Thermoset Materials (Fiberglass & Fiberglass Reinforced Plastic)
In the world of plastics, there are two major types of materials: thermoplastic resins and thermoset resins. Thermoplastic materials make up a large part of the common plastics that surround us in everyday life. These materials are solid at room temperature and can be heated to a “liquid” state, injected into a mold, then cooled back into a solid in the form of an object. We use these thermoplastics in the thermoforming process.
The thermoforming process doesn’t bring plastic to a completely liquid state, but instead involves heating a sheet of plastic material up to a temperature in which the sheet becomes malleable or formable. At this temperature, the part can then be molded into the desired shape by using vacuum to pull the hot sheet of plastic against the surface of a mold.
If you heat a thermoplastic material again at a high enough temperature, it will again become a liquid. Due to the fact that they can be returned to a liquid state, thermoplastic resins (especially commodity resins such as Polyethylene, Polypropylene, TPO and ABS) tend to be highly recyclable.
Thermoset resins are formed with a chemical reaction called polymerization. These resins are in liquid form at room temperature and, with the addition of a curing agent, convert from a liquid to a solid. Once cured, or polymerized, a thermoset resin cannot be converted back to a liquid—the process is irreversible.
In manufacturing composites, a number of types and formulations of resins are available. The most widely used polymers include polyester resin, vinyl ester resin and epoxy resin.
The term “composites” literally means “to put together”; that is, to combine different materials. In this case, the thermoset resin is combined with a fiber material known as a reinforcement. The fiber reinforces the resin matrix; that is, the fiber provides the strength and the polymer resin holds the fiber together and provides the product shape. Numerous combinations of resin and fiber enable composites to provide specific properties and meet end-user requirements. The most commonly used fiber reinforcements include glass fiber (fiberglass), carbon fiber, and aramid fiber, more commonly called Kevlar®.
The selection of composites materials and manufacturing process depends on the required finished product properties, the rate of production, and the cost factors for an individual product. We use two major production methods, open molding and closed molding. With open molding technology, the polymer resin is exposed to the atmosphere during the forming and curing process. As implied with closed molding, the process takes place inside a mold cavity where the materials are not exposed to the atmosphere.