Glass-Reinforced Materials

These are the polycondensation products of dlcarboxylic acids and diols. Dacron or terylene Is the best known example of polyesters. It is manufactured by heating a mixture of ethylene glycol and terephthallc acid at 420 to 460 K In the presence of zinc acetate-antimony trioxlde catalyst as per the reaction given earlier. Dacron fibre (terylene) is crease resistant and is used In blending with cotton and wool fibres and also as glass reinforcing materials in safety helmets, etc. 

The majority of COCs use norbornene and ethene as comonomers. However, heat curable compositions have been described (41). These compositions find use in glass reinforced materials. 

P Kelly, M Jaeger and B Schwanewilms, The use of glass reinforced materials to solve corrosion problems in the chemical process industry , EUROCORR 97, Proceedings of the European Corrosion Congress, 1997, Vol II, pp 235-245. 

ISO Plastics—Glass reinforced materials—Determination of tensile properties... 

Phenol-formaldehyde was reported as the first commercially synthetic polymer (1899) which was introduced as BakeliteT by Baekeland in 1909. This was the period which marked the dawn for the production of commercial synthetic thermosetting polymers. Other advances in the field included the discovery of urea-formaldehyde resins in 1884 and the beginning of their commercialization as Beetle moldable resin in 1928, followed by thiourea-formaldehyde (1920), aniline-formaldehyde (Cibatine by Ciba, 1935) and melamine-formaldehyde (1937) moulding powders. The year 1909 marked the discovery of epoxy compounds by Prileschaiev, which were not used until World War 2. The first thermoset polyesters, invented by Ellis, date back to 1934 and in 1938 was reported their first use in the forms of glass-reinforced materials [1]. 

The crystallisation kinetics of the composites are affected by the nucleating effects of the polymer liquid crystal interlayer and the glass fibre. When both components are present the glass fibres dominate the nucleation kinetics. This is also reflected in the degradation kinetics, where complete degradation of the matrix occurs at lower temperatures for the glass reinforced materials. 

In many cases several different fillers are used in a composite material. The use of a clay with fiber glass is one typical combination. The clay is used to add bulk and improve primarily the compression properties while the fiber glass is used to improve the tensile and compression properties. The relatively inert extender also reduces the coefficient of thermal expansion and improves the thermal conductivity which is advantageous in many cases. Colloidal silica is also frequently added to glass reinforced materials to improve the tensile properties by stiffening the resin phase. Beryllium fillers greatly increase the thermal conductivity. 

For fan shrouds the main requirement is for rigidity, often in quite thin sections, rather than impact strength. Glass reinforced materials are therefore almost universally used, especially reinforced PP, with SMC and GMT-PP increasingly evident as well as reinforced nylon. In the 1980s Peugeot... 

Specialist materials include buried capacitance laminate for wireless communication interconnects, servers and measuring instrument applications. This is a 0.002 inch thick glass reinforced material with double treated copper foil on both sides. The key features of this product are claimed to be improved electrical performance, excellent dielectric thickness accuracy and excellent electrical integrity. 

Furthermore, the dielectric constant is not really a constant. As just implied, the dielectric constant will vary with frequency. It will also vary with temperature and humidity. So besides test method, the frequency, temperature, and humidity conditions must also be considered. Last, even with the same material type, variations in resin content (resin-to-reinforcement ratio) also affect the dielectric constant.These variations will be further discussed in Chap. lO.Table 8.7 shows dielectric constants for some common fiberglass (E-glass) reinforced materials at 50 percent resin content. 

In general, glass-reinforced materials tend to be more expensive than nonreinforced materials. 

Increasing temperature will decrease the LPV and increase the wear rate of glass-reinforced materials containing TFE. 

Compression molding is similar to solid-phase molding except the glass-reinforced materials are... 

With the exception of glass-reinforced fluorocarbons, such as polytetrafluoroethylene and fluo-rinated ethylene-propylene, most all materials can be ultrasonically welded. Table 5-5 compares the welded strength of several glass-reinforced materials. However, horn wear problems can arise from the abrasiveness of the fiberglass. This problem is usually minimal with less than 20% glass. Welds can be made with glass levels between 20 and 35% but some wear will result. Strong welds cannot be assured at levels above 35% due to insufficient fusable resin . 

TABLE 5-4. ULTRASONIC WELDING GLASS-REINFORCED MATERIAL... 

Cost reductions may also result because adhesives permit the use of materials or designs which would not otherwise be possible. The current trend toward the use of plastics, especially glass reinforced materials, which permit smooth contours and the easy fabrication of complex shapes, depends heavily upon the use of adhesives. Plastics, in general, are not weldable nor do they always permit the use of mechanical fasteners. Adhesives have been able to meet the joining needs of these materials with the result that products as diverse as boats, aeroplanes, office equipment, and appliances have become widely available at competitive prices. 

The cheapest glass-reinforcement material is E-glass, often used as a roving, or a collection of parallel continuous filaments. Among the polymer matrices, polyester and epoxy resins, which we discuss shortly, are commonly employed. An unsaturated polyester prepolymer is first prepared by reacting maleic acid with diethylene glycol ... 

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