Recovery of carbon fiber-reinforced polymer waste using dimethylacetamide base on the resin swelling principle

Abstract

The mechanical recycling method of the carbon fiber-reinforced polymer (CFRP) has the advantages of simple process, less pollution and low cost, but only low utilization value of carbon fibers in powder or short fibers form can be obtained. To reduce the length and strength loss of the recycled carbon fibers, a novel and cost-effective dimethylacetamide (DMAC) swelling technique was developed to achieve rapid delamination of the CFRP laminates under mild conditions (120°C–160°C, 1 h). The corresponding swelling ratios and mass-loss rates of cured epoxy resin (CEP) were about 121.39%–157.39% and 0–0.69%, respectively. Excessive swelling of CEP in DMAC resulted in the cracking of the resin matrix between the adjacent carbon fiber layers. Thus the CFRP laminates were delaminated into soft single carbon fiber layers, which showed excellent cutting performance and reinforcing properties. The delamination products were cut into thin strips of different sizes and vacuum bag molded into new CFRP laminates. The flexural strength and tensile strength of the newly produced CFRP laminates were about 76.38%–90.98% and 94.61%–98.54% of the original CFRP laminates, respectively. More importantly, the chemical compositions of DMAC and CEP were unchanged during the physical swelling process. No organic pollutants (caused by resin degradation) were generated. And the used DMAC can be easily recycled by filtration. Therefore, this study provides a strategy for low-cost and high-valued recycling of CFRP waste.

Catalytic Recycling of Thermoset Carbon Fiber-Reinforced Polymers

“…It can be inferred that aluminum was deemed a stronger Lewis acid compared to iron for coordinating with the electron pair of nitrogen (for a proposed mechanism see Scheme 3). DMAc demonstrated a remarkable swelling impact on CFRPs 65 and also good compatibility with the catalyst, and it significantly aided the recycling process. As depicted in Figure 1, subjecting the cured epoxy polymer to a 5 h duration at 160 °C resulted in an expansion of the polymer size and dimensions.…”

“…DMAc demonstrated a remarkable swelling impact on CFRPs and also good compatibility with the catalyst, and it significantly aided the recycling process. As depicted in Figure , subjecting the cured epoxy polymer to a 5 h duration at 160 °C resulted in an expansion of the polymer size and dimensions.…”

“…64 Furthermore, in 2022, Li et al reported an study involving the use of dimethylacetamide (DMAc) to exploit its swelling properties for carbon FRP waste, aiming to achieve the delamination of CFRP laminates. 65 Additionally, carbon fibers were chemically recovered from carbon fiber-reinforced bismaleimide resin by utilizing Ca(NO 3 ) 2 in supercritical acetic acid at 240 °C for 10 h. 66 Also a benzoxazine−epoxy composite was recycled with an oxidation agent and RuCl 3 as a catalyst. 67 Taking the above-discussed behavior of Lewis acids into account that they are able to cause a cleavage of the C−N bonds in polymerized epoxy resin, we present here a novel study on the recycling of CFRP composites under mild conditions (temperature <200 °C).…”

“…Electrochemical recycling considers as another method . Furthermore, in 2022, Li et al reported an study involving the use of dimethylacetamide (DMAc) to exploit its swelling properties for carbon FRP waste, aiming to achieve the delamination of CFRP laminates . Additionally, carbon fibers were chemically recovered from carbon fiber-reinforced bismaleimide resin by utilizing Ca­(NO 3 ) 2 in supercritical acetic acid at 240 °C for 10 h .…”