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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.
Vol. 8, No. 3
PEL PLASTICS UPDATE
September - October 2002
By Mort Wallach
RECENT PROGRESS IN POLYMER/PLASTICS TECHNOLOGY AND APPLICATIONS
Nanotechnology : Polyelectrolyte multi-layer research has seen significant progress including 1) processing metal or semiconductor nanoparticles into advanced materials, 2) nano-reactors for making silver nanoparticle composites, 3) fabrication of nano-engineered core/shell structures, and 4) suppression of corrosion on stainless steel in salt water. Potential applications involve photonic, electronic, sensing and controlled delivery systems. Also a new method of nano-pattern transfer was developed at IBM Almaden with possible applications in magnetic storage and advanced electronics, and a nanotech research institute was established at MIT in collaboration with the U.S. Army.
- Nicholas Kotov and coworkers at Oklahoma State University demonstrated a method to process dispersions of semiconductor, metal, or metal oxide nanoparticles into functionally advanced materials. This was achieved using layer-by-layer nanoparticle assembly by alternately dipping a substrate into a nanoparticle and polyelectrolyte solutions. The products retain the distinctive optical, magnetic, and electrical properties of the nanoparticles. In this way they showed how layer-by-layer assembly could be used to make semi-conducting films that emit light of different colors depending on the film composition. The films were prepared from CdTe nano- particles stabilized by thioglycolic acid with a partner polyelectrolyte poly(diallyl- dimethylammonium chloride). Physical features of such materials (polarizability, refractive index) can be engineered on a molecular level and can lead to new and unique photonic and electronic devices. (J. Am. Chem. Soc., 123, 7738, 2001)..
- Michael Rubner and his group at MIT have shown that polyelectrolyte multi-layered films of poly(acrylic acid) and poly (allyl amine hydrochloride) can be employed as nanoreactors for making silver nanoparticle composites. The size of the nanoparticles and the metal concentration within the films can be controlled by the solution pH and other processing conditions. Such control of silver content gives one the ability to systematically change the optical properties of these nanocomposite films. Methods have also been developed to pattern these films by ink-jet printing. Using water or polyelectrolyte solutions as the ink in a standard ink-jet printer created patterns with features on the order of 50-300 mm. (Langmuir, 18, 3370, 2002).
- Gleb Sukhorukov and coworkers at the Max Planck Institute employed polyelectrolyte multi-layers to fabricate nanoengineered core-shell structures. The permeability of the shells and release of encapsulated materials can be controlled and modified by pH, ionic strength, and various solvents. An example is the coating of fluorescent particles as model compounds for drug delivery. The coating was a layer by layer assembly of oppositely charged polyelectrolytes sodium poly (styrene sulfonate) and poly (allylamine hydrochloride) (J. Phys. Chem. B, 105, 2281, 2001)
- Finally, Joseph Schlenoff and coworkers at Florida State University showed that polyelectrolyte multilayers suppressed the corrosion of stainless steel immersed in saltwater. Thus one can envision practical applications as the internal coating of pipes. (Electrochem. Solid-State Lett., 5, B13, 2002)
A variety of potentially useful applications of polyelectrolyte monolayers include light-emitting devices, nonlinear optics, sensors, electrochromics, conductive coatings, and analytical separations.
- Kenneth Carter and coworkers at IBM Almaden have developed a new method of nanoscopic pattern transfer. The process - nanocontact molding - employs photopolymerized acrylate polymer networks as reusable stamps. The method starts with a high-resolution hard master pattern of SiO2 , Si or quartz. First the substrate is spin coated with photopolymer. The patterned master is aligned and pressed over the photo-polymer coating which is UV cured at desired temperature. The new master is then released and the pattern is finished by dry etching, metal deposition and stripping of the organic material. The polymer stamp is then used to imprint a second photo- polymerizable polymer layer on a receiving substrate such as silicon or glass. The process has several advantages over known contact patterning methods including: 1) the polymers are easy to make and inexpensive, 2) the crosslinked photopolymers have a high enough modulus to allow for high resolution, 3) pattern replication can be done over a large area, 4) the photopolymers are UV transparent allowing for subse- quent processes requiring transfer and UV exposure. The photopolymer formulation used here consists of N-vinyl pyrrolidinone (18.5%), trimethylolpropane trimethacryl- ate (18.5%), ethoxylated bisphenol A dimethacrylate (61 %) and dimethyloxy-2-phenylacetophenone as initiator (2%). (Polymer Preprints, April 2002, p. 403)
- The Institute of Nanotechnologies (ISN) was created at MIT via a U.S. Army $50 million award. The institute will consist of 150 people including 35 MIT professors, in the Schools of Engineering, Science, and Architecture & Planning. Industry partners DuPont and Raytheon will provide another $40 million for facilities and equipment. Using nanoscience, researchers will focus on six key military capabilities including threat reduction and neutralization, concealment, enhanced human performance, real-time automated medical treatment, and weight load reduction. These topics will be addressed by research teams directed towards energy absorbing materials, mechanically active materials, detection and signature management, biomaterials and nanodevices for medical technology, process systems for manufacture and processing of materials, modeling and simulation, and systems integration. Industry researchers will also participate along with army specialists, and physicians from Mass. General, and Brigham and Women’s Hospital.(L. Schulz, C&EN, March 25, 2002, p. 12)
Alloys & Blends: New high performance microcellular foamsof polysulfone/ polybenzimidazole blends were developed by first sulfonating the polysulfone to enhance compatibility, and then preparing the foams by CO2-saturation of films under pressure, then heating the films in an oil bath.
- F. Arnold at Wright Patterson AFB, J. Mark at U. of Cinn., M. Hountz at U. of Dayton Res. Inst and coworkers developed a high temperature composite of sulfonated polysulfone (PSF) and polybenzimidazole (PBI) to create the high performance microcellular foams. Sulfonation significantly enhanced the compatibility. The PBI was well dispersed in the nanoscale range in the matrix of modified PSF. The Tg and thermal stability of the PSF was significantly increased by the addition of compatibilized PBI and microcellular foams were fabricated from the modified PSF/PBI composite. Applications include demanding aerospace material functions. (Polymer Preprints, April 2002, p. 471)
Selected Patents: Among 1000 patents reviewed during this period, there are several noteworthy inventions involving: porous polyimide circuit substrates, prepregs of liquid crystal polyarylate fibers & laminates, new fluoropolymer blends in photoresist compositions for DUV microlithography, and paintable polypropylene graft copolymer compositions.
- "Producing Porous Polyimide For Circuit Substrate" M. Kanada et al (Nitto Denko Corp.) US 6,372,808, April 16, 2002. A porous polyimide has a fine cellular structure and a low dielectric constant and good heat resistance. The porous polyimide can be produced by adding a dispersible compound to a polyimide precursor to form a micro-domain structure in which the dispersible compound is dispersed in the polymer to have a size <10mm and then removing the dispersible compound by extrusion with supercritical CO2 to make the precursor porous, where the interaction parameter cAB between the polyimide precursor A and the dispersible compound B>3. This porous polyimide has an average cell diameter <5mm and a dielectric constant < 3. (Chem. Abs. 136: 310919c)
- "Prepregs Containing Liquid-Crystalline Polyarylate Fibers And Their Laminates" T. Sugimura et al (Hitachi Chemical Co.) JP 2002 146,060 May 22, 2002. The prepregs comprise base materials comprising liquid crystal polyarylate fibers and matrixes containing cyanate resins, monohydric phenols, and polyphenylene ethers. The laminates are useful for printed circuit boards. Then, Verucus 50 (liquid crystal hydroxybenzoic acid-6-hydroxy-2-naphthoic acid copolymer nonwoven fabric) was impregnated with a varnish containing Epikote 1001 and dicyandiamide, dried, impregnated with a solution containing a reaction product of PCP [p-(a-cumyl)phenol] with Arocy B 10 [2,2-bis(4-cyanatophenyl)-propane] homopolymer and Noryl PKN 4652 [poly(2,6-dimethyl-1,4-phenylene) ether], and dried to give a prepreg, five sheets of which were hot-pressed to give a laminate showing dielectric constant 2.77, dielectric loss tangent 4.2, and suitability for drilling.(Chem. Abs. 136: 387106t)
- "Polymer Blends And Their Use In Photoresist Compositions For Microlithography" L. Berger et al (DuPont Co.) PCT Int. Appl. WO 02 44,811 June 6, 2002. The present invention relates to a photoresist composition having (1) at least two polymers selected from the group consisting of: (a) a fluorine containing copolymer comprising a repeat unit derived from at least one ethylenically unsaturated compound characterized in that at least one ethylenically unsaturated compound is polycyclic; (b) a branched polymer containing protected acid groups, said polymer comprising one or more branch segments chemically linked along a linear backbone segment; (c) fluoropolymers having at least one fluoroalkyl group having the structure: -C(Rf)(Rf ¢)OH (Rf, Rf ¢ = C1-10 fluoroalkyl groups or taken together are (CF2)n, n = 2-10; (d) amorphous vinyl homopolymers of perfluoro(2,2- dimethyl-1,3-dioxole) or CX2 = CY2 (X = F or CF3 and Y = H) or amorphous vinyl copolymers of perfluoro(2,2-dimethyl-1,3-dioxole) and CX2 = CY2 ; and (e) nitrile/fluoroalkyl-containing polymers prepared from substituted or unsubstituted vinyl ethers; and (2) at least one photoactive component. The present invention provides blends of polymer composition having high UV transparency at short wave lengths, e.g., 157 nm, which are useful as base resin for photoresist and the production of semiconductor devices. (Chem. Abs. 137: 13266p)
- "Directly Paintable Polypropylene Graft Copolymer Composition". D. Berta (Basell Technology Co.) PCT Int. Appl. WO 02 31,052 April 18, 2002. A directly paintable polyolefin composition contains (1) a graft copolymer composition containing (a) a graft copolymer having a backbone of propylene polymer material having graft polymerized thereto at least one radically polymerizable vinyl monomer, (b) a rubber component, and, optionally, (c) an oxidized polyethylene wax, (3) a propylene homopolymer or copolymer grafted with an anhydride of an aliphatic a,b- unsaturated dicarboxylic acid, (4) a functionalized polymer that is reactive with the anhydride groups of the grafted polymers, and, optionally, (5) a polyolefin rubber grafted with an anhydride of an aliphatic a,b-unsaturated dicarboxylic acid, and (6) an ethylene polymer grafted with an anhydride of an aliphatic a,b-unsaturated dicarboxylic acid. The compositions are particularly useful for making injection molded automobile parts and exhibit excellent paint adhesion and durability.(Chem. Abs. 136:310697d)
Polymeric Coatings/Auto Glazing: New plasma deposition coatings on polycarbonate substrates being developed by the Bayer/GE joint venture exhibit improved abrasion resistance to almost targeted glass levels. Lower cost processes (dip, flow or spin) at TWI in England are not quite up to the low haze required on repeat abrasion cycles, however some coatings have reportedly passed vehicle field tests.
- Current Bayer/GE prototype coatings being developed at Exatec in Wixom, MI employ a UV absorbing interlayer via a wet process, and a plasma applied abrasion resistant silicone topcoat. Taber abrasion resistance is near that of glass (about 1% haze increase) and weatherability is the best among coatings under development. Generally the target is U.S. safety standard FMVSS which specifies a haze increase of <2% after 1000 abrasion cycles for glazing ahead of the B-pillar. A production scale plasma coating line is due out in Feb. 2003 with a capability to reduce coating costs well below those of current plasma enhanced chemical vapor deposition processes. The wet processed UV absorbing layer could be substituted by an inorganic coating applied in-line using plasma deposition.
- Meanwhile TWI in Cambridge, England is developing a UV cured poly- carbonate auto glazing coating (Vitresyn) which gives a haze increase after 1000 Taber cycles of 3-4% without need for a primer. It is applied by standard dip, flow, or spin processes. UV curing occurs at room temperature and costs about the same as commercial coatings. TWI uses interpenetrating networks that employ ceramic loadings. Some of their coatings have passed vehicle field tests and they are seeking partners to help commercialize their technology. (P. Mapleston, Modern Plastics, April 2002, p. 47)
Specialty Polymers/PVC: Recent technical advances in poly(vinyl chloride) have resulted in innovative PVC materials for a variety of markets including automotive, medical, and wire & cable applications. Future potential innovations are based on tailoring the molecular architecture of PVC, novel reactive processing, and ordered polymer technology.
- Flexible vinyl with worldwide volume currently at 20 billion pounds per year is expanding at rates of 2-3 % per year in the U.S. and Europe and higher rates in Asia. This has occurred in spite of environmental issues and efforts to replace vinyl with specialty polymers and TPE’s. Recent technical advances in PVC for automotive, medical, wire and cable and other consumer and industrial applications, include ultra high molecular weight PVC, low-flame/low smoke cable compounds, blends of PVC with non-compatible polymers via compatibilizers, and use of new heat stabilizers. (R. Brookman, Plastics Engineering, June 2002, p. 14)
New Polymer Ventures: Dow Corning will acquire Multibase a French thermoplastics compounder serving packaging, automotive and appliance markets. This will allow Dow Corning to expand beyond silicon-based products. Production sites are in France, India and the United States. Multibase products include various TPE and thermoplastic compounds based mostly on polyolefins. They are a licensed compounder of Kraton SBS copolymers and also make mineral filled master batches of polyolefins. Dow Corning produces thermoset silicone elastomers, high molecular weight siloxane additives, and a new line of silicone-based TPE’s. The combined product line will be sold under the
Multibase brand which is strong in TPE for airbag doors, acoustical products, and PP compounding for automotive. This acquisition may also benefit Dow Chemical which is co-owner of Dow Corning (along with Corning, Inc) since there is speculation that Dow Chemical may enter the SEBS market. (Modern Plastics, May 2002, p. 14)
Dr. Mort Wallach has over twenty-five years experience in the plastics industry beginning at DuPont's Experimental Station, and ranging from resin, film, and plastic manufacture, to consumer products, transportation and aerospace. His contributions include twenty-four publications, four recent books, numerous patents, and key roles in commercial developments, such as Kapton polyimide film, high performance composites, novel consumer products, and engineered materials. Presently, he is President of PEL Associates, a successful product development and consulting firm in polymer/plastics science and technology. He is a member of ACS, SPE, IUPAC, and Sigma Xi. Dr. Wallach is affiliated with: Teltech Network of Experts, The CT Technology Council, Univ. of Connecticut, The Fulbright Association, and The Licensing Executives Society.
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PEL PLASTICS UPDATE highlights recent progress in key areas of polymer/plastics technology and applications including: catalysis, biopolymers, smart/functional polymers, alloys & blends, nanotechnology, polymer modification and new ventures. These citations are selected from a review of over 1000 articles in 100 journals, over 1000 US and foreign patents, and key conferences worldwide.
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