THERMAL-PROPERTIES OF SILANE-GRAFTED WATER-CROSS-LINKED POLYETHYLENE

Vinyl trimethoxysilane grafting reactions of low-density polyethylene (LDPE) were performed in an extruder, followed by crosslinking with bo iled water. The thermal properties of both silane-grafted and silane-g rafted water-crosslinked LDPE were investigated using differential sca nning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC data showed that the silane grafts on the LDPE molecules were thermal stab le in the absence of moisture under 130 degrees C under which the sila ne-grafted LDPE could be processed or recycled. The silane grafts on t he LDPE molecules reduced the melting point of LDPE and gave rise to a n endotherm shoulder at about 85 degrees C. TGA data showed that the d ecomposition temperature of the silane-grafted LDPE was much higher th an that of LDPE. It was demonstrated that the cause of the increase in the decomposition temperature was not due to the silane grafts but du e to the peroxide-induced crosslinking reactions during the silane gra fting reactions performed in an extruder. Silane-grafted water-crossli nked LDPE displayed multiple melting behavior resulting from phase sep aration during crosslinking of LDPE with water. The phase separation g ave rise to two melting points, including one at about 94 degrees C, a nd the other at about 107 degrees C. (C) 1998 John Wiley & Sons, Inc.