Polypropylene ultimate tensile strength

Figure 5.119 Degradation of polypropylene under irradiation in air[ 13] Left ultimate tensile strength Right strain at break...

In many cases, plastics degrade in the presence of oxygen at irradiation doses that are without influence or result in crosslinking in vacuum. Because of oxidation, ultimate tensile strength and strain at break in polyethylene, polypropylene, polyvinyl chloride, polystyrene and in styrene-copolymers decrease faster with increasing doses when irradiated in air than when irradiated in a vacuum, whereas this is not the case for polyethylene terephthalate, polyvinyl alcohol, and acetyl cellulose. Oxidative degradation is also the reason for radiation damage doses that are notably smaller when irradiated in air than when irradiated in a vacuum [711],... 

Table 5.99 Physical characteristics of oil-resistant TPE-V based on copolymers made from crosslinked butyl acrylate and polypropylene after 21 days of exposure at 70 °C initial values compound 1 Shore A = 64, ultimate tensile strength = 3.8 N/mm, yield strain = 140%, compound 2 Shore A = 79, ultimate tensile strength = 5.8 N/mm, yield strain = 150%) [987]...

The mass fraction crystallinity of molded PHB samples is typically around 60%. As shown in Table 3, PHB resembles isotactic polypropylene (iPP) with respect to melting temperature (175-180°C), Young s modulus (3.5-4 GPa) and the tensile strength (40 MPa). In addition, the crystallinity of iPP is approximately 65% [18]. Accordingly, the fracture behavior of PHB may be anticipated to be tough at room temperature. Molded PHB samples do indeed show ductile behavior, but over a period of several days at ambient conditions, they slowly become more brittle [82, 85, 86]. Consequently, the elongation to break of the ultimate PHB (3-8%) is markedly lower than that of iPP (400%). 

In general, the tensile strength was found to be improved with perlite addition at higher radiation doses, especially for 15% and 30% perlite compositions. The ultimate elongation also decreased with addition of perlite and the radiation dose, but not as fast as observed in nnfllled polypropylene, especially when 50% perlite composites are considered. The impact strength, as can be expected, decreased with perlite addition for nonirradiated polypropylene composites, but it was found that gamma irradiation for both unfilled polypropylene and filled polypropylene did not much alter the impact strength. 

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