Search Results
Abstract
Characterization of dilute solution of gamma-irradiated polymethyl methacrylate (PMMA) in acetone has been carried out. The polymer sample in form of natural beads was administered a gamma-ray dose of 30 kGy by a cobalt-60 radiationsource. Various types of viscosities, viscosity average molecular weight, shape and size of irradiated PMMA and its two fractions were calculated. The results were compared with those for unirradiated PMMA. Degradation of PMMA as a result of irradiation has been observed.
Abstract
The influence of methyl metharcylate and gamma exposure dose on the physico-chemical and mechanical properties of polymer-alite composite have been investigated. The hardened alite samples were impregnated with a methyl methacrylate monomer and then subjected to γ irradiation doses from 10–50 KGy. The effect of polymer loading (%), compressive strength, bulk density and the microstructure (scanning electron microscopy SEM), in addition IR spectra were studied. The results indicate that, polymer loading, compressive strength and bulk density increase with increasing absorbed dose. This is attributed to the deposition of the polymer in the pores of the samples. SEM showed the voids between the particles in the samples before the impregnation, whereas, the formation of new products in the pores appeared after impregnation.
Abstract
The influences of nanosized CaCO3 on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated. Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA/CaCO3 and PS/CaCO3 were prepared with different filler loading (0–4 wt%) of CaCO3 nanoparticles by solution mixing technique. The Fourier transform infrared analysis confirmed that CaCO3 nanoparticles were present in the polymers matrices. The morphology and elemental composition of nanocomposites were evaluated by SEM and energy dispersive X-ray spectroscopy. The thermal properties of nanocomposites were characterized by differential scanning calorimetric, thermogravimetric, and differential thermogravimetry analysis, and the results indicate that the incorporation of CaCO3 nanoparticles could significantly improve the thermal properties of PMMA/CaCO3 and PS/CaCO3 nanocomposites. The glass transition temperature (T g ) and decomposition temperature (T d ) of nanocomposites with 4 wt% of CaCO3 nanoparticles were increased by 30 and 24 K in case of PMMA/CaCO3 and 32 and 15 K in the case of PS/CaCO3 nanocomposites, respectively. The obtained transparent nanocomposites films were characterized using UV–Vis spectrophotometer which shows the transparencies of nanocomposites are almost maintained in visible region while the intensity of absorption band in ultraviolet (UV) region is increased with CaCO3 nanoparticles contents and these composites particles could enhance the UV-shielding properties of polymers.
calculated at the heating rate value of 20 K min −1 with oil shale. Interactions between polymers and fossil fuels are not well known. In this study, degradation behavior of polyethylene (PE), polyethylene glycol (PEG), polymethyl methacrylate (PMMA
-reinforced plastics (GRP), vinyl panel, polymethyl methacrylate (PMMA), polyurethane (PU) and two types of expanded polystyrene (EPS) foam. All material samples were treated according to the guided procedure of cone test with a surface area of 100 × 100 mm, and were
Abstract
Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO2, H2O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented.
Bone cements are widely used for the fixation of metallic prostheses in orthopaedics and to form replacements for skull defects in neurosurgery. Acrylic bone cements are based on a mixture of methyl methacrylate (MMA) and a fine powder of polymethyl methacrylate (PMMA). The polymerization of the bone cement occurs in contact with the bone and the prosthesis which act as the boundaries of a bulk polymerization reactor. The kinetic behaviour of the bone cement plays a fundamental role for the final performance of the implant.
Abstract
This biomaterials overview for selecting polymers for medical devices focuses on polymer materials, properties and performance. An improved understanding of thermoplastics and thermoset properties is accomplished by thermal analysis for device applications. The medical applications and requirements as well as the oxidative and mechanical stability of currently used polymers in devices are discussed. The tools used to aid the ranking of the thermoplastics and thermosets are differential scanning calorimetry (DSC), thermogravimetry (TG), thermal mechanical analysis (TMA) and dynamic mechanical analysis (DMA) as well as a number of key ASTM polymer tests. This paper will spotlight the thermal and mechanical characterization of the bio-compatible polymers e.g., olefins, nylon, polyacetals, polyvinyl chloride and polyesters.
Abstract
Two sets of hardened cement pastes were prepared by (a) impregnation with polymethyl methacrylate and polystyrene or (b) admixing with water-soluble condensates(superplasticizers) such as Na-phenol sulphonate formaldehyde, Na-polystyrene sulphonateand Na-β-naphthol sulphonate formaldehyde. The pastes were hydrated for 180 days. The results of nitrogen adsorption indicated that polymer impregnation strongly affected the specific surface areas and the total pore volumes of the hardened cement pastes. XRD analysis, DTA and TG demonstrated (a) the formation of new phases as a result of the interactions involving the polymer within the pore system of the hydrated products of the impregnated cement pastes, and (b) no change in the phase composition of the hydrated products of the cement pastes admixed with superplasticizers.
Abstract
Three types of porous limestone from Sóskút quarry and two limestone types obtained directly from Matthias Church of Budapest (both in Hungary) were used to test the performance of five stone consolidants. The quarry specimens were treated under laboratory conditions by saturation. Three types of silicic acid ester, an aliphatic uretan resin and a polymethyl methacrylate were applied to the stone. Physical parameters such as density, porosity, ultrasonic sound velocity and Duroscope rebound value were measured on untreated and treated samples. The absorption rate of different consolidants was also detected. The physical properties of untreated and treated specimens were compared in order to analyze the performance of the consolidants. Duroscope tests have shown that after consolidation there is an increase in surface strength.
