E. Calderaro

Physical and structural characterization of blends made with polyamide 6 and gamma-irradiated polyethylenes

Abstract Morphological, calorimetric and rheological results of blends made with polyamide 6 and polyethylene gamma irradiated in air are presented. The polar oxidized groups grafted in the poliolefin chains through gamma-radiation induce “compatibilization” effects in the blends with a more uniform and finer distribution of the polyethylene “phase” in the polyamide matrix, with respect to blends made with the unirradiated polymer. This effect, observed with polyethylenes of different molecular structure, i.e. low density, linear low density and high density, was attributed to the presence of interactions among the functional oxidized groups of the polyethylene chains and the polyamide. Tests done at different mixing times indicate that short times are enough to allow these interaction to occur.

Tensile properties of γ-irradiated LDPE-iPP blends

Abstract Low density polyethylene-isolatic polypropylene have been irradiated in vacuum in the dose range 0–150 Mrad. The structural modifications induced by irradiation were the subject of a previous work. Tensile tests have been performed on the same materials and the results are here discussed in the light of their physico-chemical properties.

Physico-chemical properties of γ-irradiated LDPE-iPP blends

Abstract Low density polyethylene-isotactic polypropylene blends have been irradiated in the dose range 0–150 Mrad. Structural modifications have been investigated by means of solubility, calorimetric and density measurements. Slight interactions between the effect of irradiation and the effect of blending have been observed for the blends containing small amounts of one component.

γ-radiation effects on a polycarbonate

Abstract The γ-radiation effects on a commercial poly-carbonate have been observed through rheological measurements, performed both on solutions and on the bulk polymer, and through dynamic-mechanical tests. All the data show that while at small doses a crosslinking effect predominates at higher doses the main chain scission is more effective.

Structural induced modifications in blends of polyamide with gamma irradiated low density polyethylene

Abstract Blends of gamma irradiated and unirradiated low density polyethylene and polyamide 6 were made in order to study possible modifications induced by this irradiation. Results indicate that blends with gamma irradiated polyethylene have structure and properties significantly different with respect to blends made with the unirradiated one. This difference has been ascribed to the formation of functionalized groups in the polyethylene chains, which interact with polyamide.

Radiation pretreatments of cellulose materials for the enhancement of enzymatic hydrolysis—II. Wood chips, paper, grain straw, hay, kapok

Abstract The effect of γ-ray pre-irradiation of cellulose materials such as wood chips, paper, grain straw, hay and kapok on glucose production on enzymatic hydrolysis by cellulase has been investigated. These materials have been irradiated in air, water and acetate buffer solution over the dose range 10 3 –4 x 10 6 Gy. In the relatively low dose range, up to about 5 x 10 5 Gy, the glucose yields after enzymatic hydrolysis are practically insensitive to radiation. At higher dose levels, up to 1.7–2 x 10 6 Gy, the pre-irradiation becomes very effective on enzymatic cellulose conversion. It has been found that the radiation-induced degradation of cellulose into low molecular weight polysaccharides is dependent on the nature and chemical composition of the cellulose materials and on the radiation environmental conditions. Further increases of dose causes radiation-induced structural modifications in polysaccharides previously produced, which can lead to a decrease in glucose production by enzymatic hydrolysis.

Effect of radiation conditions on some properties of a polycarbonate

Abstract Samples of polycarbonate subjected to γ-radiation under different conditions have been characterized by means of intrinsic viscosity, solubility and dynamic-mechanical measurements. All the data indicate that the effect of the dose absorbed by the material increases markedly with the water content in the polymer during the irradiation. In absence of water, up to 20 Mrad, the material seems essentially insensitive to the irradiation. In the presence of water crosslinking predominates at small doses while at higher doses main chain scission is more effective.

Molecular modifications and crystallization relationships for gamma-irradiated LLDPE/PA6 blends

Abstract The effects of gamma-radiation under vacuum on linear low density polyethylene/polymide-6 blends are studied and the results are compared with the effects of the same ageing treatment on the pure polymers. In particular, solubility and melt viscosity tests were performed and data are related to the crystallization behaviour of this system. The results indicate that molecular modifications of the blends can be interpreted by considering both the effect of gamma radiation on the two polymers and the presence of some interactions between the components due to radiation processing and mixing. For the thermal behaviour, the effects of irradiation on the maximum temperature rate and enthalpy of crystallization are observed and, in general, these are more marked for the minor component at high dose.

Ageing due to gamma-radiation of a crosslinked polyethylene

Abstract Ageing due to gamma radiation in air of a low density polyethylene, previously crosslinked by gamma-radiation under vacuum, is studied. The aim is to try to separate crosslinking and degradation phenomena which usually occur during irradiation in air. The effect of irradiation is investigated by means of solubility and swelling and calorimetric measurements, and stress-strain tensile tests. Gamma-radiation in air of the crosslinked polymer causes mainly oxidative degradation, the extent of which depends on irradiation dose rate.

Ageing of organic electrical insulating materials due to radiation: Physical properties of a cycloaliphatic epoxy resin irradiated under vacuum

Abstract Physical properties of a cycloaliphatic epoxy resin irradiated under vacuum have been investigated. In particular dynamic-mechanical, dielectric and tensile measurements have been performed. This is a useful basis with a view to studying the ageing phenomenon of organic insulating materials due to radiation under the combined effect of environmental conditions. The results indicate that, in the dose range investigated (0-1.5 x 10 6 Gy), the main effect of γ-rays under vacuum is to increase the degree of crosslinking