Thermoplastic impact modified

Improve both impact strength and rigidity of thermoplastics by using up the energy of crack propagation. Elastomers are prototypical toughening additives. Examples of high-polymeric impact modifier/thermoplastic matrix systems are EVA, CPE and MBS in PVC, EP(D)M and SBS in PA, and acrylic rubbers in polyesters. 

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... 

Acrylic resin Acrylonitrilefbutadiene/styrene copolymer Bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite Butadiene/acrylonitrile copolymer EthyleneA/A copolymer Methoxyethyl acrylate Methyl methacrylate butadiene styrene terpolymer Polyethylene elastomer, chlorinated 2-Propenoic acid, 2-methylmethyl ester, polymer with 1,3-butadiene and butyl 2-propenoate impact modifier, PVC rigid EVA/PVC graft polymer impact modifier, recycled polyamides EPDM, maleated impact modifier, thermoplastics Butadiene/acrylonitrile copolymer impact strength modifier PEG-6 trimethylolpropane impact-resistance lights Polyester carbonate resin impact-resistance, lights Polyester carbonate resin impeller... 

Hard, glassy, brittle thermoplastics such as polystyrene (PS) and polymethylmethacrylate (PMMA) have low attenuations, of order 6-10 dB/cm at 10 MHz, and in the case of PS, a low acoustic impedance. Ductile polymers such as polycarbonate (PC), many polyolefins and impact-modified thermoplastics generally have high absorption coefficients, in the range 20-40 dB/cm. The same molecular structures and mobiUty, which contribute to ductihty, may also contribute to absorption of ultrasonic energy. Not surprisingly, rubbers and, by extension, any polymer above its... 

EPDM/PP TPOs compete directly with styrenic TPEs as low-cost, low-specific-gravity (0.9 to 1.0) materials with fair to good mechanical performance and environmental resistance. They range in hardness (Table 4.15) from 60 Shore A up to 65 Shore D, with the harder products being more commonly found in commercial applications. The harder TPOs are essentially impact-modified thermoplastics and not true rubbers. The softer TPOs are rubbery at room temperature, but these characteristics are rapidly lost at elevated temperatures. EPDM/PP TPOs are therefore generally useful only below 70 to 80°C. 

Three main types of multicomponent polymer systems will be discussed (1) combinations of two or more semicrystalline polymers, (2) impact modified thermoplastics and (3) impact modified thermosets. The microstructure of semi-crystalline multicomponent polymers can often be determined by polarized light microscopy of thin... 

Much of the preceding discussion has included semicrystalline thermoplastics and blends that were used as examples for discussions of structure and process. A brief literature review of impact modified thermoplastics follows. Reich and Cohen [339] studied the phase separation of polymer blends in thin films and compared... 

Noryl. Noryl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polymers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (69). Because the mbber characteristics that are required for optimum performance in DMPPO—polystyrene blends are not the same as for polystyrene alone, most of the HIPS that is used in DMPPO blends is designed specifically for this use (70). Noryl is produced as sheet and for vacuum forming, but by far the greatest use is in pellets for injection mol ding. 

Considerable amounts of EPM and EPDM are also used in blends with thermoplastics, eg, as impact modifier in quantities up to ca 25% wt/wt for polyamides, polystyrenes, and particularly polypropylene. The latter products are used in many exterior automotive appHcations such as bumpers and body panels. In blends with polypropylene, wherein the EPDM component may be increased to become the larger portion, a thermoplastic elastomer is obtained, provided the EPDM phase is vulcanked during the mixing with polypropylene (dynamic vulcani2ation) to suppress the flow of the EPDM phase and give the end product sufficient set. 

Thermoplastic chlorinated polyethylenes are seldom used on their own but primarily in blends with other polymers, particularly PVC. If chlorination is taken to a level at which the polymer is only semi-compatible with the PVC, a blend with high impact strength may be obtained. In these circumstances the material is classified as an impact modifier. 

Typical additive packages for engineering thermoplastics have been described by Titzschkau [9], such as processing aids for PA, PP, or PET/PBT, three-component additive packages for polyamides and polyesters (nucleating agent, lubricant and process heat stabiliser) and coated copper stabilisers for polyamides. Additive packages or combinations of up to five or more additives are quite common. A typical white window PVC profile formulation comprises an acrylic impact modifier, TiC>2, CaCC>3, calcium stearate, a... 

Obviously, there exists severe interplastics competition, e.g. PP vs. ABS, clarified PP vs. PS, PA, PVC, HDPE and PS (Table 10.7). A wide range of cross-linked and thermoplastic elastomer applications, from footware to automotive parts and toothbrushes, are adopting new metallocene-catalysed polyolefin elastomers (POEs). These low-density copolymers of ethylene and octene were first accepted as impact modifiers for TPOs, but now displace EPDM, (foamed) EVA, flexible PVC, and olefinic thermoplastic vulcanisates (TPVs). Interpolymer competition may also result from... 

Although the main use of impact modifiers is with thermoplastics, thermosets also benefit. The agent is added at the monomer stage. Thus epoxy polymers can be made less brittle by the addition of rubbers. Care has to be taken that the high temperature properties of the thermoset are not compromised. 

PVC is regarded as perhaps the most versatile thermoplastic resin, due to its ability to accept an extremely wide variety of additives Plasticizers, stabilizers, fillers, processing aids, impact modifiers, lubricants, foaming agents, biocides, pigments, reinforcements. .. 

Crosslinked rubbery polymers that are used as impact modifiers often do not have sufficient compatibility with the hard matrix of the surrounding ther-moplast. One elegant method is to cover the rubbery modifier particle with a thin layer of a polymer that is compatible with both, the rubbery core and the thermoplastic matrix. 

Safety precautions Before this experiment is carried out, Sect. 2.2.5 must be read as well as the material safety data sheets (MSDS) for all chemicals and products used. This example describes the concept of core/shell impact modifiers for thermoplastic polymers (see Sect. 5.51). 

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. 

DMTA is a very interesting tool for characterizing heterogeneous materials in which domains of distinct Tg values coexist. The most interesting cases involve modified thermosets of different types (see Chapter 8). Examples are the use of rubbers (e.g., liquid polybutadiene and random copolymers), or thermoplastics (e.g., polyethersulphone or polyetherimide in epoxy matrices or poly(vinyl acetate) in unsaturated polyesters), as impact modifier (epoxies), or low-profile additives (polyesters). The modifier-rich phase may be characterized by the presence of a new a peak (Fig. 11.10). But on occasions there may be superposition of peaks and the presence of the modifier cannot be easily detected by these techniques. If part of the added polymer is soluble in the thermoset matrix, its eventual plasticizing effect can be determined from the corresponding matrix Tg depletion, and the... 

CPE impact modifiers contain around 35% of chlorine and are thermoplastic in nature. With a similar melting point to PVC, they initially form a network structure which changes to a particulate structure on processing (134). They also have good processability and excellent weathering performance consequently they are also used for window profiles (287). The effect of residual... 

The next evolution in ABS technology was the need to produce a transparent ABS. Existing ABS was opaque owing to the scattering of light by the rubber domains. While producing smaller domains would make the system clear, it led to a loss of impact strength. The answer was to modify the refractive index of the components so that the various phases were less optically different. A fourth monomer , methyl methacrylate, was used to minimize the refractive index variation in the ABS and a clear impact-resistant thermoplastic named Cyclolac CIT was achieved [20]. 

Brandstetter et al. [25] produced similar particles without the intensive shearing step by polymerizing acrylate monomer in water in the presence of a long-chain alcohol, an emulsifier and a water-insoluble initiator. The particles have a mean particle size of 0.2-6 p,m. After their preparation the particles can be grafted with SAN and then used as impact modifiers for ASA or as delustering agents for thermoplastics [26]. 

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