Influence of Liquid Isoprene Rubber on Strain Softening of Carbon Black Filled Isoprene Rubber Nanocomposites

The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations. Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed. Herein carbon black(CB) filled isoprene rubber(IR)/liquid isoprene rubber(LR) blend nanocomposites with similar crosslink density(ν_e) are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated. The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes.Meanwhile, tuning ν_e and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances. The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.     

Preparation of high damping elastomer with broad temperature and frequency ranges based on ternary rubber blends

Based on the blends of chlorinated butyl rubber (CIIR), nitrile butadiene rubber (NBR) and chloroprene rubber (CR), a kind of high damping elastomer with broad temperature and frequency ranges is prepared. CIIR/NBR binary blend is prepared to take advantage of the immiscibility and the large difference in cross‐link density of the different phases caused by the curatives and accelerators migration. The dynamic mechanical analysis reveals that the binary blend was immiscible and its loss factor (tanδ) versus temperature curves show two separated and expanded loss peaks when compared with those of pure cured CIIR and NBR. In order to improve its damping properties at room temperature, the third component CR with the polarity between CIIR and NBR was blended into the binary blend. The resulted CIIR/NBR/CR ternary blend has gained effective damping properties (tanδ > 0.3) in the temperature range of ?86.4 to 74.6°C and the frequency range of 10^?2 to more than 10⁹ Hz. Other effects on the damping properties of the ternary rubber were also studied. Copyright © 2013 John Wiley & Sons, Ltd.     

Properties of Natural Rubber/Recycled Chloroprene Rubber Blend: Effects of Blend Ratio and Matrix

The present study investigated the effects of two types of natural rubber and different blend ratios on the cure, tensile properties and morphology of natural rubber/recycled chloroprene rubber blends. The blends of natural rubber/recycled chloroprene rubber were prepared by using laboratory two-roll mill. The result showed that the cure time prolonged with the addition of recycled chloroprene rubber (rCR). Comparability, natural rubber/recycled chloroprene rubber (SMR L/rCR) blendcured rapidly than epoxidized natural rubber/recycled chloroprene rubber (ENR 50/rCR) blend. The addition of rCRalso caused a decrement in the tensile strength and elongation at break for both rubber blends. The SMR L/rCR blendsshowed higher tensile strength and elongation at break compared to those of ENR 50/rCR blends at any blend ratios.     

The role of thiophosphoryl disulfide on the co‐cure of CR‐EPDM blends

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS) has been used as a coupling cum curing agent for the compatibilization of blends of ethylene propylene diene monomer rubber (EPDM) with chloroprene rubber (CR). Electrical and mechanical properties of the blend vulcanizates have been studied to find the efficiency of the vulcanizing cum coupling activity of DIPDIS. The study reveals that CR in the presence of DIPDIS greatly improves the physical properties of EPDM. It is noted that the physical properties of the vulcanizates obtained from CR‐EPDM blend depend upon CR:EPDM ratio. The scanning electron microscopy (SEM) study reveals that it is possible to form a coherent blend of CR and EPDM in the presence of DIPDIS. Copyright © 2004 John Wiley & Sons, Ltd.     

Dynamic vulcanization of reclaimed tire rubber and high density polyethylene blends

Dynamic vulcanization of reclaimed tire rubber (RTR) and HDPE blends was reported. The effect of blend ratio, methods of vulcanization, i.e. sulphur, peroxide, and mixed system and the addition of compatibilizer on mechanical, thermal, and rheological properties were investigated. The blend with highest impact strength was obtained from 50/50 RTR/HDPE vulcanized by sulphur. Increasing the RTR content to more than 50% resulted in a decrease in the impact strength of blend, most likely due to the increasing carbon black content. For tensile strength, the presence of rubber and carbon black, however, unavoidably caused a drop in this property. Comparing among three methods of vulcanization, sulphur system seems to be the most effective method. Results from solvent swelling ratio, glass transition temperatures and viscosity indicated that the sulphur vulcanization created the highest degree of cross-link and filler-matrix interaction in the RTR/HDPE blend. Morphology of the blends was also assessed by scanning electron microscopy (SEM).     

Radiation Vulcanization of Nitrile Butadiene Rubber/Butadiene Rubber Blends

Blends of nitrile butadiene rubber (NBR) with butadiene rubber (BR) with varying ratios have been prepared. Vulcanization of prepared blends has been induced by ionizing radiation of gamma rays with varying dose up to 250 kGy. Physical properties, namely soluble fraction and swelling number have been followed up using toluene as a solvent. Mechanical properties, namely tensile strength, tensile modulus at 100% elongation and elongation at break have been followed up as a function of irradiation dose, as well as blend composition. Thermal stability of blends was studied by TGA. The result indicated that the addition of NBR has improved the properties of NBR/BR blends. Also, NBR/BR blend is thermally stable than BR alone.     

The Coagulation Impact of 50% Epoxidised Natural Rubber Chain in Ethylene Carbonate-Plasticized Solid Electrolytes

In this research, thin, soft and flexible free standing films can be obtained from poly (methyl methacrylate) (PMMA)/50% epoxidised natural rubber (ENR 50)/lithium triflate (LiCF₃SO₃) blends. However, phase separation is observed on the surface of the films which indicates that the blending is not homogeneous. The blend became more homogeneous when ethylene carbonate (EC) plasticizer is introduced into the blend system. However, the anti-plasticization effect of EC on ENR 50 occurs at lower concentration of EC at which the rubber became coagulated due to immiscibility of the rubber with EC plasticizer during solution casting. These ENR 50 coagulates can be observed as large solid structures in the Field Emission Scanning Electron Microscope (FESEM) micrographs of the EC-plasticized rubber-based electrolytes. The presence of these coagulates, hinder the migration of lithium ions in the system and also trap the lithium ions within the coil. This in turn reduced the number of free lithium ions that contribute to the ionic conduction. As a result, the conductivity of the un-plasticized PMMA/ENR 50/LiCF₃SO₃ film dropped drastically by two orders of magnitude.     

Fracture toughness of nylon‐6 blends with maleated rubbers

The fracture toughness of blends of nylon‐6 with maleated ethylene–propylene rubber and maleated styrene/hydrogenated butadiene/styrene triblock copolymer was investigated with a single‐edge‐notched three‐point‐bending instrumented Dynatup test. The blends for which the rubber particle size was less than 0.7 μm fractured in a ductile manner over the whole range of ligament lengths, whereas the blends with particles larger than 0.7 μm showed a ductile‐to‐brittle transition with the ligament length. In this regime, ductile fracture was observed for specimens with short ligaments, whereas brittle fracture was seen for those with long ligaments. The ductile fracture behavior was analyzed with the essential‐work‐of‐fracture model, whereas linear elastic fracture mechanics techniques were used to analyze the brittle fracture behavior. The fact that the ductile fracture energy was larger for the blends with the styrene/hydrogenated butadiene/styrene triblock copolymer than for those with ethylene–propylene rubber was due to the larger dissipative energy density of the blends based on the styrene/hydrogenated butadiene/styrene triblock copolymer. Both the critical strain energy release rate (G_IC) and the plane‐strain critical stress intensity factor (K_IC) increased as the rubber particle size decreased for both blend systems. The G_IC and K_IC parameters had similar values, regardless of the rubber type, when the rubber particle size was fixed. The transition ligament length was near the size criterion for plane‐strain conditions for both blend systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1739–1758, 2004     

The abnormal behavior of polymers glass transition temperature increase and its mechanism

In terms of the classical theory in textbooks, the two components with phase separation in a binary polymer blend will, depending on their compatibility, have their respective Tg get closer or remain in their original values. According to the classical theory, the Tg of plastic component shall remain unchanged or move toward the lower Tg of rubber component in a rubber/plastic blend. However, ultra-fine full-vulcanized powdered rubber (UFPR) with a diameter of ca. 100 nm can simultaneously increase the toughness and the Tg of plastics, which is abnormal and is difficult to explain by classical theory. In this feature article, the abnormal behavior and its mechanism are discussed in detail.     

Determination of bound rubber composition of filled SBR/BR blend compounds by analysis of the unbound rubber composition and bound rubber content

Analytical method for determination of the bound rubber composition of a filled SBR/BR blend compound was developed using measurement of the bound rubber content and microstructural analysis of the unbound rubber composition. Various filled SBR/BR blend compounds with different blend ratios were prepared using SBRs with different microstructures. This method included measurement of the bound rubber content, extraction of the unbound rubber, microstructural analysis of the unbound rubber composition, and process for determination of the bound rubber composition. Composition of the unbound rubber was analyzed using liquid proton nuclear magnetic resonance spectroscopy (H-NMR) and transmission Fourier transform infrared spectroscopy (FTIR). It was found that the analytical results using H-NMR had less experimental errors than those using transmission-FTIR. The raw SBR/BR blends were also analyzed in order to evaluate level of the experimental errors. Average SBR/BR ratios of the unbound rubbers were obtained using the 1,2- and 1,4-unit contents determined by the H-NMR analysis. The bound rubber compositions were obtained using the bound rubber contents and the average unbound rubber compositions. It was found that most of the bound rubbers had higher SBR ratios than the formulation value.     

Evaluation of the properties of some nitrile–butadiene rubber/polychloroprene mixes and vulcanizates

Nitrile–butadiene rubber (NBR) has been blended with polychloroprene (CR) in a weight ratio of 1:1. The vulcanizing systems in the blend formulations were varied to obtain non crosslinked CR embedded in vulcanized NBR and non crosslinked NBR embedded in vulcanized CR. The effects of these two different phases on the rheological and mechanical characteristics were evaluated. In addition, the dynamic compliance of the blends was measured over wide ranges of frequency and temperature. It has been found that the mechanical and rheological properties of the vulcanized blends depend on the type of vulcanizing system, its concentration and the presence of reinforcing filler. The mechanical properties of the blend containing N‐cyclohexyl‐2‐benzthiazyl sulphenamide/S as vulcanizing system suitable for NBR are higher than those of the blend containing non‐sulfur vulcanizing system (Zno/Mgo and ethylene thiourea) suitable for CR. Both types of rubber (CR and NBR) in the blend are incompatible as two glass transition temperatures have been observed. Copyright © 2000 John Wiley & Sons, Ltd.     

Improving properties of natural rubber/polyamide 12 blends through grafting of diacetone acrylamide functional group

The aim of the present study was to improve the compatibility in blends of natural rubber (NR) and polyamide 12 (PA12) by grafting NR with hydrophilic monomer, diacetone acrylamide (DAAM), via seeded emulsion polymerization. The increase in polarity of NR after grafting modification was confirmed by a considerable increase in the polar component of its surface energy. Blends of graft copolymers of NR and poly(diacetone acrylamide) prepared using 10 wt% of DAAM (NR‐g‐PDAAM10) and PA12 were prepared at a 60/40 blend ratio (wt%) using simple blend and dynamic vulcanization techniques. The mechanical and rheological properties of the resulting blends were subsequently investigated and compared with those of the corresponding blends based on unmodified NR. The results show that dynamic vulcanization led to a significant increase in both mechanical and rheological properties of the blends. It was also observed that the dynamically cured NR‐g‐PDAAM10/PA12 blend had smaller particle size of vulcanized rubber dispersed in the PA12 matrix than observed for the dynamically cured NR/PA12 blend. This is due to the compatibilizing effect of DAAM groups present in NR‐g‐PDAAM10 molecule, which decreases the interfacial tension between the two polymeric phases. Therefore, it can be stated that the interfacial adhesion between NR and PA12 was improved by the presence of DAAM groups in NR molecule. This was reflected in the higher tensile properties observed in the dynamically cured NR‐g‐PDAAM10/PA12 blend. Copyright © 2017 John Wiley & Sons, Ltd.     

Evaluation of air permeability characteristics on the hybridization of carbon black with graphene nanoplatelets in bromobutyl rubber/epoxidized natural rubber composites for inner‐liner applications

Nanotechnology has been explored recently as a means of enhancing the properties of conventional elastomers for engineering applications. In the current study, the effect of nanofillers on air impermeability properties of Brominated isobutylene‐isoprene rubber (BIIR)/Epoxidized natural rubber (ENR) blend has analyzed for automotive applications. The ENR chosen is ENR 25 and ENR 50 (25 and 50% epoxidation) and prepared the blends in a ratio of 75:25 (BIIR:ENR), and from both blend based composites, a part of carbon black replaced with graphene nanoplatelets (GNP). The physical and thermal properties were compared for both binary blend nanocomposites to study the level of exfoliation and reinforcement behavior of GNP. Morphology studies were employed to reveal the level of interaction between GNP and carbon black in both blends. The influence of epoxidation in the formation of nanostructures in both blends have been evaluated, and the effect of nanostructures on air permeability properties was studied. The air impermeability of BIIR‐ENR 50 nanocomposites were improved with increasing platelet concentration, a 30% improvement in air permeability is obtained for BIIR‐ENR 50 composites over BIIR ‐ENR 25.     

Compatibilization of PA6/rubber blends by using an oxazoline functionalized rubber

The compatibilization of blends of polyamide 6 with a nitrile butadiene rubber has been investigated. The procedure consists of two steps: modification of the nitrile groups of the rubber into oxazoline in the melt through condensation of ethanolamine with formation of a molecule of ammonia, followed by use of the modified rubber as a compatibilizing precursor which is melt mixed with the polyamide to produce the compatibilized blend. The modification reaction has been detected by NMR analysis and a rheological, mechanical and thermomechanical characterization has been carried out on the all the blends. The results indicate that the modification reaction occurs but the conversion of nitrile into oxazoline is relatively low. Use of the modified rubber in the preparation of binary polyamide/rubber blends, leads to an increase in viscosity, which is typical of compatibilized systems, and to enhanced tensile, impact and thermomechanical properties. These phenomena can be explained by the formation of in situ rubber/polyamide copolymers that act as compatibilizers, due to the reaction between oxazoline and the end groups of the polyamide. The presence of residual low molecular compounds, from the modification or from the purification of the rubber worsens all of the properties and inhibits the compatibilizing effect of the modified rubber.     

硅橡胶/氟橡胶并用胶的制备及力学性能

硅橡胶和氟橡胶作为国防、航天等重要领域的耐热材料一直被人们青睐,但其有着各自地优缺点且价格昂贵,本文尝试将这两种橡胶制成并用胶以解决氟橡胶不耐低温和加工性差的问题,以期增大其使用温度范围。采用机械共混法制备硅橡胶/氟橡胶并用胶,研究了硅橡胶和氟橡胶的混炼工艺、并用比、共硫化体系和硫化条件对并用胶力学性能的影响。结果表明,当硅橡胶/氟橡胶的质量比为10∶90,共硫化体系为3~#硫化剂/过氧化二异丙苯(DCP),一段硫化温度为170℃、硫化压力为10MPa、硫化时间为30min,二段硫化温度为200℃、硫化时间为6h时,并用胶的力学性能达到最好。     

Studies on the properties of EPDM–CSE blend containing HTPB for case‐bonded solid rocket motor insulation

Elastomeric blends based on ethylene propylene diene (EPDM) rubber as a primary polymer have been investigated for the thermal insulation of case‐bonded solid rocket motors (SRMs) cast with composite propellant containing hydroxy terminated polybutadiene (HTPB) as a polymeric binder. EPDM rubber found as an attractive candidate for the thermal insulation of case‐bonded SRM due to the advantages such as low specific gravity, improved ageing properties, and longer shelf life. In spite of these advantages, EPDM, a non‐polar rubber, lacks sufficient bonding with the propellant matrix. Bonding properties are found to improve when EPDM is blended with other polar rubbers like polychloroprene, chlorosulphonated polyethylene (CSE), etc. This type of polar polymer when blended with EPDM rubber enhances the insulator‐to‐propellant interface bonding. In the present work, an attempt has been made to study the properties of EPDM–CSE based insulator by incorporating HTPB, a polar polymer as well as a polymeric binder, as an additive to the EPDM–CSE blend by varying the HTPB concentration. Blends prepared were cured and characterized for rheological, mechanical, interface, and thermal properties to study the effect of HTPB addition. This paper reports the preliminary investigation of the properties of EPDM–CSE blend containing HTPB, as a novel and futuristic elastomeric insulation for case‐bonded SRM containing HTPB as propellant binder. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of non‐rubber components on the mechanical properties of natural rubber

Effect of the nanomatrix structure on mechanical properties of natural rubber was investigated in relation to the strain‐induced crystallization. Structure of natural rubber was analyzed through Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction measurement and transmission electron microscopy. The nanomatrix of the non‐rubber components was found to be inevitably formed in natural rubber, in which natural rubber particles linking to fatty acids were dispersed in the nanomatrix of the proteins and phospholipids. The nanomatrix disappeared after deproteinization of natural rubber with urea. Tensile strength and modulus of natural rubber were reduced by removal of the fatty acids and the proteins, which resulted in disappearance of the nanomatrix structure. The effect of fatty acids on the crystallization of natural rubber in small particles as a dispersoid was proved by tensile test of blend of natural rubber and styrene butadiene rubber. Copyright © 2016 John Wiley & Sons, Ltd.     

Kinetic investigation on the curing of ethylene methyl acrylate—Polydimethyl siloxane rubber blends by differential scanning calorimetry

Curing reactions of ethylene methyl acrylate (EMA) polydimethyl siloxane (PDMS) rubber blends have been investigated by differential scanning calorimetry (DSC) and by Rheometry. The curing exoterms obtained from DSC curves have been analysed to derive the kinetic parameters associated with the curing process. Crosslinking of EMA-PDMS rubber blends follow first order kinetics. The effect of blend ratio and peroxide concentration on the crosslinking characteristics of the blends have also been investigated. Department of Metallurgical Engineering     

Dichlorocarbene modified butadiene rubber (DCBR): Preparation,kinetic study,and its properties in natural rubber/DCBR blend vulcanizates

Dichlorocarbene modified butadiene rubber (DCBR) was prepared via the addition of the dichlorocarbene group in the presence of 2 phase transfer agents (cetyltrimethylammonium bromide and tetraethylammonium chloride). The effects of the reaction temperature and time, amount of dichlorocarbene precursor, and the type and amount of phase transfer agent on the chlorine content were investigated. The highest chlorine content (30%) in DCBR was obtained using 0.062 mol chloroform and 0.003 mol cetyltrimethylammonium bromide at room temperature for 19 hours although 27.9% was obtained after 12 hours. The kinetics of this dichlorocarbene modification was best described by the pseudo–first order rate law with 2 rate constants. For practical applications, the DCBR with chlorine contents of 10%, 20%, or 30% were blended with natural rubber (NR) and then vulcanized using the sulfur‐curing system. Although the polarity of DCBR was increased, a good compatibility between NR and DCBR still existed, resulting in improved mechanical properties. The oil resistance, flame retardant, and ozone resistance properties of the NR/DCBR blend vulcanizates were enhanced compared to those of a NR/butadiene rubber blend vulcanizate, which was related to the amount of chlorine incorporated into the DCBR.     

Mechanical and thermal properties of natural rubber-modified poly(lactic acid) compatibilized with telechelic liquid natural rubber

The effect of telechelic liquid natural rubber (TLNR) compatibilizer on natural rubber (NR) modified by melt-blending with poly(lactic acid) (PLA-NR) is studied using infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and notched Izod impact testing to determine the structural, thermal and mechanical properties. Scanning electron microscopy (SEM) is used to relate these properties to the morphology of the blends and fracture surface of the impact samples. Through this, it is revealed that the addition of LNR significantly improves the tensile and impact strength of PLA-NR, with the greatest compatibilization effect achieved with 6 wt% LNR. This improvement is confirmed through FTIR analysis to be due to a chemical interaction between LNR and PLA that improves the phase morphology of the blend.