Compositions of Volatile Organic Compounds Emitted from Melted Virgin and Waste Plastic Pellets

Abstract

To characterize potential air pollution issues related to recycling facilities of waste plastics, volatile organic compounds (VOCs) emitted from melted virgin and waste plastics pellets were analyzed. In this study, laboratory experiments were performed to melt virgin and waste plastic pellets under various temperatures (150, 200, and 250 degrees C) and atmospheres (air and nitrogen [N2]). In the study presented here, low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS) and the recycled waste plastic pellets were used. The VOCs generated from each plastic pellets were collected by Tenax/Carboxen adsorbent tubes and analyzed by thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS). The result showed the higher temperatures generated larger amounts of total VOCs (TVOCs). The VOCs emitted from the virgin plastic pellets likely originated from polymer degradation. Smaller TVOC emissions were observed in N2 atmosphere than in air atmosphere. In particular, larger amounts of the oxygenated compounds, which are generally hazardous and malodorous, were detected in air than in N2. In addition to the compounds originating from polymer degradation, the compounds originating from the plastic additives were also detected from LDPE and PS. Furthermore, various species of VOCs likely originating from contaminant inseparate polyvinyl chloride (PVC), food residues, cleaning agents, degreasers, and so on were detected from the waste plastic. Thus, melting waste plastics, as is conducted in recycling facilities, might generate larger amounts of potentially toxic compounds than producing virgin plastics.

Controlling Odorous Fumes Produced by Melting Recycled Polypropylene

“…Yamashita et al (2009) showed that hot-melt virgin lowdensity PE emits various quantities of aldehydes, ketones, organic acids, and other organic compounds. All the emitted volatile organic compounds (VOCs) are harmful to the plant's workers and the neighboring inhabitants and the associated odor may raise public complaints.…”

Elimination of Odors Emitted from Hot-Melting of Recycle PS by Oxidative-Reductive Scrubbing

“…Yamashita et al (2009) showed that hot-melt virgin PS emits aromatic hydrocarbons and aldehydes as main organic compounds as shown in Table 1. All the emitted volatile organic compounds (VOCs) shown in Table 1 are harmful to the plant's workers and the neighboring inhabitants and the associated odor may raise public complaints.…”

“…A few studies focused on the hypochlorite oxidation of aqueous organics such as benzene, toluene, xylenes, phenolates, aldehydes, and ketones. (Yamashita et al, 2009 Aliphatic hydrocarbons 320 2 32 220 Aromatic hydrocarbons 0 200 1 10 Alcohols 0 10 2 20 Aldehydes 0 20 18 240 Ketones 0 15 13 80 Esters 0 2 2 70 Organic acids 15 9 9 170 Others 0 2 39 140 Total 335 260 116 950 Fig. 1.…”

Identifying thermal breakdown products of thermoplastics

“…However, little is known of the degradation products released under real thermal processing conditions and in the presence of air, which can lead to the formation of oxygenated decomposition byproducts such as aldehydes, ketones or alcohols (10) . Besides, K. Yamashita et al have observed that during polymer degradation, smaller amounts of VOCs were emitted under nitrogen atmosphere than under air atmosphere (11) .…”