Commodity polymer resin blends

Crystal polystyrene is a misnomer because the polymer is an amorphous material. The term "crystal" refers to the high optical clarity of the molded polystyrene homopolymer. It is one of the top five commodity polymer resins in the world. Because most chemical modification methods are expensive, they are impractical for low scale production. For low volume production, polymer blending is the most effective way to modify polystyrene. 

This review summarizes our work at the University of Bayreuth over the last few years on improving the electret performance of the commodity polymer isotactic polypropylene (Sect. 3) and the commodity polymer blend system polystyrene/polyphenylene ether (Sect. 4) to provide electret materials based on inexpensive and easily processable polymers. To open up polymer materials for electret applications at elevated temperatures we concentrated our research on commercially available high performance thermoplastic polyetherimide resins and synthesized several fluorinaled polyetherimides to identify structure-property relations and to improve further the performance at elevated temperatures (Sect. 5). 

The modern tendency is to develop polymer blends that will preserve the desired performance characteristics upon reprocessing. Pew examples of commodity and engineering resin blends are given below. More detailed discussion can be found in [Utracki, 1989a 1998]. 

In the following text examples of recycled polymer blends will be given, first for the commodity, then for the engineering and specialty resin blends. Whenever possible, the methods of compatibilization and re-compatibilization should be the same. In particular, when recycling is to reproduce the original blends performance, the same compatibilization method is essential. For this reason, support of the blends manufacturer should be ascertained. 

Expensive conductive polymers can be blended with a commodity polymer major phase to produce a more economical and easily processed blend. The materials may be either both thermoplastic (e.g., PES), or one may be a thermoset (e.g., a phenolic). Another approach employs blending a rubber phase (EPR or urethane) with a commodity thermoplastic resin like PP, LDPE, or even polyesters or polyamides, to form a co-continuous phase structure in which incorporated carbon black resides either at the interface or within one of the phases. A similar approach, incorporating, for example, PC and PET along with an impact modifier, could be employed to produce conductive automotive body parts that are amenable to electrostatic painting (Harrats and Makhilef 2006b). 

The commodity resin blends represent the major part of the hlend market, hut their market share varies from one country to another. For example, while in Canada 70% of linear low density polyethylenes are blended, in the United States only about 30% benefit from this technology. Furthermore, styrenics blends (viz., HIPS, ABS, blends with SAN, MSAN, SMA, etc.) that constitute a large part of the market, are described in only a few entries. On the other end of the performance spectrum are the specialty blends. Reading today s patent literature one may get the impression that blends with snch resins as polyetherimide, polyamideimide, or hqnid crystal polymers, LCP, are of principal indnstrial interest. These blends also are poorly represented in this EDCPB volume. 

Since the anionically polymerized block copolymers are relatively expensive they have been more frequently used in blends with engineering than commodity resins. Owing to miscibility of styrene blocks with PPE, the SBS and SEBS are natural tougheners for this polymer. However, for blending with PEST, PC, POM or PA, the copolymer should be modified by incorporation of acidic, acid anhydride, or epoxy moieties. 

There is a trend toward specialization in the polymer products industry. Since the industry is expanding globally, a sufficient market is available for these products. Blending is a convenient route to time-efficient and cost-effective upgrading of commodity resins and to tailoring these resins to specific performance profiles for the desired apphcation. The time to commercialization can now be reduced to less than one year for PAB s vs. 8-10 or more years for the synthesis of new polymers. The development of the latter can exceed 10 MM. 

Commodity resins. Most polymers are immiscible, some, as PS with PO, antagonistically so. Outside the ranges of high dilution and of phase co-continuity, the PO/PS blends need to... 

The worldwide commercialization of polymer blends has been directed at the replacement of traditional materials, such as metals and ceramics. Even though plastics can be more costly than other types of materials on a weight basis, they are often more economical in terms of production and manufacturing cost, mainly attributed to the less complex assembly of plastic parts that can be easily formed in complex-finished shapes [1, 21-26], Blending is a convenient route to the time-efficient and cost-effective upgrading of commodity resins and to the tailoring of these resins to specific performance profiles for the desired application. The most common polymer blends and their applications are described below. 

Color Concentrate (Masterbatch). Expert compounders disperse colorants at 20 to 60 percent concentration in a carrier polymer, using high shear to break down agglomerates and produce uniform dispersion of maximum coloring efficiency. This color concentrate is used by processors, simply blending it with virgin (natural color) resin ( letdown with natural ). Typical ratios of concentrate/natural are 1/20 to 1/100. This technique is low in cosL does not create inventory problems, and is most commonly used with commodity resins. 

Engineering polymer blends (EPB) can be roughly divided into blends of an engineering plastic or resin (ER) with a commodity plastic, blends of an engineering plastic with another engineering plastic, blends of an engineering plastic with an elastomer and, blends which contain three or more polymers. We can therefore get combinations such as PPO/PS PPO/PA PC/ABS PET/PBT PBT/PC/SAN etc. each of the blends may in turn be filled. When blends are made the objective is to simultaneously optimize blend formulations, in respect of several properties important for a particular application, sacrificing those which are not important. 

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