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Rapid heat cycle molding (RHCM) is a special molding process capable of producing molded plastic parts with high surface quality and improved weldline strength and appearance. This study investigated the influence of the weldline on the tensile strength of RHCM and conventional injection molded (CIM) components. The test specimens with and without a weldline were cut from RHCM and CIM parts for scanning electron microscopy (SEM) imaging to characterize the structure and dimensions of the weldline and tensile testing. The tensile testing results showed that the weldline reduced the tensile strength, but RHCM decreased the tensile strength reduction effect of the weldline. There was no distinguishable difference between the two molding processes for the tensile strength of specimens without a weldline. In addition, a thin surface layer of material containing the V-notch at the weldline was removed from the RHCM and CIM parts to examine its effect on the tensile properties. The thinned-out specimens with a weldline showed improved tensile strength, and specimens without a weldline showed decreased tensile strength, compared to specimens with the original full thickness.

Closed cell polyurethane foams with densities of 100, 140 and 325 kg/m3 were tested in compression at speeds from 0.6 to 500 mm/min. Digital image correlation (DIC) is used to determine the engineering characteristic curve, modulus of elasticity, maximum stress, and the deformation bands that appear during deformation and prior to the final failure of the specimens. By using this procedure both global and local phenomena are observed and analyzed. While each specimen is compressed, the damage behaviour of the foams is directly observed in different stages.

In the first part of the paper we touch on the influence of the processing temperature by injection of HDPE, of PMMA, and of PC+ABS blend on some mechanical flexural properties, while the other factors which could influence the injection remain unchanged. In the second part of the paper, we present the influence of the subsequent pressure in the injection of HDPE, PMMA, and PC+ABS blend on mechanical bending properties, while the other factors which could influence the injection remain unchanged. The HDPE samples were obtained at the following injection temperatures – 180, 190, 200, 210 and 220°C – and at the following subsequent pressures – 800, 900, 1000, 1100 and 1200 bar. The PMMA samples were obtained at the following injection temperatures – 220, 230, 240, 250 and 260°C – and at the following subsequent pressures – 450, 550, 650, 750 and 850 bar. The PC+ABS samples were obtained at the following injection temperatures – 230, 240, 250, 260 and 270°C – and at the following subsequent pressures – 500 bar, 600 bar, 700 bar, 800 bar, and 900 bar. We have used the method of determining flexural properties, such as the flexural stress, flexural deformation, and flexural modulus. It was observed that in the case of HDPE, the highest values of flexural stress were registered at its lowest temperature (180°C) – the flexural stress recorded 28,3038 MPa – and at the highest value of subsequent pressure (1200 bar) – the flexural stress recorded 29.3380 MPa. PC+ABS acts in a similar manner to HDPE. In the case of PC+ABS, 240°C recorded the highest value for the flexural stress of 89.2246 MPa, while the highest subsequent pressure of 900 bar recorded the highest value of flexural stress of 88.5375 MPa. In the case of PMMA, the highest value for flexural stress (124.2563 MPa) was recorded at the lowest processing temperature (220°C) and at the subsequent pressure of 550 bar, where the value of the flexural stress was of 110.5376 MPa. In the case of HDPE and PC+ABS, the flexural deformation is barely influenced by the processing temperature and the subsequent pressure, whereas in the case of the PMMA, the processing temperature and the subsequent pressure influence the flexural deformation. The increase in the subsequent pressure leads to a slight increase of the flexural modulus in the case of the three studied polymers. The increase in the processing temperatures of HDPE and PC+ABS leads to a slight decrease of the flexural modulus, whereas in the case of the PMMA, the increase in the processing temperatures barely influences the flexural stress.

In space filed usually size doesn’t matter but weight does, being a critical point in space structure design stage. Carbon fiber reinforced polymer composite materials are already deployed in many space applications, due to their intrinsic characteristics, mainly their high strength/high stiffness to weight ratio and potential for zero or near-zero CTE, coefficient of thermal expansion. The paper presents the results of the study made on advanced composite exposed to extreme conditions comparable to those found on space environment (Low Earth Orbit – LEO [2000 km). The samples were manufactured from CFRP epoxy composite with different thicknesses (1.2 mm, 1.8 mm, 3.7 mm, 7.7 mm) using autoclave technology. The 1.8 mm thickness samples were coated with 50 and respectively 100 µm of Zn using arc thermal spray technique. Specimens were exposed to UV, gamma radiation and thermal cycles. The results of microstructural, morphological analysis and mechanical characterization showed the aging and damage mechanisms developed post exposure in comparison with reference materials.

The present paper aims to examine the way in which the temperature is distributed when the polyethylene sockets are welded using the electrofusion procedure. This research is necessary because in practice certain problems occur relating to the destruction of these sockets during welding or later. The survey is conducted in cooperation with companies working in the field of welding in polyethylene, complying with the required standing standards.

A series of bismaleimide monomers and polyaspartimides with various structures were synthesized and their structures were confirmed by Fourier transform infrared (FTIR) and proton nuclear resonance (1H-NMR) spectroscopy. Chain extension of bismaleimides was accomplished by incorporating various ether or other groups. Polymers based on these bismaleimides were prepared by the Michael addition of diamines with various structures to bismaleimides. Thermal and dielectric properties of these polymers were studied.

adhesives over acrylic classic prosthesis, but the literature lacks in comparative studies that investigate the effects and advantages of denture adhesives on obturator prosthesis performance. The hypothesis for this study was that the use of the denture adhesive would improve both wearing and efficiency on obturator prosthesis. We evaluated the clinical behaviour of six acrylic obturator prosthesis made on various maxillary defects, with and without a denture adhesive. The adhesive was applied on the prosthesis as recommended by the manufacturers. Patients used the adhesive for 24 hours and, through a questionnaire, they evaluated (comparative with and without adhesive) There are many studies in the literature regarding the effect of denture the following aspects: prosthesis retention, duration of retention, masticatory efficacy, cleansing of dentures, cleansing of gums. The clinical retention of the dentures was correlated to Modified Kapur Index Scale (MKIS) for denture supporting tissues.

The aim of this study was to asses the flexural strength of provisional acrylic resin fixed partial dentures reinforced with glass fiber with the provisional restorations without reinforcement. Three group of specimens were prepared for the flexural strength: Poly Methyl Metacrylate (PMMA) acrylic resin provisional restoration without glass fiber (control), acrylic resin provisional restoration reinforced with glass fiber between the abutments and acrylic resin provisional restoration reinforced with glass fiber including the abutment and the pontic of the fixed partial denture. The flexural strength was tested with a servo-hydraulic testing machine (Zwick Proline Z005 device), with a maximum 5KN force The highest resistance to deformation and fracture was registered in acrylic resin provisional restoration reinforced with glass fiber including the abutments.

In present paper there are given the results concerning wear behaviour in Ringer’s solution of four titanium alloys with 5%Mo, 7%Mo, 11%Mo and 12%Mo. Structural investigations (made by both optic, electronic microscopy and X-Rays diffraction) revealed a dual phase structure consisting from alpha martensite and beta”solid solution, with the constituents proportion depending on molybdenum content. Wear rates were determined using a Talysurf profilometer in Ringer’s solution for the experimental titanium-molybdenum alloys. Finally, the beneficial influence of molybdenum on wear behavior was put in evidence: the higher molybdenum content is, the lower friction coefficient is.

A novel assay for the electrochemical detection of 4-nonylphenol (4-NP) based on carbon nanotubes modified screen-printed carbon electrodes (CNTs-SPCEs) has been investigated. The electrochemical behavior of the modified SPCEs and the mechanism of the oxidation of NP were investigated using cyclic voltammetry. The differential pulse voltammetry parameters were optimized for quantitative determination of 4-nonylphenol. A detection limit of 9.95·10-6 mol·L-1 was obtained for 4-nonylphenol using its oxidation signal at +0.25 V. The disposable sensor showed good performance and was applied for the determination of 4-nonylphenol in tap water with satisfactory results.