Polymer blends with polycarbonates

Blends comprising sulfone polymers and other middle- to high-temperature engineering resins with at least a partially aromatic backbone structure are feasible in many cases. Such blends include sulfone polymer blends with polycarbonates, some polyesters, polyarylates, poly-etherimides, and polyaryletherketones. Blends of PPSF with poly-aryletherketones such as PEEK or PEK are particularly interesting as these blends form very finely dispersed systems with synergistic strength, impact, and environmental stress cracking resistance properties [43, 44]. 

Amorphous polyamides, preferably copolyamides from iso- and terephthalic acid with hexamethylene diamine have gained importance as components in polymer blends with polycarbonate, polyphenylene ether and/or functionalized elastomers, and also with the semi-crystalline polyamides 6 and 66. These copolyamides increase the chemical resistance of polycarbonate or polyphenylene ether and reduce stress-cracking sensitivity to concentrated zinc chloride solution in polyamide 6 and 66. Moreover, these copolyamides provide for improved compatibility. 

In polymers such as polystyrene that do not readily undergo charring, phosphoms-based flame retardants tend to be less effective, and such polymers are often flame retarded by antimony—halogen combinations (see Styrene). However, even in such noncharring polymers, phosphoms additives exhibit some activity that suggests at least one other mode of action. Phosphoms compounds may produce a barrier layer of polyphosphoric acid on the burning polymer (4,5). Phosphoms-based flame retardants are more effective in styrenic polymers blended with a char-forming polymer such as polyphenylene oxide or polycarbonate. 

Polycarbonates based on tetramethylbisphenol A are thermally stable and have a high Vicat softening point of 196°C. On the other hand they have lower impact and notched impact resistance than the normal polymer. Blends with styrene-based polymers were introduced in 1980, and compared with PC/ABS blends, are claimed to have improved hydrolytic resistance, lower density and higher heat deflection temperatures. Suggested applications are as dishes for microwave ovens and car headlamp reflectors. 

The effect of dissolved CO2 on the miscibility of polymer blends and on phase transitions of block copolymers has been measured with spectroscopy and scattering (40). The shifts in phase diagrams with CO2 pressure can be pronounced. Polymer blends may be trapped kinetically in metastable states before they have time to phase separate. Metastable polymer blends of polycarbonate (PC) and poly(styrene-cn-acrylonitiile) were formed with liquid and supercritical fluid CO2 in the PCA process, without the need for a surfactant. Because of the rapid mass transfer between the CO2 phase and the solution phase, the blends were trapped in a metastable state before they... 

Brief reviews covering redistribution reactions in polyester and in polycarbonate binary blends have been prepared by Porter et al. [1989] and Porter and Wang [1992]. Selected references for redistribution processes in PEST/PEST blends are listed in Table 5.7. Early studies of these processes focused on measuring the extent of redistribution under specific processing conditions rather than on producing compatibilized polymer blends with an attractive balance of properties. A number of more recent studies have reported the limits of miscibility for certain melt-mixed polyester pairs in the absence of transesterification — see for example the NMR study of PC/PET blends [Abis et al., 1994]. 

The most common polymers used for instrument panel stmctnres are acrylonitrile-butadiene-styrene (ABS), acrylonitrile-butadiene-styrene blended with polycarbonate (ABS/PC), polycarbonate (PC), poly(phenylene oxide) blended with nylon (PPO/nylon), poly(phenylene oxide) blended with styrene (PPO/styrene), polypropylene (PP), and styrene-maleic anhydride copolymer (SMA) [3]. The percentage of each of these polymers typically used in year 2000 models is shown below in Table 17.3 [3], All of these materials by themselves... 

The second most important class of commercial polycarbonate blends is derived by blending with commercial thermoplastic polyesters such as polybutylene tere-phthalate (PBT) and polyethylene terephthalate (PET). Both PBT and PET are crystallizable polymers and hence offer the expected chemical resistance advantages of the crystalline polymers in blends with polycarbonate. Among the thermoplastic polyester/polycarbonate blends, the PBT/PC blend has the major commercial volume, followed by the PET/PC blend. A copolymer of 1,4-cyclohexanedimethanol, ethylene glycol, and terephthalic acid (PCTG) forms a miscible blend with polycarbonate. PCTG/PC blend was earlier offered by Eastman (Ektar ) for specialty applications, but it is no longer commercial. 

Stanuloy ST Poly(ethylene terephthalate), PET, modified or blended with polycarbonate MRC Polymers, Inc. 

There are two types of disparities between the steady-state and dynamic flow behavior, one related to the interlayer slip (Eq. (2.56)) and the second to the flow engendered migration of the low viscosity component to the high stress location. Blends of liquid crystal polymer (LCP) with polycarbonate (PC) or poly(ethylene-terephthalate) (PET) may serve as an example of the first type [321,322], whereas those of EPDM (ethylene-propylene-diene terpolymer) with poly(vinylidene-co-hexafluor-opropylene), Viton , exemplify the second [323-325]. In both cases the steady-state shearing was performed in a capillary viscometer- the viscosity ratio of the dynamic to the steady-state data for these two blends was about two and six, respectively. 

ASA resins are available for blow molding, extrusion, and injection molding. ASA resins are also blended with polycarbonate, polyvinyl chloride, and acrylonitrile ethylene styrene for specific property enhancements. The main suppliers are BASF (Luran and Centrex), BP Chemicals (Barex), Bayer (Centrex), LG Chemical (LI and LE polymers), and GE (Geloy). 

PS forms a miscible blend with polyxylenyl ether and with tetramethyl bis-phenol polycarbonate. Styrene acrylonitrile (SAN) copolymers can form miscible polymer blends with PMMA over some compositional window of AN and with polyvinyl chloride (PVC). PS and poly(cyclohexyl methacrylate) were reported to... 

Gas sorption and transport in a copolyester and its blend with polycarbonate, /. Polym. Sci. Part B Polym. 

Automotive appHcations account for about 116,000 t of woddwide consumption aimuaHy, with appHcations for various components including headlamp assembHes, interior instmment panels, bumpers, etc. Many automotive appHcations use blends of polycarbonate with acrylonitrile—butadiene—styrene (ABS) or with poly(butylene terephthalate) (PBT) (see Acrylonitrile polymers). Both large and smaH appHances also account for large markets for polycarbonate. Consumption is about 54,000 t aimuaHy. Polycarbonate is attractive to use in light appHances, including houseware items and power tools, because of its heat resistance and good electrical properties, combined with superior impact resistance. 

During the eady development of polycarbonates, many bisphenols were investigated for potential useftil products. Some of these monomers and polymers are hsted in Table 3. Despite this intensive search, however, no homopolycarbonates other than that of BPA have been produced. Copolymers and blends, on the other hand, have been quite successhil. Blends of polycarbonate with ABS and with poly(butylene terephthalate) (PBT in particular have shown significant growth since the mid-1980s. 

Blends with good mechanical properties can be made from DMPPO and polymers with which DMPPO is incompatible if an appropriate additive, compatibilizing agent, or treatment is used to increase the dispersion of the two phases. Such blends include mixtures of DMPPO with nylon, polycarbonate, polyester, ABS, and poly(phenylene sulfide). 

Acrylic Resins. The first synthetic polymer denture material, used throughout much of the 20th century, was based on the discovery of vulcanised mbber in 1839. Other polymers explored for denture and other dental uses have included ceUuloid, phenolformaldehyde resins, and vinyl chloride copolymers. Polystyrene, polycarbonates, polyurethanes, and acryHc resins have also been used for dental polymers. Because of the unique combination of properties, eg, aesthetics and ease of fabrication, acryHc resins based on methyl methacrylate and its polymer and/or copolymers have received the most attention since their introduction in 1937. However, deficiencies include excessive polymerization shrinkage and poor abrasion resistance. Polymers used in dental appHcation should have minimal dimensional changes during and subsequent to polymerization exceUent chemical, physical, and color stabiHty processabiHty and biocompatibiHty and the abiHty to blend with contiguous tissues. 

In a molded polymer blend, the surface morphology results from variations in composition between the surface and the bulk. Static SIMS was used to semiquan-titatively provide information on the surface chemistry on a polycarbonate (PC)/polybutylene terephthalate (PBT) blend. Samples of pure PC, pure PBT, and PC/PBT blends of known composition were prepared and analyzed using static SIMS. Fn ment peaks characteristic of the PC and PBT materials were identified. By measuring the SIMS intensities of these characteristic peaks from the PC/PBT blends, a typical working curve between secondary ion intensity and polymer blend composition was determined. A static SIMS analysis of the extruded surface of a blended polymer was performed. The peak intensities could then be compared with the known samples in the working curve to provide information about the relative amounts of PC and PBT on the actual surface. 

Blends of ABS with polycarbonates have been available for several years (e.g. Bayblend by Bayer and Cycoloy by Borg-Wamer). In many respects these polymers have properties intermediate to the parent plastics materials with heat distortion temperatures up to 130°C. They also show good impact strength, particularly at low temperatures. Self-extinguishing and flame retarding grades have been made available. The materials thus provide possible alternatives to modified poly(phenylene oxides) of the Noryl type described in Chapter 21. (See also sections 16.16 and 20.8.)... 

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