Carbon Dots as smoke suppression agents for the reduction of CO release in combustion and improvement of UV resistance towards Phosphorus-containing polyester

2-Carboxyethyl(phenyl) phosphinic acid (CEPPA) is an effective phosphorus-containing flame retardant for PET. However, the release of poisonous and harmful smoke increases when CEPPA is added to PET matrix (CEPPA-PET) during the combustion process. To address this, biomass gelatin-based Carbon Dots (gCDs) was adopted as nontoxic green smoke suppression agent. When the gCDs was copolymerized into CEPPA-PET matrix by in situ polymerization (CEPPA-gCDs-PET), the peak smoke production rate was reduced by 59.38% and the CO yield was decreased by 13.83%. It was found the limited oxygen index of CEPPA-gCDs-PET rose to 31% from 21% and could achieve a V-0 rating in the UL-94 test when the content of gCDs and CEPPA were only 1.0 wt% and 5.0 wt%, respectively. What is more, in comparison with neat PET, the peak heat release rate significantly decreased by 42.66% and the total heat release was reduced by 48.10%, the peak smoke production rate is also reduced by 59.38%. Besides, the tensile strength of CEPPA-gCDs-PET increased by 11.93% for CEPPA-PET. At the same time, the addition of gCDs was beneficial for the improvement of UV resistance for CEPPA-PET, and the transmittance of sleeves prepared from the fiber of CEPPA-gCDs-PET is less than 5% from 240 nm to 400 nm. Thus, a higher efficiency flame retardant, mechanical enhancement and UV resistance system was constructed with only 5 wt% CEPPA and 1 wt% gCDs toward CEPPA-PET copolymer.