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Coatings Technology Handbook 2010 Part 15

Tham khảo tài liệu 'coatings technology handbook 2010 part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Radiation-Cured Coatings 97-7 available. There has been a trend to increase molecular weight by alkoxylation of compounds used to make multifunctional acrylates to give them better handling and health characteristics. Monofunctional compounds useful as reactive diluents include N-vinyl-2-pyrrolidone 2-ethylhexyl acrylate dicyclopentadiene acrylate hydroxyalkyl acrylates hydroxylactone acrylates and ethoxyethoxyethyl acrylate. Specific formulations are highly varied and performance requirements guide or dictate ingredient levels. Many formulations can be found in the cited literature or other literature available from material manufacturers. 97.3.2.2 Cationic or Epoxy Systems The most important formulating ingredient in a cationic UV cure system is a cycloaliphatic epoxide of the 3 4-epoxy cyclohexylmethyl-3 4-epoxy cyclohexane carboxylate or bis 3 4-epoxy cyclohexylmethyl adipate type.53 Systems usually contain from 100 to about 30 to 49 cycloaliphatic epoxide. When this epoxide is used alone or at very high concentrations strong hard and brittle coatings that are useful on rigid substrates result. These rigid coatings can be flexibilized and toughened in various ways. Although commercial compounded flexibilizers tougheners exist20 for these systems various polyols such as the propylene oxide54 or caprolactone polyols55 can be used. Polyester adipates can be used but the relatively high acidity of these polyols can lead to shortened shelf life because the cycloaliphatic epoxides are well-known acid scavengers56 and will readily react with any carboxylic or other acid groups in this system. This will either increase viscosity or cause gelation. Other flexibilizing agents include epoxidized soybean and linseed oil epoxides and epoxidized polybutadiene. Care should be exercised when incorporating these compounds in the formulation because they can cause significant softening along with flexibili-zation and little or no increase in toughness. Relatively small amounts 1