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The main purposes of this article are: 1) the minimization of an objective multi-criterial function which implies the reaction time, the polidispersion coefficient and the monomer conversion; 2) the obtaining of reaction conditions (temperature and initiator concentration) which determine the realisation of some final imposed values for conversion and polymerization degree. Within the optimization algorythm there were successively considered as decision variables: 1) a single value of temperature (the isothermal case) and the initiator concentration; 2) two temperature levels and the initiator concentration; 3) thee temperature levels. Of the three optimization strategies, the right one was proved to be the temperature trajectory constituted of two values. The obtained optimal politics essentially depend on the objectively chosen function and on the weight factors attached to each interest measure.

The ortocresol, the p-aminophenol and the formaldehyde were taken in different molar ratios and condensed in the presence of hydrocloric acid as catalyst and of toluene) N-methyl pyrolidone mixture as extraction agent of the reaction water. The condensing products are polymers with a low molecular mass, friable solid substances soluble in polar organic solvents which show colors from transparent pink for the ortocresolformaldehidic resin, to dark brown for the p-amino-phenolformaldehidic one. The obtained formaldehidic resins were structurally characterized using IR and 1H-RMN spectroscopy. The thermal properties were also investigated.

This paper presents the performance of two aminic antioxidants (TMQ and PBN) and a phenolic antioxidant (SPH) in formulations based on diene rubbers, typical for tyre treads. An imidazoline was used as secondary accelerator and the influence of antioxidant nature was investigated following its influence on scorch safety, curing behaviour, tensile strength, fatigue behaviour, abrasion performance, and thermo-oxidative degradation.

The work presents a study on a possible solution of metal replacement for pneumatic drives rods working in dry friction condition. If the total absence of lubricant and others contaminating agents is required, due to specific working environment, the pneumatic drives use is recommended. The rod sealing system is elastomeric lip seal based and works, in this case, in linear sliding dry condition. The authors tried to establish the way that polymeric material replacing the metallic rod behaves, taking into account the working conditions. Considering that the sealing system failure is due to wear, a closer investigation is performed at surfaces level by optical and 3D reconstruction methods. The observations allowed an optimization of polymeric rod rubber lip seal system in dry sliding conditions from the materials choosing point of view. Keywords: dry friction, elastomer-plastomer couple, linear sliding motion

Working on high structures is one of the jobs in the cities vertically developed. The abilities of climbing workers are used for the purpose of mounting publicity banners, cleaning building face, mounting objects on buildings etc. The use of fall arrester equipment is made under strict surveillance and training of the workers because of imminence of the accidents. Before sailing, the fall arrester equipment is tested and certified. Keywords: polyethylene, shock absorber, fall arrester, climbing, HBM MGC

Conventional methods for processing and shaping plastics parts (mold injection, thermoforming, extrusion etc) require heating (melting) process in which plastics material is soften or liquefied firstly and then imparted by using different dies and techniques. However, plastics material could be formed without any heating and for that purpose a few non-conventional procedures have been developed. An alternative to conventional shaping of plastic parts offers metal forming processes and cold forming technique.In this paper results of theoretical, numerical and experimental investigation of cold forming of plastics are present. Traditional metal forming processes such as upsetting and backward extrusion were applied for shaping billets made from HDPE and PA. Both processes are simulated by FEM and Simufact.Forging 8.1 program package. Numerically predicted load-stroke diagrams are compared to those experimentally recorded. All necessary material data and process parameters were determined according to the methodology which is used in metal forming processes. Keywords: thermoplastics, cold forming, FEM

The main characteristics of pressure sensitive adhesives are: peel resistance, shear and tensile strength. This work presents the tensile tests and related phenomena of pressure sensitive adhesives based on polychloroprene rubber with wood and steel substrates. The tensile breaking mechanism for the adhesive assembly is proposed and discussed within this article. Keywords: pressure sensitive adhesives, elastomers, tensile strength, wood, steel

In this paper were investigated influences of various types and concentrations of crosslinking agents on the properties of thermoplastic vulcanizates based on ethylene-propylene terpolymer rubber (EPDM) and plasticized poly (vinyl chloride) (PVC). Three different crosslinking systems were used: (a) common method with sulphur and vulcanization accelerators (tetramethylthiuram disulfide and mercaptobenzothiazole); (b) crosslinking with di(tert-buthyl peroxi-isopropyl) benzene Perkadox 14-40B-GR and co-agent trimethylol-propane trimethacrylate TMPT DL 75 (c) vulcanization with phenol resin Ribetak 75-30E and tin chloride dehydrate. The influence of each crosslinking systems on cross-link density, mechanical properties and DSC analysis of samples were investigated. The hardness shows a slight decrease as a result of dynamic vulcanization, because this is a way to disperse large amounts of elastomer in the thermoplastic matrix, resulting in a refined morphology. It was observed that the highest values of crosslinking density and 100% modulus were obtained by using the classic cross-linking with sulphur and accelerators, and that for a reduced amount of crosslinking agents used, there was a decrease in crosslinking density. Elastomer crosslinking led to an increased Tg and decreased Tm. These blends can be used in the manufacture of hoses, gaskets, footwear constituents etc. Keywords: TPV, EPDM, PVC, cross-link density, differential scanning calorimetry

Acid polyurethane of hard type was prepared to be further treated in hydrothermal conditions at high pressures of 20, 40, 60 and 80 atm. The influence of pressure on chemical structure and morphology of macromolecular chains have been investigated using Fourier transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). Three endothermic peaks appear in hydrothermally treated polyurethanes, being related to conformational changes due to polymer shrinking, decomposition and melting. Their corresponding enthalpies increase with pressure, probably due to a more compact polymer structure at high pressure. Under the influence of pressure, macromolecular chains modify their conformation and approach each other, leading to an increased density of the hydrogen bonds. Stretching vibrations of the –C=O group are shifted from 1746 to 1724 cm-1. There is an optimum pressure (60-80 atm) range where the polyurethane presents an increased capacity of interaction through carbonyl groups (r1 =1.295 at 60 atm) which is favorable for further composite synthesis. Keywords: acid polyurethane, high pressure, hydrothermal process, IR spectroscopy, DSC

The replacement of classical materials used in industry with other more important, cheaper and environment friendly ones and also the prevention of corrosion is one of the goals in the research area. Electrotechnical industry and engineering needs this special material. The conductive and semiconductive coatings belong to these special materials and occupy a large application domain in modern industry, used to remove the electrostatic charges, and for the shielding effects (i.e. Faraday screen, protective coat for the high voltage cables etc.).In this paper it is studied the stability in time of semiconductive lacquers based on polianiline.