A laboratory reactor was designed and constructed to study the effect of both speed of agitation and a concentration of suspension stabilizer on particle size and particle size distribution during the suspension polymerization of methyl methacrylate. It was concluded that the average particle size of the prepared polymer powder is directly proportional to the speed of agitation and is inversely proportional to the stabilizer concentration. New empirical equations correlating the average particle size and the particle size distribution (PSD) were derived from the study.
C ORE SHELL technique was used to synthesize conductive Cu-core / Ag-subshell / polyaniline-shell nanocomposites (NCs) and evaluating their antimicrobial activities. This was achieved through two stages, firstly different Cu/Ag core shell nanoparticles (Cu/Ag NPs) were prepared (C/A1, C/A3, C/A5), using electroless plating technique by reduction of AgNO 3 in alcoholic dispersion of Cu NPs at three different weight ratios of AgNO 3 : Cu. Secondly, the prepared Cu/Ag NPs were further coated with polyaniline (PANI) by oxidative polymerization of aniline in their aqueous dispersions to form PANI/(Cu/Ag) NCs (NC1, NC3, NC5). XRD patterns of Cu/Ag NPs revealed their bimetallic crystalline structure. SEM micrographs and EDAX data proved formation of Ag thin shell on the surface of Cu core. The concentration of this silvery layer increased from ≈ 38% (C/A1) to 68% (C/A5). SEM and EDAX data of NCs, showed that PANI film wrapped 60% to 63% of Cu/Ag NPs surface that Cu nearly diminished. The synthesized NCs possessed good electrical conductivity that increased with Ag content from 0.52 S/m (NC1) to13 (NC5) S/m. Good antimicrobial activities (antibacterial and antifungal), of Cu/Ag NPs and their NCs were obtained. Such good conductivity and antimicrobial activity nominate the NCs to be applied in electronic and biotechnical fields.
SynopsisThe effect of four different types and concentrations of plasticizers on some physical properties of poly(viny1 chloride) (PVC) has been studied. DOP, DOA, TTP, and Hex were used as plasticizers in concentrition levels of up to 24% of PVC weight. The plasticized and unplasticized PVC were processed into sheets by compression molding. The sheets were tested for their vicat softening point, shore D hardness, flexural properties, and dynamic fatigue. It was found that the vicat softening point, shore D hardness, flexural yield strength, and flexural modulus decrease with increase in plasticizer concentration, though in some cases a threshold concentration must be passed befoFe these effects can be okrved. Close similarities were always found in the behavior of DOP and DOA and also between TTP and Hex. It was found in the study of flexural fatigue properties of PVC plasticized by DOP that an increase in plasticizer concentration led to a decrease in load bearing ability only at stress levels above 20 MPa.
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