在橡胶加工设备中制备溴化丁基橡胶

选用无溶剂的本体法,以N-溴代琥珀酰亚胺与少量丁基橡胶(IIR)和稳定剂的预混物为溴化剂,在橡胶加工设备中对IIR进行化学改性,制备溴化丁基橡胶(BIIR)。通过红外光谱、核磁共振氢谱对产物BIIR的结构进行分析,并考察反应时间、温度和溴化剂用量等对BIIR硫化特性和物理性能的影响。结果表明:采用该方法可以制得BIIR,没有观察到腐蚀设备的情况,产物BIIR的硫化速率相比原料IIR有明显提高,硫化特性和物理性能达到了商品BIIR的水平;溴化反应温度应在60~100℃范围内,在所考察的范围内,溴化剂用量和反应时间对BIIR的硫化特性和物理性能影响不大。     

The interrelation among network structures,molecular transport of solvent,and creep behaviors of TiB2 ceramic containing butyl rubber composites

Swelling of polymer composites in solvents has become one of the major problems in the use of polymer composites exposed to petroleum products. As a possible solution to the problem, this experimental study was conducted to examine the potential application of TiB₂ ceramic in butyl rubber (IIR) composites. The effect of TiB₂ content on the curing kinetics of IIR composites was studied using a torque rheometer technique. The effect of TiB₂ on the network structure was investigated in terms of the crosslinking density, interparticle distance between conducting particles, surface tension, glass transition temperature, degree of crystallinity, scanning electron microscopy, and X‐ray analysis. Moreover, the effect of TiB₂ content on the molecular transport of solvent (kerosene) was examined by means of degree of swelling, solvent interaction parameters, volume fraction of rubber, interparticle distance after swelling, penetration rate of solvent, mean diffusion coefficient, cohesive energy density of polymer, standard entropy, standard enthalpy, and standard free energy of IIR composites. It was ascertained that with increasing TiB₂ content the degree of swelling shifts to a lower value. The main reason was interpreted as the introduction of good interface adhesion of TiB₂ with rubber matrix, which tends to block the diffusion of solvent molecules. The effect of TiB₂ content on hardness, tensile strength, Young's modules, and elongation at break is discussed. An apparent steady‐state creep of butyl rubber IIR/TiB₂ composites is evident under different constant stresses at room temperature. The strain rate of steady‐state creep showed a dependence on stress and TiB₂ volume fraction. The stress sensitivity parameter, viscosity coefficient, and activation volume for samples loaded with different content of TiB₂ were estimated. It is apparent that these new composites should be very useful for solvent permeation resistance at high TiB₂ loading level with good mechanical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2226–2235, 2005     

Synthesis of butyl rubber in hexane using a mixture of Et2AlCl and EtAlCl2 in the initiating system

A method was studied to obtain butyl rubber in hexane at ?75 and ?60°C using a mixture of a major amount of diethylaluminum chloride and a minor amount of ethylaluminum dichloride in the initiating system. The Jaacks method was used to determine the monomer reactivity ratio of isobutylene in copolymerization with isoprene in hexane at ?75°C with the above initiating system; r_IB = 1.54 ± 0.06. This value was different from a literature value r_IB = 1.08 when just EtAlCl₂ was used in hexane at ?80°C. The mixture of both alkylaluminum chlorides in the initiating solution was subsequently directly activated with minute amounts of water or methylaluminoxane (MAO). The use of the modified initiators resulted in higher molecular weights, higher degrees of conversion, and higher isoprene contents in the butyl rubber. At the same time, temperature control was good during polymerizations. With modified alkylaluminum halides, the monomer reactivity ratio of isobutylene in copolymerization with isoprene in hexane at ?75°C was close to unity, similar to the reported case with just EtAlCl₂. The system activated with MAO made it possible to synthesize butyl rubber in hexane at ?60°C having main characteristics typical of commercial butyl rubber manufactured in methyl chloride at ?95°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2360–2364, 2003     

Elastic Behaviour of Ternary Rubber-filled Vulcanizates

Near-equilibrium stress–strain measurements have been carried out on ternary rubber vulcanizates. The effect of variation of the butyl rubber content on the elastic behaviour of the ternary rubber vulcanizates has been studied. It has been found that butyl rubber (IIR) is less sensitive to the vulcanization system used than either natural rubber (NR) or styrene–butadiene rubber (SBR). One can obtain a partially crosslinked system with an IIR phase embedded in the crosslinked matrix of NR and SBR. The role played by carbon black during mixing of the ternary blend has been investigated. The Mooney–Rivlin relationship was used to describe the behaviour of the ternary rubber matrix. The constants 2C₁ and 2C₂ have been calculated by use of the strain-amplification factor and the total crosslink density of the ternary rubber–carbon black systems has been investigated. The data have been evaluated in terms of the molecular theories of rubber elasticity. The elastic behaviour was found to be intermediate between the affine and phantom limits of the theory. © of SCI.     

Curing of epoxy/novolac system modified with reactive liquid rubber and carbon filler

The curing behaviour of epoxy resins modified with reactive liquid rubber, using a novolac resin as a hardner was studied by means of differential scanning calorimetry in isothermal (100, 130 and 150 °C) and non-isothermal conditions (2, 5, 10 and 15 °C min^-1). The influence of carboxyl- (CTBN) and epoxy- (ETBN) terminated butadiene-acrylonitrile copolymers on the kinetic parameters and glass transition temperature (T_g) of cured epoxy systems was determined. The effect of grinded bituminous coal as an organic filler into epoxy network was also investigated. The carboxyl-end groups strongly enhanced the curing rate, in contrast to the epoxy-terminated rubber (ETBN) that had only a minor effect on the curing reactions. The presence of coal accelerated curing in its early stage. The T_g of completely cured epoxy was practically unaffected by the presence of carbon filler and reactive rubbers and was equal about 132 °C. The apparent curing activation energies were determined. A smaller activation energy was observed only for CTBN/epoxy/novolac system. The effect of reactive rubber and coal on the Charpy impact resistance of cured epoxy systems was also discussed.     

Crosslinking reaction of rubber with aldehydes

The reactions of rubber with aldehydes have previously been studied in latex or in solutions and the reaction products formed by cyclization, condensation, or addition, have been reported. In the present study, solid-state reactions of rubber with aldehydes were carried out. It was found that crosslinked rubbers may be obtained by press curing in the presence of aldehydes with acidic catalysts. Polychloroprene and Hypalon especially undergo these reactions without a catalyst or with a small amount of catalyst. In the experiments using various aldehydes, some improvements in the properties of the crosslinked rubber were observed when aldehydes such as paraformaldehyde or α-polyoxymethylene were used. Some Lewis acids such as SnCl₂·2H₂O were found to be more effective catalysts than the above, and it was found that organic acids such as p-toluenesulfonic acid could also be used. The curing seemed to be an ionic reaction. The physical properties of the crosslinked rubber are similar to these of sulfur-cured rubbers.     

On-line GPC/NMR analyses of block and random copolymers of methyl and butyl methacrylates prepared with t-C4H9MgBr

Summary The isotactic block and random copolymers of methyl methacrylate and butyl methacrylate prepared with t-C₄H₉MgBr in toluene, were analyzed by using a 500 MHz ¹H NMR spectrometer as a detector of gel permeation chromatography. The molecular weight dependence of the chemical compositions of these copolymers could be directly determined with this method by monitoring signal intensities of OCH₃ and OCH2 due to methyl methacrylate and butyl methacrylate units, respectively. From the results mechanism of the copolymerizations was discussed in some detail.     

Measurement of diffusivities of sulfur mustard (SM) and its analog oxygen mustard (OM) in cured butyl,nitrile, and natural-rubber sheets by weight gain and FTIR–ATR methods

The breakthrough time of butyl, nitrile, and natural-rubber sheets (cured) of different compositions against a potent chemical warfare (CW) agent have been determined using the spot disc test (SDT) method. It was observed that butyl rubber is the best material in comparison to nitrile and natural rubber for protection against sulfur mustard (SM). One of the butyl formulations provides more than 100 h protection against SM. The diffusion coefficient of oxygen mustard (SM analog) for the same formulation (F₈) and one nonblack butyl formulation (F₅) was determined by weight gain as well as by FTIR–ATR methods. Both methods provide consistent results and the diffusion coefficient of oxygen mustard (OM for butyl rubber is in the order of 10^?9cm²/s. The diffusion coefficient of SM for the form lation F₈ and F₅ was also determined from the SDT retardation time. © 1995 John Wiley & Sons, Inc.     

Cure Characteristics,Mechanical and Thermal Properties of Al2O3 and ZnO Reinforced Silicone Rubber

The effects of alumina (Al₂O₃) and zinc oxide (ZnO) fillers on the curing characteristics, thermal and mechanical properties of silicone rubber were studied. Rheometer results indicate that the incorporation of ZnO fillers retards the curing process, whereas an enhancement in cure rate was observed for Al₂O₃. Higher maximum torque (M_H) and minimum torque (M_L) values was also observed for ZnO silicone rubber compounds compared to Al₂O₃. Thermogravimetric analysis (TGA) showed that ZnO silicone rubber compounds are thermally more stable than Al₂O₃; however, the coefficient of thermal expansion of the Al₂O₃ silicone rubber compounds are lower than that of ZnO. Comparison in mechanical strength between the two silicone rubber hybrids indicates that ZnO is a better reinforcement filler, as evidenced in the tensile strength, elongation at break, and modulus at 300% elongation.     

Preparation of 2‐(dimethylamino) ethyl methacrylate copolymer micelles for shape memory materials

Researchers are actively developing shape memory polymers (SMPs) for smart biomaterials. This paper reports a new SMP system synthesized from biocompatible 2‐(dimethylamino) ethyl methacrylate (DMAEMA), butyl acrylate (BA) and tri(ethylene glycol) divinyl ether (TDE). Preliminary results show that the DMAEMA‐co‐BA‐co‐TDE copolymers form micelles in aqueous solution due to chemical crosslinking and hydrophobicity. The micelle size decreased with the increase in the BA content since the hydrophobicity of copolymers increases with the increase of BA content. The resulting polymer films contain–N(CH₃)₂ functional groups for further biomaterial applications. The thermal stability of DMAEMA‐co‐BA‐co‐TDE copolymers is determined by the DMAEMA structure and content. Moreover, the copolymers form micro‐phase‐separated structures containing a reversible amorphous soft phase, and the storage moduli decreases significantly around T_g. Therefore, good thermal‐induced shape memory effects are achieved in the DMAEMA‐co‐BA‐co‐TDE copolymers by adjusting the BA content. This work proposes a new strategy for designing smart biomaterials using a biocompatible monomer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42312.     

Development of butyl rubber nanocomposites in presence and absence of compatibiliser

Abstract

Chlorobutyl rubber nanocomposites containing organically modified nanoclay (CI-C) were prepared by solution mixing. The nanoclay used in this study was Cloisite 20A. The obtained nanocomposites were incorporated in butyl rubber (IIR) with sulphur as a curing agent. Morphology, curing characteristics, mechanical and gas barrier properties of the nanocomposites were analysed. The morphological studies proved the partial exfoliation along with agglomeration of nanoclay platelets in chlorobutyl rubber, and further incorporation of CI-C in IIR matrix enhance the exfoliation of the nanoclay platelets. Curing study demonstrated shorter scorch time, cure time and increase in maximum torque for the nanoclay loaded IIR compound in the presence of chlorobutyl rubber as a compatibiliser compared to pure and IIR-nanoclay compound without compatibilisers. Dynamic mechanical thermal analysis results showed tremendous improvement in storage modulus and decrease in tan?δ value for the one containing a compatibiliser. This particular compound exhibited substantial improvement in mechanical and gas barrier properties.     

Effect of butyl rubber type on properties of polyamide and butyl rubber blends

Polyamide‐12 was blended with butyl rubber, bromobutyl rubber, and chlorobutyl rubber with and without a sulfur curing system. Mechanical properties for dynamically vulcanized blends generally exceed those made with no vulcanization. Chlorobutyl‐containing blends prepared by dynamic vulcanization have higher tensile strength and elongation at break values in comparison to those made from other butyl rubbers. For a variety of polyamide/rubber blends made by dynamic vulcanization, there is very little effect of rubber percentage unsaturation and Mooney viscosity on the mechanical properties of the blends. In chlorobutyl‐containing blends prepared by dynamic vulcanization, the swelling index values attributed to the rubber portion decrease as rubber content decreases, and it is likely that the polyamide phase completely surrounds the rubber particles at compositions exceeding approximately 25% polyamide. Swelling index results can be correlated with elongation at break values for similar blends. The results of differential scanning calorimetry suggest that the polyamide phase is not a neutral component in high shear mixing with butyl rubbers with or without curing agents. Rheological studies indicate strong non‐Newtonian behavior for all blends of polyamide‐12 with butyl rubbers. Scanning electron microscopy on polyamide‐12/butyl rubber blends indicates compatibility for butyl rubbers in the order of chlorobutyl > bromobutyl > butyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1423–1435, 2004     

Interpretation of 2H-NMR lineshapes of PEO

Summary Temperature dependent ²H-nmr lineshapes and relaxation times T_2e of poly(ethylene oxide) (PEO_d) and two block copolymers of deuterated PEO_d and protonated poly(butyl methacrylate) (PBMA_h) were measured. The results were compared with simulated lineshapes and relaxation times and discussed as the glass transition of PEO chains.     

Use of poly(2-vinylpyridine)-b-poly(?-caprolactone) copolymers as pigment stabilizers in powder coatings

Four poly(2-vinylpyridine)-b-poly(ɛ-caprolactone) copolymers, differing in buoy block length and anchor/buoy block length ratio, have been used as TiO₂ pigment dispersants in a polyester powder coating resin. When the TiO₂ surface was fully covered with the block copolymers, the colloidal stability of the TiO₂ dispersions at typical curing temperatures was significantly improved because of the formation of a steric layer around the pigment particles. As a result, powder coatings with excellent flow, high gloss, and low haze values were obtained. Because of the high affinity of the dispersants for the TiO₂ surface, pretreatment of the pigments with the block copolymers was not necessary. At full pigment surface coverage, the chain length of the stabilizing polymer had little effect on the performance of the dispersants used. Dept. of Polymer Chemistry and Coatings Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.     

Effect of Copolymer Composition on the Dynamic Mechanical and Thermal Behaviour of Butyl Acrylate‐Acrylonitrile Copolymers

This article reports data on the dynamic mechanical and thermal behaviour of butyl acrylate‐acrylonitrile copolymers and their variation with copolymer composition. The copolymers were prepared by emulsion polymerisation techniques, using potassium peroxodisulfate initiator at 80 ± 2 °C. Films were prepared from the latex by casting and analysed by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). For copolymer with 0.7 weight fraction of butyl acrylate the dynamic mechanical behaviour was identical to the synthetic rubber NBR (acrylonitrile‐butadiene rubber), such that the storage modulus shows a rapid decay with increasing temperature. The damping characteristics, as indicated by the tan δ value, increased as the weight fraction of butyl acrylate in the copolymer increased. The dynamic mechanical data has been analysed with the WLF‐Equation to study the time‐temperature relationship. The dynamic mechanical properties and glass transition data point to the formation of a copolymer, whose properties vary with acrylonitrile content. Thermogravimetric analysis revealed that weight loss occurring at a particular temperature decreases, along with the decomposition rate, with increase in acrylonitrile content. The activation energy (E_a) for the decomposition was calculated using the Coats & Redfern equation. When temperatures for 10% copolymer decomposition are compared from TGA data, the acrylonitrile rich copolymer starts decomposing at a lower temperature, but the rate of decomposition is slower and yields higher char yields.

Effect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.     

Short fibers as reinforcement of rubber compounds

The effect of aramid, glass and cellulose short fibers on the processing behavior, crosslinking density and mechanical properties of natural rubber (NR), ethylene‐propylene‐diene terpolymer rubber (EPDM) and styrene‐butadiene rubber (SBR) has been investigated. Two fiber percentages (10 and 20 phr) were added to the rubber. The results have shown that the above‐mentioned fibers, especially aramid fibers, are effective reinforcing agents for these rubbers, giving rise to a significant increase in mechanical properties, such as tensile modulus and strength, and tear and abrasion resistance. Moreover, a significant decrease in the time to reach 97% of curing, t′_c (97) is observed, which indicates that the fibers tend to increase the vulcanization rate, regardless of the rubber used. Fibers give also rise to an increase in crosslinking, especially the aramid fibers.     

IIR/CIIR共混胶硫化特性的研究

研究了影响丁基橡胶／氯化丁基橡胶(IIR／CIIR)共混胶硫化特性的因素．包括并用比、硫化体系、补强剂和硅炕偶联剂。研究结果表明：随着IIR／CIIR共混胶中CIIR含量的增加，硫化速度加快，是大转矩值减小：用硫磺硫化的共混胶硫化速度比用树脂硫化的快，且共混胶起始转矩值也较高。在选用的几种补强剂中，添加N220补强的共混胶硫化速度较快，T90时间较短，添加活性沉淀白炭黑(WCB)补强的共混胶最大转矩值较高。加入硅烷偶联剂会使共混胶的T90时间延长，最大转矩值变高。     

New gasoline and gas barrier from plasticized carbon black reinforced butyl rubber/high‐density polyethylene blends

The effects of the high‐density polyethylene volume fraction on the curing characteristics and network structure of rubber blends have been studied in terms of the torque, scorch time, optimum curing time, Mooney viscosity, number of elastically effective chains, viscosity, interfacial tension, glass‐transition temperature, scanning electron microscopy, internal friction, sound velocity, acoustic attenuation, polymer–solvent interaction parameter, swelling index, and gel fraction. The applicability of the blends for gasoline barriers has been examined through the changes in the electrical resistance and volumetric swelling in gasoline versus time at room temperature. The transport mechanism of the solvent through the crosslinked butyl rubber/high‐density polyethylene blends is governed by Fickian diffusion law. The transport coefficients, namely, the diffusion coefficient, intrinsic diffusion, and permeation coefficient, have been computed. The experimental data for the permeation coefficient are in good agreement with the values calculated by Maxwell's model and far from those of Robeson's model. In addition, some thermodynamics parameters, namely, the standard entropy, standard enthalpy, and standard Gibbs free energy, have been estimated as functions of the high‐density polyethylene concentration of the butyl rubber blends. Furthermore, the applicability of butyl rubber/high‐density polyethylene composites for Freon gas barriers and antistatic charge dissipation has been examined. Finally, the mechanical properties, such as the tensile strength, hardness, stiffness, and elongation at break, of butyl rubber composites with different high‐density polyethylene concentrations have been evaluated. The increase in the mechanical properties is due to the increase in the crosslinking density and the interfacial adhesion of the blend. This proves that these new blends have important technological applications as gasoline and Freon barriers and for antistatic charge dissipation with good mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1237–1247, 2006     

Vulcanization of chlorobutyl rubber. II. A revised cationic mechanism of ZnO/ZnCl2 initiated crosslinking

Data relating to the ZnO/ZnCl₂‐accelerated vulcanization of chlorinated poly(isoprene‐coisobutylene) (CIIR or chloro‐butyl) is examined. ZnCl₂ and conjugated diene butyl units on the polymer chain are both precursors to crosslinking, and a revised cationic mechanism is proposed to account for crosslinking, taking into account the involvement of conjugated diene butyl in the process. It is demonstrated that Zn₂OCl₂ will catalyze dehydrohalogenation, and the formation of catalytic amounts of Zn₂OCl₂ by the reaction of ZnCl with ZnO, followed by H⁺ abstraction to give Zn₂OCl₂ and HCl, is essential in the overall crosslinking reaction sequence. The HCl is trapped by ZnO as ZnCl₂. It is proposed that the abstraction by Zn₂OCl₂ of HCl in a concerted reaction leads to Zn(OH)Cl and ZnCl₂. Zn(OH)Cl remains in the polymer as an unextractable salt, while 50% of the chlorine in the rubber is extracted as ZnCl₂ when compounds reach their equilibrium crosslink density. ZnCl₂ initiates crosslinking by the abstraction of chlorine from the chain, but a crosslink will only result when a carbocation on a dechlorinated isoprenoid unit is close to a conjugated diene butyl on an adjacent chain; if not, dehydrohalogenation will result in the formation of a further conjugated diene butyl unit at that point in the chain. The maximum crosslink density achieved is only 1/4 that theoretically possible, as crosslinking restricts chain movement and limits the number of chance meetings between carbocations on the polymer and conjugated diene butyl units. Zinc stearate promotes dehydrohalogenation, ZnCl₂ being the only chloro‐zinc salt formed. Reversion occurs in compounds where there is insufficient ZnO to trap all of the chlorine present in the rubber. HCl per se does not attack the polymer, but promotes reversion only in the presence of carbocations on the chain, i.e., during the crosslinking process. Trapping of HCl by ZnO prevents reversion. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2302–2310, 2000     

Molecular dynamics study on the dissolution behaviors of poly(vinyl acetate)-polyether block copolymers in supercritical CO2

Poly(vinyl acetate) (PVAc) could be dissolved in CO₂ at a high pressure, which limits its application. In this work, the PVAc-polyether block copolymers were constructed by introducing the CO₂-philic blocks poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO) into the PVAc molecules to increase the solubility of these polymers in supercritical CO₂ (scCO₂). The dissolution behaviors of PVAc-polyether copolymers with different structures in scCO₂ were investigated by the molecular dynamic simulation methods. First, the cohesive energy and solubility parameters of PVAc, PVAc-PEO, and PVAc-PPO copolymers were analyzed. Moreover, the mechanism of PVAc-polyether copolymers dissolving in CO₂ was investigated. The results show that PVAc-PPO molecules have a higher solubility in CO₂ because they have lower polymer–polymer and higher polymer-CO₂ interactions than PVAc and PVAc-PEO. Among the three structures of PVAc-PPO molecules, PVAc-PPO-PVAc (VPV) has a highest solubility in CO₂. Therefore, the molecular composition and structure have greatly influences on the interactions of polymer and CO₂.