Glass fiber reinforced ROMP-based bio-renewable polymers: Enhancement of the interface with silane coupling agents

In this study, the influence of silane coupling agents on interfacial adhesion in glass fiber reinforced polymers from the ring-opening metathesis polymerization (ROMP) of a linseed oil-based monomer and dicyclopentadiene is investigated experimentally. Two types of silane coupling agents, norbornenylethyldimethylchlorosilane (MCS) and norbornenylethyltrichlorosilane (TCS), are examined. Interfacial shear strength (IFSS) is evaluated by the microbond technique. The IFSS increases by about 150% for the MCS-treated fibers and by about 50% for the TCS-treated fibers compared to untreated fibers. Dynamic mechanical analysis of composite panels made with untreated and silane-treated fibers reveals that MCS-treated fiber composites have the highest storage modulus and glass transition temperature, indicating strong interfacial interactions at the glass/matrix interface. Short beam shear tests and scanning electron microscopy of fracture surfaces also confirm that MCS is more effective than TCS at improving interfacial adhesion.     

A study of the mechanical properties of short natural-fiber reinforced composites

The degree of fiber–matrix adhesion and its effect on the mechanical reinforcement of short henequen fibers and a polyethylene matrix was studied. The surface treatments were: an alkali treatment, a silane coupling agent and the pre-impregnation process of the HDPE/xylene solution. The presence of Si–O–cellulose and Si–O–Si bonds on the lignocellulosic surface confirmed that the silane coupling agent was efficiently held on the fibres surface through both condensation with cellulose hydroxyl groups and self-condensation between silanol groups.

The fiber–matrix interface shear strength (IFSS) was used as an indicator of the fiber–matrix adhesion improvement, and also to determine a suitable value of fiber length in order to process the composite with relative ease. It was noticed that the IFSS observed for the different fiber surface treatments increased and such interface strength almost doubled only by changing the mechanical interaction and the chemical interactions between fiber and matrix.

HDPE-henequen fiber composite materials were prepared with a 20% v/v fiber content and the tensile, flexural and shear properties were studied. The comparison of tensile properties of the composites showed that the silane treatment and the matrix-resin pre-impregnation process of the fiber produced a significant increase in tensile strength, while the tensile modulus remained relatively unaffected. The increase in tensile strength was only possible when the henequen fibers were treated first with an alkaline solution. It was also shown that the silane treatment produced a significant increase in flexural strength while the flexural modulus also remained relatively unaffected. The shear properties of the composites also increased significantly, but, only when the henequen fibers were treated with the silane coupling agent. Scanning electron microscopy (SEM) studies of the composites failure surfaces also indicated that there is an improved adhesion between fiber and matrix. Examination of the failure surfaces also indicated differences in the interfacial failure mode. With increasing fiber–matrix adhesion the failure mode changed from interfacial failure and considerable fiber pull-out from the matrix for the untreated fiber to matrix yielding and fiber and matrix tearing for the alkaline, matrix-resin pre-impregnation and silane treated fibers.     

纤维表面处理与基体改性对连续玻纤增强聚丙烯力学性能的影响

考察了连续玻纤的表面处理、基体的接枝改性及接枝单体的种类和接枝产物的加入量对连续玻纤毡增强聚丙烯(CGFRPP) 力学性能的影响, 并通过红外光谱、扫描电镜对CGFRPP 的界面化学作用及界面粘结进行了研究。结果表明, 马来酸酐接枝改性聚丙烯与未经偶联剂处理的玻纤不能形成有效的化学结合, 而与经硅烷偶联剂表面处理的玻纤可发生明显的化学作用, 形成良好粘结, 显著提高CGFRPP 的力学性能; 硅烷偶联剂的种类对以改性PP 为基体的CGFRPP 力学性能的影响不大; 马来酸酐接枝聚丙烯比丙烯酸接枝聚丙烯对CGFRPP 力学性能的改善更为有效。      

Effect of fiber loading on the properties of treated cellulose fiber-reinforced phenolic composites

The effect of fiber loading on the properties of treated cellulose fiber-reinforced phenolic composites was evaluated. Alkali treatment of the fibers and reaction with organosilanes as coupling agents were applied to improve fiber–matrix adhesion. Fiber loadings of 1, 3, 5, and 7 wt% were incorporated to the phenolic matrix and tensile, flexural, morphological and thermal properties of the resulting composites were studied. In general, mechanical properties of the composites showed a maximum at 3% of fiber loading and a uniform distribution of the fibers in such composites was observed. Silane treatment of the fibers provided derived composites with the best thermal and mechanical properties. Meanwhile, NaOH treatment improved thermal and flexural properties, but reduced tensile properties of the materials. Therefore, the phenolic composite containing 3% of silane treated cellulose fiber was selected as the material with optimal properties.     

Wheat gluten composites reinforced with coconut fiber

Coconut fiber-reinforced wheat gluten (WG) biocomposites were fabricated. The coconut fibers (CCFs) were chemically modified by either sodium hydroxide or silane treatment, as well as following the alkali surface treatment with a silane treatment. (3-triethoxysilylpropyl)-t-butylcarbamate (carbamate silane), which is a masked isocyanate functional silane, was used for the first time to improve interfacial adhesion between WG and natural fibers. X-ray photoelectron spectroscopy (XPS) and gas chromatography/mass spectroscopy (GC/MS) analyses were employed to prove the presence of the silane on silane-treated coconut fiber (SCCF) and alkali-followed by silane-treated fiber (ASCCF). It was found that ASCCF has more silane content on the fiber surface than SCCF. The mechanical properties of composites with 15 mass% fiber loading were assessed by three-point bending tests. Moreover, scanning electron microscopy (SEM) was used to investigate fracture surface characteristics of composites. The WG/ASCCF composite provided an 80% increase in strength, and showed superior fiber–matrix interfacial adhesion.     

硅烷偶联剂表面改性玄武岩纤维增强复合材料研究进展

表面改性是增强玄武岩纤维与基体材料之间结合性能的关键。综述了硅烷偶联剂表面改性以及酸、碱刻蚀,等离子处理辅助协同硅烷偶联剂表面改性玄武岩纤维的研究进展,介绍了硅烷偶联剂表面改性玄武岩纤维在聚合物基复合材料中的应用,并对发展趋势进行了展望,同时分析了硅烷偶联剂表面改性玄武岩纤维当前存在的问题。     

Development of slate fiber reinforced high density polyethylene composites for injection molding

During the last decade the use of fiber reinforced composite materials has consolidated as an attracting alternative to traditional materials due to an excellent balance between mechanical properties and lightweight. One drawback related to the use of inorganic fibers such as those derived from siliceous materials is the relative low compatibility with conventional organic polymer matrices. Surface treatments with coupling agents and the use of copolymers allow increasing fiber–matrix interactions which has a positive effect on overall properties of composites. In this research work we report the use of slate fiber treated with different coupling agents as reinforcement for high density polyethylene from sugarcane. A silane (propyltrimethoxy silane; PTMS) and a graft copolymer (polyethylene-graft-maleic anhydride; PE-g-MA) were used to improve fiber–matrix interactions on HDPE-slate fiber. The effect of the different compatibilizing systems and slate fiber content were evaluated by scanning electron microscopy (SEM), dynamic thermomechanical analysis (DTMA) as well as mechanical properties (tensile, flexural and impact). The results show that the use of silane coupling agents leads to higher fiber–matrix interactions which has a positive effect on overall mechanical properties. Interesting results are obtained for composites containing 30 wt.% slate fiber previously treated with propyltrimethoxy silane (PTMS) with an increase in tensile and flexural strength of about 16% and 18% respectively.     

Effect of Silane Coupling Agents on Rice Straw Fiber/Polymer Composites

The effect of coupling agents and electron beam (EB) irradiation dose on the mechanical properties of composites made from rice straw fibers and polymers have been studied. Samples were made by hot pressing of mix composition at 130°C. The pressed samples were subjected to electron beam irradiation dose ranged from 10 to 50?kGy. Increasing the electron beam irradiation dose increased the value of flexural strength, modulus of elasticity and impact strength. It was also observed that, the properties of composites containing γ-aminopropyltrimethoxy silane (A-1100) are lower than those of composites containing N-(2aminoethyl)-3-amino propyltrimethoxy silane (A-700) coupling agents. These are attributed to a hydrogen bonding formation between the amine or protonated amine and the hydroxyl groups of rice straw fibers. The presence of coupling agents in the composites during the EB irradiation process produce a more free radicals which are enough to form a chemical bonding between the rice straw fiber and polymer. The thickness swelling and water absorption values decrease with increasing the EB irradiation dose with presence of coupling agents in the composite.     

热塑性聚合物/木纤维复合材料的研究进展

介绍了国内外关于热塑性聚合物／木纤维复合材料界面改性、在加工过程中木纤维的热稳定性以及阻燃性能等方面的研究进展，界面相容剂或偶联剂能大大提高其界面相容性，特别是马来酸酐接枝热塑性聚合物作为界面相容剂更为有效。硅烷偶联剂预处理木纤维表面对提高其热稳定性有一定的作用。     

Effect of fiber surface treatments on mechanical and abrasive wear performance of polylactide/jute composites

The main focus of this work is to improve the adhesion of jute fiber with polylactide (PLA). For this purpose, surface of the jute fiber was modified by alkali, permanganate, peroxide and silane treatments. The surface modified fibers were characterized by FTIR spectroscopy. Unidirectional composites were prepared with treated jute fibers and PLA matrix by hot pressing of solvent impregnated prepregs. Surface treatments resulted in enhancement of tensile and flexural properties and reduction in Izod impact strength. Dynamic mechanical analysis (DMA) results showed that, treated composites have higher storage modulus and lower tangent delta with respect to untreated composite. The degree of interfacial adhesion between the jute fiber and PLA was estimated using adhesion parameter obtained through DMA data. The results of thermogravimetric analysis (TGA) showed a higher thermal stability for silane treated composites. Experimental results on abrasive wear tests revealed that the wear resistance of composite is sensitive to fiber/matrix adhesion.     

Characterization and biodegradability of polypropylene composites using agricultural residues and waste fish

The objective of this research was to study the potential of waste agricultural residues such as rice-husk fiber (RHF), bagasse fiber (BF), and waste fish (WF) as reinforcing and biodegradable agents for thermoplastic composites. Addition of maleic anhydride grafted polypropylene (MAPP) as coupling agent was performed to promote polymer/fiber interfacial adhesion. Several composites with various polypropylene (PP) as polymer matrix, RHF, BF, WF, and MAPP contents were fabricated by melt compounding in a twin-screw extruder and then by injection molding. The resulting composites were evaluated through mechanical properties in terms of tensile, flexural, elongation at break and Izod notched impact following ASTM procedures. Biodegradability of the composites was measured using soil burial test in order to study the rates of biodegradation of the composites. In general, the addition of RHF and BF promoted an increase in the mechanical properties, except impact strength, compared with the neat PP. According to the results, WF did not have reinforcing effect on the mechanical properties, while it could considerably improve the biodegradation of the composites. It was found that the composites with high content of WF had higher degradation rate. Except impact strength, all mechanical properties were found to enhance with increase in cellulosic fiber loading In addition, mechanical properties and biodegradability of the composites made up using RHF was superior to those of the composites fabricated with BF, due to its morphological (aspect ratio) characteristics.     

Effect of surface modification of bamboo cellulose fibers on mechanical properties of cellulose/epoxy composites

Bamboo cellulose fibers were treated with NaOH aqueous solution and silane coupling agent, respectively, before they were applied into epoxy composites. The effect of surface modification on mechanical properties was evaluated by tensile and impact tests under controlled conditions. Compared with the untreated cellulose filled epoxy composites, the NaOH solution treatment increased the tensile strength by 34% and elongation at break by 31%. While silane coupling agent treatment produced 71% enhancement in tensile strength and 53% increase in elongation at break. The scanning electron microscopy (SEM) was used to observe the surface feature of the cellulose fibers and the tensile fractures as well as cryo-fractures of the composites. The Fourier transform infrared (FTIR) was employed to analyze the chemical structure of the cellulose fibers before and after modifications. The results indicated different mechanisms for the two modifications of cellulose. The NaOH solution partly dissolved the lignin and amorphous cellulose, which resulting in splitting the fibers into smaller size. This led to easier permeating into the gaps of the fibers for epoxy resin (EP) oligmer and forming effective interfacial adhesion. Based on the emergence of Si–O–C and Si–O–Si on the cellulose surface, it was concluded that the enhancement of mechanical properties after coupling agent modification could be ascribed to the formation of chemical bonds between the cellulose and the epoxy coupled with the coupling agent.     

Improvement of physico-mechanical properties of coir-polypropylene biocomposites by fiber chemical treatment

In preparing polymer–matrix composites, natural fibers are widely used as “reinforcing agents” because of their biodegradable characteristic. In present research, coir fiber reinforced polypropylene biocomposites were manufactured using hot press method. In order to increase the compatibility between the coir fiber and polypropylene matrix, raw coir fiber was chemically treated with basic chromium sulfate and sodium bicarbonate salt in acidic media. Both raw and treated coir at different fiber loading (10, 15 and 20 wt%) were utilized during composite manufacturing. During chemical treatment, hydrophilic –OH groups in the raw coir cellulose were converted to hydrophobic –OH−Cr groups. Microstructural analysis and mechanical tests were conducted. Scanning electron microscopic analysis indicates improvement in interfacial adhesion between the coir and polypropylene matrix upon treatment. Chemically treated specimens yielded the best set of mechanical properties. On the basis of fiber loading, 20% fiber reinforced composites had the optimum set of mechanical properties among all composites manufactured.     

Preparation,crystallization behaviors,and mechanical properties of biodegradable composites based on poly(L-lactic acid) and recycled carbon fiber

The biodegradable composites based on poly(L-lactic acid) (PLLA) and recycled carbon fiber (RCF) were prepared through melting extrusion. The surface-treatment of RCF with silane coupling agent enhanced the interfacial adhesion between RCF and PLLA, and thus the PLLA/RCF composites achieved a significant improvement in mechanical properties. The morphologies of fracture surfaces indicated that the RCF obtained a homogeneous dispersion in PLLA matrix due to a good interfacial interaction. The investigations on the crystallization behaviors and kinetics demonstrated that the RCF acted as a nucleation agent for the crystallization of PLLA, and the crystallization rate and the nucleation density of PLLA matrix were improved remarkably due to the heterogeneous nucleating effect of RCF in the matrix. These features may be advantageous for the enhancement of mechanical properties, heat resistance, and processability of PLLA-based materials. The PLLA-based composites made from RCF can be used as low cost biodegradable materials for many applications.     

Processing of Functionalized and Pristine Carbon Nanotube Epoxy Composites with Silane-Treated Glass Fiber

In this work, an attempt has been made to study the bonding between the silane coupling agents and the glass fiber (GF) surface. The mechanical properties of the composites so obtained have been specifically analyzed. It has been experimentally found that epoxy silane (ES)-treated GF mat in a neat epoxy matrix showed considerable improvement compared to amino silane (AS)-treated GF. The effect of heat treatment on GF has also been looked into. Moreover, a new processing technique has been explored, which involves the use of amino functionalized nanotube (ACNT) and pristine nanotube (PCNT), homogeneously and uniformly dispersed in an epoxy matrix. Additionally, the effect of ES- and AS-treated GF in the presence of PCNTs and ACNTs has been studied and it has been found that AS shows strong interfacial adhesion in the ACNT matrix, whereas ES shows improved mechanical behavior in the PCNT matrix. The findings from this study have certainly helped us design improved fiber reinforced nanocomposites with enhanced mechanical properties suitable for marine structures.     

Biomicrofibrilar composites of high density polyethylene reinforced with curauá fibers: Mechanical,interfacial and morphological properties

Vegetal fibers are used in polymer composites to improve mechanical properties, substituting inorganic reinforcing agents produced by non renewable resources, like fiberglass. The highest performance formulation in high density polyethylene, HDPE, composites reinforced with curauá fibers were studied, aiming to improve the interphase interaction and optimize the mechanical properties. The fiber content, the type and the concentration of coupling agent were tested. The composites and the pure materials were characterized by Fourier transform infrared spectroscopy and the fiber/matrix phase adhesion was evaluated by scanning electron microscopy. The mechanical properties and the micrographs showed that the best formulation is: 20 wt.% of milled curauá fibers and 2 wt.% poly(ethylene-g-maleic anhydride). The coupled composites are also less hygroscopic than the uncoupled composites. We conclude that the composites reinforced with curauá fibers have mechanical properties comparable to commercially produced composites of HDPE reinforced with fiberglass.     

Surface modification and adhesion mechanisms in woodfiber-polypropylene composites

The interfacial adhesion between wood fiber and thermoplastic matrix polymer plays an important role in determining the performance of wood-polymer composites. The objectives of this research were to elucidate the interaction between the anhydride groups of maleated polypropylene (MAPP) and hydroxyl groups of wood fiber, and to clarify the mechanisms responsible for the interfacial adhesion between wood fiber and polypropylene matrix. The modification techniques used were bulk treatment in a thermokinetic reactive processor and solution coating in xylene. FT-IR was used to identify the nature of bonds between wood fiber and MAPP. IGC and wood veneer pull-out test was used to estimate the interfacial adhesion. Mechanical properties of injection molded woodfiber-polypropylene composites were also determined and compared with the results of esterification reaction and interfacial adhesion tests. Confocal Microscopy was employed to observe the morphology at the wood fiber-polypropylene interface, and the dispersion and orientation of wood fiber in the polypropylene matrix, respectively. The effectiveness of MAPP to improve the mechanical properties (particularly the tensile strength) of the composites was attributed to the compatibilization effect which is accomplished by reducing the total wood fiber surface free energy, improving the polymer matrix impregnation, improving fiber dispersion, improving fiber orientation, and enhancing the interfacial adhesion through mechanical interlocking. There was no conclusive evidence of the effects of ester links on the mechanical properties of the composites.     

Thermal and mechanical properties of chemically treated oil palm fiber filled acrylonitrile butadiene styrene composites

In this work, chemical surface treated oil palm fibers, including alkali, maleic and silane pre‐treatments are melt blended and hot compression molded with acrylonitrile butadiene styrene into varying compositions of polymer composites. The effectiveness of the chemical pre‐treatment and fiber dispersion are analyzed with the aid of Fourier‐transform infrared spectrometry and scanning electron microscope while the influences on thermal degradation and mechanical properties of the resulting composites are analyzed through thermal gravimetric analysis and tensile test respectively. Differential thermogravimetric analysis result show that alkali, maleic and silane pre‐treatments could lower the onset thermal degradation temperature of oil palm fiber filled acrylonitrile butadiene styrene composites. The tensile test results show that chemically treated oil palm fiber filled acrylonitrile butadiene styrene composites attained enhancement in tensile strength as compared to untreated counterpart. Scanning electron microscopy observations on fracture surfaces of oil palm fiber filled acrylonitrile butadiene styrene composites found that the reinforcing efficiency of chemically treated oil palm fiber could be further increased by improving interfacial bonding between oil palm fiber and acrylonitrile butadiene styrene.     

Study of chemical and mechanical properties of Dharbai fiber reinforced polyester composites

This investigation is focused on identifying a new variety of natural fiber (Dharbai fiber) for reinforcement in polymer matrix composites. An investigation on extraction procedure of Dharbai fibers has been undertaken. The chemical properties of Dharbai fibers were determined experimentally as per TAPPI standards. The FT-IR Spectroscopy was used to study the chemical structure of Dharbai fibers and the tensile properties of these fibers were studied using single filament test. The fibers extracted were reinforced in polyester matrix by varying the fabrication parameters namely fiber weight content (%) and fiber length (mm). The effect of fiber weight content and fiber length on the mechanical properties of Dharbai fiber-polyester composites were evaluated as per ASTM standards. Scanning electron microscope was used to characterize the interfacial bonding between Dharbai fibers and polyester matrix. This study confirmed that, the Dharbai fibers could be used as an effective reinforcement material for making low load bearing polymer composites.     

甘蔗渣显微结构对聚乳酸/甘蔗渣复合材料结构与性能的影响

采用碱处理、硅烷偶联剂处理以及碱处理配合硅烷偶联剂处理等方式改性甘蔗渣(BF),采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)、热重分析(TGA)以及力学性能测试等研究改性后BF结构的变化。结果表明,不同改性方法均明显改变了BF的结构及改性剂的键合方式。碱处理能够去除BF中的半纤维素等小分子聚合物以及部分非晶区的纤维素,导致BF热稳定性降低,结晶度上升。碱液浓度偏高以及碱处理时间过长会导致BF的纤维表面原纤化,虽然能增加与偶联剂反应的面积,但BF的强度大大下降,不利于BF的增强作用。因此,硅烷偶联剂处理的BF/PLA复合材料的相容性及力学性能最佳,其次为碱处理配合硅烷偶联剂处理的BF/PLA复合材料,最后为碱处理的BF/PLA复合材料。