The effect of interfacial adhesion and morphology on the mechanical properties of polypropylene composites containing different acid surface treated sepiolites

The study of the microstructure of polymeric composites and its relationship to mechanical properties, are of great importance. In the present study vv8 have carried out a study of the microstructure of polymeric composites of polypropylene and different sepiolites treated with organic acids, in order to determine the mesophase produced around We filler particles and its relationship with the mechanical properties of the composites. This study was made using scanning electron microscopy, differential Scanning calorimetry and mechanical tests.     

Extrusion and mechanical properties of highly filled cellulose fibre–polypropylene composites

This study focused on manufacturing of highly filled cellulose fibre–polypropylene composites and evaluation of the mechanical properties of the composites. Cellulose fibre reinforced polypropylene composites with up to 60 wt% of fibres with and without coupling agent were manufactured by extrusion. In order to achieve consistent feeding of the fibres into the extruder a pelletization technique was used where the fibres were pressed into pellets. Two commercial grades of cellulose fibres were used in the study, bleached sulfite and bleached kraft fibres. Fibre dimension measurements showed that the pelletization process and extrusion at high fibre loading caused the most severe fibre breakage. Flexural testing showed that increased fibre loading made the composites stiffer but reduced the toughness. Addition of maleic anhydride grafted coupling agent (MAPP) increased the stiffness and strength of the composites significantly. In general, there was no significant difference in the mechanical properties between the composites with kraft and sulfite fibres. An interesting finding was that the flexural modulus and strength of the MAPP modified cellulose fibre–polypropylene composites were not higher than what has previously been reported for wood flour–polyolefin composites. Scanning electron microscopy showed that addition of coupling agent improved the interfacial adhesion between the fibres and polypropylene matrix.     

The effects of the injection moulding temperature on the mechanical properties and morphology of polypropylene man-made cellulose fibre composites

Composites made of polypropylene and man-made cellulose fibres that are intended for injection moulding applications show potential for use in sustainable and light weight engineering with high energy absorption capacity. Due to the thermal sensitivity of the cellulose fibres, process parameters play an important role during the injection moulding process. A polypropylene and a man-made cellulose fibre were chosen for this investigation. Effective melt temperatures between 200 °C and 269 °C were used to process the compounds into test specimens. Tensile, impact and colorimetric tests, as well as an SEM analysis, and a measurement of the fibre length distribution were carried out in order to characterise the mechanical and optical properties of the composites. It was observed that the fibre length becomes shorter above 256 °C and elongation at break and Charpy strength (notched) of the composites already decrease at lower temperatures than tensile strength. A direct correlation between mechanical properties and discoloration was not observed. Therefore, melt temperatures up to 250 °C are suitable for these composites.     

Effect of transcrystalline morphology on interfacial adhesion in cellulose/polypropylene composites

A study was conducted on the effect of cotton cellulose fibres on the crystallization behaviour of isotactic polypropylene (PP) from the melt and the resulting morphology. When the PP was allowed to crystallize isothermally at 131° C, the cotton fibres acted as nucleating agents and a transcrystalline phase was created around the fibres. Quench cooling of the melt prevented the occurrence of such a phase. Transcrystalline layers of different thicknesses were created by interrupting the isothermal crystallization at certain intervals and quenching the melt. The effect of these morphologies on interfacial shear stress transfer was investigated using the single-fibre fragmentation test. It was found that the transcrystalline morphology at the fibre/matrix interface improved the shear transfer considerably when a tensile load was applied in the fibre direction. One mechanism is proposed to be particularly responsible for this increase: slow cooling favours the kinetics of the approach of PP molecules, and hence interfacial adsorption, which yields an ordered transcrystalline PP interphase having a high density of intermolecular secondary bonds with the cellulose surface. An increase in the shear transfer efficiency with increasing thickness of the transcrystalline layer was also observed.     

Effects of maleated polypropylene on the morphology,thermal and mechanical properties of short carbon fiber reinforced polypropylene composites

The aim of this study was to determine the effect of the maleic anhydride grafted polypropylene (PP-g-MAH) on the properties of short carbon fiber (CF) reinforced polypropylene (PP) composites. The composites were prepared by melt blending and injection molding techniques at different percentages of CF. Tensile tests, hardness, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM) were performed to characterize the physical and morphological properties of the prepared composites. It was observed from SEM photographs that modification with PP-g-MAH improved the interfacial adhesion between the carbon fibers and PP matrix. The ultimate tensile strength, hardness and modulus values of modified PP composites were higher compared to the values of CF reinforced PP composites. Melting temperature of all composites was not changed significantly with increasing CF content; however degree of crystallinity values were decreased with the increasing CF content level.     

Mechanical properties of polypropylene composites reinforced with chemically treated abaca

In the present study, abaca was chemically treated with benzene diazonium salt in order to improve in the mechanical properties of the abaca-PP composites. Both raw and treated abaca samples were utilized for the fabrication of the composites. The mechanical properties of the composites prepared from chemically treated abaca are found to increase substantially compared to those of untreated ones. Tensile strengths of the composites of both raw and chemically treated abaca-PP composites showed a decreasing trend with increasing filler content. However, the values for the chemically treated abaca-PP composites at all mixing ratios are found to be higher than that of neat PP. The surface morphologies of the fracture surfaces of the composites were recorded using scanning electron microscopy (SEM). The SEM micrographs reveal that interfacial bonding between the treated filler and the matrix has significantly improved, suggesting that better dispersion of the filler into the matrix has occurred upon treatment of abaca.     

Mechanical properties and morphology of microparticle and nanoparticle-filled polypropylene composites

Hydrophilic microparticle and nanoparticle-filled isotactic polypropylene (iPP) composites containing 5 wt% particles were extruded in a Berstorff extruder and then injection molded. For characterization the tensile and unnotched Charpy impact tests were performed. The results show that significant improvements in tensile strength, yield elongation, and unnotched impact strength are achieved in iPP/nanoparticle composite based on a good dispersion quality of nanoparticles. In the case of iPP/microparticle composite, the tensile modulus and yield strength are markedly increased compared to neat matrix, but the yield elongation and unnotched impact strength are drastically decreased due to broad size distribution of microparticles. The fracture mechanisms were discussed by studying surface morphology of failed samples. Furthermore, the influence of crystalline behavior on mechanical properties of iPP composites was discussed.     

Vetiver–polypropylene composites: Physical and mechanical properties

Injection molded vetiver–polypropylene (PP) composites at various ratios of vetiver content and vetiver length were prepared. When compared to PP, vetiver–PP composites exhibited higher tensile strength and Young’s modulus but lower elongation at break and impact strength. An increase in vetiver content led to an increase in viscosity, heat distortion temperature, crystallization temperature, and Young’s modulus of the composites. On the other hand, the decomposition temperature, tensile strength, elongation at break, and impact strength decreased with increasing vetiver content. The chemical treatment of the vetiver grass improved the mechanical properties of the composites.     

Effect of pimelic acid on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites

The pimelic acid (PA) was used as a new surface modifier for wollastonite. The effects of PA treatment on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites were investigated. The Fourier transform infrared spectroscopy analysis revealed that the PA bonded to the wollastonite's surface and formed the calcium pimelate after reacting with the wollastonite. The results of wide angle X-ray diffraction, differential scanning calorimetry and polarized light microscopy proved that the PA treated wollastonite induced more β-crystalline form and decreased the spherulites sizes of polypropylene. The results of scanning electron microscopy showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between polypropylene and wollastonite. The toughness of the composites was improved by the more ductile β-form spherulites. When 2.5 wt% of PA treated wollastonite was added, the Izod notched impact strength reached its maximum, a value of 17.33 kJ/m², which was 3.19 times greater than that of the blank polypropylene.     

Interfacial modification of polypropylene composites filled with magnesium hydroxide

The mechanical behaviour of polypropylene composites containing magnesium hydroxide is considered with reference to the influence on properties of filler surface modification. Compared to composites containing untreated filler, mechanical properties can be strongly affected by the chemical nature and amount of surface treatment applied. In particular, very significant improvements in toughness are obtained using sufficiently high levels of magnesium stearate to ensure complete coverage of the magnesium hydroxide surface. Results are discussed in terms of the observed deformation mechanism in the polymer matrix.     

甘蔗渣纤维增强聚丙烯复合材料的制备和力学性能

利用注射成型制备了甘蔗渣纤维增强聚丙烯复合材料, 分析了纤维质量分数、 注射成型条件以及添加物对复合材料力学性能的影响。结果表明, 随着纤维质量分数的增加, 材料的弯曲模量呈递增趋势。由于甘蔗渣纤维热降解的发生, 材料的力学性能随筒体温度的增加呈下降趋势。在模具温度90℃、 注射间隔时间30s、 不同的筒体温度185℃和165℃的成型条件下, 材料的弯曲性能和冲击强度分别呈现最大值。添加了马来酸酐改性聚丙烯后, 材料的弯曲强度和冲击强度得到了提高。      

Physico-mechanical properties of chemically treated coir reinforced polypropylene composites

The physico-mechanical properties of coir reinforced polypropylene (PP) composites been investigated. In order to attain improved mechanical properties of the composites coir was chemically treated with o-hydroxybenzene diazonium salt. Both raw and treated coir samples were utilized for the fabrication of the composites. The mechanical properties of the composites prepared from chemically treated coir are found to be much better compared to those of untreated ones. Tensile strengths of the composites of both raw and chemically treated coir-PP composites showed a decreasing trend with increasing filler content. However, the values for the chemically treated coir-PP composites at all mixing ratios are found to be higher than that of neat PP. The surface morphologies of the fractured surfaces of the composites were recorded using scanning electron microscopy (SEM) to gain information about the fiber–matrix interfacial adhesion in the composites.     

Continuous-glass-fibre-reinforced polypropylene composites: I. Influence of maleic-anhydride-modified polypropylene on mechanical properties

This study investigates the influence of maleicanhydride-modified polypropylene (m-PP) on monotonic mechanical properties of continuous-glass-fibre-reinforced polypropylene (PP) composites. Maleicanhydride-modified polypropylene was added to the PP homopolymer to improve the adhesion between the matrix and the glass fibre. Three-point bending tests were performed on 0° and 90° unidirectional glass-fibre/PP laminates with various weight fractions of m-PP in the PP matrix. These tests showed an increase in both longitudinal and transverse flexural strength up to 10 wt% m-PP, whereas at higher weight fractions of m-PP a decrease in flexural strength was observed. No significant influence of m-PP on composite stiffness was observed. Additional mechanical tests on unidirectional glass/PP composites with 0 wt% and 10 wt% m-PP showed only a small increase in fibre-dominated properties such as longitudinal tensile strength and strain, whereas composite properties that are governed by the interphase, such as transverse, shear and compressive strength, showed significant increases as a result of matrix modification and an enhanced interaction between the glass fibres and the PP matrix.     

Correlations between image-analysed morphology and mechanical properties of calcium carbonate-filled polypropylene

Calcium carbonate-filled polypropylene composites were processed on two different highintensity mixing devices. The resulting relationships between morphology, processing conditions and mechanical properties of these composites were studied using an electron microscope with an image-analysis system and impact and tensile testing. Only under more extreme conditions did the recently developed turbine mixer give as good a dispersion as the classical Banbury-style mixer. Relatively small additions of the filler resulted in small increases in absorbed impact energy. Semi-quantitative information about the randomness achieved in the mixing process was obtained using a dilation/counting procedure and computer-derived spatial images. Object-specific parameters such as the percentage of objects greater than 1 m in size give good correlation with the mechanical properties of the mixture.     

Dynamic mechanical properties of short sisal fibre reinforced polypropylene composites

The dynamic mechanical properties of short sisal fibre reinforced polypropylene composites containing both untreated and treated fibres have been studied with reference to fibre loading, fibre length, chemical treatments, frequency and temperature. By the incorporation of short sisal fibre into polypropylene, the storage moduli (E′)and loss moduli (E″) have been found to be increasing whereas the mechanical loss factor (tan δ) decreasing. The storage modulus decreases with increase in temperature. The treated fibre composites show better properties compared to untreated system. The Arrhenius relationship has been used to calculate the activation energy for the glass transition. The use and limitations of various theoretical equations to predict the tan δ and storage modulus of the fibre reinforced plastic composites have been discussed. Cole–Cole analysis has been carried out to understand the phase behaviour of the composite samples. A master curve for the modulus of the blend is drawn by applying the time–temperature super position principle.     

磷酸盐玻璃／聚丙烯复合材料的结晶行为和力学性能

制备了两种不同玻璃化温度的磷酸盐玻璃（P—glass）,研究了P—glass对聚丙烯（PP）基体结晶行为和力学性能的影响。结果表明,P—glass在PP中具有异相成核作用,使PP的结晶温度升高。具有较低玻璃化温度（176℃）的P—glass,能诱导生成口晶,使p-glass／PP复合材料的断裂伸长率与纯PP相比从427...     

Structural,thermal, mechanical and dynamic mechanical properties of cenosphere filled polypropylene composites

Polypropylene (PP)/cenosphere based composites were fabricated and characterized for their structural/morphological and mechanical properties such as tensile, flexural, impact and dynamic mechanical properties such as storage and loss moduli as a function of temperature. The morphological attributes were characterized by scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD) while the thermal characterizations were done by conducting differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). The morphological investigations have revealed a uniformly distributed/dispersed state of the cenosphere in the bulk PP matrix of the composites. The WAXD/DSC studies have revealed a decrease in crystallinity of the composites with increase in cenosphere content. Dynamic mechanical analysis (DMA) revealed an enhancement in the energy dissipation ability of the composite with 10 wt.% of cenosphere and an increase in the storage modulus up to ∼30% in the composites relative to the soft PP-phase. The tensile modulus increased up to ∼43% accompanied by a nominal decrease in tensile strength while the strain at break remained largely unaffected. The impact strength of the composites marginally reduced compared to PP indicating a low-cost material-concept with maximized stiffness–toughness combination. The theoretical modeling of the tensile data revealed appreciable extent of phase-adhesion despite the cenospheres lack any surface modification indicating better extent of mechanical interlocking and surface-compatibility between polymer and filler. Fractured surface morphology indicated that the failure mode of the composites undergoes a switch-over from matrix-controlled shear deformation to filler-controlled quasi-brittle modes above a cenosphere loading of 10 wt.% in the composites.     

The mechanical properties of ternary composites of polypropylene with inorganic fillers and elastomer inclusions

The effect of elastomer volume fraction and phase morphology on the elastic modulus of ternary composites polypropylene (PP)/ethylene-propylene rubber (EPR)/inorganic filler containing 30 vol % of either spherical or lamellar filler has been investigated. Phase morphology was controlled using maleated polypropylene (MPP) and/or maleated ethylene-propylene elastomer (MEPR). As revealed by SEM observations, composites of MPP/EPR/filler exhibit separation of the filler and elastomer and good adhesion between MPP and the filler, whereas composites of PP/MEPR/filler exhibit encapsulation of the filler by MEPR. Composite models were utilized to estimate upper and lower bounds for the elastic modulus of these materials, which is strongly dependent on the morphology of the ternary composite. A model based on the Kerner equation for perfect separation of the soft inclusions and rigid fillers gives a good prediction of the upper limit for relative elastic modulus as a function of filler and elastomer volume fractions. The lower limit, achieved in the case of perfect encapsulation, depends significantly on the particle shape. Good agreement was found between experimental data and lower limits predicted using the Halpin-Tsai equation for lamellar filler and the Kerner-Nielsen equation for spherical filler. In order to calculate reinforcing efficiency of the core-shell inclusions, the finite element method (ANSYS 4.4A, GT STRUDL) has been used.     

聚丙烯/海泡石复合材料的制备、表征及力学性能

采用十六烷基三甲基溴化铵(CTAB)对海泡石(SEP)进行有机化改性,制备有机改性海泡石(OSEP)和聚丙烯(PP)/SEP复合材料。经SEM、XRD、FT-IR、TG和CA分析,表明海泡石表面吸附有一定量的季铵盐分子,并且部分季铵盐分子顺利进入海泡石孔道。经TG分析,800℃时OSEP的残留质量比SEP提高17.63%。复合材料的拉伸、冲击和WAXD测试表明,OSEP的加入减少了β晶型的含量,增加了α晶粒的含量,有效提高了复合材料的力学性能。当OSEP含量为1.5%时,能获得力学性能较优的复合材料。     

Morphology and mechanical properties of isotactic polypropylene glass mat thermoplastic composites modified with organophilic montmorillonite

Satisfactory impregnation of glass fiber mats may be obtained with isotactic polypropylene/montmorillonite (MMT) nanocomposites under conditions comparable with industrial conditions. However, it is demonstrated here that the high melt viscosity of the nanocomposite matrix at low shear rates may significantly influence the release of the compressive load in the glass mat and hence the glass fiber distribution in consolidated specimens. Thus, depending on the initial lay-up and overall glass fiber content, the bending modulus may either increase or decrease with increasing MMT content, whereas the tensile modulus is more consistent with micromechanical models assuming a uniform glass fiber distribution. Results from fractographic analyses show that the presence of matrix rich layers at the specimen surfaces may also lead to premature crack initiation and failure in flexion.