Rheological characterization of polystyrene melts dissolved with supercritical nitrogen fluid during microcellular injection moulding

Chen, Shia‐Chung; Chung, Ming-Hsiu; Lin, Yu-Wan; Hsu, Ping-Shun; Hwang, Shyh Shin; Hsu, Peming P.

doi:10.1515/epoly.2010.10.1.1446

Cited by 7 publications

(10 citation statements)

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“…Polymers and Fillers Molded Part Thickness, mm [4,7,8,11,13,16,22,23] PP GF20; PP/LDPE blends; PP + GF + Talc; PP-TPU; PP CF20; PP CF30; PP + EPDM + TALC 2.4-4.0 [6,9,15,17] PA66 GF 30 1.5-4.0 [7,24] PLA/PHBV; PLA/PTFE (fibril) 3.3-4.0 [10,12] PC; PC/ABS 1.7-4.0 [14,25] PS 3.0…”

Section: Entry In the Literature Listmentioning

confidence: 99%

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring

2020

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The aim of the study was to detect the influence of nitrogen pressure on the rheological properties and structure of PA66 GF30 thick-walled parts, produced by means of microcellular injection molding (MIM), using the MuCell® technology. The process was monitored in-line with pressure and temperature sensors assembled in the original injection mold. The measured data was subsequently used to evaluate rheological properties inside an 8.4 mm depth mold cavity. The analysis of the microcellular structure was related to the monitored in-line pressure and temperature changes during the injection process cycle. A four-times reduction of the maximum filling pressure in the mold cavity for MIM was found. At the same time, the holding pressure was taken over by expanding cells. The gradient effect of the cells distribution and the fiber arrangement in the flow direction were observed. A slight influence of nitrogen pressure on the cells size was found. Cells with a diameter lower than 20 µm dominate in the analyzed cases. An effect of reduction of the average cells size in the function of distance to the gate was observed. The creation of structure gradient and changes of cells dimensions were evaluated by SEM images and confirmed with the micro CT analysis.

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Section: Entry In the Literature Listmentioning

confidence: 99%

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring

2020

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“…Foaming after melting filling plays a significant role in packing function leading to shrinkage reduction, warpage minimization, and elimination of sink marks, etc. The process characteristics and molded part properties have been studied earlier [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Despite its advantage, MuCell also faces technology challenges that hinder its wide application.…”

Section: Introductionmentioning

confidence: 99%

“…Dynamic mold temperature control [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ] uses cavity surface coating or film-insert mold surface to delay the heat transfer on the cavity surface leading to an elevated mold temperature during the melt-filling stage. An alternate and effective way of solving the surface quality issue is the use of counter-pressure techniques, particularly the gas counter-pressure (GCP) technology [ 20 , 21 , 22 , 23 , 24 ], that have been reported to effectively improve the part surface roughness. Bledzki et al [ 21 ] first reported a reduction in the part surface roughness (Rz) from 23 lm to 0.85 lm.…”

Section: Introductionmentioning

confidence: 99%

Using P(Pressure)-T(Temperature) Path to Control the Foaming Cell Sizes in Microcellular Injection Molding Process

et al. 2021

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Microcellular injection molding technology (MuCell) using supercritical fluid (SCF) as a foaming agent is one of the important green molding solutions for reducing the part weight, saving cycle time, and molding energy, and improving dimensional stability. In view of the environmental issues, the successful application of MuCell is becoming increasingly important. However, the molding process encounters difficulties including the sliver flow marks on the surface and unstable mechanical properties that are caused by the uneven foaming cell sizes within the part. In our previous studies, gas counter-pressure combined with dynamic molding temperature control was observed to be an effective and promising way of improving product quality. In this study, we extend this concept by incorporating additional parameters, such as gas pressure holding time and release time, and taking the mold cooling speed into account to form a P(pressure)-T(temperature) path in the SCF PT diagram. This study demonstrates the successful control of foaming cell size and uniformity in size distribution in microcellular injection molding of polystyrene (PS). A preliminary study in the molding of elastomer thermoplastic polyurethanes (TPU) using the P-T path also shows promising results.

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“…To produce foam cores by injection moulding, blowing agents are used, which are typically divided into physical blowing agents (PBAs) and chemical blowing agents (CBAs) [24–26]. PBAs such as CO 2 [27] or N 2 [28] are usually used in microcellular injection moulding technologies such as MuCell ® . PBAs are introduced into the plasticizing unit of the injection moulding machine in a supercritical state.…”

Section: Introductionmentioning

confidence: 99%

Thermoplastic foam injection moulding of sandwich structures with short fibre-reinforced skin layers

Loypetch

Tröltzsch

Nestler

et al. 2019

Jnl of Sandwich Structures & Materials

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Sandwich structures, consisting of a short glass fibre–reinforced polypropylene film as skin layer and chemically blown polypropylene as the core material, were produced via injection moulding. The skin layers of the sandwich structures, which contain polypropylene as well as 30 wt% and 50 wt% of glass fibres namely polypropylene–glass fibres 30 and polypropylene–glass fibres 50 respectively, were produced by film extrusion using a coat hanger die. The properties of the films were investigated by dynamic mechanical analysis. Furthermore, the influence of different glass fibre contents in the skin layers and chemical blowing agent contents in the core material of sandwich structures was studied to compare them with the compact polypropylene and the polypropylene foams. The sandwich structures were characterized with regard to density, microstructure, weight reduction, surface roughness and bending properties. In general, distinctive reinforcement effect was achieved by use of the short glass fibre with the strong influence of processing direction of the film. For the sandwich structures, it was found that a good adhesion between the skin layers and the core material can be achieved during injection moulding. The microstructure and the bending properties of the sandwich structures depend on the glass fibre–reinforced film and the chemically blown core. It was found that the use of the skin layers led to lower cell intensity in the foam core. Nevertheless, a high modulus and strength to weight ratio could be accomplished by a high stiffness of the glass fibre–reinforced film and a low density of the chemically blown core. Additionally, it was found that the surface roughness of the films could be reduced due to processing in injection moulding.

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Rheological characterization of polystyrene melts dissolved with supercritical nitrogen fluid during microcellular injection moulding

Cited by 7 publications

References 0 publications

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring

Using P(Pressure)-T(Temperature) Path to Control the Foaming Cell Sizes in Microcellular Injection Molding Process

Thermoplastic foam injection moulding of sandwich structures with short fibre-reinforced skin layers

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