Properties Of Natural Rubber Vulcanizates Research Articles

Cure characteristics and mechanical properties of natural rubber vulcanizates filled with untreated pyrolytic tire char

AbstractUntreated pyrolytic tire char was used in natural rubber (STR20) composites as single filler at loadings of 30–70 phr and co‐filler with carbon black (N330) at a total loading of 50 phr. The results were compared with rubbers filled with N330 and crumb rubber at 30 phr. The effects of fillers on cure characteristic, crosslink density, filler dispersion in natural rubber vulcanizates and their mechanical properties were investigated. The slight reversions were seen for the cure characteristics of 70 phr‐char‐filled and all co‐filler samples because the sulfur amount in the char together with the added sulfur could shift the vulcanization system from EV to SEV, whereas plateau cure curves were seen for the rest. While the highest tensile strength of char‐filled sample was obtained at 50 phr loading, whose tensile strength was about 88% of the N330 sample at 30 phr, 70‐phr‐char filled sample was superior in surface hardness, abrasion resistance and tear strength to N330 sample at 30 phr. For rubber with co‐fillers, the mechanical properties depended on the mass ratio of N330 to pyrolytic tire char. Therefore, it is possible to use untreated char as reinforcing filler for suitable applications according to their properties.

Performance of Moringa Oil as an Effective Bioplasticizer on Static and Dynamic Mechanical Properties of Natural Rubber Vulcanizates

Performance of Moringa Oil as an Effective Bioplasticizer on Static and Dynamic Mechanical Properties of Natural Rubber Vulcanizates

Physical Properties Investigations of Natural Rubber Composites Using Cetyltrimethylammonium Bromide (CTAB) as Modifier of Local Clay Filler

Improved absorption of rubber backbone on filler surfaces is necessary to enhance the physical properties of rubber vulcanizate. One of the ways to repair the surface of the filler is through modifying using surfactant. Hence, this study aims to compare the physical properties of natural rubber vulcanizates using clay filler and modified clay with cetyltrimethylammonium bromide (CTAB). The processes that were followed to achieve the objectives of this research were the design of rubber formulas, mastication and milling of rubber, and testing of the physical properties of rubber vulcanization. The clay characterization and its modification using FTIR and XRD were also carried out. Characterization using FTIR and XRD showed that there was indeed a clay modification with CTAB. Natural rubber compounds were also analyzed using SEM. The torque on the rheometer for modified clay with CTAB is 12.34 kg-cm higher than for original clay, which is 7.05 kg-cm. Elongation at break and tensile strength for vulcanizate using CTAB-modified clay filler is lower than that using original clay, with 300% modulus and hardness increase. Thus, clay modification using CTAB as a filler has a good effect on the curing characteristics and physical properties of natural rubber vulcanization compared to only using local clay as a filler.

Study of rheological characteristics and mechanical strength properties of natural rubber vulcanizates varying the type and content of carbon black

This paper presents a study about the influence of the size and content of two types of carbon black N220 and N550 with loading of 10–100 phr on the properties of the vulcanized natural rubber (NR).The mechanical characteristics such as the tensile strength, the tensile modulus, the elongation at break, the hardness, the abrasion resistance, and rheological properties of NR reinforced with carbon black were investigated. By analyzing the results of an N220 reinforced NR, the reinforcement gives improvement in tensile strengths when fillers are added up to 70 phr. However, and by referring of elongation at break, a fall of product elasticity is observed. . The increase of filler loading results a decrease in rheological properties; optimum cure time, scorch time, cure rate index (CRI). Furthermore, the increase of the filler loading leads to the increase in hardness for all the compounds. Compared the reinforcing ability of carbon black N220 scarcely inferior to carbon black N550.However, it seems that the rubber compound filled N220 or N550 gives comparable results on mechanical properties.

Preparation of Multifunctional Additive [MFA] from Castor Oil (CO) and Study of its Effects on the Physical Properties of Natural Rubber Vulcanizates

This experiment focuses on the synthesis of Multifunctional Additives (MFA) from Castor seed oil (CO) and pure Oleic acid (OA) respectively. These multifunctional additives (CO-MFA and OA-MFA) were investigated as potential substitutes for process oil, activator, co-activator, and accelerator in the formulation of a natural rubber vulcanizate. During processing, the castor seed oil was characterized for acid value (AV), free fatty acid (FFA) and saponification value (SV) and subsequently reacted with 1, 6-hexane diamine to obtain a mixture of salts termed castor oil-based multifunctional additives (CO-MFA), similarly, a pure oleic acid was also reacted with 1, 6-hexane diamine to obtain a pure salt termed oleic acid-based multifunctional additive (OA-MFA). These compounds were investigated as substitutes for process oil/stearic acid, process oil/stearic acid/zinc oxide, process oil/MBT, and process oil/stearic acid/zinc oxide/MBT in the formulation and compounding of natural rubber vulcanizate. The pre-mastication of the rubber and subsequent mixing with additives was carried out in a Banbury Internal Mixer at a rotor speed of 50 rpm for 7 mins while the vulcanization was achieved on a compression molding machine at a temperature of 140oC for 15 mins. The various vulcanizates samples were evaluated for tensile properties, compression set, abrasion resistance, and hardness. The use of castor seed oil-based multifunctional additives (CO-MFA) as a substitute for process oil/stearic acid/zinc oxide/MBT gave the highest value of tensile strength (12.24 MPa) as against the conventional rubber compound (4.21 MPa).

Effect of green synthesized zinc oxide nanoparticles as cure activator on the mechanical properties of natural rubber vulcanizate

Effect of green synthesized zinc oxide nanoparticles as cure activator on the mechanical properties of natural rubber vulcanizate

Effect of waste zinc oxide particles on properties of natural rubber vulcanizates

Effect of waste zinc oxide particles on properties of natural rubber vulcanizates

Effect of Chemically Modified Castor Seed (Ricinus Communis) Shell Powder on The Mechanical Properties of Natural Rubber Vulcanizate

Mechanical properties of natural rubber filled with modified castor seed shell powder for some engineering applications were studied. Castor seed shells were obtained and treated with 20% NaOH for 1h, washed and dried at 75oC and were pulverized and sieved to 75μm. Treated castor seed shell (TCSS) powder showed improved characteristics when compared to the untreated (UCSS) in terms of pH, bulk density, moisture content, lignin content, cellulose content, hemicelluloses content, thermal stability, SEM and FTIR spectra respectively. Natural rubber was compounded at varying filler loadings of 0, 10, 20, 30, 40 and 50phr on a two-roll mill. The cure characteristics of the compounded rubber were determined using a Mosanto Rheometer (model MDR 2000) and the result obtained were used for vulcanization in a hydraulic press. The cure characteristics, mechanical and morphological properties of the vulcanizates were analysed and compared with carbon black filled samples. The preliminary results showed that castor seed shell is hydrophilic which was chemically treated to decrease the hydrophilicity. The maximum and minimum torques increased with filler loadings. The result of the natural rubber filled vulcanizates showed improved mechanical properties such as; tensile strength, modulus, tear strength, hardness, abrasion resistance which increased with increased filler loadings while elongation at break, flex fatigue, compression set, impact strength and rebound resilience decreased with filler loadings. The TCSS filled vulcanizate showed superior abrasion resistance and compression set when compared with UCSS and CB filled. The sample morphology at 30phr revealed that TCSS was well dispersed due to strong interfacial adhesion between the filler and the matrices contributing to the improved mechanical properties investigated when compared to UCSS filled with poor interfacial interaction. The result reveal that TCSS is a reinforcing filler that can be used for the production of natural rubber-based products for some engineering applications.

Synthesis of nano zinc oxide and its effect on the cure characteristic and properties of natural rubber vulcanizates

In this work, nano ZnO was synthesized by a simple method using a polymeric substance as a dispersing agent. Characterization of the synthesized ZnO by XRD and SEM confirmed the ZnO was nanometric in size and had a wurtzite structure. The synthesized nano ZnO was used as an activator for natural rubber vulcanization. Different amount of ZnO, 1, 2 and 3 phr, was investigated in the rubber formulation and compared to convention ZnO at a typical amount (6 phr). The sample with 3 phr nano ZnO showed the lowest curing induction time with the highest (ML-MH) at all studied temperatures. Furthermore, the rubber sample with 3 phr ZnO achieved the best properties, i.e., crosslink density, rebound resilience, and hardness compared to the rubber sample with 6 phr conventional ZnO. Interestingly, the properties of rubber sample with 2 phr nano ZnO were probably equivalent and comparable to that of 6 phr conventional ZnO. Thus, it suggested that the synthesized nano ZnO could replace the convention ZnO as an activator for rubber vulcanization even at a lower amount.

The enhancement of cure and mechanical properties of natural rubber vulcanizates with waste Aquilaria crassna wood

Aquilaria crassna wood (WAC) waste was studied to reduce waste and use it as an alternative filler for rubber industry, by preparing masterbatches with varying WAC contents (0, 20, 40, and 60 phr). Dry mixing was also tested for comparison. The effects of WAC on curing characteristics, crosslink density, and mechanical, dynamic, and thermal properties were investigated. The results indicate that the masterbatch with 20 phr of WAC was near optimal. It showed a lower scorch time than control sample. That is, scorch time decreased from 1.4 min for Latex/WAC0 to 1.1 min for Latex/WAC20. This is because WAC contains some metals that activate vulcanization reactions. Thus WAC filler is beneficial in terms of reducing the cost of processing rubber to vulcanizates. In addition, the masterbatch with 20 phr of WAC showed high delta torque at 10.1 dN m, Mooney viscosity at 28.1 ± 0.5, crosslink density at 250 mol/m3, and hardness at 44 Shore A. It was also found that 20 phr of WAC gave a good filler dispersion and the highest glass transition temperature (T ɡ) at −41.2 °C, indicating strong filler-matrix interactions. Moreover, the masterbatch method exhibited overall better properties than the dry mixing method. This choice of processing method as well as compatibility of filler and matrix both affected the end results. Furthermore, the alternative filler use serves to reduce/recycle waste.

Effects of chemically treated and carbonized spear grass fibre on the curing and mechanical properties of natural rubber vulcanizates

Effects of chemically treated and carbonized spear grass fibre on the curing and mechanical properties of natural rubber vulcanizates were carried out. Natural rubber (NR) was filled with carbonized (at carbonization temperatures of 400°C, 600°C and 800°C respectively) and chemically treated (treatment with HCl and NaOH of 5% concentration) spear grass fillers respectively, at a filler loading of 30phr. The rubber compounding was carried out in a bambury mixer. The effect of carbonization temperature and chemical treatment of the filler on the mechanical properties (tensile strength, % elongation, hardness strength, abrasion resistance and compression set) and rheological properties (cure time, scorch time, maximum and minimum torque) were carried out on the samples. The results of the mechanical properties of carbonized spear grass fibre (C-SGF) filled vulcanizates show that the optimum carbonization temperature for an improved tensile strength, % elongation, hardness, abrasion and compression set was obtained at 400°C. NaOH treated fibre filled vulcanizates showed better mechanical properties; with the highest abrasion resistance of 67.65%, while untreated and acidified fibre filled vulcanizates showed poor mechanical properties. Acidified (HCl) uncarbonized spear grass fibre (U-SGF) filled vulcanizate had the highest compression set of 48% against C-SGF filled vulcanzates and carbon black filled vulcanizate, with carbon black filled vulcanizate having 47% as its compression set value. This reveals that at a carbonization temperature of 400°C, C-SGF appears to be a potential substitute filler for carbon black (CB).
 Keywords: Spear Grass Fibre, Natural Rubber, Chemical Treatments, Cure Characteristics, Mechanical Properties, Carbonization

Tensile and structural properties of natural rubber vulcanizates with different mastication times

Mastication reduced the molecular weight of natural rubber (NR). This would affect the tensile properties and strain-induced crystallization of the rubber vulcanizates due to the structural changes of the rubber molecules. In this study, influences of mastication time on tensile response, deformation-induced crystallization, and structural effects of crosslinked NR were investigated. The crystallization behavior and structural changes during stretching were studied by means of wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). Increased mastication time significantly affected modulus at specified strain and upturn point of strain-induced crystallization of the crosslinked samples while the tensile strength was influenced slightly by mastication. During stretching, degree of crystallinity at given strain was found to decrease with increasing mastication time, while the crystallite size was reduced. Moreover, the size of crosslinked network structures induced by crosslinking also decreased slightly with increasing mastication time, as suggested by SAXS measurement.

Comparative Studies on Solubility and Thermo Dynamics Properties of Natural Rubber Filled with CB/CPKS and CB/APKS Fillers

In this research, the comparative studies on solubility and thermodynamics properties of natural rubber vulcanizates filled with blends of activated palm kernel shell and carbonized palm kernel shell has been investigated. Palm Kernel Shell (PKS) was locally sourced. washed and sun dried to remove accompanying and moisture. The PKS was then pulverized to particle size, carbonized at 600°C for one hour (1hr) using Carbolite furnaces and chemically activated using 0.1M H₃PO₄ and 0.1M KOH solutions. The NR-filler loading concentrations of CB/APKS and CB/CPKS were compounded using two-roll mill. The solubility was done using three different solvents of water, kerosene and petrol respectively. The solubility results obtained for CB/APKS and CB/CPKS has no significance difference as the temperature varies when immersed in water. The solubility values observed for CB/APKS and CB/CPKS ranges from 1.06g to 1.19g and 1.03g to 1.19g across the samples respectively. This shows that since the filler is an organic substance, it has little or no affinity for water. In the case of kerosene and petrol, both are organics and the filler is an organic substance which follows the statement ‘like-dissolves-like’ as the temperature increases, the absorption of kerosene is lower than that of petrol. The results recorded for kerosene across the samples of CB/APKS and CB/CPKS ranges from 1.18g to 4.37g and 2.02g to 4.79g while the results for petrol ranges from 2.25g to 4.92g and 2.51g to 4.88g respectively. This may be due to the fact that petrol is volatile and flammable compared to kerosene. The results of the activation energy were a reflection of the solvent’s permeability except for water which showed contrary results. The results of the activation energy obtained for the three solvents across CB/APKS and CB/CPKS were 5.55 KJ/mol for water, kerosene with 9.48 KJ/mol and petrol with 13.61 KJ/mol respectively. The results observed for water might be due to its nature as the universal solvent being entirely different from other solvents in terms of reactivity and anomalous property. This means polar solvents dissolve polar molecules while nonpolar solvents dissolve nonpolar molecules. This research shows that both CB/APKS and CB/CPKS possess great potential in rubber system.

Improvements in filler dispersion and tensile properties of natural rubber vulcanizates applying lauryl alcohol

Lauryl alcohol as one type of fatty alcohols was used to raise degree of silica filler dispersion and also tensile properties of silica filled natural rubber (NR) applying a system of semi efficient vulcanization. The NR was reinforced by silica filler with a settled loading at thirty phr. The lauryl alcohol was incorporated into the silica filled NR at one, two, three and four phr. The results showed that lauryl alcohol expanded the time to scorch but reduced time to cure and minimum torque. Lauryl alcohol also reduced tensile modulus but expanded elongation at break. The other properties such as crosslink density, torque difference and tensile strength were expanded up to three phr of lauryl alcohol. The swelling properties confirmed that three phr of lauryl alcohol was an optimum concentration where silica filled NR vulcanizate with three phr of lauryl alcohol showed the highest tensile strength. As a plasticizing agent, lauryl alcohol expanded tensile strength by increasing the degree of silica dispersion.

Study on the effect of modified and unmodified silica on the properties of natural rubber vulcanizates

AbstractIn the article, the effects of silica (silicon oxide) on some properties of natural rubber (NR) were studied. Silica used are unmodified (SiKBT) and modified with triethoxi silane propyl tetrasunfite (SiBT). It is shown SiBT increases vulcanization network density (VND), so it enhances strength and elastic properties of NR. In contrary, SiKBT decreases VND and reduces, but has almost no effect on strength of NR. Silica, both modified and unmodified, are assumed to improve network regularity of NR that change thermal degradation behavior of materials and keep the strength of NR‐SiKBT compound unchanged.

End-Use Properties of Pineapple Leaf Fibre Filled Natural Rubber

The effects of incorporating pineapple leaf fibre (PLF) as a filler on the end-end properties of natural rubber vulcanizates were studied at different filler contents and particle sizes. The pineapple leaf fibre was used within filler contents, 0 to 40 phr at the following filler particle sizes, 75, 150 and 300 μm. The PLF was characterized for filler properties while carbon black (N330) served as the reference filler. The natural rubber vulcanizates were compounded on a two-roll mill. Results showed that the abrasion resistance of filled natural rubber vulcanizates was generally higher than that of the unfilled natural rubber vulcanizate at filler content, 5 phr, and for PLF (150 and 300 μm) and carbon black filled natural rubber vulcanizates, the abrasion resistance decreased within filler content, 5 to 20 phr after which it increased with filler content. CB exhibited better abrasion resistance in the vulcanizates than PLF at filler contents greater than 20 phr. The hardness of filled natural rubber vulccanizates was generally greater than that of unfilled vulcanizate and increased with increases in filler particle size at filler contents, 10 and 20 phr. The specific gravity of the rubber vulcanizates increased gradually with the increase in filler content at filler content greater than 5 phr, and increased with increases in filler particle size at any filler content considered. The swelling index of filled natural rubber vulcanizates in toluene generally decreased with increasing filler particle size at filler contents, 5, 10 and 40 phr whereas the swelling index for PLF (150 μm) filled natural rubber decreased with increases in filler content. CB filled vulcanizates absorbed the highest amount of toluene (2.5%) in the vulcanizates at filler content, 40 phr. PLF (150 and 300 μm) generally gave optimum performances in the end-use properties of the rubber vulcanizates determined within filler contents, 30 and 40 phr. The incorporation of pineapple leaf fibre into natural rubber was found to improve the end-use properties of natural rubber vulcanizates and therefore, has potential in the formulation of natural rubber products.

Cure Characteristics and Mechanical Properties of Pineapple Leaf Fibre Filled Natural Rubber

The cure characteristics and mechanical properties of natural rubber filled with pineapple leaf fibre (PLF) were studied at different filler contents and particle sizes. The PLF was characterized for filler properties while carbon black (N330) served as the reference filler. The natural rubber vulcanizates were compounded on a two-roll mill. Results showed that PLF (300 μm) filled natural rubber vulcanizates exhibited the highest maximum torque (Tmax) (47.04 lb-in) at filler content, 10 phr among the filler particle sizes investigated. The minimum torque (Tmin) of the vulcanizates generally increased with the increase in filler contents and particle sizes. The scorch times of the rubber vulcanizates did not vary with fibre content while the cure times of PLF (300 μm) filled rubber vulcanizates decreased with filler content. The tensile strength (TS) of PLF (150 μm) filled natural rubber vulcanizates generally increased with the increase in filler content whereas the tensile modulus of the rubber vulcanizates decreased steadily with increasing filler particle size at filler contents, 5 and 30 phr. The elongation at break (EB) of the rubber vulcanizates exhibited no general order of variation with filler content and particle size, and was generally greater than that of unfilled natural rubber. The flexural strength of the rubber vulcanizates increased with increasing filler particle size at filler contents, 20 and 40 phr. The addition of PLF and carbon black improved the compression strength of the rubber vulcanizates, and which for PLF (300 μm) and CB fillers generally increased with the increase in filler content. The study has demonstrated the enhancement of properties of natural rubber vulcanizates on incorporation of PLF into natural rubber, however, the property enhancements obtained were less than those recorded for CB filled natural rubber vulcanizates.

Influence of Pyrolytic Carbon Black Prepared from Waste Tires on Mechanical Properties of Natural Rubber Vulcanizates

This research aimed to investigate the possibility of pyrolytic carbon black (PCB) used as filler in natural rubber (NR) and its effect on Mooney viscosity, cure characteristics and mechanical properties compared with commercial carbon black (N774). The results revealed that Mooney viscosity, stiffness and heat build-up tended to increase with increasing both PCB and N774 loading, whereas elongation at break decreased. However, the maximum tensile and tear strengths appeared at the optimum filler loading for both PCB and N774. At similar filler content, PCB-filled NR compounds have higher cure time, heat build-up and thermal resistance. Nevertheless, they exhibited lower Mooney viscosity and mechanical properties compared to N774-filled NR. Finally, it can be concluded that PCB could be utilized as filler in NR compound to act as semi-reinforcing filler and was classified as a filler to reduce costs.

Role of eco-friendly Molasses carbon powder as a filler in natural rubber Vulcanizates

Molasses is an inexpensive by-product of the refining of sugarcane into sugar. To add value of the molasses as a consequence of such advantages as an efficient low cost carbon source, viscous molasses was converted to powder form under the proper condition. Molasses carbon powder (MCP), mainly consisting of carbon, was finally obtained. Since the MCP was rich in carbon as well as carbon black reinforcing filler in rubber, a feasibility study was carried out on the utilization of MCP as a filler in natural rubber (NR). The present work aims to investigate the role of MCP on properties of NR vulcanizates. MCP was incorporated in to the NR with various loadings of 0, 10, 20 and 30 phr (parts per hundred of rubber) and also compared with carbon black (CB). NR filled with carbon fillers, MCP and CB, were examined in the term of cure characteristics, tensile properties, tear strength, abrasion resistance, hardness and swelling resistance. From the results, it was observed that the cure times decreased with the incorporation of MCP whereas torque difference, tensile strength, tensile modulus, hardness and swelling resistance increased. Additionally, results revealed that the vulcanizates containing 10 phr of MCP provided optimum properties and can also be comparable with the commercial carbon black for use as filler for the NR vulcanizates.

Dynamic Mechanical and Morphological Properties of Natural Rubber Vulcanizates Containing Fillers

In order to examine correlation between silane coupling agent and activator which affects the physical properties of silica filled natural rubber compound, such as heat buildup, rebound property, dynamic mechanical and morphological properties were measured. With incorporation of silane coupling agent, tanδ at 0℃ was increased and at 60℃ was decreased, which resulted in improving of wet grip and rolling resistance. When silane coupling agent which is corresponding to 8~10% of silica was used, most favorable heat build up and tanδ was obtained. And also when activator was used, dispersibility of silica was improved as a result of reduction of reaggregation of silica.