A polymer is a molecule, made from many joining smaller molecules called monomers. The word “polymer” can be broken down into “poly” (meaning “many” in Greek) and “mer” (meaning “unit”). On this page: Conversational Nylon Types of Nylon What is Crystallinity? Viscosity Extractables Moisture Content Summary Base Resins Overview Fillers, Reinforcements and Additives Comparison of Filler or Additive Physical Properties Nylon is a member of the thermoplastic polyamide (PA) family, and is considered to be the first crystalline plastic. It was invented way back in the 1930’s but introduced for injection molding around 1943. We all know nylon as a strong tough plastic. Why is nylon such a strong material? The basic strength lies in the electrical bonds between molecules. This is the same bond which occurs in nature in fibrous materials such as silk and animal tissue. Interestingly, the tensile strength of the muscle in your arm – at least those of us who have any muscle left – is very close to the tensile strength of nylon. Many years ago when the chemists learned to analyze silk they discovered a very strong bond. From then on they were simply trying to duplicate this bond by using available chemicals. If you were to look through a microscope at a silk fiber and a nylon fiber, side by side, you would see a striking similarity. These early scientists produced, in reality, a synthetic silk. This was nylon.