Natural rubber composites with alumina of different particle sizes (28 nm nano particles, 200 nm active particles and > 1000 nm raw alumina) were prepared by the usual rubber processing technique. Epoxidized natural rubber (ENR) was used in the composites as compatibilizer. Cure characteristics and mechanical properties of all composites were analyzed. The values of minimum rheometric torque (ML), maximum rheometric torque (MH) and torque difference (MH – ML) increased. Maximum enhancement was observed for the nano-filled composites. It endorses the view that nano alumina reveals highest interaction with natural rubber in presence of ENR. Scorch time and optimum cure time values for nano-composites were highest among all types of composites. Vulcanization reaction for the sulfur curing system of the composites was found to follow first order rate kinetics. Specific rate constant decreased with decreasing particle size in composites. Crosslink densities of composite-vulcanizates showed increasing trend with decreasing particle size of alumina. Mechanical properties of the composite vulcanizates increased with decreasing particle size of alumina - nano composites exhibiting much higher mechanical strength. Results of oxidative resistance reveal that particle size of alumina in composite vulcanizates has a significant impact on aging behavior. 相似文献
Summary: For the first time, a series of Gd(AA)3/NR (natural rubber) composites for X‐ray shielding were prepared by an in situ reaction method. Occurrence of the in situ polymerization of Gd(AA)3 in composites during vulcanization of NR with peroxide greatly improves the dispersion level of the shielding phase by the remarkable reduction of Gd(AA)3 particle size and the formation of small sized poly‐Gd(AA)3 from the matrix. As expected and assumed, the X‐ray shielding properties of all composites apparently increase with the increase of the degree of dispersion of Gd(AA)3 in composites.
The ability of the composites to shield X‐ray radiation increases with an increase in Gd(AA)3 content and as the degree of in situ polymerization of Gd(AA)3 increases (i.e., as t tends towards t100). 相似文献
The effects of a silane coupling agent on curing characteristics and mechanical properties of bamboo fibre filled natural rubber composites were studied. Scorch time, t2 and cure time, t90 of the composites decrease with increasing filler loading and with the presence of a silane coupling agent, Si69. Mooney viscosity also increases with increasing filler loading but at a similar filler loading shows lower value with the presence of Si69. The mechanical properties of composites viz tensile strength, tear strength, hardness and tensile modulus were also improved with the addition of Si69. 相似文献
This research is conducted using palm kernel shell powder (PKS) as filler in natural rubber The effect of 3-aminopropyltrimethoxysilane as coupling agent on composites were studied at different palm kernel shell loading i.e, 0 5, 10, 15 and 20 phr The palm kernel shell was crushed and sieved to an average particle size of 5.53 μm The palm kernel shell filled natural rubber composites were prepared using laboratory size two roll mill The curing characteristics such as scorch time, cure time and maximum torque were obtained from rheometer The palm kernel shell powder filled natural rubber composites were cured at 150oC using hot press according to their cure time Curing characteristics, tensile properties, rubber-filler interaction and morphological properties of palm kernel shell powder filled natural rubber were studied Scorch time and cure time show reduction but tensile strength, elongation at break, modulus at 100% (M100) and modulus at 300% (M300) increased with the presence of 3-aminopropyltrimethyloxysilane Rubber-filler interaction studies showed that rubber filler interaction in natural rubber filled with palm kernel shell powder improved with incorporation of 3-aminopropyltrimethyoxysilane. 相似文献
Dielectric elastomers (DEs) require high drive voltages to obtain large actuated strain, which limits their application in the biological field. In this work, we enhanced the dielectric properties of natural rubber (NR) composites by using core–shell structured (CaCu3Ti4O12)x@(BaTiO3)(1−x) (CCTOx@BT(1−x)) high-dielectric particles with an buffer layer, and adjusted the thickness of the BT buffer layer by adjusting the addition of titanate during the preparation process, and then observed the relationship between the dielectric properties of NR composites and the thickness of the BT buffer layer. In addition, we modified the CCTO0.75@BT0.25 fillers surface with silane coupling agent KH560 to enhance the interfacial interaction between the inorganic fillers and polymeric matrix to obtain better dispersion and greater dielectric properties. As a result of the optimization of the CCTO0.75@BT0.25@KH560 structure, the actuated strain performance is greatly improved. The actuated strain of 5 per hundred rubber (phr) CCTO0.75@BT0.25@KH560/NR is 16.3% at 74.03 kV/mm, which is 6.52 times higher than the actuated strain obtained by NR (2.5%) at 50.28 kV/mm. This work presents a method to optimize the structure of core–shell fillers by modulating the buffer layer, and provides a new idea for further preparation of dielectric elastomer materials with large actuated strain at low voltage. 相似文献
The effect of carbon black(CB) and graphite(G) powders on the macroscopic and nano-scale free volume properties of silicone rubber based on poly(di-methylsiloxane)(PDMS) was studied through thermal and cyclic mechanical measurements, as well as with positron annihilation lifetime spectroscopy(PALS). The melting temperature of the composites(Tm) and the endothermic enthalpy of melting(?Hm) were estimated by differential scanning calorimetry(DSC). Tm and the degree of crystallinity(χc) of PDMS composites were found to decrease with increasing the CB content. This can be explained due to the increase in physical cross-linking which results in a decrease in the crystallite thickness. Besides, χc was found to be dependent on the filler type. Cyclic stress-strain behavior of PDMS loaded with different contents of filler has been studied. Mullins ratio(RM) was found to be dependent on the filler type and content. It was found that, RM increases with increasing the filler content due to the increase in physical cross-linking which results in a decrease in the size of free volume, as observed through a decrease of the o-Ps lifetime τ3 measured by PALS. Moreover, the hysteresis in PDMS-CB composites was more pronounced than in PDMS-G composites. Furthermore, a correlation was established between the free volume Vf and the mechanical properties of PDMS composites containing different fillers. A negative correlation was observed between Vf and RM. 相似文献
Novel biphasic structured in situ silica filled natural rubber composites were focused on their strain-induced crystallization (SIC) behavior from the viewpoint of morphology. The composites were prepared by in situ silica filling in natural rubber (NR) latex using a sol–gel reaction of tetraethoxysilane. Simultaneous time-resolved wide-angle X-ray diffraction and tensile measurements revealed a relationship between the characteristic morphology and tensile stress–strain properties of the composites associating with the SIC. Results showed stepwise SIC behaviors of NR-based composites for the first time. Pure rubber phases in the biphasic structure were found to afford highly oriented amorphous segments and oriented crystallites. The generated crystallites worked as reinforcing fillers together with the in situ silica to result in high tensile stresses of the composites. The observed characteristics are useful for understanding a role of filler network in the reinforcement of rubber. 相似文献
Eucommia ulmoides gum (EUG) is a renewable and sustainable polymer, which could be used as rubber or plastic by altering its crosslinking density while the complicated extracting process and nonpolar molecular chains limited its application. In this effort, a novel extraction method was introduced, which could simplify the extraction process of EUG. Then, the extracted EUG‐chloroform (CHCl3) solution was directly used to prepare epoxidized EUG (EEUG) with an epoxy degree of 40.0% to improve its polarity. The epoxidized natural EUG exhibiting both polar and nonpolar motives had an advantage in working as an interfacial compatibilizer for polymer composites, especially bio‐based composites due to its inherent biocompatibility. Accordingly, the role of EEUG in modifying the interface of styrene‐butadiene rubber (SBR)/silica composites were explored. The results showed that EEUG in SBR/silica composites acted not only as a compatibilizer but also as a constructure generating better mechanical properties than other compatibilizers, such as silane couplings, Si‐69 and KH‐550, and epoxidized natural rubber (ENR). The simplified extracting process and the epoxy modification of EUG would extend its application in rubber materials, medical materials, and biopolymer materials. 相似文献
Shape memory composites of trans‐1,4‐polyisoprene (TPI) and low‐density polyethylene (LDPE) with easily achievable transition temperatures were prepared by a simple physical blending method. Carbon nanotubes (CNTs) were introduced to improve the mechanical properties of the TPI/LDPE composites. The mechanical, cure, thermal, and shape memory properties of the TPI/LDPE/CNTs composites were investigated in this study. In these composites, the cross‐linked network generated in both the TPI and LDPE portions acted as a fixed domain, while the crystalline regions of the TPI and LDPE portions acted as a domain of reversible shape memory behavior. We found that CNTs acted as not only reinforced fillers but also nucleation agents, which improved the crystalline degree of the TPI and LDPE portions of the composites. Compared with the properties at the other CNT doses, the mechanical properties of the TPI/LDPE composites when the CNT dose was 1 phr were improved significantly, showing excellent shape memory properties (Rf = 97.85%, Rr = 95.70%). 相似文献
The aim of this study was to measure the thermal properties of foamed nano/macro filler–reinforced styrene maleic anhydride (SMA) composites. SMA (66%) as a polymer matrix (10% maleic anhydride content) and various fillers including wood flour, starch, α-cellulose, microcrystalline cellulose and cellulose nanofibrils as reinforcing agents (30%) and lubricant (4%) were used to manufacture the composites in a twin-screw extruder. According to the thermogravimetric analysis (TGA) results, thermal degradation of all the foamed composites was found to be lower than that of SMA composites. The storage modulus values were negatively affected with a second time foaming (reprocessing [recycling] the initially processed composites a second time), as were loss modulus and Tg. As a result, second-time-foamed composite modulus values were lower than those of the foamed composites. According to the melt flow index (MFI) results, viscosity of the SMA was found to increase with the addition of fillers. 相似文献
A series of polyurethanes (PU) prepolymers with NCO/OH ratios of 2.1:1 and 1.9:1 were prepared by reacting hydrogenated methylene di-p-phenyl diisocyanate (HMDI) with triol mixtures of TP740 (molecular weight 740) and TP1540 (molecular weight 1540). Stress–strain (S/S) and swelling equilibrium measurements were performed using thin-film samples prepared by moisture-curing the prepolymer at room temperature. The swollen PU networks gave an S/S curve which is fully described by rubber elasticity theory. The Mooney-Rivlin constant C1 (swollen) was found to increase directly while the molecular weight between crosslinks Mc decreases as the number of branches per cubic centimeter is increased. The solvent—polymer interaction parameter χ determined in benzene was 0.077 + 0.97vr, where vr is the volume fraction of rubber in the swollen network. The crosslink density v′, and Mc were calculated from the relations v′ = pNB and Mc = 0.667 B?1, where B denotes moles of branches per gram, and were found to be in good agreement with v′ and Mc established from S/S and swelling-equilibrium measurements. In calculating v′ and Mc, the water-PU crosslinking reaction at room temperature was assumed to occur mainly through the formation of a urea linkage. 相似文献