Study and application of pressure⁃volume behaviors of entrained gas materials in foam injection molding

doi:10.19491/j.issn.1001-9278.2024.08.011

Abstract

Abstract:

In this study， in⁃line measurement of pressure⁃volume⁃temperature in injection molding was achieved by using a modified conventional microcellular injection molding machine that generates high pressure on the recovered entrained gas polymer melt. The studies on the pressure⁃volume behavior of entrained gas melts of polystyrene and polypropylene at a certain temperature indicated that the compressibility of entrained gas polymer melts was much greater than that of gas free polymer melts at specific temperature. In practical applications， the larger compressibility of entrained gas polymer melts can be used to assist in injection and speed up the gas integration process into the melt， thereby improving foaming quality. On the other hand， the pressure release test based on the potential safety hazards of entrained gas polymer melt due to its large compressibility of the melt has put forward a new safety operation guide for injection molding of entrained gas materials for the first time in China.

Key words: microcellular foam injection molding, polystyrene, polypropene, entrained gas melt, compressibility, safety, pressure?volume

CLC Number:

TQ320.6

XU Jingyi, LUO Baoshu, WANG Shengwang, CHEN Jianbo, GE Fujiong, YANG Yafeng, HE Yadong. Study and application of pressure⁃volume behaviors of entrained gas materials in foam injection molding[J]. China Plastics, 2024, 38(8): 69-75.

Figures/Tables 9

Fig.1. Modified self⁃close non⁃return valve

Fig.2. Heavy load shut⁃off nozzle （Herzog）

Fig.3. Hydraulic system of the modified microcellular injection molding machine for PV test

Fig.4. PV data of the GPPS⁃N2 mixed melt at 223 ℃

Fig.5. PV data of the GPPS⁃CO2 mixed melt at 223 ℃

Fig.6. PV data of the GPPS （223 ℃） and PP （211 ℃） melt

Fig.7. Compressibility of the GPPS⁃N2 mixed melt at 223 ℃

Fig.8. Cell structures of the samples

螺杆头前熔体压力	释压时间/min
螺杆头前熔体压力	0	1	2
100 %预塑体积	21	13	10
40 %预塑体积	16	6	4

Tab.1. Relationship between pressure release of the gas⁃bearing melt and time

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