Poly intermediate molecular weight

In refinery applications such as the delayed coker, linear poly-(dimethylsiloxane)s of intermediate molecular weight are used. These products are normally described in terms of their viscosity in centistokes. Thus a 60,000- or 100,000-centistoke silicone fluid would be the typical recommendation for use in a delayed coker. More viscous and consequently higher molecular weight silicones have been used as described in U.S. Patent 3 700 587 (11). 

Interpenetrating elastomeric network Intumescent flame retardant Interpenetrating homopolymer network Elastomerie eopolymer from isobutene and isoprene (ANSI/ASTM, lUPAC) see also Butyl, GR-I, PlBl Poly(isobutylene) see also PIB Intermediate molecular weight Isophthalic acid... 

Polymerization by Transimidization Reaction. Exchange polymerization via equihbrium reactions is commonly practiced for the preparation of polyesters and polycarbonates. The two-step transimidization polymerization of polyimides was described in an early patent (65). The reaction of pyromellitic diimide with diamines in dipolar solvents resulted in poly(amic amide)s that were thermally converted to the polyimides. High molecular weight polyimides were obtained by employing a more reactive bisimide system (66). The intermediate poly(amic ethylcarboamide) was converted to the polyimide at 240°C. 

Solution Polymerization. Solution polymerization of vinyl acetate is carried out mainly as an intermediate step to the manufacture of poly(vinyl alcohol). A small amount of solution-polymerized vinyl acetate is prepared for the merchant market. When solution polymerization is carried out, the solvent acts as a chain-transfer agent, and depending on its transfer constant, has an effect on the molecular weight of the product. The rate of polymerization is also affected by the solvent but not in the same way as the degree of polymerization. The reactivity of the solvent-derived radical plays an important part. Chain-transfer constants for solvents in vinyl acetate polymerizations have been tabulated (13). Continuous solution polymers of poly(vinyl acetate) in tubular reactors have been prepared at high yield and throughput (73,74). 

An overview of the synthesis and characterization of a unique class of polymers with a phosphorus-nitrogen backbone Is presented, with a focus on poly(dichloro-phosphazene) as a common Intermediate for a wide variety of poly(organophosphazenes). Melt and solution polymerization techniques are Illustrated, Including the role of catalysts. The elucidation of chain structure and molecular weight by various dilute solution techniques Is considered. Factors which determine the properties of polymers derived from poly(dichlorophos-phazene) are discussed, with an emphasis on the role that the organic substituent can play In determining the final properties. 

Lower molecular weight used in chewing gum, intermediate in production of poly(vinyl alcohol) water-based emulsion paints... 

---