Methods for recycling reinforced composites
a composite material and reinforced technology, applied in the field of composite materials and epoxy compositions, can solve the problems of inability to re-melt and re-form materials without decomposition, difficult removal, recycling and reworkability, and high cost of raw materials that go into composite construction. achieve the effect of easy control
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example 1
Synthesis of Curing Agent A
[0042]
[0043]N-(2-hydroxyethyl)phthalimide (1000 g), paraformaldehyde (157 g), and p-toluene sulfonic acid (6.8 g) were placed in 1.5 L of toluene in a 5 L round bottom flask equipped with Dean Stark apparatus. After 20 hours at reflux, the reaction was cooled to ambient temperature. Then 2 L of petroleum ether (bp: 60-90° C.) was added to the reaction mixture. The white precipitate was collected by filtration and washed with 1 L of petroleum ether and dried to yield 950 g of crude protected diamine. The crude diamine was deprotected by treatment with 3.4 L of 20% aqueous NaOH at reflux. After 10 h at reflux, the reaction mixture was cooled to ambient temperature, extracted with chloroform / isopropanol (3:1). The organic phase dried with anhydrous Na2SO4, and then distilled under vacuum to yield 200 g of curing agent A (Bp=71-72° C. @ 70 Pa): 1H NMR (CDCl3, 400 MHz): 4.74 (s, 2H), 3.59 (t, J=5.2 Hz, 4H), 2.89 (t, J=5.2 Hz, 4H).
example 2
Synthesis of Curing Agent B
[0044]
[0045]N-(2-hydroxyethyl)phthalimide (1000 g), 2,2-dimethoxypropane (280 g), and p-toluene sulfonic acid (8 g) were placed in 1.5 L of toluene in a round bottom flask equipped with Dean Stark apparatus. After 20 hours, the reaction was cooled to ambient temperature and then 2 L of petroleum ether (bp: 60-90° C.) was added to the reaction mixture. The white precipitate was collected by filtration and washed with 1 L of petroleum ether and dried to yield 900 g of crude protected diamine. The crude diamine was deprotected by treatment with 80% hydrazine hydrate (460 g) in ethanol (600 mL) at reflux. After 10 h at reflux, the reaction mixture was cooled to ambient temperature and the precipitate was filtered from the solution and washed with ethanol and dichloromethane, respectively. The organic phases were combined, dried with anhydrous Na2SO4, and then distilled under vacuum to afford 200 g of curing agent B (Bp=61-64° C. @ 80 Pa): 1H NMR (CDCl3, 400 MH...
example 3
Preparation of a Reworkable Epoxy Composition and Fabrication of a Carbon Fiber Composite
[0046]A reworkable epoxy composition was prepared by blending curing agent A (20 g) and a bisphenol A epoxy resin 828 (112 g, epoxy equivalent weight=185-192) at room temperature. This composition was used to fabricate a carbon fiber reinforced degradable epoxy composite using a wet lay-up method. Three pieces of woven carbon fiber fabric (3K) were used. After a final stage cure (2 h at 80° C., then 1 h at 125° C.), a carbon fiber composite obtained.
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