A study of foam extrusion using a chemical blowing agent

Abstract

SynopsisAn experimental study of foam extrusion was carried out to determine the effect of processing variables on the quality of the foam produced. For the study, the chemical blowing agent azodicarbonamide was used, together with an activator and a nucleating agent, to produce thermoplastic foams of low-density polyethylenes. The quality of foam was determined from photomicrographs and the tensile properties of extrudate samples. It was found that the percent elongation correlates with the foam density and that the cell structure (cell size and its distribution) correlates with the ultimate tensile properties of the foam produced. Also, an experimental study was carried out to observe the growth of gas bubbles as the polymer melt containing a blowing agent flows through a rectangular channel constructed of quartz. This experiment helped us to interpret the curued pressure profile of the polymer melt containing a blowing agent as the melt approaches the die exit, whereas the polymer without a blowing agent shows a linear pressure profile.

Rheological behavior of a microcellular, oil‐extended ethylene–propylene–diene rubber compound: Effects of the blowing agent curing agent, and conductive carbon black filler

“…The total extrusion pressures of Vulcan XC72 filled, microcellular, uncured and cured compounds are 4 12.296 130 62 EB 5 12.296 130 80 EB 4 12.296 140 87 EB 5 12.296 140 113 EB 6 12.296 140 54 EB 7 12.296 140 76 EB 8 12.296 140 88 EB 7 7.685 140 93 EB 7 23.055 140 60…”

“…[3][4][5] They concluded that the bubble size and void fraction increase with temperature, reducing the extrusion rates and die length/diameter ratio under constant extrusion rate conditions. An important aspect of foam extrusion is the mechanics of bubble growth in the polymer matrix.…”

Rheological Properties of Gas-Containing Thermoplastic Materials During Extrusion

“…If we further assume that the gas bubbles in each cross section have enough time to grow to equilibrium dimensions at any pressure below the critical level (P < Per), the ~p quantity in Equation (8) can be determined with the aid of the following equation:…”

The morphology, mechanical properties and ageing behavior of porous injection molded starch-based blends for tissue engineering scaffolding

“…Studies of bubble development and morphology of polymers in foaming extrusion processes and the effect of processing variables on the quality of the produced foams have been reported by several authors [3][4][5].…”