Newsflash

The drive for lightweight materials to reduce overall cost and environmental impact for automotive manufacturers is nothing new.  Fuel economy attracts car buyers too. That is how majority of steel parts have been replaced in F-150 pickup truck by aluminum parts, reducing overall weight over 500 pounds. Then there are alloys, carbon fiber and plastics composites.The ambition for lighter vehicles did not stop with alloys (magnesium, aluminum), and/or composites (glass, carbon fibers).  Recently, Japanese researchers at Kyoto University led by Professor Hiroaki Yano along with its industrial partners (Denso Corporation and Daikyo-Nishikawa Corporation) reported that they were developing cellulose nanofiber based materials for automotive as well as aircraft parts to reduce environmental footprint while increasing product performance.Inevitable questions are: 1) would these materials be cost effective? 2) What would be the service life of these products compared to the current ones? 3) How about the parts’ safety in situations like crash or fire?A final question that an automaker has to ask is: what would be the pay back time to replace current production line (machinery) to CNF based plastics line?Reference: https://www.japantimes.co.jp/news/2017/08/15/business/researchers-japan-use-wood-make-cellulose-nanofiber-auto-parts-stronger-lighter-metal/#.WbAIKeTXuUm...
We know polycarbonates mostly from its use in plastics water bottles, safety goggles, smart phones, structural panels (glazing) and the list goes on.  A quick look at Wikipedia gives a spectrum of applications.However, polycarbonates have its weaknesses along with the BPA (bis-phenol) controversy. Polymers such as polysulfates and polysulfonates have similar if not better mechanical properties than polycarbonates.  The issue has been how reliably scale-up the manufacturing process of polysulfates and polysulfonates?“Click chemistry” is a concept in organic chemistry by which highly reactive reactions provide high yielding products and require little to no purification.  The concept was introduced by Nobel Prize winner Professor K. Barry Sharpless in 2001.A recent work published in Nature Chemistry, by a team of researchers from The Scripps Research Institute (La Jolla), Lawrence Berkley National Laboratory (Berkley), California and Shanghai Institute of Organic Chemistry & Soochow University, China claimed that reduced cost of catalyst, product purity, and by-product recycling make their work ready to move from laboratory research to industrial process.Chemists are at work indeed!References:https://en.wikipedia.org/wiki/PolycarbonateK. Barry Sharpless et al; Nature Chemistry, 2017 DOI: 10.1038/nchem.2796...
In a recent The Atlantic interview Bill Gates made a wish on an energy miracle, “Here’s a source of energy that is cheaper than your coal plants, and by the way, from a global-pollution and local-pollution point of view, it’s also better”.  The race is on to find that source. One such energy source is solar energy. We all know that solar energy can be harnessed to generate thermal energy or electrical energy for use in the residential and/or in the commercial applications.  Any material that can store Solar Thermal Energy is called Solar Thermal Fuel (STF).  The quest to harvest solar energy, store the same and use it when needed has been the focus of research in industry and academia alike. For the first time, Professor Grossman’s team at MIT, Cambridge (USA) has come up with a new approach which uses polymer Solar Thermal Fuel (STF) storage platform utilizing STF in its solid-state.  According to the published article, researchers stated, “Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. This approach enables uniform films capable of appreciable heat storage of up to 30 Wh kg?1 and that can withstand temperature of up to 180 °C.”How the STF process works?Certain molecules (chemicals) can have 2 different stable structural forms. These structures are called conformations.  When original molecular conformation is exposed to sunlight, the molecule gets charged and the original conformation changes to the other and stay in that charged conformation for a long period.  The charged molecule snaps back to their original shape (conformation), when triggered by a very specific temperature or other stimulus generating heat in the process. Currently, developed polymeric film can release heat about 10 degree C above the surrounding temperature. Film property improvements are underway. German auto company BMW, has sponsored this research. Where the potential application lies - your guess is as good as mine.References:The Atlantic, p 56, November 2015Zhitomirsky, D., Cho, E. and Grossman, J. C. (2015), Solid-State Solar Thermal Fuels for Heat Release Applications. Adv. Energy Mater., 1502006. doi:10.1002/aenm.201502006...
In a recent The Atlantic interview Bill Gates made a wish on an energy miracle, “Here’s a source of energy that is cheaper than your coal plants, and by the way, from a global-pollution and local-pollution point of view, it’s also better”.  The race is on to find that source. One such energy source is solar energy. We all know that solar energy can be harnessed to generate thermal energy or electrical energy for use in the residential and/or in the commercial applications.  Any material that can store Solar Thermal Energy is called Solar Thermal Fuel (STF).  The quest to harvest solar energy, store the same and use it when needed has been the focus of research in industry and academia alike. For the first time, Professor Grossman’s team at MIT, Cambridge (USA) has come up with a new approach which uses polymer Solar Thermal Fuel (STF) storage platform utilizing STF in its solid-state.  According to the published article, researchers stated, “Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. This approach enables uniform films capable of appreciable heat storage of up to 30 Wh kg?1 and that can withstand temperature of up to 180 °C.”How the STF process works?Certain molecules (chemicals) can have 2 different stable structural forms. These structures are called conformations.  When original molecular conformation is exposed to sunlight, the molecule gets charged and the original conformation changes to the other and stay in that charged conformation for a long period.  The charged molecule snaps back to their original shape (conformation), when triggered by a very specific temperature or other stimulus generating heat in the process. Currently, developed polymeric film can release heat about 10 degree C above the surrounding temperature. Film property improvements are underway. German auto company BMW, has sponsored this research. Where the potential application lies - your guess is as good as mine.References:The Atlantic, p 56, November 2015Zhitomirsky, D., Cho, E. and Grossman, J. C. (2015), Solid-State Solar Thermal Fuels for Heat Release Applications. Adv. Energy Mater., 1502006. doi:10.1002/aenm.201502006...
Reliable and high performance lithium ion batteries commonly known as LIBS are highly sought after product by industries. We all have heard stories about laptops, electric vehicles, airplanes catching fires due to LIBS. Underlying problem is the battery overheating. Preventing batteries from overheating is crucial to the public safety.  Now a team of researchers at Stanford University designed a thermo-responsive (heat sensitive) plastic composite film made from polyethylene and spiky nickel microparticles coated with graphene which shuts down the battery if the temperature is too high.         In a recently published work led by Yi Cui and Zhenan Bao of Stanford University, USA concluded “Safe batteries with this thermoresponsive polymer switching (TRPS) materials show excellent battery performance at normal temperature and shut down rapidly under abnormal conditions, such as overheating and shorting.” How practical this design approach is? Time will tell.References: Y. Cui, Z. Bao et al Nature Energy vol.1, Article number: 15009 (2016); DOI: 10.1038/nenergy.2015.9Chemical & Engineering News, Page 7, January 18, 2016...
In aviation industry, the focus is how to improve fuel safety and handling. Mike Jaffe and Sahitya Allam gave their perspective on safer fuels by integrating polymer theory into design (Science, 350, No. 6256, p. 32, 2015).Mist (generated from the fuel) is much more flammable than the liquid and that is why anti-misting kerosene interferes with mist formation when a low percentage of a polymer is added into it.  The problem however, is that the polymer chain undergoes scission during handling and can’t assist in suppressing mist formation. The answer comes from a recent paper published in the Journal Science by Professor Julia Kornfield and her cross-functional team at Caltech, Pasadena, USA. The group designed a megasupramolecules having polycyclooctadiene backbones and acid or amine end groups (telechelic polymer) which is short enough to resist hydrodynamic chain scission while protecting covalent bonds through reversible linkages. Yes, polymers can be designed to suit our societal needs including aviation fuel safety.Reference: M-H Wei, B. Li, R.L. Ameri David, S.C. Jones, V. Sarohia, J.A. Schmitigal and J.A. Kornfield; Science, 350, (6256), pp. 72-75 (2015)...
At the TED conference, Carbon3D, a Vancouver based company touted a radical 3D printing technology and named it CLIP or Continuous Liquid Interface Product. CLIP grows parts instead of printing them layer by layer. It harnesses light and oxygen to continuously grow objects from a pool of resin.  The result: make commercial quality parts at game-changing speed.  CLIP is 25 to 100 times faster than traditional 3D printing technique.  To make the point, Carbon3D web site provides a head-to-head comparison of CLIP to Polyjet, SLS and SLA.[Press release: March 16, 2015, Vancouver, Canada.  www.carbon3D.com]...
Self-healing plastics has been around for a while. Applications include self-healing medical implants, self-repairing materials for use in airplanes and spacecrafts. Even scientists have made polymeric materials that can repair itself multiple times. A recent report in Science describes a significant advance in self-healing plastics. The authors describe a product that mimics how blood can clot to heal a wound. When the plastic is damaged a pair of pre-polymers in channels combines and rapidly forms a gel, which then hardens over 3 hours.The authors demonstrated that holes up to 8 millimeters wide can be repaired. The repaired parts can absorb 62% of the total energy absorbed by undamaged parts.  Science never stops.Reference:S. R. White, J. S. Moore, N. R. Sottos, B. P. Krull, W. A. Santa Cruz, R. C. R. Gergely; Science, Restoration of Large Damage Volumes in Polymers, Vol. 344 no. 6184 pp. 620-623; (9 May 2014). ...
Knowingly or unknowingly, flexible electronics has become a part of our daily life.  Transparent conductive films (TCFs) are used in mobile phones, tablets, laptops and displays.  Currently, Indium Tin Oxide or commonly known as ITO is the material of choice.  But use of ITO has some major disadvantages and these are brittleness, higher conductivity at greater transparency, and supply of Indium.  This is where non-ITO materials come into play. Based in St. Paul, Minnesota (USA), Cima NaoTech’s uses its SANTETM nanoparticle technology, a silver nanoparticle conductive coating which self-assembles into a random mesh like network when coated onto a flexible substrate such as PET and PC.  According to a recent press release, the company stated SANTETM nanoparticle technology enabled transparent conductors in a multitude markets from large format multi-touch displays to capacitive sensors, transparent and mouldable EMI shielding, transparent heaters, antennas, OLED lighting, electrochromic and other flexible applications.  Cima NanoTech is working with Silicon Integrated Systems Corp. (SIS) of Taiwan and using its highly conductive SANTE FS200TM touch films to develop large format touch screens.References: Press release, San Diego, June 03, 2014; www.cimananotech.com ; http://www.cimananotech.com/sante-technology ; http://www.sis.com/...
In an article appeared today (January 29, 2014) in The Guardian newspaper, Stuart Dredge wrote, “From jet parts to unborn babies, icebergs to crime scenes, dolls to houses: how new technology is shaking up making things”1. Mr. Dredge was speaking about 3D printing technology.  The heart of this technology is the 3D printer itself. Stratasys, a company headquartered in Minneapolis, USA is the manufacturer of 3D printers.  It recently announced the launch of Color Multi-material 3D Printer, the first and only 3D printer to combine colors with multi-material 3D printing.  According to the press release2, by using cyan, magenta, and yellow, multi-material objects can be printed in hundreds of colors.  The technology is based on proven Connex technology.  While the base materials are plastics and elastomers, they can be combined and treated to make finished products of wide ranging flexibility and rigidity, transparency and opacity.  Designers, engineers and manufacturers can create models, mold, and parts that match the characteristics of the finished production part. This includes achieving excellent mechanical properties.  According to the manufacturer, print job in the newly revealed printer can run with about 30 kg of resin per cycle and prints as fine as 16 micron layers for models.  No wonder why some call the new Color Multi-material 3D printer a groundbreaking stuff.References: 1. www.theguardian.com.technology/2014/jan/29/3d-printing-limbs-cars-selfies (January 29, 2014)2. http://investors.stratasys.com/releasedetail.cfm?ReleaseID=821134 (August 3, 2014)...
Instead of stitches or skin staples, doctors use skin glue to close wounds. The glue joinsthe edges of a wound together while the wounds heal underneath. Most of the timeskin glue is used for simple cuts or wounds. According to the paper published inScience Translational Medicine, there are no clinically approved surgical glues thatare non-toxic, bind strongly to tissue, and work well in wet and highly dynamicenvironments within the body. This is the reason why this published work is promisingwhere infants born with heart defects would benefit tremendously. Researchers at the Brigham and Women’s hospital in Boston have engineered ‘bio-inspired’ gluethat can bind strongly to tissues on demand, and work well in the presence ofactively contracting tissues and blood flow. The authors of the paper show howthe glue can effectively be used to repair defects of the heart and blood vessels during minimally invasive procedures. [References: P. J. del Nido et al; Sci. Transl. Med., DOI: 10.1126/scitranslmed.3006557; See also, www.geckobiomedical.com/news/gecko-biomedicals-co-founde.html]...
Stability of organic electronics in water is a major research challenge. For this reason,organic electronics has yet to see any sensing application in aqueous environment.However, as understanding of underlying mechanism of stability aspect is becomingclearer, new developmental efforts to make water compatible organic polymer devicesare taking place. Recently, Professor Zhenan Bao’s group in the department of chemical engineering at Stanforduniversity revealed in a paper published in the journal of Nature Communications thatsolution- processable organic polymer could be stable under both in freshwater andin seawater. Developed organic field-effect transistor sensor is able to detect mercury ionsin the marine environment (high salt environment). Researchers believe that the work hasthe potential to develop inexpensive, ink-jet printed, and large-scale environmental monitoring devices. [References: O. Knopfmacher, M.L. Hammock, A.L. Appleton, G. Schwartz, J. Mei, T. Lei, J. Pei,and Z. Bao; Nature Communications, 5, 2954, January 6, 2014; DOI: 10.1038/ncomms3954]...
Insulin, the wonder medicine for diabetes was discovered about a century ago.Since insulin does not get into the blood stream easily, diabetes patients oftenhave injected themselves with insulin. Now a group of scientists led by Dr. Sanyog Jainat the Center for Pharmaceutical Nanotechnology of National Institute of Pharmaceutical Education and Research in Punjab, India has designed a polymerbased package for oral insulin administration. The package design addresses two major obstacles, 1) digestive enzymes must notdegrade insulin prior to its action and 2) the insulin gets into the blood stream.The package contained folic acid functionalized insulin loaded in liposomes.To protect the liposomes (lipids or fat molecules) they were alternately coated withnegatively charged polyacrylic acid (PAA), and positively charged poly allylamine hydrochloride. Studies were conducted to compare the efficacy of bothdelivery systems: designed polyelectrolyte based insulin and standard insulinsolution. Effects of oral administration lasted longer than that of injectedinsulin, authors reported in a recent article in Biomacromolecules. [Reference: A.K. Agarwal, H. Harde, K. Thanki, and S. Jain; Biomacrmolecules, Nov. 27, 2013;DOI: 10.1021/bm401580k]...
Research in the area of stretchable electronics is heating up!  Thanks to polymers. Led by Professor George M. Whitesides of Harvard University (USA), a team of researchers have demonstrated in a recently published paper in Science that ionic conductors can be used in devices requiring voltages and frequencies much higher than commonly associated with devices using ionic conductors.  The team showed for the first time that electrical charges carried by ions and not electrons, can be utilized in fast-moving, high voltage devices.As a proof of concept, the authors of the study built a transparent loudspeaker that produces sound across the full audible range i.e., 20 Hz to 20 kHz.  Components [such as VHB 4910 tape (acrylic tape with PE liner), polyacrylamide hydrogel containing NaCl electrolyte] used for the high speed, transparent actuators are described in the paper.Tissues and cells are soft and require stretchable conductors for biological systems. Many hydrogels are biocompatible which makes this work particularly an important one. The design of gel-based ionic conductors is highly stretchable, completely transparent and offer new opportunities for designers of soft machines.   [Reference: C.Keplinger, J-Y. Sun, C.C. Foo, P. Rothemund, G.M. Whitesides, and Z. Suo; Science, 341 (6149), pp. 984-987 (2013); DOI: 10.1126/science.1240228]...
Interweaving biological tissue with functional electronics, one can make bionic ears.  NASA has tested 3D-printed rocket engine part.  Then why not 3D print yourself?Well, Twinkind, a German start-up company is now offering enthusiasts statues of themselves for display.  How this works?  A full body scanner takes an image of the customer’s body, transfers the file to the printer after which 3D printer laser sinters a composite powder layer by layer into the customer image.Can we dare to say that Madame Tussauds wax figure of Voltaire can now be 3D printed in polymers soon!  [Reference: www.twinkind.com ]...
Polymer membranes have become a leading contender in numerous separation processes.  Be it in gas (air, hydrogen etc.) or be it in water purifications (salinated water, waste water etc.).  Not only polymer membrane technology helps reducing the environmental impact but also it is cost-effective.  Fracking in shell gas is one of many examples. New advances in drilling technology (such as horizontal drilling) have led to new hydraulic fractures called fracking.  Hydraulic fracturing requires about 2.5 to 5 million gallons of water per well.  Water management and its disposal are major costs for producers.One major challenge, however, of the membrane technology is the fouling (damage caused by contaminants) mitigation.  This has been recently studied by a group of researchers from University of Texas at Austin led by Professor Benny Freeman to address efficiency and reuse of water for fracking in shale gas plays.Researchers modified polydopamine coated UF (ultrafiltration) module by grafting polyethylene glycol brushes onto it.  The result is more hydrophilic surfaces which in turn improved cleaning efficiency relative to unmodified modules. The coating improves the membrane life, and can easily be applied to membrane surface by rinsing it through the recycling system.[References: D.J. Miller, X. Huang, H. Li, S. Kasemset, A. Lee, D. Agnihotri, T. Hayes, D.R. Paul, and B. Freeman; J. Membrane Sci., 437, pp. 265-275 (2013); Also see www.advancedhydro.net ]...
Flexible electronics can change the way we use electronic devices.  It is a term used for assembling electronic circuits by mounting electronic devices on a flexible plastic. A recent review article captured the advancement of CNT and graphene based flexible thin film transistors from material preparation, device fabrication to transistor performance control compared to traditional rigid silicon1. Silicon is used almost exclusively in electronic devices.Now Prof. Ali Javey led a team at the University of California, Berkley to develop a printing process to make nanotube transistors at room temperature with gravure printer.  The plastics used is polyethylene terephthalate (PET). The device exhibited excellent performance with mobility and on/off current ratio of up to ~9 cm2/ (V s) and 105 respectively.  Also, maximum bendability is observed.  The paper authors conclude that this high-throughput printing process serves as enabling nanomanufacturing scheme for range of large-area electronic applications based on nanotube networks2. References:1. D-M. Sun, C. Liu, W-C. Ren and H-M Cheng; Small, DOI: 10.1002/smll.2012031542. P.H. Lau, K. Takei, C. Wang, Y. Zu, J. Kim, Z. Yu, T. Takahashi, G. Cho, and Ali Javey; Nano Letters, 13 (8), pp. 3864-3869 (2013); DOI. 10.1021/nl401934a...
Drinking coffee from paper cups are as common as drinking water from plastics bottle. The issue however, is recycling of disposable cups. The disposable cups are made up of 90-95% of high strength paper (fibers) with a 5% thin coating of plastic (PE).To address the recycling issue, James Cropper Speciality Papers of UK have developed a process which involves softening the cup waste, and separating the plastic coating from the fiber.  After skimming off the plastic, remains are pulverised and recycled, leaving water and pulp behind.  According to the company news release, the high grade pulp is reused in luxury papers and packaging materials.An innovative approach to address a common problem.[Reference: www.jamescropper.com/news ]...
A search for an alternative to rigid silicon wafers gave birth to the area of flexible or bendable electronics. Research has been intense for the past few years in the area flexible electronics as it opens up multitude of new applications. Polymers play an important role to exciting field of flexible electronics.In a recent research report, a team of scientist led by Prof. Ali Javey of University of California, Berkeley (USA)  has shown for the first time user-interactive electronic skin or e-skin can conformally wrap irregular surfaces and spatially map and quantify various stimuli through a built-in active matrix OLED display.  Three electronic components namely thin film transistor (uniform carbon nanotube based), pressure sensor, and OLED arrays (red, green, and blue) are integrated over a plastic substrate.  Spin coated and cured polyimide on a silicon wafer is used as the flexible substrate.  Details are in the paper.This work essentially provides a technology platform where integration of several components (organic and inorganic) can be done at a system level on plastic substrates. According to the paper, this e-skin technology could find applications in interactive input/control devices, smart wallpapers, robotics, and medical/health monitoring devices.    [Ref: C. Wang, D. Hwang, Z. Yu, K. Takei, J. Park, T. Chen, B. Ma, and Ali Javey; Nature Materials, Published online July 21, 2013; DOI: 10.1038/NMAT3711]...
Recent buzz in the technology world is 3D printing.  Researchers to designers are creating new products everyday using 3D printing technology.  Even eBay has unveiled its services to those looking to make their own creations using 3D printing App.Since ages composites have played a crucial role in our society. Inspired by natural (biological) composites such as bone or nacreous abalone shell, researchers from MIT (USA) and Stratasys have developed composite materials that have fracture behaviour similar to bones.  Using computer model with soft and stiff polymers, the team has come up with a specific topological arrangements (hierarchical structures) of polymer phases to boost the mechanical behaviour in the composites.Interestingly, the team has been able to manufacture (thanks to 3D printing) a composite material that is more than 20 times larger than its strongest constituent.  The referenced paper showed that one can use computer model to design composite materials of their choice, tailor the fracture pattern and then use 3D printing technology to manufacture the composites.[Ref: L.S. Dimas, G.H. Bratzel, I. Eylon, and M.J. Buehler; Advanced Functional Materials, Published online June 17, 2013; DOI: 10.1002/adfm.201300215]...

Thermoplastic elastomers (TPEs) have been traditionally compounded and manufactured from raw materials based on fossil fuels.  Current trends in marketplace abounds sustainability programs. TPEs are no exception to this trend.   In a recent editorial, the authors stated “Through research and application, sustainability can evolve from a catchphrase to a societal one”1. More than two decades ago the Brundtland Commission (formerly the World Commission on Environment and Development, WCED), deliberated sustainable development issue and gave a definition of sustainability:

Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.1a

Keeping sustainability in mind, innovative developments are taking place in new TPE technologies based on bio-renewable resources.  The challenge however, is to provide the TPE product designers and the TPE product manufacturers with flexible products meeting broadest range of useful properties those contain a bio-renewable content.  Towards this objective, PolyOne has established “PolyOne Sustainable Solutions” certification to denote those products or services that meet defined standards for sustainability in areas such as renewability, recyclability, reusability, and eco-friendly composition or resource efficiency.  Let’s take a quick look at each of these categories to better understand how new TPEs to be discussed in this article provide sustainable solutions.

 

Renewable

Managing carbon in a sustainable manner is the central issue of sustainable development.  Traditional polymers such as PE, PP or PS are based on fossil feed stocks whose rate of carbon fixation is in millions of years, whilst their rate of release of carbon into the environment is 1-10 years. Clearly this increases atmospheric CO2.  On the other hand polymers which are produced from plant based, renewable feed stocks have their end-of-life CO2 release absorbed during the next planting season, thus balancing the CO2 release and trending towards a zero carbon footprint2. Polymers made from bio based materials may be derived from renewable resources by chemical methods, mechanical methods or produced directly by biological processes. TPE compounds based on renewable substances thus contribute to sustainable development by reducing the carbon footprint of the formulated TPE.

Recyclable

Recyclability considers solutions which incorporate post-consumer or post-industrial recycled content or which lend themselves to recycling such as PolyOne’s PlanetPak™ packaging system.   Among the various other advantages that come from processing thermoplastic materials, recyclability is a key factor for many processors when specifying TPEs in place of thermoset rubbers.  Not only can scrap produced during production (i.e. sprues) be ground and re-introduced with the virgin material, but finished articles can be reprocessed and recycled as well.

 TPEs can also make use of recycled products as a component of their formulation, for example employing post-consumer waste such as recycled tires, or post-industrial waste such as rubber dust or leather fibres.  Not only can these compound components provide sustainable solutions they can also reduce cost and provide functionality.

Reusable

Reusability considers packaging and other logistics related systems which are easily returned or reused.  Therefore, another important factor is to develop packaging & logistical solutions which help reduce waste and save costs.  Furthermore, PolyOne has pioneered novel, proprietary dusting systems which allow bulk packaging of TPEs that might otherwise have required more wasteful and costly packaging.

Eco-friendly Composition

Eco-friendly compositions are those solutions which respond to the ever-changing market needs by offering alternatives to traditional ingredients such as lead, bisphenol-A (BPA), phthalates and halogen-containing materials.    In many of the markets served by TPEs, there are compounds available which address these concerns. For example in the healthcare market, TPEs are designed to be phthalate free, plasticizer free and with low extractable, meeting stringent regulations and addressing real or perceived patient safety concerns4.  TPEs typically employ medical quality mineral oils which are much less scrutinized, but for the most sensitive applications plasticizer free TPEs offer the lowest level of leachable compounds.  Combined with careful component selection and specialized compounding techniques, TPE compounds can offer a very high level of purity and safety.

Which types of Renewable TPEs are available in the current market?

A number of different reactor produced TPE polymers have been commercialized by various manufacturers over the last few years.

Arkema’s Pebax Rnew is a polyether-block-amide (PEBA) block copolymer consisting of segments of amino-11 and polyether.  Since amino-11, is a derivative of castor oil, it is a biorenewable polymer with low environmental impact.  Arkema’s biorenewable TPEs contain 26-100% renewable content and have hardnesses from 35 to 72 Shore D.  They are promoted for various applications including electronics, shoes and automotive3,4.

DuPont’s renewable Hytrel RS thermoplastic polyester elastomers are based on their Cerenol polyols derived from bio-1,3propanediol produced from corn sugar using a patented bacterial fermentation process. Hytrel RS thermoplastic polyester elastomers contain 20 to 60% renewable based material.  They have hardnesses in the range of 30 to 83 Shore D and are promoted for use in applications such as hoses, tubing boots, energy dampers and airbag doors in automotive and industrial markets5.

Merquinsa’s Pearlthane ECO TPUs are produced from specially derived vegetable based polyols reacted with isocyanates in a novel patent pending process.  Whilst polyurethane foams using plant based polyols have been around for some time, difficulty reacting these polyols has restricted their use in thermoplastic applications, until now.  Merquinsa’s Pearlthane ECO TPUs contain from 30 to 90% renewable content according to ASTM D6866 and offer performance at least as good as traditional, high performance PCL based TPUs.  Products are available in hardnesses from 85 to 95 Shore A6.

In 2008, GLS Thermoplastics Elastomers launched two ranges of OnFlex™ BIO renewable based thermoplastic elastomers.  These product lines extended the functionality and performance of renewable thermoplastic elastomers available in the market opening up a wider range of applications and options for sustainable solutions.  Based on Merquinsa’s patent-pending Pearlthane® ECO technology these products feature at least 20% renewable material as certified by ASTM-D6866, meeting global market needs for sustainable and environmentally-friendly products. The OnFlex™ BIO 5100 series are glass fiber reinforced compounds which offer high stiffness in combination with excellent abrasion and impact resistance, a low coefficient of thermal expansion and excellent mechanical properties.  Typical applications for OnFlex™ BIO 5100 are industrial applications in demanding environments, sports equipment components such as ski bindings and caster wheels.

While OnFlex™ BIO 5300 series compounds are designed to offer the performance of traditional TPUs but with a wider range of hardness and easier processability.  These compounds have been designed to process well in injection molding, extrusion and calendaring processes.  Moreover these compounds offer exceptional abrasion, scratch and impact resistance, excellent tensile and tear performance, and adhesion to a wide range of substrates.  OnFlex™ BIO compounds are available from hardnesses of 70 Shore A upwards. Typical applications for OnFlex™ BIO 5300 compounds include automotive instrument panel skins, door panel skins, interior trim, gear knobs, shoe soles and grips on sports equipment.

For the purpose of a meaningful discussion of bio-renewable TPEs, it is important to understand the significance of terms such as Bio-sourced, Bio-degradable or Compostable.

Bio-sourced, Biodegradable or Compostable

Bio-plastics may be produced from renewable resources, biodegradable, or both.  Synthetic polymers either naturally or by virtue of chemical modification or the addition of certain additives can biodegrade making waste handling simpler. Polycaprolactone (PCL) is one such example7.  Certain bio plastics may be sourced from renewable resources but are not biodegradable, such as OnFlex™ BIO and Versaflex™ BIO.

The term biodegradation is not consistently used or clearly defined.  It may be used to mean fragmentation, loss of mechanical properties or degradation through the action of living organisms.  Sometimes deterioration or loss of integrity is mistakenly considered to be biodegradation.  Even the speed of degradation has to be taken into account. For example LDPE has been shown to biodegrade slowly to produce carbon dioxide (0.35% over 2.5 years)8.

Compostable means that materials will biodegrade only in a composting situation, that is, together with plant material in an aerobic environment.  Compostable plastics will biodegrade completely in the industrial compositing facilities. Not all biodegradable plastics are suitable for composting, as degradation may take too long or require higher temperatures to biodegrade completely.  The European standard EN13432 and the American standard ASTM D6400-04 helps to determine which plastics are compostable9.

Biodegradation of a material concerns only one aspect of its environmental impact and whilst it can be considered as part of an integrated waste management plan, it must be considered along with other issues such as the material source and carbon footprint.  In durable applications such as industrial and automotive markets biodegradation is undesirable.  In this case alternative methods of disposal must be investigated2.

The new TPE series, under the trade name VersaflexTM BIO those have been recently developed has opened up a new trend in this renewable TPE material segment.   

Versaflex™ BIO

Versaflex™ BIO series in Table 1 consists of a range of unique, patent pending renewable TPE compounds with some very special aspects.  These are based on novel and innovative compatible blends of a reactor produced TPE polymer, cross-linked elastomer and additives. These are the newest and most advanced renewable TPE solutions available globally.  They were launched in 2009 at the NPE exhibition in Chicago.  Versaflex™ BIO compounds are unique for their highest renewable content (up to 80%) for the hardness range of 20 Shore A to 90 Shore A with lowest specific gravity.  They are the softest renewable products on the market today, achieving performance currently unattainable with reactor polymer technologies.

   biorenewfig0

Table 1   Physical Properties of Versaflex™ BIO series

Not only do Versaflex™ BIO compounds offer very high levels of renewable content, they also help to reduce environmental impact through their low specific gravity, recyclability and ease of processability.

Dynamic Mechanical Analysis (DMA): Viscoelastic and Phase behaviour

DMA is particularly useful for determining viscoelastic behavior and phase transitions of a material, such as glass transition temperature (Tg) which can usually be easily identified by the peak of tan ? However, the peak location depends on the heating-rate and the frequency which may lead to different results than those obtained by differential scanning calorimetry (DSC)10.  DMA was conducted on samples of Versaflex™ BIO in order to understand the phase behavior of these novel complex blends and to predict the performance of these compounds at different temperatures.

The storage modulus G/ and loss modulus G// curves for two Versaflex™ BIO compounds across a range of temperatures are shown in Figure 1.  These curves indicates that these Versaflex™ BIO compounds have good flexibility between -30°C and above 100°C.  TPEs show a single transition as seen by the data.

biorenewfig1 

Figure 1.  Storage Modulus, G' and Loss Modulus. G'' of Versaflex™ BIO at 1 Hz

Tan ? is another measure of the mobility which is the ratio of the storage modulus and loss modulus as shown below:

                                                                 Tan ? = G// / G/

Figure 2, shows Tan ? curves for two Versaflex™ BIO compounds across a range of temperatures and indicates good flexibility and toughness of the TPEs in functional performance.

biorenewfig2

Figure 2. DMA Tan ? curves for Versaflex™ BIO at 1 Hz

The unique ingredients employed in Versaflex™ BIO provide a wide range of hardnesses, flexibility across a wide temperature range and a high renewable content.  A single Tg at low temperature clearly indicates the miscibility of the softer segment of the reactor based polymer TPE with the cross-linked elastomer.  There is a little shoulder around 75oC which is the Tg of amorphous phase of the reactor produced TPE elastomer in the compounded TPE.

Morphology

A number of microscopic techniques are available to understand the morphology of multiphase polymer blends.  Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) are the most commonly used methods.  AFM technique is the most user friendly technique requiring minimum sample preparation.

For TPEs, AFM is usually conducted in the tapping mode, meaning the cantilever is oscillated by peizo motion and brought into a light contact with the surface.  As the oscillating cantilever taps the surface, energy is lost due to the contact of the tip with the surface.  By measuring the cantilever amplitude information about surface morphology can be obtained.  AFM characterizes hard and soft phases, based on the effect of the modulus of these regions on the cantilever11.  This is particularly interesting for TPE blends which are typically composed of multiple ingredients of different hardness, crystallinity and other features. 

Information collected in an AFM scan is quantitative in three dimensions.  A micrograph can be presented as a topographical image with the elevation of each point encoded with a false color scale.  A 3D image can be manipulated with software, viewed from different angles, and measurements may be made on horizontal and vertical distances.  Surface roughness can be calculated along the lines or over planes. 

biorenewfigure3Figure 3. Atomic Force Micrographs (AFM) of Versaflex BIOTM 70A and 80A Morphology

AFM micrographs of two different Versaflex™BIO compounds are shown in Figure 3.  These micrographs clearly show phase separation on the µm scale. Interestingly, there is a phase change between 70 and 80 Shore A compounds; the co-continuous cross-linked elastomer (light) phase becomes dispersed into particles in a continuous reactor produced TPE matrix shown by the dark phase. These micrographs explain the improved elastic behavior and compression set for the 70 Shore A TPE compared to 80 Shore A with a penalty in tensile strength and 100% modulus.

Functional Performance: Oil Resistance 

Sebum oil and Skin So SoftTM exposure simulates functional performance in consumer applications, where as IRM- 903 Oil reflects the functional performance in demanding industrial and automotive applications. We have compared test data from Versaflex™ BIO compounds with a typical TPE-S and TPE-V to benchmark their performance in Figure 5.  We have looked at the % tensile change and % weight change after immersing samples in oil at specified temperatures for two weeks.   We have chosen a 40 Shore A and 60 Shore A versions of the Versaflex™ BIO compounds for these evaluations and 60 Shore A for the TPE-S (TPE-styrenic block copolymer) and TPE-V (TPE-vulcanizate of EPDM in PP).  The sebum resistance of VersaflexTM BIO is compared against typical TPE-S and TPE-V compounds.  VersaflexTMBIO 5500-60 shows outstanding sebum resistance and is comparable to TPE-V.  

   biorenewfigure4

Figure 4. Sebum Resistance of Versaflex BIOTM, TPE-S and TPE-V (2 weeks @ 40°C)

The soft, grippy nature of TPEs makes them attractive for use in grip applications. Among all renewable TPEs available Versaflex™ BIO is particularly appropriate for soft-touch grips due to its wide hardness range. In grip applications contact with various moisturizers and hand oils can lead to deterioration of performance, so Versaflex™ BIO was tested in contact with well known body oil, Skin So SoftTM lotion, a product of Avon Products Inc, and compared to traditional TPEs as a reference (Figure 5).

biorenewfigure5

Figure 5. Skin So SoftTM Lotion Resistance of VersaflexTM BIO, TPE-S and TPE-V (2 weeks @ 23°C)

In Figure 6 performance of Versaflex™ BIO compounds in IRM 903 oil are compared to a traditional TPE-S and   a TPE-V compound.  Despite the highly aggressive nature of IRM 903 oil, Versaflex™ BIO performs very well, with almost no weight gain and very little change in tensile performance over the testing period.  Not only does this corroborate the performance in contact with sebum and hand oils to which it might be exposed in consumer applications, but it also demonstrates performance that might be useful in industrial and automotive applications.

biorenewfigure6 

Figure 6. IRM 903 oil resistance of of VersaflexTM BIO, TPE-S and TPE-V (2 weeks @ 23°C)

Rheology, Processing and Applications

The hardness range and novel combination of properties make Versaflex™ BIO suitable for a very wide range of applications.  The capillary rheologies of Versaflex™ BIO TPEs are shown in Figure 7.  The viscosity shows shear thinning behavior and is very similar to a typical robust TPE grade which has fabrication versatility.  The capillary viscosities are nearly invariant for different hardness compounds at the measured range of shear rates. . 

biorenewfigure7

Figure 7. Capillary rheology @200°C of VersaflexTM BIO 

VersaflexTM BIO exhibit very robust processing using multiple fabrication methods.  Figure 8 shows three different fabricated forms produced from Versa flex™ BIO compounds.  Figure 8 a) shows stepped plaques injection molded from Versaflex™ BIO. Differing thicknesses demonstrate the translucency of the compound. Figure 8 b) shows a cast film extruded from Versaflex™ BIO, and Figure  8 c) shows a tube or hose extruded from Versaflex™ BIO.

biorenewfigure8 

Figure 8.  70 Shore A Versaflex™ BIO  a) Molded Plaques, b) Extruded Sheet , c) Extruded Hose

Figure 9 shows a blow-molded bottle produced from Versaflex™ BIO.  This can provide durability, toughness and flexibility for demanding applications with limited environmental impact. Furthermore, Versaflex™ BIO can be processed by multiple fabrication methods and can be colored to suit desired economics and aesthetics.

.biorenewfigure9.

Figure 9. 80 Shore A Versaflex™ BIO Blow-Molded Bottle

A limited over-molding evaluation performed on these compounds indicates that they do not bond to polyolefins and have poor bonding to engineering plastics such as ABS and polycarbonate.  Further evaluations for other substrates are underway.  At this time, Versaflex™ BIO is not recommended for over-molding applications.

Biorenewable TPE for Overmolding Applications

There have been tremendous interests and commercial applications for soft TPE over-molded to rigid plastics.  These over-molded TPEs can provide enhanced ergonomic feel and touch, gripability, aesthetics, cushion against impact, vibration isolation, etc.  Versaflex BIO materials described above can be used as a stand alone TPE, however, they are not designed for over-molding applications.  Recently a new line of renewable TPE with very high renewable content was developed for over-molding applications.

 The adhesion between the TPE and rigid thermoplastics substrates was measured by a “90 degree peel test” which is a modified ASTM D903 method.  This test is done on over-molded plaques with TPE on top of rigid thermoplastic substrates.  A 25 mm wide strip of TPE is cut and pulled at a 90o angle toward the substrate using an Instron tensile tester. The substrate is locked in its place on wheels in order to maintain the 90o angle as the elastomer is pulled. The adhesion strength, i.e., peel strength, is measured by the force required to pull the elastomer from the substrate and is reported as an average or a maximum strength over 50 mm of pulling. The adhesion is also categorized based on a visual observation of the failure mode, i.e., an adhesive failure if no TPE residue is left on the substrate or a cohesive failure if the failure is in TPE.

Table 4 below listed the mechanical properties of these new renewable TPEs.  These TPEs are developed from compatible blends of commercially available reactor grade TPE with crosslinked elastomers and plasticizers.  The materials have a renewable content of 60-70%, and are available from 40 to 70 Shore A hardness, however, broader range of hardness can be developed based on similar chemistry.  The bonding strength to polar substrates is considered good (>10 pli) to excellent (>15 pli).  These are the softest and highest renewable content TPE with good overmolding properties on polar substrates.

 

 biorenewtable2

Table 2. Physical Properties of New Bio-renewable TPE for over-molding Applications

References

1.     J.C. Crittenden and H.S. White; Harnessing Energy for a Sustainable World, J. Am. Chem. Soc., 132 (13), pp. 4503-4505 (2010)

1a.  Our Common Future, Report of the World Commission on Environment and Development, World Commission on Environment and Development.  1987

2.     Narayan, R., Bioplastics or Biobased (Renewable) Materials 101.  Michigan State University. The authors here use “free” as an indication that there is no intention to include the particular chemical in the mixture.

3.    Eustache, R., Lé G., Silagy, D.  PEBA made from Renewable Resources or How to Offer Simultaneously Sustainability and High Performance. The Eleventh International Conference on Thermoplastic Elastomers.  Rapra 2008

4.    Arkema, www.pebax.com

5.    DuPont, www.dupont.com

6.   Julia, J., Santamaria, J.  New Thermoplastic Polyurethane (TPU) from Renewable Sources.  The Eleventh International Conference on Thermoplastic Elastomers.  Rapra 2008

7.   Kulshreshtha, A. K., Vasile, C.  Handbook of Polymer Blends and Composites (Vol 4, pp: 632).  Smithers Rapra Technology, 2002

8.   Bastioli, C. Handbook of Biodegradable Polymers. (pp: 2, 219, 257, 272).  Smithers Rapra Technology, 2005

9.   Renewable Polymers.  www.nnfcc.co.uk, The National Non-Food Crops Centre, 2009

10. Ramachandran, V.S., Paroli, R. N., Beaudoin, J.J., Delgado, A. H., Handbook of Thermal Analysis of Construction Materials.  William Andrew, 2002

11. Mark, J. E., Erman, B., Eirich, F. R., Rubber Science and Technology.  (pp: 606).  Academic Press, 2005

 

Krishna Venkataswamy

Dr. Krishna Venkataswamy is the Senior Director, Global Research and Development for GLS Thermoplastic Elastomers, PolyOne Corporation.  He has been active in the TPE industry for the past 22 years and at GLS since 2001.  He has held management and technology leadership positions at GAF Materials Corporation, Advanced Elastomer Systems (ExxonMobil) and Monsanto.  He has developed many commercially successful products in the consumer, medical, automotive and industrial applications.  Krishna has authored more than 50 technical papers and patents.  He has received “SPE Fellow” award in 2006 for his technical and leadership contributions in Thermoplastic Elastomers. In addition, he has received SPEs “Outstanding Achievement Award for Leadership” in 1999.  He has been the recipient of “Sherwin-Williams” award in Applied Polymer Science from the American Chemical Society in 1986 for a paper from his Ph.D work.  Krishna has been very active in SPE; Current Chairman of New Technology Forum, Past Chair of EPSDIV and Board member Akron Section, Past Chair of SPE TPE Topical conferences including the first two-day International Symposium on TPEs during ANTEC during mid-90s.  He has a BS in Chemical Engineering from the Indian Institute of Technology, Madras, an MS in Materials Science & Engineering from University of Florida and a PhD in Polymer Science and Engineering from Case Western Reserve University.

Figure 7. Capillary Rheology @ 200oC of VersaflexTM BIO

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