New Process Makes PLA Block Copolymers

By Jan H. Schut

A new two-stage catalytic process from NatureWorks LLC, Minnetonka, MN (, the world’s largest producer of polylactic acid (PLA) biopolymer, takes an unusual mixed lactic acid feed stream, invented at Nagoya University in Japan (, and makes it into semi-crystalline PLA block copolymers. The new copolymers, which are still in R&D, could potentially offer substantially higher melt temperatures than PLA homopolymer.

All commercial PLA so far is based on bacterial fermentation to a single lactic acid isomer (L-HLA), which is condensed into L-lactide monomer, which is polymerized into PLLA homopolymer. PLLA homopolymer was introduced in the 1990s by Cargill Inc., Minnetonka, MN ( and commercialized in 2003 by NatureWorks, which is 50% owned by Cargill.

Instead of L-lactide, the feedstock for NatureWorks’ developmental PLA block copolymers is a mixture of “racemic-lactide” and “meso-lactide.” Lactides are ring compounds made by dehydration and condensation of hydroxyl and carboxyl groups from lactic acid and come in three shapes. L-lactide is a ring made of two L lactic acids; D-lactide is a ring made of two D lactic acids; and meso-lactide is a ring made of one of each. A racemic mixture means a 50/50 mixture of left- and right-handed molecules, so rac-lactide has equal amounts of L-lactide and D-lactide.

Lactic Acid

The feedstock for NatureWorks developmental process for PLA copolymer is a lactide mix invented at Nagoya University with equal amounts of LLA, DLA and meso-LA rings, made chemically from glycerin. Commercial PLAs are homopolymers made by fermentation of sugar.


The rac-lactide mixture is made by a process invented by Professor Nobuyoshi Nomura of the graduate bio-agricultural polymer chemistry department of Nagoya University and reported in a series of Japanese patents and technical papers in 2003-2011. Nagoya University’s patented process (JP Pat. Applic. # 2003-64174) uses a purely chemical reaction of glycerin, or glycol, a byproduct from bio diesel production, with sodium hydroxide, or caustic soda.

The process was interesting, but not commercially significant at the time because the racemic lactic acid mixture yielded mixed lactides that didn’t make PLA with useful properties. Conventional ring-opening catalyst polymerized mixed lactides into atactic amorphous PLA, which has no melt temperature. Rac-lactide (half LLA and half DLA) could be separated from meso-lactide because rac-lactide has a higher melt temperature, but then one-third of the feedstock would be wasted. So the cost of separation and waste would have made Nagoya University’s chemical route to PLLA copolymer too expensive vs. existing fermentation routes to PLLA homopolymer.

Test Properties of NatureWorks’ PLA Block Copolymers in R&D

Polymerization time

rac-LA/ meso-LA Ratio

Step 1 Step 2 Mol. wt. Melt temp. °C Tacticity type
Reference example 3 100/0 2 hrs 0 109,000 183 Semi- crystalline
Working example 6 90/10 1 hr 3 hrs 143,000 177 Semi- crystalline
Comparative example 7 90/10 3 hrs 0 136,000 N/A Amorphous
Source: NatureWorks/Nagoya Univ. JP Patent #50689; U.S. Pat. Applic. #20150087799)

Dozens of researchers since the mid-1990s tried to find a catalyst process to polymerize a mixture of racemic-LA and meso-LA. Nagoya University’s Nomura tested a wide range of site-selective catalysts, including chiral salen- and homosalen aluminum complexes and conventional ring-opening catalysts with chain-end polymerization trying to create isotactic PLA copolymers. But with both site selective and chain end catalysts, the meso-lactide in the mix created “errors” in the PLA chains that made the material amorphous and unusable with low isotacticity. The isotacticity level of a polymer is the average number of molecules strung together with regularly alternating “thumbs” without errors in the sequence.


NatureWorks’ invented a two-stage polymerization process that converts Nagoya University’s glycerin-based mixture of lactides (33% L-LA, 33% D-LA, and 33% meso-LA) into stereo regular, semi-crystalline PLA copolymers without separation. The patent (JP# 5806890; U.S. Pat. Applic. #20150087799) names NatureWorks, Nagoya University, and two companies, Hitachi Zosen Corp., Tokyo, Japan (, and Tohoku Electric Power Co., Sendai, Japan (, which were on the original Nagoya University patent.

In the first stage, the higher solubility of meso-LA at lower temperature allows it to melt and dissolve into a small amount of solvent and be polymerized with ring-opening catalyst into amorphous polymeso-LA blocks, while the lower solubility of rac-lactide leaves it unreacted in the solid phase. In one patent example, first stage polymerization of meso-LA is done at 90 degrees C for one hour. Since the first polymerization stage allows meso-LA to be separated from racemic-LA, NatureWorks could test several different ratios of racemic-LA to meso-LA including 80/20, 90/10, and 100% racemic-LA with no meso-LA.

JP Patent image

NatureWorks two-stage catalytic process polymerizes low temperature meso-LA into amorphous blocks. Then site-selective catalyst polymerizes long blocks of LLA and DLA onto polymeso-LA, forming semi-crystalline PLA copolymers with melt temperatures up to 220 °C.

In the second polymerization stage, rac-lactide (50% L-LA and 50% D-LA) is heated to a higher temperature, allowing it to dissolve and react in the presence of Nagoya University’s single-site salen aluminum catalyst. Second-stage polymerization is described in one patent example as taking three hours at 130 degrees C without solvent. In the second polymerization stage, rac-lactide is therefore grafted onto polymeso-lactide.

“The final architecture is a block copolymer with one block of meso-lactide followed by large blocks of L-lactide followed by large blocks of D-lactide and vice versa,” NatureWorks’ chief scientist, Joseph Schroeder explains. “The catalyst is capable of generating blocks of L and D that are long enough to form stereo complex crystals that melt at 220 °C.” NatureWorks’ patent describes PLLA and PDLA blocks of eight molecules or more. PLLA and PDLA homopolymers have lower melt temperatures of 162-180 °C.

NatureWorks’ R&D on glycerin-based PLA copolymers so far is only on a bench top scale, and no timing has been set for when it might be scaled up. In the meantime, NatureWorks more immediate R&D priority is PLA based on methane, which could come from a variety of sources. Methane, which is produced by natural decomposition of plant matter, is a component of natural gas and is also generated from landfills and waste water treatment.

PLA from methane is part of NatureWorks’ joint R&D program with Calysta Inc., Menlo Park, CA (, supported by a U.S. Department of Energy grant, for bacterial fermentation of methane to lactic acid, which would feed NatureWorks’ existing PLA homopolymer. Both glycerin and methane based research programs are environmentally interesting because they create PLA from industrial bi-products, not from sugar.

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Dandelion Rubber TPO

By Jan H. Schut

Over the last 100 years almost all natural rubber has come from tropical rubber trees (Hevea brasiliensis). The global natural rubber supply, which is critical for tire making, is periodically at risk from disease, high prices, and political instability in Africa and Southeast Asia where these trees are grown.

Governments have sponsored research on alternative natural rubber for tires off and on for over 100 years, typically in war time or when rubber prices soar. Now tire makers around the world are driving the development of alternative sources of natural rubber like dandelions and guayule shrubs, working with universities and bio-tech companies. While promising, the alternatives are a lot harder to harvest than latex, which can be tapped and collected right from the rubber tree. The alternative plants also need secondary processing, mechanical-, aqueous-, or solvent-based, to extract rubber-like polymer.

At least one auto maker also wants to modify plastics with alternative rubber, potentially for TPO bumper covers and TPE interior parts. TPOs are mostly copolymers of ethylene octene and ethylene butylene with PP and some copolymers of EPDM/PP, all of which are more stable and compatible with PP than natural rubber, compounders say. Melt blending natural rubber and PP would actually be going back to older technology, but the carbon footprint of natural rubber grown in the U.S. would be attractive.

Alternative rubber plants include Russian or “TKS” dandelions (Taraxacum kok-saghyz), actually from Uzbekistan and Kazakhstan; guayule (Parthenium argentatum) a shrub found in Mexico and the American southwest; sunflowers (Helianthus sp.); prickly lettuce (Letuca serriola); and certain fungi. TKS dandelions would be an annual crop with rubber extracted from the roots. Guayule bushes take two years to mature, but then can be harvested annually, producing rubber in the bark. Both dandelions and guayule produce very high molecular weight polymer like that from rubber trees. Sunflowers are an annual oil seed crop with very low molecular weight latex in the leaves–30,000-80,000 molecular weight vs. 1,300,000-1,500,000 for dandelion, guayule and tree rubber.

OARDC Cornish Lab

Major U.S., Japanese, and European tire makers are supporting big research efforts to develop alternative natural rubber from guayule shrubs and from TKS dandelions, like these 7-day-old seedlings growing in a research facility at Ohio State. Photo: OARDC

“If you were making rubber gloves or condoms, you would want guayule, which is stretchier [than dandelion rubber] and has no allergens. Someone who developed an allergy to Hevea latex would be allergic to dandelion latex, which is almost identical. Sunflower rubber hasn’t been tested yet for allergens,” says Katrina Cornish, research scholar at Ohio State University’s Ohio Agricultural R&D Center in Wooster ( Cornish also heads Program of Excellence for Natural Rubber Alternatives (PENRA), working on both guayule and dandelion rubber. PENRA members include Cooper Tire & Rubber Co., Findlay, OH (; Bridgestone Corp., Tokyo, Japan (; Goodyear Tire & Rubber Co., Akron, OH (; and Ford Motor Co., Dearborn, MI (

As part of a U.S. Department of Agriculture/Department of Energy grant, Cooper also works with Cornell University, Ithaca, NY (; Clemson University, Clemson, SC (; and guayule rubber supplier PanAridus LLC, Casa Grande, AZ ( Cooper unveiled a tire with multiple guayule rubber components in August 2015 and announced plans to deliver a prototype tire with 100% of natural rubber components made from guayule by 2017.

Bridgestone set up a bio-rubber process research center in Mesa, AZ, and a 281-acre guayule R&D farm in Eloy, AZ, which started up in 2013. The goal of the farm is to produce seed for high-rubber-content guayule and work with independent guayule producers. Bridgestone also has a patented process (U.S. Pat. # 8815965) for “recovering rubber from natural latex” including guayule and TKS. In October this year Bridgestone announced that it had built passenger tires in Japan and in Italy with natural rubber components made 100% from guayule rubber. Bridgestone says the earliest guayule rubber will be in commercial tires is in the 2020s.

Guayule shrubs

Alternative natural rubber from the bark of guayule shrubs is very high molecular weight like rubber from Brazilian rubber trees, but without the protein allergens. Guayule shrubs are native to arid land in Mexico and Arizona. Photo: Bridgestone

Internationally, the tire division of Continental AG in Hanover, Germany (, an automotive supplier, works with a consortium including the Fraunhofer Institute for Molecular Biology and Applied Ecology in Muenster, Germany ( and the University of Muenster’s Institute for Plant Biology and Biotechnology ( Apollo Vredestein B.V., Enschede, the Netherlands (, part of Apollo Tyres Ltd. in Gurgaon, India (, works with the European Union’s EU-PEARLS ( alternative rubber project on both guayule and dandelion rubber. Japanese tire maker Sumitomo Rubber Industries Ltd. in Kobe ( works on dandelion rubber with Kultevat Inc. in St. Louis, MO (, a startup founded in 2010. Kultevat partners with KeyGene N.V., a biotech company in Wageningen, the Netherlands (, and with the Donald Danforth Plant Center in St. Louis (


Both guayule and dandelion rubber could be used to modify PP, says Deborah Mielewski, senior technical leader of sustainable materials and plastics research at Ford, which is working with both alternative rubbers to modify soft TPEs and rigid TPOs. At the Society of Plastic Engineers 2015 TPO Conference last September in Troy, MI, Ford reported testing new generation TPOs that combine recycled PP with guayule and dandelion rubber, reinforced with graphene nanoplatelets to meet specs for things like wheel lips and bumper covers. Guayule is available in larger quantities; dandelion rubber is currently only available in tiny amounts, researchers say.

Ford Motor Co.

Ford is studying TPOs made of recycled PP with alternative natural rubber reinforced with graphene nanoplatelets. Guayule/HDPE composites are also promising for building products because of guayule’s inherent insect repellent properties. Graphic: Ford Motor Co.

A patent application (U.S. Pat. Applic. # 20150267015) from Ohio State’s Cornish on “Latex products containing fillers from waste” also reports promising blends of guayule rubber with a cross-linking agent like sulfur and unusual bio fillers like finely ground eggshells and tomato skin waste from catsup making. When the biomass/guayule blend was made into cast film (0.03 to 0.26 mm thick) and tested, it showed tensile strength over 24 MPa; elongation @ break over 750%; flexural modulus of 500%; and elongation of less than 5.5 MPa, the patent application says. Ohio State researchers also blended PLA and PHBV with up to 25% natural rubber, improving the biopolymers’ flexibility.

Guayule rubber also adds insecticidal properties. Fifteen years ago the University of Illinois and U.S. Department of Agriculture applied for a patent (WO # 2001088051) on composites of 70% guayule rubber and 30% HDPE from recycled milk bottles. They tested composites of both ground whole guayule plants and ground guayule bagasse after rubber extraction and found that both showed strong resistance to termites and decay. Only 5% of termites were alive after a week in a jar with a guayule composite sample vs. 100% alive for those in a jar with a piece of pine wood. They also reported that test composites of HDPE with three guayule species and bagasse met or exceeded American Standards for hardboard. The patent concludes that both guayule and guayule bagasse would be useful in wood-filled plastic profiles like lumber, poles, and railroad ties or in plywood and chipboard composites.

Strength of 30/70 HDPE/Guayale vs. HDPE/Wood Flour and Hardboard Standards

Fiber type Modulus of rupture
Modulus of elasticity
Internal Bond*
Parthenium incanum
(whole ground)
17.93 1149.87 1.083
Parthenium tomentosum
(whole ground)
23.04 1169.83 1.282
Parthenium argentatum
(whole ground)
16.02 982.66 1.069
Parthenium argentatum
(bagasse ground)
18.88 1180.59 1.055
Pine flour 19.76 1213.27 1.200
American Standard, 1995
for service hardboard
13.8 0.17
American Standard, 1995
for industrial hardboard
20.7 0.34

*Internal Bond or Tensile Stress Perpendicular to Plane
Source: Univ. of Illinois/USDA Paper for 33rd Annual IRG Meeting, Cardiff, Wales

PanAridus is currently the only commercial producer of guayule rubber, making “several thousand pounds annually” from a plant line that matures in 16-20 months, “and produces more rubber per acre than the tropical rubber tree,” says founder and CEO, Michael Fraley. PanAridus, founded in 2009, uses patent-applied-for technology (U.S. Pat. Applic. # 20150232583) to extract rubber from guayule plants with solvent, reportedly recovering 10% guayule rubber and another 10% lower molecular weight resin for adhesives.

A previous company, Yulex Corp. in Phoenix, AZ ( founded in 2000, used an aqueous extraction process and sold guayule rubber commercially for medical gloves and wetsuits. Yulex also supplied guayule rubber for Ford’s TPO R&D. Yulex is auctioning its equipment in December and is believed not to be operating.

Kultevat commercially produces dandelion rubber. The company was founded by its president, Daniel Swiger, who was previously a founder of Yulex. In an executive summary in September 2014, Kultevat said it expected to produce 6000 lb of TKS rubber in 2015. Kultevat has patent-applied-for water-based technology (U.S. Pat. Applic. # 2014037059) to extract rubber and sugar for ethanol from shredded dandelion roots.

A Canadian start-up Nova-BioRubber Green Technologies Inc., in Surrey/Vancouver, B.C. (, plans to produce TKS dandelion rubber using a patented dry mechanical extraction process (U.S. Pat. # 7540438), developed by Kok Technologies Inc., a related company started in 2002. Nova-BioRubber works with National Research Council Canada in Ottawa, Ont. (, and the Build-in-Canada Innovation Program ( to develop its TKS process.

Another start-up biotech company, Edison Agrosciences Inc. in Durham, NC (, plans to produce low molecular weight rubber from sunflower leaves. Edison director of research, Thomas Hohn, says they won’t use leaves from existing oil seed crops, but are developing sunflowers with increased leaf size and rubber concentration that will be grown exclusively for rubber. Ohio State’s Cornish is their chief scientific officer.

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First Foaming Head for Blow Molding

Jan H. Schut

The most interesting new technology at the Society of Plastic Engineer’s recent 31st Annual Blow Molding Conference in Pittsburgh October 12-14 (, is certainly W. Mueller GmbH’s continuous physical foaming extrusion head. Mueller ( in Troisdorf-Spich, Germany, introduced the head at NPE 2015, but the blow molding conference was the first presentation of the technology.

The three-layer, continuous foam extrusion blow molding head has been under development for a year. It uses an injection and dynamic mixing module to inject and disperse nitrogen into the plastic melt flow inside the head, where a special mixing element combines the two into a foamed middle layer. The amount of nitrogen injected into HDPE ranges from 0.05 to 0.12 L/min, reducing part weight by up to 20%, Mueller says.

Chemically foamed monolayer bottles and parts have been commercial for over 15 years, but aren’t widely used. Physically foamed bottles with gas disbursed in the extruder are also made commercially, using technology licensed from Mucell Extrusion LLC in Woburn, MA (, such as foamed preforms for reheat stretch blow molding from Plastic Technologies Inc., Holland, OH (, foamed extrusion blown automotive parts from ABC Group in Toronto (, and foamed bottles from Alpla Packaging in Austria (

Mueller’s patented technology (DE Pat. # 102013105749), however, is believed to be the first physical foaming in an extrusion blow molding head and requires no license. Customer trials are going on now in Europe. It can also be retrofitted.

Trilayer Foam Blow Molding Systems

Mueller’s three-layer extrusion blow molding head uses a dynamic mixer to add nitrogen to plastic melt, foaming the middle layer. It’s believed to be the first physical foaming done in an extrusion blow molding head.

Other blow molding conference news includes prize winning parts and containers with unusually complex shapes, made with intriguing, if not new, combinations of mold movement. A backhoe fender from Deere & Co., Moline, IL (, won overall 1st prize for industrial blow molding, made in a five-part automated mold with two side platens, a base, and two compression molding slides. Prize winning containers include two unusual dual bottles.


Deere’s backhoe fender is reportedly one of the largest parts ever made with tabs formed off the parting line, says Kenneth Carter, plastics technology leader at Deere. It was converted from rotational molding with a hefty weight saving from a 13-lb roto molded part down to a 9-lb blow molded one. The horseshoe-shaped blow molded fender is partly hollow with six tack-offs, which are stronger and much lower weight than roto molded tackoffs. The mold also has a dimpled surface texture and interchangeable bases for mud flaps, required in some markets.

First, the bottom section of the mold pinches the parison to make a pillow with low blow air of around 10 psi. Then two side platens close to shape the part with two blow needles, pushing extra plastic into a fold to create a faux parting line where structural tabs are needed. Finally, two slides compression mold and core the four tabs. The part was designed by a team at Deere; the mold was designed and built by Midwest Mold Builders Inc., Waverly, IA ( The fenders went into production in 2013, molded by Exo-S Inc. ( in Cold Water, MI.

Midwest Mold has posted a video of the mold:


Overall 1st prize for packaging went to a small wide-bodied “pod” for soap concentrate from Replenish Bottling LLC in Los Angeles, CA ( The 3-oz. pod becomes the base to a refillable soap dispenser. Squeezing the pod measures three 1-oz. squirts into the dispenser, which is then filled with water. Pods are molded in six-cavity, three-section tools from FGH Systems Inc., Denville, NJ (

Two platens close from the sides as hydraulic cylinders on the outside move the base up on two steel guide rods, while pins and rulon bushings close the base onto the side platens. FGH has built multi-cavity molds with moving bases for over 20 years, but for big 1-6 gallon bottles. The 3-oz. PP pods are by far the smallest three-section molds FGH ever built. They’re molded by Berry Plastics Corp., Evansville, IN (, on a shuttle blow molder.

An extrusion blown dual-dispensing bottle from VariBlend, Greenville, SC (, won 1st place in pharmaceutical packaging. The 30-ml bottles, which dial different combinations of two ingredients, interlock at the bottom and snap together on top. The EPET bottle halves are extrusion blown by Sonoco Products, Hartsville, SC (, in eight cavity molds also from FGH (4/4). A sliding pin forms the undercut for the interlocking bottom, then retracts into the mold.

FGH Systems Prize Winning Dual Bottles

Mueller’s three-layer extrusion blow molding head uses a dynamic mixer to add nitrogen to plastic melt, foaming the middle layer. It’s believed to be the first physical foaming done in an extrusion blow molding head.

A patented double helix promotional drink cup from Whirley DrinkWorks Industries Inc., Warren, PA (, was exhibited in the food and beverage container category. Made with a mold built in-house, the cup looks like a dual bottle, but isn’t really. The two tubes appear separate, but share one neck finish, the crossover, and the bottom. The parting line follows the two helical curves, creating two large through holes without slides in the tool. The entwined tubes appear round, but aren’t perfectly, allowing room for the platens to open without mold automation. The dual helix cups have custom promotional embossing, using proprietary Whirley technology, and are molded from a soft PS copolymer. They were commercialized late last year for slushy drinks at fairs and events. The mold has alternative sections for either snap-on or twist lids. Whirley, a promotional advertising company, is developing a 32 oz. version to be released soon.

Whirley DrinkWorks double helix cup

Whirley DrinkWorks’ double helix promotional cup is extrusion blow molded in a single cavity. The parting line follows the helical curves. The entwined tubes appear round, but aren’t perfectly, which allows room for the platens to open without mold automation.

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Advances in Air Cooling for Extruder Barrels

By Jan H. Schut

Here is a look at three unusual integrations of extruder barrel heaters with hot air removal to save substantially on energy. All were designed as retrofits, but are also used on new extruders, and two have been adapted for injection molding. WEMA GmbH, Luedenscheid, Germany (, a maker of heating elements for extruders, and Insul-Vest Inc., Tulsa, OK (, a maker of insulation blankets for extruders, separately patented ceramic heaters with very controlled hot air retention and removal.

All three heat/cool systems claim big energy savings on barrel heat ranging from 30% to 70%. WEMA’s technology uses thermally conductive ceramic over resistance heater bands covered with an enclosed cooling hood with fans and vent flaps. Insul-Vest’s technology, licensed to and built by Rex Materials Group Inc., Howell, MI (, uses thermally insulating ceramic over radiant heaters and cools by sucking air through a narrow gap between the heaters and the barrel. WEMA and Davis-Standard LLC, Pawcatuck, CT (, both have patent-applied-for shrouds that fit over each of their existing resistance heaters to control the release of hot air.



WEMA’s patented heat/cool bands (DE 19855357C2) were first introduced in the U.S. at NPE 2015 (, though they were commercialized in Europe back in 2001. They are standard on many extruder brands including Kuhne GmbH, Sankt Augustin, Germany (, Windmoeller & Hoelscher KG, Lengerich, Germany (, and Rollepaal BV, Dedemsvaart, the Netherlands ( They’re also used on twin-screw extruders and injection molding machines.

WEMA developed the technology in the late 1990s working with Robert Michels, at the time a PhD candidate at the University of Duisburg-Essen, Germany (, and now head of project management at ETA Kunststofftechnologie GmbH, Troisdorf, Germany (, which builds specialty screws, barrels, and dies. WEMA and Michels developed fins made of special aluminum oxide ceramic with high thermal conductivity of 16-28 W/mK comparable to stainless steel vs. 2-3 W/mK for standard ceramic.

The conductive ceramic is made into “stones” with concave and convex ends that can easily be adapted to different barrel diameters and zone lengths. WEMA’s KH214 bands come 48 and 63 mm wide. Ceramic fins increase cooling surface area 2.5 times vs. a smooth ceramic heater band. For applications requiring more intense cooling, KH214 heat/cool bands can be sequenced with WEMA’s KE300 aluminum cooling fins, also developed with ETA’s Michels.

KH214 heat/cool bands are also combined with WEMA’s patent-applied-for shroud (Pat. Applic. # 202009005822), introduced in 2008. The shroud controls release of hot air with its Ecowema system of vent flaps that open when fans are on and seal closed when fans are off. Each temperature zone on the extruder requires its own heat control and cooling shroud. KH214 heaters with Ecowema shrouds save up to 40% on barrel heating energy.

Figure 1

WEMA’s patented KH214 heat/cool bands for extruders alternate with intense cooling aluminum bands. They’re used with an Ecowema shroud with vent flaps to control removal of hot air for barrel cooling. They were all introduced in the U.S. at NPE 2015.



Insul-Vest’s patented ceramic heater technology (WO 2001032396) was also invented 15 years ago, then licensed to Rex, which commercialized the technology eight years ago as its TCS (thermal control solution) heaters. Rex’s TCS heaters use thermally insulating ceramic and radiant heater elements, which Rex claims heat the barrel 55% faster than conventional heater bands, which have to heat the surrounding ceramic band before heating the barrel.

Cooling is also faster because TCS heaters aren’t in direct contact with the barrel. Instead there is a 3/8 inch gap between the radiant heaters and the barrel. When cooling is needed, high speed (3000 rpm) axial fans suck hot air out of this space and pull in ambient air. The hot exhaust air can then be directed where needed to dry or preheat plastic pellets, heat the plant in winter, or keep it cool in summer by venting hot air outside. TCS heaters save up to 70% on energy for barrel heating, Rex says.

TCS heaters are distributed by Milacron ServTek in Cincinnati, OH (, and sold primarily to retrofit single screw extruders for energy saving. Each temperature zone requires its own heaters and suction fans. One or two fans are used depending on the level of cooling needed. A variation for injection molding treats the whole barrel as a single zone and is used for rapid barrel cooling before product changeovers. Insul-Vest recently applied for a patent on the next generation of its energy saving heater technology.

Figure 2

Rex Materials’ TCS heater bands, licensed from Insul-Vest, use radiant electric heaters insulated with ceramic. Heaters don’t touch the barrel. Instead there is a 3/8 inch gap between them, through which axial fans pull ambient air for rapid barrel cooling.



Davis-Standard also introduced a patent-applied-for heater/cooler system (U.S. Pat. Applic. # 20120090819) in 2011 called energy-efficient, air-cooled, electrically heated (EEACEH). The insulated cover prevents radiant heat loss and uses a conventional air cooling fan with a valve system. Valves open with air flow when the cooling fan is on and close with gravity when the air flow stops. The cover is designed to retrofit Davis-Standard extruder barrels with cast aluminum heaters built after 2000 and even reuses the bottom plate of the barrel cover.

Each temperature zone on the barrel requires a separate shroud. EEACEH shrouds have been field tested and are now commercial. Davis-Standard recently booked a large order for 27 extruders with the energy saving shrouds for barrel sizes from 1.5 to 5 inches in diameter. Shrouds are available for up to 6-inch diameter extruders. The technology is “most effective for cast film and extrusion coating where higher temperatures are used,” says Davis Standard’s Vice President of Technology John Christiano. The shrouds save 30% to 50% on energy for barrel heating compared to conventional air-cooled heaters.

Davis Standard

Davis Standard’s EEACEH cooling hoods retrofit barrels with Davis Standard cast aluminum resistance heaters for 30%-50% energy saving. The first large order for 27 extruders with the hoods was recently placed. Hoods are available for 1.5 to 6 inch diameter extruders.

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New High Biocontent Biopolymers

By Jan H. Schut

New biopolymer formulations are in the works for durables with very high biocontents of 90% to 100% for the first time, designed to compete head on with ABS for electronics, appliances, and auto parts. Several formulations use a new biopolymer that isn’t fully commercial yet, polybutylene succinate (PBS), which has properties like PP, but is biodegradable into CO2 and water. PBS itself isn’t new. Showa Denko KK in Tokyo (, launched the first commercial PBS, “Bionolle,” in 1993 as a niche polymer for biodegradable applications like fishnets and for automotive applications.

Whether petro- or bio-based, PBS is made from roughly 60% succinic acid and 40% butane diol. Showa Denko began to offer bio content PBS in 2012, with bio succinic acid from Myriant Corp., Quincy, MA (, through a semi-works plant in Lake Providence, LA, but Showa Denko’s PBS capacity is reportedly less than 12 million lb/yr and not dedicated.

In August 2015, PTTMCC Biochem Co. Ltd., in Rayong, Thailand, started up the world’s first dedicated biocontent PBS plant and is sampling customers. PTTMCC uses bio succinic acid made by BioAmber Inc.’s new monomer plant in Sarnia, Ontario, which also started in August, using patent-applied for technology (U.S. Pat. Applic. # 20140242652) from Mitsubishi Chemical Corp., Tokyo ( For now the BDO is petro-based, so the PBS won’t have more than 60% biocontent. PTTMCC’s capacity is 40 million lb/yr, still only a semi-works size, so there won’t be a lot of biocontent PBS available even in full production. PTTMCC is a joint venture between Mitsubishi Chemical, and PTT PLC Ltd. in Bangkok, Thailand. A sister company of PTT owns Myriant and also owns 50% of NatureWorks LLC, Minnetonka, MN (, maker of Ingeo PLA, the world’s largest volume biopolymer.

Bio PBS targets mulch films and packaging for biodegradability. But so far no PBS has claimed a “letter of no objection” for food contact from the U.S. Food and Drug Administration. Meantime the most interesting PBS technology to appear is high-biocontent compounds developed by automotive tier one supplier Faurecia SA, Nanterre, France ( Though Showa Denko and Mitsubishi Chemical have offered petro PBS for auto parts for years, what makes Faurecia’s PBS unusual is that it will be 100% bio.

Faurecia started an ambitious 15-year development program in 2006, more than 10 years before bio PBS was available, and planned in three material stages. The first material, a patent-applied-for composite (U.S. Patent Applic. # 20140291894), called NafiLean, took five years to commercialize, and is composed of 20% short chopped hemp fibers and 80% PP. It’s used for non-visible door panel inserts and the “top roll” on Peugeot 308 cars, starting with model year 2013, and for an entire instrument panel on the 2015 Alfa Romeo Giullia sedan.

According to the patent application, the PP/natural fiber composite uses very high flow ethylene as a flow enhancer. Chopped hemp fibers were developed in a joint venture called Automotive Performance Materials in Fontaine-les-Dijon, France (, between Faurecia and Interval Group, Arc les Gray, France (, a large agricultural cooperative. The length and aspect ratio of the fibers is similar to short glass fibers, Faurecia says. Hemp fiber adds strength and makes parts 20% to 25% lighter weight than 20% mineral filled PP. Mineral fillers are not used in NafiLean.

Short hemp fibers are loaded at 20%-40% depending on applications. Interior car parts under glass need to withstand temperatures over 120 C, Faurecia’s patent application notes. NafiLean PF2 555 with 20% hemp fiber has an HDT at 264 psi (ISO 75/A) of 72 °C and an HDT at 66 psi (ISO 75/B) of 137 °C. NafiLean also shows “40% improvement in fit and finish” vs. mineral filled PP.

Cool New Materials for Durables

Automotive tier one supplier Faurecia spent five years developing NafiLean, an 80/20 PP/chopped hemp fiber compound for lightweight structural car door parts. The next stage is 75/25 PBS and hemp fiber, called BioMat, commercial this year with 70% bio content.

Faurecia’s second stage material is hemp-filled PBS, called BioMat, which is commercial this year. Faurecia and Mitsubishi Chemical signed an R&D agreement in 2012 to optimize PBS for car parts, preventing its inherent biodegradability, increasing HDT, and reducing its high viscosity for faster molding cycles. Faurecia invented a bio-based flow enhancer and bio-based heat stabilizer for a bio-based PBS copolymer with the necessary performance. The patent-applied-for flow enhancer (U.S. Patent Applic. # 20140088269) is described as an aliphatic biopolyester based on PBS plus a terminal epoxide group. This novel oligomer not only increases flow properties of PBS, but prevents aging degradation.

Fauretia’s patent-applied-for booster (U.S. Pat. Applic. # 20140005351) for HDT involves polymerizing a bio-based high temperature polyester, polyetheramide (PEA), starting from the same monomers as PBS–succinic acid and 1,4 butenediol–plus 1,4 butenediamine. This bio-based PEA can then be reactively compounded with PBS to make a PEA/PBS copolymer with higher HDT. Faurecia developed both the flow enhancer and PEA for automotive applications working with the Institut National de la Recherche Agronomique headquartered in Paris ( and with Agro-Industry Recherche & Development in Pomacle, France ( Modifications of both technologies could potentially be developed for non-automotive applications.

Mitsubishi Chemical uses Faurecia’s technology and “specific protocol” to produce a high molecular weight “Bio PBS14” for Faurecia at PTTMCC’s new plant in Thailand. Faurecia then compounds roughly 70% bio-based BioMat including hemp fiber. BioMat passed an impressive series of auto industry tests including ultrasonic welding, noise damping, odor and VOC (it smells slightly of caramel) plus stringent German automakers’ dimensional specifications. Audi and Mercedes-Benz require dimensional stability and covering adhesion after 50 cycles from -35 °C to 80 °C with 80% relative humidity; four days (96 hours) from -30 °C to 90 °C with 95% relative humidity; and 30 days from -30 °C to 90 °C with 92% relative humidity.

In stage three, when bio-BDO monomer is commercially available, all-bio PBS will become available. Then BioMat will be 100% bio-based as well. It will culminate an extraordinary R&D effort by a processor to a new material.


NatureWorks’s Ingeo PLA, originally used mostly for packaging, has also developed two new high-biocontent injection molding grades for durables like appliances and electronics. One is medium impact, one high impact. Both use nucleating agents for rapid crystallization and higher HDT. The medium impact grade has 89% bio content with 11% modifiers and nucleating agents and HDT of 92 degrees C at 66 psi. The high impact grade has 88% bio content with 12% modifiers and nucleating agents, and HDT of 77 degrees C at 66 psi. Both are available in test quantities.

Wacker Chemie AG, Munich, Germany (, also recently published data on blends of 40% PBS from Mitsubishi Chemical and 30% PLA Ingeo 4043D from NatureWorks, using 20% of Wacker’s Vinnex PVA-based compatibilizers to enhance properties, and 10% filler, either talc or calcium carbonate for a total of 70% bio content. The Vinnex part is comprised of 14% Vinnex 2504, a vinyl acetate ethylene copolymer for higher elongation and 6% Vinnex 2510, a vinyl acetate homopolymer for higher stiffness. Developmental PBS was supplied by Mitsubishi Chemical from a pilot plant. Ingeo PLA was supplied by NatureWorks.

Wacker claims higher impact and melt strength for the PBS/PLA blend, more flexibility, and higher heat resistance for appliances–about 100 °C vs. 60 °C for typical PLA. Vinnex also allows PLA and PBS to be combined in any ratio. Without compatibilizing, only 10%-20% PBS would be miscible with PLA. Wacker introduced Vinnex five years ago in the U.S. and six years ago in Europe and offers nearly a dozen grades. Wacker also has a patent application (WO2010133560) on biopolymer blends with flour as a filler, as opposed to refined starch, noting that unrefined flour brings gluten and fibers to strengthen biopolymer blends without adding sensitivity to moisture like refined starch.

NatureWorks previously offered two PLA/PBS blends with over 50% PBS, AW300D for injection molding and AW240D for thermoforming food service, in a joint venture with Montreal-based BioAmber ( called AmberWorks. AmberWorks used technology BioAmber acquired in 2010 when it bought Sinoven Biopolymers Inc. in Philadelphia, PA, and China. But AmberWorks grades target packaging and aren’t actively sold.

Properties of High-Bio-Content Polymers for Injection Molding vs. ABS

NatureWorks Faurecia
Ingeo PLA 20% hemp/PP 25% hemp/PBS
Medium Imp. High Imp. NafiLean BioMat
Grade “884-41-1” “884-41-2” PF 2555 NBF2 112 ABS
Biocontent, % 89 88 20 60 0
Specific gravity, g/cm3 1.22 1.21 0.98 1.04
Tensile modulus, kpsi 414 414 384 384 336
Tensile strength @ yield, psi 5400 5500 5600
Tensile elong. @ break, % 32 21 5.5
Notched Izod imp., J/m
(ASTM D256 method)
139 443 277
Notched Izod imp., kJ/m2
(@23 °C, ISO 180 method)
7.5 7.2
Flexural strength, kpsi 9.5 9.4 9.9
Flexural modulus, kpsi 455 448 345
HDT, @66 psi, °C 92 77 137 104 87
MFR 190 °C/5 kg, g/10 min 11.6
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Beyond Micro: Nano Injection Molding Is Finally Commercial

By Jan H. Schut

After nearly 30 years of R&D, nano molding may be too small to see, but it’s real. Nano details that are so small they can’t even be seen under a microscope are being injection molded. They’re read by electron microscopes or by defraction using a laser pointer. Molded nano features include invisible logos on parts to prevent counterfeiting, functional surfaces like radar deflection, and hologram-like iridescence.

The original technology was developed in the 1980s by what is now the Karlsruhe Institute of Technology in Germany ( to make nozzles for uranium enrichment for atomic energy. Called LIGA, short for lithography, electroplating and molding in German, it uses concentrated X-rays to cure successive layers of PMMA to make highly precise, straight-sided parts, which are then electroplated with nickel alloys or gold.

But X-ray LIGA has drawbacks for nano molding. Vertical walls are hard to demold, so it would only work for shallow nano surfaces. The technology also requires a costly, colossal X-ray concentrating machine called a synchrotron. KIT’s is the size of a very large warehouse. An even larger one in Switzerland is the size of a small stadium. Only two companies use X-ray LIGA commercially – Microworks GmbH in Eggenstein-Leopoldshafen, Germany (, a spinoff from KIT in 2007, and HT MicroAnalytical Inc., Albuquerque, NM ( Neither has made an injection mold insert.

Nano-featured injection mold inserts are beginning to be made by UV-cured LIGA, which is less expensive than X-ray, and by nano imprint lithography. Both lithography technologies have been used for over a decade to emboss nano features on film, but only recently tried for injection molding. Mimotec SA in Sion, Switzerland (, was founded in 1998 to develop UV LIGA for micron-scale molding technology, as the name says. Instead Mimotec’s market turned out to be direct production of electroplated watch parts. Mimotec only made its first commercial nano mold insert with UV LIGA three years ago for a French office supply company. The insert, mounted on an ejector pin, puts an invisible logo on parts for authentication.

Mimotec’s patented UV-LIGA technology (EP 2855737) exposes up to three layers of polymer to make a nano feature. First a flat silicon substrate is coated with an epoxy-based photo-sensitive polymer called “SU8.” Then the reverse of the part is exposed to UV laser light using a mask. After UV exposure it takes a week for each layer to harden unless a curing agent is used. Once the layers harden, uncured polymer is washed away, and the cavity is sent out for electroplating with nickel, nickel phosphorous or gold. Electroplating is up to 0.8 mm thick, much thicker than conventional electroplating, which is only microns thick.

Mimotec’s sister company, Sigatec SA in the same location (, engraves directly on an oxidized surface layer of silicon to make functional nano-features. Sigatec’s Deep Reactive Ion Etching was used to emboss film, for example for a medical part for DNA analysis with 42 million truncated cones on the surface, each 3 microns in diameter by 3.5 microns high.

The ant on the November 1992 cover of Scientific American holds a micro gear made by then revolutionary X-ray LIGA lithography and electroplating. Today faster, less expensive UV LIGA makes shims for injection molds for micro gears and nano-scale molded features. Photo: Mimotec.

The ant on the November 1992 cover of Scientific American holds a micro gear made by then revolutionary X-ray LIGA lithography and electroplating. Today faster, less expensive UV LIGA makes shims for injection molds for micro gears and nano-scale molded features. Photo: Mimotec.

Tecan Precision Ltd. in Weymouth, Dorset, U.K. (, founded in the 1970s, is also an early user of UV LIGA, making metal masks for vacuum deposition for electronics with micro features. Tecan has also taken customers’ nano-structured masters and replicated them to make injection mold shims 200-300 microns thick, electroplated with sulphamate nickel.


Two other companies offer equipment for mask-less UV LIGA for nano mold inserts, which is reportedly less expensive and faster than using a mask. LPKF Laser & Elektronics AG, Garbsen, Germany (, a maker of laser equipment for printed circuits, offers Laser Direct Imaging technology, which guides a UV laser with what LPKF calls a “2D acoustic/optic deflector.” LPKF’s ProtoLaser LDI exposes photo resists by positioning the laser spot with “better than 1 nanometer precision,” using a UV laser wave length of 375 nanometers at a maximum speed of 100,000 spots per second. It targets molding microfluidic parts like lab-on-a-chip medical devices for blood testing and can even create rounded nano structures.

UV LIGA technology exposes a photo resist layer using a mask to define a part or its reverse. LPKF Laser & Elektronics builds mask-less UV LIGA equipment that can create rounded micro and nano details like the channels on this template for a lab-on-a-chip medical device.

UV LIGA technology exposes a photo resist layer using a mask to define a part or its reverse. LPKF Laser & Elektronics builds mask-less UV LIGA equipment that can create rounded micro and nano details like the channels on this template for a lab-on-a-chip medical device.

Nanoscribe GmbH in Eggenstein-Leopoldshaven, Germany (, another spinoff from KIT founded in 2007, makes a commercial mask-less 3D printer for nano parts, called the “Photonic Professional GT.” Nanoscribe’s patented light absorption reaction (U.S. Pat. Applic. # 20120218535) uses electromagnetic radiation to trigger a local photo reaction in the coating with either positive or negative-tone photo resist. Nanoscribe also has a patented LIGA process (U.S. Pat. # 8986563) that uses AZ MiR 701 polymer from Merck Performance Materials GmbH, Darmstadt, Germany (, for positive photo resist and SU8 epoxy for negative resist. Parts can then be electroplated.

Temicon GmbH in Dortmund, Germany (, founded in 2005, uses Laser Interference Lithography and UV LIGA to make shims for micro embossing down to 0.2-micron details like a “moth eye” anti-reflective film for laminated display screens. Temicon is developing customized injection mold inserts for lab-on-a-chip parts, which Temicon can injection mold in-house. Temicon merged in 2014 with Holotools GmbH in Freiburg im Breisgau, Germany (, a spinoff in 2001 from the Fraunhofer Institute for Solar Energy Systems in Freiburg ( Holotools specializes in large area nano-structures without seam lines for embossing down to 200 nanometers.


At least five companies also use processes loosely called “nano imprint lithography” or NIL, including two with technology for steel molds, not electroplated shims. (An electroplated nickel shim is typically good for only a few 100,000 injection shots, but the original LIGA part can be used multiple times to make new molds.) NIL Technology ApS (, a spinoff from the Danish Technical University in Lyngby, Denmark in 2009, uses patent-applied-for technology (U.S. Pat. Applic. # 20120244246) to put nano patterns onto a non-planar existing mold. NIL Technology first etches a nano pattern down to 80 nanometers onto a silicon wafer, then uses the wafer to emboss the pattern on film. Nano-featured film is then applied to a coated mold and electroplated. NIL Technology’s first commercial nano patterned injection mold was sold in 2014 to mold a package with a hologram.

NIL Technology’s nano imprint lithography technology applies nano patterns directly to an existing non-planar injection mold before molding. The company’s first commercial nano-structured mold was sold in 2014 to mold a hologram-like pattern onto a package.

NIL Technology’s nano imprint lithography technology applies nano patterns directly to an existing non-planar injection mold before molding. The company’s first commercial nano-structured mold was sold in 2014 to mold a hologram-like pattern onto a package.

NANO 4 U Group in Karlsruhe, Germany, and Sarnen, Switzerland (, founded in 2008, also directly builds nano structured steel molds, not nickel shims. Its steel molds can form more than a million parts “without severe quality reduction of the nano-structured end products,” NANO 4 U says. Patent-pending technology applies a surface onto an existing steel mold, and then etches into the surface to create nano features. The company’s first commercial application of the technology in an injection mold was in 2009. Main applications are hologram-like logos for branding and authentication in food, pharmaceuticals and medical devices.

NANO 4 U has patent-pending technology to etch nano structures like this holographic logo onto a coated steel injection mold, allowing over a million parts to be molded. Electroplated plastic shims with nano details can mold only a few 100,000 parts.

NANO 4 U has patent-pending technology to etch nano structures like this holographic logo onto a coated steel injection mold, allowing over a million parts to be molded. Electroplated plastic shims with nano details can mold only a few 100,000 parts.

Molecular Imprints Inc., Austin, TX (, founded in 2001 by two professors from the University of Texas, developed patented “Jet and Flash” imprint lithography that ink jets a low viscosity resist onto a silicon substrate. In 2014 Molecular Imprints sold the technology to Canon Inc., Tokyo, Japan, for use in equipment for the semi-conductor industry. Molecular Imprints is now developing other uses for the technology including nano imprint stamps on silicon, targeting lab-on-a-chip and other medical parts.

The EV Group, St. Florian am Inn, Austria (, founded in 1980 to build production equipment for semi-conductors, also builds commercial UV nano imprint lithography printers to make nano detailed parts, which can be electroplated into shims. EVG works with CEA Tech-Leti, a nano technology research institute in Grenoble, France (

LEAP Co. Ltd., Kanagawa, Japan (, founded in 2000, worked with Waseda University in Japan to develop patent pending “self-assembled monolayer” surface technology, or SAM, which covers surfaces with nano holes or pillars with high aspect ratio.

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First Coex Microcapillary Film Technology

By Jan H. Schut

The world’s first coextruded microcapillary film was reported by Dow Chemical Co., Midland, MI ( at the Society of Plastics Engineers’ recent ANTEC conference in Orlando, FL ( in March. The films are made by coextruding microscopic parallel threads in the machine direction in a film matrix.

Dow associate research scientist Wenyi Huang presented the “Effect of Rheology on the Morphology of Coextruded Microcapillary Films,” showing how different viscosities and different processing conditions affect microcapillary structure and describing some of the unique films that can be made.

Huang’s paper doesn’t say what the benefits of microcapillary film might be, but two recent Dow patent applications give clues. Depending on processing parameters and what resin or other material is pumped into the microcapillaries, they could be used to heat, cool, insulate, or even strengthen film.

The idea first surfaced in a 2005 PhD dissertation by Bart Hallmark at the University of Cambridge in the U.K. (, who put hollow microcapillary channels in the machine direction in monolayer extrudate. Dow licensed the microcapillary concept from Cambridge, but upped the ante by creating its own patent-applied-for film die and coextruding a second polymer into the microchannels.

The Cambridge and Dow dies are conceptually similar—both use hollow tubes to create microchannels. The Cambridge Hallmark patent (U.S. Pat. # 8641946) describes a die that forces monolayer polymer around needles, which inject air to make film or profile with hollow channels in the machine direction. Potential applications, described in subsequent Cambridge patent applications, include food products, tear guides in packaging, and medical devices.

Dow, which is the primary plastics licensee, has industrially scaled the die and added a second polymer, coextruded through hollow conduits, which open into the die land for the matrix polymer. A Dow patent application (U.S. Pat. Applic. # 20140113112) says the microcapillaries are at least five microns thick with at least five microns between them.

Dow’s patent-applied-for microcapillary die coextrudes microscopic fibers in the machine direction into plastic film through small round microcapillary pins in the die opening.

Dow’s patent-applied-for microcapillary die coextrudes microscopic fibers in the machine direction into plastic film through small round microcapillary pins in the die opening.

Dow made microcapillary test films with a 38-mm single-screw extruder with a gear pump for the matrix and a 19-mm single-screw extruder for the microcapillaries, testing different combinations of five commercial Dow polyolefins with different viscosities. Huang’s paper gives relative viscosities and processing temperatures of the five polymers. Polymers 1, 2, and 3 process at 200 degrees C; Polymers 4 and 5 process at 130 degrees C. Polymer 1 is higher viscosity than Polymer 2; Polymer 3 is higher viscosity than Polymer 1; and Polymer 4 is 100 times higher viscosity than Polymer 5, which is very, very low molecular weight – nearly Newtonian.

First, Dow tested film made with Polymer 1 in both the capillaries and matrix, coloring the capillary resin black and leaving the matrix natural, so the capillaries are visible. Dow tested different microcapillary extruder speeds. Not surprisingly, increasing microcapillary extruder speed increased the size of the microcapillaries. With the matrix extruder at 15 RPM and the capillary extruder at 25 RPM, capillaries account for 11.1% of the film. At 50 RPM, capillary percentage goes up to 23.1%. Increasing winding speed makes the film thinner and flattens the microcapillaries.

When Dow tested microcapillary films made with the same polyolefin in the capillaries and matrix at line speeds of 3, 6, 12, and 18 meters/min, capillaries were round at 3 meters/min and almost flat at 18 meters/min. But the film surface was smooth regardless of capillary shape.

When Dow tested microcapillary films made with the same polyolefin in the capillaries and matrix at line speeds of 3, 6, 12, and 18 meters/min, capillaries were round at 3 meters/min and almost flat at 18 meters/min. But the film surface was smooth regardless of capillary shape.

Dow then tested Polymer 1 in the matrix and lower viscosity Polymer 2 in the capillaries and with the matrix extruder at 15 RPM ran the capillary extruder at 25 RPM and 50 RPM. Microcapillary content went from 11.0% at 25 RPM up to 19.4% at 50 RPM. With the microcapillary screw at 50 RPM, winding speed was increased from 3 meters/min to 18 meters/min, which flattened the microcapillaries in much the same way as when capillaries and matrix were the same polymer.

Next Dow tested film made with Polymer 1 matrix and higher viscosity Polymer 3 in the microcapillaries and found that microcapillary content dropped to only 2.3% with the capillary screw at 25 RPM and to 18.6% at 50 RPM. Increasing winding speed didn’t flatten higher viscosity capillaries the way it did lower viscosity ones in a higher viscosity matrix or capillaries of the same polymer as the matrix.

The three different polymer combinations also produced films with different surfaces. With Polymer 1 in both matrix and capillaries at winding speed of 18 meters/min, the film surface is smooth. With different viscosity polymers, the film surface is wavy. When capillaries are lower viscosity than the matrix, the film is thinner over capillaries and thicker between them. When capillaries are higher viscosity than the matrix, the film is thicker over capillaries and thinner between them. Waviness is only visible under a microscope, but the wavy surface feels different to the touch, Huang says.


The most unusual finding is that extremely low viscosity capillaries in an extremely high viscosity matrix produce square or rectangular microcapillaries. Dow tested this extreme viscosity mismatch using watery Polymer 5 in the capillaries and Polymer 4 with 100 times higher viscosity in the matrix. The extreme viscosity pair was tested at four capillary screw speeds – 10, 20, 30 and 40 RPM – with the matrix extruder going very slowly at only 5 RPM.

The microcapillaries were rectangular with the capillary screw at 20 RPM and square with the capillary screw at 40 RPM. As capillary screw speed increased, capillaries also took up a much larger percentage of the film. With the capillary screw at 20 RPM, capillaries are 20% of the film. At 40 RPM they’re 42% – almost half!

Dow then wound films with rectangular and square microcapillaries at line speeds of 1.5 and 3 meters/min and found surprisingly that the rectangular and square microcapillaries only flatten slightly at higher winding speeds. Despite being much lower viscosity than the matrix, they retain squarish shapes.

When watery microcapillary resin is paired with 100 times higher viscosity matrix at a capillary screw speed of 20 RPM (a, c) capillaries are rectangular. At 40 RPM (b, d) capillaries are square. When winding goes from 1.5 m/min (a, b) to 3 m/min (c, d), capillaries only flatten slightly.

When watery microcapillary resin is paired with 100 times higher viscosity matrix at a capillary screw speed of 20 RPM (a, c) capillaries are rectangular. At 40 RPM (b, d) capillaries are square. When winding goes from 1.5 m/min (a, b) to 3 m/min (c, d), capillaries only flatten slightly.

What might Dow do with these unusual films? Two recent Dow patent applications give an idea of potential applications, depending on the size and shape of microcapillaries. Patent application (WO2013009538) for “Microcapillary films containing phase change materials” describes filling microcapillaries with “phase change” materials including carnowax in an LDPE matrix. The list of possible phase change materials in the patent application is long, but the patent suggests that they’re used to add or remove heat to or from the matrix polymer. A second patent application describes “Reinforced microcapillary films and foams” (U.S. Pat. Applic. # 20140072776) and suggests that microcapillary coextrusion could create reinforcing fibers in a film or foam in the machine direction, much like pultrusion.

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