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Title

The influence of the type of polypropylene and the length of the flow path on the structure and properties of injection molded parts with the weld lines.

Authors

Bociąga, Elżbieta; Kaptacz, Sławomir; Duda, Piotr; Rudawska, Anna

Abstract

Weld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. In the weld line area, the V‐shaped notch is formed and its shape and size depend on injection molding conditions and properties of processed polymer. Addition of the foaming agent to the polymer can be one of the way to improve conditions of melt streams welding due to the higher velocity of the colliding streams of unfilled polypropylene (PP) and PP filled with talc. The examinations of mechanical properties showed, however, lower tensile strength of porous parts compared to solid ones, but in the microscopic observation and measurements of the geometric structure of moldings, in the weld lines area, better surface conditions were achieved for samples made of the foamed polypropylene. The size of V‐notch, determined by the total height of the raw profile Pt, depends also on the length of polymer flow path from the gate to the weld line area. The values of Pt parameter increase with the length of the flow path, but this increase is smaller for foamed polypropylene. POLYM. ENG. SCI., 59:1710–1718 2019. © 2019 Society of Plastics Engineers

Subjects

SOCIETY of Plastics Engineers (Organization); WELDED joints; POLYPROPYLENE fibers; PLASTICS engineering; INJECTION molding of plastics; INJECTION molding; POLYPROPYLENE; SURFACE active agents; TENSILE strength

Publication

Polymer Engineering & Science, 2019, Vol 59, Issue 8, p1710

ISSN

0032-3888

Publication type

Academic Journal

DOI

10.1002/pen.25170

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