Recycling of sheet‐molding compounds by chemical routes

Abstract

SYNOPSISThis article describes a number of chemical routes for the recycling of sheet-molding compounds (SMC) consisting of glass fibers, filler (calcium carbonate), and an unsaturated polyester-styrene thermoset resin. Treatment of milled SMC with ethanol/potassium hydroxide at 85°C for 48 h ultimately affords a soluble polymeric fraction, consisting of styrene-fumaric acid copolymers. The excess of potassium hydroxide as well as the filler are removed via a neutralization step, which results in a large stream of waste chemicals. Treatment of SMC chips with ethanolamine a t 180°C for 48 h gives a reaction mass that can be split into three fractions, viz., the glass fibers, the filler, and a methanol-soluble polymeric residue. The excess of ethanolamine is recovered by distillation at 220°C and reduced pressure. The polymeric fraction consists of terpolymers of styrene, N,N'-di(2-hydroxyethy1)fumaramide and N-2-hydroxyethylmaleimide monomer units, the latter two bearing two and one hydroxyl groups, respectively. The terpolymer shows little solubility in unsaturated polyester, epoxy, or isocyanate resins. The glass fibers and the filler coated with the polymeric fraction can be used as constituents of bulk-molding compounds (BMC).

Thermolysis of fibreglass polyester composite and reutilisation of the glass fibre residue to obtain a glass–ceramic material

“…(iii) Fluidised bed thermal processes to recover the carbon fibre reinforcement from composites [16][17][18][19]. c) Composite depolymerisation based on chemical processes such as hydrolysis, glycolysis and solvolysis to recover organic materials [20][21][22].…”

Current State of Recycling Sheet Molding Compounds and Related Materials

“…The products of the reaction were heated to 180 C for 4 h and then analyzed using Fourier transform infrared spectroscopy (FTIR). The spectra appeared almost identical to that of commercially available low-molecular weight maleic anhydride-styrene copolymers [14]. Using quantitative FTIR measurements, Winter et al determined that the copolymer consisted of 20% maleic anhydride and 80% styrene.…”

“…In order to perform neutral hydrolysis, water or ethanol and a catalytic amount of sodium hydroxide must be reacted with SMC at high temperatures (300-375 C) and under high pressures (10-100 bar), for 10-240 min. High-pressure, high-temperature conditions yielded low-molecular weight products from pyrolytic reactions according to Winter et al [14]. Low temperatures and the same pressures gave small amounts of extractable products similar to many of the solvolysis processes discussed later.…”

A tecnologia da reciclagem de polímeros

“…A quantidade de cloro não deve exceder 10 ppm para que estes compostos sejam utilizados nas plantas petroquímicas 120 . Portanto, é adicionado vapor de sódio no fluxo de gás de pirólise para minimizar a quantidade de halogênios no óleo obtido 121 .…”