Iranian polymer journal
Volume:19 Issue: 3, 2010

An experimental apparatus has been developed for observing interfacial stabilityand deformation of multilayer pressure driven channel flows. The interfaceinstability of a co-extrusion flow of polyethylene and polypropylene is studiedexperimentally in a slit geometry. This is performed by introducing disturbances ofcontrolled wavelength and amplitude on three-layer symmetric (A-B-A) polymer meltsand followed by a series of extrudate mechanical testing. In this study variations ofmechanical properties as well as wave interlocking have been related to the conformationof the interfacial waves. By investigating the growth of interfacial waves andtensile stress of extrudate samples, a relationship between interfacial instability andmechanical properties of polypropylene (PP) and high density polyethylene (HDPE)systems has been established. It is shown that instabilities are associated withinterfacial waves, and it turns out that its amplitude is known as a mechanism forcontrolling the strength of three-layer polymer products. It is also demonstrated that themechanism of interfacial strength is related to interfacial instabilities as well as theinterfacial wave interlocking. By considering that the instability is controlled by modalwave it may be possible to forecast the quality of final products in the co-extrusionprocess.

Copolymer resins (p-COF) synthesized by the condensation of p-cresol andoxamide with formaldehyde in the presence of acid catalyst, were proved to beselective chelation ion-exchange copolymers for certain metals. The chelatingion-exchange properties of these copolymers were studied for Fe(III), Cu(II), Ni(II),Co(II), Zn(II), Cd(II) and Pb(II) ions in the form of their metal nitrate solutions. A batchequilibrium method was employed in the study of the selectivity of metal ion uptakeinvolving the measurements of the distribution of a given metal ion between the copolymersample and a solution containing the metal ion. The study was carried out over awide pH range, shaking time and in media of various ionic strengths of differentelectrolytes. The copolymer showed a higher selectivity for Fe(III), Cu(II) and Ni(II) ionsthan for Co(II), Zn(II), Cd(II) and Pb(II) ions. Distribution ratios (D) of metal ions werefound to be increased by increasing pH of the solutions; hence the resin can be usedto recover certain metal ions from waste solutions and used for the purpose ofpurification of waste water and removal of iron from boiler water. The ion-exchangecapacity of metal ions has also been determined experimentally and compared withother commercial resins. Besides ion-exchange properties, the copolymer resins werealso characterized by viscometric measurements in dimethyl sulphoxide (DMSO), UVvisibleabsorption spectra in non-aqueous medium, infra-red spectra and nuclearmagnetic resonance spectra. The physico-chemical and spectral methods were usedto elucidate the structures of p-COF resins. The morphology of the copolymers wasstudied by scanning electron microscopy, showing amorphous nature of the resinstherefore can be used as a selective ion-exchanger for certain metal ions.

To improve the toughness of epoxy resin, and clarify the complex interrelationshipbetween the miscibility, morphology, toughness and composition of epoxyresin/graft copolymer blends, amphiphilic polysiloxane graft copolymers(F6-PMSs) with different contents of polyether were synthesized via hydrosilylationbetween epoxy-immiscible poly(methylhydrosiloxane) and epoxy-miscible allylpolyoxyethylene polyoxypropylene ether (F6) to modify diglycidyl ether of bisphenol A(DGEBA). The miscibility of amphiphilic graft copolymers with epoxy resin wasinvestigated by observing the transparency of the modified epoxies before and aftercuring and by detecting the glass transition temperature (Tg) of the cured epoxies usingdifferential scanning calorimetry. The morphologies of the cured epoxies were studiedby scanning electron microscopy, and the toughness in terms of tensile and impactstrength were examined by tensile and impact testing. Results indicated to highermiscibility of polysiloxane with DGEBA by grafting with polyether. Relative to the neatepoxy network, the polysiloxane modified epoxies exhibited lower Tgs and with theincreased polyether in graft copolymer, there was a decreasing trend noticed in Tg. Thenanostructures were obtained for the modified epoxies with different F6 to PMS ratios(5 wt% of DGEBA). The formation of the nanostructures in the thermosettingcomposites was judged by following the self-assembly and reaction-inducedmechanisms, mainly dependent on the miscibility of graft copolymer with epoxy resin.Moreover, toughness of the epoxy networks was greatly improved by F6-PMS of100/100 weight ratio at relatively low addition levels.

Post-consumer waste polymers are considered as environmental pollutants thatshould be reused as inexpensive materials. Also, there are resources of naturalbitumen in several regions of Iran that can be used to modify bitumen. Thepurpose of this study is to investigate the possibility of obtaining penetration grademodified bitumen from vacuum bottom residue (VB) by adding various recycled wastepolymers and non-polymer materials without air blowing VB. Following this concept,natural bitumen (NB), recycled waste polyethylene (PE), recycled waste latex, crumprubber modifier (CRM) and heavy vacuum slopes (HVS) were used. The formulation ofmixing blends was determined by experimental design method using design-expertV.7.16 software. It was found that 40/50, 60/70 and 85/100 grades of penetrationbitumen with improved performance grades, 82-40, 70-40 and 70-40, respectively, areproducible using these materials, although, decreased ductility is observed almost forall the blends. A combination of 10% natural bitumen and 5% recycled latex with VB areconsidered as the best blend amongst all blends. The resulting modified 60/70 gradebitumen shows improved complex modulus in comparison with neat 60/70 bitumen andconsequently it has increased resistance against permanent deformation (rutting). Also,the lowered Frass breaking point of this blend (-21°C) improved its low temperatureperformance (PG = 70-40). Unfortunately, when the crump rubber modifier particles arenot well-dispersed and fine enough in bitumen matrix, there is an unexpecteddecreased ductility occurred in the blends.

The surface modification of ground tyre rubber (GTR) containing hydroxyl groupswas carried out by atom transfer radical polymerization using a two-step reactionprocedure. The process consisted of immobilization of an ATRP initiator such as2-bromoisobutyryl bromide and controllable radical polymerization of maleic anhydride(MAH). The resulting GTR-g-MAH was characterized by Fourier transform infraredspectroscopy and X-ray photoelectron spectroscopy. The results demonstrated that thegraft yield of new polymer could reach 69.4% on GTR surface. Then the grafted GTRwas used as an adsorbent for removal of lead ions from aqueous solution. It wasobserved that factors such as solution pH, contact time, initial lead concentration andgraft yield exerted considerable influence on lead adsorption capacity of GTR-g-MAH.The adsorption process indicated that the pseudo-second-order kinetic model fitted theexperimental data well, and the equilibrium of adsorption could be described byFreundlich isotherm model. The maximum adsorption capacity of GTR-g-MAHcalculated from Langmuir isotherm reached 144 mg.g-1. It was found that theGTR-g-MAH particles had significantly greater adsorption capacity and fasteradsorption kinetics for lead adsorption than unmodified GTR particles.

New UV-curable di-functional naphthyl epoxy acrylates (DNEA) and multifunctionalnaphthyl epoxy acrylates (MNEA) were synthesized from naphthylepoxy, acrylic acid, and hydroquinone as an inhibitor, and N,N´-dimethylbenzylamine(DMBA) as a catalyst. Different UV-curable liquid compositions were developedwith naphthyl epoxy acrylates, different reactive diluents, active amine monomer and1-hydroxycyclohexylphenyl ketone (Irgacure 184) as a photoinitiator. Thin films wereprepared by curing these composite solutions using a high pressure mercury lamp. Thechange of double bond absorption band was identified by Fourier transform infraredspectra during the UV-curing process. Gel content, water absorption, the pendulumhardness, mechanical properties (static and dynamic) and thermal characterizations ofthe UV-cured films were investigated. The characteristic C=C absorption of theunsaturated acrylic groups at 1635 cm-1 gradually disappeared with UV-cured time andwas no longer detectable after irradiation for 10 s. The gel content and the pendulumhardness increased with increasing irradiation time, and these gradually turned toconstant values with increasing the irradiation time as the degree of polymerizationreached its saturation. With the increase of mono-functional reactive diluents butylacrylate in the compositions, the gel content, the pendulum hardness and mechanicalproperties of UV-cured films decreased, except for the water absorption. It was foundthat the glass transition temperature and the storage modulus of MNEA compositionswere higher than those of DNEA compositions by the dynamic mechanicalmeasurements, and the glass transition temperature of MNEA compositions was142°C. The thermogravimetric analysis of UV-cured films revealed that films preparedfrom naphthyl epoxy acrylates exhibited excellent thermal stability.

Anionic ring-opening polymerization of ε-caprolactam leads to the formation ofpolyamide 6 (PA6). This reaction takes place at a significantly faster reaction rateand gives a narrower molecular weight distribution than the other techniques.Due to this advantage, anionic polymerization of ε-caprolactam towards PA6 in meltblending was investigated in this work. PA6 was prepared in an internal mixer via meltpolymerization of ε-caprolactam as a monomer with sodium caprolactam as its catalystand hexamethylene diisocyanate as an activator. The effects of various concentrationsof catalyst and activator on the initiation time of the reaction and on the residualmonomer were determined. The residual monomer was collected using a solventextraction method and determined by GC-mass technique. The physical andmechanical properties of the PA6 prepared via melt blending and of a commercial PA6prepared were determined by differential scanning calorimetry (DSC), thermalgravimetric analysis (TGA), tensile and impact tests. The experimental results showedthat addition of 3% catalyst and 3% activator to the formulation gave the bestproperties. These conditions led to the lowest residual monomer and bettermechanical properties as well. The other novel aspect of this investigation was theformation of nanofibril during melt polymerization of ε-caprolactam. Mechanicalproperties showed that the PA6 prepared by using this technique and theabove formulation were similar to the PA6 commercial grade.