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. 6, No. 4
PEL PLASTICS UPDATE
Sept.-Oct., 1998
By Mort Wallach
ISSN 1094-656X
 

Nanocomposites-Current NIST and EPIC consortium programs focus on barrier properties, FR, and automotive applications with polymers such as nylon, PP, PS, silicones, and epoxy. Meanwhile, specialized developments include polymer nanotube composites which have promise in optoelectronics.

• Recent Edison Polymer Corp. (EPIC) nanocomposite consortium activity of about a dozen companies and Universities involves improved barrier properties, use of nanocomposites in nylon containing fuel tanks, coatings for surface protection, (e.g., scratch resistance), elastomer modification, use of nanocomposites to replace carbon black in TPEs, and new nanocomposite compounding technology. NIST reports that clay nanoparticles offer 60-80% flame retardance improvement when used at only 2-5% loadings. This is true for both exfoliated and intercalated classes of nanoparticles. Promising FR results have been obtained in nylon, PP, PS, and epoxy thermosets. Present knowledge suggests that only molecular scale dispersion of particles improves FR performance. A dozen companies involved with NIST (including clay and resin suppliers, and OEMs) are interested in the mechanism and applications of this phenomenon. NIST is also working with the U.S. Air Force on silicone nanoparticles where a number of uses have been uncovered. Meanwhile, Dow Plastics is supporting investigations of mineral composites in automotive applications. (Modern Plastics, Oct. 1998, p. 12)

   

• A. Curran and W. Blau at Trinity College in Dublin, Ireland have developed polymer nanotube composites with promise in optoelectronics and other applications. Specifically they disperse small amounts of multiwalled carbon nanotubes in a conjugated light emitting polymer-poly (m-phenylenevinylene-co-2,5-dioctoxy-p-phenylene vinylene). The polymer chains form coils which wrap around the nanotubes giving a stable composite with large increases in polymer conductivity by as much as eight orders of magnitude. At low enough concentrations of nanotube the polymer luminescent properties are not appreciably deminished. Also, the nanotube acts as a heat sink preventing heat build-up by the polymer on laser illumination. A thin film of the composite is used as the emissive layer in a light emitting diode. Since the nanotubes increase the conductivity and mobility of charge carriers in the composite, luminescence occurs at lower current densities than the polymer alone. Commercial possibilities are being pursued. (Adv. Mater., 10, 1091, 1998)

Catalysis-Cyclopentene addition polymerization with nickel and palladium catalysts yields melt processable, high melting polymers with physical properties unlike any previously reported for polycyclopentene. Also, certain Zn catalysts with sterically bulky ligands readily convert CO₂ and epoxides to biodegradable aliphatic polycarbonates with potential as packaging films and biomedical sutures.

• S. McLain of DuPont and M. Brookhart of U. of North Carolina and coworkers found that -diimine complexes of Ni and Pd catalyze the addition polymerization of cyclopentene. The polymers are melt processable with melting points (high end) ranging from 241 to 330C. They range in tacticity from atactic to moderately isotactic. The polymers have a new crystalline form as demonstrated by x-ray diffraction patterns which differ from highly isotactic polymer previously reported. (Macromolecules, 31, 6705, 1998)

   

• Prof. G. Coates and coworkers at Cornell have shown that certain -diamine Zn based catalysts readily convert CO₂ and epoxides to aliphatic polycarbonates. These polymers are biodegradable and are potentially useful as packaging films and biomedical sutures. Relatively good reaction rates and narrow molecular weight distributions were obtained. The new Zn catalysis has opened up the possibility of developing systems for use with other epoxide monomers and for controlling polymer stereochemistry. The key to this discovery was the observation that sterically bulky ligands were needed to make effective zinc catalysts. (J. Am. Chem. Soc., 120, 11018, 1998)

Smart/Functional Polymers-Combinatorial routes to photorefractive resins facilitates the more rapid preparation of these important polymeric materials which are potentially useful in data storage and optical processing.

• Profs. J. Siegel and W. Moerner and coworkers at U. Cal., San Diego have demonstrated that the two units required for photorefractivity, i.e., the charge transfer agent (CTA) and the nonlinear optical (NLO) chromophore can readily be grafted to a siloxane polymer backbone. As a result the one-pot reaction of poly(hydromethyl)siloxane with a well known CTA and the precursor to a widely used NLO chromophore-followed by conversion of the precursor-yielded a library of bifunctional polymers which vary in the relative proportions of CTA and NLO units. When doped with 1% of the charge generator some of the library members become photorefractive. This technique makes it possible to rapidly prepare candidates for photorefractive screening. (J. Am. Chem. Soc., 120, 9680, 1998)

Alloys & Blends-Compatibilization technology involving nylon 6 upgrading of a polypropylene/olefinic rubber TPV yields triblend dynamic vulcanizates with improved higher temperature performance.

• K. Venkataswamy of Advanced Elastomer Systems in Akron has developed these novel thermoplastic vulcanizates (TPVs) based on a compatibilized plastic phase. The starting point involves TPVs based on polypropylene and an olefinic rubber such as EPDM, butyl rubber, or brominated p-methyl styrene-isobutylene copolymer which results in thermoplastic elastomers with a useful range of properties. In this work PP-MA technology to compatibilize the polypropylene plastic phase with engineering thermoplastics such as polyamide 6 is shown to result in triblend dynamic vulcanizates with further improvements in functional performance at elevated temperatures. Effect of compatibilizer level and type, and olefinic rubber type were investigated. (PMSE, 79, 94, 1998)

Alloy & Blend Patents-Among 1000 patents reviewed during this period, there are several noteworthy inventions involving: novel ionomer/polyamide blends with improved impact resistance, mixed catalysts for isotactic/syndiotactic olefin blend production, transparent polysilox- ane/polycarbonate flame retardant compositions for computers and business equipment, and impact-modified thin wall olefinic polymer compositions for cups, lids, and food containers.

• "Ionomers Based On Copolymers Of Ethylene With Both Mono- And Dicarboxylic Acids And Polyamide Blends Containing These Ionomers". R. Chou (E.I. DuPont de Nemours and Co.) PCT Int. Appl. WO 98 38,227, Sept. 3, 1998. Ethylene-acid copolymer ionomers which contain both (meth)acrylic acid and certain dicarboxylic acid monomers are described. The polymers may be melt processed as readily as ethylene-(meth)acrylic acid terpolymer ionomers, in contrast to ethylene/acid copolymer ionomers containing only dicarboxylic acid-monomer-derived in-chain units. Polymers with typical levels of (meth)acrylic acid and low levels of diacid provide ionomers comparable to existing ionomers, but which have adhesive and polymer blend compatibilizing characteristics, while polymers with higher levels of diacid will exhibit properties which depend on in-chain diacid units. These ionomers are useful as impact improvers for polyamides. (Chem Abs. 129: 217395z)

   

• "Catalyst System For Producing Isotactic/Syndiotactic Olefin Polymer Blends In A Single Reactor". B. Reddy et. al. (Fina Technology, Inc.) US 5,804,524, Sept. 8, 1998. The invention is a catalyst system to produce polymer blends comprising isotactic and syndiotactic polyolefins in a single reactor. The catalyst system is a combination of at least one metallocene catalyst and at least one conventional supported Ziegler-Natta catalyst. The multi-catalyst system is obtained by mixing the components of at least one metallocene catalyst and at least one conventional supported Ziegler-Natta catalyst. The metallocene catalyst comprises a solid complex of a metallocene compound and an ionizing agent. The conventional supported Ziegler-Natta catalyst comprises an aluminum alkyl and a transition metal compound with optionally, an electron donor. (Chem. Abs. 129: 217018d)

   

• "Polysiloxane Flame Retardant And Fire-Resistant Aromatic Polymer Composition Thereof". G. Davis et. al. (General Electric Co.) Eur. Pat. Appl. EP 863,185, Sept. 9, 1998. The transparent polymer composition, useful for moldings such as computers and business equipment, comprises (a) an aromatic-based polymer (such as polycarbonates) and (b) a fireproofing agent containing a copolymer of an aryl-containing silicone compound. Thus, 10 parts polysiloxane prepared from trimethylsilyl-terminated octamethylcyclotetra-siloxane-cyclic tetramethyltetravinyltetrasiloxane copolymer and triphenylsilane was blended with 990 parts bisphenol A-based polycarbonate powder, and injection molded to give a test piece showing good transparency and fire resistance. (Chem. Abs. 129: 231544d)

   

• "Impact-Modified Thinwall Polymer Compositions, Molded Products Therefrom, And Their Manufacture". A. Whetten et. al. (Dow Chemical Co.) US 5,804,660, Sept. 8, 1998. Modified polymer compositions having good flowability, impact performance, and modulus comprise 75-99% of > 1 polyolefin (high density polyethylene, medium density polyethylene, LLDPE, or polypropylene) with specified density and processing properties blended with 1-25% of > 1 homogeneous linear ethylene--olefin copolymer with a single m.p., density 0.85-0.91 g/cm³, and a short term branching distribution index > 50%. The compositions are suitable for thermoformed or molded thinwall applications such as drinking cups, lids, and food containers where the flow length to wall thickness ratios are > 180:1. (Chem. Abs. 129: 217353j)

High Performance Polymers/Polyimides-Improved gas separation of polyimide membranes is achieved via an ultrathin, defect free skin layer. Also, functional polyimides with pendant amino and cyano groups were prepared with high Tg and good thermal stability. This opens the possibility for polyimide upgrading of various polymers (e.g., PP-MA, SEBS-MA) via pendant group reaction.

• H. Kawakami and coworkers at Tokyo Metropolitan U. have prepared these asymmetric polyimide membranes by a wet/dry phase inversion process. They demonstrated the formation of an ultrathin skin layer with spongelike structure characterized by the presence of macrovoids. The gas selectivity of the membrane increases with a decrease in the thickness of the skin layer. The effect of the membrane surface skin layer on gas permeability and selectivity is discussed further. (Macromolecules, 31, 6636, 1998)

   

• I. Chung and S. Kim at the Korea Adv. Inst. of Sci. & Tech. in Taejon have converted heterocyclic diamine monomers with amino and cyano functional groups [i.e.,1,3-bis(p-amino-phenyl)-4-cyano-5-aminopyrazole] to new high molecular weight polyimides employing various dianhydrides, e.g., PMDA, BTDA, and ODPA. The polymers have high T_g and good thermal stability with no degradation or cross-linking up to 500C. The presence of such reactive functional groups could provide routes to polyimide upgrading of various polymers. (Macromolecules, 31, 5920, 1998)

New Ventures & Alliances-The Royal Dutch Shell Group plans to sell 40% of it's chemical business interests including epoxy, PVC, PK, PET, PEN, PS, PP, PU foams, resins and elastomers. Dow Chemical is rumored to be keenly interested in many of these. Meanwhile Dow Plastics has formed an alliance with Solutia to produce and market nylon 6,6 for molded applications under the current Vydyne trade name.

• The Royal Dutch Shell Group plans to make major cuts in its petroleum and petrochemical businesses. A total of 40% of its chemical interests are up for sale including a 50% interest in PP manufacturer Montell. Shell has the largest worldwide chemical operations of any oil company and is the sixth largest global chemical producer. Of 172 billion dollars in annual revenues in 1997 it had 14.3 billion in chemical sales. Shell chose to revamp now because the company expects that over the next five years oil prices will remain low and chemical profit margins will continue to erode with global economic growth no higher than 2% annually. Up for bid are bisphenol A/epichlorohydrin and seven polymer businesses including: PVC, Carilon aliphatic polyketone, PET, (including PEN), PS, PU foams, resins and elastomers. Shell will keep mostly basic and intermediate chemical businesses and will also maintain two polymer interests: the Elenac polyethylene joint venture with BASF, and the PP joint venture involving Montell. Also, Shell will continue to be involved with catalyst and lub additive businesses. Dow Chemical is rumored to be a perfect possible buyer of many of these businesses with a particular interest in Montell from whom it already licenses PP technology and purchases PP resin to sell under it's Dow name. Also, it is known that Dow intends to be one of the top global PP suppliers. (P. Layman and M. Reisch, C&EN, Dec. 21, 1998, p. 6)

   

• Solutia and Dow Plastics formed a global alliance to produce and market nylon 6,6 for molded engineering plastics applications in automotive, telecommunications, electronics, and appliance industries. The alliance is positioned to the injection molding market totaling 2.7 billion lb per year with annual growth of 10%. This gives Solutia access to Dow's expertise in product development and marketing while Dow gains the ability to market nylon 6,6 products. This is a win-win deal helping Solutia who lagged behind competition in developing new applications, and Dow which fills a big gap in its engineering plastics portfolio. Solutia will lead materials development R & D and will continue production of nylon 6,6 at its 300 million lb per year facility at Pensacola, Florida. Increased capacity of 60 million lb per year for the next two years is planned. The Solutia nylon sales force will be folded into Dow's marketing organization who will sell the product under Solutia's Vydyne trademark. (C&EN, Sept. 28, 1998, p. 13)