Volume 43, Issue 2

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: Theoretical and experimental bases for estimating the thickness of the thin anisotropic layers in order to obtain and analyze the total polarized light are discussed, having in view the numerous applications in fundamental and applicative researches. The formulas expressing the thickness of the type wave, half-wave, quarter-wave layers as functions of the birefringence of the anisotropic medium are established. The obtained results could be used for obtaining anisotropic layers, introducing a desired phase difference between ordinary and extraordinary radiations, made up of inorganic crystals or from liquid crystals with a high degree of order at the room temperature. Keywords: wave-; half-wave and quarter-wave plates; birefringence; inorganic crystals; liquid crystals

Abstract: Two copolymers based on N-(4-formyl-fenoxy-4`-carboylphenil)maleimide have been synthesized. The first one was prepared by free radical polymerization of this monomer with styrene. The second one was obtained by chemical modification reaction with p-amino-azobenzene of the resulting first copolymer. The structures of these polymers were identified and characterized by IR, 1H-NMR and UV-VIS spectroscopy. A strong birefringence in the melting state was observed for some of these compounds, suggesting a possible liquid crystalline behaviour. Keywords: maleimide, alternant copolymers, azobenzene groups

Abstract: Transparent thin films of poly(4,4’-azodiphenyl) and poly(4,4’-azostilbene) were obtained by vacuum thermolysis or photochemical decomposition of the corresponding aromatic diazides. Taking into account the working conditions, the thickness of transparent films was about of 0.1 – 0.5 mm. Surface morphology was investigated by atomic force microscopy (AFM). The influence of different factors on the surface morphology in azoaromatic polymer films such as evaporation rate, diazide quantity, support temperature, distance between support and oven has been shown. Atomic force images have revealed several types of morphology: high roughness films with prominent hills and valleys, films with satisfactory roughness but having single hills, and films with smooth surface (average roughness about 1 nm). Keywords: azoaromatic polymers, atomic force microscopy, surface morphology

Abstract: Thin films, in the range of tens of micrometers thickness, have been prepared by casting onto glass plates the chloroform or N-methylpyrrolidone solutions of poly(1,3,4-oxadiazole-ether)s. The polymers have been prepared by nucleophyilic substitution polymerization technique of 2,5-bis(p-fluorophenyl)-1,3,4-oxadiazole with various aromatic bisphenols, such as 4,4’-isopropylidenediphenol, 4,4’-(1,4-phenylene-diisopropylidene)bisphenol or 4,4’-(hexafluoroiso-propylidene)diphenol. They showed high thermal stability with decomposition temperature above 410°C and glass transition temperature in the range of 187-211°C. The polymer films exhibited good mechanical properties with tensile strengths in the range of 36.92- 44.50 MPa, tensile modulus in the range of 1.42-1.74 GPa and elongation at break in the range of 3-91%. Electrical insulating properties of polymer films were evaluated on the basis of dielectric constant. The values of the dielectric constant at 10 kHz were in the range of 2.98-3.18. Keywords: poly(1,3,4-oxadiazole-ether)s, thin films, mechanical properties, dielectric constant

Abstract: The paper analyzed the chemical resistance of polyethylene (PE) pipes, some attention paid to the general phenomenon of degradation which influences polyethylene life. The influence of synthetic condensate (50% (by mass) n-decane and 50% (by mass) 1-3-5 trimethylbenzene) about the strength and durability of polyethylene pipes was established . Keywords: polyethilene pipe, chemical resistance, strength, durability.

Abstract: In this paper, the behaviour of polyurethane protective sheets on metallic surfaces in g-radiation field was studied. The irradiation effects consist of the decrease in the sheet thickness and the worsening in the brightness of modified polyurethane protection. Kaywords: polyurethane protection, irradiation

Abstract: Polystyrenes with pendent diquaternary 4,4-bipyridinium groups are polystyrenes containing pendent viologen groups. They were obtained by the reaction of chloromethylated polystyrene with N-monoquaternary-4,4’- bipyridinium bromides as: N-(p- H, NO2, Cl) phenacyl-4,4’-bipyridinium bromides and N-carbomethoxymethyl/ethyl-4,4’-bipyridinium bromides (2a-e). Thermal stabilities of polystyrene with pendent viologen groups were investigated. The influence of the chemical structure of pendent viologen groups on the thermal stability was performed by thermogravimetric analysis in the dynamic conditions of temperature and atmospheric air. The substituted compounds undergo a thermal degradation process that took place by a complex mechanism in three steps. These steps are disscused from both kinetic parameters and thermogravimetric characteristics points of view. The thermostability of low molar mass compounds 1a-e decreases in the following order: 1c > 1a > 1e > 1d > 1b and the same thermostability order was found in the case of chloromethylated polysulfone derivatives (2c > 2a > 2e > 2d > 2b). Keywords: Thermal behaviour, thermal stability, chemical modificated polystyrene, N-phenacyl and N- carbomethoxymethyl/ethyl- 4,4’-bipyridinium groups, viologen group

Abstract: The residence time distribution at the exit of mixing zone in a fully intermeshing, corotating twin screw extruder was determined with a stimulus-response technique. The operating parameters investigated were screw speed and feed rate. The residence time decreases with increasing screw speed and feed rate. Keywords: residence time distribution, corotating twin screw extruder

Abstract: A solvent and catalyst-free synthesis of a polyphosphate was accomplished. The reaction involved a gas-liquid polycondensation between phenylphosphoric dichloride and phenolphthalein. The polyphosphate was characterized by IR, 1H-NMR, inherent viscosity, thermal analysis and molar mass. Polyphosphate was stable up to 260oC. Keywords: gas-liquid polycondensation, polyphosphate

Abstract: The structural characteristics of polymeric composites based on EPDM, (ethylene-propylene-dien monomer) rubber, which have various percentages of high density polyethylene, were studied by IR spectroscopy and optical microscopy, evidencing the influence of processing parameters. The EPDM rubber was vulcanized using either sulphur and accelerators or peroxides. The influence of the dynamic conditions (rotation rate during the mixing of rubber with polyethylene) on the solvent retaining by maintaing 1-24 hours in benzene, chloroform and MEC (methylethylcetone) was shown by weighing the samples. The results of research could be used for choosing the suitable compositions, processing conditions as well as the fields for application of these composites. Keywords: EPDM (ethylene-propylene-dien monomer) rubber, polyethylene,IR spectroscopy, microscopy

Abstract: This paper focuses on the relationships between the chemical structure of mesogenic polymer molecules and the temperature range over which they can form liquid crystalline phases. The purpose of this presentation is to illustrate the influence of the various types of chemical modification upon transition temperatures and to show how polymers can be designed with liquid crystalline stability in an optimum temperature range. Keywords: thermotropic liquid cristalline polymers, transition temperature, design

Abstract: Various bismaleimides and biscitraconimides containing ester and ether units in the main chain and having SO2 groups were synthesized. Monomers with ester units were synthesized by condensation between 3(4)-maleimidobenzoyl chloride or 4-citraconimidobenzoyl chloride with 4,4-hydroxyphenyl sulfone. Bismaleimide and biscitraconimide with ether units were prepared by reaction between maleic anhydride or citraconic anhydride with 4,4-bis (4-aminophenoxy)diphenyl sulfone. Keywords: bismaleimide & biscitraconimide monomers

Abstract: The paper presents the changes in chemical composition and hardness of cylindres used for grinding of rubber wastes. Based on experimental results obtained, some technical solutions can be suggested in order to determine a considerabile growth the life equipment. Keywords: rubber waste grinding

Abstract: The use of Rapid Prototyping (RP) processes in manufacturing cellular solids offers the advantages of controlling the distribution, dimensions and interconnection of cells, which influence their micro and macro-structural properties. But not all RP processes are able to build cellular solids with closed cells, this article analyzing the capacity of Fused Deposition Modeling (FDM) process to manufacture this type of structures from ABS material. Using a test part containing cubic and spherical cells, it is shown that FDM can manufacture structures with completely enclosed voids, but only for a certain range of dimensions. This approach opens new study directions such as the possibility to analyze the mechanical behaviour of this type of cellular materials with closed cells and controlled geometry, or to use them as test parts for detecting voids in injection moulded parts. Keywords: fused deposition modeling, rapid prototyping, ABS polymer material, cellular solids, closed cells

Abstract: In this paper the experimental results obtained at grain refining of 6082 aluminum alloy are presented, using an original method which consists in insertion of refining master alloys in two stages: in the first stage the AlTi5 elaborated at low temperature, and in stage number two AlTi5B1 classic ternary master alloy. The method ensures into the solidification process, both the elements that act by stopping the grain growth (Ti) and the nucleation centers (TiB2, AlB2, (Ti, Al)B2). Keywords: prealloys, refining

Abstract: The microelectronic package continues to evolve in order to improve the performance and integrate new technology such as multidie architectures, thinner substrates, increasing integration of passive components, increasing thermal design power and lead free interconnects. Package materials must be designed to enable the electrical and thermal performance requirement and to provide high-reliability performance. Maximum heat dissipation is a requirement for today’s higher power integrated circuit devices. The maximum heat dissipation is achieved by mounting active devices directly to high thermal conductivity heat sinking substrates or packages. Direct attachment requires a compatible coefficient of thermal expansion (CTE) value of the heat sink material to avoid stress failure of the IC device. In this paper, the thermal behavior of polymers used in cooling electronics with nonlinear electrical lumped elements as a function of temperature, physical properties and sizes of a heat sink element were modeled. Keywords: high thermal conductivity polymers, heat sink, safe operating area, nonlinear thermal impedance electrical model