Functional thiol ionic liquids as novel interfacial modifiers in SBR/HNTs composites

Eco-friendly flame-retardant bamboo fiber/polypropylene composite based on the immobilization of halloysite nanotubes by tannic acid-Fe3+ complex

Bamboo fibers (BF), as an important sustainable natural material, are becoming a hot alternative to synthetic fibers for the reinforcement of polypropylene (PP)-based composites. However, the weak interfacial compatibility between BF and PP as matrix and their inherent flammability limit the practical application of BF/PP composites (BPC). Here, a fire-safe BPC was fabricated by constructing flame-retardant interfacial layers containing tannic acid (TA)-Fe3+ complex and halloysite nanotubes (HNTs) on the fiber matrix followed by a hot-pressing process. The results showed that the interfacial chelating of TA with Fe3+ improved the dispersion of HNTs on the fibers and the interfacial interactions within the fiber matrix, resulting in the as-fabricated composite with significantly improved mechanical properties and water resistance. In addition, the flame-retardant composite exhibited higher thermal stability and enhanced residual char content. Moreover, the composite possessed significant flame-retardant performances with a reduction of 23.75 % in the total heat release and 32.44 % in the total smoke production, respectively, owing to the flame retarding in gaseous phase and condensed phase of TA-Fe3+@HNTs layers. This work offers a green and eco-friendly strategy to address the inherent problems of BPC material in terms of fire safety and interfacial compatibility, thus broadening their applications in the automotive interior and construction industries.

Anti-friction gold-based stretchable electronics enabled by interfacial diffusion-induced cohesion

Stretchable electronics that prevalently adopt chemically inert metals as sensing layers and interconnect wires have enabled high-fidelity signal acquisition for on-skin applications. However, the weak interfacial interaction between inert metals and elastomers limit the tolerance of the device to external friction interferences. Here, we report an interfacial diffusion-induced cohesion strategy that utilizes hydrophilic polyurethane to wet gold (Au) grains and render them wrapped by strong hydrogen bonding, resulting in a high interfacial binding strength of 1017.6 N/m. By further constructing a nanoscale rough configuration of the polyurethane (RPU), the binding strength of Au-RPU device increases to 1243.4 N/m, which is 100 and 4 times higher than that of conventional polydimethylsiloxane and styrene-ethylene-butylene-styrene-based devices, respectively. The stretchable Au-RPU device can remain good electrical conductivity after 1022 frictions at 130 kPa pressure, and reliably record high-fidelity electrophysiological signals. Furthermore, an anti-friction pressure sensor array is constructed based on Au-RPU interconnect wires, demonstrating a superior mechanical durability for concentrated large pressure acquisition. This chemical modification-free approach of interfacial strengthening for chemically inert metal-based stretchable electronics is promising for three-dimensional integration and on-chip interconnection.

Surface Activated Pyrolytic Carbon Black: A Dual Functional Sustainable Filler for Natural Rubber Composites

The significant rise in end-of-life tires (ELTs) globally poses immediate environmental and human health risks. Therefore, to promote ELTs recycling and to reduce tire industry carbon emissions, herein we present a facile approach for fine-tuning the interfacial interactions between pyrolytic carbon black (P-CB) obtained from ELTs and natural rubber (NR) matrix using phosphonium-based ionic liquid (PIL). The reinforcing effect of PIL-activated P-CB was studied by replacing the furnace-grade carbon black (N330-CB) with varying PIL and P-CB loadings. Adding PIL improved the filler dispersion and the cross-linking kinetics with a substantially reduced zinc oxide (ZnO) loading. Considering the cross-linking and viscoelastic properties, it was concluded that the composite, P-CB/N330-CB-PIL (1.5)+ZnO (1) with half substitution of N330-CB with P-CB synergistically works with 1.5 phr PIL and 1 phr of ZnO resulting in improved dynamic-mechanical properties with a minimal loss tangent value at 60 °C (tanδ=0.0689) and improved glass transition temperature (Tg =-38 °C) compared to control composite. The significant drop (~29 % lower) in tanδ could reduce fuel consumption and related CO2 emissions. We envisage that this strategy opens an essential avenue for "Green Tire Technology" towards the substantial pollution abatement from ELTs and reduces the toxic ZnO.

Thiyl radical induced cis/trans isomerism in double bond containing elastomers

This report presents an evaluation of thiyl radical-induced cis/trans isomerism in double bond-containing elastomers, such as natural, polychloroprene, and polybutadiene rubbers. The study aims to extensively investigate structural changes in polymers after functionalisation using thiol-ene chemistry, a useful click reaction for modifying polymers and developing materials with new functionalities. The paper reports on the use of different thiols, and cis/trans isomerism was detected through 1H NMR analysis, even at very low alkene/thiol mole ratios. The study finds that the configurational arrangements between non-functionalised elastomer units and thiolated units followed a trans-functionalised-cis units arrangement up to an alkene/thiol mole feed ratio of 0.3, while from 0.4 onward, a combination of trans-functionalised-cis and cis-functionalised-trans configurations are found. Additionally, it is observed that by increasing the level of functionalisation, the glass transition temperature of the resulting modified elastomer also increases. Overall, this study provides valuable insights into the effects of thiol-ene chemistry on the structure and properties of elastomers and could have important implications for the development of new materials with enhanced functionality.

Phosphonium Ionic Liquid-Activated Sulfur Vulcanization: A Way Forward to Reduce Zinc Oxide Levels in Industrial Rubber Formulations

Extensive use of zinc oxide and accelerators such as diphenyl guanidine (DPG) in the vulcanization of rubber composites entail potential environmental risks. These are pervasive contaminants of roadway runoff originating from tire wear particles (TWPs). Herein, the effect of phosphonium ionic liquids (PILs) in styrene-butadiene rubber compounds was demonstrated with reduced ZnO loading and no DPG to minimize the environmental footprint of the vulcanization process. The structure and chemistry of PILs were found to be the influencing parameters impelling the cross-linking kinetics, enabling shorter induction times. The generation of active Zn²⁺ sites by PILs was examined through FTIR spectroscopy, calorimetry, and molecular dynamics simulations. From a tire application perspective, the PILs not only enhanced the cure kinetics but also improved the dynamic-mechanical behavior of the rubber composites. Consequently, the harm caused by TWPs to the atmosphere, fuel intake, and CO₂ emissions was minimal, thereby confirming the potential use of PILs in the tire industry.

Halloysite Nanotube as a Functional Material for Active Food Packaging Application: A Review

Halloysite nanotubes (HNTs) are naturally occurring nanomaterials with a tubular shape and high aspect ratio, a promising functional additive for active food packaging applications. HNTs have been shown to possess unique properties such as high surface area, thermal stability, and biocompatibility, making them attractive for active food packaging materials. This review summarizes recent research on the use of HNTs as functional additives in active food packaging applications, including antimicrobial packaging, ethylene scavenging packaging, moisture, and gas barrier packaging. The potential benefits and challenges associated with the incorporation of HNTs into food packaging materials are discussed. The various modification methods, such as the physical, chemical, biological, and electrostatic methods, along with their impact on the properties of HNTs, are discussed. The advantages and challenges associated with each modification approach are also evaluated. Overall, the modification of HNTs has opened new possibilities for the development of advanced packaging materials with improved performance for various functional food packaging materials with enhanced properties and extended shelf life.

Multifunctional Applications of Ionic Liquids in Polymer Materials: A Brief Review

As a new generation of green media and functional materials, ionic liquids (ILs) have been extensively investigated in scientific and industrial communities, which have found numerous ap-plications in polymeric materials. On the one hand, much of the research has determined that ILs can be applied to modify polymers which use nanofillers such as carbon black, silica, graphene oxide, multi-walled carbon nanotubes, etc., toward the fabrication of high-performance polymer composites. On the other hand, ILs were extensively reported to be utilized to fabricate polymeric materials with improved thermal stability, thermal and electrical conductivity, etc. Despite substantial progress in these areas, summary and discussion of state-of-the-art functionalities and underlying mechanisms of ILs are still inadequate. In this review, a comprehensive introduction of various fillers modified by ILs precedes a systematic summary of the multifunctional applications of ILs in polymeric materials, emphasizing the effect on vulcanization, thermal stability, electrical and thermal conductivity, selective permeability, electromagnetic shielding, piezoresistive sensitivity and electrochemical activity. Overall, this review in this area is intended to provide a fundamental understanding of ILs within a polymer context based on advantages and disadvantages, to help researchers expand ideas on the promising applications of ILs in polymer fabrication with enormous potential.

Crystalline chalcogenidometalate-based compounds from uncommon reaction media

Chalcogenides are one of the most versatile inorganic materials families, further subdivided into a large variety of specific groups of compounds, ranging from neat binary or multinary solids and nanoparticles of the same formal compositions, both in crystalline or non-crystalline form, to complicated open-framework structures and cluster compounds, also including organ(ometall)ic derivates of the latter. The large variety regarding both the compositions and the structures is associated with an enormous variety of properties, ranging from simple or high-tech pigments through a multitude of opto-electronic devices and electrolytes to materials for ion separation or high-sophisticated catalysts. Naturally, this also goes hand in hand with a corrosponding breadth of synthesis strategies. Traditionally, chalcogenides have been accessed via high-temperature methods, which continuously have been replaced by lower-temperature approaches for economical and ecological reasons. Moreover, more recent methods also showed that new types of chalcogenide materials can be obtained under such milder conditions that are not accessible via traditional routes. To shed light onto one of the numerous families of chalcogenides, this feature article summarizes current achievements in the generation of multinary chalcogenidometallate-based clusters and networks via non-classical routes, using ionic liquids, surfactants, or hydrazine as reaction media at moderately elevated termperature.

Bromide and Chloride Ionic Liquids Applied to Enhance the Vulcanization and Performance of Natural Rubber Biocomposites Filled with Nanosized Silica

In this study, the possibility of using ionic liquids (ILs) as auxiliary substances improving the vulcanization and physicochemical properties of natural rubber (NR) biocomposites filled with nanosized silica was investigated. Hence, the influence of ILs with bromide and chloride anions and various cations, i.e., alkylimidazolium, alkylpyrrolidinium and alkylpiperidinium cation, on the curing characteristics and crosslink density of NR compounds was determined. Furthermore, the effect of nanosized silica and ILs on the functional properties of the obtained vulcanizates, including mechanical properties under static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging, were explored. Applying nanosized silica improved the processing safety of NR compounds but significantly increased the optimal vulcanization time compared to the unfilled rubber. ILs significantly improved the cure characteristics of NR compounds by increasing the rate of vulcanization and the crosslink density of NR biocomposites. Consequently, the tensile strength and hardness of the vulcanizates significantly increased compared to that without ILs. Moreover, the use of nanosized silica and ILs had a favorable impact on the thermal stability of the vulcanizates and their resistance to prolonged thermo-oxidation.

Enzymatic and Chemical Approaches for Post-Polymerization Modifications of Diene Rubbers: Current state and Perspectives

Diene rubbers are polymeric materials which present elastic properties and have double bonds in the macromolecular backbone after the polymerization process. Post-polymerization modifications of rubbers can be conducted by enzymatic or chemical methods. Enzymes are environmentally friendly catalysts and with the increasing demand for rubber waste management, biodegradation and biomodifications have become hot topics of research. Some rubbers are renewable materials and are a source of organic molecules, and biodegradation can be conducted to obtain either oligomers or monomers. On the other hand, chemical modifications of rubbers by click-chemistry are important strategies for the creation and combination of new materials. In a way to expand the scope of uses to other non-traditional applications, several and effective modifications can be conducted with diene rubbers. Two groups of efficient tools, enzymatic, and chemical modifications in diene rubbers, are summarized in this review. By analyzing stereochemical and reactivity aspects, the authors also point to some applications perspectives for biodegradation products and to rational modifications of diene rubbers by combining both methodologies.

Influence of the Silica Specific Surface Area and Ionic Liquids on the Curing Characteristics and Performance of Styrene-Butadiene Rubber Composites

In this work, we present the effect of silica’s specific surface area (180 m²·g⁻¹ and 380 m²·g⁻¹, respectively) on the crosslinking of styrene–butadiene rubber (SBR) composites, as well as their crosslink density and functional properties, such as thermal stability, damping behavior, resistance to thermo-oxidative aging, and tensile properties. Ionic liquids (ILs) with a bromide anion and different cations, i.e., 1-butyl-3-methylimidazolium (Bmi), 1-butyl-3-methylpyrrolidinium (Bmpyr), and 1-butyl-3-methylpiperidinium (Bmpip), were used to enhance the cure characteristics of SBR compounds and the functional properties of SBR vulcanizates. It was proven that apart from the silica’s specific surface area, the filler–polymer and filler–filler physical interactions have a significant impact on the vulcanization kinetics of silica-filled SBR composites. Additionally, the performed studies have shown that ILs positively affected the dispersion of silica’s particles and reduced their ability to form agglomerates in the elastomer matrix, which enhanced the functional properties of the SBR vulcanizates.

Study on the Use of CTAB-Treated Illite as an Alternative Filler for Natural Rubber

Fillers are indispensable for rubber composites. Carbon black as an efficient reinforcing filler is most widely used in the rubber industry. However, the utilization of nonrenewable feedstock, energy consumption, and footprint for making carbon black lead to the seeking of alternative substitutes for carbon black, which is of great significance. Here in this work, the possibility of illite, a most common mineral in sedimentary rocks, as an alternative filler for natural rubber (NR) is determined. It is found that pristine illite slows the curing rate and decreases the cross-linking density of NR, which results in the inferior performance of NR. This is associated with the weak filler-rubber interaction, which is a vital factor in deciding the performance of rubber composites. Therefore, illite has been modified using hexadecyl trimethyl ammonium bromide (CTAB), a commonly used cation surfactant, for improving the filler-rubber interaction. The thus obtained C-illite is confirmed to be efficient for (i) enhancing the illite-NR interaction, (ii) improving the dispersion of illite in the NR matrix, and (iii) accelerating the curing process of NR with increased cross-linking density. All of these lead to significantly improved mechanical properties and wear resistance of the C-illite/NR composites, e.g., a 71.88% increase of the modulus at 300% strain compared to the pure NR and a 23.79% reduction of the DIN abrasion volume compared to the NR filled with 40 phr pristine illite. This illustrates the high possibility of CTAB-modified illite with an optimal particle size as a promising alternative filler of carbon black for reinforcing rubbers.

Generic Method to Create Segregated Structures toward Robust, Flexible, Highly Conductive Elastomer Composites

Electrically and thermally conductive polymer composites are extensively used in our daily life. It is of great significance to fulfill the conductivity requirement while maintaining desirable mechanical performance. An efficient solution to achieve this goal is to construct segregated structures in polymer composites by confining fillers into the interstitial areas among polymer domains. Thus far, it still remains a challenge to create segregated structures in cross-linked polymeric networks. Herein, we report a facile methodology to construct segregated structures in sulfur-cured rubbers using an industrially accessible process toward robust, flexible, highly conductive elastomer composites. Specifically, natural rubber granules (NR-RGs) with reactive di- and polysulfides on the surface are fabricated and then mixed with NR gum, carbon nanotubes (CNTs), and curing additives, followed by compression molding to yield two-phase separate composites. In the composites, CNTs are selectively dispersed in the continuous NR phase due to the volume exclusion effect caused by the separate NR-RG phase, leading to overwhelming electrical conductivity compared to the counterparts with randomly dispersed CNTs. In addition, NR-RGs can serve as novel reinforcement for NR, imparting the composites with remarkably improved modulus and retained stretchability. The simultaneously improved electrical conductivity and mechanical properties are due to the strong interfacial adhesion between the NR matrix and NR-RGs, as the di- and polysulfides on the surface of NR-RGs can participate in the cross-linking reactions of NR gum and enable the establishment of covalent bonding across the interfaces. The universality of this approach in preparing segregated composites with a combination of high conductivities and robust mechanical properties is demonstrated using other diene rubbers as the matrix and boron nitride as the filler.

Influence of Fillers and Ionic Liquids on the Crosslinking and Performance of Natural Rubber Biocomposites

This work concerns the effect of fillers and ionic liquids on the cure characteristics of natural rubber (NR) compounds, as well as the mechanical and thermal properties of the vulcanizates. Three types of white filler were applied, such as cellulose, nanosized silica and hydrotalcite, to modify the performance of NR composites. Additionally, ionic liquids (ILs) with bromide anion and different cations, i.e., 1-butyl-3-methylimidazolium (Bmi) and 1-butyl-3-methylpyrrolidinium (Bmpyr), were used to improve the cure characteristics of NR compounds and functional properties of the vulcanizates. The type of filler and the structure of ILs were proved to affect the rheometric properties and cure characteristics of NR compounds as well as the performance of the NR vulcanizates. Owing to the adsorption of curatives onto the surface, silica reduced the activity of the crosslinking system, prolonging the optimal vulcanization time of NR compounds and reducing the crosslinking degree of the elastomer. However, silica-filled NR exhibited the highest thermal stability. Hydrotalcite increased the crosslink density and, consequently, the mechanical properties of the vulcanizates, but deteriorated their thermal stability. ILs beneficially influenced the cure characteristics of NR compounds, as well as the crosslink density and mechanical performance of the vulcanizates, particularly those filled with silica. Cellulose did not significantly affect the vulcanization of NR compounds and crosslink density of the vulcanizates compared to the unfilled elastomer, but deteriorated their tensile strength. On the other hand, cellulose improved the thermal stability and did not considerably alter the damping properties of the vulcanizates.

Effects of ionic liquid on cellulosic nanofiller filled natural rubber bionanocomposites

Cellulosic nanofillers are sustainable replacements of synthetic fillers while the agglomeration limits their potentials in high-performance rubber bionanocomposites. Herein, we investigate the effects of ionic liquid (IL) on cellulose nanocrystal and cellulose nanofibril filled natural rubber (NR) compounds and vulcanizates. The results indicate that IL improves the dispersion of cellulosic nanofillers, crosslinking density of NR matrix and mechanical strength of the vulcanizates. Invesigations of viscoelastic rheological behaviors show amplitude of Payne effect faints in compounds and raises relatively in vulcanizates with the increment of cellulosic nanofillers and IL.

Controlled individual and partial polyethylene nanofibers with high Tm2 prepared by PPM-supported Cp2TiCl2 catalysts

Controlled individual and partial nanofibrous polyethylenes with high second melting point (T_m2) were obtained through ethylene-confined polymerization using a porous polymer microsphere (PPM)-supported Cp₂TiCl₂ catalyst.

A functional modified graphene oxide/nanodiamond/nano zinc oxide composite for excellent vulcanization properties of natural rubber

A modified graphene oxide/nanodiamond/nanozinc oxide (MGO/ND/nanoZnO) functional hybrid filler is designed and prepared to improve the vulcanization efficiency of a rubber composite and to reduce the use of ZnO. ND was grafted onto graphite oxide with the aid of 4,4'-methylene diphenyl diisocyanate (MDI). NanoZnO, with high surface activity, was then loaded onto the MGO/ND complex through the wet chemical method, in order to synthesize the MGO/ND/nanoZnO functional hybrid filler. Rubber composites were prepared using the rubber latex composite method and their vulcanization behaviors were investigated. Our results show that the MGO/ND/nanoZnO functional hybrid filler can remarkably improve the vulcanization behaviors of the rubber composite. Compared with that of pure natural rubber (NR), the vulcanization activation energy of the rubber composite was reduced by approximately 16%. Moreover, the vulcanization efficiency can be improved by 63% (i.e., the optimum cure time is shortened from the original 405 s to 150 s) after the same amount of traditional ZnO was replaced by the functional hybrid filler loaded with 1 wt% nanoZnO. The prepared MGO/ND/nanoZnO functional hybrid filler thus provides a promising alternative to improve the vulcanization efficiency of rubber composites.

High Melting Point of Linear, Spiral Polyethylene Nanofibers and Polyethylene Microspheres Obtained Through Confined Polymerization by a PPM-Supported Ziegler-Natta Catalyst

In this work, different types of polyethylene (linear, spiral nanofibers and microspheres) were obtained via confined polymerization by a PPM-supported Ziegler-Natta catalyst. Firstly, the Ziegler-Natta catalyst was chemical bonded inside the porous polymer microspheres (PPMs) supports with different pore diameter and supports size through chemical reaction. Then slightly and highly confined polymerization occurred in the PPM-supported Ziegler-Natta catalysts. SEM results illustrated that the slightly confined polymerization was easy to obtain linear and spiral nanofibers, and the nanofibers were observed in polyethylene catalyzed by PPMs-1#/cat and PPMs-2#/cat with low pore diameter (about 23 nm). Furthermore, the highly confined polymerization produced polyethylene microspheres, which obtained through other PPM-supported Ziegler-Natta catalysts with high pore diameter. In addition, high second melting point (Tm2: up to 143.3 °C) is a unique property of the polyethylene obtained by the PPM-supported Ziegler-Natta catalyst after removing the residue through physical treatment. The high Tm2 was ascribed to low surface free energy (σe), which was owing to the entanglement of polyethylene polymerized in the PPMs supports with interconnected multi-modal pore structure.

Past, Present and Future Perspectives on Halloysite Clay Minerals

Halloysite nanotubes (HNTs), clay minerals belonging to the kaolin groups, are emerging nanomaterials which have attracted the attention of the scientific community due to their interesting features, such as low-cost, availability and biocompatibility. In addition, their large surface area and tubular structure have led to HNTs' application in different industrial purposes. This review reports a comprehensive overview of the historical background of HNT utilization in the last 20 years. In particular it will focus on the functionalization of the surfaces, both supramolecular and covalent, following applications in several fields, including biomedicine, environmental science and catalysis.

Ionic Liquids and Calcium Oxide Grafted with Allylmalonic Acid Applied to Support the Peroxide Crosslinking of an Ethylene-Propylene Copolymer

Nanosized calcium oxide (CaO) featuring a surface grafted with allylmalonic acid (ALA) was used to increase the efficiency of the peroxide crosslinking of an ethylene-propylene copolymer (EPM) filled with silica nanoparticles. In this study, 1-butyl-3-methylimidazolium ionic liquids (ILs) with different anions were applied to improve the dispersion of CaO/ALA and silica nanoparticles in the EPM copolymer, as well as to catalyze the interfacial crosslinking reactions. In this article, we discuss the effects of CaO/ALA and ILs on the curing characteristics, vulcanization temperature, crosslink density, mechanical properties, and thermal stability of EPM, as well as the resistance of EPM to weather aging. The CaO/ALA with ILs reduced the vulcanization time of the rubber compounds without a significant effect on the vulcanization temperature. Their application resulted in an increased vulcanizate crosslink density, as well as improved tensile strength compared to the pure peroxide system. The influence of 1-butyl-3-methylimidazolium ILs on EPM vulcanization and performance depends on the anion present in the molecules of the ionic liquid. The most active IL seems to be that with the tetrafluoroborate anion.

FUNCTIONALIZED SILICA AS AN ECO-FRIENDLY VULCANIZATION ACCELERATOR TO ENHANCE THE INTERFACIAL INTERACTION IN NR/SILICA COMPOSITES

Xanthate is a class of non-toxic, rapid, and eco-friendly rubber vulcanization accelerator, but it is seldom used in the rubber industry because of its poor thermostability and ease of decomposition. To overcome these drawbacks, silica supported sodium isobutyl xanthate (silica-s-SIBX) was prepared by chemically bonding SIBX onto the silica surface. After loading, the initial degradation temperature (T0), maximum degradation temperature (Tp), and final decomposition temperature (Tf) of silica-s-SIBX were increased by 85.8, 118.9, and 146.9 °C, respectively. Meanwhile, silica-s-SIBX could not only improve the dispersion of fillers in the rubber but also enhance the interfacial interaction between silica and the rubber matrix. Therefore, it may offer new scientific and technological opportunities for preparation of green additives in the rubber industry.

Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids

New thiol-functionalized carboxylate ionic liquids (ILs), varying both for the cation and for the anion structures, have been prepared as new potential redox switching systems by reacting either 3-mercapto propionic acid (3-MPA) or N-acetyl-cysteine (NAC) with commercially available methyl carbonate ILs. Different ratios of thiol/disulfide ILs were obtained depending both on the acid employed in the neutralization reaction and on the reaction conditions used. Surprisingly, the imidazolium ILs displayed limited thermal stability which resulted in the formation of an imidazole 2-thione and a new sulfide ionic liquid. Conversely, the formation of the imidazole 2-thione was not observed when phosphonium disulfide ILs were heated, thus confirming the involvement of the imidazolium ring in an unexpected side reaction. An insight into the mechanism of the decomposition has been provided by means of DFT calculations.

The emerging applications of click chemistry reactions in the modification of industrial polymers

Click chemistry reactions have been applied to the modification of major industrial polymers by analysing the synthetic approaches and the resulting material properties.

HYBRID SILANE TECHNOLOGY IN SILICA-REINFORCED TREAD COMPOUND

The use of a silane coupling agent in silica-reinforced tread can effectively improve silica dispersion in the rubber matrix and strengthen the interfacial interaction between the rubber and filler; this is beneficial to the enhancement of tire grip under wet conditions and reduces tire rolling resistance. The monofunctional silane n-octyltriethoxysilane (OTES) can react with the silanol group of the silica surface and hence improve silica dispersion. It can also suppress silica reaggregation during tire processing. Two hybrid silanes, OTES and 3-mercaptopropylethoxy-bis(tridecyl-pentaethoxy-siloxane) (Si747) or OTES and bis(triethoxysilylpropyl)tetrasulfide (TESPT), were filled in silica-reinforced tread compounds. The effect of the two hybrid silanes on the silica was investigated via Fourier transform infrared spectroscopy and thermogravimetric analysis. The processing ability of the silica-filled compounds and the performance of the vulcanizates were also investigated. Our experimental results show that OTES is able to further react with the silica following reaction between the TESPT and silica and that it should be added when the molar amount of TESPT or Si747 is constant, to prevent reduction of the cross-link density. Furthermore, the addition of OTES can extend the scorch time, especially in Si747 and OTES compounds. In addition, OTES can improve silica dispersion and only has a slightly negative effect on the physical properties of vulcanizates.

Layered double hydroxide anchored ionic liquids as amphiphilic heterogeneous catalysts for the Knoevenagel condensation reaction

In this paper, three solid base catalysts of LDH-IL-Cn (n = 4, 8, 12) were synthesized by adopting an exfoliation/assembly approach. The as-prepared catalyst showed excellent activity and selectivity for the Knoevenagel reaction in aqueous solution.

Recent Advances on Surface Modification of Halloysite Nanotubes for Multifunctional Applications

Halloysite nanotubes (HNTs) are natural occurring mineral clay nanotubes that have excellent application potential in different fields. However, HNTs are heterogeneous in size, surface charge, and formation of surfacial hydrogen bond, which lead to weak affinity and aggregation at a certain extent. It is very important to modify the HNTs’ surface to expand its applications. In this review, the structural characteristics, performance, and the related applications of surface-modified HNTs are reviewed. We focus on the surface-modified variation of HNTs, the effects of surface modification on the materials and related applications in various regions. In addition, future prospects and the meaning of surface modification were also discussed in HNTs studies. This review provides a reference for the application of HNTs modifications in the field of new nanomaterials.

EFFECT OF FILLER TYPE AND CONTENT ON PHYSICAL AND MECHANICAL PROPERTIES OF NR/SBR NANOCOMPOSITE BLEND

The effect of type and content of nanofiller on the cure behavior, cure characteristics, and mechanical and dynamic mechanical thermal properties of the vulcanized SBR/NR (30/70) blend nanocomposites containing carbon black were investigated. Halloysite nanotube (HNT) and calcium carbonate (CaCO3) nanoparticles were used as reinforcing agents at different levels ranging from 0 to 5 phr. Two nanofillers affected the cure characteristics of the blended vulcanizates in opposite ways. While the gradual incorporation of HNT into the elastomer blend shortened the scorch time along with an increase in the effective torque of resulting nanocomposite compared to the unfilled blend, the progressive addition of CaCO3 into the blend monotonically prolonged the scorch time in conjunction with a decrease in the effective torque of vulcanizate sample. Mechanical tests showed enhanced elastic modulus and tensile strength of HNT-filled nanocomposites as the HNT content was increased. Nanocomposites reinforced with HNT exhibited significantly higher extensibility than the unfilled blend. In the case of CaCO3-filled nanocomposites, the elastic modulus and ultimate strength decreased upon the addition of CaCO3 nanoparticles, whereas the strain at break showed a substantial increase compared to unfilled compound. Dynamic mechanical thermal analysis results revealed a monotonic shift of damping peak's temperature toward higher temperatures with HNT loading in HNT-filled vulcanizate nanocomposites. For CaCO3-filled nanocomposites, the damping peak's temperature shifted to higher temperatures at first and then shifted back to lower temperatures at higher loadings of CaCO3. The damping peak's intensity of the CaCO3-filled nanocomposites was considerably higher than the unfilled blend, indicating higher damping capability in these systems.

The Impact of Halloysite on the Thermo-Mechanical Properties of Polymer Composites

Nanotubular clay minerals, composed of aluminosilicate naturally structured in layers known as halloysite nanotubes (HNTs), have a significant reinforcing impact on polymer matrixes. HNTs have broad applications in biomedical applications, the medicine sector, implant alloys with corrosion protection and manipulated transportation of medicines. In polymer engineering, different research studies utilize HNTs that exhibit a beneficial enhancement in the properties of polymer-based nanocomposites. The dispersion of HNTs is improved as a result of pre-treating HNTs with acids. The HNTs' percentage additive up to 7% shows the highest improvement of tensile strength. The degradation of the polymer can be also significantly improved by doping a low percentage of HNTs. Both the mechanical and thermal properties of polymers were remarkably improved when mixed with HNTs. The effects of HNTs on the mechanical and thermal properties of polymers, such as ultimate strength, elastic modulus, impact strength and thermal stability, are emphasized in this study.

Preparation of crosslinked porous polyurea microspheres in one-step precipitation polymerization and its application for water treatment

Porous polyurea microspheres (PPUMs) were simply prepared in one-step by the precipitation polymerization of isophorone diisocyanate with triethylenetetramine and SiO₂ particles.