Novel in situ coordination copper sulfate/ acrylonitrile–butadiene rubber composite

A novel rubber composite of acrylonitrile–butadiene rubber (NBR) filled with anhydrous copper sulfate (CuSO₄) particles was investigated. Dynamic mechanical analysis, differential scanning calorimetry, X‐ray photoelectron spectroscopy, tensile testing, and an equilibrium swelling method were used for the characterization of this novel CuSO₄/NBR composite. The results indicated that the composite had wonderful mechanical properties, which profited from the in situ coordination crosslinking interactions between the nitrile groups (? CN) of NBR and solid CuSO₄ particles. Scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and transmission electron microscopy results showed that CuSO₄ particles played two roles, acting as both crosslink agents and reinforcing fillers in the matrix. The double actions of CuSO₄ gave the CuSO₄/NBR composites their excellent mechanical properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 571–576, 2007     

Investigation on crosslinking behaviors of NBR/PVC filled with anhydrous copper sulfate particles by dynamic mechanical analysis

Crosslinking behaviors of acrylonitrile butadiene rubber (NBR)/poly (vinyl chloride) (PVC) alloy, filled with anhydrous copper sulfate (CuSO₄) particles, were investigated for the first time by dynamic mechanical analysis (DMA) under hetero and isothermal modes, respectively. In the heterothermal testing, (NBR/PVC)/CuSO₄ compound showed two marked increases in the storage modulus (E′), corresponding to coordination crosslinking of NBR-CuSO₄ and self-crosslinking of NBR and PVC respectively. During the isothermal testing, a dramatic increase in E′ was found at the initial stage while that of original NBR/PVC alloy was not detected. The marked increase in E′ of (NBR/PVC)/CuSO₄ compound was mainly due to the crosslinking induced by coordination between  CN and Cu²⁺. The increasing extent of E′ increased with the rise of CuSO₄ content, suggesting the formation of a greater number of crosslinks. Moreover, the activation energy (E_a) of crosslinking process was about 139 kJ/mol. In this work, fourier transform infrared spectrum (FT-IR) and equilibrium swelling method were also performed for the characterization of the compound. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 41–51, 2007     

结晶水对硫酸铜与丁腈橡胶之间配位交联反应的影响

利用动态力学分析(DMA)、差示扫描量热分析(DSC)、扫描电子显微镜(SEM)、平衡溶胀法、力学性能测试等分析手段, 通过研究五水硫酸铜(CuSO4·5H2O)填充的NBR考察了结晶水对CuSO4与NBR之间配位交联反应的影响. 结果表明, 结晶水的存在可以促进该配位交联反应.     

硫酸铜含量对硫酸铜与丁腈橡胶之间配位交联反应的影响

利用丁腈橡胶(NBR)的可配位侧基——腈基(—CN)与金属盐硫酸铜(CuSO4)的铜离子(Cu2+)之间的配位反应制备了一种配位交联CuSO4/NBR.影响该配位交联反应的因素众多,如热压温度、热压时间、增塑剂等等,考察了CuSO4含量对其的影响.通过X射线光电子能谱(XPS)、动态力学分析(DMA)、差示扫描量热分析(DSC)等手段对CuSO4与NBR之间的配位交联反应进行了分析,并对所得配位交联的CuSO4/NBR进行了交联密度及力学性能的测试.结果发现,随CuSO4含量的不断增加,CuSO4与NBR的配位交联程度逐渐增强,且所得配位交联CuSO4/NBR显示出从典型橡胶到韧性塑料再到脆性塑料的力学转变特性.另外,通过扫描电子显微镜(SEM)及X射线能谱仪(EDX)对材料的微观结构进行了分析,发现CuSO4在聚合物基体中不仅充当交联剂的角色,而且还起着增强填料的作用.     

Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δ_max were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002     

Crosslinking behavior and enhanced mechanical properties of acrylonitrile‐butadiene rubber composites by incorporating aluminum ammonium sulfate particles

The crosslinked structure formed by the metal coordination bonding provides excellent and new properties for rubber materials. Herein, the crosslinking of acrylonitrile‐butadiene rubber (NBR) is induced by introducing aluminum ammonium sulfate (NH₄Al(SO₄)₂·12H₂O) particles. The crosslinking behavior, morphology, mechanical properties, and the Akron abrasion resistance of NBR/NH₄Al(SO₄)₂·12H₂O composites were fully explored. The results show that the three‐dimensional crosslinking structure is held together by metal–ligand coordination bonds between the nitrile group and AI(III). The coordination crosslink density exhibits a considerable increase with the addition of NH₄Al(SO₄)₂·12H₂O. Thus, the mechanical properties and abrasion resistance of the obtained composites are better than that of NBR/sulfur system. Interestingly, the elongation at break for NBR/NH₄Al(SO₄)₂·12H₂O composites is over 2000% due to the nature of coordination bonds. The abrasion volume loss decreases to 0.4 cm³ for NBR/NH₄Al(SO₄)₂·12H₂O composites with 20 phr NH₄Al(SO₄)₂·12H₂O particles as compared to 0.75 cm³ for NBR/sulfur system. The obtained NBR composites with facile preparation and excellent mechanical properties make the composites based on metal coordination bonding attractive for practical use. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 879–886     

COORDINATION CROSSLINKING OF NITRILE RUBBER FILLED WITH COPPER SULFATE PARTICLES

By incorporating copper sulfate(CuSO_4)particles into acrylonitrile butadiene rubber(NBR)followed by heat pressing,a novel vulcanization method is developed in rubber through the formation of coordination crosslinking.This method totally differs from traditional covalent or non-covalent vulcanization approaches of rubber.No other vulcanizing agent or additional additive is involved in this process.By analyzing the results of DMA,XPS and FT-IR,it is found that the crosslinking of CuSO_4 particles filled NBR was induced by in situ coordination between nitrogen atoms of nitrile groups (-CN)and copper ions(Cu~(2 ))from CuSO_4.SEM and EDX results revealed the generation of a core(CuSO_4 solid particle)- shell(adherent NBR)structure,which leads to a result that the crosslinked rubber has excellent mechanical properties. Moreover,poly(vinyl chloride)(PVC)and liquid acrylonitrile-butadiene rubber(LNBR)were used as mobilizer to improve the coordination crosslinking of CuSO_4/NBR.The addition of PVC or LNBR could lead to higher crosslink density and better mechanical properties of coordination vulcanization.In addition,crystal water in CuSO_4 played a positive role to coordination crosslinking of rubber because it decreased the metal point of CuSO_4 and promoted the metal ionization.     

Synthesis,characterization, processability,mechanical properties,flame retardant,and oil resistance of chlorinated acrylonitrile butadiene rubber

Novel chlorinated acrylonitrile butadiene rubber (Cl‐NBR) was prepared from NBR by the alkaline hydrolysis of chloroform by using phase‐transfer catalysis. The formation of Cl‐NBR was monitored by ¹H‐NMR, UV‐Vis, and Fourier transform infrared spectroscopic techniques. The percentage of chlorine attached to the rubber chain was estimated by Volhard method. The effect of polar groups on the structural and thermal properties of Cl‐NBR was analyzed by scanning electron microscopy, X‐ray diffraction analysis, differential scanning calorimetry, and thermogravimetric analysis studies. The flame retardant, oil resistance, cure behavior, and mechanical properties of chlorinated elastomer were also analyzed. The proton NMR revealed the attachment of chlorine in the backbone of NBR with new chemical shift values. The C‐Cl stretching of chlorinated NBR was confirmed from Fourier transform infrared. The UV spectrum also supported the formation of chlorinated unit in the NBR chain through the shifts and broadening of absorption peaks. The X‐ray diffraction analysis pattern indicated a decrease in the amorphous domain of NBR with an increase in the level of chemical modification. The increased glass transition temperature obtained from differential scanning calorimetry confirms the increased molecular rigidity of the chlorinated NBR and thermal transitions increased with increase in the level of chemical modification. The thermal stability of Cl‐NBR decreased with an increase in chlorine content. The flame and oil resistance of Cl‐NBR was greatly higher than pure NBR due to the increased polarity of modified rubber. The superior tensile strength of Cl‐NBR (4 times higher than pure NBR) and higher oil resistance find applications in pump diaphragms, aircraft hoses, oil‐lined tubing, and gaskets materials with the excellent flame resistant property.     

A novel nitrile butadiene rubber/zinc chloride composite: Coordination reaction and miscibility

In this work, an inorganic metal salt, zinc chloride (ZnCl₂), was mechanically mixed with nitrile butadiene rubber (NBR) to prepare a novel crosslinkable NBR/ZnCl₂ composite. ZnCl₂ was found to dissolve into NBR upon heating to a designed temperature, which was considered as a result of dissolution process induced by the occurrence of coordination reaction. Consequently, the morphology of the composite could change from an obvious two-phase structure to a macro-homogeneous phase structure. The determination of the coordination bonding in NBR/ZnCl₂ composite was done by Fourier transform infrared spectroscopy. The crosslinking procedure of the composite was investigated by dynamic mechanical analysis and differential scanning calorimetry. A Kissinger’s method was used to calculate the active energy. Other characterizations including scanning electron microscopy, elemental analysis, X-ray Diffraction and polarized microscope with a hot stage were used to investigate the morphology of the composite. Furthermore, the resulting material possessed special and excellent tensile properties.     

Characterization and properties of chemically modified Corchorus capsularis jute fiber via pulping and grafting: Infrared,thermogravimetric analysis,differential scanning calorimetry,scanning electron microscopy,X‐ray diffraction,biodegradation, and superabsorbency

Jute fiber (Corchorus capsularis, JRC‐321 variety), an environmentally and ecologically friendly product, was chemically modified by the cooking alkaline sulfite process to unbleached and bleached pulps, which were further modified via graft copolymerization with acrylamide monomer with a complex initiating system: CuSO₄/glycine/KHSO₅. The above samples were characterized and morphologically analyzed by IR, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and X‐ray diffraction. The biodegradability and superabsorbency of the samples were also evaluated for their novel commercial importance as jute‐based superabsorbents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2696–2703, 2003     

Reinforcement effect of MAA on nano‐CaCo3‐filled EPDM vulcanizates and possible mechanism

Methacrylic acid (MAA) was used as in situ surface modifier to improve the interface interaction between nano‐CaCO₃ particle and ethylene–propylene–diene monomer (EPDM) matrix, and hence the mechanical properties of nano‐CaCO₃‐filled EPDM vulcanizates. The results showed that the incorporation of MAA improved the filler–matrix interaction, which was proved by Fourier transformation infrared spectrometer (FTIR), Kraus equation, crosslink density determination, and scanning electron microscope (SEM). The formation of carboxylate and the participation of MAA in the crosslinking of EPDM indicated the strong filler–matrix interaction from the aspect of chemical reaction. The results of Kraus equation showed that the presence of MAA enhanced the reinforcement extent of nano‐CaCO₃ on EPDM vulcanizates. Crosslink density determination proved the formation of the ionic crosslinks in EPDM vulcanizates with the existence of MAA. The filler particles on tensile fracture were embedded in the matrix and could not be observed obviously, indicating that a strong interfacial interaction between the filler and the matrix had been achieved with the incorporation of MAA. Meanwhile, the presence of MAA remarkably increased the modulus and tensile strength of the vulcanizates, without negative effect on the high elongation at break. Furthermore, the ionic bond was thought to be formed only on filler surface because of the absolute deficiency of MAA, which resulted in the possible structure where filler particles were considered as crosslink points. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1226–1236, 2006     

Preparation and phase behavior of side‐chain cholesteric liquid‐crystalline elastomers

A series of new side‐chain cholesteric elastomers derived from cholesteryl 4‐(10‐undecylen‐1‐yloxy)‐4′‐ethoxybenzoate and phenyl 4,4′‐bis(10‐undecylen‐1‐yloxybenzoyloxy‐p‐ethoxybenzoate) was synthesized. The chemical structures of the monomers were confirmed by elemental analyses, Fourier transform infrared, and ¹H NMR and ¹³C NMR spectra. The mesomorphic properties of elastomers were investigated with differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X‐ray diffraction measurements. The influence of the content of the crosslinking unit on the phase behavior of the elastomers was examined. Monomer M₁ showed a cholesteric phase, and M₂ displayed smectic and nematic phases. The elastomers containing <15 mol % of the crosslinking units revealed reversible mesomorphic phase transition, wide mesophase temperature ranges, and high thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3315–3323, 2005     

Enhanced Self‐Cleaning Properties on Polyester Fabric Under Visible Light Through Single‐Step Synthesis of Cuprous Oxide Doped Nano‐TiO2

Nowadays, introducing self‐cleaning properties on various fabrics under daylight irradiation for automotive and upholstery application is in a central point of research. This can be achieved by application of metal‐doped TiO₂ nano particles on the textile fabrics. Here, alkali hydrolysis of polyester fabric has been carried out along with synthesis of Cu₂O/TiO₂ nanoparticles in a single‐step process by using sonochemical technique. CuSO₄.5H₂O was used as a source of copper in the presence of glucose as reducing and stabilizing agent. Moreover, central composite design based on response surface methodology (RSM) was used to determine the role of variables (CuSO₄.5H₂O, glucose and pH) and their effects on the self‐cleaning properties and weight of the fabric. The self‐cleaning property was investigated by degradation of Methylene blue on the surface of the treated fabrics under daylight. Further, the tensile properties, colorimetric measurement, and washing fastness of the treated fabric produced in the optimum conditions were investigated. The morphology of Cu₂O/TiO₂ nanoparticles was examined using X‐ray diffraction and field emission scanning electron microscopy (FESEM). The new polyester fabric obtained through in situ synthesis of Cu₂O/TiO₂ nanoparticles can be used as a desirable stable fabric with high tensile strength and visible‐light self‐cleaning properties.     

Crosslinking of vinyl‐terminated biphenyl and naphthalene side‐chain liquid‐crystalline poly(epichlorohydrin) derivatives

We performed the crosslinking of vinyl‐terminated biphenyl and naphthalene side‐chain liquid‐crystalline polyethers using peroxide‐type initiators with and without the addition of tertiary amine promoters. The crosslinking temperatures were chosen in the range of mesophase stability to allow the mesophase order to be frozen. The biphenyl derivatives, with a high isotropization temperature, were crosslinked to a large extent. This led to anisotropic thermosets. To crosslink naphthalene derivatives, amine promoters were needed, but degrees of crosslinking were lower, and anisotropic elastomers were obtained. Crosslinking processes were studied by differential scanning calorimetry, polarized optical microscopy, and Fourier transform infrared spectroscopy. The nature of the frozen mesophase was confirmed by X‐ray diffraction studies on mechanically oriented samples. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2237–2244, 2002     

Cure temperature influence on natural rubber—A small angle X‐ray scattering study

To analyze the natural rubber behavior during vulcanization under different cure treatments, an experimental investigation using small angle X‐ray scattering was performed. To achieve this, a set of samples were prepared using sulfur and N‐t‐butyl‐2‐benzothiazole sulfenamide as accelerator and then cured at temperatures between 403 and 463 K reaching their optimum mechanical properties considering rheometer tests. The crosslink density of the samples was evaluated by means of the swelling technique in solvent. In the usual Lorentz corrected representation of the X‐ray scattered intensity, a maximum was observed in the plots corresponding to the cured samples, revealing a highly correlated structure. This maximum shifted toward higher values of the scattering vector when the cure temperature of the samples increased. This behavior is discussed in terms of the crosslinks type present in the vulcanized rubber network at different cure temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2966–2971, 2007     

Preparation and characterization of a nanoscale poly(vinyl alcohol) fiber aggregate produced by an electrospinning method

Nanoscale poly(vinyl alcohol) (PVA) fiber (100–500 nm) aggregates were prepared with an electrospinning technique. Additionally, a chemical crosslinking method was used to crosslink the nanoscale PVA fiber aggregates. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and scanning electron microscopy techniques were employed to characterize the PVA fiber aggregates. The different crosslinking densities of the PVA fiber aggregates were obtained through the control of the weight percentage of glyoxal to PVA. The crosslinking densities due to heat treatment and chemical crosslinking were studied. The influence of heat treatment could be neglected in contrast to chemical crosslinking when the curing temperature was 120 °C. The primary factor that affected the crosslinking density was the volume of the chemical crosslinking agent. The results showed that the properly crosslinked PVA fiber aggregates had better antiwater solubility and mechanical properties than the noncrosslinked PVA fiber aggregates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1261–1268, 2002     

In situ polymerization of silicic acid in polyethylene–octene elastomer: Properties and characterization of the hybrid nanocomposites

Silicic acid produced from sodium metasilicate hydrate and metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, the acrylic acid‐grafted polyethylene–octene elastomer (POE‐g‐AA) prepared in our laboratory and used as the continuous phase was also investigated. Characterizations of POE/SiO₂ and POE‐g‐AA/SiO₂ composites were performed by Fourier transform infrared spectroscopy, ²⁹Si solid‐state nuclear magnetic resonance (NMR) spectrometry, X‐ray diffractometry, differential scanning calorimetry, thermogravimetry analysis, and an Instron mechanical tester. The POE‐g‐AA/SiO₂ hybrid could give the positive effect on the properties of POE/SiO₂ hybrid because the carboxylic acid groups of acrylic acid should act as coordination sites for the silica phase to form chemical bonds. The result of ²⁹Si solid‐state NMR spectra showed that Si atom coordination around SiO₄ units is predominantly Q₃ and Q₄. Also, the POE‐g‐AA/SiO₂ hybrid with 15 wt % SiO₂ gave the maximum values of tensile strength and glass‐transition temperature because excess particles might cause the separation between the organic and inorganic phases when the silica content was beyond this point. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 351–359, 2003     

Effect of carbon nanofibers on mechanical and electrical behaviors of acrylonitrile‐butadiene rubber composites

Recently, carbon nanofibers have become an innovative reinforcing filler that has drawn increased attention from researchers. In this work, the reinforcement of acrylonitrile butadiene rubber (NBR) with carbon nanofibers (CNFs) was studied to determine the potential of carbon nanofibers as reinforcing filler in rubber technology. Furthermore, the performance of NBR compounds filled with carbon nanofibers was compared with the composites containing carbon black characterized by spherical particle type. Filler dispersion in elastomer matrix plays an essential role in polymer reinforcement, so we also analyzed the influence of dispersing agents on the performance of NBR composites. We applied several types of dispersing agents: anionic, cationic, nonionic, and ionic liquids. The fillers were characterized by dibutylphtalate absorption analysis, aggregate size, and rheological properties of filler suspensions. The vulcanization kinetics of rubber compounds, crosslink density, mechanical properties, hysteresis, and conductive properties of vulcanizates were also investigated. Moreover, scanning electron microscopy images were used to determine the filler dispersion in the elastomer matrix. The incorporation of the carbon nanofibers has a superior influence on the tensile strength of NBR compared with the samples containing carbon black. It was observed that addition of studied dispersing agents affected the performance of NBR/CNF and NBR/carbon black materials. Especially, the application of nonylphenyl poly(ethylene glycol) ether and 1‐butyl‐3‐methylimidazolium tetrafluoroborate contributed to enhanced mechanical properties and electrical conductivity of NBR/CNF composites.     

Hollow microspheres with covalent‐bonded colloidal and polymeric shell by Pickering emulsion polymerization

Hollow microspheres with SiO₂/polymer binary shell were fabricated from Pickering emulsion stabilized solely by methacryloxypropyltrimethoxysilane‐modified SiO₂ particles, and were characterized by optical microscopy, scanning electron microscopy, Fourier transformation infrared spectrum, thermogravimetric analysis (TGA), and energy dispersive X‐ray spectroscopy. The microspheres were templated by the Pickering droplets and the inner structure was affect by the proportion of crosslinking reagent. TGA result indicated that 60.3% of polymer in the shell was connected with SiO₂ by covalent bond which was formed by copolymerization of styrene and the reactive C?C group on SiO₂ stabilizer. Copyright © 2011 John Wiley & Sons, Ltd.     

Structure and coordination properties of facilitated olefin transport membranes consisting of crosslinked poly(vinyl alcohol) and silver hexafluoroantimonate

The high selectivity of solid‐state crosslinked poly(vinyl alcohol) (CPVA) membranes containing silver hexafluoroantimonate (AgSbF₆), with respect to olefin/paraffin mixtures, was previously reported. The structure and coordination properties of CPVA/AgSbF₆ complexes were investigated in this study with wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), X‐ray photoelectron spectroscopy (XPS), and theoretical ab initio calculations, and they were compared with those of poly(vinyl alcohol) (PVA)/AgSbF₆ complexes. Contrary to expectations, the measurements of the intersegmental d‐spacings and glass‐transition temperatures indicated that the chain mobility in the PVA/AgSbF₆ membranes was lower than that in the CPVA/AgSbF₆ membranes. The different extents of transient crosslinking in the two systems were attributed mostly to their different coordination structures; silver ions in PVA/AgSbF₆ were coordinated with hydroxyl oxygens located near the polymer main chains, whereas those in CPVA/AgSbF₆ were coordinated with aldehyde oxygens located far from the main chains. According to WAXS spectra, AgSbF₆ was completely dissolved in both PVA and CPVA, and this disrupted the crystallinity of the polymers. However, our DSC study showed that the silver ions dissolved in both polymer matrices recrystallized into silver oxide at elevated temperatures. The binding energy of Ag3d_5/2, as determined from XPS spectra, shifted to lower values with the addition of increasing amounts of the polymer matrix, indicating the increasing coordination of silver ions with polymer chains. The presence of various oxygen species with and without coordination to silver ions was confirmed from O1s XPS spectra of CPVA membranes containing silver ions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 621–628, 2004