Investigation of the effect of different silane coupling agents on mechanical performance of basalt fiber composite laminates with biobased epoxy matrices

In recent years, it has been detected an increased interest in the development of materials from renewable resources. This trend has been intensified in the industrial sector where significant efforts have been made in this field in order to adapt these natural fibers to conventional industrial processes and applications. As a result, research has been done into developing new thermoplastic matrices which are compatible with this type of reinforcing fibers. This study evaluates the influence of different coupling agents based on silanes, on the mechanical properties of composite laminates made from a biobased epoxy resin matrix and basalt fabric by using vacuum assisted resin transfer moulding. The curing behavior of the biobased epoxy resin was evaluated by differential scanning calorimetry (DSC), gel point determination, and ionic conductivity. The evaluation of mechanical properties was done by tensile, flexural, impact, and hardness tests. Compatibility between basalt fibers and epoxy resin generally has managed to increase through the addition of silanes, after the addition of these, their mechanical properties are substantially improved compared to the sample without silane treatment, obtaining this way an easily processable material, with good properties and capable of competing with materials with petroleum‐based epoxy resins. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Continuous monitoring of the fragmentation phenomenon in single fiber composite materials

A continuously monitored single-filament composite (CM-SFC) test was conducted to measure the stress at which successive fiber breaks occur in the single fiber fragmentation process. This exercise was performed with a limited number of samples of various types. The purpose was to explore the possibility of using this test as a simple alternative means of (i) measuring the size effect in single fibers, (ii) calculating the Weibull shape and scale parameters for fiber strength, (iii) calculating the fiber/matrix interfacial shear strength from the extrapolated value of fiber strength using the loading history of a single fragmentation test, rather than from the value of fiber strength extrapolated from extensive testing of single fibers at various gage lengths, as is usually done. These are aspects of the SFC test that have largely been ignored so far. The results presented here confirm the possibility of using the CM-SFC test for such purposes, with a certain degree of approximation, as discussed. Additional information supplied by this test as well as a possible effect of fiber pre-tensioning on fragmentation results (including the value of the interfacial shear strength) are also briefly discussed.     

Effects of silane coupling agents on internal reinforcement of wood by E-glass and basalt fibers

The internal reinforcement of Douglas-fir by glass or basalt fibers impregnated with resorcinol-phenol-formaldehyde or polymeric diphenylmethanediisocyanate bonding resins has been investigated. The objective was to evaluate the improvement in composite properties by the use of silane coupling agents. Fibers were treated with 3-(4-methoxyphenyl) propyl methyldichlorosilane for use with the phenolic resin, and with 3-aminopropyl triethoxysilane for use with the isocyanate resin. Resin impregnated fiber plies were sandwiched between wood pieces to prepare test specimens with 17 vol. % fiber for measurement of block shear strength, and modulus of rupture (MOR) and modulus of elasticity (MOE) in 3-point bending, and interlaminar shear strength in 5-point bending. The durability under wet conditions was evaluated by subjecting the specimens to an accelerated exposure test (ASTM D2559). It was found that silane application resulted in slight shear strength improvement under dry conditions but much higher increase in shear strength retention after exposure to moisture. Basalt fibers and E-glass fibers gave similar results and comparable properties.     

Effects of the organometallic coupling agents on adhesion of the carbon fiber–BMI composites

In order to increase the chemical bonding force between fiber and resin, several kinds of organometallic coupling agent (such as titanate, zirconate, and zircoaluminate) were chosen and added in the BMI resin formulation, which possess the same solvent system with those coupling agents. The DSC analysis technique was used to find the best curing condition, and TGA was used to investigate the thermal stability property of the best curing condition. For the purpose of analyzing the bonding structure, ESCA surface element analysis techniques was applied in this study. Beside that, the mechanical properties of tensile, flexural, and short-beam shear strengths were measured for the effect of adding coupling agents, and the SEM of fracture surfaces were taken to study the fractural analysis. The results showed that composites with the application of organometallic coupling agents of [RO–Ti(OX–R′NH₂)₃] structure in the treatment of BMI resin were highly thermal stable. Also, it was shown that the mechanical strengths of composites fabricated by pretreatment of the carbon fibers with coupling agents were higher than those fabricated by adding coupling agents in resins, but there was no obvious improvement of mechanical properties with higher concentration of coupling agents. However, the SEM showed that the adhesion between fiber and resin can actually be improved by adding proper amount of coupling agents in the BMI resin formulation.     

硅烷偶联剂对硅酮密封胶性能的影响

探讨了3种硅烷偶联剂与复配硅烷偶联剂对所制备硅酮密封胶性能的影响,包括：表干时间及固化深度、粘接性能、力学性能、热贮稳定性。其中,复配硅烷偶联剂对提高硅酮密封胶的以上性能效果显著,尤其是粘接性能。     

Influence of coupling agents and treatments on the mechanical properties of cellulose fiber–polystyrene composites

Wood fibers of aspen in the form of chemithermomechanical pulp (CTMP) and Tembec 6816 have been used as reinforcing fillers in different varieties of polystyrene. The tensile strength, elongation, and energy at maximum point, as well as tensile modulus at 0.1% strain is reported. Also revealed is the optimum condition of compression molding. The influence of different coupling agents, such as poly[methylene(polyphenyl isocyanate)], silanes (A-172, A-174, A-1100), and grating on the mechanical properties of composites is discussed. The extent of increase in mechanical properties depends on the weight percentage of fibers, the concentration of coupling agents, and the grafting level (add-on %). Coating followed by an isocyanate treatment appears to be the best treatment. In addition, the isocyanate treatment and grafting are superior to the silane treatment. Experimental results are explained on the basis of possible interactions among cellulose fiber-coupling agent-polymer in the interfacial area.     

A review on oil palm empty fruit bunch fiber‐reinforced polymer composite materials

Natural fiber‐reinforced polymer composite materials have emerged in a wide spectrum of area of the polymer science. The composite produced from these types of materials are low density, low cost, comparable specific properties, and most importantly they are environmental friendly. The composite materials produced from oil palm fibers and commercially available polymers have offered some specific properties that can be comparable to conventional synthetic fiber composite materials. However, these properties are greatly dependent on the compatibility of oil palm fibers and matrix phase with moisture absorption as one of the critical issues that becomes the drawbacks of the oil palm fiber polymer composite materials. Apparently, it greatly affects the physical as well as mechanical properties of the composite materials. The present review reports the work on oil palm empty fruit bunch (OPEFB) fiber‐reinforced polymer composites with some interest on the OPEFB physical structure, and chemical compositions. Finally, the incorporation of OPEFB into polymeric materials leads to several interesting consequences on the water absorption characteristics and the mechanical properties, which have been reviewed. POLYM. COMPOS., 31:2079–2101, 2010. © 2010 Society of Plastics Engineers     

Studies of the effects of the organometallic coupling agents on adhesion of the glass fiber–BMI composites

This work investigates the increase of adhesion between glass fiber and BMI. Five kinds of organometallic coupling agents of Ti, Zr, and Zr/Al are used to treat the fiber surface and then to reinforce BMI. A more efficient way is to mix the coupling agents directly into BMI and then reinforce by glass fiber. Then compare the adhesion of resulting composites, which are made by two methods described as above. As a result, the mechanical properties of the latter is slightly lower than the former. The Ti coupling agents are most effective, followed by Zr coupling agents and then Zr/Al coupling agents. Mixing Ti coupling agent directly into BMI, the degree of curing measured by DSC is 90%, the shear strength of the GFRP increases 31.9%, the flexural strength increases 30.8%, and the tensile strength increases 34.0%. Analyzing the chemical bonding by FT-IR, we found that choosing the organometallic coupling agent of type [RO–Ti (OX–R'NH₂)₃] and adding it to BMI can most effectively improve the adhesion. TGA shows that directly mixing coupling agent into BMI only changes a little of its thermal cracking temperature. Observed by SEM, we know that using coupling agent can promote adhesion between BMI and glass fiber.     

Effects of coupling agents on the properties of an NR/SBR matrix and its adhesion to continuous basalt fiber cords

The effects of various coupling agents on the characteristics and properties of a natural rubber (NR)/styrene–butadiene rubber (SBR) matrix and its adhesion to continuous basalt fiber (CBF) cords were studied. Four types of silane-based and two types of titanate-based coupling agents were added separately to the rubber matrix during the mixing process. The processability of the rubber compounds and the mechanical and tension fatigue properties of the vulcanizates were evaluated. The static and dynamic adhesion between the CBF cord/rubber matrices were investigated using the H pull-out test and an elastomer testing system, respectively. The results showed that the effects of the coupling agent were controlled by its chemical structure, and it was found that the addition of (3-aminopropyl)triethoxysilane was the most effective for enhancing the interfacial fatigue properties, due to the combined improvements of the initial adhesion, interfacial stress states, and the fatigue property of the rubber matrix. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47098.     

Simplification and application of single fiber fragmentation test on silylated polyester–glass fiber composites

Single fiber fragmentation test (SFFT) was used to investigate the interfacial adhesion in glass fiber‐unsaturated polyester composites. A simplified approach was developed for SFFT based on determination of the maximum number of fragments on the fiber at the end of the test. This approach does not involve length measurements and shortens the experiment time to a few minutes. By using a digital camera attached to the microscope, photographs of the coupon were taken during the test, and the number of fragments within the gauge length were counted later. This method allows quick, quantitative comparison of different fibers and matrices. The test samples were prepared by using commercial polyester resin and E‐glass fibers having different commercial sizings. SFFT results were in excellent agreement with the macromechanical test done on samples prepared with the same glass fiber and same polyester. The crack modes and debonding phenomena were examined from the microscopic images. Atomic force microscopic (AFM) images of the fiber were examined to get detailed topographic information about fiber surfaces. To improve interfacial adhesion, commercial unsaturated polyester was reacted with 3‐aminopropyltriethoxy silane via Michael Addition reaction on the maleate double bonds of the polyester. The resulting silylated polyester was characterized by H¹ NMR spectroscopy. The results of SFFT showed that the maximum numbers of fragments increased 23% on using silylated polyester. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

硅烷偶联剂对玻纤/聚丙烯复合材料的影响

分别选用KH550、KH570两种硅烷偶联剂处理无碱无捻粗纱,采用挤出、注塑成型技术制备玻纤增强聚丙烯复合材料,对复合材料进行了分析和研究。结果表明：硅烷偶联剂具有提高GF/PP复合材料性能的作用。SEM显示KH570处理GF与PP基体之间形成了良好的界面,界面层起到很好的应力传递作用,达到良好的增强效果。     

硅烷偶联剂对热空气老化过程中溶聚丁苯橡胶/白炭黑复合材料性能的影响

研究了硅烷偶联剂双-[3-(三乙氧基硅)丙基]-四硫化物(Si 69)、双-[3-(三乙氧基硅)丙基]-二硫化物(Si 75)及3-辛酰基硫代-1-丙基三乙氧基硅烷(NXT)对丁苯橡胶/白炭黑复合材料的硫化胶在热空气老化过程中力学性能、应力弛豫、交联密度及喷霜现象的影响。结果表明,与未加偶联剂的胶料相比,加入Si 69、Si 75或NXT的溶聚丁苯橡胶/白炭黑硫化胶的力学性能、应力弛豫系数和交联密度都相应提高,其中在热空气老化过程中,应力弛豫系数随老化时间的延长而增大,并且随着老化时间的延长,NXT改性体系的应力弛豫行为逐渐弱于Si 69和Si 75改性体系。加入Si 69可以减小在热空气老化过程中复合材料交联密度的增长率,且增长率随Si 69用量的增加而减小。加入硅烷偶联剂可以减弱溶聚丁苯橡胶/白炭黑复合材料的喷霜现象,体系表面的喷出物主要为白炭黑。     

Interface of polyimide–silica grafted with different silane coupling agents: Molecular dynamic simulation

In this article, the effects of different silane coupling agents: 3‐glycidyloxypropyltrimethoxysilane (GOTMS), 3‐aminopropyltriethoxysilane (APTES), and 3‐methacryloxypropyltrimethoxysilane (MPTS), on the interface between polyimide (PI) and silica (SiO₂), were investigated using molecular dynamic simulation. The results indicate that binding energy between PI molecules and SiO₂ surface mainly comes from van der Waals interaction. Proper silane coupling agents generate a thin membrane on the surface of SiO₂, which improves the thickness of the transition layer between PI molecules and SiO₂ surface. And density of the transition layer was enhanced by APTES significantly. In addition, amino group (? NH₂) improves the electrostatic interaction between PI molecules and SiO₂ surface rather than epoxy group (? CH? CH₂? O) and methacrylic oxide group (? O? CO? C(CH₃)?CH₂). As a result, APTES enhances the binding energy effectively. However, excessive silane coupling agent increases the distance between PI matrices and SiO₂, which deteriorates performance of the interface. In addition, GOTMS and MPTS generate a thick and dense membrane on SiO₂ surface, which induces the loose transition layer and poor binding energy. Overlap parameter between PI molecules and SiO₂ surface grafted with silane coupling agent can be employed to evaluate the transition layer successfully. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45725.     

Effect of silane coupling agents on the properties of pine fibers/polypropylene composites

In the present work, PP‐based composites, reinforced with surface modified pine fibers, have been prepared. The surface of the fibers has been treated with several silane derivatives bearing specific functionalities. ? NH₂, ? SH, long aliphatic chain, and methacrylic group were chosen as functionalities of the silane derivatives for evaluating the compatibility with the polymer matrix. Mechanical analysis, contact angle and XPS spectra, SEM microscopy, and water uptake measurements were used as characterization techniques for evaluating the nature of composites. XPS as well as contact angle measurements demonstrated that pine fibers and silane derivatives were effectively coupled. The mechanical analysis showed an increase in Young's and flexural moduli, by 12% and 130% respectively, and nonsignificant changes in the ultimate tensile strength were noted after surface modification. Water uptake measurements revealed a low water absorption by the materials, always lower than 2 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3706–3717, 2007     

硅烷偶联剂对二氧化硅填充硅橡胶界面及性能的影响

研究了硅烷偶联剂六甲基二硅氮烷（HMDS）、KH-570与Si O2增强体系在甲基乙烯基硅橡胶（MVQ）中的应用,同时考察了硅烷偶联剂的种类对MVQ复合材料界面及拉伸性能的影响。结果表明,Si O2经HMDS和KH-570表面处理后与MVQ的界面作用增强。相比于HMDS,含有KH-570的复合材料体系,Si O2能与MVQ分子发生化学作用,因此界面区域的相互作用进一步增强,吸附橡胶分子层厚度从16.065 nm增加到21.217 nm,硫化后复合材料具有更好的拉伸性能。     

Application of the microbond technique. IV. Improved fiber–matrix adhesion by RF plasma treatment of organic fibers

The microbond technique is a modification of the single-fiber pullout test for measuring interfacial shear strength. Briefly, a cured microdroplet of material is debonded in shear from a single fiber. Ultra-high modulus polyethylene (Spectra) fibers and aramid fibers (Kevlar) were treated using a radio frequency plasma in order to increase the interfacial bond between the fibers and an epoxy resin. The treated fiber surface was subsequently analyzed by X-ray photoelectron spectroscopy (XPS). Plasma treatment resulted in an increased concentration of oxygen containing functionalities on the fiber surface. The interfacial shear strength as determined by the microbond test increased by 118% for the Spectra fibers and by 45% for the Kevlar fibers with the same epoxy resin. Scanning electron microscopy indicated little change of the surface topography of either fiber following plasma treatment. Effects of friction and surface composition of the plasma-treated fibers is discussed. © 1993 John Wiley & Sons, Inc.     

Improvement of filler–rubber interaction by the coupling action of vegetable oil in carbon black reinforced rubber

Vegetable oil has been added in small amount to the rubber compound during mixing. It has been observed that the extent of cure obtained from the rheometric torque is lower for vegetable oil‐containing compounds. This has been manifested from their physical and tensile properties. The lower abrasion and hardness of vegetable oil‐containing compounds may be due to better plasticization and lower crosslink density. The lower tan ∂ at maximum torque indicates lower loss and heat generation. The vegetable oil‐containing compounds shows lower modulus, higher tensile strength, and elongation. All the compounds containing vegetable oil shows lower compression set and higher rebound resilience, tear strength, and flex cracking compared to the standard compound containing no vegetable oil. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 735–739, 2000     

Effect of fiber volume fraction,fiber length and fiber tow size on the energy absorption of chopped carbon fiber–polymer composites

Composite materials have the potential to reduce the overall cost and weight of automotive structures with the added benefit of being able to dissipate large amounts of impact energy by progressive crushing. To identify and quantify the energy‐absorbing mechanisms in candidate automotive composite materials, modified test methodologies were developed for conducting progressive crush tests on flat‐plate composite specimens. The test method development and experimental setup focused on isolating the damage modes associated with the frond formation that occurs in dynamic testing of composite tubes. The Automotive Composites Consortium (ACC) is interested in investigating the use of chopped carbon fiber–reinforced composites as crash‐energy absorbers primarily because the low costs involved in their manufacture make them cost‐effective for automotive applications. While many in the past have investigated the energy‐absorption characteristics in various continuous fiber–reinforced composite materials, no literature is available on the energy‐absorption and crushing characteristics of chopped carbon fiber–reinforced composite materials. Hence quasi‐static progressive crush tests were performed on composite plates manufactured from chopped carbon fiber (CCF) with an epoxy resin system using compression‐molding techniques, and the effect of material parameters (fiber volume fraction, fiber length, and fiber tow size) on energy absorption was evaluated by varying them during testing. Of the parameters evaluated, fiber length appeared to be the most critical material parameter determining the specific energy absorption of a composite material, with shorter fibers having a higher specific energy absorption than longer fibers, possibly because of the increased concentration of stress raisers in the shorter fiber specimens, resulting in a larger number of fracture‐initiation sites. The combination of material parameters that yielded the highest energy‐absorbing material was identified. The test observations and trends established from this work would help support the development of low‐cost energy absorbers for the automotive industry. POLYM. COMPOS. 26:293–305 2005. Published 2005 Society of Plastics Engineers.     

Short fiber–elastomer composites. Effects of matrix and fiber level on swelling and mechanical and dynamic properties

The effects of different types of elastomeric matrix (NR, SBR, CR, NBR) and several levels (10, 15, and 20 parts phr) of short fibers on mechanical properties of uncured and cured composites and on swelling behavior of composites in hydrocarbon solvent are studied. The variation of the dynamic properties, E′, E″, and tan δ is determined as a function of deformation amplitude, temperature, and vibration frequency in composite materials subjected to dynamic deformation. The increase of fiber level does not limit the orientation ability of the fibers, which in all materials seemed to be above 70%. The addition of fiber markedly reduces maximum swelling and entails an increase in material stiffness. In addition, the amount of dissipated energy is increased and hence transformable into heat upon fiber incorporation, which can reach up to 16 times the value corresponding to the matrix alone, in addition to an increase with strain amplitude. The effect is most pronounced in the presumed direction of fiber orientation. The marked reduction of elongation at break (up to values of 7–9% of those of unfilled samples) and the shape of stress-strain curves point to a good fiber-matrix adhesion. Dynamic glass transition temperature is displaced toward higher values as a consequence of matrix-fiber interaction, which increases proportionally to fiber level, thus proving a linear relationship between thermal displacement and the number of interactions between the two phases. By the same token, the apparent activation energy of the relaxation process is enhanced for fiber-containing materials as compared to the fiber-free. The fiber composites present a less prominent yet broader transition zone.     

Effect of polymeric silane coupling agents on adhesion of polypropylene and polystyrene to glass

The coupling performance of some polymeric silane compounds was compared with that of the monomeric silanes for adhesion of polypropylene (PP) and polystyrene (PS) to glass. A silylated poly-1,2-butadiene was found to be effective for PP and, on the other hand, some copolymers derived from styrenyl triethoxysilane or γ-methacryloxypropyl trimethoxysilane for PS. Benzoyl peroxide also showed a pronounced effect on the adhesion of PP, rather than that of PS. The adhesion strength was approximately correlated with the contact angles of the resin melts on the coated glass, intensively suggesting the dependence of compatibility between resinous matrix and coupling agent on the adhesion. Their critical surface tensions, thermal behavior, and infrared spectra were also measured to discuss the relationship between the surface constitution and the adhesion effect.