The effect of gamma radiation on the properties of polypropylene blends with styrene–butadiene–styrene copolymers

Radiation Processing of Styrene-isoprene-styrene/Poly(ε-caprolactone) Blends

The irradiation consequences on styrene-isoprene-styrene (SIS)/poly(ε-caprolactone) (PCL) blends are discussed starting from the oxidation initiation. Three characterization methods: chemiluminescence, differential scanning calorimetry and FTIR spectroscopy are applied. The differences that exist between the two components are revealed, when the oxidation rates of the inspected formulas depend on the blending proportion and the degradation conditions. The relevant activation energies characterizing the oxidation strength as well as the kinetic parameters of degradation during the accelerated damaging of blended polymers are related to the inhibition protection of PCL on the faster oxidation of SIS. The interaction between mixed components is revealed by the structural modifications simultaneously accompanied by the competition of formation and decay of radicals.

Conditions Optimization and Physiochemical Analysis of Oil Obtained by Catalytic Pyrolysis of Scrap Tube Rubber Using MgO as Catalyst

Motor vehicles scrap tires and tube rubbers generate a large amount of waste with different characteristics and compositions, contaminating the environment when not properly disposed. Waste inner tube rubber (isobutylene isoprene) representing a threat to the environment can be used as valuable source of energy. Waste inner tube rubber was pyrolyzed thermally under atmospheric pressure both with and without catalyst. Parameters of temperature, time, and catalyst weight were optimized for catalytic and thermal pyrolysis of isobutylene-isoprene rubber into liquid fuel, using MgO as catalyst. It was found that one-hour heating time at 350 °C using 2 g catalyst (MgO) constitutes a suitable parameter for the maximum conversion of scrap inner tube rubber into oil. The oil obtained was characterized by physical and chemical tests. Among the physical tests, Density, specific gravity, viscosity, kinematic viscosity, analine point and flash point were determined according to IP and ASTM standard valves. The physical tests indicate the presence of aromatic and olefinic hydrocarbons. Among the chemical tests, the phenol test, bromine number, bromine water test, and KMnO4 tests were conducted. The chemical tests are also the support of physical tests conducted. The physical and chemical tests indicate that the oil obtained is a mixture of kerosene, diesel, and light oil and could be used for fuel purposes.

Gamma irradiation influence on mechanical, thermal and conductivity properties of hybrid carbon nanotubes/montmorillonite nanocomposites

A thermoplastic elastomer (TPE) based nanocomposite with the same weight ratio of hybrid nanofillers composed of carbon nanotubes (CNTs) and montmorillonite nanoclay (DK4) was prepared using a melt blending technique with an internal mixer. The TPE composite was blended from polylactic acid (PLA), liquid natural rubber (LNR) as a compatibilizer and natural rubber (NR) in a volume ratio of 70:10:20, respectively. The weight ratio of CNTs and DK4 was 2.5 wt%. The prepared samples were exposed to gamma radiation at range of 0–250 kGy. After exposure to gamma radiation, the mechanical, thermo-mechanical, thermal and electrical conductivity properties of the composites were significantly higher than unirradiated TPE composites as the irradiation doses increased up to 150 kGy. Transmission electron microscopy (TEM) micrographs revealed the good distribution and interaction between the nano-fillers and the matrix in the prepared TPE hybrid nanocomposites. In summary, the findings from this work definite that gamma irradiation might be a viable treatment to improve the properties of TPE nanocomposite for electronic packaging applications.

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Carbon nanotubes/montmorillonite nanocomposite was prepared via a melt blending.

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Gamma irradiation improved the interaction and dispersion of nanofillers in matrix.

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At 150 kGy, the thermo-mechanical properties and conductivities improved.

The effects of rubber nanoparticles with different polarities on thermal properties and foaming performance of polypropylene blends

Polypropylene blends with both polybutadiene rubber (PB) and polycarboxylbuturonile rubber (xNBR) and the required amount of acrylamide (AM) was prepared by blending with water, and the crystallinity, rheological behaviour and thermal performance were analysed and compared. The results of DSC and XRD characterization showed an obvious enhancement in the crystallization of the PP matrix in PP/xNBR/AM blends compared to PP/PB/AM blends, due to the strong incompatibility between xNBR nanoparticles and the PP polymer matrix leading to the inhibition of segmental mobility and induced formation of heterogeneous nuclei. Rheological analysis showed that the dynamical mobility of polymer chains was retarded while the AM monomer was incorporated, due to strengthening interfacial interactions by grafts through hydrogen bonding. The foaming performance was clearly improved, as reflected in the uniform cell morphology and higher cell density, and the expansion ratio achieved was 13-fold. In addition, the decomposition temperature increased from 403 °C to 465 °C by nearly 62 °C as compared with neat PP, which is ascribed to the inhibition of segmental mobility due to the cyclization reaction of nitriles. The increase in the surface energy was about 2.2-fold, which resulted in a decrease of the water contact angle from 105.3° to 83.7°, attributed due to AM addition to the composition.

Polypropylene blends with both polybutadiene rubber and polycarboxylbuturonile rubber and the required amount of acrylamide was prepared by blending with water, improve the foaming and thermal properties of polypropylene.

Influence of gamma and electron beam sterilization on the stability of a premixed injectable calcium phosphate cement for trauma indications

Premixed calcium phosphate cements (CPC's) are becoming the material of choice for injectable cements as a result of their effective delivery to the target implantation site. For orthopaedic use, it is of vital importance that the attributes of these CPC's are not compromised by irradiation sterilization. Therefore, the aim of this study is to determine the influence of irradiation sterilization on a range of premixed CPC's, with an emphasis on improving product shelf life through the use of optimal packaging configurations and annealing steps. Electron spin resonance (ESR) confirmed the presence of free radicals in the inorganic phase of the CPC paste following irradiation. The inclusion of a 24-h annealing step was the only successful method in reducing the degree of free radical formation. Based on the results of injectability force testing, it was revealed that an annealing step greater than 24-h significantly altered the viscosity, however; at 24-h the key attributes of the CPC paste were minimally effected. Overall, it was established that vacuum packing the CPC paste, placing the contents into a foil pouch, gamma irradiating at the minimal dose required and using an annealing step of ≤ 24-h, has the potential to extend the shelf life of the cement.

Effects of temperature, packaging and electron beam irradiation processing conditions on the property behaviour of Poly (ether-block-amide) blends

The radiation stability of Poly (ether-block-amide) (PEBA) blended with a multifunctional phenolic antioxidant and a hindered amide light stabiliser was examined under various temperatures, packaging and electron beam processing conditions. FTIR revealed that there were slight alterations to the PEBA before irradiation; however, these became more pronounced following irradiation. The effect of varying the temperature, packaging and processing conditions on the resultant PEBA properties was apparent. For example, rheology demonstrated that the structural properties could be enhanced by manipulating the aforementioned criteria. Mechanical testing exhibited less radiation resistance when the PEBA samples were vacuum packed and exposed to irradiation. MFI and AFM confirmed that the melting strength and surface topography could be reduced/increased depending on the conditions employed. From this study it was concluded that virgin PEBA submerged in dry ice with non-vacuum packaging during the irradiation process, provided excellent radiation resistance (20.9% improvement) in contrast to the traditional method.

Effects of gamma ray and electron beam irradiation on the mechanical, thermal, structural and physicochemical properties of poly (ether-block-amide) thermoplastic elastomers

Both gamma ray and electron beam irradiation are widely used as a means of medical device sterilisation. However, it is known that the radiation produced by both processes can lead to undesirable changes within biomedical polymers. The main objective of this research was to conduct a comparative study on the two key radiosterilisation methods (gamma ray and electron beam) in order to identify the more detrimental process in terms of the mechanical, structural, chemical and thermal properties of a common biomedical grade polymer. Poly (ether-block-amide) (PEBA) was prepared by injection moulding ASTM testing specimens and these were exposed to an extensive range of irradiation doses (5-200 kGy) in an air atmosphere. The effect of varying the irradiation dose concentration on the resultant PEBA properties was apparent. For instance, the tensile strength, percentage elongation at break and shore D hardness can be increased/decreased by controlling the aforementioned criteria. In addition, it was observed that the stiffness of the material increased with incremental irradiation doses as anticipated. Melt flow index demonstrated a dramatic increase in the melting strength of the material indicating a sharp increase in molecular weight. Conversely, modulated differential scanning calorimetry established that there were no significant alterations to the thermal transitions. Noteworthy trends were observed for the dynamic frequency sweeps of the material, where the crosslink density increased according to an increase in electron beam irradiation dose. Trans-vinylene unsaturations and the carbonyl group concentration increased with an increment in irradiation dose for both processes when observed by FTIR. The relationship between the irradiation dose rate, mechanical properties and the subsequent surface properties of PEBA material is further elucidated throughout this paper. This study revealed that the gamma irradiation process produced more adverse effects in the PEBA material in contrast to the electron beam irradiation process.