A Comparative Study on Curing Characteristics,Mechanical Properties,Swelling Behavior,Thermal Stability,and Morphology of Feldspar and Silica in SMR L Vulcanizates

Abstract

Comparison studies on effects of feldspar and silica (Vulcasil C) as a filler in (SMR L grade natural rubber) vulcanizates on curing characteristics, mechanical properties, swelling behavior, thermal analysis, and morphology were examined. The incorporation of both fillers increases the scorch time, t ₂, and cure time, t ₉₀, of SMR L vulcanizates. At a similar filler loading, feldspar exhibited longer t ₂ and t ₉₀ but lower values of maximum torque, M_HR, and torque difference, M_HR–M_L than did silica-filled SMR L vulcanizates. For mechanical properties, both fillers were found to be effective in enhancing the tensile strength (up to 10 phr), tensile modulus, and hardness of the vulcanizates. However, feldspar-filled SMR L vulcanizates showed lower values of mechanical properties than did silica-filled SMR L vulcanizates. Swelling measurement indicates that swelling percentages of both fillers-filled SMR L vulcanizates decrease with increasing filler loading whereas silica shows a lower swelling percentage than feldspar-filled SMR L vulcanizates. Scanning electron microscopy (SEM) on fracture surface of tensile samples showed poor filler–matrix adhesion for both fillers with increasing filler loading in the vulcanizates. However, feldspar-filled SMR L vulcanizates showed poorer filler–matrix adhesion than did silica-filled SMR L vulcanizates. Thermogravimetric analysis (TGA) results indicate that the feldspar-filled SMR L vulcanizates have higher thermal stability than do silica-filled SMR L vulcanizates.     

The Fatigue Behaviour of Filled Epoxidized Natural Rubber Compounds

Abstract

The fatigue behaviour of white rice husk ash (WRHA) filled ENR-50 compounds was compared with those of silica (Vulcasil-S) and carbon black (N 330) filled compounds. The effect of WRHA loading on scorch time and Mooney viscosity was also studied. The incorporation of WRHA in ENR-50 compounds reduced the scorch time but increased the Mooney viscosity. The increment in filler loadings has resulted in the reduction of the fatigue fife. The fatigue behaviour of ENR-50 vulcanizates was observed to be strain dependent. At a similar filler loading, silica filled vulcanizates showed the highest fatigue life followed by those of WRHA and carbon black.     

The Effect of Accelerator/Sulphur Ratio on the Cure Time and Torque Maximum of Epoxidized Natural Rubber

Abstract

The cure time of accelerated sulphur vulcanization of Epoxidized Natural Rubber (ENR 25) was studied while one grade of unmodified natural rubber– Standard Malaysian Rubber Light (SMR L) was used as a control. Five accelerators, viz. 2-mercaptoben-zothiazole (MBT), tetramethylthiuram disulphide (TMTD), zinc dimethyldithiocarbamate (ZDMC), N-tert-butyl-2-benzothiazylsulphenamide (TBBS) and diphenylguanidine (DPG) were used in the study and the vulcanization systems used were conventional vulcanization (CV), semi-efficient vulcanization (semi-EV) and efficient vulcanization (EV). Monsanto Moving-Die Rheometer (MDR 2000) was used to determined the cure time in the temperature range of 100-180°C. The results indicate that cure time decreases exponentially with increasing temperature for the two rubbers studied. At a fixed curing temperature, ENR 25 shows shorter cure time compared to that of SMR L. This has been attributed to the activation of the double bond by the adjacent epoxide group in ENR 25. Studies of the effect of varying amounts of M Bata a fixed sulphur concentration show that cure time decreases as the accelerator concentration increases. ENR 25 shows higher torque maximum than SMR L. This observation can be related to the oxirane group which is bulky and thus accounts for increased glass; transition temperature with increase in the level of epoxidation. Of the vulcanization systems, CV shows the highest torque maximum followed by semi-EV and than EV. This trend can be attributed to the amount of active sulphurating agent which increases with increasing accelerator concentration. It was also found that the influence of accelerator/sulphur ratio becomes less significant as vulcanization temperature increases.     

Thermal Aging Properties and Molecular Transport of Solvents through Vulcanizates Prepared from Thioglycollic Acid Modified Epoxidized Low Molecular Weight Natural Rubber Blends Filled with Admixtures of Carbon Black and Carbonized Rubber Seed Shell

Physico-mechanical, aging, swelling, solubility, and permeability properties of blends of natural rubber and thioglycollic acid modified epoxidized low molecular weight natural rubber (TGA-ELMWNR) filled with admixtures of carbon black and carbonized rubber seed shell (CRSS) in ketones, alcohols, aldehydes, and petroleum fuels (petrol, kerosene, and diesel) were investigated as a function of different filler composition. The physico-mechanical properties were found reducing as the level of CRSS increases, but were within the accepted level for natural rubber compounds, showing that CRSS can find uses as fillers in materials of low tensile strength. The aging results of all the mixes were nearly of the same magnitude. The swelling and solubility results showed that ketones swell the vulcanizates more and faster than alcohols and than aldehydes. The sorption, diffusion, and permeability of the blends as determined by the gravimetric method confirm the better resistance of blends with higher ratio of carbon black. Petrol was found diffusing through the vulcanizates faster than kerosene and faster than diesel. Above all, replacement of carbon black with 15% carbonized rubber seed shell has not shown any serious deleterious effects on the vulcanizates.     

The Comparison Effects of Palm Oil Fatty Acid and Stearic Acid on Dynamic Properties,Curing Characteristics and Mechanical Properties of Carbon Black Filled Epoxidized Natural Rubber Compounds

Abstract

The effects of palm oil fatty acid and stearic acid on dynamic properties, curing characteristics and mechanical properties of carbon black filled epoxidized natural rubber compounds were studied. It was found that the scorch time, t ₂ and cure time, t ₉₀ increased with increasing both acids concentrations. For dynamic properties, the maximum elastic torque, increased with acids concentration, whereas the minimum elastic torque shows a decreasing trend. Results also indicate that the decrease in viscous torque and tan δ is significant with increasing acids concentration. For tensile modulus, hardness, maximum torque-minimum torque and swelling index, results indicate that both acids have some effects on crosslink density. However tensile and tear strength pass through a maximum as the concentration of both acid increased.     

Curing Characteristics,Mechanical and Morphological Properties of Kenaf Fibre/Halloysite Nanotubes Hybrid-Filled Natural Rubber Compounds

Natural rubber compounds were prepared with different kenaf/HNT ratio loading i.e., 30/0, 20/10, 15/15, 10/20, 0/30 (phr/phr). The compounds were cured at 150°C according to its t₉₀. Curing characteristic, tensile properties, fatigue, rubber-filler interaction and morphological properties of the compounds were tested. Curing characteristics show that scorch time and cure time increased with increasing of HNT ratio loading while minimum and maximum torque decreased. When HNT ratio loading was increased, tensile strength and elongation at break and fatigue life increased while tensile modulus decreased. Swelling measurement and morphological study showed that better rubber-filler interaction was obtained with higher HNT ratio loading.     

Curing Characteristics,Mechanical, Thermal,and Morphological Properties of Halloysite Nanotubes (HNTs)-Filled Natural Rubber Nanocomposites

Halloysite nanotubes (HNTs)-filled natural rubber (NR) nanocomposites with various filler loading were prepared by using a two-roll mill. The addition of HNTs increased the scorch time, cure time and maximum torque but reduced curing rate index. The tensile strength increased up to 20 phr of HNTs and then decreased. When HNTs loading increased, the elongations of break, swelling percentage and fatigue life were decreased while modulus at 100% and 300% elongation and thermal properties showed inversely. The dispersion of HNTs inside the NR matrix is shown from SEM images.     

The Effect of Ethylene Diamine Dilaurate and Silane Coupling Agent on Cure Characteristics,Mechanical, and Thermal Properties of Silica-Filled Natural Rubber Composites

The influence of a new coupling agent, ethylene diamine dilaurate (EDD) and a commercial silane coupling agent, (Si-69) on the cure characteristics, mechanical and morphological properties of silica-filled natural rubber (NR) composites was studied. The results show that scorch time and cure time decreased with an increase in both coupling agents' content, but maximum and minimum torques exhibit the opposite trend. The mechanical properties such as tensile strength and tensile modulus, M100 and M300, increased with increasing both coupling agents' content but at a similar coupling agent content, silica-filled natural rubber composites with Si-69 exhibit better tensile strength (more than 2 phr) and tensile modulus than does EDD. Elongation at break (Eb) of silica-filled natural rubber increased with increasing EDD content but Si-69 exhibits the opposite trend. Scanning electron microscopy (SEM) study of tensile fracture surfaces shows the better tensile strength of silica-filled natural rubber composites with Si-69 and EDD over control composites (without EDD or Si-69). Thermogravimetric analysis (TGA) results indicate that silica-filled NR composites with EDD have higher thermal stability than Si-69. Fourier transform infrared spectra (FTIR) provided an evidence of interaction between EDD and Si-69 with silica in NR composites.