Thesis (M.Sc.)--Chulalongkorn University, 2001

In this research, scrap of LLDPE film after processing from blown film process will be recycled by the addition of antioxidant at various concentration. Then, the effects of its concentration and efficiency related to reduction of gel contents on film was studied. The compounded masterbatch of phenolic antioxidant, octadecyl 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene propanoate (Irganox 1076) and phosphite type, tris(2,4-di-tert-butylphenyl) phosphite (Irgafos 168) as it called polybatch AO-25 masterbatch was blended with scrap LLDPE at concentration of 3, 8, 15, 25, 40 phr. Furthermore, each formulation was used to prepare a film sheet using the blown film process and the gel counting, mechanical properties and yellowness index (YI) were studied. It was found that addition of polybatch AO-25 reduced the gel contents when compared with unfilled formula. It was observed that there was no longer decreasing of gels on film when polybatch AO-25 was at 15 to 40 phr. However, the value of mechanical properties and yellowness index became less and more when the contents of polybatch AO-25 was increasing. Consequently, addition of virgin grade LLDPE into these formulations could be a solution. From the testing results, using polybatch AO-25 8 phr blended with 25% virgin grade LLDPE was the most effective to provide low gel contents, good mechanical properties and low yellowness index.