TRANSIENT ELONGATIONAL VISCOSITY OF LLDPE LDPE BLENDS AND ITS RELEVANCE TO BUBBLE STABILITY IN THE FILM BLOWING PROCESS/

Transient elongational viscosity of Linear low density polyethylene (L LDPE) and its blends with 10% and 20% of low density polyethylene (LDP E) was measured at two temperatures by a constant strain rate elongati onal rheometer. In addition, the performance of the blends in the film blowing process was assessed in terms of bubble stability at two proc essing temperatures. An operating window for stable bubble production was determined. The elongational viscosity measurements on blends reve aled stronger strain hardening characteristics at a higher temperature of testing. These results correlate favorably with findings from a bu bble stability investigation where it was found that the size of the o perating window for stable bubble production increased with increasing extrusion temperature. This work seems to indicate that increasing pr ocessing temperature during the film blowing of LLDPE-rich blends coul d lead to a processability improvement of these blends as far as bubbl e stability is concerned.