Manufacturing marks on polymer films

Abstract

Polymer film fabrication is the first step in the plastic bag manufacturing process. This is the step that leaves most of the marks on the finished product, and these marks are exploited as unique identifiers in forensic engineer and traceability. It was expected that specially the percent of recycled plastic, the die and the rollers would contribute most of the marks. For this thesis five different plastic products whose manufacturing process starts with polymer film fabrication, were chosen to be tested: clingfilm, a recycled plastic bag, self-adhesive tape, a self-seal bag, and a transparent plastic bag. FTIR (Fourier- transform infrared spectroscopy) was used to determine the material composition of the test materials. Four samples were taken from one batch and one sample from a different batch, total five samples. The aim of the study was to identify the different sample. Area of analysing was optical marks in the visible light region. The methods used to identify the different sample, were visual observation, paint, and manufacturing mark analysing using an optical microscope and surface roughness and waviness testing using the Surftest testing machine. The results from the tests gave four of five products the correct answer. The transparent plastic bag result was incorrect. Based on the findings the best tests to identity a sample from a different batch, is by analysing its paint- and manufacturing marks under an optical microscope.