High rubber/polyamide blends

TPEs prepared from rubber-plastic blends usually show poor high-temperature properties. This problem could be solved by using high-melting plastics like polyamides and polyesters. But, often they impart processing problems to the blends. Jha and Bhowmick [49] and Jha et al. [50] have reported the development and properties of novel heat and oil-resistant TPEs from reactive blends of nylon-6 and acrylate rubber (ACM). The properties of various thermoplastic compositions are shown in Table 5.4. In this kind of blend, the plastic phase forms the continuous phase, whereas... 

Polyamides such as PA6 are engineering thermoplastics with high heat and solvent resistance properties and hence make ideal thermoplastic matrix candidates of choice to make high-performance TPVs with dynamically vulcanized mbber blends. Although nylon blends with low rubber content have been known for a long time as impact-modified nylons, as discussed under Sect. 19.7.1, elastomeric TPV blends of polyamide with high rubber content (>60 %) have not been commercially available until recently. Because of their higher thermal and chemical resistance performance, the polyamide-based TPVs have often been called super-TPVs (Leaversuch 2004). 

Polycarbonate is blended with a number of polymers including PET, PBT, acrylonitrile-butadiene-styrene terpolymer (ABS) rubber, and styrene-maleic anhydride (SMA) copolymer. The blends have lower costs compared to polycarbonate and, in addition, show some property improvement. PET and PBT impart better chemical resistance and processability, ABS imparts improved processability, and SMA imparts better retention of properties on aging at high temperature. Poly(phenylene oxide) blended with high-impact polystyrene (HIPS) (polybutadiene-gra/f-polystyrene) has improved toughness and processability. The impact strength of polyamides is improved by blending with an ethylene copolymer or ABS rubber. 

High-impact polystyrene (HIPS) is produced by polymerizing styrene in the presence of a rubber, usually poly(l,3-butadiene). HIPS has improved impact resistance compared to polystyrene and competes with ABS products at low-cost end applications such as fast-food cups, lids, takeout containers, toys, kitchen appliances, and personal-care product containers. HIPS as well as ABS and SMA are used in physical blends with other polymers, such as polycarbonates, polyesters, and polyamides, to improve impact resistance (Sec. 2-13c-3). 

The polymers mostly used in pharmaceutical packaging are polyethylene, polypropylene, PVC, polyamide, polystyrol, nylon, cellulose acetate, polyethylene terephthtalate, and blends thereof. Copolymers and rubbers are also used. The DSC melting curve of polyethylene used for packaging purposes is characteristic. Low- and high-density polyethylene are differentiated by their melting points. " Melting point and density of polyethylene are linearily correlated. " Crystallinity may be determined as described above for amorphous state. 

At present, there is only one commercial source of the polyamide/polycarbonate blends (Dexcarb , Dexter Corp.). According to their patent, the blend was compatibilized by using a combination of a polyesteramide elastomer and a maleated olefinic polymer, such as male-ated polypropylene or EP rubber [Perron, 1984 1988]. However the degree or the efficiency of compatibilization achieved is unknown, since the added components are not known to be miscible or compatible with the polycarbonate. Nevertheless, the data sheet indicated good properties including a high notched Izod impact strength of > 700 J/m (Table 15.24). 

The structure of EPDM grafted onto polyamide 66 was analysed with high resolution solid state carbon-13 NMR and IR spectroscopy. Details about the EPDM rubber include the amount of mbber incorporated into this blend, the sequence analysis of the EPDM mbber and an estimate... 

The above selective cross-linking of acrylate rubbers in a polyamide thermoplastic matrix leads to a PA-acrylate rubber-blend TPV with the melt-processing advantages of the PA and the high-performance properties of a thermoset acrylate rubber. The PA matrix provides the high heat resistance and solvent resistance while the cross-linked polyacrylate provides the rubber elasticity coupled with its own excellent weatherabdity and oil resistance properties to the TPV. 

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