Polyvinyl chloride, the material found in most credit cards, can liquify at 160 degrees Celsius or 320 Fahrenheit. However, the cards are made of several layers of plastic laminated together. The core is made from polyvinyl chloride acetate. The resin gives it the proper consistency and the correct appearance. There are thin layers of PVCA laminated to the core, which are afixed by heat and pressure. Issues involved with quality control have to do with the inks and the plastic raw materials. They must be prepared under specific conditions of temperature or else, they may become damaged or broken. They must be molded properly to avoid defects. Under the hot sun, heat energy will be absorbed by the plastic, causing the credit card to not actually melt, as the temperature isn't high enough, but to warp.