Adhesion-strong polymeric layers on polyethylene terephthalate films modified by irradiation with accelerated electrons

Regular trends in variation of the functional group composition, surface energy, and amorphous-crystalline structure of oriented polyethylene terephthalate films modified by irradiation with accelerated electrons to the absorbed dose in the range 25–300 kGy were studied by the methods of surface tension, indicator dye adsorption, and X-ray diffraction. The possibility of preparing gelatin emulsion layers exhibiting high adhesion strength was examined.     

Improvement of polyethylene by irradiation in artificial joints

The decrease in socket thickness of several total hip prostheses was measured on X-ray film. The following prostheses were compared: (1) SOM “28 mm metal head and an ultra-high-molecular-weight-polyethylene (UHMWPE) socket irradiated with 10⁸ rad of γ-radiation”, (2) T-28 “28 mm metal head and a UHMWPE socket not irradiated”, (3) Bioceram “28 mm alumina head and UHMWPE not irradiated” and (4) irradiated Bioceram “28 mm alumina head and UHMWPE socket irradiated with 10⁸ rad of γ-radiation”.The average steady state wear rate of SOM, T-28, Bioceram and irradiated Bioceram were 0.076, 0.247, 0.098 and 0.072 mm/year, respectively.The weight bearing portion of the irradiated socket presented a clearly-outlined and irregular pattern of about 0.1 μm thickness having a smooth ripple surface. The scratch and holding phenomenon characteristics of non-irradiated sockets was not observed at all.In our experimental tests using an IS sliding wear test machine, the wear measured as decrease of thickness was smallest at 10⁸ rad, although there was an increase in the coefficient of friction. Our experimental and clinical findings suggest that the best total hip prosthesis at present is one with an alumina head and a UHMWPE socket irradiated with 10⁸ rad of γ-radiation.     

Water soluble calixarenes as possible metal ion extractants in polyethylene glycol-based aqueous biphasic systems

The iodine thyroid content of 57 relatively healthy men and women 14–60 years old was studied using instrumental neutron activation analysis. Two methods were used: analysis of whole glands and the analysis of lyophilized samples weighing 50 mg each. Very good agreement between results was obtained. It was shown that the total iodine content, concentration and weight did not depend on age and sex. The typical mean thyroid parameters were found for healthy people of non-endemically goitrous regions where iodated food is not eaten. Average thyroid weight was 14.2g, iodine concentration was 350 g/g of wet weight and thus total iodine content was 5 mg.     

Crosslinking of recycled polyethylene by gamma and electron beam irradiation

Recycling of polymeric materials is usually accompanied by degradation and deleterious properties. Irradiation crosslinking of recycling low density polyethylene by electron beam and gamma rays could be the solution to improve their properties. This paper presents a comparison on the effects of gamma and electron irradiation on virgin and recycled polyethylene. Their mechanical, thermal and chemical properties were analyzed. VPE samples shown higher crosslinking percentages than RPE samples in all range of doses studied, unirradiated RPE samples had higher values on their tensile properties than VPE. Percentage crystallinity was similar in all range of doses studied.     

Improvement of the surface of polyethylene foamed sheet by irradiation

The manufacturing methods of cross-linked polyethylene foams are classified into two categories based on a type of cross-linking. One is chemical cross-linking by using peroxide as a cross-linking agent. The other method is cross-linking by irradiation. As for chemical cross-linking, a fairly thick foam sheet can be produced, and a comparatively high degree of cross-linking can be achieved. This means chemical cross-linking excels in thermo-forming but, due to a rough surface, the product is lacking in adhesive property and printability. We studied how to improve the surface condition of foam sheet without damaging the features proceeding from chemical cross-linking. As a result, it has been revealed that at the pre-stage of foaming, and by irradiating the surface at low voltage, the resultant foamed sheet with smooth surfaces and excelling in mechanical properties can be produced.     

Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. II. High-energy electrons irradiation

Vapor-phase mutual grafting of methyl acrylate (MA) onto polyethylene (PE) at high dose rates from an electron accelerator yields the same surface graft structure as does the grafting at low dose rates from ⁶⁰Co sources; i.e., a homopolymer layer (consisting of only MA component) is easily formed on the inner graft copolymer layer (consisting of both MA and PE components) as a result of the continuously increasing surface graft composition. To produce the surface layer, 4-MeV electron irradiation with a linear electron accelerator requires only less than 3 min of irradiation time at dose rates of more than 2 Mrad/min, whereas γ irradiation with a ⁶⁰Co source requires at least 1 hr at dose rates of less than 2 × 10³ rad/min. The rate of monomer consumption (or polymerization) in the surface homopolymer layer shows no dependence of irradiation time and a positive dependence of dose rate. It has been suggested that this kinetic feature at the high dose rates shows some contribution of vapor-phase homopolymerization and subsequent deposition (onto the grafting surface) followed by recombination with the grafted side chain radicals, although secondary graft copolymerization from the grafted chain radicals is still the principal process for the growth of the surface homopolymer layer.     

Penetrant diffusion in polyethylene spherulites assessed by a novel off-lattice Monte-Carlo technique

Semi-crystalline polymers have a complex hierarchical structure. The purpose of this study was to mimic the real structure of polyethylene spherulites by computer simulation using an off-lattice method in order to predict their diffusion properties. The principles used to build the spherulites were based on established findings obtained by electron microscopy. Spherulites in the crystallinity range of 0-55 vol% were built. Diffusion of small-molecule penetrants assuming no interfacial trapping at the amorphous-crystal boundary was studied using a Monte-Carlo technique. The main findings were: (i) diffusion was isotropic; (ii) diffusion was independent of the aspect ratio of the crystal building bricks, clearly in disagreement with the Fricke model; (iii) the geometrical impedance factor showed a dependence on the average free path length of the penetrant molecules in the amorphous phase; and (iv) data for the geometrical impedance factor obtained by simulation compared favourably with experimental data obtained for several penetrants showing limited interfacial trapping.     

Li ion diffusion in LiAlO2 investigated by Raman spectroscopy

The temperature dependence of Li ions behavior of γ-LiAlO₂ has been studied from 78 to 873 K. On heating, the Li ions underwent positional disordering along the structural channels, with the Li ions related modes at 220, 366 and 400 cm⁻¹ broadening and weakening dramatically. An anomalous maximum in the bandwidths of the Li ions related modes is observed. It should be apparent that there are at least two distinct thermally activated processes. A model suggested by Andrade and Porto is used to describe the linewidth of a phonon.     

Decomposition of solid amorphous hydrogen peroxide by ion irradiation

We present laboratory studies of the radiolysis of pure (97%) solid H2O2 films by 50 keV H+ at 17 K. Using UV-visible and infrared reflectance spectroscopies, a quartz-crystal microbalance, and a mass spectrometer, we measured the absolute concentrations of the H2O, O2, H2O2, and O3 products as a function of irradiation fluence. Ozone was identified by both UV and infrared spectroscopies and O2 from its forbidden transition in the infrared at 1550 cm(-1). From the measurements we derive radiation yields, which we find to be particularly high for the decomposition of hydrogen peroxide; this can be explained by the occurrence of a chemical chain reaction.     

Chain diffusion in semicrystalline polyethylene: Dielectric relaxation

The experimental data on high-temperature dielectric relaxation αcin linear PE samples with different thermal prehistories (slow cooling, quenching, and annealing) are described. The measurements are conducted at temperatures ranging from 0 to 80°C. Dielectric losses are measured with a high accuracy at frequencies varying from 10^?2 to 10–10⁶ Hz. These dielectric measurements allow one to reveal changes in the frequency dependence of losses with temperature. This effect of the thermal prehistory of the sample and applied stress is explained within the framework of the molecular model of chain diffusion between crystalline and amorphous phases in PE.     

Compaction of microporous amorphous solid water by ion irradiation

We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40 K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation. We find that the decrease in internal surface area of the pores, signaled by infrared absorption by dangling bonds, precedes the decrease in the pore volume during irradiation. Our results imply that impacts from cosmic rays can cause compaction in the icy mantles of the interstellar grains, which can explain the absence of dangling bond features in the infrared spectrum of molecular clouds.     

Compatibilisation of polyethylene/ground tyre rubber blends by γ irradiation

In the present work, γ irradiation is used for the in situ compatibilisation of blends of recycled high density polyethylene (rHDPE) and ground tyre rubber (GTR) powder. The expected compatibilisation mechanism involves the formation of free radicals, leading to chain scission within rubber particles, crosslinking of polyethylene matrix and co-crosslinking between the two blend components at the interface. While uncompatibilised rHDPE/GTR blends show poor mechanical properties, especially for elongation at break and Charpy impact strength, irradiation leads to a significant increase of these mechanical performances. Such behaviour is attributed to the development of an adhesion between GTR particles and the surrounding thermoplastic matrix. This conclusion is supported by in situ scanning electron microscopy observations during microtensile tests, showing strong elongation of GTR particles upon deformation of irradiated blends.     

Constructing carbon nanotube junctions by Ar ion beam irradiation

Carbon nanotubes (CNTs) irradiated by Ar ion beams at elevated temperature were studied. The irradiation-induced defects in CNTs are greatly reduced by elevated temperature. Moreover, the two types of CNT junctions, the crossing junction and the parallel junction, were formed. And the CNT networks may be fabricated by the two types of CNT junctions. The formation process and the corresponding mechanism of CNT networks are discussed.     

Behaviour of chlorosulfonated polyethylene under gamma irradiation

The behaviour of chlorosulfonated polyethylene on gamma irradiation was investigated over the range of total absorbed dose of 5 to 550 kGy. The structural modifications were followed by infrared spectroscopy and some main kinetic characteristics of the process were assessed. Determinations of gel content and evaluation of changes in sulphur and chlorine content were correlated with the evolved amounts of hydrochloric acid and with changes in unsaturation of polymers.     

Surface characteristics of low-density polyethylene films modified by oxyfluorination-assisted graft polymerization

In this study, a unique two-step process, i.e., an oxyfluorination-assisted graft polymerization (OAGP), was used to modify the surface properties of low-density polyethylene (LDPE) films. Based on the results of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method, which was performed to estimate the amount of hydroperoxides generated by oxyfluorination, oxyfluorination conditions that maximize the amount of hydroperoxide groups were selected. Hydroperoxides were generated by oxyfluorination to provide active sites for the OAGP of the different monomers. Depending on the type of monomers used, two different graft polymerization behaviors were observed. Hydrophilic methacrylic acid (MA) monomers were graft polymerized onto the oxyfluorinated LDPE (OFPE) surface in a perpendicular direction, forming a spike-shaped morphology. On the other hand, hydrophobic styrene (ST) monomers were graft polymerized parallel to the OFPE surface, forming a valley-shaped morphology. By changing the type of vinyl monomers, two different surfaces could be prepared using the hydroperoxides generated by oxyfluorination. After OAGP with MA monomers, a hydrophilic surface following the Wenzel model was obtained, whereas after OAGP with ST monomers, a hydrophobic surface following the Cassie–Baxter model was obtained. Therefore, the OAGP process may be an efficient method for preparing two different surfaces by changing the monomer used.     

NMR study of diffusion of butane in linear polyethylene

The diffusion coefficient of butane in linear polyethylene at room temperature as a function of the vapor pressure of butane was measured by the spin-echo method with a pulsed magnetic field gradient. For the Special morphology of randomly oriented stacks of parallel lamellas the detour factor is 1/3. As long as the blocking factor and migration through the lamellas can be neglected, the local diffusion coefficient D_a of the small molecules through the amorphous layers in the direction parallel to the lamellas is three times the apparent diffusion coefficient D derived from the decay of the amplitude of the spin echo under the assumption of an infinitely extended homogeneous medium. The diffusion coefficient and the spin–spin relaxation time both increase exponentially with increasing pressure, i.e., butane concentration in the polymer, while the spin-lattice relaxation time is pressure independent and seems to be determined by interaction with the amorphous polyethylene matrix.