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

MILLENNIUM ISSUE
Vol. 7, No. 3
PEL PLASTICS UPDATE
Jan.-Feb., 2000
By Mort Wallach
ISSN 1094-656X
 

Polymers and Plastics in the 21st Century-As we enter the new millennium a number of key issues and technical advances are on the horizon involving implementation of biotechnology, development of green processes and products, new material designs for the automotive industry, innovations targeted for the IT revolution, nanotechnology for applications in medicine, industry and defense, and E-commerce to enhance profitability and globalization.

1. Implementation of Biotechnology: Utilization of renewable resources and biotechnology to alleviate dependence on petrochemicals and natural gas-based systems will be a key activity, creating new monomers and polymers via bacterial fermentation and genetically engineered processes.

2. Development of Green Processes & Products: Design of cleaner manufacturing plants, new biodegradable polymers, use of supercritical polymerization media such as supercritical CO₂ are making headway and should continue.

3. New Material Designs for the Automotive Industry: Lighter/stronger composites, new modular designs, and class A finish materials, all of which will be recyclable will be a major goal in automotive.

4. Innovations Targeted for the IT Revolution: Development of polymer lasers, flexible thin film circuits for computers, polymers for smaller/denser faster chips, and quicker switches, improved displays (e.g., LEDs), and new and improved CMP for more complex circuit layering are among the areas enhancing the IT revolution, and should power the economy further.

5. Nanotechnology: Applications to stronger polymeric materials in composites and coatings, better packaging films, miniaturized electronic and photonic devices, and new biotech nanoadvances including dendrimers for gene therapy, in-vivo drug release, and enhanced prosthesis should be among many developments made possible via nanotechnology. We expect nanotechnology to be a leading area of important innovations in the new millennium.

6. Use of E-Commerce to Enhance Profitability and Globalization: Worldwide customer interface, rapid response, tailored products, lower inventory requirements, and lower costs are routes to polymer and plastics business success in the new century.

Nanocomposites-New nanocomposite fluoropolymer-silica coatings were prepared via the sol-gel process to yield glass adhering systems which have potential in antifouling, photolithog- raphic patterning, and protection from moisture. These coating systems could be applied to metal oxide surfaces (e.g., aluminum, iron, platinum) which heretofore have been difficult to coat with hydrophobic materials.

• A. Stiegman and coworkers at Florida State U. in Tallahassee have succeeded in coating fluoropolymers which are hydrophobic on to glass which is hydrophilic. Their method incorporates fluoropolymers into porous inorganic films made by the sol-gel process which can produce hard and porous xerogels. The glass adhering properties of silica and the catalytic features of vanadia were employed by spreading a film of sol onto a quartz surface and then topping the film with a thin layer of difluoroethylene liquid. The surface is bombarded with UV light causing the vanadia to polymerize the difluoroethylene in the pores of the xerogel from which polymer spreads out in a layer over the surface. This results in a polyvinylidene fluoride-silica nanocomposite coating which is very strong and has a surface energy close to pure polyvinylfluoride. This is a first demonstration of good adhesion of a fluoropolymer on ceramic oxide surface. Oxide coated aluminum, iron, platinum and other metals could presumably be so coated. Applications include enhanced parts for automotive, aerospace, marine and defense. (J. Phys. Chem. B, 103, 9383, 1999)

Smart/Functional Polymers-New dendritic polymers were developed which harvest light of varied wavelengths and efficiently convert the radiant energy to blue light leading to potential applications in optoelectronic devices such as molecular wires.

• Prof. T. Aida and coworkers at U. of Tokyo prepared rigid rods of poly(phenylethynylene) (PPE) conjugated backbone wrapped with a flexible poly(benzyl ether) dendritic envelope. The backbone collects visible light and the envelope collects photons of UV light and channels the energy to the backbone which then fluoresces blue. The quantum yield is high (i.e., photons converted to fluorescence) as is the energy transfer from the light-harvesting antennae of the dendritic envelope to the chromophore units. Fluorescence of the backbone is most intense when it is encapsulated by third generation dendritic wedges. Shielding by the dendritic wedges enhances the fluorescence unlike poly(phenyleneethynylene) without the wrapping which undergoes collisional quenching of the photoexcited state. The dendritic envelope prevents these collisions (i.e., "the envelope effect") moreso with each generation of dendritic wedges. The high efficiency and blue emission give more interest to this work. The PPE being very rigid is not very soluble and is difficult to process whereas the dendritic material is quite soluble in solvents such as THF at MWt of 250,000. Photo- and redox- functionality at backbone terminals are being investigated with the goal to prepare molecular wires. (J. Am. Chem. Soc., 121, 10658, 1999)

Catalysis-New robust Ni based catalysts which yield high molecular weight polyethylenes, function at low temperature and pressure, do not require a cocatalyst, can tolerate contaminants, and can polymerize olefins with functional groups.

• Prof. R. Grubbs and coworkers at Cal. Tech. have demonstrated these catalysts which are unlike metallocenes which require very clean conditions, and are susceptible to inactivation by organic functional groups and impurities (e.g., O₂ , N), and are unlike the Shell higher olefin process (SHOP) which primarily makes oligomers (4-20 units) and requires high temperatures and pressures. The Grubbs strategy starts with the SHOP catalyst replacing the phosphorous-oxygen ligand based species with one based on the more sterically bulky salicylaldimine. The Cal. Tech. team obtained polyethylene with MW=250,000, narrow molecular weight distribution, and very little branching. They also produced copolymers of ethylene and olefins functionalized with polar groups such as hydroxyl. This development builds on past work and is an advance in understanding transition-metal olefiin polymerization catalysis with meaningful industrial potential. (Science, 287, 460, 2000)

Alloys & Blends-Functional elastomeric approaches can enhance the performance of high impact polystyrene (HIPS) to make it an economical alternative to ABS. Atom transfer radical polymerization (ATRP) of end functional polystyrene (PS) can be melt processed to N6/PS blends with improved properties. Also, toughened poly(phenylene sulfide) (PPS) is being developed with applications targeted in electrical and automotive parts.

• Firestone Polymers has attached functional groups to rubber, to better adhere polybutadiene or styrene-butadiene in HIPS. This approach which had been used by Bridgestone/Firestone, to enhance rubber bondability to carbon black improving tire performance could also boost the performance of HIPS, making it an economical alternative to ABS and other resins. Target end-uses include packaging where functionalized rubber-based HIPS would offer better stress crack resistance and high clarity. Interest in functionalized rubber toughening technology is high among resin makers. (Modern Plastics, Oct., 1999, p. 14)

   

• E. Koulouri and coworkers at U. Patras in Patras, Greece and U. of Groningen, Netherlands synthesized terminal maleic anhydride functionalized polystyrenes using ATRP. Melt mixing of these reactive polystyrenes with nylon 6 resulted in blends with good mechanical properties attributed to an in situ formation of a copolymer which may be used for the compatibilization of the binary nylon 6/polystyrene blend. The mechanical properties of the resulting ternary blends were significantly improved with the addition of the modified polystyrene. The enhanced mechanical properties, as well as the fine PS dispersion in the nylon 6 matrix (revealed by SEM of the compatibilized cryofractured samples) support the hypothesis that an effective compatibilization of nylon 6/PS was achieved. (Macromolecules, 32, 6242, 1999)

   

• K. Kubo and coworkers at Asahi Chemical Industry in Kawasaki, Japan have made advances in toughening PPS. Chemical treatment was employed to activate the reactivity of the PPS end-group via extrusion in the presence of diphenylmethane diisocyanate (MDI). Reactive processing of the MDI-treated PPS with an olefinic elastomer containing a functional group such as carboxylic acid anhydride gave toughened PPS. The elastomer was finely dispersed in the matrix. Lamination of MDI-treated PPS sheet and the functional olefinic elastomer sheet exhibited strong adhesion. Viscoelastic properties and melt viscosity measurements suggest a strong interaction between the two sheets. Toughened PPS is used in electrical/electronic and automobile parts requiring high performance. (Kobunshi Ronbunshu, 56(7), 426, 1999)

Alloy & Blend Patents-Among 1500 patents reviewed during this period, there are several noteworthy inventions involving: polyolefin nanocomposites, paintable TPO compositions, and polyvinylidene fluoride blends with imide containing polymers.

• "Polyolefin Nanocomposites". M. Alexandre et. al. (Dow Chemical Co.) PCT Int. Appl. WO 99 47,598, Sept. 23, 1999. A nanocomposite is a dispersion of nanofiller particles derived from layered metal oxides or metal oxide salts. The nanocomposite is advantageously prepared by first swelling an untreated clay in water, then removing the water to form an organophilic clay that is dispersible in non-polar organic solvents. The organophilic clay can then be treated with an alkyl aluminoxane and subsequently a catalyst to form a complex that promotes olefin or styrenic polymerization and platelet dispersion. The nanocomposite can be prepared directly by in situ polymerization of olefin or styrene at the nanofiller particles without shear, without an ion exchange step, and without the need to incorporate polar substituents into polyolefin or polystyrene. (Chem. Abs. 131: 229867j)

   

• "Directly Paintable Thermoplastic Olefin Composition Containing Maleic Anhydride-Modified Polymers And Injection-Molded Articles Therefrom". D. Berta (Montell NA, Inc.) US 5,959,030, Sept. 28, 1999. Directly paintable polymer compositions contain (1) a thermoplastic olefin (TPO), (2) a maleic anhydride-grafted propylene homopolymer or random copolymer, (3) a maleic anhydride-grafted olefin polymer material, (4) a functionalized polymer that reacts with the maleic anhydride groups of the grafted polymers, and, optionally, (5) a maleic anhydride-grafted ethylene polymer. The amount of (2) + (3) or (2) + (3) + (5) is 16-27 parts/100 parts of the TPO. Thus, an injection molded disc comprising TPO 100, Exxelor VA 1803 (I) 5, Royaltuf 465A (II) 5, maleated polypropylene 10, Jeffamine XTJ 418 3, and antioxidant 0.2 part showed paint adhesion (paint removed with adhesive tape) 3%, and durability (paint removed with Tabor abrader, 1 lb load) after 25 cycles 10% and after 50 cycles 20%, compared with 0, 0, and 0, respectively, when the molding also contained 5 parts Ceramer 67; and 45, 28, and 44 respectively, for a molding containing 10 parts Dutral 4038 instead of I and II. (Chem. Abs. 131: 244127m)

   

• "Compatible Polyvinylidene Fluoride Blends With Polymers Containing Imide Moieties". S-C. Lin et. al. (Ausimont USA, Inc.) US 5,959,022, Sept. 28, 1999. A compatible blend of superior mechanical strength, hardness and abrasion or mar resistance comprises PVDF and a compatible organic polymer containing > 1 imide group (e.g., N- cyclohexyl maleimide-Me methacrylate copolymer). The alloy is prepared by dissolving, separately, the PVDF and polymer in a solvent and blending the solutions to provide the required composition. The alloy can also be prepared by dispersing PVDF powder in a solution of polymer containing imide groups. After heating and drying, a homogeneous alloy is formed. In addition, melt extrusion of PVDF with the imide-containing polymer also generates the desired PVDF alloy. (Chem. Abs. 131: 244126k)

New Plastics Ventures- Shell Petroleum and BASF are combining their polyolefin businesses to form one of the largest such operations worldwide. Cyclics Corp., a new company will produce polymer composites of polycarbonate, polyarylate, and PBT from low molecular weight cyclic oligomers which readily polymerize and possess good reinforcement wet-out. Applications include auto parts, bicycle frames, and bridges.

Shell Petroleum, part of the Royal Dutch Shell Group and BASF A.G. are joining their polyolefins businesses to form one of the largest polymer operations. Combined revenues are more than $6 billion. This venture would rank first in polypropylene and fourth in polyethylene worldwide. BASF and Shell plan to combine their Elenac, Montell, and Targor businesses. Elenac is the polyethylene alliance of the two companies headquartered in Strasbourg, France. Montell headquartered near Amsterdam is currently the world's leading producer of polypropylene. Targor based in Mainz, Germany, is a joint venture of BASF and Celanese who is looking to focus more on it's specialty business, and has agreed to sell it's 50% stake in the Targor polypropylene business to BASF for more than $260 million. Since Montell and Targor are among the leading polypropylene producers, antitrust issues may arise and industry observers suggest that the companies may have to divest capacity in Europe. Polyethylene is not considered a problem since Equistar, Dow, and Exxon have larger market shares. Shell and BASF would share ownership of the polyolefin operations which will be based in the Netherlands. (A. Thayer, C&EN, Nov. 8, 1999, p. 8)

Cyclics Corp., Schenectady, N.Y. (a new firm) purchased ~50 U.S. and foreign patents from General Electric Co. covering cylic compositions of polycarbonate, polyarylate, and PBT polyester. These low molecular weight oligomers readily process into high molecular weight thermoplastics. Since their initial viscosity is low, fiber reinforcement penetration is good for making thermoplastic composites. The technology combines the processability of a thermoset with the material properties of a thermoplastic. Cyclic PBT can be polymerized in seconds without exotherm so that parts can be demolded quickly without cooling. The company is setting up facilities near Albany, NY and experimental quantities of cyclic resins are expected in a few months. Potential composite applications include: auto parts, bicycle frames and bridges. (Plastics Technology, Sept., 1999, p. 29)