Impact modifiers styrenic copolymers

Figure 2.11 Transparent impact-modified styrene copolymers by isorefractive phases...

Figure 5.35 Property changes in impact-modified styrene copolymers [658]...

Such impact modifiers containing copolymers of butadiene and styrene and at least one stage or shell of poly(methyl methacrylate) are known MMBS core-shell polymers. 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

At one time butadiene-acrylonitrile copolymers (nitrile rubbers) were the most important impact modifiers. Today they have been largely replaced by acrylonitrile-butadiene-styrene (ABS) graft terpolymers, methacrylate-buta-diene-styrene (MBS) terpolymers, chlorinated polyethylene, EVA-PVC graft polymers and some poly acrylates. 

There are various requirements for impact-modified PVC. The most demanding is for outdoor sidings and window frames, where lifetimes of 20 years are expected. Because butadiene polymers or copolymers (e.g., acrylonitrile/butadiene/styrene (ABS), methyl methacrylate/butadiene/styrene (MBS)) are susceptible to UV degradation these polymers are usually not employed instead acrylate polymers are used for these applications. 

Figure 14.9 Effect of various impact modifiers (25wt%) on the notched Izod impact strength of recycled PET (as moulded and annealed at 150°C for 16 h) E-GMA, glycidyl-methacrylate-functionalized ethylene copolymer E-EA-GMA, ethylene-ethyl acrylate-glycidyl methacrylate (72/20/8) terpolymer E-EA, ethylene-ethyl acrylate EPR, ethylene propylene rubber MA-GPR, maleic anhydride grafted ethylene propylene rubber MBS, poly(methyl methacrylate)-g-poly(butadiene/styrene) BuA-C/S, poly(butyl acrylate-g-poly(methyl methacrylate) core/shell rubber. Data taken from Akkapeddi etal. [26]...

MBS (methyl methacrylate-butadiene-styrene) graft copolymers are known as one of the most efficient non-reactive impact modifiers for PET and also poly(vinyl chloride) (PVC). MBS is used commercially as an effective impact modifier for PET recyclate [27], Typical MBS rubber particles contain an elastomeric core of... 

Such materials essentially contain PS as the matrix polymer and uniformly dispersed in this matrix are elastomeric types of particles, which form the soft phase (3). The soft phase is essentially composed of poly(butadiene) or of block copolymers of butadiene and styrene. This soft phase can be also addressed as the impact modifier for PS. 

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). 

Core-shell emulsion polymers with a core or rubbery stage based on homopolymers or copolymers of butadiene are used as impact modifiers in matrix polymers, such as ABS, for styrene acrylonitrile copolymer methyl methacrylate (MMA) polymers, poly(vinyl chloride) (PVC), and in various engineering resins such as polycarbonate) (PC) poly(ester)s, or poly(styrene)s, further in thermosetting resins such as epoxies. 

Besides MMBS, also related copolymers, such as methyl meth-acrylate/acrylonitrile/butadiene/styrene and acrylonitrile/ethylene/ propylene/diene/styrene are impact modifiers for PC compositions (16). 

The MABS copolymers are prepared by dissolving or dispersing polybuiadiene rubber in a methyl methacrylate—acrylonitrile—styrene monomer mixture. MBS polymers are prepared by grafting methyl methacrylate and styrene onto a styrene—butadiene rubber in an emulsion process. The product is a two-phase polymer useful as an impact modifier for rigid polytvinyl chloride). 

STYRENE. Styrene, CgH5CH=CH2, is the simplest and by far the most important member of a series of aromatic monomers. Also known commercially as styrene monomer (SM). styrene is produced in large quantities for polymerization. It is a versatile monomer extensively used for the manufacture of plastics, including crystalline polystyrene, rubber-modified impact polystyrene, expandable polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS), styrene-acrylonitrile resins (SAN), styrene-butadiene latex, styrene-butadiene rubber (SBR). and unsaturated polyester resins. See also Acrylonitrile Polymers. 

STYRENE-MALEIC ANHYDRIDE. A thermoplastic copolymer made by the copolymerization of styrene and maleic anhydride. Two types of polymers are available—impact-modified SMA terpolymer alloys (Cadon ) and SMA copolymers, with and without rubber impact modifiers (Dylark ). These products are distinguished by higher heat resistance than the parent styrenic and ABS families. The MA functionality also provides improved adhesion to glass fiber reinforcement systems. Recent developments include lerpolymer alloy systems with high-speed impact performance and low-temperature ductile fail characteristics required by automotive instrument panel usage. 

ABA ABS ABS-PC ABS-PVC ACM ACS AES AMMA AN APET APP ASA BR BS CA CAB CAP CN CP CPE CPET CPP CPVC CR CTA DAM DAP DMT ECTFE EEA EMA EMAA EMAC EMPP EnBA EP EPM ESI EVA(C) EVOH FEP HDI HDPE HIPS HMDI IPI LDPE LLDPE MBS Acrylonitrile-butadiene-acrylate Acrylonitrile-butadiene-styrene copolymer Acrylonitrile-butadiene-styrene-polycarbonate alloy Acrylonitrile-butadiene-styrene-poly(vinyl chloride) alloy Acrylic acid ester rubber Acrylonitrile-chlorinated pe-styrene Acrylonitrile-ethylene-propylene-styrene Acrylonitrile-methyl methacrylate Acrylonitrile Amorphous polyethylene terephthalate Atactic polypropylene Acrylic-styrene-acrylonitrile Butadiene rubber Butadiene styrene rubber Cellulose acetate Cellulose acetate-butyrate Cellulose acetate-propionate Cellulose nitrate Cellulose propionate Chlorinated polyethylene Crystalline polyethylene terephthalate Cast polypropylene Chlorinated polyvinyl chloride Chloroprene rubber Cellulose triacetate Diallyl maleate Diallyl phthalate Terephthalic acid, dimethyl ester Ethylene-chlorotrifluoroethylene copolymer Ethylene-ethyl acrylate Ethylene-methyl acrylate Ethylene methacrylic acid Ethylene-methyl acrylate copolymer Elastomer modified polypropylene Ethylene normal butyl acrylate Epoxy resin, also ethylene-propylene Ethylene-propylene rubber Ethylene-styrene copolymers Polyethylene-vinyl acetate Polyethylene-vinyl alcohol copolymers Fluorinated ethylene-propylene copolymers Hexamethylene diisocyanate High-density polyethylene High-impact polystyrene Diisocyanato dicyclohexylmethane Isophorone diisocyanate Low-density polyethylene Linear low-density polyethylene Methacrylate-butadiene-styrene... 

Core-shell polymers were commercially introduced as impact modifiers for poly(vinyl chloride) PVC, in the 1960s. They are produced by a two-stage latex emulsion polymerization technique (Cruz-Ramos, 2000). The core is a graftable elastomeric material, usually crosslinked, that is insoluble in the thermoset precursors. Typical elastomers used for these purposes are crosslinked poly(butadiene), random copolymers of styrene and butadiene,... 

Various patents on the homopolymerization of BD in the presence of styrene are available [581-590]. According to these patents, St is used as a solvent in which BD is selectively polymerized by the application of NdV/DIBAH/EASC. At the end of the polymerization a solution of BR in St is obtained. In subsequent reaction steps the unreacted styrene monomer is either polymerized radically, or acrylonitrile is added prior to radical initiation. During the subsequent radical polymerization styrene or styrene/acrylonitrile, respectively, are polymerized and ris-l,4-BR is grafted and partially crosslinked. In this way BR modified (or impact modified) thermoplast blends are obtained. In these blends BR particles are dispersed either in poly(styrene) (yielding HIPS = high impact poly(styrene) or in styrene-acrylonitrile-copolymers (yielding ABS = acrylonitrile/butadiene/ styrene-terpolymers). In comparison with the classical bulk processes for HIPS and ABS, this new technology allows for considerable cost reductions... 

A major disadvantage of PVC is its relatively low service temperature (60-70 °C) and the addition of high levels of some polymers can improve the heat distortion temperature and Vicat softening point. An example of such a polymer is alphamethyl styrene-acrylonitrile (AMSAN) copolymer. AMSAN-ABS polymer can be used as a combined heat and impact modifier. 

Effects of additives in the matrix were observed by substituting for methyl methacrylate a poly (methyl methacrylate) homopolymer with a solution molecular weight of 950,000, a vinylidene fluoride copolymer (Pennwalt s Kynar 7201), and a methacrylate-butadiene-styrene impact modifier (Marbon s Blendex BTA IIIN). Concentrations were 2% on the total dispersion volume. The same additives were studied at the same volume concentration in the dispersed phase. Barium sulfate (Whittaker, Clark, and Daniels Barytes No. 91), a commonly used additive for radiopacity, was also studied in the dispersed phase. Responses were observed by the test methods described below. 

Acrylonitrile-styrene-acrylate (ASA) constitutes a versatile member of the group of styrenic copolymers used for housings, covers and other applications which require excellent surface appearance and environmental stability combined with high impact resistance and stiffness. It consists of a poly(styrene-acrylonitrile) matrix modified with small rubber particles. 

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