Environmental and human health risks of plastic composites can be reduced by optimizing manufacturing conditions

Abstract

New plastic composites are being manufactured outdoors, inside buried water and sewer pipes. This cured-in-place-pipe (CIPP) practice has been less expensive than other infrastructure repair options, but pollutants discharged during and after plastic manufacture pose environmental and human health problems. The study goal was to better understand how composite manufacturing conditions could be altered to reduce the amount of pollution released. Initiator loading, curing time, and curing pressure were modified for CIPP styrene and non-styrene ("HAP and VOC free") resin based composites. The styrene resin contained 39 wt% volatile organic compounds (VOC) whereas the non-styrene resin contained 4 wt% VOCs. Both resins contained hazardous air pollutants (HAP), endocrine disruptor, and carcinogenic compounds not listed on their safety data sheets. Vacuum pressure prompted greater VOC loss from the resins compared to ambient pressure manufacture. During both pressure manufacturing conditions, less than 1 wt% VOC was released from non-styrene composites into air compared to 8.8 to 26.4 wt% VOC released from styrene composites. VOCs including acetophenone, dibutyl maleate, p,α-dimethylstyrene, ethylbenzene, isopropylbenzene, methacrylic acid, 2-phenyl-2-propanol, styrene, toluene, and m-xylene were present in the non-styrene composite after manufacture. By doubling the styrene composite's initiator loading, styrene and styrene oxide residuals were reduced by 42 and 33 wt%, respectively. Manufacturer recommended conditions for the non-styrene composite resulted in <1 wt% initiator usage. The life cycle environmental impact assessment, which considered only composite VOC residual, predicted that styrene dominantly influenced ecotoxicity and human carcinogenic levels. Modifications to CIPP resin composition and the curing process can reduce environmental and human health impacts.