Methacrylate-butadiene-styrene-modified blends

There is extensive Hterature on PC blends with ABS, and blends of PC with related materials such as SAN, methacrylate-butadiene—styrene (MBS) emulsion-made core-shell mbber modifiers (297—299), and other impact modifiers. One report reviews some of these approaches and compares PC blends based on emulsion vs bulk ABS (229). In PC—ABS blends, no additional compatihili er is used, because of the near-miscihility of the SAN matrix of ABS and PC. 

Methyl methacrylate-butadiene-styrene (MMBS) types are rarely used as such, but rather in blends as impact modifiers (1). Styr-enic copolymers such as acrylonitrile-butadiene-styrene (ABS) and MMBS make up the largest category of impact modifiers, with about 45% of the impact modifier market (2). The field of polymer blends and the reasons for the addition of impact modifiers have been reviewed (3). 

The three types of force-time behavior noted for HiPS fractured at different temperatures also apply to other polymer blends and grafts, where values of the impact strength (or fracture energy) were measured as a function of temperature. Such behavior has been observed by Bucknall and Street (1967) not only for ABS (Figure 3.17), but also for rubber-modified PVC, HiPS, and a methacrylate-butadiene-styrene (MBS) copolymer. Not surprisingly, the concentration of rubber is important with respect to both the absolute value of impact strength (Figures 3.16 and 3.17) and the type... 

Impact modifiers are often added to BPAPC to counteract this effect (Cheng et al. 1992 Tan et al. 2005) and a few studies have been conducted to investigate the effect of thermal annealing on the mechanical performance of BPAPC. Eor example, blends of BPAPC with several core-shell methacrylate-butadiene-styrene impact modifiers have been studied after aging at 125 °C, 130 °C, and 135 °C (Cheng et al. 1992). 

SMA copolymers and terpolymers have also been used for blending with PVC to improve the heat distortion temperature and processability of PVC. These blends also contain a rubbery component for impact modification that is usually a high rubber ABS or a polymethyl methacrylate grafted styrene-butadiene rubber (MBS). For improved weatherability, acrylic rubber modified PVC has been used for blending with SMA copolymers and terpolymers (Table 15.4). The market for SMA/PVC blends is still relatively low in volume with only a few applications such as in business machine housings as a low cost replacement for flame retarded ABS. 

All the commercial PBT/PC and PET/PC blends also contain typically 10-20 wt% of an additional elastomeric impact modifier. The exact nature and the content of the impact modifier is kept proprietary and often forms the basis for a particular blend patent. Typically, core-shell rubbers such as poly(methyl methacrylate)-grafted butadiene-styrene rubber (MBS) or an all acrylic core-shell rubber such as poly (MMA-g-n-BuA) are used (Nakamura et al. 1975 Chung et al. 1985). ABS (with high polybutadiene content >50 %) or ASA rubber (>50 % aciylate rubber) have also been used. The presence of such a rubber component is definitely needed to obtain high notched Izod impact strengths (>500 J/m) in these blends. 

Additionally to the procedures described earlier, improvements for thermostabilization is copolymerisation of vinyl chloride with suitable monomers. A great number of monomers were investigated to optimize the properties of resins. But only vinyl acetate, vinylidene chloride, ethylene, propylene, acrylonitrile, acrylic acid esters, and maleic acid esters, respectively, are of interest commercially [305,436,437]. The copolymerization was carried out in emulsion, suspension, and solution in connection with water- or oil-soluble initiators, as mentioned elsewhere. Another possibility for modifying PVC is grafting of VC on suitable polymers [305,438], blends of PVC with butadiene/styrene and butadiene/ methacryl acid esters copolymers [433], and polymer-analogous reactions on the macromolecule [439,440] (e.g., chlorination of PVC). 

Stokes, V. K., The vibration welding of polycarbonate/acrylonitrile-butadiene-styrene blends to themselves and to other resins and blends, Polym Eng Sci, 40(10), 2175-2181,2000. Stokes, V. K., The vihration welding of poly(methyl methacrylate) to itself and to polycarbonate, poly(butylene terephthalate), and modified poly(phenylene oxide), J Adhes... 

One way to achieve compatibilization involves physical processes such as shear mixing and thermal history, which modify domain size and shape. The second way is the use of physical additives to increase attraction between molecules and phases. The third method is reactive processing, which is used to change the chemical structure of one or more of the components in the blend and thus increase their attraction to each other. Table 1.5 contains a list of compatibilizers used in the formulation of polyolefin blends. As can be seen from Table 1.5, most of the compatibilizers used in the formulation of polyolefin blends contain compounds such as maleic anhydride, acrylic and methacrylic acid, glycidyl methacrylate, and diblock and triblock copolymers involving styrene, ethylene, and butadiene. 

TEM photomicrographs of fully cured DGEBA/MCDEA blends with 10 wt7o of polyphenylene ether (PPE) and modified by 5 per of purified poly(styrene-b-butadiene-b-methyl methacrylate) SBM triblock, S2026B26M54. (A) PPE-rich droplet 10 mm (B) epoxy-rich substructure and (C) epoxy-rich matrix with dispersed SBM micelles (Os04 staining). (From Th. Fine and J.-P. Pascault, Macromol. Symp. 245-246,375-385, 2006. With permission.)... 

Comparison of a PS-PMMA blend with a corresponding copolymer gave information on the chemical drift. In the analysis of a competitive modified vinyl polymer sample by SEC/FTIR, some of the components of the binder could be readily identified (vinyl chloride, ethyl methacrylate, acrylonitrile), and an epoxi-dized drying oil additive was also detected. An analysis of styrene-butadiene copolymers, including a determination of the styrene/butadiene ratio and of the micro structure of the butadiene units cis/trans, l,2-/l,4-units), was performed by Pasch et al. 

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