Esterification of epoxy resins with fatty acids at 260° occurs in two stages (1) addition of one fatty acid molecule to an epoxy group to form a hydroxy‐ester, (2) esterification of the original and of the so‐formed hydroxy groups. The curing process of epoxy resins with amines has been studied by infra‐red spectroscopy, and by measurement of the material produced which is non‐extractable by solvents. The combined data provide some indication of the curing mechanism.
Flame-retardant paints have been devdoped which can considerably upgrade the performance of combustiile substrates in surface spread of flame tests, but there is uncertainty as to their benefit in a real 6re situation. This is partly owing to the lack of agreement on laboratory test methods and even of their value. Flame-retardant paints commercially available in the United Kiugdom are of two types, the intumescent type and the antimony oxide type, and their meehanirm of action is flkuswd.
Cobalt octoate (2‐ethyl hexoate) has been studied by a wide range of spectroscopic and physical techniques and found to be polymeric. A structure for the compound is proposed. Its activity as a drier in a surface coating medium is shown to be related to its polymeric state and to the coordinating effect of other components present in the system. Auxiliary metals such as calcium or lead enhance the activity by providing a strong ligand field around the cobalt, facilitating the transition from the cobaltous to cobaltic state. Other metals such as zinc or tin, or polyols reduce the activity by coordination to configurations unfavourable to this change.
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