Thermal and chemical treatments of recycled carbon fibres for improved adhesion to polymeric matrix

Abstract

The aim of this study is the characterization of recycled carbon fibres, in view of their potential application in long-fibre reinforced thermoplastic composite. The fibres were obtained from epoxy matrix composite panels, applying a patented process that includes the pyrolisis of the matrix followed by an upgrading of the fibres. Then, recycled fibres were further subjected to thermal and acid treatments in order to modify their surface morphology and chemistry. Scanning electron microscopy and energy dispersive spectrometry were used to characterize the morphological and compositional changes of the fibre surface. The fibres were characterized in terms of mechanical properties and adhesion to an epoxy matrix. The fibres treated by thermal processes at high temperatures (600°C) were shown to be too severely damaged, making them unsuitable for the production of fibre-reinforced composites. A thermal treatment at lower temperatures (450°C) involved a very limited damaging without any evident chemical modification of the fibre surface, which in turn involved a limited increase of the adhesion properties to an epoxy matrix. Chemical treatment by nitric acid caused a very limited damage of fibres, coupled with a significant modification of surface chemistry, which in turn involved a further increase of the fibre/matrix adhesion properties.

Keywords

Carbon fibres recycling interfacial strength surface treatments

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References

Pimenta

Pinho

. Recycling carbon fibre reinforced polymers for structural applications: technology review and market outlook. Waste Manage 2011; 31(82): 378–392.

Roberts

. Rapid growth forecast for carbon fibre market. Reinf Plast 2007; 51(2): 10–13.

JEC51. Carbon fiber: investing cautiously. JEC Composites Magazine, September 2009, issue 51.

Pickering

. Recycling technologies for thermoset composite materials—current status. Composites Part A 2006; 37(8): 1206–1215.

European Union. End-of-life vehicle directive. Off J Eur Union 2000; L269: 34–43.

Corvaglia

Passaro

Manni

. Recycling of PP-based sandwich panels with continuous fiber composite skins. J Thermoplast Compos Mater 2006; 19: 731–745.

Rametta R, Felline F, Conte P, et al. In: Proceedings of the international workshop on thermoplastic matrix composites 2003, Gallipoli, Italy, 11–12 Settembre 2003.

Palmer

Ghita

Savage

. Successful closed-loop recycling of thermoset composites. Composites Part A 2009; 40(4): 490–498.

Torres

de Marco

Caballero

. Recycling by pyrolisis of thermoset composites: characteristics of the liquid and gaseous fuels obtained. Fuel 2000; 79(8): 897–902.

10.

Jody

Pomykala

Daniels

. A process to recover carbon fibers from polymer-matrix composites in end-of-life vehicles. JOM 2004; 56(8): 43–47.

11.

Hyde

Lester

Kingman

. Supercritical propanol, a possible route to composite carbon fibre recovery: a viability study. Composites Part A 2006; 37(11): 2171–2175.

12.

Ushikoshi

Komatsu

Sugino

. Recycling of CFRP by pyrolysis method. J Soc Mater Sci Jpn 1995; 44(499): 428–431.

13.

Unser

Staley

Larsen

. Advanced composites recycling. SAMPE J 1996; 32(5): 52–57.

14.

Pickering

Kelly

Kennerley

. A fluidised-bed process for the recovery of glass fibres from scrap thermoset composites. Compos Sci Technol 2000; 60(4): 509–523.

15.

Candelieri T, Cornacchia G, Galvagno S, et al. Method and apparatus for recovering carbon and/or glass fibers from a composite material. Patent WO03089212, World, 2003; Patent EP1526956, Europe, 2005.

16.

Takahashi T and Nagase T. Method of recycling fiber-reinforced plastic. Patent 2010267868, USA, 2010; Patent WO2009072651, World, 2009; Patent EP2233517, Europe, 2010.

17.

Davidson J and Price R. Recycling carbon fibre. Patent WO2009090264, World, 2009; Patent 2010189629, USA, 2010; Patent EP2152487, Europe, 2011.

18.

Wan

Wang

. Influence of surface treatment of carbon fibers on interfacial adhesion strength and mechanical properties of PLA-based composites. J Appl Polym Sci 2001; 80(3): 367–376.

19.

Jang

Yang

. The effect of surface treatment on the performance improvement of carbon fiber/polybenzoxazine composites. J Mater Sci 2000; 35(9): 2297–2303.

20.

Zhang

Pei

. Effect of carbon fiber surface treatments on the flexural strength and tribological properties of short carbon fiber/polyimide composites. Surf Interface Anal 2008; 40(5): 961–965.

21.

Zhang

Breidt

. Comparison of short carbon fibre surface treatments on epoxy composites: I. Enhancement of the mechanical properties. Compos Sci Technol 2004; 64(13–14): 2021–2029.

22.

Weibull

. A statistical distribution function of wide applicability. J Appl Mech 1951; 27: 293–297.

23.

Hui

Phoenix

Shia

. The single-filament-composite test: a new statistical theory for estimating the interfacial shear strength and Weibull parameters for fiber strength. Compos Sci Technol 1997; 57(12): 1707–1725.

24.

Davidge

. Mechanical behavior of ceramics , Cambridge: Cambridge University Press, 1978.

25.

Zhao

Tomonaga

Takeda

. The estimation of statistical fiber strength by fragmentation tests of single-fiber composites. Compos Sci Technol 2000; 60(10): 1965–1974.

26.

Copponnex

. Analysis and evaluation of the single-fibre fragmentation test. Compos Sci Technol 1996; 56(8): 893–909.

27.

Varelidis

McCullough

Papaspyrides

. The Effect of temperature on the single-fiber fragmentation test with coated carbon fibers. Compos Sci Technol 1998; 58(9): 1487–1496.

28.

Lee

Drzal

. Surface characterization and adhesion of carbon fibers to epoxy and polycarbonate. Int J Adhes Adhes 2005; 25(5): 389–394.

29.

Ohsawa

Nakyama

Miwa

. Temperature dependence of critical fiber length for glass fiber-reinforced thermosetting resins. J Appl Polym Sci 1978; 22(11): 3203–3212.

30.

Feih SWK, Minzari D, Westermann P, et al. Testing procedure for the single fiber fragmentation test. Risø-R-1483(EN), 2004. Roskilde, Denmark: Risø National Laboratory.

31.

Santulli

. Critical length measurements in carbon fibers during single fiber fragmentation tests using acoustic emission. J Mater Sci 2004; 39: 2905–2907.

32.

Sarraf

Skarpova

Louda

. Surface modification of carbon fibers. J Achieve Mater Manuf Eng 2007; 25(2): 24–30.

33.

Montgomery

. Introduction to statistical quality control, 2nd ed. New York, NY: John Wiley and Sons, 1991.

34.

Krucinska

Zurek

Egbers

. The influence of fibre irregularity on the tensile properties of carbon and glass fibres. Compos Sci Technol 1995; 54(2): 169–175.