Microscopic and mechanical properties of semi-crystalline and amorphous polymeric parts produced by laser cutting

Microscopic and mechanical properties of polymeric parts are effective factors on their durability. Laser cutting is one of the most common methods for production of 2D polymeric parts. Experimental study of the mentioned properties of semi-crystalline and amorphous polymeric parts after laser cutting is conducted in this research. Low density polyethylene (LDPE) and polystyrene (PS) are considered as semi-crystalline and amorphous polymers, respectively. Laser power and cutting velocity were selected as input parameters of cutting process. According to microscopic observations, the microcracks, re-solidified spots of molten material, and sink marks just appear in heat affected zone (HAZ) on amorphous polymer. Results also showed that the HAZ width and surface roughness values are smaller for semi-crystalline polymer. For both polymers, decreasing of power and increasing of cutting velocity reduce the HAZ and surface roughness. In the case of mechanical properties, tensile strength of semi-crystalline and amorphous polymers reduces after laser cutting. Results of experiments revealed that the extension of HAZ and deterioration of surface finish decrease tensile strength of parts. Therefore, lower power and higher cutting velocity condition is preferable for reaching the better mechanical properties. Furthermore, two separate mathematical models for each polymer are presented for prediction of tensile strength after laser cutting process. (C) 2016 Wiley Periodicals, Inc.