Moisture sensitivity of matrix resins

Moisture diffuses into polymers to differing degrees, which is a function of the morphology and molecular stracture. The following aspects are critical  

The degree of crystallinity in the case of a thermoplastic matrix (although certain modified 

While (1—3) are clearly variables of the matrix, the presence of residuals (4) is not so obvious since this refers to unreacted hardeners and other impurities. Impurities such as calcium, sodium or potassium salts arise from inclusions in fillers or as contaminants on the surface of reinforcing fibres. The sodium and potassium content of glass fibres has been steadily reduced over recent years because they were widely acknowledged as responsible for the water sensitivity of glass fibre composites in aqueous environments. 

For example, an anhydride hardener (with tertiary amine accelerator) will produce a polyester -type structure with low polarity, whereas an amine hardener will form a P-hydroxyl amine network with high polarity. Hydrogen bonding of water molecules at these sites enhances the concentration of moisture which can be absorbed. However, with catalytic curing agents, polyether stmctures of relatively low polarity will form. Since it is quite common to use mixed curing agents for composite matrices, the cured 

Epoxy—cyanate ester Primaset PT30/DEN431 1.96 3.62 96 50 

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