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.

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COMPLIMENTARY COPY                      
Vol. 8, No. 4 
Jan-Feb., 2004
ISSN 1094-656X                                   PEL PLASTICS UPDATE

Nanotechnology-The great potential of nanotechnology is shown again in these recent advances. Novel single wall nanotube-functional polymer-wrapped composites have potential applications in electronic devices such as actuators and switches. Unique photochemical reactions tailoring refractive index by UV excitation of absorbing chromophores have applications in optical waveguides, optical data storage elements and interference filter nanoarray with UV tuned reflectivity. Very strong nanotube fibers obtained via a novel spinning process of intermediate SWNT-PVOH gel fibers have possible applications in safety harnesses, and cargo explosion protection blankets, as well as conducting sensors, electronic interconnects and shielding.

• J. Fraser Stoddart and coworkers at UCLA have developed a variety of polymers and their interactions with SWNTs which provide a means to change the physical properties of nanotubes and the possibility of functionalizing them. Polymeric pseudorotaxane was synthesized based on two different recognition motifs: (1) one involving hydrogen bonding interactions and (2) another involving p -p stacking. Wrapping these functionalized polymers around SWNTs results in the grafting of pseudorotaxanes along the walls of SWNTs in a periodic fashion. This preserves the unique features of the nanotubes while at the same time tailoring their properties in a controlled manner. Creation of polymer-nanotube composites holds promise for reinforcing the polymers and extending their applications to electronic device systems. (Macromolecules, 36(3), 553, 2003).

• Eric Baer and coworkers at Case Western U. have demonstrated novel polymer systems in which the refractive index can be controlled by UV excitation of absorbing chromophores thereby initiating photochemical reactions. Such materials are of interest for applications such as optical waveguides, optical data storage elements, and optical interference filters. In this work one of two alternating layers in an interference filter multilayer nanoarray is made photoreactive while keeping the other polymer layer unchanged. On exposure to high energy UV light the refractive index of the layers with photoreactive polymer blend can be selectively changed and thereby the reflectivity of the ensemble becomes tunable. On exposure to UV in a spatially resolved manner optical patterning can then be achieved. Specifically homogeneous blends of PMMA and CA (trans cinnamic acid) which photodimerizes to create photoreactive blends can readily be produced to 20% CA which has a plasticizing effects on PMMA and the T_g of the blends varies inversely with the CA content. These blends can be employed in the preparation of multilayer films which display interesting optical interference effects. Also, due to the photoreactive nature of the CA additive, these materials are photopatternable. This effect can be exploited in a variety of applications ranging from security features to optical storage systems. (Polymer Preprints, 44(2), 883, 2003).
   
• Prof. R. Baughman and coworkers at U. Texas Dallas and Trinity College Dublin employ single wall nanotubes made from carbon monoxide and a surfactant (lithium dodecyl sulfate) in a coagulation-based spinning process. The process produces nanotube-PVOH gel fibers which are converted to 100 meter long nanotube composite fibers about 50 m m in diameter. Strength tests show that this nanotube product can be drawn into fibers that exhibit twice the stiffness and strength and twenty times the toughness (ability to absorb mechanical energy) of steel wire of the same weight and length. Fiber toughness is more than four times that of spider silk and 17 times that of Kevlar fibers used in bullet proof vests. Even double the fiber strength and further increases in toughness have since been obtained. Analogous to spider silk toughness mechanism (i.e., relatively stretchable amorphous regions between rigid crystalline protein blocks) this materials toughness may be related to it’s patches of amorphous polyvinyl alcohol located between single-walled carbon nanotubes. Applications proposed include: safety harnesses, and explosion proof blankets for aircraft cargo areas. The combination of good electronic and mechanical properties suggest textile applications in sensors, electronic interconnects, and electromagnetic shielding. At present the process is being run on a laboratory scale making hundreds of meters of fiber per run while the process is amenable to scale-up. However the cost of preparing single-walled carbon nanotubes is still high.
  (Nature, 423, 703, 2003)

Plastics for Electronics/Organic Electronic Systems-A novel non-lithographic thermal transfer process is introduced (by DuPont et al) that enables printing multiple successive layers via a dry additive process. The method can pattern a range of organic materials at high speed over large areas (such as newspapers) with micron size resolution and excellent chemical performance. This dry potentially reel to reel printing method may provide a practical route to the expected benefits of plastics for electronics.

• G. Blanchet and coworkers at DuPont working with U. of Illinois, Lucent Technologies and U. of Texas illustrated the viability of thermal imaging and imageable conductors by printing a 20 inch diagonal TFT backplane that is thin, of ultra low weight, and flexible. TFTs with 20m m source and drain lines and 20m m channel length isolated from the gates by a thin dielectric were printed in registry at a throughput of 1000 cm²/min. Thermal printing thus occurs by transferring solid films, so that the need for solvents, masking, or photolithography is eliminated. (Polymer Preprints, 44(2), 306, 2003).

Self-Reinforcing Thermoplastic-Under development by Mississippi Polymer Technologies (MPT) Paramax SRP high performance rigid rod polymer is said to be the hardest, strongest, stiffest, most FR, highest in refractive index and lowest in CTE of any known polymer. It can be molded extruded and cast from solution and produces clear alloys with other engineering thermoplastics. Market potential includes military equipment, jet engines, missile housings, electronics, chemical processing, oil field components, and foam cores for sandwich panels.

• Pilot quantities are currently available and by later in 2004 million lb/yr amounts will be produced by MPT. Pricing is expected to be $30-35/lb and long range down to $6-8/lb. Interest to date has been by DOD for applications such as missile parts, launch tubes for shoulder fired weapons, jet engines, and structural composites for naval vessels. The polymer is a highly aromatic resin derived from chlorobenzene. The structure is based on a string of substituted and unsubstituted benzene rings producing a highly rigid chain structure. Paramax is completely amorphous and transparent, and isotropic producing homogeneous molded parts. It lends itself to solvent and melt processing into films and shapes unlike other rigid rod polymers such as PBI, and PBO, and polymers such as polyimides. The polymer is soluble in common solvents and can be cast into films and coatings. It can also be made into pellets and powders for compression molding and extrusion. However, current grades have very high viscosity making injection molding difficult. Extruded stock shapes can be machined with standard equipment. Paramax is very miscible with polycarbonate and polysulfone. Clear films have been cast with these blends and with polyimides. These resins are two to four times stiffer and two to three times stronger than any other thermoplastic. Surface hardness is also greater providing excellent scratch and wear resistance. Coefficient of friction is very low and compressive strength is more than 100,000 psi suggesting possible applications in ball bearings. Glass transition temperature is 165C and versions have been made with T_g up to 270C whereas the material does not lose strength at cryogenic temperatures (e.g., liquid nitrogen). Impact strength is reportedly better than other high performance polymers (such as PEEK or Ultem) while it is quite ductile relative to other fiber reinforced polymers. Paramax has a yellow tint like other aromatic polymers. It’s refractive index is very high and ultimately could be used in very thin eyeglass lenses. The inherent flame resistance is so good that on holding it up to an acetylene torch for 15 minutes it only chars and never smokes. (M. Naitove, Plastics Technology, 49(7), July, 2003, p. 34).

Selected Patents-Among 1000 patents reviewed during this period, there are several noteworthy inventions involving: polymer composites with functionalized carbon nanotubes, multilayer films with controlled light reflectivity, solid polymer fuel cell membrane compositions, and production of conductive, transparent, polymer/carbon nanotube composites.

• "A Polymer Composite Containing Chemically Bound Functionalized Carbon Nanotubes". C. Niu et al (Hyperion Catalysis Int.) PCT Int. Appl. WO 03 38,837, May 8, 2003. A composite comprises a polymerized mixture of functionalized carbon nanotubes and a monomer which can react with the functionalized nanotubes. A polymer composite comprising functionalized carbon nanotubes and polymer chains chemically bound to reactive sites on the nanotubes is produced by (a) dispersing the functionalized carbon nanotubes in a liquid medium, (b) adding a selected monomer capable of reacting with sites on the functionalized nanotubes, and (c) polymerizing the monomer and reacting with the functionalized nanotubes to form the composite. The carbon nanotubes are functionalized by reacting with oxidizing agents or by physical adsorption. The reacted surface carbons of the nanotubes can be further functionalized with chemical moieties that react with the surface carbons and selected monomers. The composite may consist of some polymer chains embedded in the composite with out attachment to the nanotubes. The resulting composite yields superior chemical, physical and electrical properties compared to mechanically mixed polymer composites that do not contain chemically bound carbon nanotubes. Thus, carbon nanotubes were carboxylic acid-functionalized by reacting with nitric acid at elevated temperatures. A composite was produced by mixing the functionalized carbon nanotubes with e -caprolactam, and polymerizing the mixture in the presence of H₃PO₄ by heating at 180° for 30 minutes, followed by heating at 260° for 30 minutes. (Chem. Abs. 138: 354784a)
   
• "Process And Apparatus For Manufacture Of Multilayer Films With Controlled Light Reflectivity Or Transmittance" Y. Nakanishi (Teijin-DuPont Film, Inc., Japan) Jpn. Kokai Tokkyo Koho JP 2003 112,355, Apr. 15, 2003. In Manufacture of the films consisting of > 11 alternately laminated resins A and B layers by melting A and B separately in an extruder, forming branches of the respective resin through pores of a multilayer feed block, introducing them to flat paths comparted by parallel plates so as to flow the branched resins in > 11 layers alternately, further introducing them to a junction in the feed block, extruding them into a sheet in layers in the thickness direction through a die connected to the junction, cooling and solidifying on a cast drum into a film, and stretching the film in at least one direction, the thickness of A and B layers is adjusted to 0.01-0.5 m m by controlling temperature distribution is also claimed. Thus a multilayer sheet consisting of 30 layers of PEN containing 0.11% spherical SiO₂ and 31 layers of a 50:50 PEN/PET blend prepated through the multilayer feedblock was stretched biaxially and heat-set to give a film showing selective light reflectivity in a wide wavelength range. (Chem. Abs. 138: 288792y).
   
• "Solid Polymer Membrane Compositions For Direct Methanol Fuel Cell" E. Howard (E.I. du Pont de Nemours and Co.) PCT Int. Appl. WO 03 34,529, Apr. 24, 2003. The present invention provides for a solid polymer electrolyte membrane having a fluorinated ionomer having imbibed therein a nonfluorinated, non-ionomeric polymer, wherein the fluorinated ionomer comprises at least 6 mol% of monomer units having a fluorinated pendant group, with a terminal ionic group, and wherein the non-ionomeric polymer is selected from the group consisting of a polyamine, a polyvinyl amine, and derivatives thereof. The invention also provides a catalyst coated membrane and a fuel cell having this solid polymer electrolyte membrane. (Chem. Abs. 138: 324117t).

• "Production of Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites". J. Connell et al (NASA) PCT Int. Appl. WO 03 40,026, May 15, 2003. A method of dispersing carbon nanotubes in a polymer matrix to produce a polymer/carbon nanotube nanocomposite comprises (a) dispersing carbon nanotubes in an organic solvent, (b) adding one or more monomers of the polymer to the dispersed nanotubes, and (c) polymerizing the monomers in the presence of the dispersed nanotubes under mechanical stirring. The nanocomposites exhibit a unique combination of properties, such as high retention of optical transparency in the visible range (400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties, such as vacuum UV radiation resistance, atomic oxygen resistance, high glass transition temperature, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings, films, foams, fibers, threads, adhesives and prepregs. Thus a polyimide-based nanocomposite comprising 0.1% of carbon nanotubes was produced by dispersing carbon nanotubes in N,N-dimethylacetamide, adding 2,6-bis(m-aminophenoxy)benzonitrile and 4,’-oxydiphthalic dianhydride, stirring the mixture for 12 hours, and adding acetic anhydride and pyridine to effect imidization. (Chem. Abs. 138: 369741h).

New Polymer Ventures-Bayer Polymers with annual sales of over $12 billion and accounting for almost 40% of Bayer Group’s sales is becoming independent. Bayer Polymers is a major global player with 23,000 employees, annual production of 6 million metric tons of various polymers, at 120 sites around the globe. As Chairman Hagen Noerenberg put it the company feels comfortable offering 2/3 commodity and 1/3 specialty polymers. The new company links three geographic regions: the Americas, Asia-Pacific, and the Europe-Middle East-Africa regions. Four marketing divisions handle a range of customers. The new structure pulls together two basic categories: thermoplastics/rubber and urethanes/coatings/adhesives including fibers. Thermoplastics and rubber combines semi-crystalline products such as styrenics, polycarbonate (including sheet), with elastomer materials like butadiene, butyl rubber, technical rubber products and rubber chemicals. An important component material is Makrolon polycarbonate first synthesized by Bayer over 50 years ago. Challenges here include: combining continuous improvement of production processes with emerging new applications. Norenberg pointed out that new applications and markets are arising particularly in Asia-Pacific. As a result much of the capital expenditure budget for the fiscal year will be spent in China such as a plant for coatings raw materials near Shanghai and further plants to follow for polycarbonate and polyurethane raw materials. (P. Short, C&EN, May 26, 2003, p. 14).