Polymers solvolysis

The solvolytic processes hydrolysis, alcoholysis, glycolysis, and aminolysis are suitable for recycling of products of polycondensation and polyaddition [13]. Since these are balanced-reaction processes, the primary material can be broken down into its monomers at a high temperature and with appropriate additives. A differentiation is drawn between summative and selective solvolytic processes. These processes are applied to polyesters, st5renics, and pol3mrethanes on a large scale as of today, and other (selective) polymers solvolysis solutions are under development. 

Important solvolysis reactions for nylons are hydrolysis, methanolysis, glycolysis, aminolysis, ammonolysis, transamidation, and acidolysis.17 Hydrolysis of nylon-6 with steam in the presence of an acid catalyst to form caprolactam is tlie preferred depolymerization approach. However, when recycling carpet face fibers, file fillers in the polymer may react with file acid catalyst and lower the efficiency of the catalyst. 

Polymers with hetero-atoms in the chain are suitable for chemical recycling of waste materials. In addition to depolymerisation (nylon 6) and solvolysis (nylon 6,6, PETP, PU) the degradation of aliphatic polyamides with dicarboxylic acids, diamines and cyclic anhydrides, especially trimellitic anhydride, becomes more and more important. The utilisation of the obtained fragments is described. 

This article highlights the growing problem of plastics waste disposal and then investigates modes of polymer degradation - thermal, chemical, mechanical, photodegradation, bio-degradation, solvolysis andglycerolysis. 4 refs. 

Another reaction mechanism that occurs in some chain-growth polymers is solvolysis. In this type of reaction, a species reacts with a C-X bond, where X represents a halogen, and breaks it. Specifically, this becomes important when describing the degradation of polyvinyl chloride. Acidic species act to remove the chlorine atom, forming hydrochloric acid. 

The chemical nature of the main-chain linkages of step-growth polymers makes this class of polymers particularly reactive to a wide variety of chemical species. Solvolysis reactions break the C-X bond at the polymer linkage bonds. These types of reactions are often pH-dependent, so the stability of the polymer is highly dependent on the acidity or basicity of the prodegradant. 

In the present study, PU s containing lignin were investigated with reference to thermal stability, which is one of the basic thermal properties of polymers. Thermal degradation of PU s which were obtained from solvolysis lignin was studied using thermogravimetry (TG). The inflammability of... 

A practical means of assessing the stability of the formed bond has been suggested by Sircar and Voet22), who, for various carbon blacks and elastomers, plotted the unextractable amount of rubber from the filler as a function of the temperature of extraction for a variety or solvents. They observed the experimental points related to a given polymer-filler blend to be falling linearly, and the extrapolation to zerografting ratio provided the so-called solvolysis temperature Tm, which appears to be independent of the solvent used. Tm represents the temperature theoretically required to eliminate all bonds between carbon blacks and elastomer and is, therefore,... 

The equations indicate that solvolysis is also possible. However, in most cases the reactions give only small yields. Many side reactions, cleavage of the Si-Si bond, rearrangements, and condensation reactions to polymers take place. 

Conversely, dimethylaminopyridines attached to polymers are remarkably effective catalysts of the solvolysis of esters, with true turnover [28-30],... 

Fife and co-workers described a macromolecule, 5 containing 4-DAAP and a bis-(trimethylene) disiloxane backbone that exhibited enzyme-like substrate selectivity for the esterolysis of p-mtrophenyl alkanoates, 6 (Scheme 5.2). This synthetic polymer showed highest levels of activity toward substrate 6 (n = 14), when it was used as a nucleophilic catalyst for the solvolysis of a series of... 

The importance of the anionic imidazole qiet is more apparent pdy-benzimidazole 2 (pK = 3.5, pKgj = 12.2) is emplt ed as catalyst (50). The value for polyvinylbenzimidazole-catalyzed solvtdy of PNPA 5 increased with increasing pH and was about four times greater than that for benzimidazcde-cata-lyzed solvolysis over the pH range of 4 to 10. i,n the polymer-catalyzed scdvol-ysis of NABS increased dmilarly with increa ng pH, whereas that for benziiiiid-... 

A similar conchisimi was arrived at when positively dragged polymer catdysts were employed for a n atively charged substrate (87). Hie solvolysis of NABA 6... 

Overberger and Pacansky used polymer catalysts 42 of dmilar nature for the solvolysis of neutral and anionic phenyl esters in aqueous buffer media contming 20 to 60% ethanol (88). The reaction fdlowed the xmd-oider kinetics and the catalytic efficfency toward anionic substrates was generally inferkir to diat of pdy-vinylinudazole. The absence of substrate binding may be attributed to die use of ethanol-water as the reaction media and to low substrate concentrations. 

A. Krzan Microwave irradiation as an energy source in poly(ethylene terephthalate) solvolysis. Journal of Applied Polymer Science, 69, 1115-1118 (1998). 

---