A design tool for core‐back timing in foam injection molding. Issue 45 (23rd September 2022)

• Record Type: Journal Article
• Authors: Taki, Kentaro; Menale, Marco; Pisante, Giovanni; Di Maio, Ernesto
• Is Part Of: Journal of applied polymer science. Volume 139:Issue 45(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-23
• Subjects: diffusion -- foams -- molding -- nucleation; Polymers -- Periodicals; Polymerization -- Periodicals; 668.9
• DOI: 10.1002/app.53121
• Languages: English
• ISSNs: 0021-8995

Abstract

Abstract: A visual observation experiment mimicking the pressure history in foam injection molding was utilized to infer the bubbles formation in core‐back operations. The different stages of bubble nucleation, dissolution, and re‐nucleation, corresponding to injection, packing, and core‐back opening, respectively, were studied. A reduction of the number density of re‐nucleated bubbles with respect to first nucleation was observed. In order to understand this observation, the evolution of the blowing agent concentration around the dissolved bubbles was analyzed. A characteristic time was introduced, required to achieve blowing agent uniformity or, equivalently, required to cancel the mass transport‐mediated memory of the system. A numerical model, assuming Fickian behavior, was derived and validated with the experimental results. The study allowed for the development of a predictive tool to design core‐back operations in foam injection molding. Abstract : In foam injection molding, complete memory loss of premature bubble formation is attained after a characteristic diffusion time dependent on diffusivity and premature foam morphology.