Influence of supramolecular additives on foam morphology of injection-molded i-PP

Abstract

Foaming isotactic polypropylene (i-PP) by foam injection molding usually results in inhomogeneous, large cell structures. Possibilities to realize more homogeneous and finer foam morphologies are adjusting processing parameters or adding nucleating agents. Often, inorganic nucleating agents such as talc in concentrations of about 2 wt% are used to influence the foam morphology. This article discusses the use of two benzene trisamide-based nucleating agents to control cell nucleation during foaming of i-PP. These additives form supramolecular nanostructures in the polymer melt acting first as nucleating sites for foam formation and second as nuclei for the polymer crystallization. Foaming was performed by foam injection molding with nitrogen as physical blowing agent. A specially designed variotherm mold technology was utilized to exactly control the foaming temperature, foaming pressure, and expansion ratio. Foamed i-PP samples were prepared with a density reduction of 50% and analyzed with respect to foam structure and mechanical properties. We demonstrate that the benzene trisamide additives have a strong influence on the foam morphology at very low additive concentrations. Only 0.02 wt% of an additive is sufficient to obtain a remarkable reduction of the cell sizes. It appears that the cell struts, those dimensions can be influenced by the additives as well, leads to a significant improvement of the mechanical properties.

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

“…15 and 16, when the dwelling time was set to 5.5 s, the polymer temperature was about 111 C. Figure 17 shows the nonisothermal crystallization behaviors of both neat i-PP and i-PP with Gel-all MD. The measurement was conducted by the Flash DSC at the high cooling rate, 19 C s…”

Influence of rheology and morphology on foaming of PS-b-PMMA diblock copolymers and their composites with modified silica nanoparticles

“…By controlling the degree of polymerization and the volume fraction of the blocks, one can fine-tune the microstructure of block copolymers for applications in a variety of industrial fields: toughness modifiers, membranes, surface modifiers, compatibilizers, biocompatible materials, electric and optical applications [4][5][6]. On the other hand, thermoplastic polymer foams have been widely used in a variety of applications, e.g., membranes, insulation, absorbents, cushion and weight-bearing structures [7][8][9][10][11]. Environmentally benign, non-flammable and inexpensive gas like carbon dioxide (CO2) has been widely used in polymer processing and hence as a porogenic agent [12][13][14].…”

A new insight into foaming mechanisms in injection molding via a novel visualization mold

“…The location of the viewing windows in the fixed plate, on the opposite side of the mold cavity, makes it possible to perform various experiments by simply changing the mold insert, some of which includes, but is not limited to, gasassisted FIM studies, shear/extension induced FIM, and the study of flow in various channels. Also, the mold can be utilized to investigate other FIM technologies such as gas-counter pressure (GCP) [12,13] and mold opening (core back) [9,10,14,15]. The designed mold can be utilized to further investigate the mechanisms of bubble nucleation/growth, interaction between bubbles and fillers [16,17], the effect of formed crystals on foaming [18], weld-line studies [19], defects [20], and model verifications [21].…”