The Effect of Processing Parameters and Calcium-stearate on the Ejection Process of Injection Molded Poly(Lactic Acid) Products

IF 1.3 Q3 ENGINEERING, MECHANICAL

PERIODICA POLYTECHNICA-MECHANICAL ENGINEERING Pub Date : 2021-10-25 DOI:10.3311/ppme.18246

T. Tábi, K. Pölöskei

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引用次数: 4

Abstract

We investigated the ejection/demolding of continuous production of injection molded Poly(Lactic Acid) tensile testing specimens and analyzed the effect of 1 wt% Calcium-Stearate additive as demolding agent (sliding or mold release agent) on this process. We demonstrated that the Poly(Lactic Acid) specimens could get stuck in the mold or even break during demolding during continuous injection molding in a certain type of mold, which has a low draft angle and varying cavity width along the flow path. The standard dumbbell-shaped tensile testing specimen is produced in such a mold. Demolding was rated with the use of a high-speed camera into three categories (problem-free demolding / stuck, but demolded undamaged product / stuck and damaged product). Moreover, the ejector force required to push the product out of the cavity was monitored over 30 continuous injection molding cycles. We also investigated the effect of processing parameters, such as injection rate (screw speed), holding pressure, holding time, mold temperature, melt temperature, backpressure, screw rotational speed, and pre-process drying (drying or not drying the pellets before injection molding). We managed to avoid product breakage during demolding with the proper settings of certain process parameters and the use of Calcium-Stearate, an effective demolding agent. This ensured problem-free demolding and thus continuous injection molding.

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工艺参数及硬脂酸钙对聚乳酸注塑成型产品挤出过程的影响

我们研究了连续生产注塑成型聚乳酸拉伸试样的脱模，并分析了1wt %硬脂酸钙添加剂作为脱模剂(滑动或脱模剂)对这一过程的影响。在某型低抽模角、沿流道型腔宽度变化的连续注射成型过程中，聚乳酸样品在脱模过程中会卡模甚至断裂。标准的哑铃形拉伸试样就是在这种模具中生产的。使用高速摄像机将脱模分为三类(无问题脱模/卡住，但脱模后未损坏产品/卡住并损坏产品)。此外，在30多个连续的注射成型周期中，监测了将产品推出型腔所需的喷射力。我们还研究了工艺参数的影响，如注射速度(螺杆速度)、保持压力、保持时间、模具温度、熔体温度、背压、螺杆转速和预处理干燥(在注射成型前干燥或不干燥)。通过适当设置某些工艺参数和使用硬脂酸钙(一种有效的脱模剂)，我们成功地避免了脱模过程中产品的破损。这确保了无问题脱模，从而连续注射成型。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

PERIODICA POLYTECHNICA-MECHANICAL ENGINEERING ENGINEERING, MECHANICAL-

CiteScore

2.80

自引率

7.70%

发文量

审稿时长

20 weeks

期刊介绍： Periodica Polytechnica is a publisher of the Budapest University of Technology and Economics. It publishes seven international journals (Architecture, Chemical Engineering, Civil Engineering, Electrical Engineering, Mechanical Engineering, Social and Management Sciences, Transportation Engineering). The journals have free electronic versions.