[en] Positron lifetime measurements for some selected vinyl polymers have been performed. Samples have been made of : polyvinyl chloride, polyvinyl alcohol, polymethyl methacrylate, polystyrene and polyvinyl acetate. A conventional slow-fast coincidence lifetime spectrometer with plastic scintillators have been used for lifetime measurements. Mean free volumes radii have been calculated from the positron lifetime data. (author). 12 refs, 1 tab

[en] Published in summary form only

[en] Preparation of two-layer hydrogel composed of polyvinyl alcohol (PVA), kappa carrageenan (KC) and carboxy methyl chitosan (CMS) laminated on polyvinyl pyrrolidone (PVP) and KC was conducted by gamma irradiation for the purpose of using as hydrogel wound dresser. The top part which designed to put to contact with the wounds would be soft hydrogel with anti-microbial activity from PVA and CMS respectively. The bottom part would serve asmain body of hydrogel, harder and absorb more wound exudate. KC was used for both layers as it could hold up more quantity of other polymers than that of agar and pregel was formed easily. The results showed that a proper constituent of the top part composed of 8% PVA 2.6% KC and 0.4% CMS. At radiation dose of 24 kGy, gel content was 9.4% with gel strength of 145 g/cm² and 250% swelling. The bottom part hydrogel composed of 7% PVP and 3% KC. At radiation dose of 24 kGy, gel content was 36.7% with gel strength of 588 g/cm² and 476% swelling. The prepared hydrogels were thus soft. possessed the power to kill germ and hold up more wound exudate

[en] A heavy charged particle detector is proposed which, to increase the registration threshold, is fitted with a sensitive polyvinylidenfluoride element. To ensure the required discriminatory power of the detector, the polyvinylidenfluoride is co-polymerized with tetrafluorideethylene which may amount up to 70 mol.%. The detector can be used for the threshold registration of accelerated multiply charged ions

[en] In this paper, we demonstrate knife edge techniques for measuring the focused beam profile of the photothermal imaging system. This quick and simple method of profiling the focused beam from Helium-Neon (He-Ne) laser is presented and detected by the PVDF thin film as a sensor. The study of focused beam profile is crucial so as to provide information of the focused beam such as beam resolution, depth of focus and the level of astigmatism of the beam. In knife edge technique, the blade moves across the beam in x and y-direction at varying axial position. (paper)

[en] The solubility parameter is calculated to express the magnitude and nature of the interactive forces between the polymers and solvents. It measures the affinity between the components of a mixture. To improve the prediction of the solubility parameter, the group contribution method is used to calculate the overall solubility parameter as suggested by Handlebar. Hildebrand’s method is used to predict the interaction between the polymers and solvent. In this study, calculate the solubility parameters of polysulfone (PSU), polyvinyl acetate (PVAc) polymers and dimethylacetamide (DMAc) solvent by Hildebrand method. The PSU and PVAc solubility were found to be 1.52H and 1.7H, respectively. These solubility values show that both polymers were dissolved readily in the DMAc solvent, resulting in a true solution. (author)

[en] In this paper, the effect of wheat straw (WS) pretreatments and glue formulations on mechanical (i.e. Compressive Strength (CS) and Impact Strength (IS)) and water resistance properties (i.e. Thickness Swelling (TS) and water absorption (WA)) of particle board have been investigated and the results have been compared with conventional wooden particleboard. Wheat straw was treated with steam available at 110 degree C and 20 psig, for the retention time of 5, 10 and 15 min. The solution of 10% HCl was also used for removing the lignin. Particleboard was prepared by bonding treated WS with four types of glue recipes of synthetic and natural binders like urea formaldehyde (UF), polyvinyl acetate (PVA), corn flour (CF) and wheat flour (WF). The particle board was formed at the hydraulic pressure and temperature of 2800 psig and 80 degree C respectively. It was observed that WS particleboard has low mechanical strength and high water resistance in comparison with conventional board. The particle board prepared with HCl cured wheat straw and glue having high urea formaldehyde and corn flour has higher CS and IS as well as low TS and WA. It may be concluded that wheat straw is a good substitute of wood for particle board while using HCl as a modifying chemical and strong binders like urea formaldehyde and corn flour. (author)

No abstract available

[en] Thermo-oxidative stability of poly (vinyl acetate) has been examined by measurement of loss in weight on heating in air. Weighted amounts of poly (vinyl acetate) placed in silica crucible were heated at four temperatures i.e. 125, 150, 175 and 200 deg. C for five hours in a ventilated furnace to an average atmosphere and weight losses were determined at various time intervals. These data were plotted as (a) percent volatilization in 5 hours versus temperature (b) as rate of volatilization versus percent volatilized. It has been found that above 125 deg. C the reaction proceeds rapidly, reaches a maxima then falls Activation energy based on rate of evaporation is found to be 12.98 Kcal/Mole. Further, work is in progress to enhance the thermal stability of poly (vinyl acetate). (author)

No abstract available