Sandra Matos is a Ph.D student at Department of Polymer Engineering in University of Minho. She studied Chemistry Engineering at Lisbon Superior Institute of Engineering and had an M.Sc in Polymer Processing and Technology at University of Minho, she is been studying the behavior and the processing effects of materials used on coating of wires for Automotive Industry. She is mainly doing researches on chemical effect of materials used on coating of electrical automotive wires and its impact in processes used at that industry. She is also serving as a reviewer of several reputed journals.
The ultrasonic metal welding process allows the joining of metals by the application of high frequency vibrations, under moderate pressure, in which the vibrations are applied parallel to the interface between the parts. The frequency between the parts, forms a solid-state weld through progressive shearing and plastic deformation over the surface asperities that disperses oxides and contaminants and brings an increasing area of pure metal contact between adjacent surfaces . The problems of metal oxides, high thermal conductivity, high electrical conductivity, intermetallic and brittle alloys are not significant in the ultrasonic welding since the ultrasonic equipment may be capable of monitoring energy and control the critical welding variables. However, on automotive industry, for applications that involve the ultrasonic welding of wires it has been seen that depending on the coating material of wires the metal bonding is not always stronger as it should be. Several studies were been done using different types of materials as insulators and as a results it was seen that PVC coated wires have worst results and even those are varying depending on the PVC formulation used. PVC is considered one of the most versatile polymers due to their ability to react with various additives before being processed into final products. By the choice within a wide range of chemicals, it is possible to obtain PVC compounds with the necessary features for each application but there are a large number of variables that affect the properties of PVC such as the degree of crystallinity, the glass transition temperature, molecular weight or morphology . The mechanical, thermal or chemical properties of the manufactured product may have specific characteristics, mainly due to two important factors: inclusion of appropriate additives in PVC formulations (plasticizers, pigments, lubricants, colorants, flame retardants, etc.) and a variety of manufacturing processes such as extrusion, injection, etc . As coating of wires, PVC is used in the flexible form, but due to PVC thermal instability, processing it is virtually impossible without the addition of additives. The additives are generally high molecular weight thermoplastic and are added in small quantities with three main functions, accelerate the fusion process, improve the rheological and mechanical properties. The biggest disadvantage of PVC is the easiness to degrade by the action of temperature or ultraviolet radiation. In order to identify the cause of negative effect on ultrasonic metal welding process of wires, a study was conducted using electrical wires coated with PVC with different formulations.