Mechanical behavior of agro‐residue‐reinforced polypropylene composites

In this research, fully environment‐friendly, sustainable and biodegradable composites were fabricated, using wheat straw and rice husk as reinforcements for thermoplastics, as an alternative to wood fibers. Mechanical properties including tensile, flexural, and impact strength properties were examined as a function of the amount of fiber and coupling agent used. In the sample preparation, three levels of fiber loading (30, 40, and 50 wt %) and two levels of coupling agent content (0 and 2 wt %) were used. As the percentage of fiber loading increased, flexural and tensile properties increased significantly. Notched Izod results showed a decrease in strength as the percentage of fiber increases. With addition of 50% fiber, the impact strengths decreased to 16.3, 14.4, and 16.4 J/m respectively, for wheat straw‐, rice husk‐, and poplar‐filled composites. In general, presence of coupling agent had a great effect on the mechanical strength properties. Wheat straw‐ and rice husk‐filled composites showed an increase in the tensile and flexural properties with the incorporation of the coupling agent. From these results, we can conclude that wheat straw and rice husk fibers can be potentially suitable raw materials for manufacturing biocomposite products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Wood‐thermoplastic composites from wood flour and high‐density polyethylene

High‐density polyethylene/wood flour (HDPE/WF) composites were prepared by a twin‐screw extruder. The effects of WF, silane coupling agents, polymer compatibilizers, and their content on the comprehensive properties of the WF/HDPE composites have been studied in detail, including the mechanical, thermal, and rheological properties and microstructure. The results showed that both silane coupling agents and polymer compatibilizers could improve the interfacial adhesion between WF and HDPE, and further improve the properties of WF/HDPE composites, especially with AX8900 as a compatibilizer giving higher impact strength, and with HDPE‐g‐MAH as a compatibilizer giving the best tensile and flexural properties. The resultant composite has higher strength (tensile strength = 51.03 MPa) and better heat deflection temperature (63.1°C). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Properties of rice husk‐HDPE composites after exposure to thermo‐treatment

Natural fiber reinforced thermo‐plastic composite, with its often‐excellent properties, is well known as a material for external flooring and landscaping. Thermo‐treatment is considered as a method to improve the mechanical properties of these composites; however, oxidation might occur. In this article, thermo‐treatment is applied to a rice husk reinforced high density polyethylene (RH‐HDPE) composite. Variations in the mechanical properties, color, mass, and chemical constituents of the RH‐HDPE composite after thermo‐treatment were investigated. The results indicated that, with the extension of thermo‐treatment time, the color of the composites darkened; the composites underwent a gradual mass loss; during the early stages of thermo‐treatment the composite's flexural properties increased, and then remained stable after 128 h of treatment. Fourier transform infrared (FTIR) spectroscopy analysis showed wood indices of the RH‐HDPE composite decreased, indicating thermo‐degradation occurred during thermo‐treatment. Wide angle X‐ray diffraction (WAXD) results indicated an increased crystallinity of the RH‐HDPE composite in the first 128 h of thermo‐treatment, and increased crystalline grain size in the first 64 h of thermo‐treatment. Appropriate thermo‐treatment is essential to improve the mechanical properties of RH‐HDPE composites. POLYM. COMPOS., 35:2180–2186, 2014. © 2014 Society of Plastics Engineers     

Rice husk/poly(propylene‐co‐ethylene) composites: Effect of different coupling agents on mechanical,thermal, and morphological properties

Poly(propylene‐co‐ethylene) composites with rice husk were prepared in a corotating intermeshing twin‐screw extruder using four different coupling agents. While modified maleic anhydrides such as maleated polypropylene (MAPP) and maleated polyethylene (MAPE) are commonly used as compatibilizers to improve interfacial adhesion between lignocellulosic filler and matrix, in this study, polypropylene grafted with acid comonomer (CAPP) and high‐density polyethylene grafted with acid comonomer (CAPE) were also used. The morphologies and the thermal and mechanical properties of the composites were characterized using scanning electron microscopy, thermogravimetric analysis, differential scanning analysis, tensile and impact tests. The results indicate that the base resin of the compatibilizer is an important factor in determining the effectiveness of compatibilizers for composites. Composites with PP‐based compatibilizers are more effective than PE‐based compatibilizers due to the improved wetting of the former compatibilizer in the matrix polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Development of basalt fiber‐reinforced thermoplastic composites and effect of PE‐g‐MA on composites

The thermoplastic matrix composites have gained great importance in last three decades. The chopped basalt fiber (mineral fiber) is considered to be a good fiber due to excellent properties as potential reinforcement of composite materials. In this work, composites of chopped basalt fiber (6 mm) with thermoplastic material Nylon‐6 (Polyamide‐6) were prepared and its mechanical and morphological properties were evaluated for automobile applications. The melt blending was carried out in corotating twin‐screw extruder and injection‐molded test samples were prepared for the analysis. The test samples of composite without coupling agent prepared by varying the loading of basalt fiber content of 5%, 10%, 15%, 20%, and 25% by weight and with coupling agent composite loading of Nylon‐6 and basalt fiber content were kept constant and the coupling agent (PE‐g‐MA) loading were changed as 1, 2, 3, 4, and 5 phr. The Mechanical and SEM properties were evaluated. From the test results, it was observed that the mechanical properties were improved with increasing coupling agent ratio. SEM images show good dispersion and adhesion of matrix and reinforcement. POLYM. COMPOS., 38:2798–2805, 2017. © 2015 Society of Plastics Engineers     

Use of silanes and copolymers as adhesion promoters in glass fiber/polyethylene composites

Two organofunctional silanes and three functionalized copolymers were used as adhesion promoters in glass fiber/polyethylene‐reinforced composites. The performance of the coupling agents was investigated by mechanical property measurements, scanning electron microscopy, and dynamic mechanical analysis. Coupling achieved with the poly(ethylene‐g‐maleic anhydride) copolymer proved to be the most successful compared with the other copolymers (ethylene/vinyl alcohol, ethylene/acrylic acid) and silane agents (γ‐methacryloxypropyltrimethoxy, cationic styryl). The combined coupling performance of the silanes and copolymers examined in this study appears to be controlled by the coupling performance of the copolymer. Effective coupling was reflected in increased mechanical properties. Increased fiber/matrix adhesion is not always associated with effective coupling because structural changes occurring at the interface region can result in a deterioration of the material property. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2877–2888, 2001     

Improvement of interfacial adhesion of poly(m‐phenylene isophthalamide) short fiber–thermoplastic elastomer (SEBS) composites by N‐alkylation on fiber surface

A composite of short‐fiber, poly(m‐phenylene isophthalamide), and thermoplastic elastomer styrene (ethylene–butylene) styrene (SEBS), was investigated. The fiber surface was modified by N‐alkylation (heptylation and dodecylation) to improve their compatibility with a less polar SEBS matrix. Observation of fiber‐surface morphology by SEM revealed surface roughness after N‐alkylation. Nearly complete coating of the polymer matrix on the fiber was observed on a fractured surface of the composite, which is evidence for the improvement of fiber–matrix adhesion. It was found that the modulus of the composites grew with increasing fiber loading to approximately the same extent for both unmodified and modified fiber composites. Tensile strength of the modified fiber composites was found to improve significantly over that of the unmodified fiber composite. This suggests that the presence of the alkyl group on the fiber surface is responsible for an improvement of interfacial adhesion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2414–2422, 1999     

Water bamboo husk‐reinforced poly(butylene succinate) biodegradable composites

The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the fiber and powder obtained from the water bamboo husk were chemically modified by coupling agents. Furthermore, the modified fiber and powder were added to the biodegradable polymer poly(butylene succinate) (PBS) separately, to form novel fiber‐reinforced composites. Morphologies, mechanical properties, and heat resistance of these water bamboo husk‐reinforced composites were investigated. The results indicate that the fibers modified by coupling agents exhibited better compatibility with the polymer matrixes than did the untreated fibers. Moreover, it is found that the thermal properties were improved as plant fiber was incorporated to those polymers. Furthermore, the mechanical properties were also increased with the addition of coupling agent‐treated fiber. On the other hand, it is found that the homogeneity of untreated powder‐containing samples is better than that of untreated fiber‐containing samples. Moreover, the results reveal that the powders modified with coupling agents were not effective in improving the mechanical properties of the reinforced PBS. This is due to the bulky structure of lignin leading to a smaller reaction ratio with the coupling agents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 188–199, 2006     

Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk

The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry     

A novel polymer composite with double positive‐temperature‐coefficient transitions: effect of filler–matrix interface on the resistivity–temperature behavior

BACKGROUND: Sn–Pb alloy‐filled high‐density polyethylene (HDPE) composites exhibit double positive‐temperature‐coefficient (PTC) behavior, with the first transition at the melting point of HDPE and the second at that of Sn–Pb alloy. The objective of this study is to improve the reversibility and reproducibility of double‐PTC transitions of these composite materials by enhancing the filler–matrix interface. RESULTS: Fourier transform infrared spectroscopy, surface wettability and dynamic mechanical and rheological measurements confirm that surface‐treating Sn–Pb with titanate concentration ≤1 wt% enhances the interface adhesion between Sn–Pb alloy and HDPE matrix. Surface‐treating Sn–Pb with titanate concentration ≤1 wt% increases the PTC transition temperature, reduces the PTC intensity and improves the reversibility and reproducibility of the double‐PTC behavior of Sn–Pb/HDPE composites. CONCLUSION: It is demonstrated that adjusting the filler–matrix interface is an effective means to modify the double‐PTC behavior of Sn–Pb alloy‐filled HDPE composites. Copyright © 2007 Society of Chemical Industry     

Mechanical properties of high‐density polyethylene/scrap rubber powder composites modified with ethylene–propylene–diene terpolymer,dicumyl peroxide,and silicone oil

The effect of ethylene–propylene–diene terpolymer (EPDM), dicumyl peroxide (DCP), and dimethyl silicone oil on the mechanical properties of high‐density polyethylene (HDPE) composites filled with 60 mesh cryogenically scrap rubber powder (SRP) was studied. The addition of 10 wt % EPDM, 0.2 wt % DCP, and 4 wt % dimethyl silicone oil significantly increased both the impact strength and elongation at break of the HDPE/SRP composites. After the modification, the impact strength increased by 160%, and the elongation at break increased by 150% for the composites containing 40 wt % SRP. The impact load–time curves showed that the increase of impact energy for the modified composites was attributed to the increase of the maximum force at yield point and the ductile deformation after yielding. The rheological behavior, dynamic mechanical properties, and morphology observation suggested that an enhanced adhesion between SRP and polymer matrix formed in the modified HDPE/SRP composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2020–2027, 2003     

Deformation and fracture of Mg(OH)2‐filled polyolefin composites under tensile stress

The tensile behavior of high‐density polyethylene (HDPE), polypropylene (PP), and linear low‐density polyethylene composites containing a titanate coupling agent and silicone‐oil‐treated magnesium hydroxide [Mg(OH)₂] was studied. The increase in the extent of the ultimate elongation of the composites was affected by the yield stress and the strain‐hardening tendency of the polymer matrix in the composites. Ethylene–propylene–diene rubber and octane–ethylene copolymer were introduced to adjust the yield stress of PP and HDPE. Although the ultimate elongation of PP/elastomer and HDPE/elastomer blends was higher than that of virgin PP or HDPE, the ultimate elongation of the filled composites dropped at a high content of Mg(OH)₂. Scanning electron microscopy showed that the difference in the uniformity of the interface exfoliation decreased with the yield stress of the matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3248–3255, 2003     

HDPE/稻糠复合材料性能研究

研究了稻糠表面处理方法、稻糠含量、HDPE回收料用量等对HDPE／稻糠复合材料物理性能的影响规律。结果表明,采用常规偶联剂处理稻糠时,对HDPE／稻糠复合材料的改性效果较差;在制备HDPE木塑复合材料时,稻糠与松木粉的应用效果相近;同时,应根据材料的使用性能要求,严格控制稻糠用量和HDPE回收料的用量。     

Behavior of polyolefin blends with acetylated sisal fibers

The influence of acetylation on the mechanical, thermal and thermodegradative behavior of sisal fiber‐reinforced PP, PP/HDPE and PP/HDPE with functionalized and non‐functionalized EPR composites was studied. Acetylation of the fiber improves adhesion of the fiber to the polyolefin matrix. In general, acetylation of the sisal fiber was found to enhance the tensile strength and modulus of the resulting composites, except in some cases. Thermal properties suggest that the mixing and molding temperatures are between 160 and 230 °C and that when acetylated fiber is mixed with polyolefins, greater polymer‐fiber interactions takes place, which slightly favor stability of these composite materials. The results allow us to suggest that a satisfactory profit/cost relation justifies the addition of acetylated fiber to PP, PP/HDPE, and PP/HDPE/EPR. © 2000 Society of Chemical Industry     

Effects of rice straw fiber morphology and content on the mechanical and thermal properties of rice straw fiber‐high density polyethylene composites

Rice straw fiber‐high density polyethylene (HDPE) composites were prepared to investigate the effects of rice straw fiber morphology (rice straw refined fiber, rice straw pellet, rice straw strand), fiber content (20 and 40 wt %), and maleic anhydride polyethylene (MAPE) concentration (5 wt %) on the mechanical and thermal properties of the rice straw fiber‐HDPE composites in this study. Rice straw refined fiber exhibited more variability in length and width, and have a higher aspect ratio of 16.3. Compared to the composites filled of rice straw pellet, the composites made of the refined fiber and strand had a slightly higher tensile strength and lower tensile elongation at break. The tensile and flexural strength of the composites increased slightly with increasing rice straw fiber content up to 40 wt %, while the tensile elongation at break decreased. With addition MAPE, the composites filled with 20 wt % rice straw fiber showed an increase in tensile, flexural and impact strength and a decrease in tensile elongation at break. Differential scanning calorimetry showed that the fiber addition and morphology had no appreciable effect on the crystallization temperature of the composites but decreased the crystallinity. The scanning electron microscopy observation on the fracture surface of the composites indicated that introduction of MAPE to the system resulted in promotion in fiber dispersion, and an increase in interfacial bonding strength. Fiber breakage occurred significantly in the composites filled with refined fiber and strand after extruding and injection processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of toughening agents on the behaviors of bamboo plastic composites

Three kinds of reactive toughening agents of bamboo plastic composites are studied in this article. The bio‐fiber keeps high polarity for the hydroxyl groups of the surface, while polypropylene (PP) matrix resin phase is nonpolar. So, the interfacial compatibility between matrix and enhanced phase is poor. The anhydride in maleic anhydride grafted polypropylene can react with the hydroxyls. A large number of hydroxyl groups on the fiber surface are reduced, and the interfacial bond strength is improved. Three reactive toughening agents: glycidyl methacrylate grafted poly(ethylene‐1‐octene), maleic anhydride grafted poly(ethylene‐octene), and poly(ethylene‐butylacrylate‐glycidyl methacrylate) are chosen to improve the impact toughness. The mechanical properties, compatibility, phase structure, water absorption, and thermal properties of PP blends are all investigated. When the content of toughening agents are controlled between 6% and 8%, not only the impact strength is greatly improved but also the other properties of PP are less affected, which makes the composites with comprehensive and practical applications. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Morphological and physicomechanical analysis of high‐density polyethylene filled with Salago fiber

The environmental issues associated with the mass discarding of waste plastics in the Philippines have significantly raised for the past decade. However, this country is a home to many natural fibers which necessitates the development of ecofriendly materials to diminish the environmental footprint of polymers. High‐density polyethylene (HDPE) was filled with floured untreated and 5 wt % alkaline‐treated Salago fiber via melt compounding. The physical and mechanical characteristics of both types of composites were measured and compared. The composite filled with 30 wt % untreated fiber became very brittle, showing tensile strength and impact resistance of 15.8 MPa and 4.9 kJ/m², respectively. Alkaline treatment improved the mechanical properties of untreated composites, but not above the value of virgin HDPE. Nevertheless, the flexural strength of treated composites exceeded that of the virgin HDPE. Untreated composites absorbed water twice as the treated ones. Finally, morphological and fractography inspection on tensile and flexural test specimens showed improvement made by treatment on the interfacial adhesion between fiber and thermoplastic, corroborating the results from mechanical properties test. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46479.     

Preparation and characterization of poly(ethylene terephthalate) powder‐filled high‐density polyethylene in the presence of silane coupling agents

Micron‐size crystalline particles of Poly(ethylene terephthalate) (PET), obtained from PET bottles by crystallization and grinding, were used as a filler in high‐density polyethylene (HDPE). The composite of PET particle‐filled HDPE was prepared by melt mixing at 190°C, which was well below the melting temperature of PET. Silane coupling agents (SCAs) were used to enhance the interaction between PET and HDPE in the composite. A chain extender (CE) and maleic anhydride (MA) were also used to provide further interaction with SCAs between these two materials. The ultimate tensile strength, especially at highest content 40% PET‐filled HDPE, and the impact strength of SCAs‐treated PET‐filled HDPE was found to be highly improved compared to untreated PET filling into HDPE. Dynamic mechanical analyses (DMA) demonstrated that T_g of the main matrix polyethylene was depressed from 3 to 10°C. Scanning electron microscopy (SEM) studies indicated a strong interaction between PET powder and HDPE when SCAs were present in the system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 827–835, 2001     

Effect of silane-based coupling agents and acrylic acid based compatibilizers on mechanical properties of oil palm empty fruit bunch filled high-density polyethylene composites

The mechanical properties of composites consisting of high-density polyethylene (HDPE) and oil palm fibrous wastes—that is, empty fruit bunch (EFB)—have been investigated. Tensile modulus showed an increase, whereas tensile strength, elongation at break, and impact strength decreased with increasing filler loading. The strong tendency of EFB to exist in the form of fiber bundles and the poor filler–matrix interaction is believed to be responsible for the poor strength displayed by the composites. Attempts to improve these properties using two types of coupling agents, that is, 3-aminopropyltrimethoxysilane (3-APM) and 3-aminopropyltriethoxysilane (3-APE) and two types of compatibilizers, poly(propylene–acrylic acid) (PPAA) and poly(propylene–ethylene–acrylic acid), (PPEAA), are described. While almost all chemical treatments increased the stiffness of the composites, limited improvement has been observed in the case of tensile strength. This have been attributed to the presence of fiber bundles that remain intact even after several types of chemical treatment have been carried out. Thus, the role of EFB as reinforcing agent is not fully realized. Scanning electron microscopy (SEM) micrographs revealed that the main energy-absorbing mechanisms contributing towards toughness enhancement is through the fiber bundle pull-out process. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2189–2203, 1998     

Novel coupling agents for PVC/wood‐flour composites *

Effective interfacial adhesion between wood fibers and plastics is crucial for both the processing and ultimate performance of wood–plastic composites. Coupling agents are added to wood–plastic composites to promote adhesion between the hydrophilic wood surface and hydrophobic polymer matrix, but to date no coupling agent has been reported for PVC/wood‐fiber composites that significantly improved their performance and was also cost‐effective. This article presents the results of a study using chitin and chitosan, two natural polymers, as novel coupling agents for PVC/wood‐flour composites. Addition of chitin and chitosan coupling agents to PVC/wood‐flour composites increased their flexural strength by ～20%, their flexural modulus by ～16%, and their storage modulus by ～33–74% compared to PVC/wood‐flour composite without the coupling agent. Significant improvement in composite performance was attained with 0.5 wt% of chitosan and when 6.67 wt% of chitin was used. J. VINYL ADDIT. TECHNOL., 11:160–165, 2005. © 2005 Society of Plastics Engineers