Study on properties of PB-g-PS latex-modified cement mortars
The PB-g-PS latex was used to modify cement mortar, and the weight ratios of polybutadiene to styrene ranged from 70/30, 50/50 to 30/70. In the constant water-cement ratio of 0.5, and curing 24h at 20°C, RH90% air followed by 27d at 20°Cwater. This study examines the effects of weight ratios polybutadiene to styrene and the polymer-cement ratios on the flow, compressive and flexural strength and water absorption rate of PB-g-PS latex modified cement mortar. The experimental results show that the flow of modified mortar is increased with increasing polymer-cement ratios and decreasing weight ratios of polybutadiene to styrene, PB-g-PS latex can markedly reduce capillary water absorption rate. The minimum is 1.33Kg/m2. PB-g-PS latex can marked influences much on the mechanical properties of modified mortars. The compressive of the polymer modified mortar decreased, and the flexural strength of polymer modified mortar decreased as well. Overview on, PB-g-PS latex can be incorporated into cement mortars as cement modifier.
Properties of latex blends and its modified cement mortars
Abstract In this paper, the mechanical properties of three latex blends and the mechanical properties and chloride diffusivity of the latex-modified mortars are studied. The relationships between the properties of polymer films formed from latex blends and the properties of the latex blend-modified mortars are illustrated. The test results showed that the modified mortar with the blend of styrene–acrylic ester (SAE) and styrene–butadiene rubber (SBR) showed synergistic effect; especially the flexural strength of the SAE/SBR blend-modified mortars was about 20–40% higher than that of monolatex-modified mortars. However, the vinyl chloride–vinylidene chloride copolymer (PVDC)/SBR and PVDC/SAE blends-modified mortars showed antisynergistic effect. The compressive strength of the modified mortars increased with the increasing of the tensile strength of the latex films, while the flexural strength of the modified mortars did not depend on the tensile strength of the latex films. When PVDC with the mass fraction of 0.2 or SAE copolymer emulsion with mass fraction of 0.4 was blended into SBR latex, the latex blend-modified mortars showed lower chloride diffusivity. The chloride diffusivity of the modified mortars increased approximately linear with the tensile strength of the latex blend films, and decreased with increase of the elongation at rupture of the latex blend films. When the elongation at rupture of the latex blend films increased from 200–300% to more than 800%, the chloride diffusivity of the modified mortars decreased from 10–15×10 −12 to 3–4×10 −12 m 2 /s.
Reduction of patient exposure during dental radiography.
We investigated the effect of using additional accessories with a conventional X-ray machine to reduce patient exposure during full-mouth dental radiography. LiF extruded-rod thermoluminescent dosimeters were placed in 23 anatomical sities of a Randophantom and the phantom was exposed to a Turkish dental X-ray machine operated at 60 kV, 10 mA for 0.5 sec periods. Maximum reductions were observed at the eyes (80%), in the thyroid (70.6%). under the collar bone (59.9% average) and the gonads