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.     

香蕉纤维的表面改性及其增强环氧树脂复合材料的性能研究

采用硅烷偶联剂(A-174)偶联、高锰酸钾接枝和乙酰化包覆等3种方法对香蕉纤维进行表面改性,制备了改性香蕉纤维增强环氧树脂复合材料,测试其拉伸、弯曲、压缩、冲击等力学性能。结果表明,偶联、接枝、包覆等表面改性均能明显改善香蕉纤维与基体树脂的相容性,提高复合材料的力学性能,其中偶联改性的效果最好。当改性香蕉纤维含量为10wt%时,与未改性的香蕉纤维比较,复合材料的拉伸强度、弯曲强度、压缩强度分别提高了1.8、1.0、2.6倍;随着纤维含量的增加,复合材料的力学性能明显提高。     

尼龙6改性研究

采用经化学改性的芳纶纤维增强尼龙6,并通过红外光谱和电镜分析其界面层,结果表明芳纶纤维经异氰酸酯化及封端稳定处理后,其表面所接技的不稳定基团-NCO转化成稳定的-NHCO-,封端结果较为明显;改性后纤维表面附有接枝物,从而使表面粗糙程度大大增加。用挤出和注塑的方法加工了PA6／Kevlar纤维（KF）复合材料,研究了它的拉伸、弯曲和冲击性能破坏形态。力学性能测试表明了改性尼龙6复合材料的拉伸和弯曲强度得到了改善,但冲击性能略为下降。     

不饱和聚酯树脂／苎麻布／碱式硫酸镁晶须复合材料的力学性能及热性能研究

研究了不饱和聚酯树脂（UP树脂）／苎麻布／碱式硫酸镁晶须复合材料的力学性能，探讨了苎麻布、晶须加入量对复合材料力学性能及热稳定性的影响，分析了复合材料的冲击断裂形貌。研究表明：当复合材料中苎麻布的质量恒定为UP树脂质量的7％时，增加晶须的含量，复合材料的弯曲模量及热稳定性随之增加，弯曲强度逐渐下降，拉伸强度及冲击强度先增加而后降低，当晶须加入量为10％时，拉伸强度及冲击强度均达到最大值，分别为30．16MP8和6．07kJ／m^2；当复合材料中晶须的质量恒定为UP树脂质量的10％时，增加复合材料中苎麻布的含量，复合材料的力学性能均随之增加，但热稳定性却下降。UP树脂／苎麻布／晶须复合材料的断面既有晶须裸露，又有卷曲的苎麻纤维分布，但苎麻布对冲击强度的贡献更突出。     

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。     

Novel eco‐friendly biodegradable coir‐polyester amide biocomposites: Fabrication and properties evaluation

Biocomposites are prepared from a cheap, renewable natural fiber, coir (coconut fiber) as reinforcement with a biodegradable polyester amide (BAK 1095) matrix. In order to have better fiber‐matrix interaction the fibers are surface modified through alkali treatment, cyanoethylation, bleaching and vinyl grafting. The effects of different fiber surface treatments and fiber amounts on the performance of resulting bio‐composites are investigated. Among all modifications, cyanoethylated coir‐BAK composites show better tensile strength (35.50 MPa) whereas 7% methyl methacrylate grafted coir‐BAK composites show significant improvement in flexural strength (87.36 MPa). The remarkable achievement of the present investigation is that a low strength coir fiber, through optimal surface modifications, on reinforcement with BAK show an encouraging level of mechanical properties. Moreover, the elongation at break of BAK polymer is considerably reduced by the incorporation of coir fibers from nearly 400% (percent elongation of pure BAK) to 16‐24% (coir‐BAK biocomposites). SEM investigations show that surface modifications improve the fiber‐matrix adhesion. From biodegradation studies we find that after 52 days of soil burial, alkali treated and bleached coir‐BAK composites show significant weight loss. More than 70% decrease in flexural strength is observed for alkali treated coir‐BAK composites after 35 days of soil burial. The loss of weight and the decrease of flexural strength of degraded composites are more or less directly related.     

Synthesis and mechanical properties of unsaturated polyester based nanocomposites

Two classes of nanocomposites were synthesized using an unsaturated polyester resin as the matrix and sodium montmorillonite as well as an organically modified montmorillonite as the reinforcing agents. X‐ray diffraction pattern of the composites showed that the interlayer spacing of the modified montmorillonite expanded from 1.25 nm to 4.5 nm, indicating intercalation. Glass transition values of these composites increased from 72°C, in the unfilled unsaturated polyester, to 86°C in the composite with 10% organically modified montmorillonite. From Scanning Electron Microscopy, it is seen that the degree of intercalation/exfoliation of the modified montmorillonite is higher than in the unmodified one. The mechanical properties also supported these findings, since in general, the tensile modulus, tensile strength, flexural modulus, flexural strength and impact strength of the composites with modified montmorillonite were higher than the corresponding properties of the composites with unmodified montmorillonite. The tensile modulus, tensile strength, flexural modulus and flexural strength values showed a maximum, whereas the impact strength exhibited a minimum at approximately 3–5 wt% modified montmorillonite content. These results imply that the level of exfoliation may also exhibit a maximum with respect to the modified montmorillonite content. The level of improvement in the mechanical properties was substantial. Adding only 3 wt% organically modified clay improved the flexural modulus of unsaturated polyester by 35%. The tensile modulus of unsaturated polyester was also improved by 17% at 5 wt% of organically modified clay loading.     

The influence of fiber surface modification on the mechanical properties of coir‐polyester composites

Coir, an important lignocellulosic fiber, can be incorporated in polymers like unsaturated polyester in different ways for achieving desired properties and texture. But its high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix lead to debonding with age. In order to improve the above qualities, adequate surface modification is required. In our present work, fiber surface modification was effected through dewaxing, alkali (5%) treatment, aqueous graft copolymerization of methyl methacrylate (MMA) onto 5% alkali treated coir for different extents using CuSO₄ – NaIO₄ combination as an initiator system and cyanoexhylation with a view to improve the mechanical performance of coir‐polyester composites. Mechanical properties like tensile strength (PS), flexural strength (ES) and impact strength (IS) of the composites as a function of fiber loading and fiber surface modification have been evaluated. Composites containing z5 wt% of fiber (untreated) improved tensile and flexural strength by 30% and 27% respectively in comparison to neat polyester. The work of fracture (impact strength) of the composite with 25 wt% fiber content was found to be 967 J/m. The elongation at break of the composites exhibits an increase with the introduction of fiber, All types of surface modification result In improved mechanical properties of the composites. Significant improvement in mechanical strength was also observed for composites prepared from 5% PMMA grafted fiber.     

Effect of alkali treatment on properties of unidirectional isora fibre reinforced epoxy composites

Abstract

Unidirectional isora fibre reinforced epoxy composites were prepared by compression moulding. Isora is a natural bast fibre separated from Helicteres isora plant by retting process. The effect of alkali treatment on the properties of the fibre was studied by scanning electron microscopy (SEM), IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties such as tensile strength, Young's modulus, flexural strength, flexural modulus and impact strength of the composites containing untreated and alkali treated fibres have been studied as a function of fibre loading. The optimum fibre loading for tensile properties of the untreated fibre composite was found to be 49% by volume and for flexural properties the loading was optimised at ～45%. Impact strength of the composite increased with increase in fibre loading and remained constant at a fibre loading of 54·5%. Alkali treated fibre composite showed improved thermal and mechanical properties compared to untreated fibre composite. From dynamic mechanical analysis (DMA) studies it was observed that the alkali treated fibre composites have higher E' and low tan δ maximum values compared to untreated fibre composites. From swelling studies in methyl ethyl ketone it was observed that the mole percentage of uptake of the solvent by the treated fibre composites is less than that by the untreated fibre composites. From these results it can be concluded that in composites containing alkalised fibres there is enhanced interfacial adhesion between the fibre and the matrix leading to better properties, compared to untreated fibre composites.     

Effect of Chemical Surface Modifications on the Properties of Alfa Fiber-Polyester Composites

Composite materials based on Alfa fibers and unsaturated polyester resins were manufactured by the hand layup technique. Mechanical properties of composites prepared form Alfa fibers collected from the region of Boussaada (Algeria), treated by various concentrations of NaOH solutions (1, 3, 6, 9, and 12%) during 24 h were found to be better than those of the untreated ones. The 6% NaOH-treated fibers composite showed maximum improvement in tensile strengths about 63% and the 9% NaOH treated fibers composite showed maximum improvement in flexural strength about 52%, respectively. The tensile modulus improved by 50.48%. The flexural modulus was also improved by 44.06% compared to the untreated Alfa fiber composite. FTIR characterization of Alfa fibers showed that the number of hydroxyl groups (OH) decreased and the crystallinity index increase by 16.60% after alkaline treatment. SEM observations on fibers' surfaces showed that the alkaline treatment improved the interface adhesion of fiber–matrix.     

Evaluation of the mechanical properties of sisal–polyester composites as a function of the polyester matrix formulation

In this work a comparative study on the impact and tensile properties of polyester/sisal fiber reinforced composites was undertaken. The polyester matrix was used bare and modified with: (1) a silane coupling agent; (2) a flame retardant system; and (3) a blend of the silane agent and the flame retardant system. The experimental results show that the flame retardant acts as a particulate reinforcement to the polyester matrix and the silane coupling agent acts as a plasticizer. The simultaneous addition of these two compounds to the polyester resin tended to decrease the performance of the composites. The results obtained show that strength or toughness could be tailored, and although none of the composites manufactured with the modified polyester matrices showed a significant improvement on the fiber–matrix interface strength, a better compromise between impact and tensile properties was obtained with the silane modified matrix. The critical fiber volume fraction was also evaluated and shown to be less than 10% for the sisal–polyester composite investigated here. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1209–1217, 2004     

Surface modification and physical properties of various UHMWPE‐fiber‐reinforced modified epoxy composites

Two surface modification methods—plasma surface treatment and chemical agent treatment—were used to investigate their effects on the surface properties of ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers. In the analyses, performed using electron spectroscopy for chemical analysis, changes in weight, and scanning electron microscope observations, demonstrated that the two fiber‐surface‐modified composites formed between UHMWPE fiber and epoxy matrix exhibited improved interfacial adhesion and slight improvements in tensile strengths, but notable decreases in elongation, relative to those properties of the composites reinforced with the untreated UHMWPE fibers. In addition, three kinds of epoxy resins—neat DGEBA, polyurethane‐crosslinked DGEBA, and BHHBP‐DGEBA—were used as resin matrices to examine the tensile and elongation properties of their UHMWPE fiber‐reinforced composites. From stress/strain measurements and scanning electron microscope observations, the resin matrix improved the tensile strength apparently, but did not affect the elongation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 655–665, 2007     

超支化聚合物对聚丙烯/剑麻纤维复合材料性能影响

为改善剑麻纤维(SF)与聚丙烯(PP)之间的相容性,在PP/SF复合材料中添加超支化聚酯(H101)、超支化环氧树脂(E102),研究了两种超支化聚合物(HBP)的热稳定性及对PP/SF复合材力学性能、熔体流动性和微观形貌的影响。热重分析表明,所使用的HBP均具有较好的热稳定性;扫描电子显微镜分析发现,HBP的加入使基体与纤维结合得更加紧密;力学性能测试表明,H101可不同程度地提高复合材料的拉伸、弯曲及冲击强度;E102可提高复合材料的拉伸及冲击强度,当E102含量为10%时,与PP/SF复合材料相比,冲击强度提高了72.24%。尽管HBP含量较高时复合材料的力学性能提高,但HBP会降低复合材料的熔体流动速率,选择HBP含量时需要综合考虑。     

玻纤毡增强聚丙烯复合材料的增容及力学性能

通过玻璃纤维(GF)毡与双螺杆挤出相容剂改性聚丙烯(PP)膜的多层叠合,以熔融浸渍法制得PP基GF毡增强热塑性塑料(GMT)复合材料,研究了相容剂PP接枝马来酸酐(PP-g-MAH)和PP接枝丙烯酸(PP-g-AA)的用量(为PP基体质量的百分数)及其复配改性,以及相容剂改性PP基体分布和毡体种类对GMT力学性能的影响。结果表明,PPg-MAH可明显提高GMT的拉伸与弯曲性能,但降低了冲击性能;PP-g-AA可明显提高GMT的冲击性能,但不利于拉伸与弯曲性能的提高,只有当PP-g-AA用量超过5%后,拉伸性能才有所提升。在PP-g-MAH用量为3%的条件下,将其与不同用量的PP-g-AA进行复配改性没有对GMT力学性能产生协同作用。在各相容剂用量相近(3%~3.5%)的情况下,与相容剂复配改性GMT相比,以两层PP-g-AA改性PP为芯层、PP-g-MAH改性PP为上下表面层作为改性基体分布时,GMT拉伸与弯曲强度分别提高17%和27%、缺口冲击强度提高48%;而以两层PP-g-MAH改性PP为芯层、PP-g-AA改性PP为上下表面层作为改性基体分布时,在不损失强度与刚性的同时,缺口冲击强度提高了88%。采用连续GF毡的GMT力学性能比采用短切GF毡的GMT高,尤其是缺口冲击强度提高了89.6%。     

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.     

Utilization of Flyash as Filler Material in Hybrid Polyester Composites for Improved Thermo-Mechanical and Erosion Wear Behavior

The present work was carried out for the utilization of major quantities of flyash as filler material in the short fiber reinforced polyester resin composites in various engineering and structural applications. The incorporation of flyash modifies the hardness, tensile, flexural, impact and damping behavior of the composites. It is observed that hardness, flexural modulus and impact strength of flyash filled composites increases with increase in the flyash filler contents. Whereas, with the addition of flyash contents it is observed that there is decrease in tensile strength and flexural strength. But beyond the 10 wt.-% flyash filler addition in the composite the flexural strength increases. At the end, the erosion wear behavior of all the composites has been studied by Taguchi experimental design. It is found that unfilled glass polyester composite suffers greater erosion loss as compare to particulate filled glass polyester composites. The eroded surface morphology is examined by SEM and the related erosion wear mechanism is discussed in detail.     

改性竹纤维增强聚丙烯复合材料的性能研究

以聚丙烯为基体材料,不同处理工艺改性的竹纤维为增强材料,采用密炼-注塑工艺制备聚丙烯/竹纤维复合材料。通过红外光谱仪(FTIR)、扫描电子显微镜(SEM)、热重分析仪(TGA)、万能试验机等对复合材料的化学结构、表面形态、热性能、力学性能等进行表征和测试。结果表明:偶联剂与碱处理均可改变竹纤维的表面特性,改善复合材料的界面相容性,其力学性能、热性能均随处理工艺有所改善。当偶联剂KH-550含量为2%时,复合材料有较好的力学性能,其断裂伸长率为14.5%,拉伸强度为30.48 MPa,冲击强度为22.4 kJ/m2。     

The effect of alkali treatment and filler size on the properties of sawdust/UPR composites based on recycled PET wastes

In this study, natural sawdust fillers from acacia were mixed with unsaturated polyester resin (UPR), which was prepared by recycling of polyethylene terephthalate (PET) waste bottles to prepare sawdust/UPR composite. PET wastes were recycled through glycolysis and depolymerized to produce a formulation for the resin. The effects of alkali treatment, filler content, and filler size on the tensile, flexural, hardness, and water absorption of the composites were investigated. The results show that the modulus of both tensile and flexural increased with increasing filler contents, but the tensile and flexural strength of composites decreased. The size of sawdust also played a significant role in the mechanical properties, with smaller size sawdust producing higher strength and modulus. This is due to the greater surface area for filler–matrix interaction. The results also show that alkali treatment causes a better adhesion between sawdust and UPR matrix and improves the mechanical properties of the composites. Furthermore, surface treatment reduced the water absorption of composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Banana fiber reinforced low-density polyethylene composites: effect of chemical treatment and compatibilizer addition

In this study, an attempt has been made to utilize banana fiber (a natural fiber from agricultural waste) as reinforcement for low-density polyethylene (LDPE) to develop environmental friendly composite materials. LDPE/banana fiber composites were fabricated at different fiber loadings (10, 15, 20, 25, and 30 wt %) using compression molding technique. The composite with the composition of 25 wt % banana fiber was observed to be optimum on the basis of biodegradability and mechanical properties. Further, the effect of banana fiber surface treatment (alkali and acrylic acid) on the mechanical properties, morphology and water absorption behavior of the LDPE/banana fiber composites in the absence and presence of compatibilizer (maleic anhydride grafted LDPE, MA-g-LDPE) was comparatively studied. The alkali and acrylic acid treatment of the banana fibers led to enhanced mechanical properties and water resistance property of the composites, and these properties got further improved by the addition of the compatibilizer. The addition of compatibilizer to the acrylic acid treated banana fiber composites showed the most effective improvement in the flexural and impact strength and also, exhibited a reduction in the water absorption capacity. However, the tensile strength of the compatibilized composites with treated fibers resulted in slightly lower values than those with untreated fibers, because of the degradation of fibers by chemical attack as was evidenced by scanning electron microscopy (SEM) micrographs. SEM studies carried out on the tensile fractured surface of the specimens showed improved fiber-matrix interaction on the addition of compatibilizer.     

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