Volume 40, Issue 2

Abstract: The relationship for the calculus of flow in a single screw extruder was inferred based on the analysis of the real movement of the powder material in the feeding zone, considering the screw rotating and the barrel stationary. The relationship is applicable to extruders with the barrel in the feeding zone both smooth and grooved. Both the slipping of the powder material with respect to the surface of the screw and the existence of a velocity profile on the depth of the powder layer were taken into consideration when establishing the flow relationship. The fundamental hypotheses of the new theory are: - barrel stationary and screw rotating; - in the powder layer, powder particles have a relative motion. The relationship for the direct calculus of the deviation angle b was deduced. From the analysis of the results obtained applying the relationship for flow, where the flow factor can be calculated with the relationships in the paper, one would notice that the flow will grow both with increasing the depth of the channel in the feeding zone and the increase of the friction coefficient between the powder material and barrel,, as well as the one between the powder material and screw. Keywords: extrusion, optimization, flow factor, deviation angle

Abstract: CaCO3 is the main component of the raw materials powder mixture to obtain Portland cement. In the clinkerization process, with increasing the working temperature, physico-chemical processes take place in the raw materials, the most important being the endothermal process of CaCO3 decomposition. Thermal efficiency of the plant is given by decarbonization degree of raw materials at feeding rotary kiln. It is proposed a mathematical model for correlation decarbonization degree with the main parameters (temperature, time, granulometric characteristics of the raw materials).

Abstract: Some photosensitive structurally different polyamides were obtained using as starting monomers various dicarboxylic acids and 2’-(cinnamoyloxy)ethyl-3,5-diaminobenzoate. Their synthesis is based on the Yamazaki-Higashi procedure. The characterization of the prepared polyamides was accomplished by spectroscopic and thermal measurements.

Abstract: Due to physical properties of the composite materials based on resin – textile fibres cover, in the present different utilisation areas such as: terestrial, aerian and naval transport, civil and industrial engineering, medical tehnique, food industry, sportive articles etc. This paper present ssthe determination of the water’s absorption in composites resin – flax, resin – cotton, resin – hemp.

Abstract: By exposure to the environment of polymer wastes, the disintegration and degradation processes take place by simultaneous and concurrent mechanisms, as photodegradation, hydrolisys, thermooxidation and biodegradation. The latter may be described as a complex process taking place in several steps. In a first step of the biodegradation process, the polymer with low molecular mass suffer a hydrolisys reaction enzymatically catalyzed, resulting in a mixture of oligomers and intermediates with low molecular mass and different chemical structures. The next step is preceded by microorganisms invasion, transforming the carbon and the hydrogen of polymers and respective intermediates into CO2 and H2O. In the study there are presented some reaction and initiation mechanisms of the biodegradation processes of some synthetic polymers susceptible to biodegradation.

Abstract: In this paper a relaxation model for polymeric materials is presented.

Abstract: The copolymerization of octamethylcyclotetrasiloxane and methylhydrogensiloxane oligomers was carried out using a styrene-divinylbenzene copolymer with sulphonic groups as catalyst (VIONIT CS-34C). The conversion versus time function was studied at different temperatures. It was found a first order reaction towards monomers.

Abstract: This work presents a study on the interaction that a phenolic hindered antioxidant (Irganox-1076) and new reactive dyes derivated from 3H-aza-1-oxa-2H-thioxo-5,8-phenalendisulphonic acids, have upon izopolipropylene thermooxidation. The study was performed by chemiluminescence technique (CL). Synergetic effects were observed between reactive dyes used and phenolic antioxidant in thermooxidation protection of the polymer.

Abstract: In this paper, some models for gel and glass effects – a new empirical model and Chiu’s model – are checked under batch and semibatch, isothermal and nonisothermal reaction conditions. The chemical initiated free radical polymerization of methyl methacrylate is considered to be achieved in a bulk process and the reaction mechanism takes into account the azobisisobutyronitrile decomposition, propagation, chain transfer to monomer and termination by disproportionation. In the exponential relations that represent the dependence of termination and propagation rate constants on monomer conversion (gel and glass effects), the coefficients are polynomials of forth degree in temperature. For batch operating conditions, the simulations performed at different temperatures and initiator concentrations give results close to experimental ones. In semibatch operation, an instantaneous addition of initiator at different reaction times and different temperatures was considered. Step changes in temperature performed at different reaction times represent an other type of operation taken into account in this paper. In the semibatch and nonisothermal reaction conditions, the simulation results of the two models agree with experimental data even if the same values of parameters as for batch isothermal operation were used. This paper demonstrates the generality of the exponential models and also emphasizes the possibility of controlling polymer properties and reaction time by semibatch and nonisothermal operations.

Abstract: Aromatic diamines are antidegradants with outstanding capability in protection against oxidative and ozone destruction of elastomers and elastomer-based compounds. Their performances are dependent, among others, on their solubility in elastomer matrix and on migration rate to the matrix surface. In an attempt to control solubility and migration of amine antidegradants, the influence of some special additives (fatty amines, fatty amides, ethoxilated phenols) has been investigated and migration characteristics like diffusion coefficient, migration rate and specific migration are presented and discussed. The obtained data correlate in a semi-quantitative manner with main physical characteristics of vulcanizates in circumstances of thermo-oxidative and ozone degradation.