Engineered plastics Blends

The physical blend of PDLA and PLL A can be used in other applications, such as woven shirts with better ironability, microwavable trays, hot-fill applications and even engineering plastics (blends with rubber-like polymers such as ABS). PLA is also currently used, like PGA, in a number of biomedical applications, such as sutures, dialysis media, drug delivery devices and tissue engineering. 

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. 

Table 9 compares the most important properties of substrate materials based on BPA-PC, PMMA, and CPO (three different products) (216,217). The future will prove if the current disadvantages of CPO against BPA-PC regarding warp, processibiUty (melt viscosity), and especially cost can be alleviated. CycHc polyolefins (CPO) and, especially cycloolefin copolymers (COC) (218) and blends of cycloolefin copolymers with suitable engineering plastics have the potential to be interesting materials for substrate disks for optical data storage. 

Blend of (1) and (2) type categories mostly include the modification of engineering thermoplastics with another thermoplastic or rubber. PS-EPDM blends using a low-molecular weight compound (catalyst) Lewis acid have been developed [126]. Plastic-plastic blends, alloys of industrial importance, thermoplastic elastomers made by dynamic vulcanization, and rubber-rubber blends are produced by this method. 

Polyarylate (PAR)-b-PSt and PAR-b-PMMA for compatibiiizers are described 135,39,40). The addition of PAR-b-PSt (1-10 parts) to 100 parts of a blend of PAR-PSt (7w-3w) resulted in improvement of the tensile and flexural modulus (Fig. 4), and PSt dispersed particles were diminished from 1-5 microns to an order that is undetectable by SEM, indicating the excellent, compatibilizing effect of the block copolymer. The alloy thus formed exert the characteristic of PAR, an engineering plastic, as well as easy processability of PSt. Addition of PAR-b-PMMA (3 or 8 parts) to 100 parts of a blend of PAR-polyvinylidenefluoride (PVDF) (7w-3w) resulted in improved microdispersed state of PVDF due to compatibility of PMMA with PVDF, while segregation of PVDF onto the surface was controlled. 

The additive analysis reported has been largely confined to conventional polymers (polyolefins, polycondensates, PS, PVC, etc.) Very little work, if any, has been reported on advanced engineering plastics. Similarly, also relatively little research activity has focused on additives in acrylics or blends. 

Several flexible polymers, such as natural rubber (NR) synthetic rubber (SR) polyalkyl acrylates copolymers of acrylonitrile, butadiene, and styrene, (ABS) and polyvinyl alkyl ethers, have been used to improve the impact resistance of PS and PVC. PS and copolymers of ethylene and propylene have been used to increase the ductility of polyphenylene oxide (PPO) and nylon 66, respectively. The mechanical properties of several other engineering plastics have been improved by blending them with thermoplastics. 

To conclude the above methods of incorporation of modified lignin in polymer networks and blends opens new promising possibilities for the technical use of lignins and makes it competitive with other raw materials for engineering plastics. 

To the range of engineering plastics were added polyethylene and polybutylene tereph-thalates (PET and PBT), as well as General Electric s polyethers, the PPO (polyphenylene oxide) produced through polymerization of 2,6-xylenol and the Noryl plastic produced by blending PPO with polystyrene. Other special polymers, derived like the polycarbonates from bisphenol A, were added to this range polyarylates, polysul-fones, polyetherimides. 

In situ polymerisation may have wide applicability in preparing blends of polymers such as engineering plastics which have few solvrats. Because the solvents interact strongly with the polymers they are more likely to induce phase separation. This has been shown to be true for PVC which also has few solvents. 

We note that the phase diagrams for PLC-containing blends are more complicated than those of ordinary engineering plastics. For PLCs additional phases have to be taken into account since the PLCs themselves may exhibit complex polymorphism. 

Electrical and electronic products such as computers, cell phones, TVs, and stereos are becoming a more visible part of the MSW. Some of the resins used in electronic products are PS, HIPS, ABS, PC, PP, PU, PV, PVC, polyamides, phenol formaldehyde, and blends of some of these polymers. Several technologies are being developed for the separation of different plastic types. Since the electronic parts are made from many engineering plastics, and with many different additives, it is more difficult to identify and separate the individual resins. 

Finally, it has been stated that this new toughening technique can be safely extended to other fragile plastics, such as PVC and PS (38). This observation supports that a properly tailored diblock copolymer can help in generating materials with highly improved properties. Engineering polymer blends... 

Polyamide-6 (PA-6) and polypropylene (PP) are both semi-crystalline polymers and the combination of an engineering plastic (PA) and the best commodity product (PP) could lead to new blends with Interesting Intermediate properties. We tested systems containing 50 wt% of each product and the ones obtained by addition of 3% of the reactive PP-g-AM resulting from previous continuous grafting in the extruder. The blends were prepared by simple mixing in the ZSK 30 twin-screw extruder and the samples for mechanical testing were molded by injection in a BILLION equipment. 

Fortunately, the deficiencies of both the classic thermosets and general purpose thermoplastics have been overcome by the commercialization of a series of engineering plastics including polyacetals, polyamides, polycarbonate, polyphenylene oxide, polyaryl esters, polyaryl sulfones, polyphenylene sulfide, polyether ether ketones and polylmides. Many improvements in performance and processing of these new polymers may be anticipated through copolymerization, blending and the use of reinforcements. 

It has been estimated that 15 to 20 percent of all engineering plastics produced in the United States today are polymer blends or alloys, which are physical mixtures of homopolymers and/or copolymers. A serious problem exists, however, in that the bulk properties of the blend will depend on the degree of mixing achieved. Such mixing is difficult to accomplish on the molecular level and... 

Styrenics and Engineering Plastics ethylbenzene, styrene, polystyrene, SAN, ABS, alloys and thermoplastic blends ... 

Many of the practical examples of miscible blends involve poly(vinylchloride) including those with butadiene-acrylonitrile copolymers2), possibly the first put into use, and various poly acrylates and vinyl acetate copolymers3,4) which are extensively used in PVC formulations at present. Others involve high performance engineering plastics such as blends of polystyrene with poly(2,6-dimethyl-1,4-phenylene oxide) (Noryl )5). In some cases a useful compromise or averaging of properties can be obtained whereas in others a useful combination of different desirable properties can be achieved. 

---