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]...

Fillers have been in use since the early days of plastics.  Today’s enormous growth of the polymer industry is due to the unique properties of fillers they impart to polymers.  Glass bubbles (low density hollow glass microspheres) as fillers have been incorporated into thermoset polymers for decades.  They are tiny hollow spheres and are virtually inert.  These glass bubbles are are compatible with most polymers.  Until recently, their use with thermoplastic polymers has been limited because of high rates of bubble breakage from the high shear forces to which they are exposed during such thermoplastic processing operations as extrusion compounding and injection molding.  At issue has been the strength of the glass microspheres.

3M have recently developed innovative glass bubbles which offer resistance to extremely high compressive and shear forces.  This allows compounders, thermoformers and injection molders to use them to achieve significant weight reductions without restoring to costly equipment modifications.  This article will showcase how plastics processors could exploit the advantages of these novel glass bubbles while improving the end-product properties.

1.0        Glass bubbles : Why use them in plastics compounds?

 

3MTM Glass Bubbles  (hollow glass microspheres) (Figure 1) are weight reducing fillers which can be incorporated into various polymers by melt compounding and processed into articles via thermoforming, blow molding,  sheet casting, injection molding and etc.

glass_b_figure_1
 

Figure 1. Hollow Glass Microspheres

 

Compared to other heavy fillers such as talc, calcium carbonate, glass fiber, and clay (from 2.5 to 2.8 g/cc), glass bubbles (GB) for plastics and rubber applications have densities ranging from 0.1 to 0.6 g/cc (Figure 2).


glass_b_figure_2 

Figure 2. 3MTM Glass Bubbles vs. Other Heavy Fillers

 

Reducing the weight has been a paramount objective in various industries, such as transportation, aerospace, and hand-held electronics. A few words on the historical trends in transportation industry would be illustrative to set the scene. The trend of reducing the weight which in turn would reduce the fuel consumption in transportation became dominant after the first oil crisis which affected the Western World in mid-1970s and continues to be an active research field. A recent historical analysis of fuel efficiency of US vehicles [1] before the mid-1970s indicated little change – indeed a net deterioration – in average miles-per-gallon (mpg) of vehicles in US between 1923 (14 mpg) and 1975 (12 mpg). The step change in oil prices during the 1970s (Figure 3) triggered a strong interest in improving the fuel efficiency in transportation which continues to be prevalent today and has resulted in a current fleet fuel efficiency of around 17 mpg [1]. In view of the historical data, it is not surprising that the global rise in oil and energy prices in the early 21st century (Figure 3) triggered a renaissance of light weight material applications. Note that current real (adjusted for inflation) oil prices are higher than what was experienced during the first oil crisis of the 1970s (Figure 3).

 glass_b_figure_3

Figure 3. Real (adjusted to inflation) US retail gasoline prices. The plotted data were obtained from: www.eia.doe.gov (accessed December 20, 2010)

 

The importance of reducing the weight and its relationship to fuel consumption is illustrated in the following scenario. One may estimate that the body panels, hoses, bumpers, doors, and the car interior count for about 50% of the total weight of a standard passenger car. On average, about 300 Ibs of filled and unfilled polymers of various densities ranging from 0.9 g/cc to 1.68 g/cc are used in these components [2]. Table 1 summarizes weight reductions that could be achieved in these parts at different GB wt% loadings with two grades of glass bubbles, K42HS and IM30K. The table indicates that a 50 lb to 100 lb weight reduction can readily be achieved in a car having 300 lbs of polymeric parts. Based on a recent study, this would result in an increase of fuel efficiency up to 2 % [3].

glass_b_table_1
 

Table 1. % Weight Reductions in the Presence of 3MTM Glass Bubbles

 

Current interest in new light weight materials covers a broad spectrum from light weight metals, such as aluminum and magnesium, to carbon fiber reinforced plastics. Although the majority of these are technically viable solutions, many of them pose challenges both to the producer and to the customer. New materials, such as carbon fibers, are usually significantly more expensive than the traditional industrial materials and might require additional processing and assembly steps which may increase the total cost. Most crucially, new materials usually require additional time and funds for testing, validation, and design trials which may prolong the product launch and increase cost. 3M glass bubbles offer a ‘plug-and-play’ solution for reducing the weight of plastic parts without requiring significant material and process changes. 3M glass bubbles can be easily compounded with various polymers using the conventional melt processing operations such as extrusion.  The resulting compounds are strong enough that the glass bubbles will not break, even in high shear, high pressure processes like injection molding.  Figure 4 shows a few examples in different polymer systems.

glass_b_figure_4 

Figure 4. Examples of Polymer + 3MTM Glass Bubble Composite Systems

 

The isostatic crush strength (psi) versus the corresponding true density (g/cc) of the glass bubbles are shown in Figure 5 along with their average diameters indicated in the circles.

glass_b_figure_5 

Figure 5. Isostatic Crush Strength vs. the Corresponding True Density of the 3MÔ Glass Bubbles (the number in the colored circles indicates the average diameter)

 

The recently developed 3M glass bubbles such as XLD6000, K42HS, and iM30K, which fall onto the “High Strength GB Trend” line in Figure 5, are optimized to improve their compressive strengths.  They have noticeably smaller average particle sizes and narrower particle size distributions compared to their same density counterparts as shown in Figure 6.

 glass_b_figure_6

Figure 6. Comparison of the Same Density 3MTM Glass Bubbles (0.6 g/cc) with Different Particle Sizes and Size Distributions

 

The appropriate glass bubble grade for weight reduction is typically the lowest density with the highest survival rate in a given polymer system.  The base polymer resin viscosity and the level of pressure fields experienced in the process influences the survival rate of the glass bubbles. High melt viscosity materials in high pressure polymer processes (e.g. injection molding) require stronger glass bubbles such as 3M Glass Bubble iM30K. Nevertheless, there is no strict rule and several grades of lower density bubbles (e.g. 0.3 g/cc at 6000 psi) can still be injection molded successfully with minimal bubble breakage provided that the conditions are set correctly. We will review process parameter considerations in the next section.

 

2.0        Things to consider during its processing

 

2.1        Extrusion compounding

Compounding of 3M glass bubbles in a twin screw extruder is similar to that of glass fibers where the fiber attrition is kept to a minimum by introducing the fibers downstream into the molten polymer. The appropriate twin screw extruder is typically a co-rotating intermeshing or a counter-rotating non-intermeshing parallel twin screw extruder. Glass bubbles are preferably added downstream into the main extruder via side stuffing or top feeding ports. For high loadings of glass bubbles, it is important that the screw elements in the glass bubble feed zone have large free volumes with large channel depths. One of the advantages of glass bubbles over other fillers, such as clay or talc, is that they do not form agglomerates in the melt and readily distribute themselves in the molten polymer without having to resort to special distributive mixing elements. Standard forward conveying elements are sufficient to convey and distribute the bubbles in the molten polymer. Pressure generation via reverse elements or wide kneading blocks, typically used for dispersion, i.e. agglomerate break up, should be avoided.  If required, narrow kneading blocks with a small number of disks can be used. Another important factor for glass bubble survival in twin screw extrusion is back pressure applied by the presence of the die and melt screen. Increasing the number of strand holes in the strand die along with the diameter of the openings increases glass bubble survival by reducing the back pressure.

The strongest grade of glass bubble, 3M Glass Bubble, IM30K [4], can provide an economical alternative for compounders who are unable to implement side stuffing or downstream feeding. Compounding trials in which iM30K 3MÔ  glass bubbles were fed through or near the hopper indicated relatively reduced extent of breakage of the fillers. However, it should be emphasized that side feeding downstream is still preferable for 3M Glass Bubble iM30K as well.

 

A preferred screw configuration with downstream glass bubble feeding, along with downstream glass fiber feeding, is shown in Figure 6. Note that the glass bubbles are introduced after feeding all other components to the process.

glass_b_figure_7 

Figure 7. Representative Extruder Screw Design for Compounding 3MÔ Glass Bubbles

 

2.2        Injection Molding

Injection molding involves high pressure fields and hence more attention has to be paid to prevent glass bubble breakage. There are two zones in the process where the glass bubble breakage can occur. The first one is the plasticating zones where the polymer is molten and conveyed to get ready for injection into the mold. Back pressure, which increases shearing of the polymer melt, has to be set low enough to prevent glass bubble breakage but high enough to provide a compact melt and prevent air bubble formation in the plastic melt and eventually in the finished part. Next, the injection rate should be kept low enough to prevent injection pressures exceeding the iso-static crush strength of the glass bubbles. Likewise, holding pressure should be lower than what the glass bubble isostatic crush strength is rated for. Injection pressure is also determined by the intensification ratio, i.e. area of the ram /area of the screw, and should not exceed the pressure ratings of the glass bubble [5]. As for tooling, a general-purpose injection screwbarrier is recommended. Double-vane or vented designs are not recommended. Sharp edges on the nozzle should be avoided and sprue orifices should be at least of 0.25 in diameter. Use of full-round or trapezoidal runners cut into both plates having a minimum radius of 0.125 in are recommended.

 

 

3.0       A Case Study on the Properties of 3MÔ Glass Bubbles in Glass Fiber filled Nylon 6,6

 

Glass bubbles are excellent strength/weight optimizers when they are used in filled polymer systems such as glass fiber, talc, and calcium carbonate filled thermoplastics. Replacing a certain percentage of these high density fillers with glass bubbles results in weight reduction while maintaining  the original mechanical properties. As an example this is shown in the following case study with glass fiber filled nylon 66.

 

3.1        Materials

Commercially available, high strength (18000 psi isostatic crush strength), low density (0.60g/cc) glass microspheres  (3MTM glass bubbles S60HS) were selected for these experiments.  A commercially available, injection molding grade of polyamide 66 was obtained from E.I. DuPont de Nemours Company under the trade name Zytel®101LNC010 [6]. Glass fibers, PPGÔ Chopvantage 3540, with a density of 2.65 g/cc were obtained from PPG Industries [7].

 

3.2        Compounding and injection molding

All samples were compounded on a Berstroff Ultraglide twin screw extruder (TSE 25 mm screw diameter; length to diameter ratio of 36:1) equipped with top feeders for microspheres and glass fibers (GF), a water bath, and pelletizer . Screw speed ranged from 140 to 160 rpm. Temperature set points ranged from 500ºF to 575ºF. Test specimens were then molded on a 150 ton Engel injection molding machine using an ASTM four cavity mold. The screw diameter was 30mm and the injection pressure was maintained below 18000 psi to prevent glass bubble breakage.

 

 

3.3        Testing and Characterization

Flexural strength and flexural moduli were determined according to the ASTM D790. Notched Izod impact properties were determined according to ASTM D252. Tensile mechanical properties were determined according to the ASTM D638. The density of the injection molded parts was determined using a helium gas pycnometer.

 

3.4        Results and Discussion

The results in Table 2 indicate that the presence of 3M Glass Bubble S60HS significantly reduced the density of the injection molded parts. One can also note the strength/weight optimization via the use of glass bubbles in glass fiber filled nylon 66.  Glass bubbles allow the end product properties to be retained to a large extent while decreasing the density. For instance, the formulation with the 10wt% GF and 90wt% Nylon 66 (C-3) has a final part density of 1.20 g/cc with a tensile strength (TS) of 73 MPa, tensile modulus (TM) of 5.47 GPa, flexural strength (FS) of 147 MPa, flexural modulus (FM) of 4495, unnotched Impact (UI) of 2.8 J/cm and notched impact (NI) of 0.6 J/cm. If one desires to double all of the mechanical properties, the GF content has to be increased from 10wt% to 33% (see formulation C-1). This would increase the density from 1.20 to 1.39 g/cc. The doubling of these properties can also be obtained using formulation #4 with a density of 1.19 g/cc which contains glass bubbles.

glass_b_table_2 

Table 2. Physical Properties of 3MÔ  Glass Bubbles S60HSfilled Nylon 66 Composites

 

In order to improve the properties of composites further, glass bubbles are surface treated with silanes to improve compatibility with various polymers. Figure 7 shows silane treated 3M Glass Bubble IM30K which shows improved adhesion to the polymer matrix.

glass_b_figure_8

Figure 8.  Scanning Electron Microscopy Image Showing Improved Adhesion to the Polymer Matrix via Silane Treatment

 

4.0        Additional Benefits

 

There are several other benefits of adding glass bubbles into thermoplastics compounding formulations. These can be outlined as reduced cycle time in thick molded parts, decreased mold shrinkage and part warpage, and reduced coefficient of thermal expansion as discovered during numerous laboratory and plant trials. Figure 9 shows the effect of glass bubble loading on the Coefficient of Linear Thermal Expansion (CLTE) of the Nylon 66 at different temperature intervals. 25 to 30% decrease in CLTE can be achieved in Nylon 66 with the addition of glass bubbles up to 30 vol %. Likewise, Linear Mold Shrinkage (LMS) decreases as the amount of glass bubble loading is increased. 50% reduction in LMS is observed in injection molded polypropylene containing 30% by volume IM30K.

glass_b_figure_9

Figure 9.  Coefficient of Linear Thermal Expansion (CLTE) of Nylon 66 as a Function of Glass Bubble Loading

 

glass_b_figure_10

Figure 10.  Effect of Glass Bubbles on Linear Mold Shrinkage

 

 

5.0        Conclusions and Future Outlook

 

Compounding 3M Glass Bubbles with polymers offers a ‘plug-and-play’ weight reduction solution. The method is rapid, cost effective, and does not require any complex material or process modification.  

3M Glass Bubblescan be added to high density filled polymer composites (talc, glass fiber, carbon black, calcium carbonate and etc) to optimize density-and mechanical strength. 

In addition to weight reduction, laboratory and plant trials also indicated that additional processing and material related improvements can be achieved by the addition of glass bubbles into compounding formulations. These can be summarized as reduced cycle time especially in thick injection molded parts, decreased part warpage due to isotropic nature of the fillers, reduced coefficient of thermal expansion, and decreased mold shrinkage.

 

References

  1. M Sivak, O. Tsimhoni. Fuel efficiency of vehicles on US roads: 1923–2006. Energy Policy 37, 3168-3170, 2009.
  2. N. G. McCrum, C. P. Buckley, C. B. Bucknall. Principles of Polymer Engineering, 2nd ed. Oxford University Press, New York, 1999. pp. 8-10.
  3. J. Pflug, B. Vangrimde, I. Verpoest. Material efficiency and cost effectiveness of sandwich materials, SAMPE Conference, Long Beach, CA USA, 2003
  4. iM30K 3MÔ Glass BubblesProduct Information, issues by 3M Company on August 2006.
  5. 3M™ Glass Microspheres Compounding and Injection Molding Guidelines, Issued by 3M Company 3/08.
  6. Zytel® is a registered trademark of E. I. du Pont de Nemours and Company.
  7. The PPG® name is a trademark of PPG Industries.

13M Energy & Advanced Materials Division, 3M Center, St. Paul, MN, USA

2 3M Safety Security & Protect Bus, 3M Center, St. Paul, MN, USA

33M Corporate Research Process Laboratory, 3M Center, St. Paul, MN, USA

*Corresponding authors:

 

Baris Yalcin, Ph.D.

Application Development Specialist, 3M Energy and Advanced Materials
3M Center, 236-0G-B68, St. Paul, MN, 55144-1000, USA
Office: 651 733 6959 | Mobile: 651 387 1460 | Fax: 651 736 7794

e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. (B. Yalcin)

Steve E. Amos, Ph.D.

Sr. Product Development Specialist, 3M Energy and Advanced Materials

3M Center, 236-0G-B68, St. Paul, MN, 55144-1000, USA
Office: 651 737 3045 | Mobile: 612 281 3337 | Fax: 651 736 7794

e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.(S.Amos)

 

Baris Yalcin, Ph.D.

Baris is an application development specialist in 3M Energy and Advanced Materials Division. He has a Ph.D. in Polymer Engineering from The University of Akron, Akron, OH, USA. From 2004 to 2010, he has worked as the center manager and researcher for the Center for Multifunctional Polymer Nanodevices and Materials (CMPND) at The University of Akron, a third Frontier Project initiative by the State of Ohio to expand Ohio's high-tech research capabilities and promote innovation and company formation. His expertise is on the manufacture and investigation of advanced functional polymer based materials with innovative process design concepts. He has over 25 technical publications/patents.  He is a member of the Society of Plastics Engineers and is an active reviewer for several refereed plastics journals.

 

Steve E. Amos, Ph.D.

Steve has an MS in Polymer Science from the University of Ferrara, Ferrara, Italy and a BS in Chemistry for the University of Wisconsin-Madison.  He has been involved with product development, materials and application research at 3M Company since 1994.  Materials that he has worked with at 3M include fluoropolymers, glass bubbles, nucleating and clarifying agents, flame retardants, fluorochemicals and ceramic microspheres.  He has numerous technical publications and patents.  He is a member of the Society of Plastics Engineers (SPE) and a past board member of the Polymer Modifiers and Additives Division of SPE.

I. Sedat Gunes, Ph.D. 

Sedat received his PhD in Polymer Engineering from The University of Akron, Akron, OH, USA under the guidance of Professor Sadhan C. Jana. He serves in the Editorial Board of Journal of Plastic Film & Sheeting, in the Society of Plastics Engineers New Technology Forum Organization Committee, and in ASTM Committees D20: Plastics and E56: Nanotechnology. His professional experiences focus on processing and characterization of polymers and nanocomposites.

Andrew D’Souza, Ph.D.

Andrew  is a Product Development Specialist in 3M's Safety and Security Protection Services Lab.   Prior to that, he has worked in glass bubble technology and polymer processing in 3M's Energy and Advanced Materials Division.  He holds several patents and publications in the area of ceramic processing, glass science and technology and specialty coatings.  Dr. D'Souza has a  Ph.D. in Material Science and Engineering from The Pennsylvania State University