Silane Modification of Carbon Nanotubes and Preparation of Silane Cross‐Linked LLDPE/MWCNT Nanocomposites

The objective of this study is to investigate the effects of carbon nanotube (CNT) content, surface modification, and silane cross‐linking on mechanical and electrical properties of linear low‐density polyethylene/multiwall CNT nanocomposites. CNTs were functionalized by vinyltriethoxysilane to incorporate the ─O─C2H5 functional groups and were melt‐blended with polyethylene. Silane‐grafted polyethylene was then moisture cross‐linked. Silanization of CNT was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and EDX analysis. Hot‐set test results showed that silane cross‐linking of polyethylene and incorporation of modified CNTs into polyethylene led to an increase in cross‐linking density and the number of entanglements resulting in a decrease in elongation. It was found that the addition of pristine multiwall carbon nanotubes (MWCNTs) and functionalized MWCNTs does not affect silane cross‐linking density. Silane modification resulted in a stronger adhesion of the silane cross‐linked LLDPE to silanized MWCNTs according to scanning electron microscopy micrographs. Additionally, the electrical tests revealed that the silane modification of CNTs results in an improvement in electrical properties of nanocomposites, while silane cross‐linking will not have an effect on electrical properties. Rheological properties of MWCNT/LLDPE nanocomposites have been studied thoroughly and have been discussed in this study. Moreover, according to TGA test results, modification of the MWCNTs led to a better dispersion of them in the LLDPE matrix and consequently resulted in an improvement in thermal properties of the nanocomposites. Crystallinity and melting properties of the nanocomposites have been evaluated in detail using DSC analysis. J. VINYL ADDIT. TECHNOL., 26:113–126, 2020. © 2019 Society of Plastics Engineers     

Comparative role of Interface in reinforcing mechanisms of Nano silica modified by Silanes and liquid rubber in SBR composites

The objective of the present study is to discuss the role of silica-rubber interfacial interactions on vulcanization kinetics, morphology, mechanical and viscoelastic behavior of silica filled styrene butadiene rubber (SBR) composites. Three types of modifiers, namely mono- and bi-functional silanes as well as hydroxyl-terminated poly butadiene (HTPB) liquid rubber were grafted to silica surface, and composites prepared by these fillers were characterized. Results showed that modified silica, especially grafted by bi-functional silane and liquid rubber, accelerated vulcanization reactions, while pristine silica slowed down vulcanization kinetics of SBR. Morphological studies indicated that all modifications improved dispersion of silica, but HTPB-grafted silica was dispersed to a greater extent in SBR. The observed differences in mechanical and dynamic-mechanical properties of vulcanizates were correlated to the significant differences in silica-rubber and silica-silica interactions. Type of interfacial interactions, i.e. rigid covalent bonds in the bi-functional silane, flexible polymeric bonds in the liquid rubber, and weak energetic bonds in the mono-functional silane, could explain the observed differences. Although all modifications reduced filler networking, rigid covalent bonding by bi-functional silane significantly improved mechanical properties and stabilized the filler network. The mono-functional silane lacks these mechanisms. The soft and flexible interphase of HTPB could create bonds and transfer stresses between the rubber matrix and silica to some extent, however it could not improve the mechanical properties and reduce the Payne effect as much as the bi-functional silane did.     

Mechanical,thermal and electrical properties of multi‐walled carbon nanotube/aluminium nitride/polyetherimide nanocomposites

A series of polyimide‐based nanocomposites containing polyimide‐grafted multi‐walled carbon nanotubes (PI‐g MWCNTs) and silane‐modified ceramic (aluminium nitride (AlN)) were prepared. The mechanical, thermal and electrical properties of hybrid PI‐g MWCNT/AlN/polyetherimide nanocomposites were investigated. After polyimide grafting modification, the PI‐g MWCNTs showed good dispersion and wettability in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The utilization of the hybrid filler was found to be effective in increasing the thermal conductivity of the composites due to the enhanced connectivity due to the high‐aspect‐ratio MWCNT filler. The use of spherical AlN filler and PI‐g MWCNT filler resulted in composite materials with enhanced thermal conductivity and low coefficient of thermal expansion. Results indicated that the hybrid PI‐g MWCNT and AlN fillers incorporated into the polyetherimide matrix enhanced significantly the thermal stability, thermal conductivity and mechanical properties of the matrix. Copyright © 2012 Society of Chemical Industry     

Effect of fillers on thermal and mechanical properties of polyurethane elastomer

The effects of five different types of fillers on the thermal and mechanical properties of hydroxyl-terminated polybutadiene-based polyurethane elastomers were explored to develop a filled polyurethane elastomeric liner for rocket motors with hydroxyl-terminated polybutadiene-based composite propellants. Two type of carbon black, silica, aluminum oxide, and zirconium(III) oxide were used as filler. Based on the improvement in the tensile properties and the erosion resistance achieved in the first part of the study, an ISAF-type carbon black was selected to be used as the main filler in combination with an additional filler. The second part involves the investigation of polyurethane elastomers containing a second filler in various amounts in addition to the ISAF-type carbon black used as the main filler. In addition to the thermal and mechanical properties, the processability of the uncured polyurethane mixtures were also explored by measuring the viscosity in this second part of the study. The studied fillers do not considerbly change the thermal degradation temperatures and the thermal conductivity of the polyurethane elastomers with a filler content up to 16 wt %. The best improvement in the erosion resistance and tensile strength of the polyurethane elastomers with additional fillers is also achieved when filled with the ISAF-type carbon black, whereas the use of zirconium(III) oxide as additional filler provides almost no improvement in these properties. Viscosity of the uncured polyurethane mixtures increases with the increasing filler content and with the decreasing particle size of the filler. Aluminum oxide-filled elastomers seem to be the most suitable compositions having sufficiently high thermal and mechanical properties, together with the processability of uncured mixtures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1057–1065, 1998     

Thermal and fire retardancy studies of clay‐modified unsaturated polyester/glass fiber composites

The aim of this study was to investigate the effect of new, cation‐exchanged, and silane modified montmorillonite nanoclays fillers on thermal, mechanical and flammability characteristics of polyester/glass fiber composites in comparison with composites prepared with calcium carbonate filler. The coefficient of thermal expansion showed reduced values for silane‐modified samples. All the composites decomposed at lower temperatures in air and their degradation behavior differed from those exposed to nitrogen. The glass fibers acted as a physical barrier before combustion and the catalytic effect of the clay was less pronounced for silane‐modified samples. The peak of heat release and linear burning rate for the silane‐modified Cloisite 30B sample was reduced. However, the limiting oxygen index did not show significant changes. In general, consequent to clay addition, these composites showed improved fire performance, shorter fire duration and slower fire growth and maintained better mechanical properties than those with calcium carbonate filler. POLYM. COMPOS., 38:2743–2752, 2017. © 2015 Society of Plastics Engineers     

Mechanical reinforcement of polyethylene using n‐alkyl group‐functionalized multiwalled carbon nanotubes: Effect of alkyl group carbon chain length and density

Polyethylene (PE) is one of the most produced synthetic resins in the world. Functionalized multiwalled carbon nanotube (MWCNT) is a potential nanoscale filler to realize the next generation strong and multifunctional PE composites. We demonstrate that MWCNTs grafted with short n‐alkyl groups are effective nanofillers for mechanical reinforcement of PE composites. At 1 wt% filler loading, the yield stress and Young's modulus improve significantly up to 54 and 63% compared with neat PE, respectively. Among ductile properties, tensile strength increases up to 30%; ultimate strain is preserved; and toughness increases up to 33%. More important, we show that short n‐alkyl groups can be grafted on MWCNTs much easier than long chain polymers. Further, we find that alkyl groups of C14–C18 chains have the optimum length for reinforcement. The optimum density of grafted alkyl groups is around 0.390–0.423 μmol/mg when the C14 alkyl groups are used. Overall, the results manifest that MWCNTs grafted with n‐alkyl groups with suitable length and density are efficient nanoscale fillers for high‐performance PE composites. POLYM. ENG. SCI., 54:336–344, 2014. © 2013 Society of Plastics Engineers     

High electrical conductivity of nylon 6 composites obtained with hybrid multiwalled carbon nanotube/carbon fiber fillers

The synergetic effect of multiwalled carbon nanotubes (MWNTs) and carbon fibers (CFs) in enhancing the electrical conductivity of nylon 6 (PA6) composites was investigated. To improve the compatibility between the fillers and the PA6 resin, we grafted γ‐aminopropyltriethoxy silane (KH‐550) onto the MWNTs and CFs after carboxyl groups were generated on their surface by chemical oxidation with nitric acid. Fourier transform infrared spectroscopy and thermogravimetric analysis proved that the KH‐550 molecules were successfully grafted onto the surface of the MWNTs and CFs. Scanning electron microscopy and optical microscopy showed that the obtained modified fillers reduced the aggregation of fillers and resulted in better dispersion and interfacial compatibility. We found that the electrical percolation threshold of the MWNT/PA6 and CF/PA6 composites occurred when the volume fraction of the fillers were 4 and 5%, respectively. The MWNT/CF hybrid‐filler system exhibited a remarkable synergetic effect on the electrically conductive networks. The MWNT/7% CF hybrid‐filler system appeared to show a second percolation when the MWNT volume fraction was above 4% and a volume resistivity reduction of two orders of magnitude compared with the MWNT/PA6 system. The mechanical properties of different types of PA6 composites with variation in the filler volume content were also studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40923.     

Structure development in thermoset recyclate‐filled polypropylene composites

Polypropylene containing comminuted fiber reinforced thermoset recyclate has been shown to exhibit enhanced mechanical properties relative to particulate‐filled materials. Optimum mechanical performance in these recyclate‐filled materials is achieved in compositions made from rubber‐modified polypropylene containing maleic anhydride‐modified PP in conjuction with silane coupling agent. Although matrix crosslinking was found to enhance properties in both filled and unfilled systems, composite properties are dominated by the development of strong interfacial bonding between polypropylene and recyclate reinforcement. A mechanism for the formation of interfacial bonding is proposed involving reaction between maleic anhydride functionalized PP, formation of trisilanol groups and their subsequent condensation with hydroxyl groups on the recyclate surfaces, together with molecular entanglement and co‐crystallization of the grafted and ungrafted polypropylene molecules. Furthermore, in the absence of treatment there is evidence that the elastomer particles encapsulate the filler particles. However, this effect is strongly hindered when functionalized‐PP is added, either in isolation or in combination with the silane co‐treatment. The crystalline nucleation of PP by thermoset recyclate and treatment is also considered. The treatment system investigated was found to promote interfacial bonding to both the polyester (DMC) and woven glassreinforced phenolic recyclates investigated, suggesting it may be suitable for treating mixed composite scrap.     

Properties and performance of a simulated consumer polymer waste—coal combustion byproduct composite material

A UK sourced fly ash (coded UKFA) was introduced into polypropylene (PP)/polyethylene (PE) based composites at different PP/PE ratios to investigate its effect on the physical and mechanical properties of the material. Composites containing 65% wt. fly ash modified with commercial peroxide (DCP) and commercial coupling agent (C800) were prepared via batch mixing and compression moulding. The usage of DCP led to the formation of cross‐linked PE, which was responsible for highly viscous composites. The newly formed cross‐linked PE, together with chain scission of PP, would promote phase separation. Mechanically less stiff materials were produced, especially at high PE levels, because of the larger rubbery interfacial region, despite the good matrix–filler adhesion increasing the strength balance. POLYM. ENG. SCI., 54:1239–1247, 2014. © 2013 Society of Plastics Engineers     

Mechanical properties of recycled polyethylene ecocomposites filled with natural organic fillers

The use of natural organic fillers in addition to postconsumer recycled polymers is getting a growing interest during the last years; this is due to many advantages they can provide in terms of cost, aesthetic properties, environmental impact. In this work, several types of wood flour (differing each other with regard to production source and particle size) were added to a recycled polyethylene coming from films for greenhouses and the effects of filler type, content, and size were investigated. Investigation was then focused on the improvement of mechanical properties, through the addition of polar copolymers (ethylene‐co‐acrylic acid, ethylene‐vinyl acetate) and a maleic anhydride‐grafted‐grafted polyethylene (Licocene® PE MA 4351 TP), in order to try to overcome the poor adhesion between polar filler particles and nonpolar polymer chains. Investigation was also based on SEM micrographs. An overall positive influence of these additives was observed. Polym. Eng. Sci. 46:1131–1139, 2006. © 2006 Society of Plastics Engineers.     

The influence of the dispersed phase on the morphology,mechanical and thermal properties of PLA/PE‐LD and PLA/PE‐HD polymer blends and their nanocomposites with TiO2 and CaCO3

This research investigated the impact of different processing temperature (extrusion at 160°C and 180°C) and the influence of the TiO₂ and CaCO₃ fillers on morphology, mechanical, and thermal properties of polylactide (PLA) blended with low‐density polyethylene (PE‐LD) and high‐density polyethylene (PE‐HD) in 90/10 weight ratio. The impact of the particle size of the filler was also examined with the three types of TiO₂ filler. It has been shown that the different processing temperature has no significant impact on the morphology, mechanical, and thermal properties of PLA/PE‐LD 90/10 and PLA/PE‐HD 90/10 polymer blends. It has also been shown that better phase interaction is not the crucial factor for the improvement of the mechanical properties but the domain size distribution of the dispersed phase within the matrix and the dispersion of the filler are. Samples with a narrow size distribution of the dispersed phase domain (5 to 10 μm) with the higher portion of larger domains that are uniformly distributed within the polymer matrix showed best mechanical properties. POLYM. ENG. SCI., 59:1395–1408 2019. © 2019 Society of Plastics Engineers     

Effects of silane coupling agent and maleic anhydride‐grafted polypropylene on the morphology and viscoelastic properties of polypropylene–mica composites

In this study, morphology, and dynamic and mechanical properties of polypropylene–mica (PP–Mica) composites were investigated. To enhance the adhesion between PP and mica, maleic anhydride‐grafted PP (MAPP) and treated mica with silane coupling agent were used. MAPP (as a compatibilizer) and silane coupling agent (as a filler surface modifier) caused an interfacial bonding in the mica filled polypropylene composites. The effect of mica content, MAPP, and treated mica with silane coupling agent on the morphological properties were investigated by Scanning Electron Microscopy (SEM). The results showed that with increasing MAPP or silane coupling agent, dispersion of filler and adhesion between PP and filler were improved. Mechanical data showed that with increasing MAPP and mica treated with silane coupling agent, tensile modulus and flextural strength of composites were enhanced. Dynamic rheological behavior of composites was also investigated within the domain of linear viscoelasticity. The rheological observations indicated that the complex viscosity, storage and loss moduli increased, and tan δ decreased with increasing mica content. POLYM. COMPOS. 27:491–496, 2006. © 2006 Society of Plastics Engineers.     

Effects of silane on the properties of wood‐plastic composites with polyethylene‐polypropylene blends as matrices

The influence of 3‐(trimethoxysilyl)propyl methacrylate and benzoyl peroxide on gel content, crystallinity, and mechanical performance of unfilled PP‐PE blends, and their composites with wood was investigated. All materials were compounded in a twin screw extruder and then injection molded. Specimens were then exposed to high‐humidity and elevated temperature in a humidity chamber to cross‐link any unhydrolyzed silane. Adding wood to the PE‐PP blends, increased premature cross‐linking but also increased gel contents. However, the gel contents of the composites were still low. The PP component did not appear to cross‐link well and our gels were almost entirely HDPE. Fourier Transfer Infrared (FTIR) spectra provided additional evidence that TMSPM is grafted and cross‐linked in unfilled PE‐PP blends. Unfortunately, the spectra of wood composites proved difficult to interpret because of the complexity and overlap of the FTIR spectra of the wood. The HDPE component annealed when exposed to high‐humidity and elevated temperature, although less so in samples with high‐gel contents, presumably because of the decreased mobility. Annealing influenced mechanical performance, especially increasing moduli. Adding peroxide and silane appeared to improve adhesion between the wood flour and matrix in the composites but had little effect on energy absorbed during high‐speed puncture tests. Published 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of Nano‐SiC on Silane Grafting and Curing of Polyolefin Elastomer: Mixing Order,Physical, and Mechanical Properties

The objective of this article was preparation of curable silane‐grafted poly(ethylene‐1‐butene) nanocomposite. The poly(ethylene‐1‐butene) was a polyolefin elastomer with random high comonomer content. Two preparation methods were investigated. The method of preparing nanocomposites significantly affected the mechanical properties of the resulted nanocomposites. So that, with the same formulation and different preparation methods, silane grafting with the first was 94% (PVDS3), while with the second was 33% (PS3VD). It was shown that the tensile strength of the cured nanocomposite prepared with the method 1 (PVDS3) increased four times higher than the pure resin. The effects of different factors such as the amount of silane and also the amount of silicon carbide on the physical, mechanical, and thermal properties of the cured and uncured nanocomposites were investigated. The rate of curing was depended on the silicon carbide concentration and 5 phr (part per hundred resin), and nano‐SiC was a concentration where the tensile properties were optimum. Thermal stability and the impermeability of the cured samples improved in the presence of nano‐silicon carbide. J. VINYL ADDIT. TECHNOL., 26:244–252, 2020. © 2019 Society of Plastics Engineers     

Effects of silicone oil and polymeric modifiers on the mechanical properties of highly filled LLDPE

The effects of coupling agents, silicone oil, and three types of polymeric modifiers on the mechanical properties of linear low density polyethylene (LLDPE) composites highly filled with aluminium hydroxide [Al(OH)₃] were studied. Polymeric modifiers that contain polar groups, such as silane‐grafted polyethylene (Si‐g‐PE) and acrylic‐acid‐grafted ethylene‐vinyl acetate copolymer (AA‐g‐EVA), improve the mechanical properties dramatically, while nonpolar modifiers improve them to some extent. When Al(OH)₃ was treated using a titanate coupling agent, the silicone oil increased the impact strength and elongation at break of the LLDPE/Al(OH)₃ composites. Introduction of a polymeric modifier containing polar groups destroys the beneficial effects of silicone oil on film mechanical properties, while the introduction of a nonpolar elastomeric polymeric modifier retains the high impact strength and elongation at break. SEM analyses provide the indirect evidence of the encapsulation of silicone oil around the filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 121–128, 2002     

The influence of structural order of anthracite fillers on the curing behavior,morphology, and dynamic mechanical thermal properties of epoxy composites

This article concerns the study of polymer composites with anthracite fillers of various structural order. Raw Svierdlovski anthracite of turbostratic structure and the anthracite thermally treated at 2,000°C of graphite‐like structure were used as fillers of low‐molecular‐weight diglycidyl ether of bisphenol A cross‐linked with aliphatic amine. Two anthracites of extremely different structures were compared to natural graphite that is composed of well‐ordered graphene sheets. Systematic studies of the influence of the structure of anthracite filler on the curing behavior, morphology, dynamic mechanical thermal properties, and thermal stability of epoxy composite were performed. It was found that the structure of anthracite filler affects the cross‐linking reactions of the epoxy matrix as well as the morphology of the composites and their viscoelastic properties. Raw anthracite added to epoxy matrix had a visible effect on the activation energy and differential scanning calorimeter parameters of the curing process, in contrast to the epoxy matrix modified with anthracite heated at 2,000°C. On the contrary, the effect of anthracite on dynamic mechanical behavior of composites is more evident when the anthracite prepared at 2,000°C was used as a filler. POLYM. COMPOS., 36:336–347, 2015. © 2014 Society of Plastics Engineers     

Green composites of organic materials and recycled post‐consumer polyethylene

Addition of organic fillers to post‐consumer recycled plastics can give rise to several advantages. First of all, the cost of these fillers is usually very low, the organic fillers are biodegradable contributing to an improved environmental impact and, last but not least, some mechanical and thermomechanical properties can be enhanced. Organic fillers are not widely used in the plastic industry although their use is increasing. Bad dispersion into the polymer matrix at high‐level content and poor adhesion with the matrix are the more important obstacles to this approach. In this work various organic fillers have been used with a post‐consumer plastic material originating from films for greenhouses. The properties of these green composites have been compared with those of materials filled with a conventional inorganic filler. The organic fillers cause slightly worse processability, due to an increase of viscosity, an enhancement of the rigidity and of the thermomechanical resistance similar to that measured for the inorganic filler, while a reduction of the impact strength is observed. Copyright © 2004 Society of Chemical Industry     

Mechanical properties and morphology of nylon‐6 hybrid composites

In this investigation, the influence of filler type and filler content on the mechanical properties of nylon‐6 is investigated. The mineral fillers were selected on the basis of their shape and size: flake‐like kaolin and talc, spherical glass beads or fibrous wollastonite. These fillers were added to nylon‐6 individually or in mixed combinations. They were added at different percentages varying between 10 and 30% w/w. Samples of the composites were prepared by the injection moulding process. Uniaxial tensile, Izod impact and flexural tests were carried out. Tensile strength, elongation at break, modulus of elasticity and impact energy were obtained and compared. In case of single fillers the results showed that the tensile strength, modulus of elasticity and their flexural values for nylon‐6 composite improve with the increase in filler content while mixed compounds showed no significant changes above 15% + 15% w/w filler. However, for single and mixed filler up to 10% w/w, the impact strength and maximum elongation at break showed significant decrease. In general, the maximum improvement in mechanical the addition of 10–15% w/w filler. Copyright © 2003 Society of Chemical Industry     

Effect of oleyl amine on SBR compounds filled with silane modified silica

The effect of oleyl amine on processing and physical properties of SBR compounds filled with silane–silica particles has been evaluated. Two different types of silane molecules have been used as coupling agents to minimize the silica–silica interactions and reduce the formation of secondary structures of silica, in addition with an increment in the filler–rubber interactions. Significant differences between those compounds have been found according with the silane structure. However, in both cases, the dynamic, rheological, and mechanical properties of the filled rubber compounds were improved after the incorporation of oleyl amine molecules. This fact could be related with the capacity of the amine molecules to interact with the free silanol groups of silane‐modified silica forming an amine‐modified silica complex, which reduces the hydrophilic nature of the silica surface. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1806–1814, 2007     

Preparation of nano‐zinc oxide/EPDM composites with both good thermal conductivity and mechanical properties

In this article, nano‐zinc oxide (ZnO) filled ethylene propylene diene monomer (EPDM) composites are prepared, and the mechanical (static and dynamic) properties and thermal conductivity are investigated respectively, which are further compared with the traditional reinforcing fillers, such as carbon black and nano‐silica. Furthermore, influence of in‐situ modification (mixing operation assisted by silane at high temperature for a certain time) with the silane‐coupling agent Bis‐(3‐thiethoxy silylpropyl)‐tetrasufide (Si69) on the nano‐ZnO filled composites is as well investigated. The results indicate that this novel reinforcing filler nano‐ZnO can not only perform well in reinforcing EPDM but can also improve the thermal conductivity significantly. In‐situ modification with Si69 can enhance the interfacial interaction between nano‐ZnO particles and rubber matrix remarkably, and therefore contribute to the better dispersion of filler. As a result, the mechanical properties and the dynamic heat build‐up of the nano‐ZnO filled composites are improved obviously by in‐situ modification, without influencing the thermal conductivity. In comparison with traditioanl reinforcing fillers, in‐situ modified nano‐ZnO filled composites exhibit the excellent performance in both mechanical (static and dynamic) properties and better thermal conductivity. In general, our work indicates that nano‐ZnO, as the novel thermal conductive reinforcing filler, is suitable to prepare elastomer products serving in dynamic conditions, with the longer expected service life. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011