Browse Articles

The study investigates the effect of several injection moulding parameters, such as the melt and mould temperature, on the adhesion obtained at the moulding of bi-component tensile test specimens. Mono- and bi-component specimens were subject to uniaxial tensile tests. The aim is to obtain a model analysis for the study of the mechanical behaviour of bi-component parts submitted to uniaxial tensile tests. The localised information on the state of stresses and strains at the interface between the two polymeric components is obtained through this analysis.The use of the G’Sell-Jonas model offers a good prediction regarding the mechanical behaviour of the two component tensile test specimens on both the elastic and the plastic regions. The simulation of the mono-component tensile test showed a good agreement between the experimental and the predicted results, with a correlation coefficient ranging between 0.9973 and 0.9998. High levels of confidence were obtained for the mono-component tensile test specimen results, further applied for FEA analysis of the two-component specimen (HDPE/LDPE). The necking effect observed in the experiments, at a 255°C melt temperature for the LDPE, was similar to the one revealed by the finite element analysis. Keywords: polymers, adhesion, tensile test, FEA

This paper analyses the influence of the grind percentage on some mechanical properties of various injection-molded items in the automotive industry, which are made of acrylonitrile butadiene styrene (ABS), polyamide 6.6 (PA 6.6) and polyoxymethylene (POM). The specimens had the following compositions: new material 100%, new material 80% + grind 20%, new material 60% + grind 40%, new material 40% + grind 60%, new material 20% + grind 80% and grind 100%. The mechanical properties were measured using tensile tests, the Izod impact test and the Shore Durometer hardness test. It was observed that the hardness of the three tested polymers is not significantly influenced by the increase in grind percentage. The shock resistance of ABS and PA 6.6 decreases when the grind percentage is increased, while for POM the increase in grind percentage leads to an increase in shock resistance. The tensile strength at break decreases when the grind percentage is increased from 0% to 40% for ABS and POM. The further increase in grind leads to a slight increase in the tensile strength at break. In the case of PA 6.6 the tensile strength at break increases along with the increase in grind percentage. Keywords: acrylonitrile butadiene styrene (ABS), polyamide 6.6 (PA 6.6), polyoxymethylene (POM), tensile tests, the Izod impact test, the Shore Durometer hardness test

This article presents a new material obtained from a mix of waste of carbon fibre, sand and an epoxy resin. The obtained material values the reinforcement material waste that is accumulated in the process of production, of the companies that produce fibre-reinforced composite material. This new material obtained from the integral value of the carbon fibre waste is used as a material for the consolidation of the moulds made of composite material or in the domain of construction materials. The authors realize a study regarding the physico-mechanical characteristics of the morphology of the breaking surfaces and a chemical analysis of the EDAX constituents. The mechanical characteristics of this new material at compression, show us values doubled from the ones of a classic concrete and a density decreased with approximately 20 percent. Keywords: composite materials, carbon fibre, epoxy resin

Among the composition and morphological structure field of biomaterials, the biodegradable biocomposites based on, synthetic and natural polymers as biocompatible spongious matrices has been studied. The biodegradable synthetic polymers have good mechanical properties, low toxicity and a controlled degradation kinetic. However, these polymers are hydrophobic and do not exhibit adequate surface for cells attachment and proliferation because of receptors absence for cells recognition. The natural polymers show good cellular interaction and high hydrophilicity. The advantages of biocomposites made of both synthetic and natural polymers are holding both physico-chemical properties of synthetic polymers and biocompatibility, cellular adhesion properties and variety of biological interactions induced by the contact between cells and natural polymeric support. The aim of this study was the synthesis of biocompatible porous structures by compounding synthetic polymers - (poly(L-lactic acid) (PLLA), poly(D,L-lactic-co-glycolic acid) (PLGA) which are biocompatible, biodegradable but hydrophobic, with natural polymer – collagen, the main protein of extracelullar matrix. The biocomposites were prepared in a polymer: collagen ratio of 2:1 by adding synthetic polymer solution, solved in chloroform, to aqueous collagen gel. The synthesis of biocomposite matrices was achieved by lyophilizing of synthetic polymer/collagen blends after dialyse against 1M KCl. Both uncrosslinked and crosslinked samples were prepared. As standard sample the uncrosslinked and crosslinked collagen matrices were chosen. The morphology of biocomposite matrices PLLA/collagen, PLGA/collagen was characterized by SEM in order to investigate the macro-, micro and nanoporosity. Physico-chemical characterization was focused on thermal stability (DSC and TGA) and surface hydrophilic character by water vapours absorption, water vapours permeability and water absorption. Keywords: biocomposites, collagen, biodegradable synthetic polymers

Polymeric nanoparticles are widely used as drug carriers in order to achieve the targeting of drug to the ill tissue. N-vinyl-2-pyrrolidone and itaconic anhydride were copolymerized and the alternating copolymer was then grafted with PEG of different molecular weight, to form amphiphilic copolymers. The grafted copolymers have been used to prepare polycaprolactone nanoparticles. The PCL has been chosen as it can mimic the hydrophobic drugs. Several emulsions were stabilized and characterized by SLS. The synthesized copolymers proved to be effective in stabilizing nanoparticles. The mean diameter of nanoparticles was stable in time, over 12 weeks. Keywords: Polycaprolactone nanoparticles, amphiphilic surfactants, radical polymerization

This paper presents the results of the experimental researches made on an extruder for pasta, in which the extrusion die has the active extrusion surfaces from two different materials: plastic and metallic. The subject is focused on polytetrafluoroethylene, to indicate the advantages of this material comparative with bronze. The experimental part consists of diameter measurements of the intern extrusion holes with the optic microscope. Keywords: polytetrafluorethylene, bronze, extrusion, die

The paper presents experimental data regarding a number of five new polymeric termo-resistant pigments synthesized by condensation of Perylene 3, 4, 9, 10-tetracarboxylic dianhydride with 2-Cl-p-phenilendiamine in various molar ratio. Reaction products were purified and characterized by elemental analysis, UV-VIS, IR and thermal analysis. Keywords: perylene 3, 4, 9, 10-tetracarboxylic dianhydride, 2-Cl-p-phenilendiamine, polymeric thermoresistant pigments

The concept of thermal homogeneisation efficiency, hht was defined, giving an indication on the thermal homogeneity realised by a certain zone through the heat generated by internal friction. Its optimal value corresponds hht = 1. This concept was then applied to the calculus of thermal homogeneity at the flow of a power-law non-Newtonian polymer melt, through a rectangular slit, similar to the flow over the barrier flight f. The relationships obtained for temperature rise due to heat generated through internal friction allowed the calculus of hht in a given case. Kewords: thermal homogeneity, internal friction, polymer melt

This work presents the results obtained from experiments of rigid PVC stabilization both lead stabilizer and earth alkaline carbonates as co stabilizer. Efficiency of stabilizers was tested by dynamic tests (roll mill processing or Brabender plastograph) and static test (thermogravimetric analysis). Both types of test were in concordance from point of view of stabilization efficiency and from thermal analysis can be predicted the thermal lifetime of PVC products. This is an important fact for durable usage or for recycling products made from PVC. Keywords: PVC stabilizers, roll mill, Brabender plastograph, thermal analysis, lifetime prediction, isoconversional method

In this paper it was established the influence of the processing temperature of the injection moulding on the in-mould pressures and on the characteristics of the obtained items used for high performance sport products. The processed polymers were: polypropylene (PP), polyamide 6,6(PA66), polycarbonate (PC), polyurethane (PU), polyoxymethylene (POM, polyacetal). The injection machine employed was ENGEL G/11/10/116/3 produced in 2002. For the correct temperature measurement in the injection cylinder nozzle a DYNISCO Ti422J thermocouple was used and for the determination of the cavity temperature, a thermocouple 2024T model, produced by Digitron Instrumentation Ltd. was used. The mould cavity pressure was measured with a transducer model IDA, produced by Dynisco Europe GmbH. Keywords: injection moulding, pressure, temperature