Polycarbonate-Siloxane Copolymers

The synthesis and characterization of poly(hexamethylene sebacate-tiimethyl-siloxane) block copolymers, prepared by coupling Cl- or McjNH-terminated dimethylsiloxanes with OH-terminated poly(hexamethylene sebacate), have been studied. The copolymers containing 19—90% siloxane were characterized by n.m.r., viscosity, DSC and CPC. All the polymers were found to be crystalline. The copolymers containing 69% siloxane, when cast from solution or melts, indicated a reduction in spherulite size as the siloxane concentration increased, although only a small m.pt. depression was observed. All the copolymers have critical surface tensions similar to dimethylsiloxane homopolymers. Polycarbonate-Siloxane Copolymers.—A model has been proposed to predict the micromorphology and mechanical properties of block copolymers of bisphenol-A polycarbonate and poly(dimethylsiloxane). N.m.r. data upon 65 35 (wt%) copolymer of poly(dimethylsiloxane) and bisphenol-A polycarbonate, with block lengths of 20—100 monomer units, were found to be in agreement with the predictions of a spin-diffusion model.  

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Linear polysiloxanes having reactive terminal groups are often condensed with reactive orgaiuc polymers. For example, hydroxy-terminated siloxanes can be condensed with a carboxy-terminated polyester, as illustrated in equation (28). The resulting polymers behave as thermoplastic elastomers, having some of the desirable properties of both siloxanes and polyesters. Similar condensation reactions have been used to synthesize siloxane copolymers with polyamides, polyethers, polycarbonates, and so on. 

Samples of styrene-dimethylsiloxane and poly (2,6-diphenyl )phenylene ether-dimethylsiloxane block copolymers were also examined as spread films. The styrene-siloxane copolymers included AB, ABA, and repeating block copolymer types. In these cases, as with the polycarbonate, the organic homopolymers do not form monolayers when we try to spread volatile solvent solutions on water. The characteristics of the copolymer spread films, however, were similar to those of the BPAC—DMS copolymers. In all cases, sigmoidal 7r-A curves were obtained, and surface pressures above 10 dynes/cm were unstable. (All of the samples examined had organic blocks of 15 or more monomer units.) A typical curve, for a styrene-dimethylsiloxane repeating block copolymer (19), is shown in Figure 4. 

Fig. 2.21 Effect of char yield of polymers on oxygen index The straight line represents the calculated oxygen indices while the points are actual measured values. Notations at the measured points 12,13,22 polyethersulphone 11,20,24 polyphenylene-sulphide 15 polyarylsulphone 18 ABS 17, 25 chlorinated PVC 14, 19 polycarbonate 30, 31 phenolphthalein/polycarbonate copolymer 23 fluorinated polycarbonate/poly(dimethyl siloxane) copolymer 32 poly(vinyl fluoride) 58 poly(vinylidene fluoride) Reprinted from Ref. 40 by permission of Marcel Dekker, Inc. Copyright Marcel Dekker, Inc.,...

However, care must be taken to reduce overly excessive shear stresses that may be present, typically at gates and sharp corners. Adequate venting is essential when a fast injection speed is selected. High mold temperatures are desirable for optimum flow, minimum molded-in stress, and optimal surface appearance. For the greatest machine productivity, polycarbonate grades with mold release are used to reduce the amount of ejection force required to remove parts from mold cavities. Recent efforts with siloxane copolymers of polycarbonate have shown productivity improvements due to the reduction in surface friction. This allows for ejection at higher part temperatures due to reduced ejection forces. 

Finally, CarboSil and ChronoSil are thermoplastic polysiloxane/polycarbonate/ PU copolymers able to combine the mechanical strength of polycarbonate-based PUs with the biostability and hemocompatibihty of siloxane-based PUs. These products are also resistant to environmental stress aacking and therefore suitable for long-term cardiovascular applications. 

Hagenaars AC, Bailly C, Schneider A, Wolf BA (2002) Preparative fractionation and characterization of polycarbonate/eugenol-siloxane copolymers. Polymer 43 2663-2669 Schmiedbauer J, Sybert PD (2000) In Legrand DG, Bendler JT (eds) Handbook of polycarbonate science and technology. Marcel Dekker, New York... 

Omega-SLllyl polycarbonates have been hydrosilated with either tertiary silanes or ym-tetramethyldisiloxane to yield silylated polycarbonates or polycarbonate-disiloxane-polycarbonate triblock copolymers.The siloxane-containing polymers exhibit relatively lower Tg and higher thermooxidative stability compared with bisphenol A polycarbonate. Hydrosilation of allyl-terminal poly(alkyleneoxide-co-sulfone) in 1 1 or 2 1 ratio with hydride-terminal polysiloxane leads to ABC and (AB)2C type block-terpolymers, respectively. DSC studies indicate microphase separation, while TGA data point to higher thermal stability for the siloxane... 

Figure 10 Structure of bisphenol-A-polycarbonate/eugenol-capped siloxane copolymer. Reprinted from Hagenaars, A. C. Bailly, Ch. Schneider, A. Wolf, B. A. Polymer 2002, 43, 2663. Copyright 2002, with permission from Elsevier.

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

Figure 1. Stress-strain curves of polycarbonate-polydimethyl-siloxane block copolymers (Crosshead Speeds 5 cm/min). (Reproduced from Refs. 15 18. Copyright 1980, 1984 American Chemical Society.)...

Chen and Gardella used this surface engineering strategy to create siloxane-rich surfaces [40]. Their approach involved the blending of a homopolymer (A) with a block copolymer composed of a block with the same chemical identity as the homopolymer (A) and a block of PDMS. For all homopolymer types studied (polystyrene, poly(cc methyl.styrene) and Bisphenol A polycarbonate), XPS analysis of Si C ratios revealed a significant enrichment of the PDMS... 

Si NMR of siloxane systems has been used in studying organosilicone containing block copolymers to determine block length and chemical redistribution during polymerization. (85) Block copolymers of bisphenol A polycarbonate (BPAP) and polydimethyl-siloxane (PDMS) [20] were studied by both and Si NMR to determine a variety of structural parameters. 

Tphe surface activity of block copolymers containing dimethylsiloxane units as one component has received considerable attention. Silicone-poly ether block copolymers (1,2,3) have found commercial application, especially as surfactants in polyurethane foam manufacture. Silicone-polycarbonate (4, 5), -polystyrene (6, 7), -polyamide (8), -polymethyl methacrylate (9), and -polyphenylene ether (10) block copolymers all have surface-modifying effects, especially as additives in other polymeric systems. The behavior of several dimethylsiloxane-bisphenol A carbonate block copolymers spread at the air—water interface was described in a previous report from this laboratory (11). Noll et al. (12) have described the characteristics of spread films of some polyether—siloxane block co-... 

A capillary lung produced by Dow Chemical Co. (38) can pass 1.4 liters/min/m2 of blood. It has siloxane-polycarbonate copolymer hollow fibers of 150 p inside diameter, 25 /x wall thickness, and is 8.5 cm in active length. Prime volume is 100 ml/m2. One square meter transfers 51 ml/min of oxygen and 66 ml/min of carbon dioxide at 1.4 liters/min/m2... 

In order to improve the low-temperature notched impact strength of polycarbonate while still maintaining the transparency, new polycarbonate-poly(dimethyl siloxane) block copolymers were developed (Maruvada et al. 2005). These PC-siloxane block copolymers were transparent as long as the siloxane block length was kept short (<10 units), so that fine siloxane rubber domains (10-40 nm) were... 

For a given notched-lzod value, a higher melt flow can be obtained via use of a copolymer than with the corresponding BPA homopolymer (e.g., Lexan resins). For example, Lexan SP grades possess almost twice the melt flow index (MFI) of the BPA homopolymer resins at a 640 J/m (12 ft Ib/in) notched Izod. The tradeoff for the increased flow is a corresponding decrease in the distortion temperature under load (DTUL) of 20°C, as shown in Fig. 14.7. These resins are being supplanted by the siloxane-BPA polycarbonate (see the section PC Siloxane Block Copolymers ), which provide an even better balance of melt flow and ductility without a significant loss in heat performance. 

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