Non-reactive impact modifiers

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... 

Pecorini and Calvert [28] attribute the role of small particles and a small interparticle distance to inducing high toughness in PET by promoting massive shear yielding in the matrix. Their study showed that the non-reactive impact modifier gives a system in which the rubber phase is not well dispersed. It was shown that this is not effective in toughening PET at levels of either 10 or 20%. The... 

Non-reactive impact modifier (copolymer of ethylene and methyl acrylate). b Reactive impact modifier (terpolymer of ethylene, methyl acrylate and glycidyl methacrylate). c Interparticle distance, i.e. the average distance between particles of impact modifier in the PET matrix. 

Non-reactive impact modifier (copolymer of ethylene and methyl acrylate). 

Reactive impact modifiers are preferred for toughening of PET since these form a stable dispersed phase by grafting to the PET matrix. Non-reactive elastomers can be dispersed into PET by intensive compounding but may coalesce downstream in the compounder. Reactive impact modifiers have functionalized end groups. Functionalization serves two purposes - first, to bond the impact modifier to the polymer matrix, and secondly to modify the interfacial energy between the polymer matrix and the impact modifier for enhanced dispersion. Some examples of commercially available reactive impact modifiers for PET are shown in Table 14.3. An example of a non-reactive elastomer that can be used in combination with reactive impact modifiers is ethylene methyl acrylate (EMA), such as the Optema EMA range of ethylene methyl acrylates manufactured by the Exxon-Mobil Chemical Company (see Section 4.2). 

Most non-reactive (unfunctionalized) elastomeric impact modifiers such as general purpose rubbers, are not highly effective at toughening polyesters because they are unable to adequately interact with the polyester matrix so as to achieve... 

Figure 14.11 Variation of the notched Izod impact strength of PET containing 20 % of an elastomeric toughening system as a function of the ratio of reactive to non-reactive modifier. It can be seen that the 30 70 reactive non-reactive mixture provides the optimum balance. The reactive modifier acts more as a compatibilizer in this system. Note units for impact strength (kJ m 2) can be converted to J nr1 by multiplying by 10...

Several research investigations have been made to compatibilize PET or PBT with PPE both by reactive and non-reactive routes of compatibiliza-tion [Brown et al., 1990 and 1991 Akkapeddi and VanBuskirk, 1992]. Compatibilized binary blends of PPE/polyesters still lacked adequate toughness and invariably required the addition of rubbery impact modifiers (reactive or compatible type) and polycarbonate. The addition of polycarbonate presumably suppresses the crystallization of the thermoplastic PET or PBT phase, due to its... 

The blending of polymers offers the opportunity to create materials with modified properties such as impact strength or rigidity without the necessity to synthesize a new polymer. However, because of entropic constraints, most polymer combinations are immiscible. A polymer blend can be produced by a non-reactive or reactive route. 

Nevertheless, compared to an unmodified GF-reinforced polyamide, up to a 2-fold increase in notched Izod impact strength can be obtained via the incorporation of a suitable impact modifier, without significantly sacrificing (<20%) the high modulus and strength. It was found that by blending 10 w% of a 1 1 mixture of a non-reactive rubber (EPR) and a... 

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