Hexahydrophthalic anhydride HHPA

Resing and Moniz 60) cured DGEBA with three different curing agents, piperidine, hexahydrophthalic anhydride (HHPA) and nadic methyl anhydride (NMA). Spectra were collected with C-13 NMR using cross polarization and high power decoupling. 

After the primary amines, acid anhydrides are the next most important class of epoxy curing agents, although these are not used as often in adhesive systems as they are in casting compounds, encapsulants, molding compounds, etc. The most common types of anhydrides are hexahydrophthalic anhydride (HHPA), phthalic anhydride (PA), nadic methyl anhydride (NMA), and pyromellitic dianhydride (PMDA), although there are several others. Chemical structures of several anhydrides are illustrated in Fig. 5.6. 

Hexahydrophthalic anhydride (HHPA) is a low-melting-point (36°C) solid. It is liquefiable at temperatures of 50 to 60°C and can be mixed easily with hot epoxy resins. The mixed resins are characterized by low viscosity, long pot life, and low exotherm. Because of its low reactivity HHPA is generally used with an accelerator, usually BDMA or DMP-30. 

Most of the data reported here will be concerned with bisphenol A epoxy resin systems cured with the liquid anhydride, 1-methyltetrahydrophthalic anhydride (the Union Carbide commercial designation for this material is ZZLA-0334). However, these quaternary phosphonium compounds have also been shown to be effective with other anhydrides such as hexahydrophthalic anhydride (HHPA). 

In Table II, the IDT s obtained by curing various diglycidyl-hydantoins with hexahydrophthalic anhydride (HHPA) are shown. 

Casting. Castings of liquid epoxy resins cured with hexahydrophthalic anhydride (HHPA) were prepared by heating the liquid resin in a stirred 3-necked flask to which the calculated amount of premelted HHPA was added. A vacuum was drawn to partially degas the mixture then 2 phr benzyldimethylamine (BDMA) was added as accelerator. After further degassing, the mixture was poured into casting molds prepared as described above. The filled molds were put into an oven at the desired gelling temperature subsequently, either the oven was reset to the final cure temperature or the molds were transferred to a second oven, as convenient. 

The presence of hardener hexahydrophthalic anhydride (HHPA) in the blends completely changed the miscibility behavior of the blends. All the blends became heterogeneous upon adding HHPA. The phase behavior of the ternary blends was evident from the phase diagrams given in Fig. 21.2. 

Hexahydrophthalic acid diglycidylester (HHPD)/ hexahydrophthalic anhydride (HHPA)/Oligoester... 

Epoxy resins resulting from the reaction of diepoxide (Araldite F) with different hardeners methylte-trahydrophthalic anhydride (MTHPA), hexahydrophthalic anhydride (HHPA) and phthalic anhydride (PA) exhibit unlike availability to oxidation. The cycloaliphatic systems are more stable than the aromatic one and the order of thermal stability stated after the analysis of CL data is [93T1] ... 

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