Table 4.
General characteristics, manufacturing conditions, and mechanical properties in the reuse of recycled CF and CFRP.
| Feedstock | Recycling Process | New Matrix Material | Conditions for Manufacturing | Mechanical Properties (rCF or Composite) | Ref. |
|---|---|---|---|---|---|
| CFR epoxy | Crushing | ABS/PP 1 | Pelletizing of CFRTP (CFRP + thermoplastic polymer) using a two-axis pelletizing machine, followed by injection moulding | Composite: 24% fiber volume fraction seems to be a limit for mechanical properties | [99] |
| CFR epoxy | Mechanical cutting (chopping) | Epoxy | Fibers are converted to non-woven mats by a wet papermaking process. Compression moulding at 7 MPa | rCF: 98.1% TS 1, 95.6% TM 2 compared to virgin fibers | [38] |
| CFR epoxy and CFR bismaleimide | Mechanical cutting, pyrolysis at 400 °C, cleaning with water washing, including ultrasonication + fiber drying | PPS | Pelletizing using twin-screw extruder: throughput 3 kg/h, screw speed 150 rpm, die temperature 315 °C and cooling in air. Manufacturing by moulding press at 290–305 °C |
Composite: 680% TM, 720% TS, 250% impact energy increase, when compared to PPS | [68] |
| CFR epoxy | Total cure of prepregs for 5 h at 100 °C. Mechanical shredding and sieving. Fluidized bed at 550 °C, followed by oxidation at 850 °C | PP | Compounding: using twin-screw extruder, L/D ratio 25:1, screw speed 50 (lower fiber damage)–80 rpm, coupling agents (2–8%) Injection moulding: nozzle temperature 200–210 °C, mould temperature 50 °C, hold pressure 12 MPa, back pressure 47.5 MPa |
Composite: 150% TS increase when incorporating coupling agents (5% wt.) compared to composite with no coupling agents | [100] |
| rCF from CFR epoxy | As-received: Pyrolysis at 500 °C for 10 min, and cut | PP | Carding and wrap spinning process. Hot compression moulding, at 220 °C, 2 MPa for 15 min | rCF: retains 90% TS and 93% TM compared to vCF Composite: rCFRP with 27.7% volume fraction has 50% higher TS and FS 3 compared to rCFRP with 15% volume fraction |
[101] |
| CFR epoxy | Crushed using rotating blade, ball milling process | ABS | Mixing, grinding and injection | Composite: Higher TS when higher content in CF, but drops dramatically at 70% (in weight) | [54] |
| CFR epoxy | Mechanical cutting, pyrolysis at 500 °C followed by oxidation at 500/600 °C | Epoxy | rCF chopping, oxidation (optional), mixing with epoxy resin and hot pressing at 110 °C, 4.5 MPa, for 40 min | rCF: 65–95% TS when compared to vCF | [102] |
| CFR epoxy | Solvolysis in water and acetone (20:80 in volume) | Epoxy | For rCF: manually alignment, impregnation with resin, and vacuum in bag. Cured at room temperature for 16 h and post-cured at 75–80 °C for 1 h For rCF plies: alignment, impregnation with resin, followed by curing in hot press at 60 °C, 3.5 MPa, for 5 h |
rCF: >90% TS, compared to vCF | [88] |
| CFR polybenzoxazine | Mechanical crushing, followed by pyrolysis at 500 °C | LDPE 4 | For blending, roll mill: speed 10–20 rpm, roll temperature 150–180 °C. Grounded and hot pressed at 34.5 MPa at 180 °C | rCF: Some combinations of rCF + additives show similar properties to vCF composites | [103] |
| CFR PEEK | Electrodynamical fragmentation, 6 cycles of 100 pulses, 180 kV, frequency 5 Hz, followed by sieving | PEEK | Compression moulding, 20 ton clamping force, heated at 360 °C for 3 min, cooled at a rate of 20 °C/min | Composite: rCFRP mechanical performance is 17% lower than novel composite | [58] |
| PAN-rCF | Unknown | PC 5 | Pelletizing using twin-screw extruder: screw speed 100 rpm, die temperature 230–250 °C. Injection (biocarbon fillers + rCF) at 80–120 MPa, at 250 °C | Composite: 35% TM 270% TS increase, compared to the reference PC-biocarbon composite | [104] |
| CFR epoxy | Pyrolysis in molten ZnCl2 at 360 °C | Epoxy | Manual lay-up, cured at 80 °C for 2 h and at 150 °C for 4 h in oven. | rCF: 95% TS retention after pyrolysis in molten ZnCl2, 80% TS retention after pyrolysis in air, compared to vCF | [73] |
| rCF | Pyrolysis. Two treatments for resizing: Acetone washing and drying in oven Acidic treatment in a bath of 65% HNO3 for 20 min at 60 °C, followed by drying in oven |
PP/PA6 6 | Preparation of films with 1–5% (in weight) of solids content. Drying for 12 h at 80 °C. Chopping of fibers. Compounding in a twin-screw microcompounder at 80 rpm, 190 °C for PP, 230 °C for PA6, compounding time 1 min | Composite: No effect of PP sizing, slight positive effect of PU 7 sizing on TS and TM | [105] |
1 Tensile strength; 2 Tensile modulus; 3 Flexural strength; 4 Low density polyethylene; 5 Polycarbonate; 6 Polyamide 6; 7 Polyurethane.