The influence of chemical surface modification on the performance of sisal‐polyester biocomposites

This article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.     

Influence of fiber surface treatment on the properties of sisal-polyester composites

The effect of several chemical treatments, viz. organotitanate, zirconate, silane, and N-substituted methacrylamide, on the properties of sisal fibers used as reinforcement in unsaturated polyester resin (∼50 vol%) was investigated. An improvement in the properties was observed when sisal fibers were modified with surface treatments. Under humid conditions, a decrease of 30 to 44% in tensile and 50 to 70% in flexural strength has been noted. The strength retention of surface-treated composites (except silane) is high compared with untreated composites. It is observed that N-substituted methacrylamide-treated sisal composites exhibited better properties under dry as well as wet conditions. Fractographic evidence such as fiber breakage/splitting and matrix adherence on the pulled-out fiber surface explains such behavior.     

表面处理对剑麻纤维布/不饱和树脂材料性能影响

采用碱、高锰酸钾及热对剑麻纤维布进行了表面处理,并由真空辅助树脂传递模塑成型(VARTM)工艺制备了剑麻纤维布增强不饱和聚酯树脂复合材料。通过对复合材料的力学性能及吸水性的测试,研究了不同剑麻纤维布表面处理对其不饱和聚酯树脂复合材料性能的影响。结果表明:经过碱处理,复合材料的拉伸、弯曲,冲击强度提高最大,可分别提高26.5%,16.5%和22.6%,吸水率降低了47.5%。对剑麻纤维布进行表面处理可使复合材料的界面性能得到改善,力学性能提高,吸水性降低。     

A study of the mechanical properties of randomly oriented short banana and sisal hybrid fiber reinforced polyester composites

The mechanical performance of short randomly oriented banana and sisal hybrid fiber reinforced polyester composites was investigated with reference to the relative volume fraction of the two fibers at a constant total fiber loading of 0.40 volume fraction (V_f), keeping banana as the skin material and sisal as the core material. A positive hybrid effect is observed in the flexural strength and flexural modulus of the hybrid composites. The tensile strength of the composites showed a positive hybrid effect when the relative volume fraction of the two fibers was varied, and maximum tensile strength was found to be in the hybrid composite having a ratio of banana and sisal 4 : 1. The impact strength of the composites was increased with increasing volume fraction of sisal. However, a negative hybrid effect is observed when the impact strength of the composites is considered. Keeping the relative volume fraction of the two fibers constant, that is, banana : sisal = 0.32 : 0.08 (i.e., 4 : 1), the fiber loading was optimized and different layering patterns were investigated. The impact strength of the composites was increased with fiber loading. Tensile and flexural properties were found to be better at 0.40 V_f. In the case of different layering patterns, the highest flexural strength was observed for the bilayer composites. Compared to other composites, the tensile properties were slightly higher for the composite having banana as the skin material and sisal as the core material. Scanning electron micrographs of the tensile and impact fracture surfaces of the hybrid composites having volume fraction 0.20 and 0.40 V_f were studied. The experimental tensile strength and tensile modulus of hybrid composites were compared with those of theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1699–1709, 2005     

不饱和聚酯树脂/大麻纤维复合材料性能的研究

采用模压工艺制备了不饱和聚酯(UP)树脂/大麻纤维复合材料,研究了大麻纤维加入量及纤维的碱处理、乙酰化处理及偶联剂处理对复合材料力学性能的影响;采用傅立叶变换红外光谱仪对复合材料的结构进行了表征和分析。结果表明,随着大麻纤维含量的增加,UP树脂/大麻纤维复合材料的拉伸弹性模量逐渐增加,拉伸强度、弯曲强度、弯曲弹性模量及冲击强度等均先降低而后逐渐增大;偶联剂处理对复合材料力学性能的改善效果最好;偶联剂与纤维之间发生了酯化反应。     

阻燃香蕉纤维增强聚乳酸复合材料的制备与表征

采用乙酰柠檬酸三丁酯(ATBC)作为增塑剂增塑聚乳酸,添加改性香蕉纤维和膨胀型阻燃剂(IFR)制备阻燃香蕉纤维增强聚乳酸复合材料.研究结果表明,偶联剂处理纤维的效果最好,使复合材料的拉伸、弯曲强度分别达到57.49MPa、101.80MPa,与扫描电子显微镜(SEM)的结果一致;IFR含量为5份(以聚乳酸为100份计)时综合性能最佳,材料的极限氧指数达到了 32.8%,垂直燃烧实验达到了 V-0 级(UL-94),材料的拉伸和弯曲强度分别为43.97 MPa 和87.95MPa,效果最好.热失重研究结果表明,阻燃香蕉纤维的加入能明显提高聚乳酸的热分解温度和残炭量.     

Influence of Fiber Surface Modification on the Mechanical Performance of Isora-Polyester Composites

This paper reports the effect of chemical treatment on the mechanical properties of a natural fiber, isora, as reinforcement in unsaturated polyester resin. Isora fiber is separated from the bark of the Helicteres isora plant by a retting process. The short isora fiber surface was modified chemically by acetylation, benzoylation, silane and triton treatments to bring about improved interfacial interaction between the fiber and the polyester matrix. The modified surfaces were characterized by IR spectroscopy and SEM. The SEM studies were carried out to investigate the fiber surface morphology, fiber pull-out and fiber-polyester interface bonding. They showed the changes occuring on the fiber surface during chemical treatment. Properties like tensile strength, flexural strength and impact strength have been studied. The chemical modification of fiber improved fiber/matrix interaction as evidenced by the enhanced tensile and flexural properties. The lower impact properties of the composites, except triton-treated fiber composite, further point to the improved fiber/matrix adhesion, compared to the untreated fiber composites.     

Effect of interface modification on the mechanical properties of polystyrene‐sisal fiber composites

The effect of interface modification on the mechanical (tensile, impact and flexural) properties of polystyrene–sisal fiber composites was investigated. The interface modification was performed by treatment of sisal fibers with benzoyl chloride, polystyrene maleic anhydride (PSMA), toluene diisocyanate (TDI), methyl triethoxy silane and triethoxy octyl silane. These interface modifications improve the compatibility of hydrophilic sisal fiber with a hydrophobic polystyrene matrix and change the tensile, impact and flexural properties of the composite, but to varying degrees depending on the fiber modification. The treated fibers were analyzed by spectroscopic techniques. Scanning electron microscopy was used to investigate the fiber surface, fiber pullout, and fiber‐matrix interface.     

Plant oil‐based biofoam composites with balanced performance

BACKGROUND: Biofoam composites were prepared using short sisal fibers as reinforcement and acrylated epoxidized soybean oil as matrix, aiming at replacing traditional unsaturated polyester foams in structural applications. The compressive properties of the composites were examined as a function of fiber loading, fiber length and foam density. RESULTS: The foam composite with 10 phr (parts per hundred of base resin by weight) sisal fiber possessed properties similar to those of commercial unsaturated polyester foams. A study of the failure mechanism revealed that debonding between fiber and matrix was a key issue responsible for catastrophic damage of the composites. According to this finding, surface pre‐treatment of the sisal using an alkali or silane coupling agent was carried out. This brought about positive effects on interfacial interaction and compressive strength of the composites, as desired. Also, soil burial tests proved that the foam composites could be biodegraded, and the incorporated sisal fibers accelerated the biodegradation of the composites. CONCLUSION: This work shows the feasibility of making rigid biofoams from natural resources, which could be potential candidates for structural foams. Copyright © 2009 Society of Chemical Industry     

Mechanical properties of pineapple leaf fiber-reinforced polyester composites

Pineapple leaf fiber (PALF) which is rich in cellulose, relatively inexpensive, and abundantly available has the potential for polymer reinforcement. The present study investigated the tensile, flexural, and impact behavior of PALF-reinforced polyester composites as a function of fiber loading, fiber length, and fiber surface modification. The tensile strength and Young's modulus of the composites were found to increase with fiber content in accordance with the rule of mixtures. The elongation at break of the composites exhibits an increase by the introduction of fiber. The mechanical properties are optimum at a fiber length of 30 mm. The flexural stiffness and flexural strength of the composites with a 30% fiber weight fraction are 2.76 GPa and 80.2 MPa, respectively. The specific flexural stiffness of the composite is about 2.3 times greater than that of neat polyester resin. The work of fracture (impact strength) of the composite with 30% fiber content was found to be 24 kJ m⁻². Significant improvement in the tensile strength was observed for composites with silane A172-treated fibers. Scanning electron microscopic studies were carried out to understand the fiber-matrix adhesion, fiber breakage, and failure topography. The PALF polyester composites possess superior mechanical properties compared to other cellulose-based natural fiber composites. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1739–1748, 1997     

表面处理方法对剑麻纤维/酚醛树脂复合材料性能的影响

分别采用碱、硅烷偶联剂、阻燃剂对剑麻纤维(SF)进行表面处理,采用模压成型工艺制备了SF/酚醛树脂(PF)复合材料。研究了SF表面处理方法对SF/PF复合材料的摩擦磨损性能、力学性能、吸水性的影响,借助扫描电镜观察了复合材料磨损面的形貌。结果表明:SF经阻燃剂处理后,SF/PF复合材料的磨损体积为0.00053cm3,比未处理的SF/PF复合材料减少了77.2%;SF经硅烷偶联剂处理后,SF/PF复合材料的冲击强度、弯曲强度分别比未处理的SF/PF复合材料提高18.7%、15.4%,且耐水性也有一定改善。     

黄麻纤维增强不饱和聚酯树脂初步研究

以油酸为偶联剂,将氢氧化钠-油酸处理后的黄麻纤维布作为填充材料制备了不饱和聚酯复合材料,并对氢氧化钠处理黄麻纤维的适宜浓度、复合材料的拉伸强度、冲击强度、吸水率进行了研究测试。结果表明:氢氧化钠的适宜浓度为20%,黄麻纤维增强不饱和聚酯树脂的冲击强度及拉伸强度最大值分别为12.75 kJ/m2和33.05 MPa,复合材料的最大吸水率为4.07%。经油酸处理的黄麻纤维可有效提高不饱和聚酯复合材料的性能。     

The role of additives in the manufacture of sheets of unsaturated polyester and postconsumer unsaturated polyester/glass fiber composites: Mechanical and dynamic mechanical properties

The storage of postconsumer glass fiber reinforced unsaturated polyester composite impacts negatively on the environment because of the long lifetime and the volume/amount ratio of residuals, which are important aspects to be considered. Two types of additives were employed as an attempt to improve the mechanical properties of sheets manufactured with ground postconsumer glass fiber reinforced orthophthalic unsaturated polyester resin composite and virgin orthophthalic unsaturated polyester resin, a silane‐coupling agent and an organic dispersant. Flexural and impact tests, and dynamic mechanical analyses, demonstrated that the coupling agent increased the mechanical properties, while the dispersant decreased these properties, compared to material without either additive. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1834–1839, 2004     

Mechanical properties of wood flake–polyethylene composites. II. Interface modification

This article discusses the methods of interface modification of composites based on raw wood flakes and high‐density polyethylene (HDPE) and the effects of these modifications on composite properties. An HDPE matrix was modified by a reaction with maleic anhydride (MA) in a twin‐screw extruder and then compounded with wood flakes to produce wood–polyethylene composites. Wood flakes were modified by a reaction with a silane coupling agent in an aqueous medium before being compounded with HDPE to produce silane‐modified WPCs. Differential scanning calorimetry and Fourier transform infrared spectroscopy data provide evidence for the existence of a polyethylene (PE)–silane‐grafted wood structure, which acts as a compatibilizer for wood flakes and PE. The results of MA‐modified composites indicate that some maleated HDPE is reacting with wood through esterification to form a compatibilizer for wood flakes and HDPE. Significant improvements in tensile strength, ductility, and Izod impact strength were obtained. Scanning electron micrographs provide evidence for strong interactions between the wood flakes and the matrix agent. The results indicate that 1–2 wt % MA modification on HDPE and 1–3 wt % silane treatment on wood flakes provide WPCs with the optimum properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2505–2521, 2002     

氢氧化镁的表面改性及在聚丙烯中的应用研究

研制了用硅烷和钛酸酯偶联剂表面改性后的氢氧化镁和聚丙烯的复合材料,研究了用不同表面活性剂改性的阻燃剂氢氧化镁的用量对复合材料阻燃性能和力学性能的影响。结果表明,硅烷偶联剂表面改性后的氢氧化镁能更好改善复合材料的力学性能,显著提高聚丙烯的阻燃性能,在用量为65%时,氧指数达到31.9%,垂直燃烧特性可达UL94V-0级。     

膨胀型阻燃剂/二乙基次磷酸铝阻燃改性不饱和树脂基复合材料

采用密胺包覆聚磷酸铵（APP）、季戊四醇（PER）和三聚氰胺（MEL）作为膨胀型阻燃剂（IFR）对不饱和树脂（UP）进行改性,研究了APP、PER和MEL不同复配比例及用量对不饱和树脂基复合材料阻燃性能和力学性能的影响。基于IFR最佳用量,以二乙基次磷酸铝（ADP）为协效剂,研究了ADP用量对IFR/UP阻燃复合材料阻燃性能、力学性能及热稳定性的影响。结果表明,当APP∶PER∶MEL复配比例为4∶1∶1,IFR添加量为15 %（质量分数,下同）时,复合材料综合性能最佳,其极限氧指数为27.4 %,UL 94垂直燃烧达到V?1等级,弯曲强度和冲击韧性分别为100.3 MPa和6.3 kJ/m²;ADP的引入能够进一步提高IFR/UP复合材料阻燃性能,且随着ADP质量分数的增加而增强;当ADP质量分数为2 %时,IFR?ADP/UP复合材料极限氧指数为28.5 %并达到V?0阻燃等级,弯曲强度和冲击韧性分别为110 MPa和7.8 kJ/m²,与IFR/UP复合材料相比,分别提高了9.7 %和23.8 %;ADP能够促进IFR/UP复合材料表面成炭,缓解基体的热降解。     

Effect of environmental stress on the mechanical properties of surface treated fly‐ash/polyester particulate composite

Fly‐ash (FA) was surface treated with silane coupling agents (CA) vinyltriethoxy silane and aminopropyltrimethoxysilane. Fly‐ash/polyester (FA/GPR) and surface treated fly‐ash/polyester (FA/CA/GPR) particulate composites were made. The composites were exposed to various adverse environmental conditions such as water, boiling water, salt water, acid, alkali, toluene, weather and freezing–thawing cycles for 30 days. The mechanical properties, ie tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus, compressive strength, impact strength and hardness of FA/GPR and FA/CA/GPR were studied before and after exposure to adverse environmental conditions. The results indicate that the mechanical properties of FA/GPR composites are improved by surface treatment of FA and that their resistance to the various environmental stresses is also enhanced substantially by surface treatment. © 2002 Society of Chemical Industry     

Sisal fibers treated with NaOH and benzophenonetetracarboxylic dianhydride as reinforcement of phenolic matrix

In this work, composites based on a phenolic matrix and untreated‐ and treated sisal fibers were prepared. The treated sisal fibers used were those reacted with NaOH 2% solution and esterified using benzophenonetetracarboxylic dianhydride (BTDA). These treated fibers were modified with the objective of improving the adhesion of the fiber–matrix interface, which in turn influences the properties of the composites. BTDA was chosen as the esterifying agent to take advantage of the possibility of introducing the polar and aromatic groups that are also present in the matrix structure into the surface of the fiber, which could then intensify the interactions occurring in the fiber–matrix interface. The fibers were then analyzed by SEM and FTIR to ascertain their chemical composition. The results showed that the fibers had been successfully modified. The composites (reinforced with 15%, w/w of 3.0 cm length sisal fiber randomly distributed) were characterized by SEM, impact strength, and water absorption capacity. In the tests conducted, the response of the composites was affected both by properties of the matrix and the fibers, besides the interfacial properties of the fiber–matrix. Overall, the results showed that the fiber treatment resulted in a composite that was less hygroscopic although with somewhat lower impact strength, when compared with the composite reinforced with untreated sisal fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on thermal degradation and flame retardant behavior of the sisal fiber reinforced unsaturated polyester toughened epoxy nanocomposites

Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant, and morphological behavior of the UP toughened epoxy (Epoxy/UP) were systematically studied. The chemical structures of Epoxy, UP, and Epoxy/UP systems were characterized using Proton Nuclear magnetic resonance (¹HNMR) and Fourier transform infrared (FTIR) spectra. The homogeneous dispersion of nanoclay within the polymer matrix was analyzed using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis. Incorporation of sisal fibers and C30B nanoclays within Epoxy/UP system resulted in an increase in the mechanical, thermal, and flame retardance properties. Thermogravimetric analysis (TGA) has been employed to evaluate the thermal degradation kinetic parameters of the composites using Kissinger and Flynn‐Wall‐Ozawa methods. Cone calorimeter, UL‐94, and LOI tests revealed a reduction in the burning rate of the matrix with the addition of fibers and nanoclays. The results showed that the treated fiber reinforced nanocomposites had higher thermal stability and better flame retardant properties than the treated fiber reinforced composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42068.     

Unsaturated polyester‐toughened epoxy composites: Effect of sisal fiber on thermal and dynamic mechanical properties

In the present study, the mechanical and thermal properties of sisal fiber‐reinforced unsaturated polyester (UP)‐toughened epoxy composites were investigated. The sisal fibers were chemically treated with alkali (NaOH) and silane solutions in order to improve the interfacial interaction between fibers and matrix. The chemical composition of resins and fibers was identified by using Fourier‐transform infrared spectroscopy. The UP‐toughened epoxy blends were obtained by mixing UP (5, 10, and 15 wt%) into the epoxy resin. The fiber‐reinforced composites were prepared by incorporating sisal fibers (10, 20, and 30 wt%) within the optimized UP‐toughened epoxy blend. Scanning electron microscopy was used to analyze the morphological changes of the fibers and the adhesion between the fibers and the UP‐toughened epoxy system. The results showed that the tensile and flexural strength of (alkali‐silane)‐treated fiber (30 wt%) ‐reinforced composites increased by 83% and 55%, respectively, as compared with that of UP‐toughened epoxy blend. Moreover, thermogravimetric analysis revealed that the (alkali‐silane)‐treated fiber and its composite exhibited higher thermal stability than the untreated and alkali‐treated fiber systems. An increase in storage modulus and glass transition temperature was observed for the UP‐toughened epoxy matrix on reinforcement with treated fibers. The water uptake behavior of both alkali and alkali‐silane‐treated fiber‐reinforced composites is found to be less as compared with the untreated fiber‐reinforced composite. J. VINYL ADDIT. TECHNOL., 23:188–199, 2017. © 2015 Society of Plastics Engineers