Content Knowledge

Students can find information on the make up of different types of balls and how they relate to a given sport on the web.

The simplest definition of a polymer is something made of many units. The units, or monomers, are made up mostly of carbon and hydrogen atoms and are linked together to make a chain from at least 1000 atoms to many 1000's of atoms in a row. While some polymers, like polyvinyl acetate (Elmer's Glue) can exist in the liquid state at room temperature, they can be made more solid or gel-like by the addition of a crosslinker. A crosslinker is a small molecule or ion which bonds to two different polymer strands and restricts the movement of the individual polymer strands. This causes the characteristics of the polymer to become more gel-like and less fluid. Since a new substance is formed by the addition of the crosslinker, a chemical change has taken place.

Scientists continue to develop cheaper, stronger, and better polymers. One method of accomplishing this is through compounding, or the addition of a variety of materials to a polymer during the manufacturing process. The goal is to make the best product possible and assure trouble-free manufacturing of the product. Additives change the properties and/or improve the ease of processing the polymer. The final product performs better and can be offered at lower cost to the consumer. Additives may be fillers (extending agents), reinforcers, antioxidants, heat and ultraviolet stabilizers, flame retardants, plasticizers, colorants, lubricants, foaming agents, and antistatic agents. The borax used in this activity, a crosslinker, can be considered an additive here.