While Trex is a very well known brand in composite decking and the leader in the industry, there are many other brands, made by a number of different companies, and made of different combinations of materials. Generally, composite decking is a board made of basically sawdust and a binding agent and covered with a thin layer of plastic. I don't believe that the word "sawdust" is used in the industry. You will also almost never see the term "plastic" used. The terms used are PVC or HDPE, etc. which are acronyms for their chemical components, typically, but not always recycled from plastic bags and soda bottles. It is the (plastic) outer layer that has the color and the faux wood texture. It is also this layer that is most vulnerable to heat damage. Each manufacturer will use its own formulation of the HDPE or PVC, so they are not all the same. Often, but not always, the manufacturer will promote the particular qualities of its proprietary formula that make its brand superior. We have been doing a lot of research into the composite decking industry and will be sharing it with our readers over the coming weeks.