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Detecting latent "tiger stripes" on injection moulded trim lists
2003 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

“Tiger stripes" is a surface defect that can appear on injection moulded products. It is generally referred to as dull and rough bands on a normally smooth and shiny plastic surface. “Tiger stripes” has been observed with a broad range of polymers and its appearance mainly depends on material and tool parameters together with process conditions. Today latent “tiger stripes” appears on exterior car details such as trim lists and bumper covers. Latent "tiger stripes" is a problematic surface defect that deteriorates the aesthetic impression of several car models. The aim of this work is to try to provoke and make latent “tiger stripes” appear at the laboratory and eventually find a method for detecting latent “tiger stripes”. A series of tests were performed on a rear trim list and a front trim list where the appearance of latent "tiger stripes" is being observed on the field. The material is a PP/ EPDM elastomer blend. Different equipment for accelerating ageing tests were used. In addition to the ageing factors provided by the equipment, an artificial dirt was applied to the majority of the samples during tests. It was found that the combination heat and artificial dirt makes latent "tiger stripes" appear at the laboratory. The best result was obtained with heat ageing at 90°C combinated with artificial dirt that was removed and applied again once a week. A sharp pattern was obtained on the rear trim list after two weeks and on the front trim list after three weeks. The results from this work can be used to develop a test method for detecting latent "tiger stripes" on exterior car details. A pattern that appears after several months on the field can by heat ageing combinated with artificial dirt be detected after a minimum of two weeks at the laboratory.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Injection moulding, surface defect, flow marks, trim list
Keyword [sv]
URN: urn:nbn:se:ltu:diva-57837ISRN: LTU-EX--03/267--SELocal ID: e74e9768-2a79-4611-b934-68c45061f592OAI: diva2:1031225
Subject / course
Student thesis, at least 30 credits
Educational program
Materials Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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