and antioxidant can be fed separately or they can be combined and fed in as a compound to the feeding zone after the feeding zone there is a melting zone followed by a metering zone and finally a mixing zone the physical blowing agent is injected through the feed nozzle between the metering and mixing zones after exiting from the mixing zone of the first extruder the melt passes through a pipe which connects the first and second extruders and enters the second extruder in the second extruder the melt is cooled down to an appropriate temperature to allow it to exit the die assembly as a foam via the circular die the foamed sheet exiting the circular die is about 1000 mm in width 10 mm in thickness and 30 times in its expansion ratio in the experiments which follow the residence time in the first extruder is calculated to be about six 6 minutes the resin is a low density polyethylene known as petrothene na952 by quantum chemical corp which has a melt index of 2 0 g 10 min and a density 0 918 g cm 3 its feed rate is 200 kg hr the physical blowing agent is iso butane and its feed rate is 25 28 kg hr the nucleating agent is mistron from cyprus ind minerals which comprises 70 low density polyethylene and 30 talc and its feed rate is 1 0 kg hr as talc the aging agent is atmul 918k from humko chemical which is glycerol monostearate and its feed rate is 2 2 kg hr in each of the seven 7 runs listed below a 1 to a 7 inclusive a different peroxide is indicated listed.