Laser Transmission Welding of Semicrystalline Thermoplastics - Part II: Analysis of Mechanical Performance of Welded Nylon

Abstract

Selecting thermoplastics for a wide industrial application (automotive, appliances, lawn and garden, power tools, etc.) strongly depends on the plastic material composition, part design, processing (molding and welding) conditions. The structure of used thermoplastics, mechanical properties and composition (reinforcements, fillers, additives, pigments, etc.) may have the greater influence and need to be characterized for optimum material selection for the laser transmission welding (LTW) application. To provide a guide to nylon based thermoplastics selection for LTW applications we have evaluated the influence of specific material composition factors and properties, such as fiber-glass, mineral filler, impact modifier content, and color/pigment version on the Near InfraRed (NIR) transmission characteristics, including the laser wavelength (1.06 mm). The results of an optical characterization of nylon 6 based thermoplastics are discussed in the Part I of this report to ANTEC’ 2000 (Kagan, V. A., Bray, R. B. and Kuhn, W. P., ‘‘Laser Transmission Welding of Semi-Crystalline Thermoplastics - Part I: The Magical Solution, Proceedings of the SPE 58th Annual Technical Conference and Exhibits (ANTEC’2000)). The mechanical performance (tensile strength at room temperature conditions) of nylon welded joints was evaluated in terms of the influence of transmission laser welding technology parameters (laser power, welding speed, laser beam spot sizes, clamp pressure, etc.) and thermoplastic composition (reinforcements, fillers, additives, pigments, etc.). Technical results of this comprehensive evaluation (optical properties of nylon 6 based plastics and mechanical performance of welded joints) will assist plastic parts designers and technologists in selecting nylon based thermoplastics and developing new products using LTW technology. The purpose of Part II of this report is to increase understanding within the plastics engineering community regarding the usefulness and possible applicability of LTW technology for nylon made components.