VOCs emissions from recycled PET are recognized as one of the major causes of poor healthy condition. Much attention has been increasingly focused on VOCs produced from regenerated PET for their significance in ecological safety. These emissions may be strongly influenced by the raw materials and manufacturing techniques of the recycled PET. However, there is very little published information regarding this issue. The purpose of this study was to examine VOCs releasing from reprocessed productions when exposed to high temperature or other extreme conditions.In this study, we determined and compared VOCs emissions from samples after different manufacturing stages such as PET popcorn, dried PET popcorn, screw melts, undrawed fibers and drawed fibers, including their species and content. To simulate the VOC emissions of samples processed with the high temperature in longer time during screw melting, we investigated VOCs from screw melts utilizing Thermo Gravimetric-Mass Spectrometry (TG-MS) with 90 min in 280°C . We found that: (1) The optimisation of the equilibration procedure for volatile organic compounds was performed and the optimal equilibration conditions were determined to be 30 min at 120°C ; (2) Seven individual VOCs were identified: considerable VOC content changes during the manufacturing process; and the drying was tremendously helpful in reducing the VOC emissions from PET popcorn; formaldehyde, acetaldehyde and TVOC were reduced by 24%, 58% and 50%, respectively after drying; while acetaldehyde, benzene, benzaldehyde and TVOC increased dramatically after screw melting; (3) The VOCs were released at the initial stage of heat preservation (about 5 min) and VOCs content came to the maximum which indicated the almost immediate thermal degradation in screw melting.

A method to determine the volatile organic compounds (VOCs) in the recycled polyethylene terephthalate fiber was presented by using the headspace sampling-gas chromatography coupled to flame ionization detector (HS-GC-FID), in order to evaluate the level of VOC contamination. The extraction variables, such as the incubation temperature, the pre-incubation time and the size of the vial, were also studied. The effects on the determination of VOC were also compared using two type chromatographic columns. The optimal conditions were found using a headspace sampling for 20 min at 100 °C, where 120 mL vials and TM-1 column were prior to analysis of benzene compounds in PET(polyethylene terephthalate) fibers. The results can be used in analysis of VOC from recycled PET fibers.

As consumer awareness of heavy metal content in textile increased, it is necessary to develop analytical methods that identify and quantify heavy metals. In order to comprehensively investigate the potential risks of antimony (Sb) in recycled polyester fiber to humans health, this study developed acid digestion method, with the condition that the volume ratio of concentrated sulfuric acid to hydrogen peroxide was 1, and digested at 200°Cfor 1.5h, which produced clear and colorless solutions.Currently, microwave and dry ashing are also common methods for digesting polyethylene terephthalate samples. Three pretreatment methods for determining the content of Sb in recycled polyester fibers was evaluated. Results showed that inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis of acid digested recycled polyester samples resulted in Sb content higher than for the microwave and dry ashing digestion methods which incompletely digest recycled polyester. Moreover, compared with microwave digestion and dry ashing, acid digestion had a low detection limit of 0.0116 ug/mL, a high spike recovery of 82% to 106% and the RSD value less than 2%, which indicates that the data was accurate and reproducible. Therefore, in this study, acid digestion - ICP-OES was an effective method for detecting the content of heavy metal Sb in recycled polyester.

Recycling is promising to dispose the wasted Poly (ethylene terephthalate) (PET) fibers currently. However, high temperature and oxygen in the recycling process may accelerate the degradation of PET and residual dyes, resulting in the volatile organic compounds (VOCs) emissions, which will do serious harm to the environment and human health. Exploring the source of VOCs is significant to remove VOCs and keep products safety. This study was carried out to investigate the influence of high temperature on the release of four VOCs (formaldehyde (CH2O), acetaldehyde (C2H4O), benzene (C6H6) and toluene (C7H8)) during the recycling process of PET fibers, utilizing thermogravimetric analysis and differential thermal analysis coupled with mass spectrometric (TGA-DTA/MS). The atmospheres and heating conditions of esterification, polycondensation and melt spinning were simulated by TGA with various atmospheres and programmed heating processes (heating from 50 °C to 240 °C in Ar, 280 °C in Ar and 280 °C in air, respectively, and then maintaining for 30min). Bis (2-hydroxyethyl) terephthalate (BHET) (esterification product) and virgin PET (VPET) were used to explore the thermal degradation of PET. White PET popcorn, black PET popcorn and dyes were used to explore the effect of dyes on the release of VOCs. The results indicated that: (1) Aldehydes including formaldehyde and acetaldehyde are generated during the manufacturing process of PET, mainly due to its thermal oxidation;(2) Aromatic compounds including benzene and toluene are originated from the disperse dyes. So the degree of dye removing has a great influence on the production safety; (3) Thermal oxidation causes more VOCs than nonoxidative thermal degradation. So in the stages of melt spinning and slightly alcoholysis, usually in O2 containing atmosphere, devolatilization should be developed further.