Thermoplastic alloying

The sales of plastics continue to increase in a large part due to technical and economic advancements of polymer blends. Reactive blending is a useful technique for elastomers but, it appears that chemistry could also play an important role in the correct microstructure adjustment of thermoplastic alloys. Interfacial reactivity should be the focal point in maintaining the expected structure during subsequent stages of manufacture. Besides industrial examples, various kinds of polymeric co-reacting systems are also presented in order to emphasise the key factors of reactive blending. 

Vandar . (Hoechst Cdanese/Ei ineer-ing Plastics Hoechst UK] Thermoplastic alloy (elasttHner-modUlfiedPBT), some glass or mineral filled used for automotive body conqxments and housings, furniture, ski boots, tqq>liances, clips, fasteners. 

Xenoy . [GE nasties GE Plastics Ltd.] Thermoplastic alloys, some glass reinforced for biow molding, structural foam tpplics., automotive exterku body parts, fluid handling equip., medical prods., Ughtweight lawnmower casings. 

Thermoplastic alloys based on styrene maleimide with PA have good thermal stabUity, chemical resistance, abrasion resistance, paintability and weatherability. Those blended with ABS combine thermal resistance with very good processabUity. The alloys find use in various automotive components such as defroster grills, door handles, and headlamp surrounds. 

Commercially important elastomeric thermoplastic alloys are dynamically vulcanized blends of polypropylene with high volume fractions of EPDM, polybutadiene rubber, nitrile rubber, and butyl rubber (Santoprene , Vyram , Geolast and Trefsin ) all currently sold by Advanced Elastomer Systems, a joint venture of Monsanto and Exxon. Another recent member of the commercial dynamically cured elastomeric thermoplastic alloys is the blend of PVC and a crosslinked ethylene copolymer (Alcryn , DuPont). The current consumption of all the elastomeric thermoplastic alloys in the USA is over 23 kton/y, with the EPDM/PP blend (Santoprene ) assuming about 90% of the market share. 

BFGoodrich Specialty Chemicals produces a family of thermoplastic alloys that are inherently conductive. Alloys with 15% of the active conductive polymer differ little in surface resistivity from alloys with 25% active polymer. Further, the conductive polymer content remains relatively constant through processes such as injection molding, extrusion, and thermoforming, unlike resins containing conductive fillers. In contrast to chemical antistats, the conductive polymers are active at all humidity levels, do not lose their potency over time, and add no ionic contaminants to the surrounding atmosphere. 

ABS nylon alloy A thermoplastic alloy of acrylonitrile-butadiene-styrene plastic (ABS) and nylon (PA) with properties similar to ABS but witb bigber elongation at yield. See acrylonitrile-butadiene-styrene plastic nylon plastic. 

Make note of this COLOR SELLS If you want a new high performance thermoplastic alloy or blend to reach the widest number of appropriate end user markets, you have to be able to color it in a cost effective manner that does not harm its performance properties. Barriers to cost effective coloring include ... 

Thermoplastic alloy of styrene maleic anhydride copolymer and polybutylene terephthalate. Has improved dimensional stability and tensile strength. Processed by injection molding. Also called SMA PBT Alloy. 

Research to develop jute and kenaf fiber thermoplastic alloys is based on first thermoplasti-cizing the fiber matrix as described above, followed by grafting of the modified fiber with a reactive thermoplastic. This type of composite has the thermoplastic bonded onto the jute or kenaf so there is only one continuous phase in the molecule. This is done in one of two ways. In one case, the matrix is reacted with maleic anhydride that results in a double bond in the grafted reacted molecule. This can then be used in vinyl-type additions or in free radical polymerization to either build a thermoplastic polymer or graft one onto the jute or kenaf backbone. In the second method, the matrix is reacted with a bonded chemical and then reacted with a low-molecular-weight thermoplastic that has been grafted with side-chain anhydride groups. 

Dynamically vulcanized, elastomeric thermoplastic alloys or TPVs display properties as good as or even better than the block copolymers, viz., a high degree of rubber elasticity yet good melt processability. The main advantages of the thermoplastic vulcanizate elastomer blends over the uncured thermoplastic/elasto-mer blends are... 

Garaprene Thermoplastic alloy compounds Evode Plastics Ltd. 

Plastiblend, Injection moldable thermoplastic alloys, TP Composites, Inc. 

Xenoy, Thermoplastic alloys, GE Plastics XRC Bushing, Externally heated hot runner bushings, Incoe Corp. 

Among thermoplastics alloys the combination of PP and PET offers some advantages over the pure components. PET may enhance the stiffness of PP at higher temperatures while the polyolefin could facilitate PET crystallization. Non-compatibilized and compatibilized PET/PP blends were prepared. Main compatibilizers used were PP-acrylic acid copolymer, maleic anhydride modified PP (PP-g-MA), hydrogenated SBS block copolymer (SEBS-g-MA) and linear low-density polyethylene (LLDPE-g-MA) (34). 

Improving mechanical properties such as toughness usually serve as the main reasons for the development of novel thermoplastic alloys and blends [4]. Other reasons for blending two or more polymers together include (i) to improve the polymer s processability, especially for the high-temperature polyaromatic thermoplastics (ii) to enhance the physical and mechanical properties of the blend, making them more desirable than those of the individual polymers in the blend and (iii) to meet the market force (cost dilution). Most products succeed because of a beneficial combination or balance of properties rather than because of any single characteristic. In addition, a material must have a favorable benefit-to-cost relation if it is to be selected over other materials for a particular application. One key technical issue is whether the blend will exhibit additive properties, or not. In many cases properties are well below additive, while in others they may be above additivity. The property relationships exhibited by blends depend critically on the correct control of their phase behavior [3]. 

Janoff, Vicic, and Cain [11] used accelerated life test methods to select the best material to use for lip seals used in water/glycol fluids contained in subsea oil-field hydraulic systems. The required seal life was 20 years at 93°C sustained temperature at 20.7 MPa pressure with 100 mechanical operations. Finite Element Analysis was used to determine the actual seal temperature in the installed component to establish the service temperature rating. Polyurethane and thermoplastic alloy seals were tested in water/glycol and hydrocarbon hydraulic fluids at 3—5 elevated temperatures at 20.7 MPa constant pressure. Failure was defined as seal leakage at pressure. Test results were analyzed using Least Squares regression in an equation like that used by KenneUey et al. The correlation coefficients exceeded 0.95 and show excellent fit to the model. Table 16B.1 shows the results of the study. 

Another result of mixing two materials—and in many ways this is the preferred result— is that the two materials will have chemical affinity for one another, and will combine to form a new material with properties greater than the sum of the parts. This is a thermoplastic alloy. In a similar manner to how alloys of iron and carbon (steel) or of copper and tin (bronze) enabled new products and technologies in the Age of Metals, thermoplastic alloys opened an entire spectrum of new possibilities in the Age of Plastics. The combination of material variations, additives, possible alloys, and potential new applications is virtually unlimited. The next breakthrough thermoplastic material may very well be right in front of you. 

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