Effect of electron beam radiation on tensile and viscoelastic properties of styrenic block copolymers

Abstract

The effect of electron beam (E-beam) radiation on a series of styrenic block copolymers (SBCs) was investigated. These SBCs included newly developed poly(styrene-blockisoprene/butadiene-block-styrene) (SIBS), poly(styreneblock-butadiene-block-styrene) (SBS), and poly(styreneblock-isoprene-block-styrene) (SIS). The tensile properties, stress relaxation, molecular weight, and dynamical mechanical properties were studied. Generally, the crosslink density and tensile moduli of SBCs increased with increasing of E-beam radiation dose. The tensile strength of SIBS and SIS was shown to first decrease at lower E-beam radiation dose (<120 kGy) and then increase at higher radiation dose (>190 kGy). The tensile strength of SBS was significantly decreased at high E-beam radiation dose (>190 kGy). This was attributed to the differences between entanglement before E-beam radiation and the homogeneity of the crosslink network after exposure. EXPERIMENTAL MaterialsSBCs synthesized by anionic polymerization were provided by Kraton Polymers, Houston, TX. The detailed information of SBCs is listed in Table 1. Polybutadiene (20% vinyl; 80% cis-and trans-1, 4, M n 6 k) and polyisoprene (cis-1,4, M n 17 k) were purchased from Sigma-Aldrich. Polystyrene was obtained from Americas Styrenics, Marietta, OH with product No. of D4030.01. Solvents were purchased from Sigma-Aldrich

Sulfur-Free Prevulcanization of Natural Rubber Latex by Ultraviolet Irradiation in the Presence of Diacrylates

“…Coagents with mono-, di-, or poly-functional reactive groups with either abstractable hydrogen or double bonds can be used to aid the free radical production . The coagent radicals react with the carbon–carbon double bonds in NR molecules to form covalent cross-links. , Although sufficiently energetic radiation (e.g., electron beams and γ rays) can generate free radicals directly from a suitable coagent, − the use of such radiation is unattractive because of safety considerations and the expensive equipment needed. An alternative is to use weaker radiation such as ultraviolet (UV) light to generate radicals .…”