Investigation on the use of coir fiber as alternative reinforcement in polypropylene

Polypropylene/coir fiber composites were prepared according to an experimental statistical design, in which the independent variables, coir fiber, and compatibilizer content, were varied. The compatibilizer used was maleic anhydride grafted polypropylene (PP‐g‐MA). Compatibilizer free composites were also prepared. Composites were processed in a corotating twin‐screw extruder and submitted to mechanical and morphological analyses. The effects of the independent variables on the mechanical properties were assessed through tensile strength, elongation at break, flexural modulus, and impact strength. The morphological properties were assessed by scanning electron microscopy (SEM). The results indicated the need for using compatibilizers in the composites due to the incompatibility of PP and coir fiber. The variable with the strongest effect on the properties was coir content, whose increase caused increase in tensile strength, impact strength and elastic modulus, and decrease in elongation at break. The presence of PP‐g‐MA was fundamental to achieving the aforementioned results. The effect of increasing compatibilizer content was only observed for the elastic modulus. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fatigue life of coir fiber reinforced PP composites: Effect of compatibilizer and coir fiber contents

The fatigue behavior of polypropylene/coir fiber composites was investigated. Composites were prepared according to an experimental statistical design, in which the independent variables coir fiber and compatibilizer content were varied. The compatibilizer used was maleic anhydride grafted polypropylene (PP‐g‐MA). Compatibilizer free composites were also prepared. Composites were prepared in a corotating twin‐screw extruder and the mechanical behavior of polypropylene/coir fiber composites were assessed through monotonic (tensile) and cyclic (fatigue) tests. Fatigue load controlled tests were conducted under tension–tension loads at a frequency of 6 Hz. The fracture mechanism was accompanied by surface fracture analyses using scanning electron microscopy (SEM). The results indicated the need for using compatibilizer in the composites; however, increase in compatibilizer content did not affect composite fatigue lifetime. Coir content was the variable with the strongest effect on composite properties; increasing this variable caused significant increase in fatigue life. POLYM. ENG. SCI., 53:2159–2165, 2013. © 2013 Society of Plastics Engineers     

聚丙烯/麦秸秆木塑复合材料的力学性能

采用转矩流变仪混合造粒,通过注射成型方法制备了聚丙烯(PP)/麦秸秆木塑复合材料,研究了NaOH浓度、增容剂的含量和麦秸秆含量对PP/麦秸秆木塑复合材料力学性能的影响,采用扫描电子显微镜对麦秸秆表面及复合材料的断面形貌进行分析。结果表明:8%NaOH溶液处理麦秸秆时,PP/麦秸秆木塑复合材料的拉伸强度、弯曲强度和冲击强度达到最大;马来酸酐接枝PP增容剂的加入使得麦秸秆与PP的界面相容性提高,复合材料的力学性能增加;在一定范围内麦秸秆的添加降低了PP材料的拉伸强度和冲击强度,而提高了其弯曲强度,并且PP/麦秸秆复合材料的弯曲强度随着麦秸秆含量的增加而增加,在麦秸秆含量为30%时弯曲强度达到最大值为43.4 MPa。     

Evaluation of interactions between compatibilizers and photostabilizers in coir fiber reinforced polypropylene composites

Coir fiber‐reinforced polypropylene composites (PP/CF), compatibilized with maleic anhydride grafted polypropylene (PPMAH) and stabilized with a hindered amine, HALS (Tinuvin^® 791) and UV absorber (Hostavin^® ARO 8), were prepared in a co‐rotating twin‐screw extruder. The effects of additives and their interactions were investigated by analyzing the mechanical properties, in tensile strength, scanning electron microscopy (SEM) and Differential Scanning Calorimetry (DSC). The results indicate that the incorporation of coir, in the presence of the compatibilizer, significantly increases tensile strength, but in the absence of the compatibilizer, the natural fibers act as stress concentrators, allowing a lower tensile strength to the sample. The joint presence of Tinuvin^® and the compatibilizer has a negative effect on tensile strength and on the compatibility of the natural fiber with the matrix. UV absorber does not affect the compatibility of the PP/CF composites. POLYM. ENG. SCI., 57:1179–1185, 2017. © 2017 Society of Plastics Engineers     

Isolation and characterization of betel nut leaf fiber: Its potential application in making composites

Betel nut leaf fiber (BNLF) is a new finding as cellulosic filler for polymer composites. Its main constituents are 75% α‐cellulose, 12% hemicelluloses, 10% lignin, and 3% others matter, viscosity average molecular weight 132,000 and degree of crystallinity 70%. In the present work, BNLF reinforced polypropylene (PP) composites were prepared using heat press molding method. 5–20 wt% short length fiber is taken for getting benefits of easy manufacturing and the fiber was chemically treated with NaOH, dicumyl peroxide (DCP), and maleic anhydride‐modified PP (MAPP) to promote the interfacial bond with PP. The extent of modification of fiber was assessed on the basis of morphology, bulk density, moisture absorption, thermal, and mechanical properties of untreated fiber, treated fiber, and their reinforcing PP composites. The tensile and flexural strength of composites increase with the increase of fiber loading up to 10 and 20 wt%, respectively. It was also observed that Young's modulus and flexural modulus increase with fiber loading. The thermal degradation behavior of resulting composites was investigated. Among the various treated fibers, MAPP‐treated fiber composite showed best interfacial interactions as well as mechanical and thermal properties. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Structure-property relationships of short fiber reinforced polypropylene-polyamide blends

Short fiber composites based on polypropylene (PP)-polyamide (PA) blends were studied using compatibilizers comprising maleic anhydride modified polypropylene. Results have shown that the structure and morphology developed and the resultant mechanical properties of the blend composites strongly depend on the number of acid functional groups in the compatibilizers. The impact strength and tensile modulus of the PP-PA blend composite more than doubled compared with PA and PP short fiber composites, respectively. Furthermore, analytical methods characterizing nonisothermal crystallization were used to investigate the crystallization of fiber containing blends in constrained matrix nucleation mode. Results have shown that interphase interactions are the dominant ones with respect to morphology development. Synergistic effects were obtained that were due to the effect of fibers.     

高强高韧GF／PP复合材料的研究

通过在短玻(GF)增强聚丙烯(PP)中添加聚烯烃弹性体(POE),并用马来酸酐对PP进行接枝交联的方法, 制备了高冲击韧性GF／PP复合材料。在该材料中,短切玻璃纤维的加入大幅度提高了材料的拉伸、弯曲强度,而POE 则通过产生形变等方式,提高了材料的冲击韧性;在其中加入马来酸酐接枝聚丙烯增加界面结合力,可使GF／PP／POE 复合体系表现出良好的综合力学性能,其拉伸强度为51．9 MPa,弯曲强度为68．1MPa,冲击韧性为44．2 kJ／m2。     

Polypropylene‐organoclay nanocomposite: Preparation,microstructure, and mechanical properties

A series of polypropylene (PP) nanocomposites containing 2, 4, and 6 wt % of an organophilic montmorillonite clay was prepared via direct melt mixing in the presence of maleic anhydride grafted polypropylene (PP‐g‐MAH) as compatibilizing agent. Microstructure characterization was performed by X‐ray diffraction analysis. Nanocomposites exhibited a 15 and 22% enhancement in tensile modulus and impact strength, respectively. The heat deflection temperature of PP nanocomposites was 36°C greater than for pure PP. Thermal and mechanical properties of nanocomposites were compared to properties of traditional PP‐talc and PP‐glass fiber composites. The results showed that the properties of nanocomposites improved compared to ordinary polypropylene composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

玻璃纤维增强聚丙烯的力学性能研究

研究了玻璃纤维(GF)和马来酸酐接枝聚丙烯(PP-g-MAH)对聚丙烯力学性能的影响。结果表明:随着GF与PP的质量比增加,玻璃纤维增强聚丙烯的拉伸强度增加,冲击强度总体呈下降趋势。当PP与GF的质量比为55∶45时,拉伸强度最高,达到45MPa。当PP与GF的质量比一定时,在玻璃纤维增强聚丙烯复合材料中添加增容剂马来酸酐接枝聚丙烯(PP-g-MAH),可使其拉伸强度得到很大的提高,但是冲击性能却下降。当PP与GF的质量比为75∶25时,随PP-g-MAH与PP/GF复合材料的质量比增加,其拉伸强度先增大后减小,其冲击性能总体呈下降趋势。当PP-g-MAH,PP和GF的质量比为15∶75∶25时,其综合性能最优,拉伸强度为50.5MPa,冲击强度为4.3kJ/m2。     

Preparation and characterization of polypropylene composites reinforced with chemically treated coir

In the present work chemically treated coir reinforced polypropylene composites were fabricated by injection molding method. Raw coir was chemically treated by a simple two-step reaction. The mechanical properties of the treated coir reinforced polypropylene (PP) composites were found to be much improved compared to the corresponding values of the untreated ones. Water absorption of the composites increased with an increase in fiber content. However, treated coir-PP composites showed lower water uptake capacity compared to those prepared from untreated coir, indicating that upon chemical treatment the number of hydroxyl groups in the cellulose of coir has decreased, giving reduced the hydrophilic nature of the fiber. The surface morphology of the composites obtained from scanning electron microscopy (SEM) showed that raw coir-PP composites possess microvoids, fiber agglomerates and surface roughness with extruded fiber moieties. However, due to favorable interaction between the treated coir and the PP matrix, agglomerates and micro-voids in the composites have largely minimized showing better dispersion of the fiber in the matrix. It was concluded that upon surface modification hydrophilic nature of coir has largely minimized, giving better fiber-matrix interfacial adhesion and improved mechanical properties of the composites.     

聚丙烯/马来酸酐接枝聚丙烯/环氧树脂/玻璃纤维复合材料的制备及其性能研究

通过双螺杆挤出机制备了聚丙烯/马来酸酐接枝聚丙烯/环氧树脂/玻璃纤维（PP/PP-g-MAH/EP/GF）复合材料,并研究了PP-g-MAH含量、EP含量及固化剂对复合材料力学性能的影响。结果表明,PP-g-MAH含量为10份,含有固化剂EP的含量为3份时,复合材料的综合力学性能最佳;与不加EP的复合材料相比,其拉伸强度、弯曲强度、冲击强度分别提高了41 %、47 %、86 %。扫描电子显微镜分析表明,EP的加入明显改善了GF和PP基体的黏结强度。     

Flax fiber surface modifications: Effects on fiber physico mechanical and flax/polypropylene interface properties

This study arises on the opportunities of using flax fibers as reinforcement for polypropylene (PP) matrix composites. For this purpose, untreated flax fiber bundles obtained by a retting process have been used. For improving compatibility between flax fiber bundles and PP matrix, fiber surface treatments such as maleic anhydride, maleic anhydride polypropylene copolymer, and vinyltrimethoxy silane have been carried out. On the other hand, alkali treatment has also been carried out for fiber modification. The effect of surface modification on tensile properties of single fibers and also on fiber‐matrix interfacial shear strength (IFSS) has been analyzed. Finally, both optical microscopy and atomic force microscopy have been used for characterizing flax fiber microstructural features. The current study completes previous results to elucidate the influence of treatments on fiber surface and flax fiber‐PP interface. POLYM. COMPOS. 26:324–332, 2005. © 2005 Society of Plastics Engineers.     

Influence of interfacial adhesion on the structural and mechanical behavior of PP‐banana/glass hybrid composites

Hybrid composites of polypropylene (PP), reinforced with short banana and glass fibers were fabricated using Haake torque rheocord followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both fibers into PP matrix resulted in increase of tensile strength, flexural strength, and impact strength upto 30 wt% with an optimum strength observed at 2 wt% MAPP treated 15 wt% banana and 15 wt% glass fiber. The rate of water absorption for the hybrid composites was 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 been analyzed to investigate the interfacial properties. An increase in storage modulus (E′) of the treated‐composite indicates higher stiffness. The loss tangent (tan δ) spectra confirms a strong influence of fiber loading and coupling agent concentration on the α and β relaxation process 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 through differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA), indicated an increase in the crystallization temperature and thermal stability of PP with the incorporation of MAPP‐treated banana and glass fiber. POLYM. COMPOS., 31:1247–1257, 2010. © 2009 Society of Plastics Engineers     

An investigation of the interfacial adhesion between reclaimed newspaper and recycled polypropylene composites through the investigation of their mechanical properties

The effects of different parameters (e.g. method of defibration of newspaper; size of the fiber; type and concentrations of coupling agents, impact modifiers, and fire retardants) on the mechanical properties of old newspaper fiber-filled recycled polypropylene (PP) have been evaluated. Statistical methods were applied to determine the effects of variables on the tensile strength, Young's modulus, tensile toughness, and impact strength. Statistical analysis revealed that the composites based on newspaper fiber prepared by mechanical defibration showed a better tensile strength compared with those prepared by the steam explosion process, while the latter type of fiber outperformed the former as far as the other mechanical properties are concerned. In the presence of maleic anhydride grafted PP (MPP) and the initiator dicumyl peroxide (DCPO), the tensile strength of the composites increased with increasing fiber loading and fiber size. Moreover, both the tensile strength and the modulus increased with an increase in the concentrations of MPP and DCPO, even in the presence of an impact modifier and fire retardants for surface-modified newspaper-filled composites. Since the tensile strength of short fiber reinforced composites is strongly dependent of the degree of adhesion between the fiber and matrix, the experimental results suggest that either one of these (MPP and DCPO) or both act as the interfacial bonding agent to develop a strong interphase between old newspaper fiber and recycled PP.     

剑麻纤维增强聚丙烯复合材料的制备及性能研究

制备了剑麻纤维增强聚丙烯（PP）复合材料,考察了纤维含量及马来酸酐接枝PP（MPP）增容剂对复合材料孔隙率及力学性能的影响,并采用修正的数学模型分别对复合材料的拉伸强度和拉伸弹性模量进行预测。结果表明,随着纤维含量的增加,复合材料的孔隙率先增大后减小,纤维质量分数为30％时孔隙率达到最大值。未添加MPP增容剂时,复合材料的拉伸及弯曲性能在纤维质量分数小于30％时变化幅度较小,40％时则有较大幅度提高;冲击强度随着纤维含量增加而提高。当添加MPP增容剂时,复合材料的力学性能随纤维含量的增加而提高。拉伸性能的预测结果与实测结果比较一致。     

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.     

Injection molding of long sisal fiber–reinforced polypropylene: Effects of compatibilizer concentration and viscosity on fiber adhesion and thermal degradation

A two‐step process was used to obtain long sisal fiber‐polypropylene (SF/PP)–reinforced thermoplastic composites, using maleic anhydride grafted polypropylene (MA‐g‐PP) as a compatibilizer. At a first stage, modified polypropylenes (mPP) were used for an extrusion impregnation process, for the preparation of composite pellets containing about 70 wt% of SF. SF/mPP pellets with a large aspect ratio were prepared by continuous extrusion impregnation of a continuous SF yarn, using a single screw extruder and an adequate impregnation die. The mPP used were MA‐g‐PP and regular polypropylene (PP), modified by reaction with different amounts of an organic peroxide. The composite pellets were thus dry blended with regular PP pellets in an injection machine hopper, and injection molded to obtain composite tensile specimens with a minimum quantity of modified polypropylene, minimum fiber breakage and thermal degradation, and excellent mechanical properties. It is shown that the fiber breakage is reduced to a minimum, even for recycled composites, due to the presence of the low‐viscosity polymer layer wetting the SF fibers. The bulk composite effective viscosity and the fiber breakage extent and thermal degradation during the injection‐molding step are found to be closely related. Blending with much less expensive mPP at the impregnation stage optimizes the amount of expensive MA‐g‐PP. POLYM. ENG. SCI., 45:613–621, 2005. © 2005 Society of Plastics Engineers     

Effect of coir fiber loading on mechanical and morphological properties of oil palm fibers reinforced polypropylene composites

Hybrid composites were fabricated by compounding process with varying the relative weight fraction of oil palm empty fruit bunch (EFB) and coir fibers to assess the effect of hybridization of oil palm EFB with coir fibers in polypropylene (PP) matrix. The mechanical and morphological properties of oil palm/coir hybrid composites were carried out. Tensile and flexural properties of oil EFB‐PP composites enhanced with hybridization of coir fibers except coir/oil palm EFB (25:75) hybrid composite, whereas highest impact properties at oil palm:coir fibers with 50:50 ratios. Results shown that hybrid composites with oil palm:coir fibers with 50:50 ratios display optimum mechanical properties. In this study, scanning electron microscopy (SEM) had been used to study morphology of tensile fractured surface of hybrid composites. Its clear from SEM micrograph that coir/EFB (50:50) hybrid composites display better tensile properties due to strong fiber/matrix bonding as compared with other formulations which lead to even and effective distribution of stress among fibers. The combination of oil palm EFB/coir fibers with PP matrix produced hybrid biocomposites material can be used to produce components such as rear mirrors' holder and window levers, fan blades, mallet, or gavel. POLYM. COMPOS., 35:1418–1425, 2014. © 2013 Society of Plastics Engineers     

Effects of wheat straw fiber content and characteristics,and coupling agent concentration on the mechanical properties of wheat straw fiber‐polypropylene composites

Wheat straw fiber‐polypropylene (PP) composites were prepared to investigate the effects of wheat straw fiber content (10, 20, 30, 40, and 50 wt %), fiber size (9, 28, and 35 mesh), and maleic anhydride grafted polypropylene (MAPP) concentration (1, 2, 5, and 10 wt %) on the static and dynamic mechanical properties of the wheat straw fiber‐PP composites in this study. The tensile modulus and strength of the composites increased linearly with increasing wheat straw fiber content up to 40%, whereas the elongation at break decreased dramatically to 3.78%. Compared with the composites made of the longer wheat straw fiber, the composites made of the fines (>35 mesh) had a slightly higher tensile strength of 31.2 MPa and tensile elongation of 5.39% at break. With increasing MAPP concentration, the composites showed an increase in tensile strength, and the highest tensile strength of 34.0 MPa occurred when the MAPP concentration reached 10 wt %. As wheat straw fiber content increased from 0 to 40%, the flexural modulus of the composites increased gradually from 1335 to 3437 MPa. The MAPP concentration and wheat straw fiber size distribution had no appreciable effect on the static flexural modulus of the composites. The storage flexural modulus of the composites increased with increasing wheat straw fiber content. The scanning electron microscopy (SEM) observation on the fracture surface of the composites indicated that a high wheat straw fiber content (>30 wt %) resulted in fiber agglomeration and a reduction in interfacial bonding strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009