Specific oligomer recovery behavior from cured unsaturated polyester by superheated steam degradation

• Published in: Polymer degradation and stability 2019-03, Vol.161, p.1-6
• Main Authors: Chan, Chi Hoong, Wakisaka, Minato, Nishida, Haruo
• Format: Article
• Language: English
• Subjects: Chemical compounds; Collapse; Copolymers; Crosslinking; Cured unsaturated polyester; Degradation; Degradation behavior; Fourier transforms; Molecular weight; NMR; Nuclear magnetic resonance; Oligomer recovery; Polyester resins; Polyesters; Recovery; Size exclusion chromatography; Styrene-fumarate copolymer; Styrenes; Super-heated steam
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2018.12.025

To examine the specific oligomer recovery behavior from cured unsaturated polyester resin (cUPR), super-heated steam (SHS) was employed as a reactant. The cUPR was treated by SHS in a temperature range of 300–350 °C and solubilized, resulting in recovery of solvent extracted residues (SE-SDRs). From size-exclusion chromatography analysis, an interesting finding was that the molecular weight (MW) value of SE-SDR, increased gradually with degradation time. This specific recovery behavior was analyzed by FT-IR and 1H NMR spectroscopies. Based on the analytical results, a proposed SHS degradation mechanism was that first orthophthalate and glycol ester groups were degraded and removed as short length fragments, after which cleavage of styrene unit crosslinkers induced collapse of the 3-D network structure with the resulting solubilizing cUPR as SE-SDR. This mechanism can explain the specific oligomer recovery behavior whereby an increase in MW of SE-SDR occurred with SHS-degradation time. Obtained styrene-fumarate copolymer having Mn 2550 and Mw 9480 was recovered in a maximum 57 wt% yield after SHS treatment at 325 °C for 180 min. [Display omitted] •Cured unsaturated polyester resin (cUPR) was converted to styrene-fumarate copolymer (SFC) by super-heated steam (SHS) treatment, and SFC was recovered in the maximum 57 wt% yield after the treatment at 325 °C for 180 min.•Interestingly, the molecular weight of SFC increased gradually with SHS treatment time.•A degradation mechanism was proposed to explain the specific oligomer recovery behavior whereby an increase in MW of SFC occurred with SHS-degradation time.