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

Abstract

A complete experimental analysis of the microcellular injection process using Chemical Blowing Agents (CBA) with Gas Counter Pressure (GCP) and core‐back expansion is presented. Three different types of polypropylene, neat and charged, were mixed with two different CBAs and injected into a plate mold with varying process parameters. First, an exhaustive cartographical mapping of the plate morphology is analyzed. In a second step, the relation between injection parameters and the resulting morphology is investigated. The results show that injection time affects the cellular structure. The formulation, especially the type of chemical foaming agent, controls the average bubble radius. Compared with classical injection process, the use of CBAs, combined to Gas Counter Pressure and core‐back process, allows obtaining parts with good surface aspect, more homogeneous cellular structures and smaller bubble radius. POLYM. ENG. SCI., 55:2465–2473, 2015. © 2015 Society of Plastics Engineers

Microcellular polymeric foams based on 1‐vinyl‐2‐pyrrolidone and butyl‐acrylate with tuned thermal conductivity

“…Cellular structural characterization was carried out throughout the determination of the average bubble radius and cell density, that were measured using the Image software from SEM images . For each sample, three different SEM micrographs were analyzed.…”

Polypropylene/Chemical Blowing Agent Foams: Effect of the Injection Speed and Core Back Distance on Microstructure and Mechanical Properties

“…It is possible to produce several parts in different wall thicknesses, densities and mechanical properties using the same polymer/chemical blowing agent mixture only by changing the process parameters and core back set up of the mold. The core back distance and injection speed have a huge influence on microstructure and mechanical properties of PP foams and very few studies can be found in the literature (Wu et al 2018, Reglero Ruiz et al 2016, Reglero Ruiz et al 2015, Wu et al 2019 The core-back system is actually an advanced technology allowing an increase of the weight reduction. In this technology, the core back represents an additional step during the injection molding process which provides a free volume for polymer foaming.…”

“…In this way, the manufacturing of foamed plastic parts becomes more achievable with an increased weight reduction. (Wu et al 2018, Reglero Ruiz et al 2016, Reglero Ruiz et al 2015, Wu et al 2019, Stumpf et al 2011, Zhao et al 2017, Miyamoto et al 2014, Sporrer and Altstadt 2007, Chu et al 2016, Ishikawa and Ohshima 2011, Ameli et al 2015, Shaayegan et al 2017, Ishikawa et al 2012) Wu et al (2018 examined the mechanical properties of polymeric foams composed of syndiotactic PP mixed with azodicarbonamide as chemical blowing agent and produced by injection molding and core back technologies. They showed that the core back technique decreases the defects present on the surface of specimens and improved the mechanical properties even at similar weight drop conditions.…”

Effect of Mold Opening Process on Microporous Structure and Properties of Microcellular Polylactide–Polylactide Nanocomposites

“…Valentina explored the filling and cooling stages by Moldflow simulations, and compared the morphological, rheological, and mechanical properties of two different PLA grades by foam injection molding with mold opening process [ 24 ]. Ruiz et al analyzed the morphology of microcellular injected polypropylene using chemical blowing agents and a combination of core-back and GCP processes [ 25 ]. With regard to the cell-nucleation mechanisms in high-pressure foam injection molding, Shaayegan et al studied the mechanism of controlled bubble nucleation in high pressure foam injection molding via in situ visualization using polystyrene and supercritical carbon dioxide system.…”