Glass bonding problem

In addition to the nature of resin and fibre, the laminate properties also depend on the degree of bonding between the two main components and the presence of other additives including air bubbles. Because of this some parts, fabricated by simple hand building techniques, may exhibit strengths no better or even worse than unreinforced materials. This problem is often worst with glass fibres which are therefore normally treated with special finishes to improve the resin-glass bond. 

Because the glass-to-EVA interface bonding problem seemed to be solved when all samples exhibited adherent and persistent bonds, the focus of the effort was shifted to back-sheet adhesion. An additional series of test (see Table II) confirmed the good results of Tedlar with the Du Pont adhesive 68040. Korad 63000 may be a useful material, but cure temperatures during lamination caused some degradation. Additional tests on this acrylic sheet may be run. A polyester film, Scotchpar 20CP, was interesting, because it would be less expensive than a polyvinyl fluoride film, such as Tedlar. This test series showed that a new primer or adhesive was needed for the Scotchpar film. 

The glass-bonded alumina described in Problem 9.15 is to be used as a grinding ball for ball-milling operations. In the initial development, a series of tests was performed and the results were as follows ... 

Polypropylene can be fabricated by almost any process used for plastics (see Plastics processing). The extmsion of pipe and injection mol ding of fittings present no unusual problem. However, there is no way to bond the fittings to the pipe except by remelting the polymer, which is impractical on most constmction sites. The resin can be reinforced by glass fibers, mineral fillers, or other types of fillers and can be pigmented readily. 

Creep of polymers is a major design problem. The glass temperature Tq, for a polymer, is a criterion of creep-resistance, in much the way that is for a metal or a ceramic. For most polymers, is close to room temperature. Well below Tq, the polymer is a glass (often containing crystalline regions - Chapter 5) and is a brittle, elastic solid -rubber, cooled in liquid nitrogen, is an example. Above Tq the Van der Waals bonds within the polymer melt, and it becomes a rubber (if the polymer chains are cross-linked) or a viscous liquid (if they are not). Thermoplastics, which can be moulded when hot, are a simple example well below Tq they are elastic well above, they are viscous liquids, and flow like treacle. 

The theory of mechanical interlocking explains adhesive bonding with the physical coupling of surface irregularities, roughness. It can be applied for the solution of problems emerging in the textile and paper industry, but cannot describe adhesive interaction of smooth surfaces like in the case of glass. 

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