Volume 42, Issue 2

Abstract: The paper presents some basic considerations to establish the optimum conditions for designing the ultrasonic equipment employed in plastic flow activation. In the first part, the paper presented general considerations and recommendations for the design of the ultrasonic horns. The associated conditions are submitted at a critical discussion correspondingly at the particular industrial applications. There was emphasized a particular effect of the ultrasonic activation – namely “the thermo-pellicular effect”- specific for the particularized activation conditions of the viscous-elastically mediums under pressure. The effect is characterized by the appearance of a fine layer of melted overheated material with lubricant effect on the lateral side of the ultrasonic horn. The paper includes a computer-aided application focused on the design of an ultrasonic horn employed in plastic manufacturing and some particular applications in plastics injection and extrusion. Keywords: plastic, flow, rheology, ultrasonic, activation, design, concentrator, industrial, application

Abstract: This paper presents the influence of styrene-butadiene block-copolymers on the modification of high density polyethylene wastes. The modification of this polyolefine is a means of improving the mechanical properties, especially the impact strength, in order to increase the posibilities of recycling high density polyethylene wastes. Keywords: styrene-butadiene block-copolymers

Abstract: A series of five new aromatic polyhydrazides containing pendent acetyloxybenzamide groups has been synthesized by low-temperature solution polycondensation of 5-(4-acetyloxybenzamido)-isophthaloyl chloride with dihydrazides of terephthalic, isophthalic, 2,5- or 2,6-pyridin dicarboxylic acids, or with p-aminobenzhydrazide in N-methyl-2-pyrrolidinone (NMP). These polyhydrazides were gradually thermally treated up to 280°C in order to be converted in corresponding poly(1,3,4-oxadiazole)s. The inherent viscosity of polyhydrazides is in the range of 0.31-0.69 dL/g. The polymer structures were confirmed by infrared spectra. The polymers were characterized from solubility and thermal properties point of view. Keywords: polyhydrazides, poly(1,3,4-oxadiazole)s, 5-(4-acetyloxybenzamido) group, thermal stability

Abstract: Low density polyethylene films were g-irradiated in various oxidative environments: air and aqueous solutions containing hydrochloric acid and different chlorides (MnCl2, CuCl2, NiCl2, and CoCl2) in the concentration of 10 % (w/w). Radiochemical degradation of polyethylene was assessed by IR spectroscopy at various characteristic vibration regions: 1720 cm-1 (C=O band), 3440 cm-1 (OOH/OH band) and 1630 cm-1 (C=O in the vicinity to C=C). Low dose rate (0.4 kGy/h) was applied over the dose range 0-4.5 MGy at ambient temperature. The two main processes occurred during high energy exposure: degradation and crosslinking were pointed out. Keywords: polyethylene, degradation, aqueous solutions, IR spectroscopy

Abstract: Two new bismaleimides with preforming ester and amide linkages in the main chain were prepared by the reaction between the chloride of 4-maleimidobenzoic acid and 4 (5) amino- salicylic acid. The structures were characterized by elemental analysis, infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy and thermogravimetric analysis. Keywords: bismaleimides, polyimides, thermal stability

Abstract: This paper presents two different procedures for the configuration optimization of a glass fibre reinforced laminate in order to enlarge the load capacity of different structures where these materials could be embedded. By some experimental tests, the authors have established the optimal forming pressure of laminate belonging to a glass fibre fabric reinforced composite. A second experimental aspect taken into account was the determination of the optimal number of laminate, in both situations being attended the obtainment of the highest values for ultimate strengths. The Finite Element Method gives the possibility of a constructive optimization of the composite, the parameters taken into consideration depending on the followed purpose. Keywords: epoxy resin, lamina, finite element method, forming pressure, interlaminar strength

Abstract: The paper investigates the effect of organic phase on yield and inherent viscosity in liquid-vapor interfacial polycondensation and the effect of reaction temperature and reagents molar-ratio on yield, inherent viscosity and molecular weight in liquid-liquid interfacial polycondensation of cyclohexylphosphonic dichloride (CPD) with bisphenol A (BA). A comparative study between liquid-liquid and vapor-liquid interfacial polycondensation of CPD with BA was performed. Keywords: polyphosphonate, interfacial polycondensation, bisphenol A, cyclohexylphosphonic dichloride

Abstract: Waxes are critical to hot melt adhesives performance in terms of thermal stability and mechanical properties. The thermal behavior of EVA with microcrystalline and polyethylene waxes have been investigated by infrared spectroscopy and physical-mechanical testing. Infrared spectroscopy was used to follow the ratio evolution of band intensities E730/E720 with type and content of EVA –wax blends. The tensile properties have been measured at two EVA/wax ratios: initially and after exposure at 175 and 200oC. A significant correlation was found among tensile strength at break / elongation and type and ratio of EVA / wax ratio. Semiquantitative spectral information and evolution of physical – mechanical properties have been used to improve the behavior of EVA hot melt adhesives at work temperature. Keywords: wax, elastomers EVA, thermodegradation, cristallinity

Abstract: Powders of poly (vinyl alcohol) with different degrees of polymerisation and hydrolysis have been reacted with phosphorous acid in homogeneous conditions. The influence of experimental conditions on the substitution degree has been investigated. Analytical, spectral, viscosimetric and thermogravimetric methods were used to analyse the influence of tacticity, crystallinity and degree of polymerisation and hydrolysis of parent poly (vinyl alcohol) on the properties of the phosphorilated products. Keywords: phosphorilated poly (vinyl alcohol), degree of hydrolysis, degree of polymerisation, tacticity

Abstract: Epoxy resins with mezogenic groups were prepared from diglycidyl ether of 4,4`-bisphenol (DGEBP), as rigid block, and 4,4’-diaminodiphenyl sulphone (DDS), as curing agent. A nematic-like structure was developed in time, in the temperature range of the curing process between 151 and 2530C. The mesophase formation was proved using optical microscopy (OM) and wide-angle-X-ray scattering (WAXS) techniques. Keywords: epoxy, mesophase, liquid crystal, curing, network

Abstract: The paper deals with the synthesis and characterisation as plasticizers and/or lubricants of some unsymmetrical diesters of sebacic acid by using superior branched aliphatic alcohols, such as 2-ethyl-hexanol, isodecanol and isotridecanol, along with complex aliphatic-aromatic alcohols, like 2-phenoxyethanol, 2-[(o-sec-butyl)phenoxy]ethanol and 2-[(p-nonyl)phenoxy]ethanol, respectively. Valuable plasticizing and/or lubricating properties were recorded, as a function of the polar / unpolar ratio within each structure of the considered product. A semnificative improved thermal resistance was also observed. In this way, the valability and consistency of the theoretical premises admitted, like the asymmetry and polyfunctionality principles, were fully proved. Keywords: unsymmetrical sebacic diesters, plasticizers, lubricants, phenoxy-ethanols

Abstract: It was studied the influence of urheomelamineformaldehydic resin adds, as flow modifier, on the main characteristics of some epoxi-polyesteric powder dye of white signal type and of cover films made with these. It was established that the introducing in the forming of the uhreomelaminoformaldehydic resin ensures the decrease of the gelification time, the disappearence of needle shots and of craters appearing in the cover film made with the standard dye and the reducing of the orange skin aspect intensity. In order to ensure these positive influences it is necessary to introduce in the forming relatively high ratios (9.1%) of urheomelamino-formaldehydic resin. By also introducing an acrylic flow modifier, the positive influences may be obtained with smaller ratios (~ 3.2%) of urheomelaminoformaldehydic resin. Keywords: adds, main, forming, needle shots, forming

Abstract: The 2,6-di-tert-butylphenol (DtBP) can be oxidated with O2, in the presence of some catalysts based on M(II) complexes with Schiff bases, in DMF. The metal complexes contain Mn and tetradentate Schiff bases derived from salen, as ligands. The transformation degree, the nature and contents of the products obtained were followed by 1H RMN spectroscopy and gas chromatography. Kinetic data indicate that the reaction is of the pseudo-first-order, as compared with dioxygen consumed. Keywords: kinetics, oxidation, Mn(II) Schiff bases complexes

Abstract: New aromatic aldehydes were prepared in the conventional literature manner by Williamson etherification reaction of p-chlorobenzaldehyde with p-substituted phenols, or by esterification reaction of cyanoacetic acid with p-hydroxybenzaldehyde in the presence of dicyclohexylcarbodiimide (DCC). The obtained monomers have been confirmed structurally by IR, 1H-NMR spectroscopy, elemental analysis and characterized by solubility, thermal behavior and refraction index. Keywords: monomer, aromatic aldehyde, mesogenic precursor

Abstract: The main route of obtaining bismaleimides is the reaction between maleic anhydride and primary diamines. First stade occured with forming maleamic acid, then cyclicised to bismaleimide in presence of the acetic anhydride, sodium acetate or other dehydration agents. In the reaction mixture there appeared secondary products as bisisomaleimide, bisacetamide and unreacted bismaleamic acid. A study of their presence and influence on the polyaminobismaleimide resin processability and properties using DSC, ATG and IR methods was performed. Keywords:bismaleimides, secondary products, polyaminobismaleimide

Abstract: The delivery pharmacokinetics of the codeine, which was entrapped in some polymeric matrices, was studied. As matrices, the methyl methacrylate homopolymer and methyl methacrylate copolymers with different percentage of 2, 3 epoxypropyl methacrylate were used. The release profile is correlated with the nature and obtaining manner of the macromolecular structures with and without the presence of a continuous electromagnetic field respectively. Keywords: crosslinked, functionalised copolymers, codeine, drug release, release rate