Microcellular Plastics

Abstract

Microcellular plastics are typically thermoplastic polymers with a large number (∼billions per cm3) of tiny bubbles (of the order of 10 μm in diameter). Their densities can range from 3% to 95% of the solid polymer depending on the volume taken by the bubbles (which are denoted as cells in this paper). In general, microcellular plastics exhibit superior impact strength, toughness, fatigue life, thermal stability, dielectric strength, thermal and acoustical insulation performance, as well as optical properties, relatively to the solid counterparts. Other advantages of microcellular plastics include higher productivity due to its faster processing times and sink‐mark free injection‐molded parts with no residual stress and high dimensional stability. Owing to these unique properties, there are a large number of applications of microcellular plastics, particularly in automotive industries. This article summarizes the science and technology of microcellular plastics. To be specific, their history, science (ie, generation of polymer–gas solution, cell nucleation, growth, deterioration and stabilization), solid‐state processing technologies, continuous processing technologies (ie, extrusion and injection molding), design guidelines of each processing technologies, as well as the properties and application of microcellular plastics, are discussed in detail.

Advances in microcellular injection moulding

“…Therefore, with the higher density of cells obtainable through MIM insulating properties can be enhanced. 1 Wang et al 143 have developed a mathematical model of thermal transport through nano-cellular polymers. The research concludes that nano-cellular polymers are a super insulating material due to the high infrared absorption capacity and the infrared reflectance on the cell walls.…”

“…In the early 1980s, the Massachusetts Institute of Technology (MIT) invented microcellular processing in the industry polymer processing programme. 1 The aim of this project was to reduce material usage, reduce final part weight and modify the resulting material properties through the introduction of small spherical cells into the polymer-based products. 2 The initial publications and theses from this research institute discovered the proof of concept and advanced the fundamental theories behind the technology.…”

A Novel Hybrid Foaming Method for Low-Pressure Microcellular Foam Production of Unfilled and Talc-Filled Copolymer Polypropylenes

“…Polypropylene (PP) is regarded as one of the most popular polymers used in polymer industry due to low material cost, excellent chemical resistance, low density and high heat distortion temperature [16]. The first stage of FIM is super critical fluid (SCF) dissolution into the polymer melt [17]. Semi-crystalline polymers, such as PP, exhibit poor SCF dissolution due to the special interference between crystalline lamella being smaller than the SCF molecules [11] which means that the single-phase solution is not formed correctly.…”

Foaming of PLA Composites by Supercritical Fluid-Assisted Processes: A Review

“…Microcellular batch processing technology was invented by Jane Martini [118], from 1980 to 1984 at the Massachusetts Institute of Technology (MIT). The first U.S. patent was filed in 1984: a polystyrene foam was produced in an autoclave using nitrogen as the blowing agent, and after saturation of the sample, it was immersed in a stirred glycerine hot bath and then submerged in cold water; argon and carbon dioxide were also tested [119].…”