Tiger-Striped Flow Mark of Polypropylene Alloys

Maeda, Shuichi

doi:10.1678/rheology.49.215

Cited by 5 publications

(1 citation statement)

References 10 publications

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“…The flow marks have some common features. They all consist of visually glossy and cloudy regions that alternate on the surface of the injection molded products and usually appear downstream of the flow, which is almost perpendicular to the flow direction of the melt. – In many cases, the period of the flow marks is reversed on the opposite side. – That is, the cloudy and glossy regions on one side correspond to the glossy and cloudy regions on the opposite side. It is worth noting that the flow marks adversely affect not only the desired appearance of the injection molded products but also their required long-life mechanical properties. – Therefore, it is important and necessary to clarify the generation mechanism of the flow marks and reduce or eliminate them.…”

Section: Introductionmentioning

confidence: 99%

Development of Unstable Flow and Morphological Analysis of Flow Marks in Injection Molding of Polypropylene and Polyolefin Elastomer Blend

Hu,

Zhang,

Song

et al. 2023

Ind. Eng. Chem. Res.

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The unstable flow phenomenon in injection molding and the resulting flow marks adversely affect the application of polymer products. Therefore, it is important and necessary to study the unstable flow to clarify the generation mechanism of the flow marks. In this work, the development of unstable flow in injection molding of the polypropylene/polyolefin elastomer (PP/POE) blend was investigated through short shot injection molding experiments. The results show that the melt flows stably at the early stage, and then, the flow front of the melt begins to fluctuate along the thickness direction, resulting in the formation of an unstable flow of the melt and periodic concave and convex regions on the surface of short shot samples. The relationship between the generation of flow marks and the development of unstable flow was also clarified, that is, the convex and concave regions formed during the filling process evolve into the cloudy and glossy regions of the flow marks, respectively. Since the melts in different regions experience different shear and thermal histories, the orientation degree of the dispersed phase and the crystal in the cloudy region is higher than that in the glossy region, while the glossy region has a higher crystallinity and lamellar thickness. Ultimately, a more refined unstable flow model for the generation mechanism of flow marks was proposed..

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