Commercial Engineering Polymer Blends

As noted earlier, the first major engineering polymer blend was poly(2,6 dimethyl-1,4-phenylene oxide) (PPO) with impact polystyrene. PPO and polystyrene exhibit miscibility over the entire composition range and thus mechanical compatibility. PPO/impact polystyrene blends were commercialized by General Electric in the late 1960s [52, 53] under the trade- 

PC/ABS Bayblend Bayer Office equipment, battery chargers, AC adaptor. 

PC/PBT Xenoy GE Lawn and garden equipment, sports equipment 

PC/PMMA Cyrex Gyro Medical devices, toys, appliances, portable phone and pager housings,. 

---

Figure7.1 Commercial engineering polymer blend combinations...

Although commercial twin-screw extruders can be as large as 300 mm size, capable of compounding up to 40 ton/hr, the acmal type and size of the equipment used depends on the type of the polymer blend and the production volume. Normally, for engineering polymer blends, twin-screw extmders of about D = 90 mm size (L/D = 30 to 40) and capable of compounding at 700 to 1000 kg/hr, are used. For blending PVC or elastomer blends other types of compounding equipment are used, e.g. Farrell continuous mixer (FCM), Buss co-kneader, or a batch mixer, such as Banbury. 

In the engineering polymer blends, a number of advances in the technology and the commercial areas have been realized in the past decade. New commercial polymers have been manufactured by various combinations of preexisting polymers. One of the major areas has been with polyesters and polycarbonates (polybutyleneterephthalate/ polycarbonate polyethyleneterephthalate/polycar-bonate polyarylate/polycarbonate cyclohexane dimethanol based polyesters/polycarbonate). 

The last several decades have seen an exponential increase in the activity of engineering polymer blends. While this activity will continue, the area that will probably show the most future increase in commercial activity will be in high temperature systems. These blends include LCP and molecular composites as subsections that will be discussed separately. The activity in high temperature polymer blends has been primarily in the patent and published literature. Several examples of developmental and specialty commercial blends have emerged and many more are expected to follow in the future. 

Table 7.2 Commercial Examples of Engineering Polymer Blends...

Most of the work to date concerns the area with the greatest potential for commercial exploitation, the blending of LCPs with conventional polymers. While a few studies of solution blending with Kevlar do exist [57-61], most of the work has centered on melt blending thermotropic copolyesters (Vectra, Xydar) with engineering thermoplastics (PET, PC, PEI, etc.). For convenience, this work may be separated into three blend regions based on LCP content, namely ... 

Chemical engineers have worked with polymers since the first Bakelite articles were produced early in this century. Since then, the class of polymeric materials has grown to encompass a whole range of thermoset and thermoplastic resins, as well as copolymers and polymer blends, and chemical engineers have played major roles in the rise of these materials to commercial success. From production of the resins (which involves heat and mass transfer, kinetics, fluid dynamics, process design, and control) to the fabrication of final articles (involving many of the same processes, as well as some unit operations not part of traditional chemical engineering, such as extrusion... 

In the future, prospects for combining engineering polymers with the lower cost commodity polymers should lead to unique cost/performance systems. Potential combinations might include PC/PP, polyester (PBT, PET)/PP and POM/PP or HOPE. Newer commercial polyamides (PA-46 Amodel (Amoco) aliphatic/aromatic polyamide) should also be off interest in new blend combinations. An example of this involves Amodel/ PPS blends as noted by Chen and Sinclair [1997]. Although the rate of introduction of new engineering polymers has decreased, new additions will be continued to be expected and thus new blend combinations will also be offered. 

The most recent addition to the engineering polymer field is the ethylene/carbon monoxide (COPO) alternating copolymers initially introduced by Shell. The commercial polymer is highly crystalline and believed to contain small amounts of propylene to reduce the crystalline melting point to allow a broad window of process-ability. COPO should offer serious competition to polyacetal, PA, and PBT. With the favorable raw materials cost, COPO should be a successful and competitive entry. As is now expected with new polymers, intense blend patent activity accompanies the introduction. This has also occurred with COPO as is noted in various U.S. patents involving COPO blends (See Table 17.4). COPO polymers are available from Shell (Carilon ) and BP (Ketonex ). 

---