Thermal Stability Of Natural Rubber Research Articles

Hydrothermal Liquefaction of Scrap Tires: Optimization of Reaction Conditions and Recovery of High Value-Added Products

Response surface method (RSM) was proposed to investigate the conversion of scrap tire via hydrothermal treatment. Temperature was the dominant factor in the process. The liquefaction rate increased sharply with temperature and exceeds 40 wt.% in the supercritical region ( >374.3°C). A maximum of more than 40 wt.% liquefaction rate was obtained when the tire was kept at 399°C for 60 min with the water/tire mass ratio of 10.8/1. Subsequently, the analysis of solid phase and liquid products at 360 and 400°C was carried out. The thermal stability of natural rubber in tire is significantly deteriorated after hydrothermal treatment. The hydrothermal process of rubber includes chain cleavage, particle hydrolysis, and carbon nanospheres formation, growth and agglomeration. The liquid products including carotenoids, ketones, and aromatic compounds, the ratio of which can be adjusted according to the temperature.

Effects of collagen fiber addition on the combustion and thermal stability of natural rubber

Collagen fiber (CF) and silane coupling agent-modified collagen fiber (MCF) were used as flame retardant filler for natural rubber (NR) modification. The combustion phenomena and properties of composites blended with different dosages of CF or MCF were compared to elucidate the flame retardant mechanism of the composites. The flame retardancy of NR can be enhanced effectively by increasing nitrogen content (the nitrogen content of CF is about 18%), creating air pockets, and structuring the flame retardant network in the composites. MCF failed to structure a flame retardant network in the composite, indicating that its modification effects of MCF are weaker than those of CF. When CF dosage was 30 wt%, the composite can achieve the best flame retardancy, with limited oxygen index of 29.4% and without smoke and dripping during burning. This study demonstrated a new method for the flame retardant modification of NR.Graphical abstract

Kinetic of thermal degradation and thermal stability of natural rubber filled with titanium dioxide nanoparticles

This article deals with the kinetic of thermal degradation and thermal stability of natural rubber (NR) filled with titanium dioxide (TiO2) nanoparticles. Incorporation of TiO2 nanoparticles was done through a latex mixing method. This is to ensure the homogeneity of TiO2 nanoparticles throughout the NR matrix. Adding TiO2 nanoparticles results in shifting the decomposition temperature and char residue irrespective of the loadings of TiO2 nanoparticles. This is confirmed by the calculated kinetic parameters of the composites, indicating that higher energy is required to decompose the NR chains. Based on this analysis, a schematic model for thermal stability of TiO2 nanoparticles filled NR composites is proposed. POLYM. COMPOS., 40:3149–3155, 2019. © 2018 Society of Plastics Engineers

Exploring the comparative effect of silane coupling agents with different functional groups on the cure, mechanical and thermal properties of nano-alumina (Al2O3)-based natural rubber (NR) compounds

The surface of sol–gel-synthesized nano-alumina (Al2O3) was modified by three types of silane coupling agents with different specific functionalities, namely 3-aminopropyltriethoxysilane (APTES), triethoxy(octyl)silane (OCTEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT). The aim of the present study was to explore the effect of both unmodified and surface-modified nano-Al2O3 on the cure characteristics, mechanical properties, cross-link density and thermal stability of natural rubber (NR) nanocomposites. Results revealed that silane coupling agents were very effective to enhance maximum rheometric torque (R∞) and mechanical properties like modulus and tensile strength of nano-Al2O3-based NR nanocomposites. APTES offered higher value of cure rate index for NR compounds as compared to two other silane coupling agents. Among three silane coupling agents, TESPT provided highest improvement in the mechanical properties of NR/nano-Al2O3 composites. This might be explained by considering excellent improvement in the cross-link density of NR compounds in the presence of TESPT-treated nano-Al2O3. The incorporation of both TESPT- and OCTEOS-modified nano-Al2O3 into the NR matrix markedly improved the thermal stability of NR composites. Moreover, bi-functional silane TESPT not only increased the hydrophobicity of nano-Al2O3, but also improved the probability of sulfur cross-linking during cure process of NR compounds.

Mechanical Properties and Thermal Resistance of Natural Rubber Nanocomposite Reinforced with Quaternized Polyvinyl Alcohol/Silica Nanoclusters

Quaternized polyvinyl alcohol (QPVA) was synthesized and used as an intermedium to improve dispersion of silica (SiO2) in natural rubber (NR). QPVA/SiO2 nanoclusters reinforced NR nanocomposite was prepared by latex compounding via electrostatic interaction. TEM micrographs demonstrated QPVA/SiO2 nanoclusters were distributed around NR particles, forming shell-core structure. The mechanical properties and thermal ageing resistance of NR-QPVA/SiO2 were significantly improved compared with that of neat NR. The tensile strength of NR-QPVA/SiO2 film was improved by 60%, when the SiO2 content is 3%. SEM pictures indicated SiO2 was homogenous dispersed throughout NR matrix in the presence of QPVA. It also demonstrated that SiO2 could enhance thermal stability of NR, as NR-QPVA/SiO2 had best surface morphology after 72 hours thermal ageing at 100 °C. The thermal decomposition temperature and glass transition temperature of NR-QPVA/SiO2 film increased to a higher temperature due to strong polymer–filler interaction, which also indicated that all the ingredients were compatible and homogenous.

A comparison between polyethylene glycol (PEG) and polypropylene glycol (PPG) treatment on the properties of nano-titanium dioxide (TiO2) based natural rubber (NR) nanocomposites

The purpose of the present article is to modify the surface of nano-titanium dioxide (TiO2) and to investigate the reinforcing effect of both unmodified and surface-modified nano-titanium dioxide (TiO2) on the mechanical properties and thermal stability of natural rubber (NR) nanocomposites. Surface of nano-TiO2 is modified by polyethylene glycol (PEG) and polypropylene glycol (PPG). The effective surface modification of nano-TiO2 is evaluated by Fourier transform infrared (FTIR) spectra and field emission scanning electron microscopy (FESEM). The result notifies that the final properties of NR nanocomposites are dramatically improved in the presence of surface-modified nano-TiO2 in comparison to unmodified nano-TiO2. The excellent reinforcing capability of surface-modified nano-TiO2 is due to its better hydrophobicity and uniform dispersion within the NR matrix, as confirmed from morphological analysis. Furthermore, due to its small size PEG is better surface modifier for nano-TiO2 than PPG.

Enhancement of thermal stability of natural rubber based nano composite filled with boron nitride

The present work aims at enhancement of thermal stability of natural rubber. Natural rubber composite was prepared by two step method with boron nitride Nano particles as particulate fillers. Nano fluid was used in preparation of polymer composite. The boron nitride particles were added in various wt% proportions for the preparation of composite. The addition of the filler material into latex rubber matrix was found to be very effective through two step method. Filler particles interaction was observed through peaks in Fourier Transmission and infrared spectroscopy. Thermo gravimetric analysis observations reveal the thermal stability of composite.

Experimental and theoretical investigations of natural rubber (cis-1,4-polyisoprene) using Coloumb attenuating and Hartree–Fock theoretical methods

A systematic analysis of natural rubber (NR) has been carried out in the present investigation. The Fourier transform infrared (FTIR) spectrum of NR has been recorded in the range of 4000–400cm−1 and the vibrational frequencies of the fundamental modes have been precisely assigned. Density functional CAM-B3LYP/6-311++G(d,p) and Hartree–Fock HF/6-311++G(d,p) calculations were performed to obtain the optimized molecular structures, vibrational frequencies, natural bonding orbital (NBO) analysis and thermodynamic parameters. The computed static dipole moment (μtot) and first hyperpolarizability (β0) of the present molecule has been determined using the CAM/HF levels of theory. The optimized geometric parameters (bond lengths, bond angles and bond dihedrals) are found to be almost same at the B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) levels of theory. The vibrational frequencies obtained by CAM-B3LYP/6-311++G(d,p) method are much better than HF/6-311++G(d,p) when compared with the experimental FTIR values. From the NBO analysis, it was observed that C5 is more electronegative compared with other carbon atoms. The dielectric constant being an important parameter in deciding the insulation characteristic of the material was determined for NR in the X-band and K-band microwave frequency region by employing Roberts and Von Hippel's method. From Thermogravimetric analysis (TGA), the thermal stability of natural rubber has been discussed and important thermal transitions have been detected using Differential thermal analysis (DTA). In addition the hardness of the natural rubber was determined using shore ‘A’ durometer.

Influence of the Type of Alkylamine Organic Modifiers on Thermal Mechanical Behavior and other Related Properties of Natural Rubber/Clay Nanocomposites

Sodium-montmorillonite (Na-MMT) nanoclay was modified with different types of alkylamine organic modifier including primary and quaternary alkylamines. Influence types of alkylamine on properties of natural rubber/clay nanocomposites was investigated. It was found that organoclays caused improvement of mechanical properties of natural rubber, and accelerated vulcanization reaction with higher degree of crosslinking. In addition, organoclay modified with quaternary alkylamine showed significance cure reversion phenomenon which caused reduction of thermal stability. On the other hand, primary alkylamine modified nanoclay caused improvement of thermal stability of natural rubber. Moreover, stress relaxation was observed at the melting temperature of the modifying agent.

Effect of nanocrystalline cellulose on the curing characteristics and aging resistance properties of carbon black reinforced natural rubber

This work focused on the effect of nanocrystalline cellulose (NCC) on the curing characteristics, aging resistance and thermal stability of natural rubber (NR) reinforced with carbon black (CB). Sharing the same fillers loading of 45 parts per hundred rubber (phr), NR/NCC/CB composites with different NCC/CB ratios (i.e. 0/45, 5/40, 10/35, 15/30, 20/25 phr) were prepared and analyzed. Resorcinol and hexamethylene tetramine (RH), acting as the modifier in NR/NCC interface, was also discussed for its influence. The result showed that an relatively higher ratio of NCC/CB led to a lower torque, a shorter cure time (T90), a slightly longer scorch time (T10) and a bigger vulcanization rate constant (K). This tendency suggested that the existence of NCC accelerated the vulcanization process. Additionally, modified by RH, NR/NCC/CB compounds exhibited a short T10 and a elevated torque. And a moderate RH content would lower the Ea of vulcanization. A 10 phr substitute of CB by NCC can help to improve aging resistance in terms of mechanical properties. In a high temperature aging condition, composites with 10 phr NCC also performed the highest storage modulus (G′) among composites tested. A moderate NCC content contributed to the best retention of G′ after high temperature aging, so did the incorporation of RH. With the partial replacement of CB by NCC, the temperature of 5% weight-lose had a slight drop and the apparent crosslink density showed a decrease. Thanks to the interaction of RH with both NR and NCC, composites showed an improvement in apparent crosslink density after modified by RH.

Effect of CMCS on the Thermal Stability of Natural Rubber

Effect of CMCS on the thermal stability of natural rubber(NR) was studied by means of TG-DTG,and the decomposition activation energy(Ea) was calculated through Flynn–Wall–Ozawa (FWO) method in the paper.The results showed that the Ea of NR mixed with CMCS was higher than that of ammonification NR,and the thermal stability of NR improved with increasing the addition level of CMCS.

EFFECT OF CELLULOSE NANOFIBERS ISOLATED FROM BAMBOO PULP RESIDUE ON VULCANIZED NATURAL RUBBER

Nanocomposites were prepared using two bioresources, viz., cellulose nanofibers (CNFs) extracted from bamboo paper-pulp waste as the reinforcing phase and natural rubber (NR) as the matrix phase. CNFs with diameters up to 50 nm were isolated from bamboo pulp waste, and nanocomposites with 5 and 10% CNFs were obtained via two-roll mill mixing of solid natural rubber with a master batch containing 20 wt% CNFs. The NR phase was cross-linked using sulphur vulcanization. The morphology studies showed that the dispersion of CNF in NR matrix was not optimal, and some aggregates were visible on the fracture surface. The tensile strength and modulus at 50% elongation increased for the nanocomposites with the addition of CNFs, accompanied by a moderate decrease in elongation at break. The storage modulus of the natural rubber significantly increased above its glass-rubber transition temperature upon nanofiber addition. The addition of CNFs also had a synergistic impact on the thermal stability of natural rubber. The susceptibility to organic solvents decreased significantly for the nanocomposites compared to crosslinked NR, which indicated restriction of polymer chain mobility in the vicinity of the nanosized CNFs in the NR matrix.

Characterization of electron beam irradiated natural rubber/modified starch composites

The effects of electron beam irradiation on thermal, mechanical and morphological properties of natural rubber/starch blends were investigated. The results of thermogravimetric analysis indicated that the thermal stability of natural rubber was improved by the addition of modified starch and by irradiation. On the other hand, thermal stability of irradiated natural rubber and natural rubber/unmodified starch blends is lower than that of pure natural rubber. The tensile strength of natural rubber (2.01MPa) was improved to 3.82MPa with the addition of 5phr unmodified starch. There was a further increase from 2.01MPa to 6.44MPa when 5phr modified starch was used.

Infrared Spectroscopy and Thermal Stability Studies of Natural Rubber-Barium Ferrite Composites

Natural rubber (NR)-barium ferrite (BaF) composites (RFCs) have been prepared. Structural features of the composites were characterized by Infrared spectroscopy and scanning electron microscope (SEM). Differential scanning calorimetry (DSC) analysis showed that there is small variation of glass transition temperature (≈ –1℃). The activation energy of glass transition was calculated by Kissinger method and has values between (53-110 kJ/mol). Thermodynamic parameters such as activated entropy, enthalpy and Gibbs free energy were calculated for glass transition also. Thermogravimetric analysis TG and its derivative DTG showed one stage thermal decomposition between 300℃-400℃ with weight loss between (19.47%-52.13%). Increasing barium ferrite loading will increase the thermal stability of natural rubber. The kinetic parameters such as activation energy, entropy, enthalpy and Gibbs free energy for composites in the decomposition region were calculated and analyzed using Coats-Redfern technique.

Thermal and Thermo-Oxidative Degradations of Deproteinized Natural Rubber and Natural Rubber

Deproteinization of natural rubber was achieved in the latex stage. The structure of deproteinized natural rubber (DPNR) was characterized by fourier transform infrared spectroscopy (FTIR). The thermo degradation of DPNR was studied by thermogravimetry analysis (TG) under air atmosphere and nitrogen atmosphere. The kinetic parameters apparent activation energies (Ea) of the thermal decomposition reaction been calculated from the TG curves using the method described by Broido. And the results were compared with the thermo degradation of natural rubber (NR) under the same conditions. The effect of proteins in natural rubber latex on thermal/ thermo-oxidative stability of NR was discussed. The results show that: the absorptions of the proteins in DPNR at 1546 ㎝-1, compared to NR, become significantly weaker, nearly disappear, which indicates most of proteins has been removed from NR. The thermo degradation of DPNR in nitrogen atmosphere is a one-step reaction. The initial degradation temperature (T0) 、the maximum degradation temperature（Tp） and the final degradation temperature（Tf）as well as the Ea of DPNR are higher than those of NR, which indicates that DPNR represents a better thermal stability than NR under nitrogen atmosphere. Thermo-oxidative degradation of DPNR and NR are two-step reaction. The characteristic temperatures (T0, Tp and Tf) of DPNR are lower than those of NR. The Ea during the First Step of Thermooxidative Degradation of DPNR are also lower than those of NR. These results prove that the thermo-oxidative stability of DPNR is worse than that of NR. Protein is the key role to the thermal stability of natural rubber.

Structure and Thermal Stability of Natural Rubber Reinforced with <i>In Situ</i> Generated Zinc Sorbate

In situ prepared zinc disorbate (ZDS) in natural rubber (NR) by the reaction of zinc oxide and sorbic acid was used to reinforce the dicumyl peroxide-cured NR vulcanizate. The changes in mechanical properties of NR vulcanizates after ageing and were determined and the structures and thermal stability of vulcanizates were also analyzed using scanning electron microscope and thermal gravimetric analyzer. The change ratios in tensile strength and elongation at break of NR vulcanizate with theoretic formation of ZDS of 21phr can be increased to -33 from -44 and -27 from -38 after ageing and the initial weight loss temperature of NR vulcanizate can be increased for about 7°C as compared to un-reinforced NR vulcanizate, indicating that the antioxidative behavior and thermal stability of NR can be improved significantly with theoretic formation of ZDS of 21phr.

Natural Rubber-Carbon Nanotube Composites through Latex Compounding

Natural rubber (NR)-based nanocomposites have been prepared with single-walled carbon nanotubes (SWNTs) through a latex stage mixing method. SWNTs were dispersed in water through ultrasonication and stabilized by the subsequent addition of a surfactant. The stabilized aqueous dispersion of SWNTs was mixed with NR latex and the effect of nanofiller on the flow properties of NR latex was investigated. Casting the compounded latex followed by curing gave good quality composite films with significantly improved mechanical properties. For example, the tensile strength and modulus of the composite film containing 2.0 phr (parts per hundred parts of rubber) SWNTs were, respectively, 56% and 63% higher in relation to pure NR. Electrical percolation threshold concentration of SWNTs in the NR matrix was found to be 1.5 phr. Thermogravimetric analysis indicated that the thermal stability of NR remains unaffected by the presence of SWNTs at low concentrations.

Thermal degradation and ageing behavior of microcomposites of natural rubber, carboxylated styrene butadiene rubber latices, and their blends

AbstractThe effect of microfillers on the thermal stability of natural rubber (NR), carboxylated styrene butadiene rubber (XSBR) latices, and their 70/30 NR/XSBR blend were studied using thermogravimetric method. Microcomposites of XSBR and their blend were found to be thermally more stable than unfilled samples. The activation energy needed for the degradation of polymer chain was calculated from Coats‐Redfern plot. Activation energy needed for the thermal degradation of filled samples was higher than unfilled system. It indicated the improved thermal stability of the filled samples. The ageing resistance of the micro‐filled samples was evaluated from the mechanical properties of aged samples. The thermal ageing was carried out by keeping the samples in hot air oven for 7 days at 70°C. The mechanical properties such as tensile strength, modulus at 300% elongation, and strain at break were computed. As compared to unfilled samples, micron‐sized fillers reinforced systems exhibited higher ageing resistance. Finally, an investigation was made on the influence of ion‐beam irradiation on microcomposites of NR, XSBR latices, and their 70/30 blend systems using 28Si8+ performed at 100 MeV. The surface changes of the samples after irradiation were analyzed using X‐ray photoelectron spectroscopy. The results of XPS measurements revealed that the host elements were redistributed without any change in binding energies of C1s, O1s, and Si2p. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Thermal stability and ageing properties of sulphur and gamma radiation vulcanized natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends

The thermal stability of natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends was studied by thermogravimetric methods. Ageing characteristics of these latex blends were studied by applying hot air oven thermal ageing for seven days at 70 °C. The mechanical properties of the aged samples were studied. Thermal degradation and ageing properties of these individual latices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As the XSBR content in the blends increased their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possesses higher thermal stability due to the higher thermal stability of carbon–carbon crosslinks. DTG curves were used for the determination of different stages involved in the degradation. Activation energy for degradation was determined from Coats–Redfern plot. The properties of aged samples were found to decrease due to chain depletion. However, the moduli of XSBR and NR/XSBR blends were found to increase owing to the formation of crosslinks upon ageing.

Radiation grafting of methyl methacrylate on radiation crosslinked natural rubber film

Grafting ofmethyl methacrylate (MMA) on radiation crosslinked natural rubber (NR) film has been investigated by mutual radiation grafting. The effect of experimental parameters like radiation dose, dose-rate, additives like acids and inorganic salts, solvents, monomer concentration, cross-linking density of the natural rubber film on the grafting extent has been studied.From the kinetic studies, a kinetic equation showing almost parabolic and linear dependence of grafting on concentration and dose rate, respectively, was deduced.Preliminary thermal stability studies of grafted films indicated that grafting of MMA does not enhance the thermal stability of NR.