Effect of silane‐coupling agents on interfacial properties of CF/PI composites

In this article, to form a structure‐controlled interface, carbon fiber (CF) surfaces were first activated by plasma technique and then hydroxylated by LiAlH₄ treatment, and then were reacted with a suit of silane‐coupling agents terminated with desired functional groups to form thin films, which further reacted with polyimide (PI) resin to generate a strong adhesion interface. The morphology, structure, and composition of CF surfaces before and after treatment were investigated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS), respectively. The results of FTIR and XPS analysis showed that silane‐coupling agents were successfully chemisorbed onto the CF surfaces by the hydrolysis and condensation reactions. The interfacial shear strength of the CF/PI microcomposites was evaluated by the microbond technique. The results showed that the types of the interfacial functional groups, especially the vinyl end groups in vinyltriethoxysilane (VS), which can react with PI resin, had very significant influence on the improvement of the interfacial adhesion properties of composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Natural rubber vulcanizate reinforced by modified coal‐shale‐based fillers

Coal shale is considered a waste material in coal mining and washing processes. It comprises both inorganic and organic components. In this study, two kinds of coal shale were microcracked, burned, modified by enoxidation natural rubber (ENR), and then used as reinforcing fillers for natural rubber (NR). The NR vulcanizates reinforced with this modified filler were characterized by bounded rubber content, apparent crosslink density, and various mechanical property tests. The results show that the ultramicro coal‐shale powder was a good filler for NR. It could be mixed quickly, and it dispersed well in NR, which resulted in a significant enhancement. After modification by ENR, the reinforcement properties were improved further. The results suggest that this new type of filler could be used as a semireinforcing filler to replace or partially replace carbon black. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1397–1400, 2004     

Hybridized reinforcement of natural rubber with silane‐modified short cellulose fibers and silica

Natural‐rubber‐based hybrid composites were prepared by the mixture of short cellulose fibers and silica of different relative contents with a 20‐phr filler loading with a laboratory two‐roll mill. The processability and tensile properties of the hybrid composites were analyzed. The tensile modulus improved, but the tensile strength and elongation at break decreased with increasing cellulose fiber content. The scorch safety improved with the addition of 5‐phr cellulose fiber in the composites. The Mooney viscosity significantly decreased with increasing cellulose fiber content. To modify the surface properties of the cellulose fiber and silica fillers, a silane coupling agent [bis(triethoxysilylpropyl)tetrasulfide, or Si69] was used. The effects of Si69 treatment on the processing and tensile properties of the hybrid composites were assessed. We found that the silane treatment of both fillers had significant benefits on the processability but little benefit on the rubber reinforcement. The strength of the treated hybrid composite was comparable to that of silica‐reinforced natural rubber. Furthermore, to investigate the filler surface modification and to determine the mixing effects, infrared spectroscopic and various microscopic techniques, respectively, were used. From these results, we concluded that the fillers were better dispersed in the composites, and the compatibility of the fillers and natural rubber increased with silane treatment. In conclusion, the hybridized use of short cellulose fibers from a renewable resource and silica with Si69 presented in this article offers practical benefits for the production of rubber‐based composites having greater processability and more environmental compatibility than conventional silica‐filler‐reinforced rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphology and properties of silane‐modified montmorillonite clays and clay/PBT composites

Commercially available organoclay (Closite 30B) was modified by using 3‐aminopropyltriethoxysilane (APS) via a silylation reaction. Sodium clay (Closite Na) was treated by APS directly as a control. Such modified clays were further melt‐compounded with polybutylene terephthalate (PBT). The morphology and properties of the modified organoclays were characterized with X‐ray diffraction (XRD), transmission electrical microscopy (TEM), Infra‐red spectroscopy, contact angle measurement, and thermogravimetric analysis (TGA). The effects of modified clays on the crystallization behavior of PBT were characterized by differential scanning calorimetry. The basal spacing of Closite Na was enlarged from 1.01 to 1.41 nm after APS treatment, indicating that the APS was intercalated into the clay intergalleries as a monolayer. The basal spacing of Closite 30B increased slightly after APS treatment, partially resulted from the reactions between the APS and hydroxyl groups on the intercalant of Closite 30B. Closite 30B was found to be exfoliated disorderly after melt‐compounded with PBT. The APS‐modified Closite 30B only dispersed as swollen elliptical clay aggregates, in which the silicate layers were orderly intercalated. TGA results showed that the decomposition temperature at 5% weight loss of Closite 30B was increased from 250 to 270°C after APS treatment. A significant increase in the degree of crystallinity of PBT was observed in the exfoliated PBT/30B composite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical properties of silane‐treated,silica‐particle‐filled polyisoprene rubber composites: Effects of the loading amount and alkoxy group numbers of a silane coupling agent containing mercapto groups

The surface treatment of spherical silica particles with a silane coupling agent with mercapto groups was carried out. The treated silica particles were incorporated within polyisoprene and then vulcanized. The effects of the loading amount and alkoxy group number of silane on the stress–strain curve of the filled composite were investigated. For this purpose, silanes with dialkoxy and trialkoxy structures were used. The loading amount of silane on the silica surface was varied from 1 to 8 times the amount required for monolayer coverage. The stress at the same strain increased with the silane treatment, and it was higher in the dialkoxy structure than in the trialkoxy structure above 300% strain. There was no significant influence of the loading amount on the stress for the trialkoxy silane structure. However, the stress was influenced by the loading amount, and the maximum stress was observed at 4 times the silane amount required for monolayer coverage for the dialkoxy structure. The stress had a good relationship with the crosslinking density of silica‐filled polyisoprene rubber (measured with a swelling test). The reinforcement effect by the silane treatment of silica was found to be affected strongly both by the entanglement of the silane chain and polyisoprene rubber matrix and by the crosslinking reaction between the mercapto group of silane and polyisoprene rubber in the interfacial region. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Film blowing of silane‐modified polyethylene

The grafting of vinyltriethoxysilane (VTES) onto polyethylene (PE) with the help of small amounts of peroxides was investigated to film‐blow these modified materials. The degree of crosslinking was kept very low to achieve good melt processability and improved mechanical properties. The possibility of obtaining modified PE films with improved properties and regularly distributed crosslinking with a single processing step demonstrates the uniqueness of this study. The additive concentration was established through preliminary studies; with a batch mixer, it was possible to process the modified PE in the film‐blowing operation. Water treatment of the modified films after film blowing allowed for improved properties without the processability being affected. The modification of PE was followed with mechanical, rheological, and extraction tests and with calorimetric analyses. The variations of the main mechanical properties of the films were very important from an application point of view. The elastic modulus and tear strength of the films for both extrusion directions (machine and transverse) increased with the VTES concentration increasing and even more with the addition of a small quantity of a peroxide. Some reductions of the tensile strength and elongation at break were observed, but these reductions were not considerable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Unexpected behavior between polystyrene and untreated and silane‐treated glass beads in filled polymeric composites

Attempting to extend the database of work reported earlier, the practical adhesion between a glass filler, modified by various silane‐coupling agents, and a polystyrene matrix is measured and compared with predictions based on a generalized thermodynamic criterion. Measurements leading to adhesion failure are carried out using the single‐particle composite method, in which a rectangular polymer specimen containing a single untreated or silane‐treated glass bead is subjected to increasing uniaxial tensile stress until interfacial failure, as observed using a microscope, occurs at one of the poles of the sphere. The results show no difference in adhesion strength between an untreated and a silane‐treated glass bead, and the interfacial failure mechanism for the polystyrene composites is markedly different from that observed for previously studied systems. Crazes originate at the particle pole at low values of the applied stress and continue to form along the interface with continued strain. A dye test performed on filled composites confirms that the polystyrene is not wetting the untreated glass beads. More studies must be done to determine the origin of the anomalous failure and wetting behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 521–526, 2003     

In situ sol‐gel process of polystyrene/silica hybrid materials: Effect of silane‐coupling agents

The polystyrene–silica hybrid materials have been successfully prepared from styrene and tetraethoxysilane in the presence of silane‐coupling agents by an in situ sol‐gel process. Triethoxysilyl group can be incorporated into polystyrene as side chains by the free‐radical copolymerization of polystyrene with silane‐coupling agents, and simultaneously polystyrene–silica hybrid materials with covalent bonds between two phases were formed via the sol‐gel reaction. The 3‐(trimethoxysilyl)‐propyl‐methacrylate (MPS) systems were found to be more homogeneous than the corresponding allytrimethoxysilane hybrid system of equal molar content. In the MPS‐introduced system, the thermal properties of the materials were greatly affected by the presence of MPS. FTIR results indicate successful formation of the silica networks and covalent bonding formation of coupling agents with styrene. The homogeneity of polystyrene–silica systems was examined by scanning electron microscope and atomic force microscope. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2074–2083, 2002     

Crystallization and melting of highly filled polypropylene composites prepared with surface‐treated fillers

Polypropylene (PP) composites with high filler content have been prepared with surface‐treated fillers. The effect of the filler is twofold; nucleation of crystallization occurs, though the PP is also adsorbed onto the filler thereby retarding its motion. Differential scanning calorimetry has been used to study the crystallization of the PP. Melting and recrystallization during melting has been characterized by differential scanning calorimetry. The properties of the composites are more than an additive combination of the filler and polymer. In the case of highly filled composites, the morphology of the PP is important in limiting brittleness and for the strength of the interface between filler and polymer. Surface treatment of the filler has been found to have a significant control over the morphology and properties of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1942–1948, 2001     

偶联剂对淀粉/丁苯橡胶复合材料性能的影响

采用乳液共混法制备了淀粉/丁苯橡胶(SBR)以及间苯二酚甲醛树脂(RF)改性淀粉/SBR复合材料,考察了偶联剂对2种复合材料硫化特性、力学性能的影响,并用扫描电镜观察了其相态结构。结果表明,各种偶联剂都能在一定程度上提高淀粉/SBR复合材料的拉伸强度和撕裂强度,其中γ-氨基丙基三乙氧基硅烷(KH-550)和N-β(氨基乙基)-γ-氨丙基三甲氧基硅烷(KH-792)的增强效果最为显著;采用RF对淀粉进行改性,RF改性淀粉/SBR复合材料的力学性能较之淀粉/SBR复合材料的力学性能有了进一步提高。橡胶相与淀粉相界面结合的改善是RF改性淀粉/SBR复合材料力学性能提高的主要原因。     

丁苯橡胶/硅烷偶联剂改性勃姆石复合材料的制备与性能

采用直接共混法制备了丁苯橡胶(SBR)/勃姆石(BM)复合材料,研究了BM用量和硅烷偶联剂双-[γ-(三乙氧基硅)丙基]四硫化物(Si 69)的表面改性对复合材料力学性能、微观形貌、硫化特性、动态力学性能的影响.结果表明,BM能够有效提高SBR硫化胶的力学性能,而Si 69处理可以进一步改善复合材料的力学性能以及BM与...     

Characterization of organoclay‐networks modified low‐temperature hydrogenated nitrile butadiene rubber composites

The low‐temperature grade hydrogenated nitrile butadiene rubber (LTG‐HNBR) composites with organoclays were successfully prepared for the purpose of using the clay‐networks to improve bulk properties. In order to construct different clay‐networks, three montmorillonite (MMT) modified by surfactants were added and then their dispersions and affinities in the rubber were compared. Transmission electron microscope and small‐angle X‐ray scattering results showed that 10 phr organoclays form partially exfoliated and intercalated structures in the matrix despite of modifier types. FTIR and particle analysis data display that increasing the number of alkyl tails of modifier molecules decreases the affinities of clays and their extent of intercalation in rubber whereas the special modifier with coupling agent enhances their compatibility with the bulk. The mechanical, oil resistance, and thermal properties of the composites are greatly reinforced by clay‐networks which parallel their interactions. Importantly, the addition of clays barely changes glassy temperature (T_g) of rubber bulk, but it improves its low‐temperature elasticity. Therefore, it is stressed that organoclay hybrid networks are very useful to modify low‐temperature rubber. We believe that LTG‐HNBR composites with organoclays may serve some applications of oil‐sealing products. POLYM. COMPOS., 35:1306–1317, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of konjac glucomannan‐acrylic acid‐diatomite composites

A novel konjac glucomannan (KGM)‐acrylic acid‐diatomite composite (KGAD) was synthesized by the solution polymerization of partially neutralized acrylic acid (AA) on to KGM and diatomite (DT), using potassium persulfate as a free radical initiator, in the presence of Trimethylolpropane Trimethacrylate (TPTA) as a crosslinking agent. The structure and morphology of KGAD were characterized by using FT‐infrared, X‐ray diffraction, scanning electron microscopy. Besides, the thermal stability as well as the salt absorption of the composites was investigated by the thermogravimetric analysis and the swelling rate test, respectively. The results showed that the interactions between KGM‐AA (KGA0) and DT could be generated through hydrogen bond formation. Besides, the crystal of composites became rules and grew well with the addition of DT. It was also found that the appropriate amount of DT could be dispersed uniformly with a single crystal state in the matrix of KGA0 while excessive DT caused aggregation, inducing an irregular distribution in the matrix. In addition, the thermal stability of KGAD was improved based on the introduction of DT into the polymer network. POLYM. COMPOS., 37:3384–3390, 2016. © 2015 Society of Plastics Engineers     

Novel coupling agents for PVC/wood‐flour composites *

Effective interfacial adhesion between wood fibers and plastics is crucial for both the processing and ultimate performance of wood–plastic composites. Coupling agents are added to wood–plastic composites to promote adhesion between the hydrophilic wood surface and hydrophobic polymer matrix, but to date no coupling agent has been reported for PVC/wood‐fiber composites that significantly improved their performance and was also cost‐effective. This article presents the results of a study using chitin and chitosan, two natural polymers, as novel coupling agents for PVC/wood‐flour composites. Addition of chitin and chitosan coupling agents to PVC/wood‐flour composites increased their flexural strength by ～20%, their flexural modulus by ～16%, and their storage modulus by ～33–74% compared to PVC/wood‐flour composite without the coupling agent. Significant improvement in composite performance was attained with 0.5 wt% of chitosan and when 6.67 wt% of chitin was used. J. VINYL ADDIT. TECHNOL., 11:160–165, 2005. © 2005 Society of Plastics Engineers     

Protein‐polyisoprene rubber composites

Hydrolyzed proteins previously shown to aggregate in aqueous solution were compounded into synthetic polyisoprene rubber (IR). Modulus increases of up to 232% resulted from protein reinforcement of IR. Increased hydrogen bonding on amine groups and the presence of β‐sheets in the protein phase were observed via Fourier transform infrared (FTIR) spectroscopy. The total β‐sheet amount relative to the IR content strongly correlated to the modulus and varied with the protein concentration, protein aggregation state, and compounding conditions. Isotropic protein aggregates on the order of hundreds of nanometers were observed by scanning electron microscopy with energy dispersive x‐ray spectroscopy (SEM‐EDX). The aggregates were evenly dispersed throughout the rubber matrix after compounding. The composite glass transition temperature (T_g) was unchanged from the control, which indicated that the protein and rubber existed as two discrete phases. Remarkably, protein β‐sheet structures were observed in FTIR even after rubber compounding under harsh conditions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46026.     

Blend compatibilizers based on silane‐ and maleic anhydride–modified polyolefins

Polypropylene (PP)/polyamide blends were compatibilized with PP modified with vinylsilane or maleic anhydride and ethylene–propylene random (EPR) copolymer modified with maleic anhydride. The thermal behavior, mechanical properties, and morphology of the blends were investigated. Thermal analysis showed that the polyamide crystallization temperatures shifted downward with all compatibilizers, whereas its melting behavior did not change. On the other hand, polypropylene crystallization temperatures shifted upward in all cases, except for blends containing EPR modified with maleic anhydride. Tensile strength and elongation at break increased for blends compatibilized with modified PP. Blends containing up to 7% of EPR modified with maleic anhydride did not show good yield stresses. The morphology of the blends showed a finer dispersion of the polyamide minor phase in the PP matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2492–2498, 2003     

Influence of silane‐coupling agents on the performance of morphological,mechanical, thermal,electrical, and rheological properties of polycarbonate/fly ash composites

Fly ash, waste product of thermal power station, generated in huge quantities has been posing problems of its disposal. As such, it contains a variety of inorganic oxide and is available in finely powder form. Attempts have been made for its utilization, as filler in engineering plastic. The fly ash (FA) fillers reinforced polycarbonate (PC) composites were fabricated using a economically and environmentally viable method of melt extrusion and compression molding technique. The FA surface was chemically modified using vinyltrimethoxysilane and 3–Aminopropyltriethoxysilane. The feasibility of using treated FA/PC composites was examined in terms of scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and rheological behavior. The morphology shows a good dispersion and strong interfacial interaction between PC and modified FA than the unmodified counterpart. Mechanical investigation manifested that modified FAs have strengthening effect (increase in tensile and flexural strength) on the mechanical performance of PC composites. Rheological behavior of PC/FA composites was characterized by parallel plate rheometer system. Addition of treated FA imparted dimensional and thermal stability, which has been observed in scanning electron micrographs and in thermogravimetric analysis plot. The increase of thermal stability has been explained based on increased mechanical interlocking of PC chains inside the structure of FA. This study shows that surface modification of FA is one of the key factors influencing the mechanical and thermal properties of PC/FA composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Chemically modified oil palm ash‐filled natural rubber composites and its properties

Chemically modified Oil Palm Ash (OPA)‐filled natural rubber composites were prepared by modifying the functional group of OPA with cetyltrimethylammonium bromide (CTAB) prior to compounding by using laboratory conventional laboratory‐sized two‐roll mills. The functional groups of CTAB‐modified OPA were analyzed by using Fourier Transform Infrared (FTIR) and compared with those of non‐modified ones. The CTAB‐modified OPA‐filled NR composites showed shorter scorch time and cure time as compared to those of non‐modified OPA, which was attributed to the new functional groups occurred. The tensile test results showed that the OPA‐filled NR composites with CTAB modification exhibit improvement in tensile strength, tensile modulus, and hardness but lower elongation at break as compared to nonmodified ones. The tensile fractured surface of modified OPA filled NR composites revealed the well embedded and better distribution of CTAB‐modified OPA in NR matrix. The toluene uptake was also found to be lower for the modified OPA‐filled NR composites and showed better rubber–filler interaction; it further showed that surface modification with CTAB could compatibilize the OPA particles and NR matrix. POLYM. COMPOS., 35:691–697, 2014. © 2013 Society of Plastics Engineers     

Improved electromechanical response in acrylic rubber by different carbon‐based fillers

Dielectric elastomers are materials often utilized for the fabrication of electroactive actuators. Acrylic rubber (ACM) is very widely used in dielectric elastomer actuators (DEAs). However, its overall good performance is limited by the high operating electric field required. In the present work, we compare the effect of different types of conventionally used carbon black (CB) as well as other carbon‐based fillers on the dielectric and actuation properties of ACM in order to show that performance of DEAs can be improved by the development of ACM composites. Indeed, addition of CB, carbon nanotubes (CNTs), and synthetic graphite leads to an increase in the relative dielectric permittivity of elastomeric material. Moreover, incorporation of nanodiamonds results in reduction of dielectric losses. Finally, actuation stress is remarkably improved by CNTs and different grades of CB. POLYM. ENG. SCI., 58:395–404, 2018. © 2017 Society of Plastics Engineers