Weight Swelling Ratio Research Articles

Protection effects of condensed bromoacenaphthylene on radiation deterioration of ethylene–propylene–diene rubber

AbstractAs a continuation of a series of the studies on the flame and γ‐radiation resistant modification of ethylene–propylene–diene rubber (EPDM), condensed bromoacenaphthylene (con‐BACN) as a newly developed flame retardant was synthesized and its effects on the radiation resistance of EPDM were investigated. The radiation resistance evaluated by measuring tensile properties of irradiated sheets of 2 mm thck was found improved greatly by adding con‐BACN together with ordinary rubber ingredients but decreased by decabromodiphenylether (DBDPE) that has bromins in aromatic rings as con‐BACN. When EPDM sheets of 1 mm thick were irradiated in oxygen at a dose rate of 1 × 105 rad/h, the weight swelling ratio increased with increasing dose, indicating that oxidative main chain scission is predominant under the irradiation conditions. On the other hand, crosslinking was shown to be predominant in nitrogen. From the results of the swelling experiments with different additives, it was concluded that DBDPE accelerates both the main chain scission in oxygen and the crosslinking in nitrogen. In contrast to this, con‐BACN reduced the chain scission in oxygen. This observation was accounted by the assumption that the influence of the oxidative chain scission is partly compensated by the concurrent crosslinking which takes place through additions of con‐BACN to substrate polymers even in the presence of oxygen.

Effect of Acetylene on the γ-Ray Crosslinking Polymerization of Various Kinds of Acrylic Monomers

Abstract The γ-radiation-induced crosslinking polymerization of methyl methacrylate (MMA), methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA), methyl acrylate (MA), and acrylic acid (AA) was carried out in bulk. The polymerization rates of AA and HEMA were much larger than those of other monomers. Acetylene had no influence on the polymerization rate in the initial stage, and the rate was dependent only on the kinds of monomers. In the absence of acetylene, gelation took place in PMA, PAA, and PHEMA obtained at complete conversion, but not in PMMA and PMAA. By the addition of acetylene, complete gelation of PMMA was observed, but no gel formation was observed for PMAA. Volume and weight swelling ratios were measured for PMA, PAA, PHEMA, and PMMA with complete gelation. It was found that by the addition of acetylene the molar concentration of crosslinks increased as much as about twice for PMA and PHEMA, and over about one hundred times for PMMA AND PAA. The relation between volume Sv and weight swelling ratio Sw was studied theoretically. Sv was expressed by the the equation, Sv = (pp /p+)Sw+ (1 -pp/ps), as a function of Sw and the densities of pure polymer (pp) and solvent (ps) in swollen polymer.