Curing characteristics and mechanical properties of rattan‐powder‐filled natural rubber composites as a function of filler loading and silane coupling agent

Curing characteristics, tensile properties, morphological studies of tensile fractured surfaces using scanning electron microscopy (SEM), and the extent of rubber filler interactions of rattan‐powder‐filled natural rubber (NR) composites were investigated as a function of filler loading and silane coupling agent (CA). NR composites were prepared by the incorporation of rattan powder at filler loading range of 0–30 phr into a NR matrix with a laboratory size two roll mill. The results indicate that in the presence of silane CA, scorch time (t_s2), and cure time (t₉₀) of rattan‐powder‐filled NR composites were shorten, while, maximum torque (M_H) increased compared with NR composites without silane CA. Tensile strength and tensile modulus of composites were enhanced whereas elongation at break reduced in the presence of silane CA mainly due to increase in rubber‐filler interaction. It is proven by SEM studies that the bonding between the filler and rubber matrix has improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Autoclaved aerated concrete waste (AACW): An alternative filler material for the natural rubber industry

Material waste from the production of autoclaved aerated concrete, a porous material, should be considered as a valuable byproduct for use as a filler material for the rubber industry. Natural rubber (NR) composites filled with different loading (over the range of 0–60 phr) of autoclaved aerated concrete waste (AACW) as a new eco‐friendly material were produced using two roll mills and then were studied for their cure characteristics, mechanical and aging properties, and morphology, and also compared with commercial fillers, calcium carbonate (CaCO₃), and silica (SiO₂). In most cases, the cure characteristics and mechanical and aging properties of the SiO₂‐filled NR composites were significantly better than those of the AACW‐ and CaCO₃‐filled NR composites. However, these properties for AACW‐filled composites appeared to be higher than CaCO₃‐filled composites. The reason for this could be due to a larger surface area which is both porous and of an irregular shape of the AACW filler used. Scanning electron microscope images showed that the morphology of the rubber filled with SiO₂ was finer and more homogenous compared with the rubber filled with AACW or CaCO₃. Overall results revealed that the reinforcement ability of AACW‐filled NR composites was generally better when compared with CaCO₃‐filled NR composites; therefore, AACW can be used effectively as a cheaper filler for production of rubber products where end‐use properties of a rubber product is specifically required. POLYM. COMPOS., 36:2030–2041, 2015. © 2014 Society of Plastics Engineer     

Dynamic mechanical properties of oil palm microfibril‐reinforced natural rubber composites

The dynamic mechanical properties of macro and microfibers of oil palm‐reinforced natural rubber (NR) composites were investigated as a function of fiber content, temperature, treatment, and frequency. By the incorporation of macrofiber to NR, the storage modulus (E') value increases while the damping factor (tan δ) shifts toward higher temperature region. As the fiber content increases the damping nature of the composite decreases because of the increased stiffness imparted by the natural fibers. By using the steam explosion method, the microfibrils were separated from the oil palm fibers. These fibers were subjected to treatments such as mercerization, benzoylation, and silane treatment. Resorcinol‐hexamethylenetetramine‐hydrated silica was also used as bonding agent to increase the fiber/matrix adhesion. The storage modulus value of untreated and treated microfibril‐reinforced composites was higher than that of macrofiber‐reinforced composites. The T_g value obtained for this microfibril‐reinforced composites were slightly higher than that of macrofiber‐reinforced composites. The activation energy for the relaxation processes in different composites was also calculated. The morphological studies using scanning electron microscopy of tensile fracture surfaces of treated and untreated composites indicated better fiber/matrix adhesion in the case of treated microfibril‐reinforced composites. Finally, attempts were made to correlate the experimental dynamic properties with the theoretical predictions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical properties of surface‐modified ultra‐high molecular weight polyethylene fiber reinforced natural rubber composites

The mechanical properties of ultra‐high molecular weight polyethylene (UHMWPE) fibers reinforced natural rubber (NR) composites were determined, and the effects of fiber surface treatment and fiber mass fraction on the mechanical properties of the composites were investigated. Chromic acid was used to modify the UHMWPE fibers, and the results showed that the surface roughness and the oxygen‐containing groups on the surface of the fibers could be effectively increased. The NR matrix composites were prepared with as‐received and chromic acid treated UHMWPE fibers added 0–6 wt%. The treated UHMWPE fibers increased the elongation at break, tear strength, and hardness of the NR composites, especially the tensile stress at a given elongation, but reduced the tensile strength. The elongation at break increased markedly with increasing fiber mass fraction, attained maximum values at 3.0 wt%, and then decreased. The tear strength and hardness exhibited continuous increase with increasing the fiber content. Several microfibrillations between the fiber and NR matrix were observed from SEM images of the fractured surfaces of the treated UHMWPE fibers/NR composites, which meant that the interfacial adhesion strength was improved. POLYM. COMPOS., 38:1215–1220, 2017. © 2015 Society of Plastics Engineers     

Influence of ionic liquid on the polymer–filler coupling and mechanical properties of nano‐silica filled elastomer

The natural rubber (NR) nanocomposites were fabricated by filling ionic liquid (1‐allyl‐3‐methyl‐imidazolium chloride, AMI) modified nano‐silica (nSiO₂) in NR matrix through mechanical mixing and followed by a cure process. Based on the measurements of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance spectroscopy, and Raman spectroscopy, it was proved that AMI could interact with nSiO₂ through hydrogen bonds. With the increase of AMI content, the curing rate of nSiO₂/NR increased. The results of bound rubber and dynamic mechanical properties showed that polymer–filler interaction increased with the modification of nSiO₂. Morphology studies revealed that modification of nSiO₂ resulted in a homogenous dispersion of nSiO₂ in NR matrix. AMI modified nSiO₂ could greatly enhance the tensile strength and tear strength of nSiO₂/NR nanocomposites. Compared to unmodified nSiO₂/NR nanocomposite, the tensile strength of AMI modified nSiO₂/NR nanocomposite increased by 102%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44478.     

Interfacial interactions and properties of natural rubber–silica composites with liquid natural rubber as a compatibilizer and prepared by a wet‐compounding method

Natural rubber–silica [W(NR–SiO₂)] composites were prepared by wet‐compounding technology with liquid natural rubber (LNR) as a compatibilizer. The effects of the LNR content and wet‐compounding technology on the filler dispersion, Payne effect, curing characteristics, mechanical properties, and interfacial interactions were investigated. The results show that the incorporation of LNR promoted vulcanization and decreased the Payne effect of the W(NR–SiO₂) composites. With the addition of 5 phr LNR, the remarkable improvements in the mechanical properties of the W(NR–SiO₂) vulcanizates were correlated with the improved silica dispersion and strengthened interfacial bonding. Furthermore, the W(NR–SiO₂) vulcanizates containing LNR exhibited improvements in both the wet‐skid resistance and rolling‐resistance performance. The interfacial interactions, quantitatively evaluated by the Mooney–Rivlin equation and Lorenz–Park equation on the basis of the rubber elasticity and reinforcement theory, were strengthened in the presence of LNR. Accordingly, an interfacial structural model was proposed to illustrate the improvements in the mechanical properties of the W(NR–SiO₂) composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46457.     

Surface modification of aramid fibers with CaCl2 treatment and secondary functionalization of silane coupling agents

Aramid fibers have excellent mechanical properties as the main reinforcing filler in high-performance composites. However, the adhesion properties between fibers and most polymer matrices were poor. In this study, aramid fiber (AF) was modified by KH550 through surface coating based on the treatment with CaCl₂ solution. The new surface treated with complexing agents could act as an active platform for secondary reactions for further modification. The surface morphology and composition of the treated aramid fibers were tested by scanning electron spectroscopy and X-ray photoelectron spectroscopy, the interlaminar shear strength and the tensile strength of aramid fiber-reinforced polymer (AFRP) of were evaluated. The results showed that the silane coupling agent KH550 was successfully grafted onto the surface of aramid fibers after treatment with CaCl₂. Interlayer shear strength is greatly improved and the tensile strength of AFRP through further grafting with KH550 on the surface treated with CaCl₂ was improved by 48.7%, compared with untreated aramid fiber. In the current scenario, this study is of immense importance because it validates the possibility of secondary modification after fiber complexation modification and useful modification methods, and provides a new direction for the modification of AF.     

Study on Tensile,Electrical, and Thermal Properties of Aluminium Particle Filled Natural Rubber (NR) and Ethylene-Propylene-Diene Terpolymer (EPDM) Composites

Comparative studies on the effect of aluminium particles in natural rubber (NR) and ethylene-propylene-diene terpolymer (EPDM) were conducted. The incorporation of aluminium particles in NR or EPDM composites increased the cure time, t ₉₀, and scorch time, t _S2 . At a fixed filler loading, EPDM composites exhibited longer t ₉₀ and t _S2 than NR composites. The results also indicate that the maximum torque, M _H of aluminium filled NR and EPDM composites increase with increasing filler loading. For tensile properties, EPDM composites show lower tensile properties than NR composites. Thermogravimetric analysis (TGA) results show that aluminium filled EPDM composites have better thermal stability than aluminium filled NR composites.

The results for electrical properties indicate that the electrical properties of aluminium filled NR and EPDM composites increase with increase in filler loading.     

Development and characterization of graphitic carbon nitride as nonblack filler in natural rubber composites

A new type of elastomeric composite containing natural rubber (NR) and graphitic carbon nitride (g-C₃N₄) has been successfully prepared with the reinforced property. The reinforcing effect of g-C₃N₄ in NR composites was examined by cure, mechanical, morphological, and swelling studies. Besides, epoxidized NR with 50-mol % epoxy level (ENR-50) was used as a compatibilizer to enhance the hydrophilic g-C₃N₄ filler capacity for hydrophobic NR composites. At the same filler load level, the mechanical properties of NR/g-C₃N₄ composites, such as tensile strength and tensile modulus, were consistently increased with increased ENR-50 content. To note, the ENR compatibilized composites have shown better-reinforced performance, which has been attributed to the hydrogen bonding interactions between the uncondensed amine groups in g-C₃N₄ and the polar groups in ENR. We believe that these newly prepared NR composites based on g-C₃N₄ as nonblack filler and ENR-50 as compatibilizer can find potential applications in modern day rubber research. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48136.     

Improving properties of ceramic silicone rubber composites using high vinyl silicone oil

Reactive high vinyl silicone oil (HVSO) was selected to prepare the ceramic silicone rubber composites. The effects of HVSO on the mechanical properties and thermal stabilities of ceramic silicone rubber composites were investigated. The structures of the cross‐linked network of silicone rubber with or without HVSO were studied. The intermolecular space of silicone rubber was enlarged, and the cross‐linked point was concentrated by addition of HVSO, which was demonstrated by cross‐linking densities, scanning electron microscope (SEM) images, and dynamic mechanical analysis (DMA). The cross‐linked network model was formed with the slipping of the cross‐linked points along with the silicone rubber chain. Mechanical properties of composites were enhanced by the formation of this cross‐linked network. The tear strength, tensile strength, and elongation at break of the composites were increased by 18.5%, 13.2%, and 37.4% by the adding of 2 phr HVSO, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41864.     

Enhancing interfacial adhesion performance by using poly(vinyl alcohol) in (low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) composites

The effects of (a) the chemical modification of water hyacinth fiber by poly(vinyl alcohol) (WHF‐_PVA) and (b) loading on the properties of low‐density polyethylene (LDPE)/(natural rubber (NR))/(water hyacinth fiber (WHF)) composites were studied. Mechanical properties, water absorption behavior, morphology, and thermal properties were examined; X‐ray diffraction and infrared spectroscopic analysis were done. The results indicated that LDPE/NR/WHF‐_PVA composites had higher values of tensile strength, Young's modulus, melting temperature, and water absorption resistance but lower elongation at break than LDPE/NR/WHF composites. The LDPE/NR/WHF‐_PVA composites had better interfacial adhesion between the matrix and the fibers than LDPE/NR/WHF composites, as shown by SEM results. The LDPE/NR/WHF‐_PVA composites exhibited lower interparticle spacing than LDPE/NR/WHF composites, a feature which enhanced the interparticle interaction between the water hyacinth fibers and the LDPE/NR matrix. J. VINYL ADDIT. TECHNOL., 19:47–54, 2013. © 2012 Society of Plastics Engineers     

Preparation and performance of oleylamine modified silica-reinforced natural rubber composites

Oleylamine (OA) modified silica (SiO₂-g-OA) was prepared using γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) and OA, silica/natural rubber (NR) and SiO₂-g-OA/NR composites were prepared by mechanical blending in an internal mixer, and SiO₂-g-OA was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analyzer, and contact angle analyzer. The mechanical properties, abrasion resistance, curing characteristics, Payne effect, and morphology of silica/NR and SiO₂-g-OA /NR composites were investigated using universal testing machine, Akron abrasion tester, rubber processing analyzer, and scanning electron microscope, respectively. The results showed that SiO₂-g-OA became more hydrophobic and had better compatibility with NR. Moreover, SiO₂-g-OA/NR had weaker Payne effect, better vulcanization performance, and more excellent mechanical properties. As the content of filler was more than 30 phr, SiO₂-g-OA/NR had lower rolling resistance and higher wet skid resistance. Compared with silica modified by other coupling agents, SiO₂-g-OA had the best reinforcement effect on NR.     

Cure characteristics,mechanical, thermal,and coloring properties of natural rubber/dye‐loaded shell powder composites

To explore the application of shell powder (SP) in rubber, a dye‐loaded SP (DSP) bio‐filler based on SP and Congo red was incorporated into natural rubber (NR). The adsorption experiments demonstrated that the maximum monolayer adsorption capacity of Congo red onto SP was 69.3 mg/g. The effect of aluminate coupling agent and DSP was investigated by evaluating the cure characteristics, mechanical, thermal, and coloring properties of NR/DSP composites. It was suggested that the optimum amount of aluminate coupling agent was 2 wt %, and the best tensile strength (24.80 MPa) of vulcanizates was achieved at the DSP content of 20 phr, while other mechanical properties such as tear strength kept increasing with the addition of DSP. Furthermore, the improved thermal stability and uniform color distribution of the NR composites was obtained. The results indicate that DSP is promising to become a low‐cost filler and pigment for rubber materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45750.     

Comparison of thermoset soy protein resin toughening by natural rubber and epoxidized natural rubber

Fully bio‐based soy protein isolate (SPI) resins were toughened using natural rubber (NR) and epoxidized natural rubber (ENR). Resin compositions containing up to 30 wt % NR or ENR were prepared and characterized for their physical, chemical and mechanical properties. Crosslinking between SPI and ENR was confirmed using ¹H‐NMR and ATR‐FTIR. All SPI/NR resins exhibited two distinctive drops in their modulus at glass transition temperature (T_g ) and degradation temperature (T_d ) at around ?50 and 215 °C, corresponding to major segmental motions of NR and SPI, respectively. SPI/ENR resins showed similar T_g and T_d transitions at slightly higher temperatures. For SPI/ENR specimens the increase in ENR content from 0 to 30 wt % showed major increase in T_g from ?23 to 13 °C as a result of crosslinking between SPI and ENR. The increase in ENR content from 0 to 30 wt % increased the fracture toughness from 0.13 to 1.02 MPa with minimum loss of tensile properties. The results indicated that ENR was not only more effective in toughening SPI than NR but the tensile properties of SPI/ENR were also significantly higher than the corresponding compositions of SPI/NR. SPI/ENR green resin with higher toughness could be used as fully biodegradable thermoset resin in many applications including green composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44665.     

Properties of (Low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) composites: The effect of polyaniline

The effects of polyaniline (PANI)‐modified water hyacinth fiber on the properties of (low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) (LDPE/NR/WHF) composites were studied. The composites were prepared by using a Brabender Plasticorder at 160^oC and a rotor speed of 50 rpm for 6 minutes. LDPE/NR/WHF_PANI composites exhibited higher tensile strength, Young's modulus, elongation at break, melting temperature, and electrical conductivity but lower molar sorption, capacitance, percentage crystallinity, and interparticle spacing than LDPE/NR/WHF composites. Scanning electron microscopy morphology showed a better interfacial adhesion of PANI‐modified water hyacinth fiber (WHF_PANI) and the LDPE/NR phases than when unmodified WHF was used. J. VINYL ADDIT. TECHNOL., 20:122–130, 2014. © 2014 Society of Plastics Engineers     

Effects of PBO fiber and clay on the mechanical,morphological, and dynamic mechanical properties of NR/HDPE blends

Poly(p‐phenylene‐2,6‐benzobisoksazole) (PBO) and natural rubber (NR)/high density polyethylene (HDPE) composites were melt‐blended in a Haake internal mixer. The tensile strength, tensile modulus, and impact strength increased with fiber loading and optimized at 20%. Incorporation of clay into the NR/HDPE/PBO composites resulted in an improvement of tensile strength for NR/HDPE/PBO composites compared to the systems without clay. However, addition of clay was only effective at low contents (5–7.5%). Additional improvement of tensile strength, tensile modulus, and impact strength of the hybrid composite was observed on addition of liquid natural rubber (LNR). Scanning electron micrographs of the samples had indicated that the presence of clay decreased the domain size of the dispersed phase. Results on dynamic response showed that incorporation of clay and LNR into the composites had increased the storage modulus and reduced the tan δ. The shift of glass transition temperature (T_g) to higher values for composites also indicated good interaction between the fiber and the matrix. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Construction of an in situ interfacial layer for aramid fiber reinforced styrene butadiene rubber composites

In this work, the in situ interface layer composite was prepared by using the coating agent dispersion. Aramid fiber (AF) was modified with lithium chloride aqueous solution, and then coated with the blends of a low-molecular weight maleated polybutadiene liquid rubber (MLPB), the epoxy resin (E51), and 2-ethyl-4-methylimidazole (2E4MZ). The in situ interface layer was formed via the reaction of epoxy group with anhydride group in the presence of the accelerator 2E4MZ and covulcanization of MLPB with styrene butadiene rubber (SBR) in the process of preparing vulcanized AF reinforced SBR. It can be seen from analysis of scanning electronic microscopy, attenuated total reflection Fourier transform infrared, and thermogravimetric analysis that the in situ interfacial layer was a uniform and dense interfacial layer on the fiber surface and was not be destroyed during processing. The results of the dynamic mechanical analysis and mechanical properties showed that the in situ interface layer formed in processing had higher flexibility and better integrity than the interface layer prepared before processing, which is favorable for stress relaxation, and the in situ interface layer imparts better tensile strength and tear strength to the composite. The 100% modulus of composites with in situ interface layers was 14.6% higher than that of composites prepared without uncoated AF.     

Green Composites from Natural Rubber and Oil Palm Fiber: Physical and Mechanical Properties

Natural rubber (NR) composites were prepared by incorporating short oil palm fibers of different lengths (viz., 2, 6, 10, and 14 mm) into natural rubber matrix in a mixing mill according to a base formulation. The curing characteristics of the mixes were studied and the samples were vulcanized at 150°C. The vulcanization parameters, processability characteristics, and tensile properties of these composites were analyzed. The effects of fiber length, orientation, loading, and fiber-matrix interaction on the mechanical properties of the green composites were studied. The reinforcement property of the alkali-treated fiber was compared with that of the untreated one. The extent of fiber orientation was studied from green strength measurements. From anisotropic swelling studies, the extent of fiber alignment and the strength of fiber–rubber interface adhesion were analyzed. Scanning electron microscopic (SEM) studies were carried out to analyze the fiber surface morphology, fiber pullout, and fiber–rubber interface.     

Effect of a silane coupling agent on the properties of white rice husk ash–polypropylene/natural rubber composites

White rice husk ash (WRHA)–polypropylene (PP)/natural rubber (NR) composites were prepared using a Brabender Plasticorder at 180 °C and a rotor speed of 50 rev min^?1. The mechanical and water‐absorption properties were studied. The incorporation of WRHA into the PP/NR matrix has resulted in the improvement of the tensile modulus; however, the tensile strength, elongation at break and stress at yield decreased with increasing WRHA loading. Poor filler matrix interactions are believed to be responsible for the decrease in the properties. Incorporation of a silane coupling agent, 3‐aminopropyl triethoxysilane (3‐APE), improved tensile modulus, tensile strength and stress at yield of the composites. Water‐absorption studies indicate that the use of the coupling agent reduced the amount of water absorbed by the composites. © 2001 Society of Chemical Industry     

Influence of nanocrystalline cellulose on structure and properties of natural rubber/silica composites

A complex of resorcinol and hexamethylenetetramine (RH) was utilized to modify nanocrystalline cellulose (NCC). The modified NCC (MNCC) was then mixed with natural rubber (NR) filled silica. The structure, processing properties, mechanical properties, and dynamic compression fatigue properties of the NR/MNCC/Silica nanocomposites were characterized by scanning electron microscopy (SEM), rubber processing analyzer, electronic tensile machine, and dynamic compression fatigue performance tester. The results showed that the processing properties, mechanical properties, and dynamic compression fatigue properties of NR/MNCC/Silica nanocomposites were substantially improved over NR/Silica composites. Their better performances in terms of processing, mechanical properties, heat build‐up, and permanent set were correlated to the better dispersion of MNCC and stronger interface interaction between NR and MNCC than NR/Silica composites. POLYM. COMPOS., 36:861–868, 2015. © 2014 Society of Plastics Engineers