Foam Injection Molding of Polypropylene/Zinc Oxide Nanocomposite with Chemical Foaming Agent: Mechanical Properties and Morphology

The MuCell process is a special injection molding process which utilizes supercritical gas (nitrogen) to create integral foam sandwiches. The advantages are lower weight, higher specific properties and shorter cycle times. In this study, a series of glass fiber-reinforced polyphenylene sulfide foam blanks are manufactured using the MuCell injection molding process. The different variations of the process (low-pressure also known as structural foam injection molding) and high-pressure foam injection molding (also known as “core back expansion,” “breathing mold,” “precision opening,” decompression molding) are used. The sandwich structure and mechanical properties (tensile strength, bending strength, and impact behavior) of the microcellular and glass fiber-reinforced polyphenylene sulfide foams are systematically investigated and compared to compact material. The results showed that the injection parameters (injection speed, foaming mechanism) played an important role in the relative density of microcellular polyphenylene sulfide foams and the mechanical properties. It could be shown that the specific tensile strength decreased while increasing the degree of foaming which can be explained by the increased number of cells and the resulting cell size. This leads to stress peaks which lower the mechanical properties. The Charpy impact strength shows a significant dependence on the fiber orientation. The specific bending modulus of the high-pressure foaming process, however, surpasses the values of the other two processes showing the potential of this manufacturing variation especially with regard to bending loads. Furthermore, a high dependence of the mechanical properties on the fiber orientation of the tested specimens can be found.

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Effect of Blowing Agent and Polyethylene Glycol on Cellular Structure and Mechanical Properties of Chloroprene Rubber

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.217-219.517 ◽

2012 ◽

Vol 217-219 ◽

pp. 517-521 ◽

Cited By ~ 2

Author(s):

Hong Ling Yi ◽

Ting Wei ◽

Lin Heng ◽

Bai Cun Zheng

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Zinc Oxide ◽

Polyethylene Glycol ◽

Cellular Structure ◽

Foaming Agent ◽

Blowing Agent ◽

Swell Ratio ◽

Closed Cell ◽

Chloroprene Rubber

In this paper the closed-cell sponge of chloroprene rubber(CR) were produced by foaming agent Azodicarbonamide (AC) and Oxybis (benzene sulfonyl) hydrazide (OBSH). The blend blowing agent AC/OBSH was more effective than the pure AC as it could produce chloroprene foam with greater cell porosity, more uniform and better cell distributions. The CR foam prepared with AC/OBSH had better tensile strength and tear strength than pure AC, but higher Shore C hardness. The Polyethyene glycol (PEG) modified Zinc Oxide (ZnO) could accelerate curing and foam process simultaneously. Increase the content of PEG, CR foam has bigger swell ratio, smaller cell size, and better softness.

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Effect of processing condition on properties of polylactic acid parts obtained by foam injection molding

Journal of Cellular Plastics ◽

10.1177/0021955x16670589 ◽

2016 ◽

Vol 53 (5) ◽

pp. 491-502 ◽

Cited By ~ 5

Author(s):

Valentina Volpe ◽

Roberto Pantani

Keyword(s):

Mechanical Properties ◽

Injection Molding ◽

Polylactic Acid ◽

Flow Rate ◽

Flexural Modulus ◽

Processing Condition ◽

Blowing Agent ◽

Injection Flow Rate ◽

Injection Flow ◽

Foam Injection Molding

Foam injection molding is a processing technology particularly interesting for biodegradable polymers, which present a very narrow processing window, with the suitable processing temperatures close to the degradation conditions. The addition of a physical blowing agent, besides decreasing the final part weight, reduces both the viscosity and the glass transition temperature of the polymer melt, allowing the processability of these materials at lower temperatures. In this work, structural foams of polylactic acid with nitrogen as physical blowing agent were obtained by foam injection molding. In particular, the effects of back pressure, namely the pressure imposed inside of the cylinder when the screw is returning back to prepare a new amount of material to be injected, and of the injection flow rate on foaming and mechanical properties of the molded parts was assessed. It was found that the samples molded adopting a higher injection flow rate are shorter than those injected at lower flow rate, and this result was ascribed to the large compressibility of the injected shot. As far as the mechanical properties of the foamed parts, it was found that the modulus decreases with decreasing density. However, the density reduction is not the only significant parameter, but also the morphology of the foams should be taken into account in order to justify the differences between tensile and flexural modulus.

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Effects of Nano-CaCO3 Content on the Crystallization, Mechanical Properties, and Cell Structure of PP Nanocomposites in Microcellular Injection Molding

Polymers ◽

10.3390/polym10101160 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1160 ◽

Cited By ~ 11

Author(s):

Huajie Mao ◽

Bo He ◽

Wei Guo ◽

Lin Hua ◽

Qing Yang

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Injection Molding ◽

Cell Structure ◽

Nucleating Agent ◽

Foaming Agent ◽

Caco3 Content ◽

Microcellular Injection Molding ◽

Vertical Sections

Using supercritical nitrogen as the physical foaming agent, microcellular polypropylene (PP) nanocomposites were prepared in microcellular injection molding. The main purpose of this work is to study effects of content of nano-CaCO3 on the crystallization, mechanical properties, and cell structure of PP nanocomposites in microcellular injection molding. The results show that adding nano-CaCO3 to PP could improve its mechanical properties and cell structure. The thermal stability and crystallinity enhances with increase of nano-CaCO3. As a bubble nucleating agent, adding nano-CaCO3 to PP improves the cell structure in both the parallel sections and vertical sections. The mechanical properties increase first and then decrease with increase of nano-CaCO3. The mechanical properties are affected by the cell structure, as well. The mechanical properties and cell structure are optimum when the content of nano-CaCO3 is 6 wt %.

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

Journal of Cellular Plastics ◽

10.1177/0021955x11408769 ◽

2011 ◽

Vol 47 (6) ◽

pp. 519-534 ◽

Cited By ~ 31

Author(s):

Marieluise Stumpf ◽

Andreas Spörrer ◽

Hans-Werner Schmidt ◽

Volker Altstädt

Keyword(s):

Mechanical Properties ◽

Injection Molding ◽

Control Cell ◽

Large Cell ◽

Processing Parameters ◽

Expansion Ratio ◽

Foam Formation ◽

Nucleating Agents ◽

Foam Morphology ◽

Foam Injection Molding

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.

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