Photodegradable polyolefins. Photo-oxidation mechanisms of innovative polyolefin copolymers containing double bonds (original) (raw)
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Photo-oxidation of polymers—Part V: A new chain scission mechanism in polyolefins
Polymer Degradation and Stability, 1982
The photo-oxidation o fan ethylene-propylene copolymer has been studied at 310 and 365 nm. The results indicate that the Norrish type II reaction occurs but that another chain scission mechanism is also operative. This involves the reaction of free radicals produced by the photo-decomposition of hydroperoxide groups with neighbouring ketones.
Polymer Degradation and Stability, 1980
The effect of prior irradiation (2's > 30Ohm) in an inert atmosphere on the subsequent photo-oxidative stabilities of polypropylene and low density polyethylene films has been examined using luminescence, infra-red and ultraviolet absorption techniques. Prior prolonged irradiation in an inert atmosphere of nitrogen was found to have no significant effect on the subsequent rates of photo-oxidation of the polymer films. The importance of oxygen-polymer charge transfer complexes in initiating photo-oxidation of the polymers is discussed in relation to the behaviour of other major photo-initiators such as carbonyl/'unsaturated carbonyl and hydroperoxide groups.
Journal of Applied Polymer Science, 1998
Acrylate and methacrylate monomers with the photodimerizable ␣,-unsaturated ketone moiety, such as 4-cinnamoylphenyl, 4-(4-methoxycinnamoyl)phenyl, 4-(4-nitrocinnamoyl)phenyl, or 4-(4-chlorocinnamoyl)phenyl, were prepared and homopolymerized using benzoyl peroxide as the initiator at 70°C in methyl ethyl ketone. The poly(meth)acrylates were characterized by ultraviolet, infrared, 1 H-nuclear magnetic resonance (NMR), and 13 C-NMR spectra, and gel permeation chromatography. Their thermal properties were studied by thermogravimetric analyses in air and nitrogen, and differential scanning calorimetry. The photocrosslinking properties of the polymers were investigated as thin films and in solution in the presence and absence of sensitizer.
Synthesis of photoreactive poly(ether ether ketone)s containing alkyl groups
Journal of Polymer Science Part A: Polymer Chemistry, 1996
Poly(ether ether ketone)s containing alkyl groups were prepared by nucleophilic substitution reaction of alkyl-substituted difluoro diaryl ethers with hydroquinone or by electrophilic substitution reaction of alkyl-substituted diaryl ether with 4,4'-oxydibenzoic acid in PPMA. Polycondensations proceeded smoothly and produced polymers having inherent viscosities up to 0.5-1.6 dL/g. The polymers were quite soluble in strong acid, dipolar aprotic solvents, and chloroform a t room temperature. Thermogravimetry of the polymers showed excellent thermal stability, indicating that 10% weight loses of the polymers were observed in the range above 450°C in nitrogen atmosphere. The glass transition temperatures of the polymers ranged from 128 to 146°C. Furthermore, Polymer 3b functioned as a photosensitive resist of negative type for UV radiation. The resist had a sensitivity of 42 mJ/cm2 and a contrast of 2.5, when it was postbaked at 100°C for 10 min, followed by development with THF/acetone a t room temperature.
Journal of Macromolecular Science, Part A, 2005
The copolymers of ethylene/propylene as well as their terpolymers with polar monomers were prepared by Ni-catalyst systems and their photodegradation behavior was studied by Fourier transform infrared spectroscopy. The polar monomers used to synthesize coand terpolymers of ethylene/propylene/polar monomer were 5-hexen-1-ol, 10-undecen-1-ol, acrylamide, methylmethacrylate, acrylonitrile, and methylvinyl ketone. The morphological changes of the irradiated samples were determined by scanning electron microscopy. The photodegradation kinetics has also been studied. The surface damage caused by polychromatic irradiation (l 290 nm) at 55 8C in atmospheric air is presented in different micrographs. The rate of photo-oxidative degradation is very fast in terpolymers containing polar monomers as compared with copolymers and homopolymers. The morphological study of the photodegraded samples showed a very good correlation with the photodegraded results.
Photo-oxidative degradation of mechanically stressed polyolefins
The influence of mechanical tensile stress on the photodegradation of commercial drawn polyolefin tapes has been investigated. The degradation was monitored by the time-to-break in creep experiments. Surprisingly, photodegradation had little effect on creep rates of polyethylene and only a small effect on creep rates of polyethylene-propylene copolymer (~10% ethylene content). The stress was shown to accelerate photodegradation.
Photochemically cross-linked poly(ε-caprolactone) with accelerated hydrolytic degradation
European Polymer Journal, 2015
Irradiation of benzophenone (BP)-doped poly(e-caprolactone) (PCL) films at k > 350 nm alters the molecular characteristics, viscoelastic properties and hydrolytic degradation rate. The influence of BP concentration on changes caused by irradiation of BP-doped PCL film was investigated using gel permeation chromatography along with analyses of gel content, DSC and rheology. Changes in the rate of basic hydrolysis of irradiated BP-doped PCL films were also investigated. Irradiation of PCL film doped with at least 0.5% w/w BP led to crosslinking and gel formation, even though simultaneous degradation was also observed. Polar groups formed during the irradiation of BP-doped PCL films enhanced the hydrolysis of cross-linked PCL films compared with untreated films.
Macromolecular Chemistry and Physics, 1994
In this work the reexamination of the photo-oxidation mechanism of three poly(ethy1eneco-propene-co-5-ethylidene-2-norbornene) (EPDM) terpolymers containing different amounts of 5-ethylidene-2-norbornene (ENB) a) (2-8 wt.-%) is discussed. The photo-oxidation depends on the initial content of ENB units in the chains. The formation of a band at 923 cm-' is attributed to the CH out-of-plane deformation of a new double bond in terminal position in the ethylidene moieties. The presence of double bond migration suggests the formation of stable tertiary hydroperoxides which show a new band at 870 cm-'. The kinetic behaviour of a band with similar spectral pattern in the UV at 235 nm has been correlated with double bond migration. The identification of photoproducts both by 2,4-dinitrophenylhydrazin and SO, confirms the proposed spectroscopic assignments. The gel measurements of the studied terpolymers, and some comparisons with a poly(ethy1ene-co-propene) (EPR) copolymer having a similar ethylene to propene ratio, suggest that the presence of ENB can strongly influence both the photo-oxidation and the crosslinking yields of these rubbers.
Polyolefins with controlled environmental degradability
Antioxidants and stabilisers, developed to increase the durability of polyolefins, in combination with prooxidant transition metal complexes provide industrial products with widely variable but controlled lifetimes. The low molar mass oxidation products formed during photo-oxidation and thermal oxidation are biodegradable and oxo-biodegradable polyolefins are now widely used in agricultural applications and in degradable packaging as examples. The scientific basis for the performance of oxo-biodegradable materials is explained with reference to naturally occurring macromolecules. Comparison with hydro-biodegradable materials is made and the need is demonstrated for performance standards to be developed that mimic nature's resource recovery mechanism, that of oxo-biodegradation.