Ken Tsuda

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.

Erosion damage of polymeric material by slurry

Abstract An attempt was made to reveal the erosion mechanism of a plastic material in slurry containing glass beads of approximately 176 μm in diameter. The experimental observations were interpreted in terms of parameters such as the impact velocity Vp, the impact angle α of the beads and the striking efficiency η. A theoretical flow analysis for a solid-liquid two-phase flow was made and it was found that the trajectories of the particles curved as they approached the specimen, indicating that the actual surface onto which the particles were impinging was much narrower than that which would be expected for sand erosion in an air stream. In the slurry erosion the impact velocity and impact angle differed greatly at different positions of the specimen. This is possibly due to the differences in the density and viscosity of liquid and air. Two distinctly different types of erosion were observed: a typical brittle behaviour occurred near a stagnant point, after an initial incubation period, whereas at a distance from the stagnant point only a slight surface roughness was produced. These two different types of erosion produced a clear boundary. Erosion rates depended on the positions of the specimen and were found to be proportional to (Vp sin α)2.6. This suggested that the normal component of the impact velocity of the particle determined the erosion rate of the plastic material due to slurry.

Form and rate of corrosion of corrosion-resistant FRP resins

The corrosion behavior and mechanism of matrix resins for FRP in aqueous solutions were investigated, comparing these with the corrosion of metals. Three forms of corrosion were found, namely surface reaction type, corrosion layer forming type and penetration type. In surface reaction type corrosion, which was recognized in the corrosion of epoxy resin cured with phthalic anhydride in alkaline solution, the ester bonds in the resin were attacked by hydrolytic reaction with liquid and then dissolved from its surface uniformly. In the corrosion layer forming type corrosion, observed in the corrosion of unsaturated polyester in alkaline solution, the ester bonds in the main polymer chain were corroded by the same mechanism, but crosslinked polymer chain remained. Then the corrosion residual layer was formed. In penetration type corrosion, a large quantity of environmental liquid was absorbed until an equilibrium state was reached, and then the strength of the specimen decreased quite remarkably. This type of...

Effect of surface treatment on sand erosion behavior of glass beads-filled epoxy resin

Effects of the adhesion between filler particle and matrix on the erosion rate were studied in cured epoxy resin filled with glass beads having mean diameter 17 um. In order to observe the effect of adhesion on erosion rate. the filler particles were treated with silane coupling agent, silicone oil and washed by acetone as well. The filler content of the specimen was varied and also the specimens were attacked by different size angular particles. The comparison of each type of specimen shows that by using acetone and silicone oil for surface treatment, the erosion rate is relatively high. Whereas the specimen in which the filler was treated by silane have low erosion rate. The difference of erosion behavior is influenced by impacting particle size and filler content. Using small impacting particles and also low filler content, the erosion behavior between silane and acetone treated was quite different. On the other hand, using large impacting particles and high filler content, the erosion behavior between...

Preparation and Performance under Corrosive Environment of Epoxy-Nanocomposite

Epoxy-organoclay nanocomposite were prepared and investigated in terms of mechanical properties and also in term of water diffusion and sulfuric acid corrosion resistance. Diffusion was studied through epoxy samples containing up to 6phr of organically treated montmorillonite. The diffusion of the environmental solution was measured by immersion of the samples in these solutions at elevated temperature with noting the increase in weight as immersion function of time. An evaluation by flexural strength of the nanoclay/epoxy composites samples was made to compare their mechanical performances under corrosive environment as a function of immersion time and temperature.

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.

Evaluation of Corrosion Behavior of Rigid PVC Used for HNO3 Absorption Tower.

13年間使用した硬質ポリ塩化ビニル製硝酸吸収塔 (直径2.6および2.0m, 高さ15m, 厚さ20mm) の腐食状況について検討した.試験片は塔壁マンホール部から, 外層, 中間層および内層について試料を採取し, それらについてクリープ破断強さ, 引張り, 曲げ, 衝撃強さなどの機械的強度を測定し, さらに赤外スペクトル (IR) 分析を行った.IR分析により大気側 (外層) では-OHと>C=O基の生成が, また, 接液側 (内層) では>C=O基とニトロ基の生成が認められた.ステアリン酸バリウムのIR吸収に注目した結果, 外層の大気劣化層, 内層の腐食層の厚さは, それぞれ250および500μmであることが明らかになった.これらの結果より, 硝酸の製造装置用材料として, 従来のステンレス鋼に代わり, 硬質ポリ塩化ビニルが有効であることがわかった.

Evaluation of Thermal Shock Resistance for Cast Epoxy Resin with Various Toughness.

Previously the present authors proposed the testing method of thermal shock resistance using a notched disk type specimen of brittle type epoxy resin and its evaluation method based on fracture mechanics. In order to examine their applicability, some practical epoxy resins for casting were tested in this study.For brittle alicyclic epoxy resin, irrespective of the cooling bath temperature, the nondimensional stress intensity factor calculated by the experimental results agreed well with that of theoretical estimation.In the case of mixed resin of bisphenol A epoxy having certain toughness and very brittle alicyclic epoxy, the critical temperature difference ΔTC was clearly recognized for all resin systems with various mixture ratios, and the resin with higher bisphenol A epoxy content showed higher thermal shock resistance. For the bisphenol A type epoxy resin with longer molecular chains (larger number of repeated units) indicated higher resistance. The analysis agreed well with the experiments for these both resin systems.For the epoxy resin modified with a low content of plasticizer, the same evaluation method of thermal shock resistance was found to be applicable. But over 20phr content, plastic flow occurred markedly, and so the critical temperature difference could not be obtained. For such cases, it is still possible to evaluate the thermal shock resistance by using a large size specimen.