Commodity resins, blends

Engineering resins can be combined with either other engineering resins or commodity resins. Some commercially successhil blends of engineering resins with other engineering resins include poly(butylene terephthalate)—poly(ethylene terephthalate), polycarbonate—poly(butylene terephthalate), polycarbonate—poly(ethylene terephthalate), polysulfone—poly (ethylene terephthalate), and poly(phenylene oxide)—nylon. Commercial blends of engineering resins with other resins include modified poly(butylene terephthalate), polycarbonate—ABS, polycarbonate—styrene maleic anhydride, poly(phenylene oxide)—polystyrene, and nylon—polyethylene. 

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. 

The largest group comprises the impact modified PEST s — these were summarized while discussing commodity resin blends. The commercial blends with, e.g., SMA or acrylic rubber, show good processability, rigidity, impact and tensile strength, as well as excellent weatherability, viz. Arloy 2000, Bexloy , Celanex , Pibiter HI, Rynite , Ultradur KR. 

Table 10.5. Forming methods for commodity resin blends polyolefins-based blends...

Table 10.7. Forming methods for blends of commodity resins - Others...

This section aims at discussing the conditions and recommendations for successful extrusion of blends containing commodity resins as the major component. The conditions recommended by manufacturers are hsted in Table 10.19, while the recommended procedures and accepted practices are discussed below for each type of blend. 

Table 10.19. Extrusion conditions for commodity resin blends...

Blends of Other Commodity Resins Acrylic-based blends (Acrylite , Cyrolite and XT) are often used to extrude sheets for applications where transparency is important. Thus, to ensure clarity, it is important to avoid contamination. The combination of long residence time and high temperature will increase viscosity leading to gel-like skin, with loss of gloss and transparency. Orientation in the final product should be kept below 25%. Suitable screws should have... 

Injection molding conditions of blends of polyolefin resins and other commodity resins are listed respectively in Tables 10.25 and 10.26. The conditions represent an average for each type of blend. They usually vary slightly from one grade to another. Recommended practices and specific comments are discussed below for each type of blend. 

Table 10.26a. Injection molding conditions of blends of other commodity resins — Part A...

Numerous blends based on PC have been developed for injection molding applications. Amongst the blends with commodity resins, styrenics have found the widest applications, particularly the blends with ABS. 

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. 

Costs can be reduced by blending engineering thermoplastics (ETPs) with less expensive commodity resins. Also, the distinction between plastics and elastomers can be breached by PAB s and is in fact narrowing. 

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. 

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