Structure and mechanical properties of polystyrene foams made through microcellular injection molding via control mechanisms of gas counter pressure and mold temperature

Chen, Shia‐Chung; Liao, Won-Hsion; Chien, Rean‐Der

doi:10.1016/j.icheatmasstransfer.2012.06.015

Cited by 42 publications

(28 citation statements)

References 13 publications

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“…Although the electrical conductivity of the overall part decreased slightly when the GCP was applied, the results obtained in this investigation show the potential application of GCP technology combined with mold temperature control in conventional injection molding to manufacture products with enhanced electrical conductivity. As in our previous study [19], because GCP was able to increase the fiber orientation in the through-plane direction at the core region and mold temperature control can decrease the skin layer thickness, TPEC increased.…”

Section: Resultssupporting

confidence: 72%

“…Gas counter pressure (GCP) [17][18][19] processing is a technology dating from the 1970s, usually applied to improve the surface quality of foam injection molded parts. In normal injection molding, as the plastic melt enters a mold, it displaces the air within the cavity and the air is vented to the atmosphere via specially designed vents specific to the type of plastic being molded.…”

Section: Introductionmentioning

confidence: 99%

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Effect of gas counter pressure on the carbon fiber orientation and the associated electrical conductivities in injection molded polymer composites

Chen¹,

Chien

Lin³

et al. 2014

Journal of Polymer Engineering

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Polymers filled with conducting fibers to provide electrical conductivity performance have received great attention due to the requirements of many engineering applications. In the present article, injection molding of acrylonitrile butadiene styrene (ABS)/carbon-fiber composites using applied gas counter pressure (GCP) was conducted and the overall fiber orientation and associated through-plane electrical conductivity (TPEC) of each layer (core, shear and skin layers) and various locations (far gate, center and near gate) were characterized. Results show that GCP had significant effects on the fiber orientation and skin layer thickness, resulting in decreases in the fiber orientation level (FOL) value in all locations and TPEC increases with increasing GCP in the core region of the molded composites (improvement of 62% when 100 bar GCP was applied). However, the effect of increased skin layer thickness in reducing TPEC was stronger than the effect of decreased FOL in raising TPEC when GCP was applied. This resulted in the overall TPEC falling slightly with increasing GCP. The results also show that the electrical conductivity followed the sequence of far gate > center > near gate and the FOL followed the order of core layer < shear layer < skin layer. The results obtained in this investigation reveal the potential application of GCP technology associated with mold temperature control in injection molding to manufacture products with enhanced electrical conductivity in the future.

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Section: Resultssupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Effect of gas counter pressure on the carbon fiber orientation and the associated electrical conductivities in injection molded polymer composites

Chen¹,

Chien

Lin³

et al. 2014

Journal of Polymer Engineering

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“…Therefore, the main difference between the nucleation mechanism in low-pressure and high-pressure FIM schemes was the source of the pressure drop, which induced bubble nucleation. In order to increase the surface quality and structural homogeneity of FIM parts, the FIM process was performed using GCP [12,13]. In this method, the mold cavity was charged with GCP, higher than the solubility pressure of the dissolved BA, prior to the filling step.…”

Section: Resultsmentioning

confidence: 99%

“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Shaayegan¹,

Mark²,

Tabatabaei³

et al. 2016

Express Polym. Lett.

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Abstract. The complex mechanisms of bubble nucleation and dynamics in foam injection molding have not been uncovered despite many previous efforts due to the non-steady stop-and-flow nature of injection molding and the non-uniform temperature and pressure distributions in the mold. To this end, a new visualization mold was designed and manufactured for the direct observation of bubble nucleation and growth/collapse in foam injection molding. A reflective prism was incorporated into the stationary part of the injection mold with which the nucleation and growth behaviors of bubbles were successfully observed. The mechanisms of bubble nucleation in low-and high-pressure foam injection molding, with and without the application of gas-counter pressure, was investigated. We identified how the inherently non-uniform cell structure is developed in low-pressure foam injection molding with gate-nucleated bubbles, and when and how cell nucleation occurs in high-pressure foam injection molding with a more uniform pressure drop.

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“…Chen et al showed that the application of larger and longer GCP resulted in a thicker skin layer and in smaller cells in the core region of the PS sample foams. They also found that using GCP improved the sample's tensile strength …”

Section: Introductionmentioning

confidence: 95%

Identification of cell‐nucleation mechanism in foam injection molding with gas‐counter pressure via mold visualization

et al. 2016

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The mechanisms of cell nucleation and growth are investigated in foam injection molding (FIM) using gas-counter pressure (GCP). An in-situ mold visualization technique is employed. The application of GCP suppresses cell nucleation, and prevents the blowing agent from escaping during mold-filling. The inherent structural heterogeneity in the regular FIM can be improved because of the uniform cavity pressure when employing GCP. The cavity pressure profiles show much faster pressure-drop rates using GCP, because the single-phase polymer/gas mixture has a lower compressibility than the two-phase polymer/bubble mixture. Therefore, both the cell nucleation and growth rates are significantly increased through a higher pressure-drop rate on the removal of the GCP. The effect of GCP magnitude on the cell morphology is explored. When the GCP is lower than the solubility pressure, bimodal foaming occurs. As the GCP increases above the solubility pressure, the cell density increases because of the higher pressure-drop rate. Figure 14. Formation of a bimodal structure as a result of an insufficient GCP of 2.30 MPa (injection speed: 35 cm 3 s 21 ; CO 2 : 1%; T melt 5 230 C).

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Structure and mechanical properties of polystyrene foams made through microcellular injection molding via control mechanisms of gas counter pressure and mold temperature

Cited by 42 publications

References 13 publications

Effect of gas counter pressure on the carbon fiber orientation and the associated electrical conductivities in injection molded polymer composites

Effect of gas counter pressure on the carbon fiber orientation and the associated electrical conductivities in injection molded polymer composites

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

Identification of cell‐nucleation mechanism in foam injection molding with gas‐counter pressure via mold visualization

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