Polypropylene Hybrid Composites Research Articles

Date palm wood flour/glass fibre reinforced hybrid composites of recycled polypropylene: Mechanical and thermal properties

Recycled polypropylene (RPP) based hybrid composites of date palm wood flour/glass fibre were prepared by different weight ratios of the two reinforcements. Mixing process was carried out in an extruder and samples were prepared by injection molding machine. Recycled PP properties were improved by reinforcing it by wood flour. The tensile strength and Young’s modulus of wood flour reinforced RPP increased further by adding glass fibre. Glass fibre reinforced composites showed higher hardness than other composites. Morphological studies indicated that glass fiber has good adhesion with recycled PP supporting the improvement of the mechanical properties of hybrid composites with glass fiber addition. Addition of as little 5wt% glass fibre to wood flour reinforced RPP increases the tensile strength by about 18% relative to the wood flour reinforcement alone. An increase in wood particle content in the PP resulted in a decrease in the degree of crystallinity of the polymer. The tensile strength of the composites increased with an increase in the percentage of crystallinity when adding the glass fibre. The improvement in the mechanical properties with the increase in crystallinity percentage (and with the decrease of the lamellar thicknesses) can be attributed to the constrained region between the lamellae because the agglomeration is absent in this case.

Polypropylene hybrid composites with wood flour and needle-like minerals

Polypropylene (PP) hybrid composites filled with wood flour and needle-like minerals, including SiO2 whiskers, CaCO3 whiskers and milled glass fibres, were prepared by melt blending and injection moulding. Maleic anhydride grafted PP was used as a compatibiliser. The effect of the needle-like minerals’ type and content on the crystallisation and melting behaviour, morphology, mechanical properties, moisture resistance and thermal stability of the hybrid composites were studied. The results showed that SiO2 and CaCO3 whiskers exhibited strong heterogeneous nucleation and promotion effect on PP crystallisation. Milled glass fibre was superior to enhance the tensile, flexural and impact properties of hybrid composites. Maleic anhydride grafted PP was selective for the interfacial modification of hybrid fillers and the best modification effect achieved in the composites hybridised with milled glass fibre. Comparatively speaking, the optimal proportions between the three kinds of needle-like minerals and the wood flour for the hybrid modification of PP all lie in 1·5∶48·5.

Mechanical and Morphological Study of Talc/calcium Carbonate Filled Polypropylene Hybrid Composites Weathered in Tropical Climates

Dua jenis komposit, iaitu komposit polipropilena (PP) terisi–tunggal (diisi dengan talkum atau kalsium karbonat) dan komposit PP terisi–hibrid (diisi campuran talkum dan kalsium karbonat) yang telah diacuan–suntikkan kepada bentuk ‘dumbbell’. Spesimen tersebut didedahkan kepada pencuacaan semulajadi, iaitu iklim tropika di Pulau Pinang, Malaysia selama 6 bulan. Selepas tempoh pendedahan, sifat mekanikal PP terisi–tunggal telah merosot akibat degradasi fizikal dan kimia yang teruk. Kajian yang lebih mendalam ke atas aspek struktur komposit telah dijalankan untuk mendapatkan kepastian tentang keadaan degradasi tersebut. Walau bagaimanapun, komposit PP–terisi hibrid menunjukkan keupayaan untuk mengekalkan sifat tegangan dan lenturan yang lebih baik walaupun terdapat kesan degradasi pada permukaan spesimen. Didapati bahawa kesan ‘hibridisasi’ telah berjaya meningkatkan ketahanan komposit hibrid terhadap degradasi pencuacaan yang teruk, sehingga struktur–struktur di dalam komposit tersebut dapat dilindungi daripada kesan degradasi, sedangkan permukaan komposit telah mengalami degradasi yang teruk. Kata kunci: Polipropilena; komposit hibrid; pengoksidaan foto; pengguntingan rantai; degradasi terma; pencuacaan semula jadi Two kinds of composites, namely single–filler polypropylene (PP) composites (contain either talc or calcium carbonate) and hybrid–filler PP composites (consist of a mixture of talc and calcium carbonate) were injection moulded into dumbbells. These specimens were subjected to natural weathering i.e. tropical climate in Penang, Malaysia for 6 months. After 6 months of exposure, the mechanical properties of single–filler PP composites deteriorated due to severe physical and chemical degradation. This was confirmed after studies were made on the structure aspects of the composite. However, the hybrid–filler PP composites were found to show better retention in both tensile and flexural strength albeit have undergone some degree of degradation as well. It was found that the ‘hybridization’ effect has successfully increased the resistance of the hybrid composite to severe environmental degradation to the extent that it protects the internal structure of the composite from environmental damage, while the surface of the composite gets severely degraded. Key words: Polypropylene; hybrid composite; photooxidation; chain scission; thermal degradation; natural weathering

The Effect of Water Absorption on Mechanical Properties of Wood Flour/Wheat Husk Polypropylene Hybrid Composites

The main objectives of this research were to study the effect of water absorption on mechanical properties of hybrid fiber reinforcement for polypropylene composites. The poor resistance towards water absorption is one of the draw- backs of natural fibers. Hybrid filler-polypropylene composites are subjected to water immersion tests in order to study the effects of water absorption on the mechanical properties. Composites specimens containing 30 phr and 40 phr fiber weight were prepared by melt blending process. Water absorption tests were conducted by immersion specimens in distilled water at room temperature for different time durations (24, 48, 72, 96, 120, 144, 168, 192 hours). The tensile, flexural and impact properties were investigated before and after water absorption. The percentage of moisture uptake increased as the increasing order of the filler loading due to the high cellulose content. The phase morphology of wood flour/wheat husk polypropylene hybrid composites were investigated by SEM, the dynamic mechanical properties of the composite are analyzed by DMA & wheat, wood filler interaction are analyzed by FT-IR.

Polypropylene hybrid composites filled by wood flour and short glass fiber: Effect of compatibilizer on structure and properties

Polypropylene (PP) hybrid composites filled with wood flour (WF) and short glass fiber were prepared by melt blending and injection molding. Maleic anhydride-grafted PP (PP-g-MA), glycidyl methacrylate-grafted PP (PP-g-GMA), maleic anhydride-grafted ethylene-octene copolymer (POE-g-MA), and maleic anhydride-grafted hydrogenated styrene-butadiene-styrene (SEBS-g-MA) were used as the compatibilizers to enhance the interfacial adhesion between PP and the fillers. The effect of the types and contents of graft polymer on the crystallization and melting behavior, micromorphology, mechanical property, moisture resistance, and thermal stability of PP hybrid composites was observed. The result showed that PP-g-MA and PP-g-GMA had strong heterogeneous nucleation and promotion effect on PP crystallization. PP-g-MA was superior to enhance the tensile, flexural, and impact properties of composites. Hybrid composites had excellent moisture resistance and low water absorption. WF and PP macromolecular compatibilizer could improve the thermal stability of PP composites, in which the most obvious effect was obtained in PP-g-MA-modified WF and short glass fiber hybrid system. As a result, PP/WF composite could achieve outstanding improvement effect by being modified with macromolecular compatibilizer.

Study on the Performance of Hybrid Jute/Betel Nut Fiber Reinforced Polypropylene Composites

The newest research and development results dealing with natural short fiber composites show new possibilities for environmentally-friendly materials. Current production trends clearly indicate the increased use of structural, nonstructural and molded natural fiber based composite panels for many applications. In our present work, two types of short natural fibers, namely jute and betel nut fibers, are employed as fillers for the formation of short fiber reinforced polypropylene composites in difference ratios (fiber content: 3, 5, 10 and 20 wt%) by hot-press moulding technique. Different jute-betel nut reinforced polypropylene hybrid composites were prepared in the ratio of 10:5, 10:10 and 10:15 wt% fiber contents with 85% PP, 80% PP and 75% PP, respectively. Mechanical properties of the composites, i.e., tensile, bending and impact strengths, were investigated. For better compatibility, jute and betel nut fibers were subjected to alkalization and the hybrid composites of alkalized jute/betel nut and PP showed much improved performance with respect to other composites. Water absorption capacity and degradation behavior of the different composites were also studied.

Development of glass fiber, wollastonite reinforced polypropylene hybrid composite: Mechanical properties and morphology

Hybridization with small amounts of mineral fibers makes these glass fiber composites more suitable for technical applications. This study focused on the performance of injection molded short wollastonite fiber and chopped glass fiber reinforced hybrid polypropylene composites. Results showed that hybridization of glass fiber and wollastonite was found to be comparable to that of polypropylene glass fiber composites. Analysis of fiber length distribution in the composite and fracture surface was performed to study fiber breakage fracture mechanism. The simultaneous compounding of polypropylene with two fillers was done to obtain a hybrid composite. The mechanical properties of hybrid, injection molded, chopped glass fiber/wollastonite/polypropylene composites have been investigated taking into account the effect of hybridization by these two types of fillers. This system is expected to have considerable mechanical properties, good surface finish and low cost. It has been found that the tensile, flexural, and impact properties of the filled polypropylene were higher than those of unfilled polypropylene. The hybrid effects of the tensile strength and modulus were studied by the rule of hybrid mixtures (RoHM) using the values of single fiber composites.

Degradation and flammability behavior of PP/ banana and glass fiber-based hybrid composites

Hybrid composites of polypropylene (PP) reinforced with short banana and glass fiber were fabricated using melt-blending technique followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to promote the interfacial adhesion between the fibers and the PP matrix. The degradation behavior in the composites and hybrid composites were studied employing FTIR spectroscopy. Test results indicated an increase in the carbonyl and hydroxyl regions increase with the incorporation of fibers within the PP matrix. Further, BFPP composites exhibited higher degradation tendency as compared with the virgin polymer as well as the hybrid composites. Extent of biodegradation in the irradiated samples showed increased weight loss in the BFPP samples thus revealing effective interfacial adhesion upon hybridization with glass fibers. Horizontal rate of burning test indicated 50% reduction in rate of burning in BFPP and BGPP composites with the incorporation of Mg(OH)2 flame retardant. Limiting oxygen index tests also showed more consumption of oxygen for combustion in case of BGPP hybrid composites indicating improved flame retardant characteristics.

Sisal Glass Fiber Reinforced PP Hybrid Composites: Effect of MAPP on the Dynamic Mechanical and Thermal Properties

Hybrid composites of polypropylene (PP) reinforced with short sisal and glass fibers were prepared using twin-screw extruder, followed by injection molding in the presence and absence of maleic anhydride grafted PP (MAPP) as a coupling agent. The mechanical properties such as tensile strength, flexural strength, and impact strength increased by an optimum value at 15% sisal and 15% glass fiber loading in the presence of 2% MAPP. The rate of water absorption in the composites decreased due to the presence of glass fiber and coupling agent. The storage modulus of sisal/glass reinforced PP hybrid composites (SGRP) showed maximum improvement after treatment with MAPP. The fiber matrix morphology of the interface region in the composites was examined using scanning electron microscopy. The differential scanning calorimetry thermogram confirms higher thermal stability in the case of hybrid composites.

Influence of short bamboo/glass fiber on the thermal, dynamic mechanical and rheological properties of polypropylene hybrid composites

The present article summarizes the development of polypropylene-bamboo/glass fiber reinforced hybrid composites (BGRP) using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The crystallization and melting behavior were investigated employing differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) indicates an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus ( E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The rheological behavior of the hybrid composites has also been studied using time–temperature superposition (TTS) principle and corresponding viscoelastic master curves have been constructed.

Studies on Mechanical Performance and Water Absorption of Recycled Newspaper/Glass Fiber-reinforced Polypropylene Hybrid Composites

The present experimental work is aimed at studying the performance of recycled newspaper and recycled newspaper/glass fiber hybrid polypropylene composites. The effects of glass fiber loading and maleic anhydride (MA) as a coupling agent on the tensile behavior and impact strength of composites containing 30 wt% fiber were examined. The results suggest that the tensile strengths of the recycled newspaper/PP composites increase with increasing glass fiber content. A value of 55 MPa for tensile strength and 4.1 GPa for the tensile modulus is achieved from a hybrid composite containing 10 wt% of newspaper and 20 wt% of glass fiber. The impact strength of the newspaper/PP composites progressively decreased with increasing glass fiber content. Adding (MA) by 2 wt% in the composite formulation significantly improved both the dimensional stability and mechanical properties. Microstructure analysis of the fractured surfaces of modified composites confirmed improved interfacial bonding. Dimensional stability and strength properties of the composites can be improved by increasing the glass fiber content and or by addition of coupling agent. This project has shown that the composites treated with glass fiber and coupling agents will be desirable as building materials due to their improved stability and strength properties.

Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.

Polypropylene—Bamboo/Glass Fiber Hybrid Composites: Fabrication and Analysis of Mechanical, Morphological, Thermal, and Dynamic Mechanical Behavior

Hybrid composites of polypropylene reinforced with bamboo and glass fibers (BGRP) were fabricated using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The mechanical properties of the hybrid composites were studied from tensile, flexural, and impact tests. Mechanical tests indicated an increase in tensile, flexural, and impact strength of the BGRP hybrid composites at a bamboo:glass fiber ratio of 15:15 ratio in the presence of 2 wt% of MAPP. Nearly, 69, 86, and 83% increase in tensile flexural and impact strength respectively has been observed as compared with virgin PP. The fiber matrix interfacial morphology of the tensile fractured specimens was studied using scanning electron microscopy (SEM) which showed less fiber pullout and comparatively less gaps between the fiber and the base matrix in the case of MAPP treated hybrid composites. The crystallization, melting behavior and thermal stability of the hybrid composites were investigated employing differential scanning electron microscopy (DSC) and thermogravimetric analysis (TGA). Thermogravimetric analysis (TGA) showed an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus (E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The tan δ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of PP.

Effect of chemical treatments on the mechanical, flow, and morphological properties of talc‐ and kaolin‐filled polypropylene hybrid composites

AbstractThis study was performed with commercially available phenyl trimethoxysilane (PTMS) and neoalkoxytitanate [i.e., neopentyl(diallyl)oxytri(dioctyl)phosphato titanate (LICA 12)] as coupling agents. PTMS and LICA 12 were used to treat talc and kaolin to compare their effects with untreated fillers upon incorporation into polypropylene (PP). Single‐filler PP composites (containing either talc or kaolin) and hybrid‐filler composites (containing a mix of both talc and kaolin) were compounded in a twin‐screw extruder and subsequently injection‐molded into dumbbells. The incorporation of PTMS and LICA 12 slightly decreased the tensile and flexural properties in terms of modulus and strength but increased the elongation at break for both single‐filler and hybrid‐filler composites. There was also a significant improvement in the impact strength of the composites, particularly those treated with LICA 12. The hybrid composites, through the synergistic coalescence of positive characteristics from talc and kaolin with the aid from chemical treatment provided an economically advantageous material with mechanical properties comparable to those of the single‐filler‐filled PP composites. Further investigations on flow and morphological properties were also done to correlate the mechanical properties of the single‐ and hybrid‐filler‐filled PP composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Influence of the zeolite type on the mechanical–thermal properties and volatile organic compound emissions of natural‐flour‐filled polypropylene hybrid composites

AbstractThe physicomechanical properties, thermal properties, odor, and volatile organic compound (VOC) emissions of natural‐flour‐filled polypropylene (PP) composites were investigated as a function of the zeolite type and content. The surface area and pore structure of the natural and synthetic zeolites were determined by surface area analysis and scanning electron microscopy, respectively. With increasing natural and synthetic zeolite content, the tensile and flexural strengths of the hybrid composites were not significantly changed, whereas the water absorption was slightly increased. The thermal stability and degradation temperature of the hybrid composites were slightly increased with increasing natural and synthetic zeolite content. At natural and synthetic zeolite contents of 3%, the various odors and VOC emissions of the polypropylene/rice husk flour and polypropylene/wood flour hybrid composites were significantly reduced because of the absorption of the odor and VOC materials in the pore structures of the natural and synthetic zeolites. These results suggest that the addition of natural and synthetic zeolites to natural‐flour‐filled thermoplastic polymer composites is an effective method of reducing their odor and VOC emissions without any degradation of their mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Relationship of Rheological Study with Morphological Characteristics of Multicomponent (Talc and Calcium Carbonate) Filled Polypropylene Hybrid Composites

Polypropylene (PP) copolymer reinforced with talc, CaCO3, or multicomponent fillers (a combination of talc and CaCO3) were compounded in a Brabender Plasti-Corder® internal mixer. These compounds then experienced an extrusion process by means of a capillary rheometer. The rheological and morphological (SEM) properties of the extrudate were analyzed to investigate the effect of shear stress, filler type, and temperature. The rheological studies revealed that the incorporation of multicomponent fillers has increased the melt viscosity. However, different ratio of filler type demonstrates no significant effect. It is also shown that the system appears pseudoplastic over one range of shear rates but dilatant over another. The presence of filler seems to have a pronounced influence on dilatant flow in filled PP. Observation on SEM analysis at high shear stress showed that large CaCO3 agglomerates are seen to be randomly dispersed whereas talc particles are more uniformly distributed and oriented to flow direction, suggesting better mixing.

Fabrication and Characterization of Sisal/Glass and Polypropylene Hybrid Composites

The present work summarizes an experimental study on the dynamic mechanical behaviour of sisal – glass fiber reinforced PP composites (SGRP). Variation in mechanical strength, storage modulus (E’), loss modulus (E’’) and damping parameters (tan δ) with the addition of fibers and MAPP were investigated. Mechanical tests revealed an increase in the tensile, flexural and impact strength in the SFRP composites with an increase in the fiber loading from 10% to 30%. Further the SGRP composites prepared using 15 wt% of glass and 15 wt % of sisal fiber, exhibited improved mechanical performance as compared with the virgin matrix as well as 30% SFRP composites. The fiber matrix morphology of the interface region in the composites was examined employing SEM analysis of the tensile fracture specimens. Thermal stability in the composites was studied using TGA/DTG thermo grams. Dynamic mechanical analysis data showed an increase in the storage modulus of the treated composite. The tanδ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of PP. FTIR spectra of the treated and untreated sisal fibers was also studied to ascertain the existence of the type of interfacial bonds.

Studies on the Water Absorption Properties of Short Hemp—Glass Fiber Hybrid Polypropylene Composites

Hemp fiber is one of the inexpensive and readily available bast natural fibers and hemp-fiber reinforced polymer composite products have gained considerable attraction for automotive interior products. Though extensive research has been made on the performance evaluation of these composite materials, not much data is available on the moisture absorption of the composites, which restricts their use in exterior applications. This study aims to investigate the moisture absorption of short hemp fiber and hemp-glass hybrid reinforced thermoplastic composites to study their suitability in outdoor applications. The water absorption properties and its effect on the tensile properties of hemp and hemp/glass fiber hybrid polypropylene (PP) composites prepared by an injection molding process were investigated. Effect of hybridization on the water uptake and the kinetics of moisture absorption of the hemp fiber composites were evaluated by immersing the hybrid composite samples in distilled water at different temperatures, of 40, 60 and 80°C. The composites showed a Fickian mode of diffusion; however, a deviation was observed at higher temperature and may be attributed to the microcraks developed at the interface and dissolution of the lower molecular weight substances from the natural fibers. Equilibrium moisture content (Mm) showed that water up take of 40 wt% hemp fiber reinforced PP composites was highest and incorporation of glass fiber decreased the water uptake significantly (40%). Equilibrium moisture content was found to be independent of temperature, while diffusion coefficient (D) was increased with temperature. Effect of water absorption on the tensile properties of the composites showed that there is a significant reduction in strength and stiffness. It was observed that hybridization with glass fibers did not have any significant effect on the strength properties of the aged samples. The tensile properties of the re-dried aged samples showed an increased retention of strength properties after drying; however a complete recovery of the properties has not been achieved. This indicated that water absorption is not a physical process and permanent damage occurred to the composite after aging.

Mechanical, flow, and morphological properties of talc‐ and kaolin‐filled polypropylene hybrid composites

AbstractPolypropylene (PP) hybrid composites have been produced by compounding two types of mineral fillers, viz., talc and kaolin with PP copolymer using a twin screw extruder. The PP hybrid composite was injection‐molded into dumbbell specimen for tensile, flexural, and impact properties characterizations. MFI and SEM studies were used to characterize the flow and morphological properties of the PP hybrid composites. The result shows that most of the hybrid composites showed a significant decrease in flow, tensile, flexural, and impact properties compared with the single filler‐filled PP composites. However, a hybridization effect was seen for the PPT20K10 hybrid composites, through the synergistic coalescence of positive characteristics from 20 wt % of talc and 10 wt % of kaolin. This hybrid formulation have given an economically advantageous material with the mechanical properties (tensile, flexural, and impact) comparable to those of the talc‐filled PP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 434–441, 2007

Injection‐molded short hemp fiber/glass fiber‐reinforced polypropylene hybrid composites—Mechanical, water absorption and thermal properties

AbstractNatural fiber‐based thermoplastic composites are generally lower in strength performance compared to thermoset composites. However, they have the advantage of design flexibility and recycling possibilities. Hybridization with small amounts of synthetic fibers makes these natural fiber composites more suitable for technical applications such as automotive interior parts. Hemp fiber is one of the important lignocellulosic bast fiber and has been used as reinforcement for industrial applications. This study focused on the performance of injection‐molded short hemp fiber and hemp/glass fiber hybrid polypropylene composites. Results showed that hybridization with glass fiber enhanced the performance properties. A value of 101 MPa for flexural strength and 5.5 GPa for the flexural modulus is achieved from a hybrid composite containing 25 wt % of hemp and 15 wt % of glass. Notched Izod impact strength of the hybrid composites exhibited great enhancement (34%). Analysis of fiber length distribution in the composite and fracture surface was performed to study the fiber breakage and fracture mechanism. Thermal properties and resistance to water absorption properties of the hemp fiber composites were improved by hybridization with glass fibers. Overall studies indicated that the short hemp/glass fiber hybrid polypropylene composites are promising candidates for structural applications where high stiffness and thermal resistance is required. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2432–2441, 2007