天然橡胶硫化动力学研究

采用硫化仪测定了2种不同凝固工艺的天然橡胶（NR）的硫化过程,探讨了制胶工艺、配方和温度对硫化动力学参数的影响。研究结果发现,随着温度的上升,硫化速率常数迅速上升。在纯胶体系中,微生物凝固胶的活化能高于酸凝固胶。当加入炭黑后,酸凝固胶的活化能升高,而微生物凝固胶的活化能下降。     

Study on kinetic of natural rubber vulcanization by using vulcameter

The velocity of vulcameter torque change during the vulcanization of natural rubber consists of two increasing and decreasing stages. The vulcanization process in the stage of velocity increasing is not a simple reaction, and can be expressed in an equation of ln(M_H ? M_t) = lnA ? K₁(t ? t₀)^α, which is different from the famous equation of V_ut = ? (aK₃/K₄)ln[(K₂e^K1t ? K₁e^K2t)/(K₂ ? K₁)] deduced by Coran, the value of K₁^1/α in the former can be used as a rate constant to calculate the value of activation energy (E₁) according to the Arrhenius equation. The vulcanization process in the stage of velocity decreasing consists of two first‐order reactions, and can be expressed in a kinetic equation of ln(M_H ? M_t) = lnB ? K(t ? t_dis). The time (t_p) at which the torque change reaches to the maximum velocity (V_m) is corresponding to the time (t_dis) suggested by Coran. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 680–684, 2003     

蛋白质对天然橡胶硫化动力学的影响

选用与天然胶乳中的d球朊结构类似的牛白蛋白,将其加入到经Alcalase蛋白酶处理得到的低蛋白天然橡胶中,通过硫化仪法研究了蛋白质对胶料硫化动力学的影响。结果表明：各胶样的硫化反应可按一级反应处理;在相同温度条件下,随着蛋白质用量的增加,焦烧时间（t10）和正硫化时间（t90）缩短,硫化反应速率提高,说明牛白蛋白能够提高天然橡胶的硫化速度;硫化速率随着温度的升高而显著提高,且都能很好地符合阿伦尼乌斯方程;反应活化能随着蛋白质用量的增加而提高。     

Effect of 2‐mercaptobenzothiazole level on kinetics of natural rubber vulcanization

The kinetics of natural rubber vulcanization were investigated by use of a vulcameter. The vulcanization process before t_dis (the time when the accelerators and/or intermediates react to depletion) was expressed in an equation as ln(M_H ? M_t) = ln A ? k₁(t ? t₀)^α, which is different from the famous equation of Vu_t = ?[α(k₃/k₄)]ln[(k₂e ? k₁e)/(k₂ ? k₁)] deduced by Coran. It was found that the rate constants of two vulcanization processes with different reaction mechanisms before and after t_dis increase and their activation energies decreased with an increase in 2‐mercaptobenzthiazole (MBT) level. The considerable effect of MBT level on the activation energies of the vulcanization process before t_dis and the obvious temperature dependency of the reaction rate of vulcanization process after t_dis were observed. The time t_dis was shortened with an increase in MBT level, whereas the degree of vulcanization at t_dis remained unchanged. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3260–3265, 2004     

Effect of non‐rubber substances on vulcanization kinetics of natural rubber

Effect of non‐rubber components on vulcanization kinetics of natural rubber was studied with the use of a Rheometer MDR‐2000. The results show that the rate constants of induction period and curing period of natural rubber (NR) are greater than that of natural rubber extracted with acetone (NR_E), and the activation energies of induction period and curing period of NR are lower than that of NR_E. The activation energy of induction period of NR is reduced by16.9% and the activation energy of curing period of NR is reduced by 3.2% compared to the activation energies of NR_E. The time t_dis of NR is shorter than that of NR_E at the same temperature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

环氧型丙烯酸酯橡胶的硫化

通过硫化曲线评定,选用苯甲酸铵作硫化剂环氧丙烯酸酯橡胶低温胶进行硫化。结果表明,共聚单体中甲基丙烯酸缩水甘油酯用量为２％－３％,苯甲酸铵用量为１．５份时,经胶的力学性能最好。二段硫化对硫胶的力学性能几乎无影响。     

Melt‐compounded natural rubber nanocomposites with pristine and organophilic layered silicates of natural and synthetic origin

Composites based on natural rubber (NR) and containing organophilic and pristine layered silicates of natural and synthetic origin were produced by melt compounding and sulfur curing. The curing, thermomechanical, and mechanical properties of the mixes, which contained 10 phr (parts per hundred parts of rubber) silicates, were determined. The dispersion of the silicates was studied by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Organophilic clays accelerated the sulfur curing of NR, which was believed to occur because of a complexation reaction in which the amine groups of the clay intercalants participated. The property improvements caused by the fillers were ranked as follows: organophilic clays > pristine synthetic layered silicate (sodium fluorohectorite) > pristine natural clay (purified sodium bentonite) > precipitated nonlayered silica (used as a reference). This was attributed to partial intercalation of the organophilic clay by NR on the basis of XRD and TEM results and to the high aspect ratio of the fluorohectorite. Apart from intercalation, severe confinement (i.e., the collapse of the interlayer distance) of the organoclays was observed. This peculiar feature was traced to the formation of a zinc coordination complex, which extracted the amine intercalant of the organoclays, thus causing the collapse of the layers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 813–819, 2004     

Properties of vulcanizates from blends of natural rubber and thioglycolic acid modified,epoxidized, low‐molecular‐weight natural rubber filled with carbonized rubber seed shell

Vulcanizates from blends of natural rubber and thioglycolic acid modified, epoxidized, low‐molecular‐weight natural rubber filled with mixtures of carbon black and carbonized rubber seed shell, with semiefficient sulfur vulcanization recipes, were critically investigated and characterized. The investigated properties were the processing and rheological properties (the cure rate, cure time, scorch time, total oscillating disc rheometry torque, and Mooney viscosity), physicomechanical and chemical properties, solvent resistance, solubility, and swelling properties. On the basis of the investigated properties, it was observed that the carbonized rubber seed shell acted as a plasticizer and not as a reinforcing filler such as carbon black. The replacement of carbon black with up to 20% carbonized rubber seed shell produced vulcanizates having processing advantages in time gain and energy consumption, with their physical, chemical, and mechanical properties around the acceptable level for natural rubber compounds but lower than the properties obtained for a 100% carbon black filled vulcanizate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Rice husk ash filled natural rubber. I. Overall rate constant determination for the vulcanization process from rheometric data

Black rice husk ash (BRHA) and white rice husk ash (WRHA) were incorporated into natural rubber (NR) using a laboratory‐size two‐roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI‐100 Curometer. The torque curves were obtained at 150, 160, 170, and 180°C. The overall rate and the apparent activation energy for the vulcanization process were calculated for each compound assuming that vulcanization follows first‐order kinetics. For comparison purposes, two commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N762), were also used. It was observed that addition of WRHA to NR compounds increased the cross‐linking rate and lowered the apparent activation energy more markedly than the other fillers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1194–1203, 2003     

不同硫化体系天然橡胶阻尼减震材料的硫化动力学及其性能研究

研究硫黄和促进剂用量对高阻尼天然橡胶胶料硫化特性的影响,并通过非线性拟合探讨硫化体系对硫化胶力学性能的影响。结果表明:随着硫黄用量的减小,硫化前驱体形成交联键的反应活性和交联键降解速率均是先增大后减小,力学强度下降,阻尼性能提高;随着促进剂/硫黄用量比的增大,硫化前驱体形成交联键的反应活性提高,交联键降解速率减小,力学强度提高,阻尼性能下降。     

Preparation of low‐allergen natural rubber latex by transglutaminase catalysis

The technique of enzyme treatment on the water‐soluble proteins and mechanical properties of natural rubber latex (NRL) films was studied. The main aim was to introduce an enzymic catalysis method to tackle the protein allergy problem in NRL product. The suitable pH value, the temperature, and the best proportion of transglutaminase to deal with NRL were found. The protein spillage of modified NRL films was greatly lower than that of unmodified NRL, and the tensile strength and the elongation at break of the modified NRL films almost had been scarcely changed. The compactness of the NRL films was improved simultaneously. These suggest that the modified NRL can be used as a kind of latex with low‐allergy personal barrier products such as surgical gloves. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Properties of a new synthetic rubber: High‐trans 1,4‐poly(butadiene‐co‐isoprene) rubber

A high‐trans 1,4‐butadiene/isoprene copolymer (TBIP) was synthesized in a 5‐L autoclave with hydrogen as an effective molecular weight modifier. The effects of hydrogen on the catalyst efficiency and molecular weight of the copolymers were investigated. The processability and physicomechanical properties of TBIP and their relationship to the composition, composition distribution, and molecular weight of TBIP were examined in detail. Increasing the H₂ pressure effectively reduced the molecular weight of TBIP. The optimum Mooney viscosity of TBIP and the 1,4‐butadiene molar content in the feed were 30–50 and 5–25%, respectively. No cis–trans isomerization was observed during the roll processing procedure for TBIP. The vulcanization characteristics of TBIP were similar to those of general rubbers, and no reverse vulcanization was observed for TBIP. A high green strength was the typical characteristic of TBIP. Vulcanized TBIP (TBIR) with an optimum composition and molecular weight presented outstanding antifatigue properties and low heat buildup in comparison with general rubbers. Compared with general sidewall stock [natural rubber (NR)/butadiene rubber (BR) = 50/50], TBIR exhibited a greater than 15‐fold increase in its crack‐initiation resistance. The other mechanical properties of TBIR were similar to those of 50/50 NR/BR. The heat‐aging mechanism of TBIR was crosslinking aging. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2941‐2948, 2004     

Rice husk ash filled natural rubber. III. Role of metal oxides in kinetics of sulfur vulcanization

In preceding investigations the overall rate and apparent activation energy for the vulcanization process were calculated for natural rubber compounds, assuming that vulcanization follows first‐order kinetics. It was observed that the addition of white rice husk ash (WRHA) increased the rate of crosslinking and lowered the apparent activation energy more profoundly than commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N762), with a conventional vulcanization system. In this work, a specific model for the vulcanization process accelerated by N‐cyclohexylbenzothiazole sulfenamide was used to investigate the real role of WRHA in crosslink formation. Cure studies were carried out at 150°C, and the kinetics constants were evaluated. In relation to the other fillers, WRHA seems to develop catalytic activity, resulting in a positive effect on the specific rate of crosslink formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1519–1531, 2003     

Rice‐husk‐ash‐filled natural rubber. II. Partial replacement of commercial fillers and the effect on the vulcanization process

In a previous investigation, we observed that in the presence of a conventional vulcanization system, the addition of white rice husk ash (WRHA) to natural rubber (NR) compounds increased the rate of crosslinking and lowered the apparent activation energy (E_a) of the vulcanization reaction more strongly than the other fillers used. In this work, commercial fillers, such as precipitated silica (Zeosil‐175) and carbon black (N762), were partially replaced by black rice husk ash and WRHA. Cure studies were carried out on a TI‐100 curometer at 150, 160, 170, and 180°C, and the overall rates and the E_a's for the vulcanization process were calculated for each compound, with the assumption that vulcanization followed first‐order kinetics. Again, WRHA showed some catalytic effect on the NR vulcanization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1405–1413, 2003     

Cure characteristics and mechanical properties of hydrogenated natural rubber/natural rubber blends

The cure characteristics and mechanical properties of blends consisting of hydrogenated natural rubber (HNR) and natural rubber (NR) blends were investigated. The HNR/NR blends at 50/50 wt ratio were vulcanized using various cure systems: peroxide vulcanization, conventional vulcanization with peroxide, and efficient vulcanization with peroxide. The HNR/NR vulcanizates cured by the combination of peroxide and sulfur donor (tetramethylthiuram disulfide, TMTD) in the efficient vulcanization with peroxide exhibited the best mechanical properties. It was also found that the hydrogenation level of HNR did not affect the tensile strength of the vulcanizates. The tensile strength of the blends decreased with increasing HNR content because of the higher incompatibility to cause the noncoherency behavior between NR and HNR. However, the HNR/NR vulcanizate at 50/50 wt ratio showed the maximum ultimate elongation corresponding to a co‐continuous morphology as attested to by scanning electron micrographs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Vulcanization kinetics of nano-silica filled styrene butadiene rubber

It was shown that the physical filler-polymer and filler–filler interactions, apart from the filler surface chemistry, has a substantial role in controlling the vulcanization kinetics of styrene butadiene rubber filled with nano-silica in a sulfur vulcanization system. Kinetic studies by the oscillating disc rheometer, differential scanning calorimeter, and swelling tests revealed that the vulcanization rate goes through a maximum as loading of silica increases, but conversion in crosslinking continuously decreases as the amount of silica increases. The effect of silica loadings on the vulcanization reactions was linked to the immobilization of rubber chains around particles as well as in a polymer-mediated filler network, which were differentiated by the nonlinear viscoelastic behavior of rubber vulcanizates. By surface modification of nano-silica, the accelerating/decelerating effects of nano-silica on the vulcanization reactions were altered corresponding to the non-linear viscoelastic behavior of the vulcanizates. Therefore, a mechanism was proposed which correlates vulcanization kinetics of rubber to the dynamics of chains influenced by the reinforcing fillers.     

Effect of nano zinc oxide on the cure characteristics and mechanical properties of the silica‐filled natural rubber/butadiene rubber compounds

With the increasing interest in environmental and health issues, legal restrictions, such as European Union (EU) End of Life Vehicle Directives, were strengthened. This led us to incorporate nano zinc oxide (nano‐ZnO), with particle sizes of 30–40 nm and specific surface areas of 25.0–50.0 m²/g, instead of conventional ZnO into natural rubber (NR)/butadiene rubber (BR) compounds to decrease the content of zinc in the formulation. In the unfilled system, only a 20 wt % nano‐ZnO content, compared to conventional zinc oxide content, showed the cure characteristics and mechanical properties of the same level. This was because the increase in the specific surface area of the nano‐ZnO led to an increase in the degree of crosslinking. The effect of nano‐ZnO on the cure characteristics and mechanical properties was more pronounced in the silica‐filled system than in the unfilled system. This was mainly because of the dispersing agent used in the silica‐filled system, which also improved the dispersion of nano‐ZnO. The silica‐filled NR/BR compounds containing 0.3–3.0 phr of nano‐ZnO showed improved curing characteristics and mechanical properties, such as optimum cure time, 100 and 300% modulus, tensile strength, and tear strength compared to the compound with 5 phr of conventional ZnO. The optimum amounts of nano‐ZnO and stearic acid were only 1.0 and 0.1 phr, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of chemically modified waste rubber powder as a filler in natural rubber vulcanizates

Waste rubber powder (RP) was subjected to chemical modification by using different concentrations of oxidizing agents such as nitric acid and 30% hydrogen peroxide solution. This treatment leads to introducing some functional groups onto the surface of RP. The chemically modified RP was incorporated in natural rubber mixes either alone or in combination with carbon black (HAF). The physicomechanical properties of NR vulcanizates obtained were studied and compared to NR vulcanizates filled with untreated RP. It was found that the chemically modified RP improves tensile strength and aging resistance of NR vulcanizates compared with untreated RP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 30–36, 2004     

New binary systems containing TMTD‐amidino phenyl thiourea and CBS–amidinophenyl thiourea for the vulcanization and rheological behavior of natural rubber latex

The use of accelerators in rubber latex is basically different from their use in dry rubber. In the present study, N amidino N'phenyl thiourea (APT) which is more nucleophilic than thiourea was studied as a secondary accelerator along with tetra methyl thiuram disulphide (TMTD) and N‐cyclohexylbenzothiazyl sulphenamide (CBS) in the vulcanization of natural rubber latex. These binary systems were found to be very effective in reducing the vulcanization time. The optimum dosages for this non‐toxic secondary accelerator required were derived. Rheological studies of the compounded latex show that the introduction of APT in these systems does not have adverse effect in processing in comparison with the thiourea systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

羧基丁腈橡胶的硫化性能

用无硫硫化体系、低硫高促进剂硫化体系、普通硫黄硫化体系、过氧化物硫化体系、金属氧化物硫化体系和硫黄／金属氧化物硫化体系对羧基丁腈橡胶（XNBR）进行了硫化,研究了XNBR的硫化性能、物理机械性能、耐老化性能、压缩永久变形和耐油性能。结果表明,采用普通硫黄硫化体系、硫黄／金属氧化物硫化体系所得到的XNBR硫化胶的综合物理机械性能较好;用无硫硫化体系、低硫高促进剂硫化体系和硫黄／金属氧化物硫化体系所得到的XNBR硫化胶的耐老化性能较好;用硫黄／金属氧化物硫化体系所得到的XNBR硫化胶的耐磨性、压缩永久变形较好;用普通硫黄硫化体系和硫黄／金属氧化物硫化体系所得到的XNBR硫化胶的耐油性能较好。