Thesis (M.Sc.)--Chulalongkorn University, 1999

Recycling of polyethylene resins to reduce waste problems in environment and to save cost of the production in film industry was carried out. The effect of virgin high density polyethylene (HDPE)/recycled polyethylene resin composition on the morphology and mechanical properties of the blended films was investigated. The recycled polyethylene resin was obtained from a post-consumer cyclate of HDPE film, HDPE bottle, and low-density polyethylene (LDPE) resin. Based on the statistical evaluation of the type of PE on tensile properties and morphology, it was found that the recycled LDPE affected both properties. In addition, the thermal properties, the viscoelastic properties and the flow behavior as melt flow index (load 2.16 and 5 kg/190 ํC) and flow curve were investigated for film processability. The stress at break, stress at yield and elongation at break, stress at yield and elongation at break decreased with increasing the recycled LDPE amount while the elongation at yield did not affect the film properties significantly (14.00-16.67%). Morphology of the blended films is composed of the crystalline region shown as brignt fibrils and the amorphous region as narrow dark fibrils. The whole region was confirmed by X-ray diffraction (XRD) which determined the crystalline and amorphous domains. Incrasing the amount of recycling LDPE decreased % crystallinity. The amount of crystallinity was determined indirectly as heat of fusion by differential scanning calorimetry (DSC). The extent of crystallinity and heat of fusion are in a direct relation. Additionally, increasing the concentration of recycled LDPE decreased the crystallinity of plastic film from 78% to 67%, and tensile property (MD) decreased from 27 MPa to 17 MPa.