Infrared Welding of Thermoplastics. Colored Pigments and Carbon Black Levels on Transmission of Infrared Radiation

Abstract

This chapter discusses colored pigments and carbon black levels on transmission of infrared radiation. Infrared welding has been characterized as unpredictable because different polymers or formulations have been observed to heat at widely different rates under similar conditions. Polymers that have pigments with other colors of the spectrum and can scatter light might also be expected to show differences in absorption of infrared energy. This chapter aims to study the absorption characteristics of IR energy by different polymers, by variously colored ABS materials, and by polymers with different levels of carbon black. This information should provide practical guidelines and process understanding when infrared welding is being used. Infrared welding has the ability to penetrate polymers and heat them; it offers the potential for stronger joints because a deeper melt zone is created by absorption, at once, rather than by conduction through the polymer. Polymers of different colors can be expected to weld differently by infrared welding. Not only are the issues of pigment–polymer interactions present such as the differences in weldability caused by white, black or other pigments, but heating times and depth of heating are likely to be affected by part color. This kind of phenomenon can already occur in conventional hot plate welding when, in some cases, red and black parts weld differently. It can be expected to become even more of an issue with infrared welding. These effects can be easily handled, but workers must be aware of their presence and how to control them.