Processing polycarbonates

Processing. Polycarbonates may be fabricated by ah. conventional thermoplastic processiag operatioas, of which iajectioa mol ding is the most common. Recommeaded operatiag coaditioas are stock temperatures of 275—325°C and mol ding pressures of 69—138 MPa (10,000—20,000 psi). 

Processing. Polycarbonates may be fabricated by all conventional thermoplastic processing operations, of which injection molding is the most common. 

Abdel-Goad M, Potschke P (2005) Rheological characterization of melt processed polycarbonate-multiwalled carbon nanotube composites. J Non-Newtonian Fluid Mech 128 2-6... 

These copolymers, containing a high level of ITR, have also been commercialized in a highly weather-resistant film that has the appearance of a paint film. The film is available in transparent and opaque colors. In addition, the film can be made with a metallic look. The film can be used with in-mold-decoration (IMD) (see the section Processing Polycarbonates ) molding processes to produce class A automotive exterior parts. Because the film contains very high levels of the ITR resin, it has an excellent balance of scratch resistance, weatherability, chemical resistance, and thermal performance. 

Informative and valuable sections of the chapter are Reengineering the Molecule and the previous sections to which this section refers, Commercial Production of Polycarbonate, Polycarbonate Properties General-Purpose and Apphcation-Specific Grades, Applications using Polycarbonates and Processing Polycarbonate. ... 

H. T. Pham, S. P. Namhata, and C. P. Bosnyak, Compositions for Tough and Easy Melt Processible Polycarbonate/Polyolefin Blend Resin, US Patent 6,025,420, Dow Chemical Co., Midland, MI, 2000. 

Ci-derivatives Trichloromethane Monochloromethane Tetrachloromethane Phosgene Hydrochloro-fluorocarbons Polytetrafluoroethylene (PTFE) Silicones, methylcellulose Industrial processes Polycarbonates, diisocyanates, polyurethanes... 

As higher temperatures are required to process polycarbonate, heat transfer through the mold to the material can be a problem. The best results are achieved using oil-jacketed molds and finer powder than the 35 mesh (500 tm) commonly used for polyethylene. However, bubbles can still occur in parts and it is common to see textured mold surfaces used to disguise their presence. The use of a nitrogen atmosphere can reduce the yellow color caused by degradation. 

Pbtschke, P., Pomes, T.D., Paul, D.R. Rheological behavior of multiwalled carbon nanotube/polycarbonate composites . Polymer 43(11) (2002) 3247-3255 Pbtschke, P., Dudkin, S.M., Ahg, I. Dielectric spectroscopy on melt processed polycarbonate-multiwalled carbon nanotube composites . Polymer 44(11) (2003), 5023-5030... 

Poetschke P, Dudkin S M and Alig I (2003) Dielectric spectroscopy on melt processed polycarbonate-multiwalled carbon nanotube composites, Polymer 44 5023-5030. Kramarenko V Y, Shantalii T A, Karpova I L, Dragan K S, Privalko E G, Privalko V P, Pragiadakis D and Pissis P (2004) Polyimides reinforced with the sol-gel derived organosilicon nanophase as low dielectric permittivity materials, Polym Adv Technol 15 144-148. 

Fig. 26. Qualitative compatison of substrate materials for optical disks (187) An = birefringence IS = impact strength BM = bending modulus HDT = heat distortion temperature Met = metallizability WA = water absorption Proc = processibility. The materials are bisphenol A—polycarbonate (BPA-PC), copolymer (20 80) of BPA-PC and trimethylcyclohexane—polycarbonate (TMC-PC), poly(methyl methacrylate) (PMMA), uv-curable cross-linked polymer (uv-DM), cycHc polyolefins (CPO), and, for comparison, glass.

Fig. 4. Diagram of the two-step process to manufacture nucleation track membranes, (a) Polycarbonate film is exposed to charged particles in a nuclear reactor, (b) Tracks left by particles are preferentially etched into uniform cylindrical pores (8).

Acrylic ESTER POLYMERS Acrylonitrile POLYMERS Cellulose esters). Engineering plastics (qv) such as acetal resins (qv), polyamides (qv), polycarbonate (qv), polyesters (qv), and poly(phenylene sulfide), and advanced materials such as Hquid crystal polymers, polysulfone, and polyetheretherketone are used in high performance appHcations they are processed at higher temperatures than their commodity counterparts (see Polymers containing sulfur). 

Polycarbonates are prepared commercially by two processes Schotten-Baumaim reaction of phosgene (qv) and an aromatic diol in an amine-cataly2ed interfacial condensation reaction or via base-cataly2ed transesterification of a bisphenol with a monomeric carbonate. Important products are also based on polycarbonate in blends with other materials, copolymers, branched resins, flame-retardant compositions, foams (qv), and other materials (see Flame retardants). Polycarbonate is produced globally by several companies. Total manufacture is over 1 million tons aimuaHy. Polycarbonate is also the object of academic research studies, owing to its widespread utiUty and unusual properties. Interest in polycarbonates has steadily increased since 1984. Over 4500 pubflcations and over 9000 patents have appeared on polycarbonate. Japan has issued 5654 polycarbonate patents since 1984 Europe, 1348 United States, 777 Germany, 623 France, 30 and other countries, 231. 

Phosgene addition is continued until all the phenoHc groups are converted to carbonate functionahties. Some hydrolysis of phosgene to sodium carbonate occurs incidentally. When the reaction is complete, the methylene chloride solution of polymer is washed first with acid to remove residual base and amine, then with water. To complete the process, the aqueous sodium chloride stream can be reclaimed in a chlor-alkah plant, ultimately regenerating phosgene. Many variations of this polycarbonate process have been patented, including use of many different types of catalysts, continuous or semicontinuous processes, methods which rely on formation of bischloroformate oligomers followed by polycondensation, etc. 

Transesterification. There has been renewed interest in the transesterification process for preparation of polycarbonate because of the desire to transition technology to environmentally friendly processes. The transesterification process utilizes no solvent during polymerization, producing neat polymer direcdy and thus chlorinated solvents may be entirely eliminated. General Electric operates a polycarbonate plant in Chiba, Japan which produces BPA polycarbonate via this melt process. 

An analogue of the transesterification process has also been demonstrated, in which the diacetate of BPA is transesterified with dimethyl carbonate, producing polycarbonate and methyl acetate (33). Removal of the methyl acetate from the equihbrium drives the reaction to completion. Methanol carbonylation, transesterification using phenol to diphenyl carbonate, and polymerization using BPA is commercially viable. The GE plant is the first to produce polycarbonate via a solventiess and phosgene-free process. 

Medical and health-care related appHcations consume about 21,000 t of polycarbonate aimuaHy. Polycarbonate is popular because of its clarity, impact strength, and low level of extractable impurities. Special grades have been developed to maintain clarity and resistance to yeHowing upon gamma radiation sterilization (qv) processes. Leisure and safety appHcations are many and varied, accounting for about 22,000 t of consumption aimuaHy. The... 

---