Iranian Journal of Polymer Science and Technology
Year:2011 | Volume:24 | Issue:4 (ISSUE NUMBER 114)|Papers Count:6

Fiber reinforced composites are widely used instead of traditional materials in various technological applications. Therefore, by considering the extensive applications of these materials, a proper knowledge of their impact behavior (from low- to high-velocity) as well as their static behavior is necessary. In order to study the effects of strain rates on the behavior of these materials, special testing machines are needed. Most of the research efforts in this field are focused on application of real loading and gripping boundary conditions on the testing specimens. In this paper, a detailed review of different types of impact testing techniques and the strain rate dependence of mechanical and strength properties of polymer composite materials are presented. In this respect, an attempt is made to present and summarize the methods of impact tests and the strain rate effects on the tensile, compressive, shear and bending properties of the fiber-reinforced polymer composite materials. Moreover, a classification of the state-of-the-art of the testing techniques to characterize composite material properties in a wide range of strain rates are also given.

Residual lgnin of wood after MWL isolation was dissolved with 1-butyl-3-methylimidazolium chloride ionic liquid. Chemical structure of isolated MWL from poplar wood (Popolus deltiodes) and dissolved residual lignin were characterized with gas chromatography and ID, 2D NMR techniques. Analytical results showed that Popolus delta ides wood has more 4- (3-hydroxy-1-propenyl) -2-methoxyphenol units (Guayacil lignin) than 4- (3-hydroxy-1-propenyl) -2, 6-dimethoxy phenol units (Syringyl moieties). In addition to Guayacil and Syringyl, the extracted ligin is composed of a small amount of p-benzyl alcohol. The residual lignin is mainly composed of condensed structures which are often of carbohydrate complexes. The lignin structural ratios of dissolved wood in ionic liquid are the same as those of dioxan extracted lignin. Anomeric HSQC analysis of lignin showed that the lignin-carbohydrate complex is composed of cellulose, xylan, mannan and arabinan sugars. Side-chain region of lignin structure is mainly composed of β-O-4, phenylcoumaran, resinol and spirodienone moieties.

Synthetic water soluble acrylamide-based polymers have wide range of applications in the field of soil establishment and non-desertification. In this research, the acrylamide-based anionic polyelectrolytes were prepared by solution polymerization. The polymerization was carried out using AIBN as a radical initiator and at different degrees of anionic charges ranging between 10% and 30% using sodium hydroxide as hydrolyzing agents. The chemical structure of the synthetic polymers was studied and confirmed by FTIR technique. The charge density on polymer backbone was determined by titration method. The rheological behavior of polymer solutions was evaluated by Brookfield viscometer. The results show that the viscosity decreases with increasing the shear rate of solutions. Molecular weights of samples were measured by laser light scattering analyzer. The morphology of the polymer was studied by SEM and the EDX was used for elemental analysis determination. The anionic polymers with 10-30% negative charges were mixed with clay in order to evaluate the soil establishment. The results show that an anionic polyelectrolyte can make soil particles more cohesive and improve soil physical properties.

Alinear low density polyethylene (LLDPE) production process, including two- fluidized bed reactors in series (FBRS) and other process equipment, was completely simulated by Aspen Polymer Plus software. Fluidized bed reactors were considered as continuous stirred tank reactors (CSTR consisted of polymer and gas phases). POLY-SRK and NRTL-RK equations of state were used to describe polymer and non-polymer streams, respectively. In this simulation, a kinetic model, based on a double active site heterogeneous Ziegler-Natta catalyst was used for simulation of LLDPE process consisting of two FBRS. Simulator using this model has the capability to predict a number of principal characteristics of LLDPE such as melt flow index (MFI), density, polydispersity index, numerical and weight average molecular weights (Mn, Mw) and copolymer molar fraction (SFRAC). The results of the simulation were compared with industrial plant data and a good agreement was observed between the predicted model and plant data. The simulation results show the relative error of about 0.59% for prediction of polymer mass flow and 2.67% and 0.04% for prediction of product MFI and density, respectively.

The present work reports and discusses the results of a 3D simulation of the injection molding process of a rubber compound that includes the mold filling stage and material curing, using the computer code is developed in "UDF" part of the Fluent 6.3 CAE software. The data obtained from a rheometer (MDR 2000) is used to characterize the rubber material in order to find the cure model parameters which exist in curing model. Because of non-newtonian behavior of rubber, in this work the non-newtonian model for viscosity was used and viscosity parameters were computed by mean of viscometry test by RPA. After calculation of the physical and curing properties, vulcanization process was simulated for a complex rubber article with non-uniform thickness by solving the continuity, momentum, energy and curing process equations. Predicted filling and curing time in a complex and 3D rubber part is compared with experimentally measured data which confirmed the accuracy and applicability of the method.

This research work is devoted to the investigation on the use of silica on the fatigue-to-failure property of a tire tread compound. A reference compound was first designed in which 60phr carbon black was used as the reinforcing filler. While keeping the total of filler content to be constant as 60phr, three additional compounds with 5, 10 and 20phr silica were then manufactured. The classical static and dynamic tests were carried out on appropriate samples made from these compounds to determine tensile strength, hardness, abrasion resistance, fatigue-to-failure, dynamical-mechanical properties and temperature rise due to heat build-up. The results showed that by replacing part of carbon black with equivalent amount of silica, a major increase in fatigue resistance is obtained to the point that 20phr silica has the most significant effect when subsituting 5 and 10phr silica. The DMTA analyses revealed that the best compromise between fatigue properties, rolling resistance and wet/ice traction can be achieved at 5 to 10 phr silica substitution.