Effect of Sample Configuration on the Morphology of Foamed LDPE/PP Blends Injection Molded by a Gas Counterpressure Process

Abstract

Blends of isotactic poly(propylene) and low‐density polyethylene with different composition ratios were prepared through direct melt compounding on a twin‐screw extruder. The specimens with various geometric configurations were injection‐molded using a gas counterpressure process, using blends to which 0.5 wt.‐% of a blowing agent was added. The influence of blend composition and specimen geometry on the structure and morphology of the samples was investigated by SEM and WAXS. The thermal behavior of the blends was analyzed by DSC. It was found that the morphology of each region depended on the composition ratio and specimen geometry.magnified image

Influence of relative low gas counter pressure on melt foaming behavior and surface quality of molded parts in microcellular injection molding process

“…Kotzev et al. 25 investigated the influence of blend composition of LDPE/PP composite material and specimen geometry on the cell structure and morphology in the specimen, it was found that when the mixed ratio of LDPE/PP equals to 25/75, a microcellular injection molding specimen with good cell morphology can be obtained. Chen et al.…”

“…In recent years, some researchers combined gas counter pressure (GCP) process with microcellular injection molding process to improve the surface quality of microcellular injection molded parts on the premise of cost control. [24][25][26][27] For conventional microcellular injection molding process, the pressure of melt flow front is almost constant and equal to atmospheric pressure. But in GCP microcellular injection molding process, the pressure of melt flow front is not constant but dynamic.…”

“…For GCP microcellular injection molding process, Bledzki et al 24 studied the influence of GCP process and precision mould opening process on cell size and mechanical properties of microcellular injection molded parts for different materials. Kotzev et al 25 investigated the influence of blend composition of LDPE/PP composite material and specimen geometry on the cell structure and morphology in the specimen, it was found that when the mixed ratio of LDPE/PP equals to 25/75, a microcellular injection molding specimen with good cell morphology can be obtained. Chen et al 26,27 developed a foaming control system by using GCP process and mould temperature control technology.…”

Polyolefinic nanocomposite foams: Review of microstructure-property relationships, applications, and processing considerations

“…Controlled distribution of voids along the thickness of the foamed part, including formation of an aesthetic skin is an important aspect of foaming when considering injection foaming [147][148][149][150] (especially core-back injection foaming 124,141,[143][144][145] ), foam blow moulding, 151 or foamed pipes. Pinto et al 152 reported a novel route to produce foams with controlled skin thicknesses via controlled by gas diffusion.…”

Morphological analysis of microcellular PP produced in a core‐back injection process using chemical blowing agents and gas counter pressure

“…Bledzki et al [15] analyzed the influence of GCP process on cell size and mechanical properties of microcellular injection molded parts for different materials, using both Chemical Blowing Agents (CBA) and Physical Blowing Agents (PBA). Kotzev et al [16] analyzed the morphology of foamed LDPE/PP blends injected with a counter pressure process. Jahani et al [17] analyzed the morphology and acoustical properties of open-cell foams using core-back and high GCP values (up to 10 MPa).…”