Process stabilization of HDPE

HDPE Compounding was done with a twin-screw extruder at 220Deg C,300rpm
and nitrogen(1,5 bars) was used to make the compounding step
as inert as possible.
HDPE powder and additives were mixed mechanically before compounding.
Multiple extrusions were done with a single screw extruder under air atmosphere at 260 Deg C.
Table a shows the melt flow ratio and yellowness index of HDPE stabilised by 0.025%
AO-1 in combination with 3 different phosphites.
It is well known that HDPE can undergo crosslinking as well as chain scission
during processing and significant changes in molecular weight distribution can result.