Current State of Recycling Sheet Molding Compounds and Related Materials

Abstract

Recycling of thermoset molding compounds has been intermittently investigated for roughly the past 15 years. The use of sheet molding and bulk molding compounds has steadily increased over the same time period, but no closedloop recycling regime has been developed. First, a general discussion is made on the materials involved and some of their applications. The major recycling methodologies, energy recovery, chemical breakdown, thermal breakdown, and size reduction are all reviewed. Also, some of the new technologies being developed and areas where further work is needed are outlined.

Re-use assessment of thermoset composite wastes as aggregate and filler replacement for concrete-polymer composite materials: A case study regarding GFRP pultrusion wastes

“…Filler or reinforcement material for artificial wood (Demura et al, 1995), high density polyethylene plastic lumber (George and Dillman, 2000), wood particle board (Conroy et al, 2006), rubber pavements blocks (Itoh and Kaneko, 2002), cement based concrete materials (Asokan et al, 2009(Asokan et al, , 2010Correia et al, 2011;Kojima and Furukawa, 1995;Osmani and Pappu, 2010;Tittarelli and Moriconi, 2010;Wakasuhi and Sugiura, 1995;Yamada k Mihashi, 1995), bulk and sheet moulding compounds (DeRosa et al, 2005a(DeRosa et al, , 2005bJutte and Graham, 1991) and core material for textile sandwich structures (Adolphs and Branca, 2001), were some of the foreseen potential applications for the recyclates. Most of them have failed at an industrial scale due to one or both of the following reasons: (a) tendency of recyclate addition to negatively affect the mechanical properties of final composite; and (b) negative cost balance, where recycling and refining operation costs outweighed the market value of the virgin products (calcium carbonate and glass fibres); (Halliwell, 2006;Palmer et al, 2009;Pickering, 2006).…”

Recycling carbon fibre reinforced polymers for structural applications: Technology review and market outlook

“…Some review papers on carbon-fibre recycling are available in the literature; DeRosa et al (2005) and Pickering (2006) focused on established recycling processes, while McConnel (2010) and Wood (2010) discussed their implementation at commercial scales. However, there is a strong connection between recycling, re-manufacturing processes and the final performance of the recyclates (Pimenta et al 2010a); this clearly affects the type of markets in which rCFs can be introduced, which has a great impact for any commercial recycling operation (Line 2009).…”

A Critical Review of Research on Reuse of Mechanically Recycled FRP Production and End-of-Life Waste for Construction

“…Experimental investigations are required to confirm this hypothesis as it seems to contradict some findings about incorporating FRP waste particles in polymeric materials; according to DeRosa et al [48], Dzeskiewicz and Ralston [56] found that when 17.5 wt% BMC recyclate with an average size of 0.25 mm was added to another BMC, tensile strength increased slightly over the base formulation, while when 0.50 mm recyclate was added at 17.5 wt%, a 15% reduction in tensile strength in the new BMC was observed. However, it is not known if the particles of waste BMC used by Dzeskiewicz and Ralston were in the form of composite or separated ingredients.…”

“…Some studies have shown that using ground FRP as a filler in new polymeric composite materials can reduce mechanical performance of the new composite [47], while other studies have reported similar or even enhanced properties of polymeric composite materials as a result of incorporating mechanically recycled FRP waste. For example, it has been observed that substitution of up to 88% of the calcium carbonate filler in sheet molding compounds (SMCs) by fine particulate recycled FRP resulted in materials with comparable strength and stiffness [48]. Inoh et al [49] reported that replacing up to 20% of filler in SMC with finely ground SMC does not affect the mechanical performance of the composite material.…”