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Achievements in the field of biomaterials have as a basis three scientific domains: chemistry, biology and physics, then the technical application or the putting up culminating with clinical achievements. Dental prostheses, regardless of their type, replaced the lack of teeth. Although, mainly, many people that lost their teeth could continue life with the help of prostheses in a way pretty decent, dental prostheses shows some disadvantages that make them even unbearable for some people. The study aims at analyzing the biological behavior of sandwich type structures that reunite the classic acrylate and a silicone layer, namely the Flexite type elastic acrylate. We used a silicone material, RUBBER 732 RTV, which is frequently used in mucous-bone support deficits, especially in oral maxillofacial surgery post interventions. The tensile strength was tested ona TEXTENSER traction test machine, in view of establishing the chemical analysis of the 2 materials used. Regarding the maximum tensile strength for sandwich-type test samples, the flexible acrylate - silicone RUBBER 732 RTV structure broke at 1125N, while for the classic acrylate – silicone material a fracture value of 950N was recorded. The structure of the two biomaterials within the sandwich type test samples decisively influences the force and tension at which the fracture occurs, as well as the fracture route, which is linear, without the displacement of fragments, both the flexible acrylate and the silicone being affected, respectively a linear route at the level of the acrylic structure, affecting the acrylate – silicone interface for the classic acrylate – silicone test samples.

Polymer films with high refractive index are suitable for a wide range of applications, such as optical fibers, lens and other components for optoelectronic devices. In this work, polyvinyl alcohol films were prepared from aqueous solutions, which were homogenized by ultrasonication. In order to increase the refractive index, the polymer was reinforced with barium titanate nanoparticles, which are previously ultrasonicated for an adequate dispersion inside the host polymer. The dispersion of the refractive index in visible domain was analyzed as a function of filler percent introduced in polymer, showing that an increase in sample`s polarizability determined an increase in the refractive index values. The reinforcement caused a decrease of Abbe number indicating a higher light dispersion in the samples. Optical dispersion parameters were extracted from dispersion curves, revealing a reduction of band gap from 3.448 eV for pure polymer to 2.605 eV for the sample containing 2% barium titanate. Doping with the ceramic nanofiller determined a increase in optical conductivity and real part of dielectric constant as a result of appearance of new level states in the band gap. The increase of third order nonlinear optical susceptibility and nonlinear refractive index indicates the suitability of the analyzed nanocomposites for nonlinear optics applications.

Composite resin materials for posterior restorations are becoming more and more popular. According to the market, Ormocer materials are more expensive than composite resin this paper is comparing the resistance to fracture between nanohybrid composites and Ormocers under vertical forces to evaluate their cost efficiency in the dental cabinets. 20 teeth were prepared and filled with Ormocer and 20 with nanohybrid composite respectively. All the samples were sent for measuring under vertical pressure with the use of a universal testing machine. The average value of fracture for Ormocer was slightly higher (1541 N) than the average value of fracture of the nanohybrid composite (1431 N). Considering the similarity in the average values of the two materials we should look into the other properties (biocompatibility, shrinkage, aesthetics, etc) to take a final decision. Both materials can be used with the same rate of success taking in account always the protocol provided by the manufacturer.

The form of the outer and inner surfaces of hollow spherical parts determines the developments of some particular categories of efforts during the compression tests. The overall purpose of the research presented in this paper was to study the behaviour of the hollow spherical parts under axial compression. The PLA hollow spherical parts were obtained by 3D printing and using distinct values for certain process input factors. The finite element method was used to theoretically investigate the behaviour of the parts and it highlighted the total plastic deformation of the test pieces. To experimentally verify the theoretical considerations, an L9 Taguchi orthogonal design was performed. The empirical mathematical model thus determined highlighted the stronger influence exerted by the printing plate temperature, printing speed, and part wall thickness.

The needs of environmental protection led to the introduction of composites based on the use of plastics reinforced with biodegradable materials or other easily accessible materials. The overall purpose of the research was to experimentally investigate the possibilities of using some accessible reinforcement materials. Textile based on plants fibers and glass fibers were used as reinforcement materials, while the matrix was a polymer type material. An empirical mathematical model was proposed to highlight the effect of the number of glass fiber reinforcements on the tensile strength. The determined mathematical empirical model and graphical representations highlight how the number of glass fiber reinforcements affects the modulus of elasticity of the composite materials.

It is actual now to work out new radiation protecting sheeting on the basis of non-curing polymeric composition which possess self-adhesion properties, are easily mounted and dismantled and provide high tightness and low permeability. Mechanical properties of non-curing composites consisting of ethylene propylene diene monomer (EPDM), industrial oil (IO), alkyl phenol-formaldehyde resin (PF) with addition of barite (52 %) to the total material volume were investigated in this article. The aim of investigation is to find optimal content of the above mentioned components at which it would be possible to get the following properties: composite would be sticky enough (peel strength not less than 4 N/cm); character of a separation would be cohesive (on a material) and thus there would be no migration of softener and satisfactory resistance of fluidity. The results showed that PF addition till 20 % in the system EPDM/PF leads to the increasing of adhesive strength, in this case optimal oil concentration in the system EPDM/PF/IO is in the interval from 45 till 55 %. New self-adhesion lead-free material, exhibited higher X-ray-shielding properties, is also received in the result of investigation.

The paper presents the mechanical behaviour and properties of a new hybrid vegetal based resin. For this, through static loading tests, the main mechanical characteristics were determined: static Young modulus, breaking strength, breaking elongation and transversal Poisson ratio. Samples of the proposed materials were subjected also to free vibration tests, by clamping them at one end and leaving them free at the other. The observation and results from these were used for deduction of the first vibration mode eigenfrequency, the dynamic Young modulus, the loss and damping factors. Some representative SEM images with an electronic microscope were collected and the samples surface roughness was determined. By using the Thermogravimetric analysis (TGA), the mass loss up to 800° C was investigated. Compared to the other resins that have dammar in composition, the proposed dammar based resin from this research has a 15.32 times higher static Young modulus than the oil palm trunk and 8.885 times higher than the oil palm trunk (OPT) with 20% dammar resin.

The first part of the paper presents the specific issues from the injection molding associated with the water content of the hygroscopic plastics (water adsorption, equilibrium moisture level, chemical affinity, hydrolysis) and recommendations regarding the drying of plastics for injection, the drying methods and defects specific to products injected due to the moisture content. The experimental results on the injection of a polyamide (AKULON) and of a thermoplastic polyurethane (DESMOPAN) presented in the second part of the paper are focused on the surface appearance fault `splay` associated with the different values of moisture content for these two materials, verify the value for the admitted moisture content for two hygroscopic materials, polyamide and thermoplastic polyurethane, and ends with conclusions on the residual humidity allowed and opinions on choosing the drying technology and parameters.

In this paper, experimental investigation, modeling and optimization of the drilling of PMMA are performed using the Taguchi Design of Experiments (DOE), analysis of variance (ANOVA) and artificial neural networks (ANN) methods. Drilling experiments were conducted on PMMA to assess the impact of process parameters (drill diameter, spindle speed, and feed rate) on the hole-quality characteristics (surface roughness, circularity error, and cylindricity error). ANOVA was performed to identify the drilling parameters that have a statistically significant influence on the hole-quality characteristics. A predictive model for the hole-quality characteristics was derived using a four-layer ANN with a backpropagation algorithm and a sigmoidal transfer function at the hidden layers. The ANN model was able to accurately predict the hole-quality parameters with the absolute mean relative errors of the testing data in the limits of 3 to 7%. Based on the experimental results and analytical modeling, it was found that drilling of PMMA requires lower spindle speed and high feed rate when the integrity of the drill hole is the main quality criterion.

This article is devoted to the problem of working out of damping polymer materials which are effective in the wide temperature and frequency range. In the modern world, work is being carried out to create damping polymer composite materials (DPM) from which it is possible to manufacture protective elements and parts of engineering structures of reduced vibration excitability. Existing DPM have a narrow temperature range, within which effective vibration absorption is observed, moreover, most of them go through a vulcanization stage, which increases the cost of the final product, has a harmful effect on environment and allows limited recycling of waste. One of the ways to solve this problem is to replace traditional rubber vibration-absorbing materials with thermo-elastoplasts (TEP). The most promising polymer for TEP is ethylene vinyl acetate (EVA), which has high damping properties, oil resistance and relative incombustibility. In this regard, experimental studies were conducted to establish the patterns of influence of the type and concentration of structure-forming components (plasticizers, fillers, modifiers) on the dynamic mechanical properties of TEP based on EVA in order to develop a new DPM effective in a wide temperature range. The leading method to investigate this problem is a method of dynamic mechanical analysis which allows to get information about changes of mechanical characteristics under mechanical load and controlled temperature and frequency. With the help of detected patterns it was possible to determine type of plasticizer which significantly decreases glass temperature of EVA. The percentage ratio of EVA/plasticizer system is stated, and the type of plasticizer at which the maximum of mechanical losses takes over greater values is accordingly detected. It is revealed, that to work out DPM on EVA basis, which are effective in wide temperature range it is more preferable to add not less than 40 % on volume basis inert fillers, such as talc or mica with addition of 5-10 % of carbon as the hardening additive. The kind of resin improving damping properties and raising rigidity of composites on EVA basis is defined. On the basis of the research, a material was developed which has the following properties: the maximum value of tan δ is at least 0.45 at a temperature of plus 5°C (oscillation frequency 10 Hz); width of the temperature interval within which tan δ is not less than 0.3 from minus 40 to plus 50°С (oscillation frequency 10 Hz); conditional tensile strength of not less than 10 kg/cm2, cold resistance up to minus 50°C.