Hybrid filler and coupling agent: Effect of partial replacement of carbon black with talc and silane on properties of natural rubber compound

The studies on cure index, swelling behaviour, tensile and thermo-oxidative properties of unfilled natural rubber (NR) compounds in the presence of alkanolamide (ALK) were carried out. As a rubber additive, the ALK was added into the NR compounds at various loadings (0.2, 0.4, 0.6, 0.8, and 1.0 phr). It was found that the cure indexes of NR compounds with ALK were higher than that of NR compound without ALK (control compound). It was also found that ALK exhibited higher tensile modulus and tensile strength up to 0.6 phr of loading and then decreased with further increases in the loading. The swelling test revealed that 0.6 phr of ALK in the unfilled NR compound exhibited the highest degree of crosslink density which correlated to the highest tensile modulus and tensile strength of the NR vulcanisates. The ALK increased the heat aging resistance of the NR vulcanisates.

This work highlights the synthesis of high purity silica from rice husks and the effect of rice husk silica (RHS) loading on the mechanical, physical, and thermal properties of natural rubber (NR) compounds. The RHS was synthesised using the solvent-thermal extraction method, which was adopted from TAPPI T204 (2007) and TAPPI T264 (1997) standards with some modifications. The treatment successfully produced high purity RHS particles, with 99.9% SiO2 content between 100 to 300 nm in size. The high purity RHS was then incorporated in NR compounds at 2, 4, 6, 8, and 10 parts per hundred rubber (phr). Even without any surface modification, the high purity RHS-filled NR compounds showed tremendous improvements in strength-related properties at the optimum loading of 4 phr. In addition, the thermal stability of the NR compounds was remarkably improved with the addition of RHS.

Study the influence of high concentrations of antioxidants N-isopropyl-N-phenyl-p-phenylenediamine (IPPD) and 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) and the mixing time of the vulcanization physical properties, thermal properties, mechanical properties and structure micro on natural rubber compound has been done. The purpose of this study is to compare the effect of anti-oxidants types IPPD and TMQ and mixing time of vulcanization of the physical properties, mechanical properties, microstructure and elemental composition of the synthesis of natural rubber compound. Processes of vulcanization with variations in the concentration of antioxidant IPPD and TMQ: 2, 3, and 4 grams and mixing time: 20, 30, and 40 minutes. Analysis characterization of physical properties and mechanical properties of natural rubber compound showed that the maturity value 0,499Nm (TMQ) and 0.489 Nm (IPPD), Mooney viscosity value of 26.7 (TMQ) and 20.8 (IPPD), the value of the elongation at break 583.75 % (IPPD), and 552.63% (TMQ) as well as the value of tensile strength of 28.108 M.Pa (TMQ), and 27.986 M.Pa (IPPD). Analysis of thermal properties of natural rubber compound antioxidant IPPD with DTA shows there are three endothermic peak on the curve that is temperature 405°C, 550°C and 660°C and tested by TGA showed that the curve of the total reduction in the sample are 81.745% and compound rubber antioxidant TMQ with the analysis of DTA also contained 3 endothermic peak at a temperature 397,21°C, 514,02°C, and 610,27°C and TGA analysis shows the curve of the total sample of 82.356% reduction. Gsi fun group analysis rubber-antioxidant compound IPPD / TMQ with FTIR spectrophotometer shows some typical infrared absorption peak at the wave number (1 / λ) 833-895 cm-1 for cluster / CH bonds, 1,313 cm-1 for group / single bond Si-O, 1368 cm-1 to g ugus / single bond CC, 1507 cm-1, for cluster / bond C = C, 1665 cm-1For cluster / bond-C = O, 2128 cm-1 is the group / bond CN single, 3371cm-1 for group-OH, 3506 cm-1 for cluster / CH3 bond and 3585 cm-1 showed the presence of vibration in the cluster / bond-NH. The results of morphological observation with SEM produces uneven surface (homogeneous) and are compatible at 2000 times magnification, as well as the test composition by EDX spectroscopy showed that the biggest element in the rubber compound is carbon and Zn, S, Ca, Si, Mg, Al, N. This shows that the natural rubber compound antioxidant IPPD / TMQ meet the standard of "Mechanical Properties of Industrial Tyre rubber Compounds".

This study aims to determine the mechanical properties of natural rubber compounds with variations of OPBA nanoparticle fillers and carbon black. Preparation methods for natural rubber compounds using Open Mill. Indonesian rubber standard -20 (SIR-20) mixed with anti-oxidants, activators, curing agents, accelerators and OPBA nanoparticle fillers size 56.31 nm and commercial Carbon black type (N330) with variations (0,2,4,6 and 8)% wt. The results showed that tensile strength increased with the increase in the composition of OPBA nanoparticles and carbon black, as well as the elongation of break and hardness. The best composition of OPBA filler 8% wt showed a hardness of 52 Shore A, a tensile strength of 1.7 MPa, an elongation of break 150%. The best composition of carbon black 8% wt filler with a hardness of 55 Shore A, a tensile strength of 2.5 MPa, elongation breakdown of 140%.

The influence of organically modified nanoclay‐carbon black (CB) hybrid filler on the curing behavior of natural rubber (NR) was explored in this investigation. Here an effort was paid to understand the curing kinetics of organomodified nanoclay filled rubber compounds. On the basis of two different types of modified clay, NR nanocomposites were prepared and cured by a conventional vulcanization system. A faster curing rate and lower torque values were found when the modification was done by quaternary ammonium compounds. The activation energy of the rubber curing process decreased with the incorporation of nanoclay. In addition, it was revealed that the quaternary ammonium compounds used as modifier in the clay show a plasticization effect. Additionally, X‐ray diffraction studies indicated, that the basal spacing of the clay minerals was increased in both cases after incorporation in the rubber matrix. The dynamic mechanical analysis using a strain sweep mode showed that the Payne effect decreases because of an improved dispersion of CB induced by the presence of nanoclay. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Improving the Tensile Properties of Natural Rubber Compounds Containing Ground Ethylene Propylene Diene Rubber Waste by Two-stage Processing

Microstructure and thermal properties of natural rubber compound with palm oil boilers ash for nanoparticle filler

Nowadays, the use of materials from renewable resources, such as agricultural waste and forest residues, has increased. In this work, industrial waste recovered from a recycled paper/cardboard company was mechanically refined to obtain ligno-cellulosic microfibers (LCMFs). The obtained LCMFs were well characterized and chemically modified in situ together with natural rubber through silanization. The effect of in situ silanizated LCMFs, by using (3-triethoxysilylpropyl) tetrasulfide (Si69) as a silane coupling agent, on natural rubber (NR) compound properties was studied. The NR compound with silanizated LCMFs at 2.5 phr of Si69 (NR MF Si2) increased NR stiffness significantly. For example, the 300% modulus of NR MF Si2 was around 9 units higher than that of NR. The physical–mechanical properties, crosslink density, curing behavior, infrared spectroscopy, and microscopy of the compounds were studied to confirm the in situ silanization of the microfibers and its reinforcement effect on the NR matrix. The storage modulus (E′) obtained from Dynamic Mechanical Analysis suggested that the silanizated samples presented an uneven crosslinking, but it was enough to stiffen the NR chains.

The rheometric properties of natural rubber compounds containing the compound tetrabutylammonium bis(N‐phenylsulfonyldithiocarbimate)zincate(II) as the accelerator are modulated by means of the response surface methodology (RSM), where the Face Centred Central Composite Design (FCCD) with three factors and three levels was chosen with the objective to obtain the relationship among the evaluated properties and factor levels. The factors in the experimental design are the amounts of both accelerator and sulfur and the vulcanization temperature. The compounds are evaluated as for the scorch time, optimum vulcanization time, and maximum torque. For each of these properties the Regression analysis, the pareto diagram and the fitted surface are obtained. Concerning the scorch and optimum vulcanization times, the most important factors are the vulcanization temperature and the amount of accelerator, respectively. Regarding the maximum torque, the most significant factors are the amounts of sulfur and accelerator. Considering the optimum vulcanization time a regression model with good accuracy could be obtained. The function desirability is used to obtain an optimum condition for an adequate cure system related to a set of desired intervals for the properties of interest.

The effects of partial replacement of oil palm wood flour by silica and silane coupling agent on properties of natural rubber compounds

Chrome tanning generates large amounts of leather wastes (LW) which have become a considerable environmental issue. In this work, particulate LW with and without urea treatment were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) under inert and oxidative atmospheres, and elemental analysis. Then treated LW (TLW) were incorporated in natural rubber compounds, seeking to find another way of disposal for this type of residue. The effect of TLW on rheometric properties of rubber composites during vulcanization was evaluated, including parameters related to leather particles dispersion in the matrix. It was found that TLW contained chromium and sulfur remaining from tanning, which could affect the properties of rubber compounds. During TGA analysis, oxidation of chromium into LW was increased as an effect of urea treatment. It was observed that TLW improved rubber processability during open two-roll mill mixing process. Rheometric characteristics allowed to identify a decreased TLW particle dispersion into the compound with the increase of its content in the composites. Stiffness of vulcanized composites and the kinetic of the vulcanization varied with TLW content, as an effect of the interaction of TLW with the rubber compound. Particulate leather wastes morphology could facilitate its mechanical interlocking with the polymeric matrix. The development of these type of composites will enable another profitable use for this type of waste.

Rubber products are usually fabricated by adding fillers to meet demands in multi-faceted industrial applications. Reinforcing fillers like carbon black and silica provide excellent mechanical strength and dimensional stability to a rubber vulcanizate. Nevertheless, further enhancement of rubber properties by introduction of novel materials has been an exciting area of research, especially with reference to the development of lightweight radial tire and tire for electrical vehicles. Recently, graphene has been extensively explored for such applications. It is a two-dimensional sheet of sp2-hybridized carbon and has exceptionally high specific surface area and high charge carrier mobility. Due to these unique properties, graphene is considered to be an ideal, nano-sized, multifunctional filler for rubber nanocomposites used in tire industries. However, despite its high mechanical strength, graphene has not yet been known to improve rubber properties significantly, possibly due to its poor dispersibility in a rubber matrix. In the present work, four different graphenic materials – Graphene oxide (GO), Reduced Graphene Oxide (RGO), two types of Graphene nano-platelets (GP1, GP2) – have been taken for complete evaluation in natural rubber (NR) and styrene butadiene rubber (SBR) compounds. Pristine graphene fillers at high loading did not impart significant properties as reported from our earlier studies, and hence, hybrid fillers were used in this study. We have examined four different aspects, i.e. the effect of nature and loading (1, 3, 5 and 7 phr) of graphene in a hybrid filler system, keeping the total filler (carbon black (N234) and graphene) constant at 45 phr, the effect of loading of carbon black keeping the graphene level constant at 5 phr and the effect of nature of rubber for a fixed hybrid filler (40 phr N234:5 phr Graphene) system. A reference compound with 45 phr of N234, without graphene, was also prepared. Graphene nano-platelets were found to exhibit superior mechanical and dynamic properties as compared to GO and RGO. Incorporation of GP1 and GP2 in a NR compound had enhanced 300% modulus, tensile strength, tear strength and rebound resilience. The abrasion resistance of these compounds was significantly superior to the GO- and RGO-based compounds. The enhancement in properties was attributed to a greater degree of exfoliation of graphene nano-platelets and dispersion of carbon black in the rubber matrix as well as their rough surface characteristics. The properties of NR compound containing the graphene were found to reach an optimum at a loading of 5 phr of graphene and 40 phr of carbon black. A decline in tear strength was observed with the increasing loading of graphene. At higher loading of carbon black (60 phr), the effect of graphene was not always significant. The enhancement in rubber properties was also observed in SBR-based formulation containing 40 phr of N234 and 5 phr of graphene nano-platelet. The extent of improvement in SBR-based compound was compared with the NR-based formulation. Graphene also reinforces silica filled compounds. A mechanism of reinforcement by graphene in the hybrid has been discussed in the light of the existing theories.

Carbon black‐filled natural rubber composites were prepared using various types of natural rubber: unmodified natural rubber, epoxidized natural rubber with two levels of epoxy groups at 25 and 50 mol % [epoxidized natural rubber (ENR)‐25 and ENR‐50], and maleated natural rubber. Two types of carbon black (HAF and ECF) with different structure and surface area were used. The functional groups present in natural rubber and carbon black were characterized by FTIR and 1H‐NMR. Furthermore, cure characteristics, mechanical, morphological, and electrical properties of composites and gum rubber compounds were investigated. It was found that the presence of polar functional groups in rubber molecules and the different structures of carbon black significantly affected the cure characteristics and mechanical properties. This is attributed to physical and chemical interactions between carbon black surfaces and rubber molecules. It was also found that natural rubber filled with ECF showed the highest Young's modulus and hardness, which is due to the high‐surface area and structure of the ECF causing an increase in the degree of entanglement between rubber chains and carbon black particles. Frequency dependency of the dielectric constant, loss tangent, and AC conductivity was also investigated. An increase in dielectric constant, loss tangent, and AC conductivity was observed in the ENR/ECF composites. High‐carbon black loading level caused network formation of these conductive particles, increasing the AC conductivity of the composites. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers

This study investigates the efficiency of already developed surface‐modified carbon black (CB), both independently and in conjunction with nano‐silica, as a hybrid filler, to the properties of natural rubber (NR) compounds. The modification process, followed by coupling agent treatment, enhanced cross‐link density and curing characteristics, though the inclusion of nano‐silica alone negatively affected curing due to its inherent polarity and tendency to agglomerate. The filled compounds with modified CB exhibited significant improvements in mechanical properties, notably tear resistance. Moreover, the combination of nano‐silica with modified CB yielded compounds with superior tear resistance, attributed to synergistic effects. CB surface modification exhibited varying effects on the glass transition temperature, with enhancements observed in tan δ at lower temperatures, indicating improved ice and wet grip potential. Also, it reduced rolling resistance after treatment with a coupling agent. While thermal stability remained consistent across the studied compounds, swelling resistance varies with filler type and ratio. Thermodynamic analysis confirmed the positive impact of CB surface modification on the elasticity and chain mobility of the investigated rubber compounds. It was concluded that the strategic selection of fillers and modification approaches were essential for achieving optimal results in the rubber compound's performance and application.

The effects of filler loading on the curing characteristics, swelling behavior, and mechanical properties of natural rubber compounds were studied using a conventional vulcanization system. Recycle rubber powder (RRP), carbon black (CB) (N550), and calcium carbonate (CaCO3) were used as fillers and the loading range was from 0 to 50 phr. Results show that the scorch time, t 2, and cure time, t 90, decrease with increase in filler loading. At a similar filler loading, RRP shows shortest t 2 and t 90 followed by CB and calcium carbonate. The tensile strength, tensile modulus, and hardness increase with increase in CB loading, whereas elongation at break, resilience, and swelling properties show opposite trend. For RRP and calcium carbonate filled natural rubber compounds, the tensile strength increases up to 10 phr and starts to deteriorate at higher filler loading. The other properties such as tensile modulus, hardness, elongation at break, resilience, and swelling percentage show a small change (increase or decrease) with increase in RRP and calcium carbonate loading in natural rubber compounds. Overall results indicate that RRP can be used as a cheapener to replace calcium carbonate in natural rubber compounds where improved mechanical properties are not critical.