Mechanical Behavior Of Polypropylene Research Articles

Triaxiality and Plastic-Strain-Dependent Proposed PEAK Parameter for Predicting Crack Formation in Polypropylene Polymer Reservoir Subjected to Pressure Load.

This article raises the topic of the critical examination of polypropylene, a key polymeric material, and its extensive application within the automotive industry, particularly focusing on the manufacturing of brake fluid reservoirs. This study aims to enhance the understanding of polypropylene's behavior under mechanical stresses through a series of laboratory destruction tests and numerical simulations, emphasizing the finite element method (FEM). A novel aspect of this research is the introduction of the PEAK parameter, a groundbreaking approach designed to assess the material's resilience against varying states of strain, known as triaxiality. This parameter facilitates the identification of critical areas prone to crack initiation, thereby enabling the optimization of component design with a minimized safety margin, which is crucial for cost-effective production. The methodology involves conducting burst tests to locate crack initiation sites, followed by FEM simulations to determine the PEAK threshold value for the Sabic 83MF10 polypropylene material. The study successfully validates the predictive capability of the PEAK parameter, demonstrating a high correlation between simulated results and actual laboratory tests. This validation underscores the potential of the PEAK parameter as a predictive tool for enhancing the reliability and safety of polypropylene automotive components. The research presented in this article contributes significantly to the field of material science and engineering by providing a deeper insight into the mechanical behavior of polypropylene and introducing an effective tool for predicting crack initiation in automotive components. The findings hold promise for advancing the design and manufacturing processes in the automotive industry, with potential applications extending to other sectors.

Mechanical behavior of carbon/glass polypropylene hybrid composites

AbstractThis research investigates the influence of graphene and some additives on the mechanical behavior of polypropylene (PP). Anhydride maleic coupling agent (MAPP), graphene nanoplatelets (GNPs), and glass fiber (GF) were incorporated into the polymer matrix. The incorporation of MAPP and/or GNP significantly improved the affinity between the PP matrix and fibers while altering the surface morphology. More than 60% of the fibers showed a dimension lower than 0.5 mm. The tensile strength increased from 27.45 to 41 MPa for the neat PP compared to one of the composites. The strength modulus varied from 0.5 to 0.9 GPa. Mechanical tests showed that the addition of MAPP improved the tensile toughness (from 27.45 to 41 N mm mm−2) by 49%, while the GF increased tensile strength, albeit reducing elongation at break. The dynamic mechanical thermal analysis uncovered distinct behavioral variations among fiber‐reinforced samples, particularly in modulus peak differences. In rheological assessment, the presence of GF notably increased viscosity within certain shear rate ranges (at 100 [1/s], the viscosity goes from 200 to 300 Pa s to neat PP for some composites). This research highlights how chosen additives can influence a PP homopolymer's properties, offering useful insights for practical material processing and design.Highlights MAPP and GNP can increase PP and glass fiber interfacial bonding. Glass fiber raises tensile strength and decreases elongation. Sample with just GNP has a rougher surface, implying better energy dissipation. Glass fiber raises viscosity in the observed shear rate ranges. DMA demonstrates that MAPP and GNP have an influence on energy dissipation.

Multiresponse optimization of drillability factors and mechanical properties of chitosan-reinforced polypropylene composite

In this study, the mechanical and machinability characteristics of chitosan (Cts)-filled polypropylene (PP) composites produced by injection molding method were analyzed. Uniaxial tensile, impact, hardness, and three-point flexural tests were used to observe the influence of Cts filler on the mechanical behavior of PP. For the machinability analysis of these materials, drilling experiments based on Taguchi’s L27 orthogonal array were performed using different drill qualities and machining parameters. Then, machining conditions are optimized through grey relational analysis methodology for machinability characteristics such as thrust force and surface roughness obtained from drilling tests. The results showed that tensile, flexural strength, and percentage elongation decreased while impact strength increased with adding the Cts filler to PP. Moreover, it was determined that the tensile and flexural modulus of elasticity increased significantly and there was a slight increase in hardness. Thrust forces decreased while surface roughness values increased when the Cts filler ratio and feed rate was increased. The optimal machining conditions for minimizing thrust force and surface roughness was obtained as PP/10 wt% Cts material, uncoated tungsten carbide drill, feed rate of 0.05 mm/rev, and cutting speed of 40 m/min. In this regard, PP composite reinforced by 10 wt% Cts is recommended for industrial applications in terms of both the mechanical and machinability characteristics.

Investigation of the Effects of Mold Temperature, Test Temperature and Strain Rate on Mechanical Behaviour of Polypropylene

This paper investigates the time and temperature dependence of a ductile polymer, polypropylene, from the mechanical point of view. As the polymeric specimens have been manufactured by the injection molding process, the influence of mold temperature has been also subjected to the study. Compression tests have been performed both in quasi static and dynamic range (10–3/103 s−1), at different test temperatures (− 20/40 °C), and the results have been analysed in terms of yield stress and failure behaviour. The strength of the polymer is strongly influenced from all the input parameters. Mold temperature has a relevant effect only at room and high temperature. Polypropylene reveals a ductile to brittle transition when it is loaded at high rates, except when test temperature is high. The relation between test temperature, strain rate and yield stress is found to be well described by the Ree–Eyring model, adapted to the two relaxation mechanisms involved.

An evaluation of modified Kaolinite surface on the crystalline and mechanical behavior of polypropylene

An approach for the surface modification of Kaolinite with two types of silane coupling agents is reported to investigate how structural chemical differences would influence the behavior of crystallization, crystalline structure and mechanical properties of polypropylene. Functionalization of Kaolinite showed that the mass ratio and the chemical structure of the silanes directly affected the mechanical and crystalline behavior of the polymer matrix. Compared to octyltriethoxysilane, functionalization with isobutyltrimethoxysilane led to an increase in the surface energy of kaolinite acting as a nucleating agent. This characteristic induced the formation of structures that gave the composite ductile behavior due to intra-spherulitic deformations under mechanical stress. These results have great potential to stimulate both research and industrial interest in the development of new materials based on a polypropylene matrix.

Melt-viscosity and mechanical behaviour of polypropylene (PP)/wood flour composites: Effect of pulverization of wood flour with and without water

Abstract This study analyses the effect of pulverization of wood flour with and without water to the melt-viscosity and mechanical behaviour of polypropylene (PP)/wood flour (WF) composites. The composites were processed in an extruder and subsequent injection moulding. The effects of initial wood flour particle size, type of trees (namely cypress and European scots pine trees) as well as plate gap (200 μm and 350 μm) in pulverization were also evaluated in terms of melt-viscosity, tensile properties, Izod impact strength and fatigue behaviour of the prepared composites. PP/WF composites with pulverised wood flour with water exhibited higher melt-viscosity than that of nonpulverized and pulverized wood flour without water reinforced PP composites. Tensile strength values of composites were slightly affected by the pulverization of wood flour and the enhancement of tensile strength values were depended on the type of initial WF. From Izod impact test results of composites, it was found that the composites reinforced with pulverized wood flour with water displayed higher values of impact energy compared with the composites of pulverized WF without water. Depending on the type of initial WF particle, the positive effect of pulverization of wood flour with water to the fatigue life of the composites was also observed.

On the mechanical behavior of polypropylene, steel and hybrid fiber reinforced self-consolidating concrete

This article presents the results of an experimental investigation on the mechanical behavior of a self-consolidating concrete reinforced with steel, polypropylene and hybrid fibers. Hooked end steel fibers with different lengths and diameters were used as reinforcement in fiber volume fractions of 0.50%, 1.00% and 2.00%. Polypropylene fibers were used as reinforcement in volume fractions of 0.33%, 0.66% and 1.10%. Hybrid composites (HyFRC) were also developed to study the synergy effects of both fibers. The hybrid fiber self-consolidating concrete was produced with the addition of 0.50% of hooked-end steel fibers and 0.66% of polypropylene fibers.Pre-notched SCC prims where tested under monotonic and cyclic three-point bending. The tests where controlled by the crack mouth opening displacement in order to have a better analysis of the post cracking regime. The addition of polypropylene, hooked-end and hybrid fibers was effective in improving the post-peak strength of the composites, even though the use of steel fibers promoted higher values of flexural residual stress due to its geometrical and material properties. The same behavior was observed for the fracture parameters results with an improvement of the crack growth resistance for the analyzed composites.Finally, the effect of the fiber reinforcement on the flexural behavior was studied through structural tests on fiber reinforced self-consolidating concrete beams. Both hooked-end steel fiber and hybrid composites enhanced the resistance at yielding and promoted a lower rate of stiffness degradation, while the polypropylene fiber reinforcement presented an improvement in the ductile behavior of the structural composite. The present work gives an important contribution on the structural and cyclic behavior of steel, PP and hybrid fiber reinforced concrete. The paper makes a comparison on the mechanics of the different composite systems aiming its application in structural elements.

Biocomposites reinforced with natural fibers:thermal, morphological and mechanical characterization

ABSTRACT This study evaluates the thermal, morphological and mechanical behavior of polypropylene (PP) composite with different natural fibers. The fibers used were wood, sugarcane, bamboo, babassu, coconut and kenaf with and without coupling agent. The thermal, morphological and mechanical properties were evaluated, and a composite PP+GFPP (glass fiber) was used as reference. The interaction at the interface fiber-polymer matrix was studied by scanning electron microscopy (SEM) at the fractured surface of the composites, as expected the presence of maleic anhydride (MA) as coupling agent increasedthe interaction at the interface. The influence of natural fiber in the degree of crystallinity of the composites was evaluated by DSC analysis. The samples of PP+GFPP and PP+(PP-MA)+WF (wood flour) showed better temperature stability. PP+GF also presented superior flexural modulus. The thermal dynamic mechanical behavior was evaluated by DMA, a decrease in storage modulus with increasing temperature was observed, the PP+GF and the composite containing maleic anhydride and sugarcane fiber showed higher modulus. The natural fiber biocomposites studied, consistently presented lower flexural modulus and tensile strength than the reference composite, with and without the use of coupling agent. As expected the use of natural fibers lowered the density compared to the reference material.

Effects of Recycling on the Mechanical Behavior of Polypropylene at Room Temperature Through Statistical Analysis Method

This article reports the effects of recycled material percentage, annealing conditions, and glass fiber percentage on the mechanical behavior of injection molded polypropylene samples. Specimens were prepared with different percentages of recycled material ranging from 0 to 100%. Two groups of samples, i.e., non‐annealed and annealed at 150°C, were tested to investigate annealing effects. The effects of adding fiber (0–7.5%) to specimens was also investigated. It was found that increasing the amount of recycled material improves the material properties in a non‐linear trend. Annealing had a significant positive effect on both non‐fiber‐added and fiber‐added samples: it improved the yield stress of non‐reinforced polypropylene samples by more than 10% and their Young's modulus by about 50%. Fiber‐added materials showed more variability, and adding fiber also improved the Young's modulus and the yield stress of the samples by about 50%. The results indicate that the three factors investigated improved toughness of the injected polypropylene samples; however the effects are not significant. The study findings reveal that using recycled polypropylene has no significant effect on the material properties of polypropylene. POLYM. ENG. SCI., 56:1283–1290, 2016 © 2016 Society of Plastics Engineers

Blast furnace slags as functional fillers on rheological, thermal, and mechanical behavior of thermoplastics

ABSTRACTBlast furnace slags (BFS) is a secondary byproduct of iron industry, which has a combination of acidic and basic oxides and show a complex, multiphase structure. If appropriately tailored, BFS could be an effective functional filler, improving the property profile of thermoplastics such as polypropylene (PP) and polystyrene (PS). As a raw material, the proposed filler may introduce both economic and ecological advantages, as it is considered an inexpensive secondary product rather than a natural resource. The current study aims at investigating the effect of incorporating BFS as a micro‐sized filler on the rheological, thermal, and mechanical behavior of PP and PS. BFS types in this study are air‐cooled, crystalline, and amorphous, grounded types. Both types are ground into 71, 40, and 20 μm batches and introduced in 10, 20, and 30 weight fractions via melt kneading. Mixtures are then formed into 4‐mm and 2‐mm thick plates via compression molding. Slight increase in rheological factors is observed with increasing filler loading. BFS hinders the crystallization of PP, resulting in slight increase of crystallization temperatures (Tc) and lowering of crystallization enthalpy (ΔHc). No significant effect of filler on transition temperatures (Tg) is reported. Mechanically, BFS increases the tensile modulus of PP, but decreases its strength. For PS formulations, a modest toughening effect is observed by slag filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43021.

Effect of crystalline structure on the mechanical response of polypropylene under cyclic deformation

Abstract To evaluate the influence of crystalline structure on the mechanical behavior of polypropylene (PP), uniaxial tensile cyclic tests with a mixed program (oscillations between fixed maximum strains and the zero minimum stress) were performed on isotactic PP (iPP) manufactured by the Ziegler-Natta catalysis method, metallocene catalyzed PP (mPP), and annealed mPP. Although the stress-strain diagrams of iPP and mPP under tension are quite similar, their responses under unloading differ markedly. The residual strain (measured as the strain under retraction down to the zero stress) of iPP strongly exceeds that of non-annealed mPP, and annealing of mPP increases this difference. To rationalize these findings, constitutive equations are developed in cyclic viscoelasticity and viscoplasticity of semicrystalline polymers, and adjustable parameters in the stress-strain relations are found by fitting the observations. The ability of the model to describe the observed phenomenon and to predict the mechanical response in multi-cycle tensile tests, with various deformation programs, is demonstrated by numerical simulation.

Mechanical Behavior of Recycled Polypropylene Composites Under Tensile, Bending, and Creep Loading: Experimental and Modeling

By the 2000/53/CE directive, the European Union leads to develop the recycling process industry, specially the plastic one, for end of life vehicles (ELV). To value these recycled materials by an isofunction use, as for example for car semistructure elements, it is necessary for the mechanical properties to be better known. In this study, the effects of the recycling process on the mechanical behavior of polypropylene (PP)/elastomeric, talc particles filled or not, are presented, through different loading tests: tensile (small and finite strain), bending and creep tests. The failure, plasticity, and elasticity parameters modifications are established. Tensile and bending tests lead to some similar characteristics evolution as, for example elastic modulus values. The creep behavior evolution is more complex to understand. Both materials have a near finite strain macroscopic behavior so that, taking account of each component (talc, EPDM or EPR elastomeric part) the intrinsic behavior can be well described in the mechanical model finally presented.

Effects of processing route on morphology and mechanical behavior of polypropylene in equal channel angular extrusion

AbstractChanges of morphology and mechanical behavior of isotactic polypropylene (iPP) due to equal channel angular extrusion (ECAE) were investigated. The iPP specimens were processed for up to two passes in the same direction (route A), with the specimens rotate 180°around loading axis after the previous pass (route C). The macroscopic observation showed that high level of shear strain is introduced in iPP extruded twice in route A. Reflected optical microscopy revealed that the original spherulites are elongated into ellipsoidal shape along the shear direction in route A, and the recovery of the spherulitic shape occurred in iPP extruded in route C. X‐ray diffraction results and the dynamic mechanical analysis showed that the crystalline and amorphous phase are prone to orientation more favorably via route A than route C. The increase of the dynamic storage modulus (E′) indicated that iPP becomes stiffer than other samples when extruded twice in route A. Izod impact testing results demonstrated that the ECAE‐deformed spherulites influence the crack propagation direction. The impact strength of iPP is greatly improved to 490.5 J/m after processed twice in route A, 10 times of that of un‐deformed reference sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Investigation on the effect of a compatibilizer on the fatigue behavior of PP/coir fiber composites

AbstractThe mechanical behavior of polypropylene (PP) and 30 wt% coir fiber reinforced PP composites, with and without compatibilizer, were assessed through monotonic (tensile and bending) and cyclic (fatigue) tests. Fatigue load controlled tests were conducted under tension loads at a frequency of 6 Hz. The fracture mechanism was accompanied by surface fracture analyses using both optical microscopy and scanning electron microscopy. The compatibilizer used was the PP grafted with maleic anhydride. The compatibilized composites exhibited longer fatigue life times. It was also concluded that the presence of coir fibers changed the preferential fatigue mechanism, because the fracture mechanism in PP was mainly caused by heat generated by viscous effects during solicitation (thermal fatigue), whereas in the compatibilized and noncompatibilized PP/coir composites the predominant fracture mechanism was mechanical fatigue. However, thermal fatigue was also observed in the composites, especially in the noncompatibilized ones. © POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Alteration of the mechanical behaviour of polypropylene owing to successive introduction of multiwall carbon nanotubes and stretching

Stretching effects on the morphology of polypropylene/carbon nanotube composites is the focus of this work. The material under investigation was composed of isotactic polypropy lene (iPP) and multiwall car bon nanotubes (MWCNTs) in amount of 0.5 wt.%. The iPP and CNTs were mixed under sonication in a solvent, and the homogenized mixture was melted and pressed. The rectangular plates produced from the material were stretched by a constant load at a fixed temperature in order to obtain extended specimens. The scanning electron microscopy, a thermal gravimetric analysis, and the differential scanning calorimetry were employed to study variations in the structural morphology of the material. A dynamic mechanical analysis showed that the strain-induced crystallization of polypropylene and the possible Stone-Wales transformation of the carbon nanotubes due to stretching improved the mechanical performance of the nanocomposites considered.

Structure and Mechanical Behavior of Isotactic Polypropylene Composites Filled with Silver Nanoparticles

AbstractIsotactic polypropylene (PP) nanocomposites containing 0.1, 0.3, 0.5 and 1.0 wt % silver (Ag) nanoparticles were prepared via melt compounding in a twin-screw extruder followed by injection molding The effects of the Ag nanoparticle additions on the structure and mechanical behavior of PP were studied using DSC, WXRD, optical microscopy, tensile and Izod impact techniques. DSC and WXRD measurements showed that the addition of only 0.1 wt% Ag nanoparticles promote the formation of β-form PP. Further increasing Ag content would not lead to additional increase of the β-PP phase content. The induced β- form PP phase is beneficial to enhance the impact strength and tensile ductility of the PP/Ag nanocomposites.

Polypropylene/carbon nanotube nanocomposite fibers: Process–morphology–property relationships

AbstractThis study is focused on aligning carbon nanotubes in polypropylene matrix by melt spinning. Two different weight percentages (0.5% and 1.0%) of nanotubes were used for the synthesis of the nanocomposite fibers. The effect of the nanotubes on the crystallization and mechanical behavior of polypropylene as well as the effect of draw ratio on the nanocomposite morphology and properties is also discussed. Correlation of fiber morphology and nanotube alignment was done using differential scanning calorimetry, wide‐angle X‐ray diffraction, and transmission electron microscopy. Significant improvement in tensile modulus and tensile strength were observed, which is characteristic of a highly aligned nanotube system. A substantial vincrease in the onset of decomposition was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3844–3850, 2007

Kinetic considerations on the mechanical behaviour of polypropylene + wood flour and polypropylene + sisal fibre blends

Abstract This work is aimed at analyzing by means of simple mathematical models the effect of different integral doses of γ-irradiation on the mechanical properties and concentration of radicals of the blends of polypropylene (PP) + wood flour and PP + sisal fibre. The analysis of the results permits inferring that the kinetic behaviour of the mechanical properties and the concentration of radicals at low integral doses (≤ 10 KGy) are indicative of a complex degradation process, implying the possibility of cross-linking and chain scission reactions both in the polymer as well as in the filler. Consequently, it can be concluded that cross-linking reactions are predominant. The behaviour observed at higher irradiation doses means that both reactions (cross-linking and chain scission) occur, the breaking reactions being the prevailing ones. This study of the kinetic analysis of the tensile properties is based on the behaviour detected for the melt-flow index.

Effect of Die Drawing Process on the Mechanical Behaviour of Polypropylene

Effect of Die Drawing Process on the Mechanical Behaviour of Polypropylene

Optimisation of nanocomposites based on polypropylene/polyethylene blends and organo-bentonite

The effect of the organophilisation of a Na-bentonite, through cationic exchange reaction with a commercial quaternary benzalkonium salt, on the morphology and mechanical behaviour of polypropylene (PP)/low density polyethylene (LDPE) blend matrices has been investigated employing a statistical experimental design. The results show that the tensile modulus and strength of the composites increase (up to 760 and 360%, respectively) as both PP percentage in the matrix and clay content in the composite increase. The properties are more dependent on matrix composition than on clay content. In all cases, the organo-bentonite gives rise to more resistant materials in comparison with the Na-bentonite. Increments of 50–35% in stiffness and strength, respectively, have been observed. The elongation at break mainly depends on matrix composition and a minimum is observed when phase inversion has taken place. The organophilized bentonite gives rise, in some formulations, to an increase in elongation up to 400%. Theoretical equations to predict the tensile behaviour of composites based on PP/LDPE blends with Na-bentonite and benzalkoniun chloride modified bentonite, inside the investigated limits, have been deduced. A morphological study has been carried out by means of scanning electron microscopy.