The importance of fabric structure in laminates
Glastic channels make use of fiberglass that has been reinforced with polyester to take advantage of the individual properties of the materials. Polyester is a common base material used for laminates because of its strength, durability, cost and stretch. Most fiber structures make use of fabric instead of mesh or film. In order for the fabric to gain more strength and environmental resistance, it is coated with a synthetic material that can be woven fiberglass coated with PTFE and silicone or polyester that is laminated and coated with PVC. Polyester laminated or coated with PVC is generally less expensive and can be effectively used for long term applications.
Woven fiberglass that has been coated with PTFE is also widely used as base material because of its high ultimate tensile strength. It behaves elastically and it does not undergo any significant stress relaxation or creep. The glass fibers are drawn into continuous filaments that are bundled into yarns. The yarns are later woven into a substrate. The PTFE coating is chemically inert and it able to withstand temperatures from -73oC to 232oC. It is also immune to UV radiation and can easily be cleaned with water. Because of the differences on how polyester and fiberglass performs in fire resistance tests, fiberglass that has been coated with PTFE is the only membrane material that meets the US model building codes in their definition of a non-combustible material. There is also a perception that the high melting temperature and lack of creep including its long term elongation makes fiberglass-based fabrics superior to polyester. On the other hand, polyester if properly constructed can also be equally durable because like fiberglass, it melts instead of burns at high temperatures. These are the reasons why glastic channels and sheets are widely acceptable as electrical insulation.
Selection of resin
There are two common types of thermosetting resins used: epoxy or polyester. Epoxy is known for its performance and high price. It is used in weight critical, high strength and dimensionally accurate applications. Polyester resins are more cost effective with the advantages of increased corrosion resistance. Polyester resins are also more forgiving than epoxies and it is for this reason that polyester is more widely used in different industries. The choice however should not depend on the cost of the resin but a careful consideration of fabric compatibility, service conditions and the desired characteristics of the finished product.