1,721,046 research outputs found
The water ageing of unsaturated polyester-based composites: influence of resin chemical structure
No full textImmobilization of yeast cells in hydroxyethylmethacrylate gels
No full textWhole cells of Saccharomyces cerevisiae were entrapped in polymers of 2-hydroxyethylmethacrylate and sucrose hydrolysis catalysed by its invertase was investigated. Analysis of the experimental results confirmed that diffusional resistance to mass transfer of reactant and product was not induced by immobilization. For the yeast cells in the hydrogel, invertase activity obeyed Michaelis-Menten kinetic and the value of Km (40 mM) was the same as that for yeast cells in bulk phase. The recovery of biocatalyst activity ranged between 17% and 23%, depending on immobilization temperature; the optimum pH range was found to be slightly wider. Storage stability at refrigerator temperature was quite satisfactory; invertase half-life was 267 days. Operational stability of immobilized cells at 45°C (half-life 110 days) was almost twice that of free cells. Finally, cell distribution in the polymer, observed with a scanning electron microscope, was found to be uniform
THE DEVELOPMENT OF THERMAL-ENERGY STORAGE-SYSTEMS EXPLOITING SOLID-SOLID PHASE-TRANSITIONS
No full textThe selection criteria for various latent-heat storage systems are discussed. The evaluation of (n-CnH2n+1NH3)2MCl4 (M = Mn2+, Co2+, Hg2+, Fe2+, Cu2+, or Zn2+; n = 9-18), prepd. from com. available amines and incorporated in polystyrene [9003-53-6] matrixes, for heat storage systems is reported
Time, temperature and strain effects on viscoelastic Poisson's ratio of different polymeric materials
No full textAn investigation of non-elastic response of semicrystalline polymers at high strain levels
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WATER UPTAKE AND VOLUMETRIC CHANGES IN POLY(METHYLMETHACRYLATE).
No full textWater uptake in amorphous glassy, poly(methylmethacrylate) (PMMA) occurs through a dual mechanism, i. e. part of the penetrant is inserted into the polymer network and causes the swelling of the structure, and part is accommodated into pre-existing microvoids. In this communication we advance the suggestion that the equilibrium sorption isotherm of water in PMMA can be described by the dual sorption model, which can be applied in the gas sorption in glassy polymers. The theoretical expectations of density variation with the weight% of sorbed water agree well with experimental results from literature
PHYSICAL CHARACTERIZATION OF LAYERED PEROVSKITES-POLYSTYRENE COMPOSITES
No full textThe layered perovskites show a solid-solid transition at a temp. which is dependent on the no. of C atoms in the hydrocarbon chains and on the nature of the metal atom. The composite of polystyrene [9003-53-6] with (n-C12H25NH3)2MnCl4 [75899-75-1] shows relatively good mech. properties even at high filler content. These properties, coupled with excellent thermal properties due to the thermally active filler inside the polymer matrix, make the title composites potentially useful in thermal-energy storag
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