Polystyrene thermal destruction

Boric acid esters provide for thermal stabilization of low-pressure polyethylene to a variable degree (Table 7). The difference in efficiency derives from the nature of polyester. Boric acid esters of aliphatic diols and triols are less efficient than the aromatic ones. Among polyesters of aromatic diols and triols, polyesters of boric acid and pyrocatechol exhibit the highest efficiency. Boric acid polyesters provide inhibition of polyethylene thermal destruction following the radical-chain mechanism, are unsuitable for inhibition of polystyrene depolymerization following the molecular pattern and have little effect as inhibitors of polypropylene thermal destruction following the hydrogen-transfer mechanism. 

Experimental and theoretical studies are presented from a laboratory-scale thermal destruction facility on the destructive behavior of surrogate plastic and nonplastic solid wastes. The nonplastic waste was cellulosic while the plastic waste contained compounds such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, nylon, rubber, and polyurethane or any of their desired mixtures. A series of combustion tests was performed with samples containing varying composition of plastic and nonplastic. Experimental results are presented on combustion parameters (CO, excess air, residence time) and toxic emissions (dioxin, furan, metals). 

THERMAL DESTRUCTION OF POLYPROPYLENE, POLYSTYRENE, POLYETHYLENE, AND POLYVINYL CHLORIDE... 

In the mid-1980s, the first technique that relies on the reversible termination of radicals with a stable free radical was developed in the group of E. Rizzardo at CSIRO in Australia. Rizzardo and co-workers found that nitroxide-stable free radicals were able to add to carbon-centered radicals to form alkoxy amines (9). In certain cases these alkoxy amines are thermally unstable, so that they enter into an equilibrium between (transient) carbon-centered radical and (persistent) nitroxide radical on one side, and alkoxy amine on the other side. TEMPO was initially the most frequently used nitroxide in conjunction with the polymerization of styrene and its derivatives. The TEMPO-polystyrene adduct requires temperatures of 120° C or above in order to establish an equilibrium at which polymerization takes place. Around the mid-1990s Georges and co-workers focused on the TEMPO-mediated pol5unerization of styrene (10), and developed various strategies to overcome intrinsic weaknesses of the system. They used camphor sulfonic acid to enhance the rate of polymerization (11). This rate enhancement was later elucidated to be due to the destruction of excess nitroxide that builds up during the polymerization. 

---