Sharif Digital Repository

The fracture mechanism of hybrid iPP-EPR-GF composites has been studied by notched Charpy, three- and four-point bending fracture tests. The results of impact tests illustrate that increasing both temperature and EPR/GF ratio increases the impact energy of iPP-EPR-GF. Indeed, with increasing temperature, a brittle, ductile, transition temperature (BDTT) occurs. The results of a three-point bending test show that fracture toughness (KIC) can be improved by addition of both GF and EPR. Since the trend in the fracture toughness values is close to what would be expected by the rule of blends, it can be concluded that the use of both GF and EPR has no significant synergistic effect on toughening.... 

A great amount of work has been done over the past few years to understand the structure-properties relationship in polypropylene/glass fiber composites. This is because of the very fast-growing rate of polypropylene applications in the automotive and other industries. This work focused on the role of glass fibers and fiber-matrix adhesion on deformation mechanism. Composites with different fiber content, with and without adhesion promoter, were fabricated. Tensile tests and microscopy techniques were conducted. Based on the results, a physical model has been proposed that illustrates the initiation and growth of the damage under static loading condition. According to this work, the... 

The fracture mechanism of isotactic polypropylene has been studied by three- and four-point bending tests. The result of three-point bending test shows that a wide spread damage zone is present in front of the notch. Looking in more detail via cross-polarised light shows the evidence of birefringence in the stress-whitened zone. Increasing the applied load causes it to spread out the stress-whitened zone. Then the craze-like features are nucleated inside the stress-whitened region. The result of four-point bending test shows that craze-like damage appears in front of pre-crack and its propagation is dictated by spherulite microstructure. © 2003 Elsevier Science Ltd. All rights reserved  

The main goal of this study is to further understanding of the role of rubber particles on deformation mechanisms in PP/EPR blend. For doing this standard tensile specimens were produced using injection molding. The results of microscopic evaluation of tensile specimen after some stretching show that damage forms in some points and then propagates in different directions. Also some elongated voids are observed, those are probably formed due to cavitation of rubber particles or debonding at the interface. With regard to achieved micrographs one may conclude that the deformation mechanism in PP/EPR blend can be massive dilatational shear banding due to repeated cavitation. © 2003 Elsevier Ltd.... 

A polypropylene (PP) sheet was successfully applied as an extracting medium for trace enrichment of fluoxetine (FLX) from urine samples, followed by high performance liquid chromatography-fluorescence detection (HPLC-FD). The extraction medium was a square, 1 × 1 cm2 piece of polypropylene membrane sheet that was conditioned in methanol. The extraction process was conveniently carried out using a 5 mL urine sample. After extraction, the PP sheet was withdrawn and transferred to a glass vial for performing the desorption process using 210 μL organic solvent. After complete drying, the residue was dissolved in 50 μL of methanol and an aliquot of 20 μL was, finally, injected into the HPLC... 

Long-chain branches are incorporated into the molecular backbone of a polypropylene (PP) in a foaming process. The branching of PP occurs by radical reactions of dicumyl peroxide and a tri-functional monomer, trimethylol propane trimethacrylate. Use of peroxide without tri-functional monomer results in scission of PP molecular chains and significant reduction in melt viscosity. The increase in melt viscosity in conjunction with the flow ability of the modified PP indicates that the polymer has a branched structure. Melting temperature of PP remains unchanged with branching reactions implying that reactions occur mainly in amorphous regions of PP. The improvement in melt strength and... 

In this study, effect of MAPE (maleic anhydride polyethylene) as the compatibilizer on the mechanical properties of wood-flour polyethylene composites has been investigated by using Dynamic Mechanical Analysis (DMA). Composites were made at 25% and 50% by weight fiber contents and 1% and 2% compatibilizer respectively. Controls were also made at the same fiber contents without the compatibilizer. Static mechanical tests including tensile and bending tests were performed. Temperature scans in the range of- 110 to +100°C was also conducted. Results indicated improvements in the mechanical properties due to the compatibilizer addition. Storage modulus values were higher in the case of coupled... 

In last decades, rubber-toughened polymer blends have been the object of considerable interest by many investigators, owing to their attractive mechanical as well as physical properties. Polypropylene (PP) is a type of polyolefin which can be toughened using rubber particles. In another paper [J. Appl. Polym. Sci., submitted for publication], the role of ethylene-propylene (EPR) particles on the deformation mechanism during tensile tests and the fracture mechanism under quasi-static loading tests has been investigated. This paper is instead focused on the role of EPR particles on the fracture mechanism under dynamic loading (impact properties) of EPR/PP blends. Blends with different weight... 

A heat transfer rate was determined for polypropylene tubes in solar water heaters for the Reynolds number range 800-5600. Experiments were conducted in ambient temperatures of 34 to 37°C. Data were correlated in the form of Nusselt numbers as: Nu=0.0015 Re0.75 Pr1/3 with correlation coefficient of 0.95. Such data can be used to predict heat transfer rates in a polypropylene solar heater in Tehran where the experiments were performed. An application of the results is shown in an example. © 2003 Elsevier Ltd. All rights reserved  

Effects of pozzolans and fibers on mechanical properties of RCC are addressed. The mechanical properties were evaluated using optimum moisture with different amounts of pozzolans, steel and polypropylene fibers. Using pozzolans, maximum increase in compressive strength was observed to occur between 28 and 90 days of age, rupture modulus was found to decrease; but toughness indices did not change considerably. The influence of steel fibers on compressive strength was often more significant than that of PP fibers; but neither steel nor PP fibers did contribute to increase in the rupture modulus independently from pozzolans. Also, the toughness indices increased when steel fibers were used  

Joining feasibility of aluminium alloy to polypropylene sheets via friction stir lap joining was examined. Effects of heat-input on microstructure and mechanical behaviour of the joints were investigated. A covering plate was used to confine flow of molten polymer. The results showed a distinctive interaction layer at polymer/aluminium interface, consisted mainly of C, O and Al. Shear strength of the joints decreased by enhancement of the heat-input due to increase in the thickness of the interaction layer as well as the gap width between this layer and both aluminium and polymer matrices. Maximum shear-tensile strength of 5.1MPa (∼20% of polymer shear strength) was obtained, which was... 

The effect of an impact polypropylene copolymer (IPC) having excellent stiffness–toughness balance on the microstructure and properties of a blend comprising 80 wt% recycled high density polyethylene (rHDPE) and 20 wt% recycled isotactic polypropylene (rPP) was studied. Morphological observations revealed improved interfacial interactions, a finer dispersion state and a more homogeneous phase morphology upon IPC incorporation into the blend up to 20 wt%. Flexural modulus, flexural strength, tensile strength and tensile ductility were steadily increased with IPC loading, and exhibited 13%, 14%, 35% and 520% improvement at 20 wt% IPC. A monotonic rise in Izod impact energy, accompanied by a... 

This paper has described a method to obtain the molecular weight distribution (MWD) of polymeric materials from their rheological data. The method has been developed for linear polymers with log normal molecular weight distribution. The rheological data required to obtain the molecular weight distribution are the shear storage modulus,G' (ω), and shear loss modulus,G' (ω) , extending from the terminal zone to the plateau region. For determining the molecular weight average, the method uses the relationship between stress moduli and relaxation spectrums, with the equation that connects dynamic rheological data with molecular weight distribution, and so it is not necessary to achieve the... 

In this study, homo- and co-polypropylene were modified by nanometric calcium carbonate and the effect of additive on scratch resistance was evaluated. Results of this study show that the length of scratch curvature can be considered as an acceptable criterion to evaluate the scratch resistance of polymers. Also, it was found that addition of calcium carbonate to homo-polypropylene increases scratch resistance of this polymer, but its effect on co-polypropylene is insignificant. Based on the results of this work, one may claim that incorporation of nanometric particles with good adhesion to the matrix and well dispersion might be effective in enhancement of scratch resistance. Formation of... 

Polymer films possess excellent optical properties, such as high transparency, and thermal characteristics, like low heat conductivity, as well as further polymer specific advantages. Consequently, polymer films have an outstanding potential for many solar applications. They are already used for encapsulation of photovoltaic (PV) cells, as convection barrier in solar collectors and as substrate or adhesive layers for glazing. In translucent polymers, energy can be transferred internally by radiation in addition to conduction. Since radiant propagation is very rapid, it can provide energy within the layer more quickly than diffusion by heat conduction. Thus, the transient thermal response of...