Hideki Sembokuya

An approach to chemical recycling of epoxy resin cured with amine using nitric acid

Abstract An approach to chemical recycling of epoxy resin was pursued. Bisphenol F type epoxy resin cured with 1,8- p -menthanediamine could be completely decomposed in nitric acid solution resulting from low corrosion resistance to nitric acid. Organic decomposed products of the resin with the highest yield were extracted from neutralized solution. The extract was repolymerized to prepare recycled resin, mixed with bisphenol F type epoxy resin and curing agent of phthalic anhydride. The mechanical properties of virgin resin and recycled resins were compared. It was surprising that the recycled resins were far superior to the virgin resin in strength. The results obtained from differential scanning calorimeter (DSC) showed that the glass transition temperature ( T g ) of recycled resins was higher than that of virgin resin. The reason that they formed the better network structure was discussed.

Decomposition of GFRP in nitric acid and hydrogen peroxide solution for chemical recycling

Decomposition of Glass Fiber Reinforced epoxy resin cured with amine in nitric acid and hydrogen peroxide solution has been investigated. After specimens were immersed in above solutions for a specific time, glass fiber could be separated from matrix resulting from the decomposition of matrix resin. The chemical structures and molecular weight distributions of the decomposed products were analyzed by FT-IR and size exclusion chromatography (SEC). When nitric acid was used, the resin was mainly decomposed into 2,4,6-trinitrophenol (picric acid) and quasi-monomer. In the case of hydrogen peroxide, the backbone of resin was broken into monomer and dimer, or peracetic acid, depending on immersion time. On the other hand, glass fiber exhibited low corrosion resistance to nitric acid, while it was hardly degraded in hydrogen peroxide. Based on analyzing the decomposed products and observing the degradation of glass fiber, the chemical recycling method on GFRP was proposed.

Decomposition mechanism of epoxy resin in nitric acid for recycling

Bisphenol F type epoxy resin cured with 1, 8-p-menthanediamine was completely decomposed in specified immersion time in nitric acid solution due to its poor corrosion resistance to strong acid. By repolymerizing the decomposed products, an approach to chemical recycling of epoxy resin was proposed. Organic decomposed products of the resin in nitric acid with the highest yield were extracted by ethyl acetate from neutralized solution. The extract was repolymerized to prepare recycled resin, mixed with bisphenol F type epoxy resin and curing agent of phthalic anhydride. The mechanical properties of original resin and recycled resins were compared, as indicated that the recycled resin showed higher strength when the neutralized extract was used to substitute for a part of resin rather than curing agent. Furthermore, in order to investigate these behaviors, the decomposed products were analyzed in detail. The results of size exclusion chromatograph (SEC) and FT-IR showed the extract was mainly nitrated compounds which retained the main chain of epoxy resin, as explained the recycling mechanism that it could prepare recycled resin as quasi-monomer in place of part of epoxy resin.

Thermal shock resistance of hybrid particulate-filled epoxy composites with hard and soft fillers

For improvement in toughness of epoxy casting materials, the technology of filling the epoxy with hard and soft particles is effective. In this study, thermal shock tests were carried out for a hybrid composite system that consisted of silica particulate as hard filler, methacrylate-butadiene-styrene rubber as soft filler and matrix of epoxy resin. The testing method was established by the authors, and the thermal shock resistance of materials could be evaluated by using a disc-type specimen with a sharp notch. Fracture toughness of the hybrid composite materials improved remarkably by using both silica and MBS filler. However, the contribution of particle filling effect to thermal shock resistance was relatively small. These results were mainly due to debonding of silica filler/matrix resin interface.

Delamination Fatigue Crack Propagation Behavior of CFRP Laminates with Two Kinds of CF and Epoxy.

Delamination fatigue crack propagation behavior was investigated for four kinds of CF/epoxy laminates (Toray T300/#3601, T800/#3601, T300/#3631, and T800/#3631). Tests were carried out under mode I opening loading by using double cantilever beam specimens. The effect of reinforcing fiber on the delamination fatigue crack growth behavior was very small. The fatigue crack growth behavior was mainly controlled by matrix resin. The analysis of the equivalent stress intensity range proposed by the present authors indicated that the contribution of maximum load was large in delamination fatigue crack propagation of the laminates tested here. The degree of the contribution of maximum load was higher for more brittle resin. The improvement of the interlaminar fracture toughness was not fully transferred to the improvement of threshold value of the fatigue crack growth. The mechanism of delamination fatigue crack propagation agreed well with the fractographic observation.