Unsaturated polyesters polyester-glass laminates

At about the same time, an allyl resin known as CR39 was introdueed in the United States as a low-pressure laminating resin. This was followed in about 1946 with the introduction of unsaturated polyester laminating resins which are today of great importance in the manufaeture of glass-reinforced plasties. Alkyd moulding powders were introduced in 1948 and have since found specialised applications as electrical insulators. 

Suzuki, Y., Maekawa, Z., Hamada, H., Yokoyama, A. and Sugihara, T. (1993). Influence of silane coupling agents on interlaminar fracture in glass fiber fabric reinforced unsaturated polyester laminates. J. Mater. Sci. 28, 1725-1723. 

Two resins were used to do the first study on laminate construction. The first was a brominated epoxy vinyl ester resin with antimony pentoxide and the second was a brominated unsaturated polyester resin. They were both promoted to cure at room temperature with methyl ethyl ketone peroxide catalyst. The panels were then postcured at 250°F (121°C) for 8 h. Panels were prepared that varied in glass content from 25% to 70% and panel thickness varying from 0.05 in. to 0.25 in. and were tested at the same testing facility. A summary of the FSI test data for the first set of panels tested are shown in Figures 23.1 and 23.2. This graph in Figure 23.1 plots the FSI value versus the panel thickness. This data would indicate that the thickness of the test panel has no effect on the measured... 

Laminating is, furthermore, important as a manufacturing process for composite materials by means of so-called laminating resins (unsaturated polyester, epoxides with substrates such as glass and carbon fibers) for example, in aeroplanes, vehicles and in shipbuilding. In these applications, however, bonded joints in the true sense of the meaning do not occur. 

Unsaturated polyesters find apphcations mainly in two ways polyester-glass-fiber laminates and polyester molding compositions (discussed later). 

Methods of producing FRP laminates with polyesters have been described in Chapter 2. The major process today is the hand layup technique in which the resin is brushed or rolled into the glass mat (or cloth) by hand (see Figure 2.44). Since unsaturated polyesters are susceptible to polymerization inhibition by air, surfaces of the hand layup laminates may remain under-cured, soft, and, in some cases, tacky if freely exposed to air during the curing. A common way of avoiding this difiiculty is to blend a small amount of paraffin wax (or other incompatible material) in with the resin. This blooms out on the surface and forms a protective layer over the resin during cure. 

Although unsaturated polyester resins are often regarded as casting plastics in at least one important use, glass-fiber lamination, they are used as adhesives. The method of binding glass-fiber mats with unsaturated polyesters started in 1942 by U.S. Rubber [1]. 

One of the main uses of polyester resin is to function as the adhesive for glass-fiber lamination. The cross-linking reaction of unsaturated polyesters is exothermic that is, it is accompanied by a rise in temperature. Indeed, one of the useful features of an inorganic adherend functioning also as a reinforcing agent in these resins is that the heat of reaction... 

The ribs were manufactured from FRP composites. The laminate used glass fibres in tissue form and rovings as additional reinforcement, embedded in a matrix of unsaturated polyester (PU) resin. A gel coating provides protection. 

The materials in this group are linear copolyesters. One of the dicarboxylic acids is an aliphatic unsaturated diacid. The unsaturation is introduced into the polymer backbone for the purpose of subsequent crosslinking. Unsaturated polyester technology was developed for use in glass fiber laminates, thermosetting molding compositions, casting resins, and solventless lacquers. 

Several different processes can be used to produce a laminate. In what is called the hand application process, for example, glass-fiber mats are impregnated with unsaturated polyester resins. The impregnated mats are then removed from the mold by hand and pressed between rollers. The final molding is effected by cold pressing. The method is suitable for small numbers of objects with large surface areas (e.g., boat hulls). 

Chlorostyrenated polyester n. An unsaturated polyester resin made by reacting a fluid polyester with monochlorostyrene in place of styrene See polyester, unsaturated). Monochlorostyrene is less volatile and more reactive than styrene, providing faster cure rates and increased flexural strength and modulus in glass-fiber laminates. 

The macroscopic composites are those in which one or both phases tend to have structures large enough to be easily seen with the naked eye. These include paint hlms (paint itself is usually a particulate composite), adhesive joints, and foams (e.g., the familiar polystyrene foams used for coffee cups because of their low heat transfer coefficient). The fabric laminates alternate layers of inorganic cloth and plastic. An important subclass usually has multiple layers of glass cloth or chopped fiber interspersed with layers of unsaturated polyester-styrene AB-cross-linked materials see Section 2.7.3. These sheet molding compounds are widely used for the hulls of pleasure boats, because they are light weight and very puncture resistant, as well as for automotive bodies see Section 13.9.1. 

Dieu T, Liem N, Mai Y, Tung N (2004) Study on fabrication of BMC laminates based on unsaturated polyester resin reinforced by hybrid bamboo/glass fibers. JSME Int J Ser A 47 570-573... 

It is possible to cross-link unsaturated linear polyester chains directly one to another however, reaction is slow and a low degree of cross-linking is achieved. These limitations are overcome by the introduction of a material which forms bridges between the chains. The materials most commonly used to cross-link unsaturated linear polyesters in this way are vinyl monomers. The addition of a liquid vinyl monomer to the polymer also leads to a reduction in viscosity and this facilitates the impregnation of glass-fibre in the preparation of laminates. 

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