B2: IA-based as curing agents

synthesis of IA-derivatives as curing agents for epoxy resins

Epoxy coatings are extensively utilized for coatings of metal and glass surfaces and for flooring applications due to their generally high level of mechanical properties, corrosion protection and chemical resistance. In the last few decades epoxy coatings have evolved from high VOC systems to more environmentally friendly technologies, like high solids coatings, solvent-free coatings, powder coatings, and waterborne coatings. [Volatile organic compounds (VOCs)] are organic compounds that have a high vapor pressure at room temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. In the field of waterborne epoxy coatings the technology has evolved along two fundamental different routes commonly identified as Type I and Type II systems : 1) Type I systems are based on liquid bisphenol A/F epoxy resins, with an EEW <250; 2) Type II systems are based on higher molecular weight,

New developments in waterborne epoxy curing agent technology are often driven primarily by environmental regulations. So the diamines or polyamidoamines for their detrimental effects on the environmental and human health can be replaced with the IA-based curing agents. The diamines and polyamides exhibit different reativity with respect to that of acids and anhydrides. The diamines in presence of mercaptanes as catalysts can induce crosslink reactions of the commercially available epoxy resins at room temperature, while acids and anhydrides need a thermal treatment up to 90-100°C to initiate the polymerization reaction. Depending on the process for coating or adhesive, the crosslinking reactions of commercially available of liquid Bisphenol-A epoxy resins can promoted by IA acid, itaconic anhydride or other multifunctional itaconates. The itaconic anhydride can be obtained by heating above 100°C of IA by removal the water under reduced pressure. Furthermore, multifunctional itaconate can be synthesized by condensation reaction in a similar manner as above reported for IA-based polyesters and monomers (see scheme C2.2). Some preliminary results obtained on the polymerization of commercially available epoxy resins (by Dow Supplier) indicate that IA can induce crosslinking above 90°C in presence of a catalyst such as imidazole. The thermal analysis can reveal that the itaconic acid shows a good reactivity to induce crosslinking reaction above 90 °C of commercially available Bisphenol-A epoxy resin. The phtalyc anhydride will be chosen as reference curing agent for these studies.

advanced polymer materials