Effect Of Silane Coupling Agent Research Articles

Effect of silane coupling agent on mechanical properties, flame retardancy, and ceramifiable behavior of ceramifiable flame‐retardant silicone rubber composite

AbstractIn order to improve the dispersibility of inorganic fillers and enhance its ceramifiable flame‐retardant efficiency, the ceramifiable flame‐retardant silicone rubber composites were prepared using glass powder, zinc borate, ammonium polyphosphate, mica powder, platinum catalyst as ceramifiable flame‐retardant agent, and various silane coupling agents as interfacial modifier. The micromorphology, mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame‐retardant silicone rubber composites, as well as the flexural strength of the corresponding ceramics generated after pyrolysis of the composites were examined. The results reveal that the inclusion of silane coupling agents improves the dispersibility of ceramifiable flame‐retardant agents substantially. The mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame‐retardant silicone rubber composites are all improved. When compared to a composite without a silane coupling agent, the tensile strength of the composite can be improved by up to 1.9 times. Only 0.5phr silane coupling agent is required to raise the vertical combustion rating from V‐1 to V‐0, and the composite with 3 phr KH570 has a LOI value of 38.6. Meanwhile, the heat release rate of the composite is reduced to a certain extent, and the time to ignition and residue are dramatically enhanced after the addition of silane coupling agent in the cone calorimetry test. Moreover, flexural strength of the corresponding ceramics generated after pyrolysis of the composites rapidly increases with increasing silane coupling agent content, which can reach to 24.7 MPa with addition of 3 phr KH570.

Promoting Adhesion of Natural Rubber/Styrene-Butadiene Rubber to Brass Using Vietnamese Natural Rubber-Based Adhesives

Abstract This study aimed to enhance the adhesion between brass and NR/SBR rubber sheets using solvent-based adhesives derived from Vietnamese natural rubber. The effects of silane coupling agents and iron nanoparticles on adhesion were investigated. (3-Aminopropyl) Triethoxysilane (APTES) and iron nanoparticles are incorporated into the adhesives at varying concentrations to enhance adhesion levels. The characteristics of the adhesive, such as viscosity, peel-off tensile strength, and the surface morphology of the adhesive bond failure, have been studied and evaluated. The research results demonstrated that as the APTES content added to the adhesives increases gradually, the peel strength between the NR/SBR and brass significantly improves. The highest peel strength value achieved was 5.27 N/mm at 25 phr APTES, representing a 974% increase compared to the sample without silane. The continued addition of iron nanoparticles to the adhesive further improves the peel tensile strength, reaching a maximum value of 5.93 N/mm at a nanoparticle content of 5 phr. This information will be crucial for developing practical applications for this type of adhesive.

Effects of Silane Coupling Agents on Physical Properties of Simultaneous Biaxially Stretched Polylactide Film

Effects of Silane Coupling Agents on Physical Properties of Simultaneous Biaxially Stretched Polylactide Film

Effect of silane coupling agent grafted glycidyl methacrylate on hollow microsphere/natural rubber composites

AbstractTo improve the interfacial bonding between hollow microspheres (RiM01) and natural rubber (NR), the silane coupling agents γ‐aminopropyltriethoxysilane (KH550) and γ‐methacryloyloxypropyltrimethoxysilane (KH570) are used in this study as intermediate reaction platforms for the modification of (RiM01) with glycidyl methacrylate (GMA), respectively. In the process, GMA reacts with KH550 and KH570 through epoxy group ring‐opening and free radical polymerization, respectively. Different NR/RiM01@GMA composites are prepared by a mechanical blending method. The results show that the addition of GMA improves the interfacial bonding between RiM01 and NR, and enhances the vulcanization rate and cross‐linking degree of the rubber composites. When KH550 is used as the reaction platform, the tensile strength of the rubber composites increases by 24% compared to composites with unmodified RiM01, while when KH570 is used, the tensile strength increases by 18%. Additionally, the tear strength and abrasion resistance of the rubber composites increase by 13% and 15%, respectively, when KH570 is used as the reaction platform. At the same time, the filler‐matrix interaction is strongest when KH570 is used as the reaction platform, and the rubber composites exhibit the lowest rolling resistance and the best resistance to heat and oxygen aging.Highlight Modification of hollow microspheres by grafting GMA with KH550 and KH570, respectively. Improvement of rubber composite properties after modification GMA improves the interfacial bonding between hollow microspheres and rubber.

Multi-scale analysis and structural application of the synergistic enhancement effect of silane coupling agent on the interface between PVA/rubber and cement

This study employs polyvinyl alcohol (PVA) fibers and silane coupling agent (SCA) to augment rubberized concrete mechanical prowess. A multiscale investigation delves into the synergistic enhancement mechanism of SCA on the interfaces of PVA/cement and rubber/cement, considering macroscopic mechanical properties, microscopic structural characteristics, and nanoscale interface interactions. Initially, fundamental mechanical performance tests reveal a notable enhancement in compressive and flexural strength with the inclusion of SCA and PVA fibers in rubberized concrete. Subsequently, observations of corresponding composite concrete slices are conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results manifest gel and polymer filling interface gaps, with SCA fostering a tighter amalgamation of the two interfaces, effectively rectifying interface defects and elucidating its bonding effects at the microscopic interface. Molecular dynamics (MD) modeling and simulation analyses of PVA/C-S-H and rubber/C-S-H, pre- and post-SCA modification, demonstrate that SCA mitigates interface effects, reinforcing hydrogen bonding, van der Waals interactions, Ca-H coordination bonds, and stability. This augmentation enhances interface adhesion energy, fortifying the weak interface bonding between PVA fibers, rubber, and inorganic silicate (C-S-H). Ultimately, portal frame experiments substantiate that incorporating fiber rubberized concrete into structures not only fails to diminish but marginally enhances the load-bearing capacity of the framework. This research furnishes concrete and innovative solutions for sustainable development while providing a valuable reference for the future application of PVA fiber rubberized concrete materials in practical engineering endeavors.

Utilization of composite particles with customizable cross-linked lignin patches for dental cleansing

Lignin, a natural polyphenol polymer, is a biocompatible, cost-effective and accessible material. To fully utilize the benefits of lignin, it is crucial to transform its complex macromolecules into nanoscale particles in a single solvent. In this research, an assembly-mediated internal cross-linking method in single solvent was proposed to manufacture cross-linked lignin colloidal particles with nanoscale particle size controlled to be around 50 nm. Then, cross-linked lignin composite particles with a unique “patchy” structure for dental cleansing were obtained by rapidly grafting the cross-linked lignin colloidal particles onto the surface of silica microspheres through the bridging effect of silane coupling agent. The resulting composite particles have rivets with adjustable hardness, significantly lower than traditional abrasives like silica in both hardness and modulus. Through the group cleansing behavior of soft interlocking, a breakthrough has been achieved in the high solid content agglomeration friction mode of traditional abrasives, which effectively reduces tooth wear and exhibits an excellent plaque removal effect.

Core-Shell Rubber Nanoparticle-Modified CFRP/Steel Ambient-Cured Adhesive Joints: Curing Kinetics and Mechanical Behavior.

Externally bonded wet-layup carbon fiber-reinforced polymer (CFRP) strengthening systems are extensively used in concrete structures but have not found widespread use in deficient steel structures. To address the challenges of the adhesive bonding of wet-layup CFRP to steel substrates, this study investigated the effect of core-shell rubber (CSR) nanoparticles on the curing kinetics, glass transition temperature (Tg) and mechanical properties of ambient-cured epoxy/CSR blends. The effects of silane coupling agent and CSR on the adhesive bond properties of CFRP/steel joints were also investigated. The results indicate that CSR nanoparticles have a mild catalytic effect on the curing kinetics of epoxy under ambient conditions. The effect of CSR on the Tg of epoxy was negligible. Epoxy adhesives modified with 5 to 20%wt. of CSR nanoparticles were characterized with improved ductility over brittle neat epoxy; however, the addition of CSR nanoparticles reduced tensile strength and modulus of the adhesives. An up to 250% increase in the single-lap shear strength of CFRP/steel joints was accomplished in CSR-modified joints over neat epoxy adhesive joints.

Effect of Silane Coupling Agent Treatment of Aggregates on Mortar Workability, Strength and Interfacial Microscopic Properties

In this study, 3-aminopropyltriethoxysilane (KH550) and vinyltrimethoxysilane (KH171) were used to modify aggregates and prepare aggregates with different surface wettability. The effect of silane coupling agents on aggregate surface properties was characterized through FT-IR, XPS, contact angles and aggregate water absorption. The influence of the aggregate’s surface wettability on the interface properties was discussed using MIP, SEM, BSE and nanoindentation, and then the influence mechanism of the interface microscopic properties on the macro-properties of mortar was revealed. The results showed that the type of silane has an intense impact on the surface properties of aggregates. KH550-modified aggregates increased the contact angle from 23.6° to 59°, while KH171-modified aggregates increased it from 23.6° to 91.6°. Silane-modified aggregates reduced the surface hydrophilicity, thereby reducing the water absorption and improving the mortar’s workability. However, KH550-modified aggregates exhibited a more effective enhancement of the mortar’s mechanical properties. Specifically, KH550-modified aggregates reduced the aggregate’s surface hydrophilicity, consequently alleviating the interfacial edge effect. This led to a 10% increase in the compressive strength of the mortar, an 11.6% reduction in the porosity, an 8.4% decrease in the interfacial porosity, and a 42.3% increase in the elastic modulus of the ITZ. Meanwhile, the cement matrix obtained a greater amount of water for cement hydration, resulting in an increased degree of hydration and an 18.5% increase in the elastic modulus of the cement matrix. The improvement in the ITZ between the modified aggregates and the cement matrix is considered to be one of the fundamental reasons for the enhancement of the mortar’s performance.

Multi-scale analysis of the synergistic strengthening effect of silane coupling agent on PVA and cement interface

Conventional polyvinyl alcohol (PVA) cementitious composites are susceptible to macroscopic cracking when subjected to reduced compressive strength, diminished toughness, tensile impact and other external loads. In order to address these issues, this study investigates the mechanism of the modifier's influence by modifying PVA fibers with a silane coupling agent (KH560) through experimental studies and molecular dynamics simulations for multiscale computational analyses. Macro test results showed that the mechanical properties of PVA fiber concrete were significantly improved after silane coupling agent modified PVA fiber. The microscopic test results showed that the SCA-modified polymer film acted as a bridging ligament in the interfacial transition zone, effectively prevented crack extension, and enhanced the interfacial adhesion between the organic components of the PVA fibers and the cement matrix. Nanoscale molecular dynamics simulations showed that the hydrated calcium silicate exhibited a stable skeletal structure, while the introduction of SCA expanded the hydrogen bonding interactions at the interface, thus enhancing its stability.

Effect of silane coupling agent on the ultraviolet weathering behavior of polylactic acid based composites

Polylactic acid (PLA) is a promising material due to its biodegradability and compatibility. However, the limited resistance to ultraviolet (UV) degradation of PLA composites hinders their use in automotive interior materials. In our previous work, we successfully prepared 3D printed filaments by combining KH550-treated micro-nano rice husk (MNRH) fibers with KH570-treated PLA, which exhibited favorable performance. This study aimed to investigate the effects of silane coupling agents, MNRH, and accelerated UV weathering time on the photodegradation behavior of 3D printed PLA-matrix composites reinforced with MNRH. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were utilized to characterize the 3D printed PLA-matrix composites. Furthermore, an exponential equation between tensile strength and UV weathering time was established, providing theoretical guidance for predicting the service life of automotive interior materials based on PLA composites. The morphological characterization experimental results indicate that with prolonged UV aging time, both PLA and RH6-KH550/KH570 composite materials transitioned from transparency to translucency. This transition can be attributed to the rupture of polylactic acid molecular chains and chemical bonds during the UV aging process. FTIR test results revealed the formation of carboxylic acid in the composite, and the reduction of C = O absorption intensity indicated that MNRH and silane coupling agents exhibited a stabilizing effect on the UV durability of the RH6-KH550/KH570 composite. TGA and DSC results indicated that KH550 and KH570 delayed the photodegradation rate of PLA-matrix composites.

Immediate and Late Repair of Microhybrid Resin Composites: Effect of Silane Coupling Agent, Universal Adhesives and Photo Polymerization.

This study investigated the effect of silane coupling agent and universal adhesive application on repair bond strength of resin-based composite after bur grinding. Microhybrid resin composite (Charisma Smart) blocks (N=80; 8x8x4 mm3) were prepared, aged (37°C; 1 month), roughened, etched and randomly divided into two groups. Silane was applied to half of the groups (Porcelain Primer, Bisco), before one of the following universal primers/adhesives was applied: a) Scotchbond Universal (3M), b) All-Bond Universal (Bisco), c) G-Premio Bond (GC), and d) Clearfil SE Bond (Kuraray). In each adhesive group half of the group was photo-polymerized. The blocks were repaired with the same size resin composite and segmented into beams. Half of the beams were subjected to micro-tensile bond test (1 mm/min), while the other half was aged (37°C; 6 months) prior to testing. Failure modes were analyzed using Scanning Electron Microscopy (SEM). Data were analyzed using repeated measures of ANOVA, Tukey's post-hoc, and paired t-tests (alpha=0.05). The silane application did not affect the repair bond strength regardless of photo-polymerization of the adhesive resin. The repair bond strength decreased significantly after 6 months when adhesive resin was not photopolymerized (p⟨0.05). Photo-polymerizing universal adhesives might ensure higher repair bond strength and its maintenance after aging.

Effect of silane coupling agent and concentration on fracture toughness and water sorption behaviour of fibre-reinforced dental composites.

This paper presents the effect of silane treatment of S-2 Glass fibres on the fracture toughness and water sorption/solubility behaviour of fibre-reinforced flowable dental composites. The effect of epoxy- and methacrylate-based silane coupling agents (SCAs) on the mechanical strength and hydrolytic properties were investigated. The concentration of the selected SCAs on the mechanical and physical properties were investigated. The influence of molecular structure and concentration in the interfacial adhesion at the fibre-matrix interfaces was also studied. Short S-2 Glass fibres of 250µm in length and 5µm in diameter were etched with acid to remove any impurities and roughen the surface. The acid-etched fibres were silane treated with 3MPS, 3GPS, and 8MOTS at different concentrations by weight (%). The silane-treated fibres were incorporated at 5 % into the dental resin mixture. Untreated fibres were added at 5 % to the dental resin mixture and served as the control group. The physical properties such as water sorption, solubility, and desorption along with mechanical properties such as fracture toughness and total fracture work of the fibre-reinforced dental composites grafted with the above-mentioned SCAs were evaluated. The surface morphology of the fractured surface was studied and analysed. The fracture toughness tests showed that the dental composites grafted with optimum weight per cent (wt. %) concentration of the SCA had a better stress intensity factor (KIC) when compared to the 2.0wt. % and 3.0wt. % concentration. The KIC value of dental composites grafted with untreated surface etched glass fibres was less than the KIC values of dental composites grafted with optimum concentrations of 3MPS, 3GPS, and 8MOTS by 81.6 %, 38.6 %, and 110.5 %, respectively. A similar trend was found while investigating the total work of fracture of the dental composites, between optimum concentration, 2.0wt. % and 3.0wt. % concentration of respective SCA. The increase in silane concentration also led to an increase in the water sorption/solubility characteristics. The absorption of water was most severe in the fibre-reinforced dental composites without silane treatment (32.9µg/mm3). The ANOVA results showed that the fibre-reinforced dental composites grafted with 8MOTS at optimum concentration showed an increase in fracture toughness when compared to optimum concentrations of 3GPS and 3MPS by 51.9 % and 15.9 %, respectively. The enhanced mechanical and physical characteristics are due to the increased adhesion between the fibre and silane achieved from the optimum wt. % concentration of 8MOTS. Similarly, dental composites grafted with 8MOTS at optimum concentration showed a decrease in water sorption characteristics when compared to optimum concentrations of 3GPS and 3MPS by 18.2 % and 0.6 %, respectively. The decreased water sorption characteristics at the optimum concentration of 8MOTS could be due to the reduced availability of reactive hydroxyl groups and the hydrophobic characteristics of 8MOTS. Silane coupling agents (SCAs) are important components of dental composites. The type and concentration of SCA have a significant effect on material properties. The current study focuses on understanding the effects of different SCAs and wt. % concentrations on the interfacial fracture behaviour and the influence of different SCAs on the water sorption and solubility behaviour of S-2 Glass fibre-reinforced flowable dental composites.

Verification of mechanism for effect of silane coupling agent modification of polyethylene (PE) fiber's surface on strain-hardening behavior of high-strength cementitious composites

To fully understand the mechanism for the effect of silane coupling agent (SCA) modified polyethylene (PE) fiber on the strain-hardening behavior of high-strength cementitious composites (HSCC), an experimental research has been conducted, including direct tension and microstructural tests using optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed that, compare to the interfacial bonding between original PE fiber and very high strength matrix of cementitious composite at water/binder ratio (W/B) of 0.18, the interfacial bonding was strengthened after the modification of PE fiber's surface by SCA solution of 3% concentration, which subsequently resulted in the improvement of initial-cracking stress, ultimate tensile stress and ultimate tensile strain from 5.20 MPa, 6.34 MPa and 0.68% to 7.26 MPa, 8.01 MPa and 5.06%, respectively. The mechanism for the improvement in strain-hardening behavior of HSCC with SCA-modified PE fiber was that the physicochemical interactions occurred between the SCA-modified PE fiber and the matrix. Among these interactions, amino and hydroxyl groups connected to the PE fiber improved the hydrophilicity of fiber surface, which enhanced the physical bonding between the SCA-modified PE fiber and the matrix. More importantly, two types of chemical interactions have been proved to establish chemical bonding between the PE fiber and matrix, namely, the condensation reaction between hydroxyl groups of the modification layer on the PE fiber and hydroxyl groups of C–S–H gels in the matrix, and the combination of the polymer of SCA's hydrolysates with Ca(OH)2 released by cement hydration.

A review study on coupling agents used as ceramic fillers modifiers for dental applications

The aim of this study is to provide a review on silanized composite performance when exposed in a complex wet aqueous environment and the role of titanium coupling agent as a more stable and reinforcement material in the construction of dental composites. Silanes are considered as the most dominant materials used for surface modification of the filler added to the polymer material in dental applications. Due to the presence of silica in the silane structure, so, the silane coupling agent were considered to be more effective in modifying materials which are consisting of silica because of the similarity in their ordered structure. Silanes are relatively characterized by dehydration inside the oral aqueous environment. On the other hand, titanate coupling agents are effective in serving at a wet environment, because its ability to react with the positive proton available on the surface of the filler (H+). TCAs are superior in performance in comparison to silane by creating a strong internal bonding between the filler and polymer matrix, and having a significant effect on the dispersion and resolving of particles agglomeration and good hydrolytic stability inside the mouth. This paper presents a comparative study between the effects of silane coupling agents against the TCAs performance in oral environment.

Study on the Stability of Porous Silicon Energetic Materials

Porous silicon has been widely studied due to its high explosion characteristics, less harm to the environment and compatibility with all silicon based production processes. At present, it has been used in military, national defense and other fields. In this paper, porous silicon was prepared by electrochemical anodic oxidation. The electrolysis time was 35 min, the current density was 50 mA/cm2, and the electrolyte was HF: DMAC=5:1 (volume ratio). The effects of silane coupling agents (KH550 and KH560) and cathodic reduction treatment on the life of porous silicon were investigated. The results show that the life of porous silicon chips treated by cathodic reduction+KH560 is longer, and the morphology of porous silicon chips treated by cathodic reduction+KH560 is better.

실란 커플링제 첨가에 따른 TPU/EVA/Silica 컴파운드의 수분흡수 및 기계적 물성 연구

폴리우레탄(thermoplastic polyurethane, TPU)은 고무 소재의 대체 신소재로 주목받고 있다. 그러나 TPU는 수분 친화성이 높아, 습윤한 환경에 취약하여 상용화의 한계를 지니고 있다. 이를 해결하고자 수분흡수율이 낮고 타 수지와 친화성이 높은 ethylene vinyl acetate(EVA)를 말레산 무수물(maleic anhydride, MAH)이 그라프트된 EVA-g-MAH를 이용하여 블렌드(TPU/EVA)를 제조한다. 하지만 이 경우 기계적 물성이 떨어지는 단점이 있다. 따라서 본 연구에서는 기계적 물성을 보완하고자 실란 커플링제를 이용하여 표면을 개질시킨 실리카 필러를 사용하여 복합체를 제조하였다(TPU/EVA/Silica). TPU/EVA/Silica의 특성을 분석한 결과, 실란 커플링제로 표면 개질된 실리카 필러가 들어간 컴파운드의 경우 실리카의 분산성이 향상되어 수분 흡수율의 감소와 기계적 특성이 향상되는 결과를 보였다. 그러나, 3 phr 이상의 실란 커플링제가 첨가되었을 때 가소제와 같은 역할로 분산성이 저하되고 기계적 물성의 감소와 수분 흡수율이 증가하는 결과를 확인하였다.

Modified silica to strengthening and toughening soft polyvinyl chloride

AbstractModifying nanoparticles for polymer nanocomposites is important for multifunctional and low‐cost developmental direction. However, nanoparticles have several deficiencies, such as dispersion, agglomeration, and poor binding ability with most polymers. This work used soft polyvinyl chloride (PVC with 33.1% plasticizer volume) as the matrix. Polycaprolactone (PCL) was synthesized on the surface of SiO2 by the bridging effect of silane coupling agent (SiO2‐PCL), which was expected to improve the bond strength between SiO2 and soft PVC matrix. Moreover, it enhanced the dispersion of SiO2 in the PVC matrix. The results revealed that SiO2‐PCL was nanodispersed in a soft PVC matrix and played a plasticizer role in the composite, which enhanced the tensile strength and elongation at break of PVC composites. The thermal stability and solvent extraction stability of PVC composites elevated with the increase of SiO2‐PCL content. When the content of SiO2‐PCL was 8 wt%, the tensile strength (14.54 MPa) and elongation at break (149.47%) of PVC composites were the highest, 64.36% and 60.48% higher than those of unfilled PVC, respectively. It was indicated that PVC composites were dramatically toughened and strengthened by modified SiO2, improving their overall performance.

The modification mechanisms of silane coupling agent (SCA) on the physical properties of thermosetting polyurethane asphalt binder (PUAB)

• The addition of SCA enhanced the physical properties of PUAB . • A viscosity model based on the dual-Arrhenius theory was established. • SCA had physical and chemical connection on the polyurethane-asphalt interface. • A deformation layer formed by SCA was a significant role in PUAB system. The paper attends to investigate the influence of silane coupling agent ( SCA ) on the novel thermosetting polyurethane ( PU ) asphalt binder ( PUAB ). Initially, the storage stability, thermal stability and viscosity of PUAB are evaluated with the separation test, thermogravimetric analysis ( TGA ) and Brookfield viscosity, respectively. Then the mechanical properties, elastic recovery performance and permanent deformation resistance of PUAB are examined by the universal testing machines and dynamic shear rheometer ( DSR ), respectively. Finally, the modification mechanism is analyzed by Fourier transform infrared spectroscopy ( FTIR ). The results show that the thermal stability and storage stability of PUAB are improved by adding SCA . Then, a viscosity model based on the dual-Arrhenius theory is established and well predicts the effect of SCA on viscosity-time relationship of PUAB . Furthermore, the addition of SCA significantly enhance mechanical behaviors of PUAB where the complex modulus of PUAB rise, a 16 % of tensile strength increase and a 98.4 % of the elastic recovery (58 °C/0.1 kPa) are reached with 1 % SCA adding. Data from chemical investigations suggest that SCA connect between asphalt and PU to form groups of oxazolidinone, then promoting better compatibility. Then formed deformation layer can relieve the stress and improve the interfacial bond strength. Accordingly, this finding provides a feasible approach to the performance improvement of PUAB .

Sulphate resistance of silane coupling agent reinforced metakaolin geopolymer composites

Sulphate resistance is an important index for evaluating geopolymer durability. This study investigates the beneficial effects of silane coupling agent (SCA) addition on the sulphate corrosion resistance of metakaolin-based geopolymer composites via strength tests and various characterisation techniques such as XRD, FTIR, SEM-EDS, and 29Si NMR. The results show that the compressive and tensile strengths and corrosion resistance coefficient of the geopolymer first increased, then decreased with increasing SCA dosages. The geopolymer incorporated with the optimum dosage of 0.1 wt% SCA exhibits the highest strengths, fluidity, and sulphate resistance coefficient. SCA addition effectively compacts the pore structure, thus making it difficult for SO42− to invade the matrix. The SEM-EDS diagram reveals that before and after sulphate attack, the Na content of the pure geopolymer decreased from 7.37 wt% to 3.84 wt%, and the mass ratio decreased by 47%. However, the Na content of the geopolymer composite modified with SCA decreased from 5.64 wt% to 4.85 wt%, and the mass ratio only decreased by 14%, indicating that the addition of SCA reduced the Na precipitation rate of the geopolymer in the sulphate environment. The 29Si NMR spectrum also reveals that the addition of SCA inhibits the resonance peak shift from Q4 to Q3 after 56 d of sulphate attack, which indicates improvement in the stability of the three-dimensional network structure in the geopolymer.

RETRACTED: Effect of Silane Coupling Agent on the Mechanical Properties of Oil Palm Frond Fiber Composite

Retracted article: In this study, the influence of silane coupling agent on the matrix/ fiber interface bonding and its effect to the mechanical properties of oil palm frond fiber reinforced polyester composites were investigated. Tensile and flexural properties of the composites were studied at 0 - 10.2 volume fraction (% fiber content). Results showed an increasing trend in tensile modulus while tensile strength and flexural strength reduced as the fiber content increased. Higher tensile modulus values were observed in silane treated fiber composites due to additional fiber/ matrix interaction and increment in polyester molecular chain mobility constraint. Reduction in tensile strength is caused by decrease in the matrix crystallinity and formation of stress concentration spots emerging from interface discontinuity. These obstructions, however, were reduced by fiber surface modification, which improved the tensile strength. Enhanced fiber dispersion upon surface modification was unveiled through scanning electron micrograph images.