The Effect of Radiation-Induced Cross-linking on Loss of Chimassorb 944 from Polyethylene/Ethylene-Vinyl Acetate Blend in Hot Water

Loss of a high molecular weight hindered amine light stabilizer (HALS) from irradiated low density polyethylene-ethylene vinyl acetate blends (LDPE/EVA) in hot water has been investigated. The effects of Chimassorb 944 and two trifunctional monomers, triallyoxy-1,3,5-triazine and 2-ethyl-2-(hydroxymethyl)-1,3-propandiol trimethacrylate on LDPE/EVA properties after irradiation and on migration of stabilizer from the polymer base during thermal aging in hot water have been studied. The samples in both pure form and mixed with additives were exposed to electron beam radiation at doses between 50 and 150 kGy, at room temperature, in air. In order to study the thermal aging property, irradiated samples were placed in hot water bath at 95ºC for 1000 h and in an oven at 140ºC for several hours. Irradiated samples showed noticeable changes in mechanical properties. Long term heat stability of polymer blend was improved significantly by using of polyfunctional monomers. From the results of the thermal aging procedures, the HALS showed a convenient influence on the increasing of the polymer blend thermal stability at 95ºC. However in the accelerated condition, the value of oxidation induction time (OIT) decreased as a result of depletion of HALS from the polymer base during the immersion in hot water.