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In this paper we study the non-uniformity that appears in the composite bars reinforced with fiber glass fabric. We defined a factor which characterizes the non-uniformity from the composite materials. We will give a formula for calculating this coefficient and a formula for the elasticity modulus of the composite bars, with two zones in which the volumetric proportions of reinforcement are different. We compared the theoretical results, which give the values of the uniformity coefficient and elasticity modulus, with experimental results obtained for three sets of samples made from ambresit and reinforced with fiber glass fabric. Keywords: composite materials, non-uniformity coefficient, elasticity modulus

Over the last years the use of bioabsorbable materials in orthopaedic surgery has increased exponentially. One of the first surgical interventions to take benefit from these absorbable materials was the reconstructive surgery for the anterior cruciate ligament (ACL) of the knee, meaning the use of interference screws for the primary fixation of the ligament graft. The aim of this paper is to present the main types of screws of this kind, used in current practice, the preferred manufacturing materials and to evaluate the standard implantation procedures in terms of the stability they ensure to the ligament graft. Keywords: bioabsorbable screws, ACL reconstruction, ligamentoplasty

The present study pursues the influence of polyelectrolytes based on maleic co-polymers with styrene and vinyl acetate under the form of natrium salt, on the colour parameters CIEL*a*b* of the Melana type polyacrylonitrile fibers dyed with Methylene blue. The work is part of a study on the metachromacy of cationic dyestuffs at dyeing the polyacrylonitrile fibres in the presence of cationic polyelectrolytes. The colours attributes are analyzed in terms of the tinctorial conditions: polyelectrolyte character and concentration, dyeing temperature and during time. Keywords: maleic polyelectrolytes, polyacrylonitrile fibres, colour differences, tinctorial parameters, methylene Blue

The introduction of the thermo and fotopolymerizable acrylic resins for the manufacture of total prostheses base has revolutionized dentistry in the 20th century. Thermopolymerizable acrylic resins (methacrylic acid derivatives) are found to have a low degree of toxicity on oral tissues after resection of the lower facial floor. It raises the question of thermo and fotopolimerizable acrylic resins toxicity compared with transplanted tissues from outside the oral cavity, in these cases compared with free osseomiocutaneous fibular flap. With the help of these resins, the restoration of the mastication, swallowing, phonation and physiognomy functions was achieved. The impact of free flaps in reconstruction of the mandible and oral floor and osseointegration of dental implants ensuring the stability of dentures are remarkable, allowing the reconstruction of the lower facial floor in a very high degree and the restoration of all functions. Keywords: acrilic resins, reconstruction lower floor

In this study, the ethylene propylene terpolymer elastomer (EPDM) was chemically changed by sulphonation which was subsequently used in preparing compounds by adding neutralization agents, ionic and non-ionic plasticizers, fillers, and polyolefines with the view to obtain an ionic thermoplastic elastomer based on sulphonated EPDM. The chemical changes in EPDM were revealed in the following ways: measurement of sulphonation reaction yield, FTIR analysis and tests for physical-mechanical characteristics of the unchanged and chemically changed EPDM. The extent to which the neutralization agent, ionic and non-ionic plasticizers, filler, polyolefines are influencing the characteristics of the resulted products was determined with the purpose of selecting the best types of ionic thermoplastic elastomer based on sulphonated EPDM. The new type of thermoplastic ionic elastomer can be processed by adequate techniques for the thermoplastic materials. Key words: chemical change, sulphonated EPDM, thermoplastic ionic elastomer

This paper presents the investigation of the catalytic agent influence on the crystallinity degree of polymers (metallocene polyethylene). Differential scanning calorimetry was the method used to determine the crystallinity. It was underlined that the catalyst has a great influence on the crystallinity of metallocene polyethylene. The results are in good agreement with the preceeding ones [4]. Keywords: polymer, metallocene polyethylene, crystallinity, differential scanning calorimetry, baseline method, First Law method

Three aromatic silicon-containing poly(1,3,4-oxadiazole-amide) were synthesized by solution polycondensation reaction of aromatic diamines containing performed 1,3,4-oxadiazole ring with a diacid chloride incorporating diphenylsilane unit. All polymers are soluble in polar organic solvents such as N-methylpyrrolidinone, dimethylformamide or dimethylacetamide. Thin films having good mechanical properties were made by casting polymer solutions onto glass substrates. These polymers exhibit high molecular weights and narrow molecular weight distribution. They are highly thermally stable, their decomposition being above 415°C. Glass transition temperature (Tg) is within the range of 246-346°C. The values of Tg, tensile strength and elastic modulus were correlated with the conformational rigidity parameters. Absorption and photoluminescence properties were also measured and discussed. Keywords: aromatic silicon, poly(1,3,4-oxadiazole-amide), aromatic diamines

For calendaring sheets with a desired final thickness, the design process of the calender unit includes, among other parameters, the calculation of the flow velocity and pressure fields in the gap between the rolls. In this paper, the fundamental aspects about the behavior of the molten polymer during the calendaring process are analyzed and the relations between the variables of interest are determined for calendring of high density polyethylene (HDPE), polyvinyl chloride (PVC) and ethylene styrene interpolymers (ESI). Keyword: plastic materials, calender, calendered sheet

Lubricants based on vegetable oils are a growing in attraction various applications. Environmentally friendly, vegetable oils and their derivatives constitute alternatives for a large variety of mineral based lubricants. New lubricating oils obtained from mixtures of vegetable oils (sunflower, SFO and rapeseed oil, RO) and synthetic diesters (di-2-ethylhexyl-adipate (DOA)) are studied. The physico-chemical characteristics of all these mixtures are given together with the differential scanning calorimetry (DSC) and thermal gravimetric (TG) analyses. Keywords: vegetable oils, diesters, environmentally lubricants, di-2-ethylhexyl-adipate, sunflower oil, rapeseed oil

The biodegradable polymeric materials can be achieved based on several methods among which, the compounding of natural polymers with synthetic ones has a significant utility. The biodegradable materials based on polyvinyalcohol (PVOH) and starch have a practical interest because can be entirely destroyed in environment, in controllable times based on the PVOH hydrolysis degree. The silicate presence in the PVOH - starch systems determines the increasing of the glass transition with 4 - 11 0C and of the maximum of the melt temperature with 10 0C. If the silicate was functionalizated then its interaction with the polymer is underlined by the melting uniformity . Keywords: polyvinylalcohol, starch, thermic properties, nanocomposites