SYNOPSISThe improvement of toughness and heat resistance of phenolic resin was examined by blend of novolac and copolymers prepared from p -hydroxyphenylmaleimide ( HPMI ) and acrylic ester. Copolymers of HPMI and acrylic esters, such as methyl acrylate, ethylacrylate, n -butylacrylate, or 2-ethylhexyl acrylate, were synthesized. Average molecular weights, glass transition temperatures ( T,) and thermal decomposition temperatures were measured.The miscibility of the copolymers with novolac was evaluated. It was found that these copolymers had higher average molecular weight and higher thermal decomposition temperature than those of novolac; they also had good miscibility with novolac. Molding compounds were prepared by hot roll-kneading of mixtures, which involved novolac, the copolymer, hexamethylenetetramine ( hexamine) , and glass fiber. Test pieces of the modified phenolic resins were prepared by transfer molding from the molding compounds. It was found that phenolic resin, modified with HPMI/ethylacrylate copolymer or HPMI/nbutylacrylate copolymer, which consisted of numerous units of acrylic ester, showed both good toughness and good heat resistance. I NTRO DU CTlO NPhenolic resin is used widely as an industrial material because of its good heat resistance, electrical insulation, dimensional stability, and chemical resistance. Recently, improvement in properties, especially toughness and heat resistance, have been required particularly for the industrial field. However, the improvement of mechanical properties, especially toughness, is usually incompatible with the improvement of heat resistance.Many approaches have been tried attempting to improve the heat resistance of phenolic resin. Fukuda et al.' have improved the heat resistance of the phenolic resins by means of the after-cure or an increase in hardening agent content. It was reported2 that high temperature phenolic resins were produced by the addition of a modifier that has good heat re-* To whom correspondence should be addressed. In the previous article5 it was found that the modification of phenolic resin with HPMI/styrene copolymer improved both flexural strength and heat resistance, but didn't much improve the toughness. It is expected that phenolic resin modified with HPMI /acrylic ester copolymer has higher toughness than the phenolic resin modified with HPMIlstyrene copolymer, because HPMI/acrylic ester copolymer is more flexible than HPMIlstyrene copolymer. Therefore, we studied the heat resistance and mechanical properties, especially toughness, of phenolic resin modified with copolymer prepared from HPMI and acrylic ester.In this study, copolymers of HPMI and acrylic ester, such as methylacrylate (MA), ethylacrylate (EA) , n-butylacrylate ( n-BuA) , or Z-ethylhexylacrylate (EHA), were synthesized and identified by 'H-NMR. Average molecular weight, Tg, and thermal decomposition temperature of the copolymers were measured by gel permeation chromatography (GPC ) , differential scanning calorimetry (DSC) , and thermogravimetry (TG) , respecti...

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SYNOPSISWe studied the improvement of heat resistance and mechanical properties of phenolic resin modified with polymers prepared from p -hydroxyphenylmaleimide (HPMI) . Homopolymss of HPMI and copolymers of HPMI with some vinyl monomers were synthesized and M,, Tg, and thermal decomposition temperature of them were measured by GPC, DSC, and TG, respectively. The miscibility of homopolymer with novolac was examined by DSC. It was found that the homopolymer had good heat resistance and good miscibility with novolac. Molding compounds were prepared by hot roll-kneading the mixtures of novolac, the homopolymer, hexamethylenetetramine, and glass fiber. It was found that molded test pieces had good heat resistance.

SYNOPSISThe improvement of heat resistance and mechanical properties of phenolic resin was examined with the blend of novolac and copolymers prepared from p -hydroxyphenylmaleimide (HPMI) and styrene.Copolymers of HPMI and styrene with various molecular weights were synthesized.Glass transition ( T,) and thermal decomposition temperatures of the copolymers were measured by differential scanning calorimetry (DSC ) and thermogravimetry ( T G ) , respectively. The miscibility of the copolymers with novolac was examined by DSC.It was found that the copolymers had a good heat resistance and a good miscibility with novolac. Molding compounds were prepared by hot roll-kneading of mixtures that involved novolac, copolymer, hexamethylenetetramine ( hexamine ) , and glass fiber. It was found that the test pieces prepared by transfer molding from the molding compounds showed a good heat resistance and better mechanical properties than phenolic resin modified with HPMI homopolymer. INTRODUCTIONPhenolic resin is a widely used industrial material because of its good heat resistance, electrical insulation, dimensional stability, and chemical resistance. Recently, improvement in properties, especially heat resistance and mechanical properties, are required particularly for the industrial field. However, the improvement of mechanical properties are usually incompatible with the improvement of heat resistance. Many approaches have been tried to improve the heat resistance of phenolic resin. Fukuda et al.' improved the heat resistance of the phenolic resins by means of after-cure or an increase of hardening agent content. It was reported' that phenolic resins with good heat resistance were produced by the addition of modifier. But in these approaches mechanical properties of phenolic resin, e.g., flexural strength or impact resistance, were reduced. There are a few paper^^.^ related to the modified phenolic * To whom correspondence should be addressed. resins of which both heat resistance and mechanical properties are superior to those of unmodified phenolic resin.In the previous paper,5 it was found that the modification of phenolic resin with p -hydroxyphenylmaleimide ( HPMI ) homopolymer improved the heat resistance, but didn't improve the mechanical properties so much. The reasons for these were as follows: (1) HPMI homopolymer had a stiff main chain, a high glass transition temperature, and a good heat resistance; ( 2 ) HPMI homopolymer had a higher molecular weight than that of novolac; ( 3 ) the modified phenolic resin could form a higher degree of crosslinking because HPMI homopolymer was miscible with novolac and reacted with hexamine. It is expected that the modified phenolic resin with HPMI / styrene copolymer has better mechanical properties than those of the modified phenolic resin with HPMI homopolymer because HPMI/ styrene copolymer is more flexible than HPMI homopolymer.In this study, HPMI/styrene copolymers with various molecular weights were synthesized and Tg and thermal decomposition temperatures of the copolyme...

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