Irradiation dose rate

The chain length is therefore adversely afFected by the irradiation dose rate being inversely proportional to its square root. Wagner (1969) lists a large class of unsaturated compounds in which addition reactions can be induced by irradiation. Typical examples involving long chain lengths are for the addends HC1, Cl2, and HBr in ethylene, benzene, toluene, and so on. where the products are telomers or hexachlorides. 

LDPE/EVA blend was irradiated using gamma-irradiation and then expanded by heat as a foamed material. The EVA content in the blend was optimised to form a gel. The effects of atmospheres and of irradiation dose rate were studied. The ETIR spectra of the foam revealed the oxidation level. The relations between gel fraction of LDPE/EVA blend, expansion ratio, apparent density, average cell diameter and tensile properties of the foam are discussed. 8 refs. 

A new additive dose method is proposed to obtain the age directly without extrapolating the growth curve.1115 The experimental growth curve at the artificial irradiation dose rate gives simply the defect production efficiency (G-value) from the initial growth and the interaction distance, d, between spins from the saturation behaviour. The latter involves the effect of magnetic dipolar and exchange interactions of similar and dissimilar spins and also destabilization of a spin in a distorted area by a local lattice distortion. 

Usually, when the high energy electrons travel through the aqueous media, they leave behind these reactive species in spheres centered on the point of impact where the electrons strike the molecules suspended in the media. As the irradiation dose rate increases, the concentration of these spheres of reactive species increases, we observe a concentrated ionization path, as those observed with protons and neutrons. 

The e-beam pulse frequency is related to the energy absorbed by the material per unit of time, i.e. to the irradiation dose rate therefore it can affect both the cure reaction kinetics and the heat developed during cure. 

It is possible to control the exothermic reaction within the wood by varying the irradiation dose rate (i.e., the distance between the 7 source and the wooden object). 

In the case of TC, both stages of the process are thermally activated. In the case of RTC, the first stage is radiation initiated chain carriers are created by irradiation. The absorbed electron energy, necessary for formation of radical concentration sufficient for cracking initiation is only about 0.4 kJ/mol. The propagation stage of RTC is still thermally activated. The radical mechanism of RTC assumes that radiation-induced chain initiation does not depend on temperature, and the rate of radical generation depends only on irradiation dose rate. 

Dependence of the product G-values on temperature and irradiation dose rate is given by the following equation ... 

Kq is reaction rate constant Kr is recombination rate constant P is irradiation dose rate... 

Table 6.Fraction of St-nBA homopolymer and grafted in NR film. Irradiation dose rate = 0.4 Mrad/hour, monomer concentration 40 phr... 

T.J. Williams, P.R. Burch, C.A. English and P.H.N. de la cour Ray, The effect of irradiation dose rate and temperature, and copper and nickel content, on the irradiation shift of low alloy steel submerged arc welds, Proceedings of the Third International Symposium on Environmental Degradation of Materials - Water Reactors, G.J Theus and IR. Weeks (eds), The Metallurgical Society, Warrendale, PA, 1988, pp. 121-131. 

As the irradiation causes the chain scission, with simultaneous creation of chain termination, induced by polymer/stabilizer radical reactions, a significant modification of the molecular weight [M (5 Mrad)/M (0 Mrad) = 0.5] may be observed. Consequently a decrease of the molten viscosity for irradiated PP with increasing irradiation dose rate is observed [6]. 

Table 6 Influence of temperature on the grafting of polypropylene fibers with acrylonitrile monomer (y Co-irradiation dose rate 0.5 kGy.h ). The data were taken from [98P1].

Table 13 Changes in water uptake for various swelling time at different doses obtained during swelling of NVP/AAm copolymer hydrogel (80/20 v/v) y ( Co)-irradiation dose rate 5.15 kGy.h The data were taken from [04H2].

Table 14 The effect of different pH on the drug release from poly(W-vinyl-2-pyrrolidone)/itaconic acid/ gelatin (97 3 15 mg). The data were taken from [09E1]. (drug chloropromazine hydrochloride 30 kGy of 7 ( °Co)-irradiation dose rate 1.3 Gy.s ). ...

Fig. 18 Modifications in the oxygen uptake (a) and rate of oxygen uptake (b) EPDM/DVB films at various doses. DVB concentration 18 phr. blends (7 ( Cs) irradiation dose rate 0.45 kGy.h ). The data were taken from [05Z1]. ( ) 0 kGy, (0) 7.0 kGy, (O) 25.2 kGy and ( ) 70.1 kGy.

Fig. 23 Ratios of crosslinking to scission radiochemical yields for (a) neat LDPE (b) LDPE + TMPTA + diazodicarbonamide (c) LDPE + TMPTMA + diazodicarbonamide (7 ( Co)-irradiation dose rate 5.1 kGyJi ). The data were taken from [OlBl] (white) virgin polyethylene (black) recycled polyethylene.

Fig. 26 Changes in unsaturation level for irradiated isobutylene-isoprene rubber rubber [01Z2]. ( ) accelerated electrons (energy 2 MeV) (O) 7 ( Cs)-irradiation (dose rate 0.4 kGy.h ).

Fig. 44 Radiochemical yields measures for irradiated FEP at various temperatures (7 ( Co)-irradiation dose rate ...

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