Browse Articles

Atomic force microscopy (AFM) has become established as a significant and versatile tool for investigating local mechanical properties of various materials. In addition, through the AFM tip-sample interaction, it has become possible to study the effects of perturbations and modifications to the surface of samples such as composite materials based on polymers that can ensure a transfer selective in the process of friction, trough formed an antifriction selective layer. The selective layer can get by friction between a surface of steel with a sample of composite material (polytetrafluorethylene (PTFE) with added cooper oxide (Cu2O) in various greased media) and formed of very thin layer, tribological performed on surface of steel in which predominated Cu. The accurate knowledge of their response to the continuous AFM scanning could help to design new materials with desirable mechanical properties. In this paper, we present results obtained applying a new method to investigate friction and wear properties on the composite material PTFE/Cu2O. This material is used with high tribological performance at tightening the cylinders of motor vehicles and compressors of petroleum installations. Keywords: atomic force microscopy, selective transfer, substrate, friction and wear, ripple, topography

The copolymerization reaction between bisphenol A glycerolate dimethacrylate (BisGMA) and urethane dimethacrylate (UDMA) monomers was studied and the monomer reactivity ratios were determined on the base of the FTIR data obtained at different times of reaction. Both Fineman-Ross and copolymer composition equations were used. Also ProCop computation program was used in order to establish the values for the reactivity ratios. Keywords: Dimethacrylates; Copolymerization; Monomer Reactivity Ratios; FTIR; ProCop

Nowadays more and more people have or get sick of venous diseases such as venous insufficiency, low foot blood pressure or even the phenomenon of swelling for diabetic people or for the post-birth period. Medical stockings provide a method to fight against these problems since ancient times but the results after every use was in compliance with the level of technology used to produce the stocking. This situation creates a challenge for the stocking manufacturers with developing new technologies and technical materials that give the best results and maximize the effects of compression stockings on the people that wear them. This paper is integrating the total design of a product, regarding the cycle of the product, profitability and satisfaction of the client problems, proposing new ideas of client approach using new technologies like mass customization through computer integrated manufacturing systems including 3 - dimensional body scanning and individual approaches to the client; and using this knowledge develops a kind of compression stockings that are fit-to-wear and satisfy the requirements of the clients concerning the efficiency of the product, comfort properties and durability. Keywords: compression stocking, yarns, total product design, mass customization, apparel for technical applications, 3-D body scanning, computer integrated manufacturing

The paper directs the attention to the detrimental influences exerted by longitudinal notches on the polyethylene pipe surface when subjected under high pressure to long time service. It was shown that the detrimental degree is influenced by the notch depth, working pressure and service duration. Depending on these parameters, researches evinced two types of fracture behaviour: ductile and brittle. The conditions they produce and the transition limits of the ductile – brittle behaviour were demonstrated in two different environments: water and air, at the temperature of 80°C. Keywords: mechanical behaviour, testing duration, environment, PE 80 polyethylene, pressure, longitudinal notches, temperature, pipes

Polymers become more important in everyday life. Although extremely useful in their life cycle, polymers become long-term pollutants. Worldwide, along the increased research in the environmental field, one can obviously observe a keen interest into new biodegradable and biocompatible plastic materials. This paper presents the synthesis and characterization of a new class of biodegradable copolymers based on carbohydrates. An oligomer was synthesized by the polycondensation of 3-benzyl-5,6-(bis(maleyloxy))-1,2-isopropylideneglucofuranose with propane-1,3-diol in the presence of p-toluenesulfonic acid and then it was copolymerized with hydroxypropyl (meth)acrylate, using benzoyl peroxide as initiator. The oligomer was characterized by FTIR, NMR spectroscopy and HPLC-MS, and the copolymers were analyzed using FTIR and thermogravimetry. Keywords: glucose, glycopolymer, maleic anhydride

Most of the Romanian treatment stations use surface waters to obtain potable water. Suspensions elimination is achieved though coagulation with aluminium sulphate or with aluminium polyhydroxychloride. These chemical reagents contaminate the potable water with aluminium ions, which may lead to different diseases of the organism. This paper focuses on a comparative assay of different coagulation agents or coagulation/flocculation agents based on laboratory studies or purification stations. In the same time we propose a new ionic polymer as flocculation agent. Keywords: coagulation/flocculation, polyelectrolytes, potable water

Two-component injection process has multiple uses from the manufacture of household products to manufacture of high precision parts for industry specific computer and automotive industry. Given the importance the paper presents two-component injection process simulation using plastic material and PPG40 Moldflow software. To realize the simulation it was used a research plan by Taguchi with six input parameters, each parameter with two levels, such as nozzle shape, melt temperature, mold temperature, injection time, injection pressure and accuracy imposed. The main results obtained from simulation show the variation of the mold filling time depending on the injection pressure, temperature distribution on the entire volume variation part and solidification time in matrix material. Keywords:injection, nozzle, temperature, accuracy, simulation

The birefringence of some polymeric esters of alkoxy benzoic acid (PEABA) in tetra chloromethane (TCM) was determined by previously proposed interferometric methods in polarized light. An increase in PEABA birefringence when an external electric field acts on the liquid crystal layer was evidenced in this paper. The decrease of PEABA birefringence with the increase in the alternate electric field frequency was also evidenced. The dipolar nature of the collective interactions between the side-chains of PEABA in liquid crystalline phase and also the viscosity of the lyotropic liquid crystal obtained by mixing PEABA with TCM in concentrations of about 10-2 g / cm3, at room temperature are sustained by the results obtained in this paper. Keywords: PEABA birefringence, tetra chloromethane (TCM), polarized light

Extracellular matrix biocomposites based on poly(ester urethane), and hydrolyzed collagen, elastin, chondroitin sulfate and hyaluronic acid have been prepared. Different surface morphologies for each of the test matrices were revealed by Environmental Scanning Electron Microscope (ESEM). The biological material used is a very wide spread aggressive fungal species in all media for life, Mucor mucedo. Evaluation of the biologically active potential of these biocomposites against Mucor mucedo has been done through inoculation onto Sabouraud –agar nutrient medium. Fungal growth was monitored over 60 days.Visual observations of the fungal growth show that Mucor mucedo was aggressive and caused rapid grow after 72 h of inoculation onto Sabouraud-agar nutrient medium, but the biopolyurethane composites samples relatively to the fungal attack particularly showed a different relationship. Keywords: biomaterials; composites; polyurethanes; Mucor mucedo; extracellular matrix

In the context of developing new phosphazene/silica hybrids for preparation of thermally resistant membranes for gas separation processes, two cyclophosphazenes/organosiloxane monomers (1 and 2, scheme 1) were synthesized via aminolysis of hexachlorocyclotriphosphazene (N3P3Cl6) with the monoamine functional trialkoxysilanes: 3-(triethoxysilyl)-propylamine (H2N-(CH2)3-Si(OC2H5)3) or 3-(trimethoxysilyl)-propylamine (H2N-(CH3)3–Si(OCH3)3), respectively, as new starting compounds for cyclophosphazene/SiO2 composites prepared by the sol-gel process. The siloxane monomers, N3P3Cl3[N(CH2)3Si(OCH3)3]3 (1) and N3P3Cl4[N(CH2)3Si(OCH2CH3)3]2 (2), as well as the corresponding composites {N3P3Cl3[N(CH2)3]3}y-(SiO2)41y (1’) and {N3P3Cl4[N(CH2)3]3}y-(SiO2)80y (2’) issues from the sol-gel process, have been characterized by infrared spectroscopy and elemental analysis, TG-DTA-DSC coupled thermal analyses, as well as by XPS, XRD, and SEM-EDAX investigations. Keywords: cyclophosphazene, sol-gel process, organic-inorganic hybrid materials