Synthetic polymers degradation

An alternative tactic to deal with the problem of polymer wastes is to make polymers degradable. The difficulty with this approach is that in making synthetic polymers degradable one of the greatest assets of these materials, namely their durability, may be eliminated. There is also the possibility that... 

Pyrolysis GC/MS is limited in application to those studies in which the compounds formed are capable of being analysed by GC, that is it is only reasonably suitable for low molecular weight products. Many synthetic polymers degrade (pyrolyse) by processes that may simply be described as either random scission (e.g., polyolefins), unzipping to produce mostly monomers (e.g., PMMA)... 

Most synthetic and natural polymers degrade when exposed to solar ultraviolet (UV) radiation (1-5). In synthetic polymers degradation is generally caused by the presence of photosensitive impurities and/or abnormal structural moieties which are introduced during polymerization or in the fashioning of the finished products. The presence of groups such as ketones, aldehydes, peroxides and hydroperoxides are implicated in polymer degradation (1-5). 

TABLE 14.26 Msjor Synthetic Polymer Degradative Agents... 

Edman degradation (Section 27 13) Method for determining the N terminal amino acid of a peptide or protein It in volves treating the material with phenyl isothiocyanate (CgH5N=C=S) cleaving with acid and then identifying the phenylthiohydantoin (PTH derivative) produced Elastomer (Section 10 11) A synthetic polymer that possesses elasticity... 

Like almost all synthetic polymers, styrene plastics ate susceptible to degradation by heat, oxidation, uv radiation, high energy radiation, and shear, although... 

Whereas cellulose films are biodegradable, that is they are readily attacked by bacteria, films and packaging from synthetic polymers are normally attacked at a very low rate. This has led to methods of degrading polymers to a sufficiently low molecular mass (typically about 10000) which are then accessible to biodegradation. 

Membranes used for the pressure driven separation processes, microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO), as well as those used for dialysis, are most commonly made of polymeric materials. Initially most such membranes were cellulosic in nature. These ate now being replaced by polyamide, polysulphone, polycarbonate and several other advanced polymers. These synthetic polymers have improved chemical stability and better resistance to microbial degradation. Membranes have most commonly been produced by a form of phase inversion known as immersion precipitation.11 This process has four main steps ... 

Such studies have shown that it is the chemical structure and composition that determine whether or not synthetic polymers are biodegradable. On the other hand, the precise rate at which a synthetic polymer will degrade is determined by the specific morphology of the article into which the polymer has been fabricated. 

Synthetic polymers and natural polymers suitable for drilling muds are listed in Tables 1-7 and 1-8, respectively. Polyacrylamides are eventually hydrolyzed in the course of time and temperature. This leads to a lack of tolerance toward electrolyte contamination and to a rapid degradation inducing a loss of their properties. Modifications of polyacrylamide structures have been proposed to postpone their thermal stability to higher temperatures. Monomers such as AMPS or sulfonated styrene/maleic anhydride can be used to prevent acrylamide comonomer from hydrolysis [92]. 

Similarly to polymer synthesis, there are essentially two main mechanisms of degradation of synthetic polymers involving main chain links and leading to... 

A product is only considered to be totally biodegradable if all its single components can be degraded naturally. Currently, pressure sensitive adhesives (PSA) are mostly based on non-biodegradable synthetic polymers such as polyacrylates, ethylene-vinyl acetate copolymers and styrene block copolymers [124]. Therefore there is a growing demand for the application of biodegradable PSAs on naturally degradable products like paper and cardboard. 

---