Exposure to ultraviolet (UV) radiation may cause the significant degradation of many materials. UV radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. Polystyrene (PS), one of the most important material in the modern plastic industry, has been used all over the world, due to its excellent physical properties and low-cost. When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement. The mechanism of PS photolysis in the solid state (film) depends on the mobility of free radicals in the polymer matrix and their bimolecular recombination. Free hydrogen radicals diffuse very easily through the polymer matrix and combine in pairs or abstract hydrogen atoms from polymer molecule. Phenyl radical has limited mobility. They may abstract hydrogen from the near surrounding or combine with a polymer radical or with hydrogen radicals. Almost all synthetic polymers require stabilization against adverse environmental effects. It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (1) light screeners, (2) UV absorbers, (3) excited-state quenchers, (4) peroxide decomposers, and (5) free radical scavengers; of these, it is generally believed that excited-state quenchers, peroxide decomposers, and free radical scavengers are the most effective. Research into degradation and ageing of polymers is extremely intensive and new materials are being synthesized with a pre-programmed lifetime. New stabilizers are becoming commercially available although their modes of action are sometimes not thoroughly elucidated. They target the many possible ways of polymer degradation: thermolysis, thermooxidation, photolysis, photooxidation, radiolysis etc. With the goal to increase lifetime of a particular polymeric material, two aspects of degradation are of particular importance: Storage conditions, and Addition of appropriate stabilizers. A profound knowledge of degradation mechanisms is needed to achieve the goal.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-398) contains supplementary material, which is available to authorized users.

The depletion of the world's crude oil reserve, increasing crude oil prices, and issues related to conservation have brought about renewed interest in the use of bio-based materials. Emphasis on the development of renewable, biodegradable, and environmentally friendly industrial fluids, such as lubricants, has resulted in the widespread use of natural oils and fats for non-edible purposes. In this study, we have reviewed the available literature and recently published data related to bio-based raw materials and the chemical modifications of raw materials. Additionally, we have analyzed the impacts and benefits of the use of bio-based raw materials as functional fluids or biolubricants. The term biolubricants applies to all lubricants, which are both rapidly biodegradable and non-toxic to humans and other living organisms, especially in aquatic environments. Biodegradability provides an indication of the persistence of the substance in the environment and is the yardstick for assessing the ecofriendliness of substances. Scientists are discovering economical and safe ways to improve the properties of biolubricants, such as increasing their poor oxidative stability and decreasing high pour points. ''Green'' biolubricants must be used for all applications where there is an environmental risk.

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BackgroundPetroleum polymers contribute to non-degradable waste materials and it would therefore be desirable to produce ecofriendly degradable materials. Biodegradation of polyhydroxybutyrate (PHB) in the presence of oligomer hydrolase and PHB depolymerase gave 3-hydroxybutyric acid which could be oxidized to acetyl acetate. Several bacteria and fungi can degrade PHB in the soil.ResultsBiodegradation of PHB showed a significant decrease in the molecular weight (Mw), number-average molecular weight (Mn) and the dispersity (Mw/Mn) for all the film formulations. Nanofibers of PHB and its composites showed faster degradation compared to other films and displayed complete degradation after 3 weeks. The SEM micrographs showed various surface morphology changes including alterations in appearance of pores, cavity, grooves, incisions, slots and pointers. Such changes were due to the growth of microorganisms that secreted PHB depolymerase enzyme which lead to the biopolymer films degradation. However, PHB nanofibers and its composites films in the presence of TiO2 demonstrated more surface changes with rupture of most nanofibers in which there was a drop in fibres diameter.ConclusionsThe degradation of biopolymers help to overcome some of the pollution problems associated with the use of petroleum polymers. PHB nanofiber and its TiO2 composite were degraded faster compared to other PHB film types due to their three dimensional and high surface area structures. The presence of TiO2 nanoparticles in the composite films slowdown the degradation process compared to PHB films. Additionally, the PHB and its composite films that were prepared from UV treated PHB films led to acceleration of the degradation.Graphical abstractBiodegradation of polyhydroxybutyrate films in soil

Five new thiophenes, namely,N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a),N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b),N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-methylquinazolin-4(3H)-one (4d), and 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-isopropylquinazolin-4(3H)-one (4e), have been synthesized. All of these materials brought about a reduction in the level of photodegradation of poly(vinyl chloride) (PVC) films containing the synthesized thiophenes (0.5%; by weight). The results obtained showed that the extent of photostabilization of PVC in the presence of an additive was in the order4e > 4d > 4b > 4a > 4c. For the most favorable additive (4e), the rate of appearance of infrared absorption bands of degradation products was reduced by around two-thirds, while the quantum yield of chain scission was calculated to be reduced by a factor of more than one thousand. It is suggested that the additives may help stabilize PVC by direct absorption of UV radiation and dissipation of the energy as heat or that electrostatic attraction between the additives and PVC may assist transfer of energy from excited state PVC to the additive, from where it can be dissipated.

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Three organotin complexes containing furosemide as a ligand (L), Ph 3 SnL, Me 2 SnL 2 and Bu 2 SnL 2 , were synthesized and characterized. Octahedral geometry was proposed for the Me 2 SnL 2 and Bu 2 SnL 2 , while the Ph 3 SnL complex has trigonal bipyramid geometry. The synthesized organotin complexes (0.5% by weight) were used as additives to improve the photostability of poly(vinyl chloride), PVC, (40 µm thickness) upon irradiation. The changes imposed on functional groups, weight loss and viscosity average molecular weight of PVC films were monitored. The experimental results show that the rate of photodegradation was reduced in the presence of the organotin additives. The quantum yield of the chain scission was found to be low (9.8 × 10 −7 ) when Ph 3 SnL was used as a PVC photostabilizer compared to controlled PVC (5.18 × 10 −6 ). In addition, the atomic force microscope images for the PVC films containing Ph 3 SnL 2 after irradiation shows a smooth surface compared to the controlled films. The rate of PVC photostabilization was found to be highest for Ph 3 SnL followed by Bu 2 SnL 2 and Me 2 SnL 2 . It has been suggested that the organotin complexes could act as hydrogen chloride scavengers, ultraviolet absorbers, peroxide decomposers and/or radical scavengers.