Iranian Polymer Journal
Year:2006 | Volume:15 | Issue:8 (74)|Papers Count:7

4-(1-Naphthyl)-1,2,4-triazolidine-3,5-dione (4-NTD) was prepared from 4-naphthyl isocyanate. The compound 4-NTD was reacted with excess acetyl chloride in N,Ndimethylacetamide (DMAc) solution and gave 1,2-bis-acetyl-[4-(1-naphthyl)]-1,2,4- triazolidine-3,5-dione as a model compound. Solution polycondensation reactions of monomer with succinyl chloride, suberoyl chloride and sebacoyl chloride were performed under conventional solution polymerization conditions in the presence of different catalysts such as pyridine (Py) and triethylamine (TEA) in DMAc and N-methylpyrrolidone (NMP) which led to the formation of novel aliphatic polyamides. These novel polyamides have inherent viscosities in a range of 0.04-0.46 dL/g in N,N-dimethylformamide (DMF) at 25oC. The resulted polymers were characterized by FTIR, 1H NMR, UV-vis and TGA analyses techniques. The flurescence excitation and emission spectra were also studied.

This paper describes the characteristics of polypropylene-straw fibres composite interfaces. Surface chemical modification of straw fibres was carried out by poly (methyl hydrogen siloxane) (PMHS) to enhance compatibilization. Dried straw fibres were grafted with PMHS and then melt blended with polypropylene. All treatments even at low degrees of grafting significantly changed the hydrophilic nature of the straw fibres surfaces to hydrophobic one and improved the wetability of the straw fibres by the matrix which lead to improved adhesion. The rheological and morphological properties of composite were studied and results show that at low loadings, the viscosity of the treated straw fibres composite is reduced because of low molecular weight of PHMS. Water absorption of treated and untreated straw fibres was studied and results indicated the enhanced improvement in hydrophobic nature of treated fibres. Untreated and treated straw fibres with different amount of coating were floated on water for 2 h, results show that the water absorption is minimum in straws treated with 2 wt% of each PMHS and catalyst.

According to the crystallization conditions, polypropylene (PP) can be crystallized into three forms: a-monoclinic, b-hexagonal, and g-form. The major problem with thermoforming of PP is its narrow processing window. Due to broadening the melting region, b -crystal form has a significant effect on the thermoformability of PP. In this study  g- quinacridone (Q-dye) was used as a b-nucleator agent. Three different concentrations of Q- dye (5, 10, and 50 ppm) were mixed separately with PP by a laboratory twin screw extruder. X-ray graphs confirmed the β-nucleating effect of Q-dye obviously. Differential scanning calorimetry (DSC) was used for evaluating of the crystallization behaviour. Both melting points of a- and b- crystals were seen in the samples containing Q-dye. Crystallization temperature and the rate and degree of crystallinity increase with b-nucleator concentration. Sagging tests were carried out at 170°C and it was observed that sag distance and sagging rate decreased with increasing Q-dye content.

Polymer composites based on modified montmorillonite (OMMT) and polystyrene (PS) were prepared with different compositions by melt processing. The pristine montmorillonite (MMT) was obtained from Algerian plant with a cation exchange capacity (CEC) of 119 meq/100 g. The modification of MMT was carried out by treating with octadecylammonium cation. The polymer composites were characterized using different techniques such as X-ray diffraction (XRD), infrared spectrophotometery (IR), differential scanning calorimetery (DSC), thermal gravimetric analysis (TGA), and rheology and tensile measurements. The results were showed that, the basal space of the silicate layer increased, as determined by XRD, from 12.6 to 32.3 A. The microstructure was detected by X-ray patterns and transmission electronic microscopy (TEM) at 2 wt% OMMT, however, higher than 2 wt% OMMT reveals partial intercalation structure. The composite with 5 wt% was indicated the greatest improvement in thermal stability. The rheological properties of the PS/OMMT composites were investigated using ARES-rheometer operated in the dynamic mode with a parallel plate geometry. The storage and loss moduli were increased with increasing the clay content. The stress-at-break is also improved relatively compared to the virgin polystyrene in our experimental conditions.

Simulation models play a key role in development and operation of polymerization processes. The objective of this work is the simulation of polymerization process of high-density polyethylene (HDPE) in slurry phase using Ziegler-Natta catalyst at industrial scale. Since Ziegler-Natta catalysts produce polyolefins with wide molecular weight and copolymer composition distributions, a multi-site type catalyst model was used for simulating the polymerization process. By deconvoluting the GPC graph of a specimen from the first reactor it was found that at least 5-6 site types should be considered within the catalyst for simulating the wide molecular weight distribution of produced polymer. In our methodology for optimizing the kinetic parameters, the deconvolution of the GPC graph of only the first reactor was used. Six catalyst sites were considered for this purpose and a set of kinetic parameters was proposed for this number of active sites. Results from the simulation showed that the model is able to predict the industrial data e.g., average molecular weight, molecular weight distribution, production rate, and residence time of polymer product. By using the model, the effects of changing hydrogen, monomer, comonomer, and also impurities flow rates were investigated on polymerization rate, mass average molecular weight, and molecular weight distribution.

This paper addresses the finite element modelling of a steel belted radial tyre under static contact load using ABAQUS code. The model combines the 3D parts of the complex tread patterns and the quasi axisymmetric part of the tyre in which the tread blocks are not included. These two sections were meshed separately and linked together using a tying algorithm implemented in the code. The fibber reinforced parts of the tyre including ply, belts, and cap ply were modelled using rebar layer embedded in the surface elements. A hyperelastic material model was used in conjunction with a linear elastic one to describe the stress-strain behaviour of rubber and reinforcing fibres, respectively. The developed model was used to simulate the 175/70R14 steel-belted radial tyre subjected to inflation and contact loads. Three belts angles were selected to examine the effect of belt angle variations on the mechanical behaviour of the tyre. In addition, the results were also compared with a similar tyre model in which a simply ribbed tread was used instead of complex tread pattern. The friction between tread surface and contact road surface was simulated using the Coulomb’s friction law. The numerical results and also the comparison of experimentally measured tyre deflection under concentrated vertical load revealed that neglecting the details of the tread blocks has very minor effect on the predicted tyre deformation. However, differences can be large enough when considering secondary or higher variables such as contact pressure, stress, and strain energies. It is also shown that a belt angle of 20o is the best comprised value among the selected design parameters.

A proposed method to overcome the donor-recipient blood group incompatibility is to mask the blood group antigens by the covalent attachment of poly (ethylene glycol) (PEG) to the red blood cell (RBC) membrane. Despite much work in the development of PEG-coating of RBCs, there is a paucity of data on the optimization of the PEG-coating technique by using low molecular weight polymers. It is the aim of this study to determine the optimum conditions for PEG-coating using a cyanuric chloride reactive methoxy-PEG derivative as a model polymer. Activated PEG of 2 kDa molecular mass was covalently attached to human RBCs under various reaction conditions. Inhibition of binding of a blood-type specific antiserum (anti-D) was employed to evaluate the effect of the PEG-coating, quantified by flow cytometry. RBC morphology was examined by scanning electron microscopy (SEM). Statistical analysis of experimental design together with SEM results showed that the optimum PEGylation conditions are: temperature 140C, reaction time 20 min, and concentration of reactive PEG 10 mg/mL.