High Pressure Laminates (HPLs) are hard, dense materials made by applying heat and pressure to substrate layers impregnated with synthetic resin. When heat and pressure are applied, polymerization transforms the layers into a thermoset industrial laminated plastic. Paper, canvas and glass fabric are the most common substrates. The resins include epoxy, phenolic, melamine, silicone and polyester.HPLs are characterized by low cost, superior heat resistance, high heat deflection temperatures and good electrical properties. Applications include electrical device, mechanical, oil & gas and power generation. Given their use in many electrical applications, the industry generally refers to the materials based on their NEMA rating (The National Electrical Manufacturers Association).