PCB - laminate, manufactured in the form of sheets of cotton fabric impregnated with phenol-formaldehyde resole resin. For the manufacture of PCB different brands used different tissue density and weave. Typically used plain fabric plain weave warp and weft, in which the number of overlapping bases weft max. Sometimes also used fabric of satin weave with fewer weft bases overlap, which increases the tensile strength of the material. Character weave has a significant influence on the other properties of the PCB: the toughness, resistance to splitting, and others. According to the thickness of the fabrics used are divided into light (up to 150 g / m2), medium (up to 300 g / m2) and heavy (over 300 g / m2).
Properties and application PCB.
PCB is available in the form of sheets of different thickness (0.2 to 100mm) of different lengths and widths. Textolite each brand has its own pre-emptive purposes. PCB ornamental marks PT, PTC Class and Class produces a thickness of 0.5 to 70 mm with a smooth light brown or dark brown surface. Textolite grades A and B is the electrical materials.
Properties PCB depend on the type of fabric. The material on the basis of heavy fabric having a higher toughness than the material based on fabric, but on other parameters inferior. The strength of the material is proportional to the number of fabric layers per unit thickness of the material. The highest values are obtained with a ratio of the resin and the fabric of 1: 1 or a close. The properties of the material influence the conditions of pressing. High pressure at 42-48% resin content results in a material with lower physical and mechanical properties. PCB has a high compressive strength, impact and shatter resistant better than getinaks, but slightly below the electrical insulation properties. Properties of the sheets are not identical in the longitudinal and transverse directions, as the strength of the fabric exceeds the strength on the basis of the weft. Compressive strength and flexural strength is much higher in the direction perpendicular to the layers. Splitting strength depends on the strength of bonding fabric layers. This quantity determines the ability of a material to the machined. Water resistance and resistance to splitting often reduced when in violation of the impregnation and drying fabrics and pressing. Higher humidity impregnated and dried fabric and peresushka (reduction of the soluble part of the resin) and insufficient resin content - the main reasons for reducing the strength of gluing layers of fabric.
PCB can be used for a long time at 90-105˚ C under a load of 50-60% of the tensile strength, determined at the operating temperature.
Substitution cotton nylon allows to obtain a material having good electrical insulating properties and a high resistance to moisture and mildew. Such material has a high impact strength and can withstand mechanical handling.
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