PEL PLASTICS UPDATE highlights recent progress in key areas of polymer/plastics technology including: catalysis, biopolymers, smart/functional polymers, alloys & blends and polymer modification. A recent issue of PEL Plastics Update follows.

Complimentary Copy
Vol. 5, No. 5
PEL PLASTICS UPDATE
Sept-Oct, 1997
By Mort Wallach
ISSN 1094-656X
 

Nanotechnology-New polymer composites with nanoscopic silicate minerals exhibit improved properties including flame resistance, structural characteristics, and gas barrier features which have important industrial potential. Polyimide nanofoams were developed with possible applications in microelectronic devices, and optically transparent polyimide composite waveguides were prepared by dispersing nanosized TiO₂ particles into the polymer matrix.

• Prof. E. Giannelis and coworkers at Cornell in Ithaca, NY and Kolon Chemical, of S. Korea prepared nanocomposites with enhanced properties by attaching alkyl chains to the surface of mica-type minerals dispersed in polymers including polyesters, polystyrene, and polyethylene oxide. The cation-exchanged silicates readily form nanocomposites of either intercalated (slightly separated silicate layers) or an exfoliated arrangement (highly dispersed mineral blocks). Property enhancements include flame resistance, structural features and gas diffusion. These systems have important practical potential in a variety of markets including automotive, appliances and electrical applications. (M. Jacoby, C&EN, Oct. 6, 1997, p. 35)

   

• R. Briber and coworkers at U. of Maryland in College Park have prepared new polyimide nanofoam films with possible applications in microelectronic devices. They were produced from triblock copolymers derived from polyimide as the center block [e.g., pyromellitic dianhydride-1,1-bis(4-aminophenyl) -1-phenyl-2,2,2-trifluoroethane] and polypropylene oxide as the end blocks. The nanofoam was produced in a three step process: spin-casting the triblock copolymer onto a Si substrate, thermal imidization of the center block and thermal treatment in air to degrade the polypropylene oxide domains and form nanoscale voids. (Mater. Res. Soc. Symp. Proc., 461, 103, 1997)

   

• P. Prasad and coworkers at SUNY, Buffalo have prepared optically transparent polyimide-TiO₂ composite waveguide materials by the dispersion of nano-sized TiO₂ particles into the polyimide matrix. The particles were produced through reverse micelles using the sol-gel method, and were dispersed into the fluorinated polyimide (Ultradel 9020D) solution. The solution was coated on to a glass substrate, and a polyimide-TiO₂ composite waveguide (4 wt % TiO₂ concentration) was successfully produced after heat treatment. Because the particle size was very small, no noticeable scattering loss was observed. The measured optical propagation loss at 633 nm was 1.4 dB cm^-1. It is equivalent to that of the pure polyimide, and the refractive index was increased from 1.550 to 1.560 by the incorporation of the TiO₂ particles. This is another demonstration of the diverse and important applications of nanotechnology. (J. Mater. Sci., 32, 4047, 1997)

Supramolecular Structures-Polyion films in intricate tailored patterns were built into ultra-thin multilayers on gold substrates. Chemical functionality was directly programmed into the surface so that adsorbed polyions form microstructures by self-assembly. The technique has much promise and could be used for device fabrication involving customized refractive index, or unique emittance, or electron-transfer properties.

• Prof. P. Hammond and coworkers at MIT have created supramolecular structures with controlled nanometer sized horizontal and vertical resolution. An example involves coating gold surfaces with parallel columns of polyion films, e.g., strips of film a few hundred nanometers thick form 3.5 µm wide lines separated from each other by 2.5 µm. Substrates were prepared using the microcontact printing technique developed by G. Whitesides of Harvard. The gold surface patterned with regions of alternating chemical functionality serves as a molecular template for polyanions. Adsorption of polyanion layers thereby proceeds with lateral selectivity and researchers can experimentally control whether layers of polycations or polyanions preferably assemble on selected regions. Since chemical functionality is directly programmed into the surface, adsorbed polyions form microstructures by self-assembly. The method has much promise for making electronic and optical devices such as electroluminescent instruments and sensors that diffract light of certain wave lengths under controlled conditions, and possibly wave guides for fiber optics. (PMSE, 77, 620, 1997)

Biopolymers-Further understanding of how the protein p53 protects against cancer has been uncovered as a three step process by which p53 kills potential cancer forming cells.

• B. Vogelstein and coworkers at Johns Hopkins U. in Baltimore have developed a biomolecular map of how the p53 protein protects against cancer by determining which genes are activated by p53. Measurements were made of the amount of various messenger RNA molecules present in cells that contain active p53 as compared to mRNA in control cells. The mRNA levels indicate which genes are functioning and their level of activity. In this way the researchers identified genes which were activated by p53 and their function. It turns out that many of these genes encode proteins that can generate or respond to oxidative stress. Overall, these results suggest that there is a three step process by which p53 kills cells that otherwise could become cancerous. First the p53 switches on redox-related genes. Products of these genes then produce reactive oxygen species which cause degradation of components of the cell's mitochondria. This leads to the death of cells which are potentially cancerous. (Nature, 389, 300, 1997)

Alloys & Blends-In studies of the compatibilization of the polyamide/polyethylene system with functionalized polyethylene (PE-g-GMA), Nylon 11 exhibits the most efficient grafting as compared to several other aliphatic polyamides.

• E. Koulouri and workers at U. Patras, in Patras, Greece have investigated the grafting efficiency of different nylons (e.g., 6, 11, 12, 6-10, and 6-12) with ethylene-glycidyl methacrylate copolymer (PE-g-GMA) and ethylene ethyl acrylate copolymer at a composition of 85/15, when melt-mixed under optimum conditions. Two of these-nylon 6 and 11-were studied in the complete composition range. Using techniques like dynamic mechanical analysis, tensile testing, differential scanning calorimetry, SEM, and Fourier transform infrared spectroscopy (FTIR) for the characterization of the blends it was shown that the most efficient grafting occurred in the case of nylon 11/PE-g-GMA blends. The formation of a copolymer was confirmed by extraction experiments. The existence of both polymers in the isolated copolymers was proven by FTIR and thermal analysis. Overall, the concept of the compatibilization of the polyamide-polyethylene system was confirmed in the case of nylon 11/HDPE compatibilized by PE-g-GMA. (Polymer, 38 (16), 4185, 1997)

Alloy & Blend Patents-Among 1000 patents reviewed during this period, several noteworthy inventions include: ternary polyetherimide/polyester blends with improved transparency, TPO laminates for automotive parts, transesterification inhibited PET compositions, and inorganic compound-coated film with good moisture resistance.

• "Ternary Polyetherimide/Polyester/Polyester Blends With Improved Transparency". C. E. Scott (Eastman Chemical Co.) US 5,648,433, July 15, 1997. A visually clear blend of thermoplastic polymers comprises (A) a polyetherimide, (B) a mixture of polyesters comprising: (1) a polyester comprising repeat units from (a) 2,6-naphthalene dicarboxylic acid and (b) ethylene glycol (I) and (2) a polyester comprising repeat units from (a) an acid of terephthalic acid and isophthalic acid or mixtures thereof, and (b) a glycol of I 1,4 cyclo-hexanedimethanol (II) or a mixture thereof. A blend containing Ultem 1000 (polyetherimide) 30, I-dimethyl 2,6-naphthalene dicarboxylate copolymer 14, and di-Me terephthalate-I-II copolymer 56%, gave injection-molded test pieces with clear appearance, Rockwell hardness 104L, and flexural modulus 342 kpsi. (Chem. Abs. 127: 136506t)

   

• "Thermoplastic Elastomer Composition Laminates For Automobile Parts". K. Kobayashi (Mitsui Petrochemical Ind.) JP 09,156,009, June 17, 1997. The title laminates, giving automobile parts having good scratch resistance, lightweight, recyclable, and no toxic gas generation, even on incinerating, comprise (a) an embossed surface layer prepared from (a1) polyolefin blends containing 15-45% ultrahigh molecular weight polyolefins (e.g., UHMWPE) and 60-85% low-or high-molecular weight polyolefins (e.g., LDPE) 10-50, (a2) hydrogenated block copolymers of styrene (derivatives) block and isoprene or butadiene-isoprene block (e.g., hydrogenated isoprene-styrene block copolymer) 50-90, and optionally (a3) silicone oil (e.g., SH 200) aliphatic alcohol-(dicarboxylic acid or fatty acid) esters (e.g., distearyl phthalate) fluoropolymers (e.g., KF Polymer W-1000), and/or fatty amides (e.g., erucamide, oleamide, ethylene bisoleamide) 0.01-10 parts, and (b) a base layer of (b1) polyethylene or polypropylene foams or (b2) crystalline polyolefins or polyolefin-olefin rubber (e.g., EPDM) crosslinked products. (Chem. Abs. 127: 122676m)

   

• "Transesterification-Inhibited Poly(Ethylene Terephthalate) Melt Blend Compositions Having Improved Dyeability". W. Cattron et. al. (Amoco Corp.) US 5,646,208, July 8, 1997. Melt blend compositions, useful for shrink fiber and film and as powdered binders for nonwoven fabrics having high m.p., improved dyeability and good solvent resistance, comprise poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) or random copolymers of poly(ethylene terephthalate) and poly(ethylene isophthalate) and an inter-esterification inhibitor. Thus, PEI dried pellets (prepared from isophthalic acid and ethylene glycol) 566.7, PET dried pellets 2266, and Ultranox 626 [bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite] transesterification inhibitor 14.24 g were blended and melt-extruded at 280C to give a blend showing m.p. 253.0C, T_g 76.0C and fiber shrinkage (2 min at 80C, spun at 32 m/min) 9.5%. (Chem. Abs. 127: 149783f)

   

• "Inorganic Compound-Coated Plastic Film With Good Moisture Resistance And Good Flexibility". T. Azuma et. al. (Kureha Chemical Ind.) JP 09,183,179, July 15, 1997. The film comprises, in sequence, polymer substrate, evaporation coated inorganic compounds, gas-barrier polymer coatings and relief layers, where the relief layers (Lf) satisfy with 5 N/mm < elastic modulus of Lf (GPa) x thickness (µm) of Lf < 90 N/mm. Thus, a film was prepared by bonding a Si oxide-coated (on PET side; thickness 3 µm) laminate of PET and vinyl chloride-vinylidene chloride copolymer and LDPE (thickness 40 µm; elastic modulus of MD 0.18 GPa, of TD 0.22 GPa). (Chem. Abs. 127: 150017r)

Automotive Plastics-Thermoplastic car-body materials are being employed in several new models. Favored materials include: alloys & blends and composites of Noryl GTX (nylon/ PPO), Azdel PP glass mat, PET glass filled polymer, and Xenoy (PC/PBT) systems. Cars employing these plastic body materials are no longer niche vehicles with production levels expected at 100,000 to 200,000 vehicles/yr. Several of these applications were shown at the recent show in Frankfort.

• Unveiled at the recent Frankfort International Motor show was the plastic-bodied Composite Concept Vehicle (CCV) by Chrysler made of recyclable 15% glass filled PET. Panels are assembled (4 per car) with polyurethane adhesive on a steel chassis. There are only 1100 parts (vs 4000 conventionally) and no paint is required. The car weighs half as much (1,200 lb) as a comparable metal car, and gets 50 mpg. The plastic panels can be recycled and contain up to 20% recycled PET themselves. The car is aimed for developing countries by the year 2000 and will sell for about $6000. The panels are molded on a 9000 ton injection molding machine with 160 ton molds which are 3X larger (14 X 8 X 6 ft) than any other mold used in automotive applications. The polyester composite is relatively inexpensive at $1.50/lb compared to other plastic blends and composites. Cycle times are only 3 min (vs twice that for comparable SRIM sections) due to novel gate and gas injection sequences. Other cars introduced with plastic panels include the new Mercedes compact A-Class tailgate of Noryl GTX outer skin (and front fenders) and Azdel PP glass mat inner skin; the new Land Rover Freelander also with front fenders of Noryl GTX; the new VW Beetle with front and rear fenders of the same material. GE claims car manufacturers can achieve up to 50% fender weight reduction by switching from steel to Noryl GTX, with repainting only required at collision speeds of 35 km/hr compared to the need for steel fender replacement after simulated collisions of just 8 km/hr. Meanwhile, the Mercedes/Swatch joint venture (MCC) also introduced a completely plastic clad car which is due in production very soon. It has self-colored Xenoy (PC/PBT) exterior panels with a clear coat. (Modern Plastics, Oct. 1997, p. 17)

New Polymer Ventures/PEN-Several major chemical companies including (Amoco, Eastman Chemical, Shell, ICI, DuPont, Teijin Chemical, and Mitsubishi Gas Chemical) have entered the poly(ethylene naphthalate) (PEN) business. Key target markets include glass and aluminum which supply 16 billion bottles for beer and 35 billion cans for soft drinks annually. However, some important issues remain including monomer availability, pricing, FDA and recycling concerns. Performance-wise the future looks good with markets including film, fiber, and packaging. PEN's rigid chain architecture accounts for its increased strength, heat stability, and barrier features as compared to PET. Current entry markets involve specialty films such as in advanced photo system cameras (where PEN provides thinner gauge and better curl resistance), and electronic film applications (where PEN enhances thermal performance, aging, and dielectric properties). However the film market now represents only a small specialty opportunity of 2MM lbs (with 9 MM lbs projected for the year 2000). Amoco Chemical is the only US producer of the main PEN raw material naphthalene dicarboxylate (NDC) and the price of PEN ($4-5/lb) is strongly determined by that of NDC. Capacity is currently 60 million lb/yr. As a result a virtual single source has led to some significant reported delays in PEN development programs. However, Amoco has plans for a plant expansion (Decatur, AL) to from 85-110 million lbs/yr. Larger market opportunities in fibers and packaging are more sensitive to supply security. Applications in the fiber market include tire cord (the largest) to replace rayon in high speed vehicles and industrial uses such as equipment belts and heavy-duty cables as a possible steel replacement. Much of this work is in the early developmental stage. The best opportunity for PEN is the packaging market due to its higher T_g and improved barrier properties. This puts PEN in a good position to replace glass and aluminum cans in applications which could not be captured by PET. Its higher temperature capabilities along with light weight and shatter resistance open up many food container possibilities. PEN's heat stability allows it to be used in the returnable/refillable beer bottle market. Improved barrier properties make PEN suitable for small 12 oz beverage containers where PET can not be used. However, packaging market penetration is very price dependent and in the year 2000 Kline & Co. estimates penetration of only 1.6 MM lbs @ a price of $3.25/lb, and 5 MM lbs @ $2.00/lb; in 2005 the volumes are projected to be 14 MM lbs @ $3.25/lb and 140 MM lbs @ $1.50/lb, respectively. Other larger estimates have also been made. The use of blends and copolymers with PET are being investigated to address the price issue. From a technical point of view this approach is straight forward but FDA approvals and resolution of recycling issues could be slowed down. Since most PEN companies are also major PET players any development strategy must consider the impact it may have on the PET business. (P. Morse, C&EN, Nov. 10, 1997, p.8)