Iranian polymer journal
Volume:15 Issue: 3, 2006

Acomprehensive study on the linear viscoelastic buckling of Euler-Bernoulli (E-B) and Timoshenko beams is presented. The mathematical formulation for visco elasticE-B beam under combined time variant general axial and transverse loading and for the viscoelastic Timoshenko beam only subjected to time variant general axial loading is developed. Various boundary conditions are defined then clamped edge constraintsare applied. The E-B and Timoshenko cantilever beams are investigated under general axial loading. Both differential and integral forms of the beam governing equations are derived, but only the differential equations are solved, using the finite difference numerical technique assuming Kelvin material model. A computer programme is implemented for computing the beam deflections and a technique is described for obtaining the critical buckling loads. Where possible the finite difference numerical results are compared with other available results. The correlations of the results are extremely well. The important contributing factors are the general nature of the loading and the technique for calculating the critical buckling loads.

Experimental design of Taguchi was used to optimize the irradiation conditions of UHMWPE/PET composite. Four radiation process variables; fibres percentage, radiation type, radiation dose and post irradiation thermal treatment temperature have been considered. According to the variables and levels, the L9 orthogonal array was selected. Analysis of variance on the physico-mechanical properties and gel content of the samples illustrated that among variables, fibre percentage has affected the properties of the composite more than the other variables in a way that with its increase the samples’properties will decrease, therefore zero was considered as an optimum level forfibre percentage. Results indicated that better properties can be achieved by EB-irradiation, compared with γ-irradiation, and the optimum level of radiation dose is 125 kGys. Although post-irradiation thermal treatment temperature affected the sample properties insignificantly but its optimum value was 110oC. The results of this research indicated that irradiation of composite, reduced physical properties, increased the percentage of crystallinity and enhanced the wear resistance. According to the reduced properties of PET fibre’s tensile test, the mechanical properties of irradiated composite diminished. Scanning electron microscopy showed that non-homogeneous dispersion of fibres in the matrix and poor interfacial adhesion between fibres and matrix, caused reduction of composite mechanical properties. FTIR Analysis confirmed that cross-linking and oxidation occurred in composite radiation process.

Mathematical Modelling can lead to a better understanding of the role of variables in real dyeing process. The aim of this study was to model colour yield in dyeing cotton cloth with selected reactive dyes via two phase pad-steam fixation method, as a function of steam temperature, steaming time and alkali concentration. Factorial design was employed and at first, polynomial regression models were produced for the selected monochlorotriazine, dichlorotriazine, trichloropyrimidine and vinylsulphone reactive dyes. As these models did not meet the necessary requirements, orthogonal polynomial regression was employed. This led to the acceptable models except in one case. The models for the selected dyes in each group of monochlorotriazine, dichlorotriazine, trichloropyrimidine showed similarity but not for vinylsulphone dyes. Response surfaces of the models can be used to find the optimum conditions that maximize the colour yield of each dye.

The polymeric ligand poly[(2,4-dihydroxy benzophenone)butylene] H(DHBP-BD) forms 1:2 metal-ligand complexes with Ni(II), Co(II), Cu(II) and Zn(II). The polymeric ligand and its polychelates were characterized on the basis of elemental analyses, magnetic susceptibilities, IR-spectroscopy, UV-visible spectra, NMR, thermogravimetric analyses. The molecular weight of resin was determined using number average molecular weight (Mn) by vapour pressure osmometry (VPO) method. The stereochemistry in case of the Cu(II) polychelate is square-planar, tetrahedral for Zn(II) and octahedral for Ni(II) and Co(II). The stereochemistry in each chelate is proposed on the basis of magnetic susceptibilities and electronic spectra. The IR spectra show that the bidentate ligand coordinates through the oxygen atom of the carbonyl and phenolic group with replacement of hydrogen by metal ions, respectively. All the chelates are paramagnetic in nature except the Zn(II) chelate which is diamagnetic. The ion-exchange study of the prepared resin was checked by batch equilibration method with selected metal ions [Cu(II), Ni(II), Fe(III) and UO2 2+(VI)] at varying electrolyte concentration, pH and time. It is found that, resin can be used as an ion-exchanger.

Compatibilizer is used for improvement of interfacial interaction, mechanical properties and processability of polymer blends. In this study, the effect of phthalic anhydride (PAH), succinic anhydride (SAH) and maleic anhydride (MAH) in vulcanizable compositions of the melt mixed acrylonitrile butadiene rubber/poly(vinyl chloride) (NBR/PVC) in different proportions were investigated. PAH, SAH and MAH were used to improve compatibility of NBR/PVC blends. These additives increased the interfacial interaction between NBR and PVC phases confirmed by the scanning electron microscopy (SEM) study of fracture surfaces. The results were compared to those for control type (no compatibilizer added) NBR/PVC formulation. The developed compositions were studied by rheometric and mechanical properties. Also, in this work, we investigate the effects of mixing procedure (Brabender Plasticorder and Haake rheometer) and NBR form (powder and bale) on the final properties of NBR/PVC blends. It is argued that NBR/PVC blends with NBR powder prepared in the Haake rheometer have higher stabilization torque and tensile properties than NBR/PVC blends with NBR bale and have lower properties than the blends which were prepared in Brabender Plasticorder with NBR powder. It is observed that the increasing effect of NBR powder in mechanical properties is owing to fine particle size and high surface area that are well interacted with PVC.

Ionic liquids (IL)s are a new class of solvents which have interesting properties such as nonvolatility, high ionic concentration, good thermal stability, nonflammability and candissolve most of organic as well as inorganic materials. Recently ILs are attracting more attention due to their significant role in controlling the reaction as a catalyst. It is important that ILs are the chemicals that can be applied as solvents and catalysts in green chemistry processes. In this investigation high molecular weight and optically active poly(amide-imide)s (PAIs) have been synthesized and their properties such as optical activity, solubility, thermal stability were studied. Polymers were synthesized by direct polymerization of N,N’-(4,4’-hexafluoroisopropylidenediphthaloyl)-bis-L-methionine and various aromatic diamines in the presence of triphenyl phosphite by a new microwave assisted ionic liquid (MAIL) method. The compounds obtained were characterizedby elemental C, H and N analysis, solubility, FTIR, 1H NMR. Thermogravimetric curves were also recorded. All data agree with the proposed structures.

4-Chloromethyl styrene (CMS) was copolymerized with different monomers such as 2-ethyl hexyl acrylate (EHA), 1,1-dichloroethylene (DCE), N-viny1-2-pyrrolidone (NVP) acrylonitrile (AN) and methacrylonitrile (MAN) by free radical polymerization method at 70±1oC using α,α’-azobisisobutyronitrile (AIBN) as an initiator and the copolymers (I-V) collected respectively. The copolymer compositions were obtained using related 1H NMR spectra and the polydispersity of the copolymers was determined using gel permeation chromatography (GPC). Highly sterically hindered tris (trimethylsilyl)methyl (Tsi=trisyl) substituents were then covalently linked to the I, II and III copolymers. When copolymers IV and V are treated with TsiLi, cross-linking is observed and no further modification is possible. Differential scanning calorimetry (DSC) showed that incorporation of Tsi substituents in the side chains of copolymers increases the rigidity of the polymersand subsequently, their glass transition temperatures. All the resulted polymers werecharacterized by FTIR and 1H NMR spectroscopic techniques.

Conducting polymers have been widely investigated for both academic and industrial purposes over two decades. Polyaniline (PANI), a member of the intrinsically conducting polymer family was blended with Nylon 6 in concentrated formic acid. Conducting fibres were spun from the blend solution by wet spinning method. In this process the solvent is replaced by non-solvent and consequently the polymer is precipitated. Qualitative studies were carried out on the effect of coagulation bath. Coagulation bath containing 7.5% w/w Li2SO4 has improved mechanical properties of the fibres. The electrical resistance of fibres containing 5-25% w/w of PANI, varies between 0.665 to 0.015 MΩ.cm-1. It was found that the electrical resistance of fibres depends on their moisture content. Cyclic voltammetric studies were carried out in -350 to 1000 mV vs.Ag/AgCl. These studies showed that PANI/nylon 6 fibres were electroactive. Further more fibre containing 25% w/w of PANI has high electroactivity stability.

Electrospinning is a simple, economical and straightforward method of production of various nanostructures. Electrospun nanofibres have a wide range of potential applications in many fields, such as air filtration, water filtration, biomedicine, catalyst supports, drug delivery, tissue engineering, nanowires, just say few. This experiment shows that operating parameters affect much morphology and mechanical character of electrospun nanofibres. This paper studies theoretically and experimentally the scaling relationship between two main operating parameters-current and applied voltage. Polyacrylonitrile (PAN) nanofibres are prepared by electrospinning of 12 wt% and 18 wt% PAN/DMF solution. In our experiment the volume flow rate keeps unchanged during the electrospinning process, and the voltage varies from 10 kV to 50 kV. The non-linear relationship between current and applied voltage is obtained by an allometrical approach.The theoretical prediction agrees very well with experimental data.