硫化体系对天然橡胶耐热空气老化性能的影响

研究了硫化体系(CV、EV和SEV)对炭黑填充天然橡胶胶料耐100℃热空气老化性能的影响,并采用化学探测法测试了NR硫化胶老化后交联密度和交联键类型的变化。结果表明,100℃热空气老化后,CV硫化胶力学性能和交联密度均发生明显劣化;EV硫化胶表现出优异的耐100℃热空气老化性能,其力学性能和交联密度变化幅度均明显低于CV硫化胶;SEV硫化胶耐100℃热空气老化性能与CV硫化胶接近。CV硫化胶以多硫键为主,单硫键含量非常低,100℃热空气老化后多硫键含量下降,单硫键含量升高,双硫键基本保持不变;EV硫化胶以单硫键为主,多硫键含量很低,100℃热空气老化后单硫键含量增大,多硫键含量减小,双硫键变化不大;SEV硫化胶中双硫键含量最高,单硫键和多硫键含量基本相同,100℃热空气老化后多硫键含量和双硫键含量均下降,单硫键含量增大。     

硫化剂DCP用量对NBR/EVM并用胶交联密度及力学性能的影响

研究了硫化剂DCP(过氧化二异丙苯)用量对丁腈橡胶(NBR)/乙烯-醋酸乙烯酯橡胶(EVM)共混胶的硫化特性、两相交联密度、物理力学性能以及热空气老化性能的影响。结果表明,随着硫化剂DCP用量的增大,NBR/EVM共混胶的硫化速度和交联密度逐渐增大。与老化前相比,经热空气老化后硫化胶的交联密度增大,经125℃热空气老化后硫化胶的交联密度增大速率逐渐变大,且在DCP用量为1.5份时老化后的硫化胶交联密度增大一倍多。随着硫化剂DCP用量的增大,NBR/EVM硫化胶中NBR相的交联密度逐渐增大、EVM相的交联密度微降,在DCP用量为1.5份时两相交联密度相差最大。与老化前相比,经过热空气老化后硫化胶中NBR相的交联密度明显增大,EVM相的交联密度则变化不大。随着硫化剂DCP用量的增大,NBR/EVM硫化胶的拉伸强度基本保持不变,硬度和100%定伸应力均逐渐增大,拉断伸长率和压缩永久变形均逐渐减小。与老化前相比,经70℃、100℃热空气老化后硫化胶的硬度、拉伸强度、100%定伸应力均增大,而拉断伸长率基本保持不变。经125℃热空气老化后硫化胶的100%定伸应力明显变大,拉伸强度和拉断伸长率均明显减小。     

热空气老化对苯基硅橡胶阻尼特性的影响

研究了不同老化温度(300℃、320℃、330℃、340℃、350℃)下,短时(30 min)热空气老化对苯基硅橡胶(PS5360)硫化胶老化性能的影响。采用低场NMR橡胶交联密度测定仪研究了老化前后PS5360硫化胶的交联密度变化。测试了其在老化前后的物理力学性能变化。依据不同的应用环境,使用动态热机械分析仪分别在20℃和110℃下测量了老化后PS5360硫化胶的动态力学性能。结果表明:随着短时老化温度的提高,PS5360硫化胶在中低频(5~150 Hz)环境下的介质损耗因数逐渐提高,交联密度逐渐降低,物理力学性能逐渐下降。     

防老剂MB用量对CM／EVM共混胶性能的影响

研究了共混比为70／30的氯化聚乙烯（CM）／乙烯一醋酸乙烯酯橡胶（EVM）共混胶中不同MB的用量下,共混胶的硫化特性,热空气老化前后共混胶的力学性能、两相交联密度和动态力学性能。研究表明：随着MB用量的增加,共混胶的硫化特性稍有变化;老化前后,1#共混胶的力学性能及交联密度变化率较高,玻璃化转变温度的变化程度较大;老化前后,5#共混胶的力学性能变化率较低,交联密度变化率较低,玻璃化转变温度的变化程度较小。     

硅烷偶联剂Si69对SSBR/SiO2硫化胶热空气老化性能的影响

研究了SSBR(溶聚丁苯橡胶)/SiO2硫化胶热空气老化过程中,硅烷偶联剂Si69对其力学性能、应力松弛、交联密度及喷霜的影响。结果表明,加入Si69可以提高SSBR/SiO2硫化胶的力学性能、应力松弛系数和交联密度,并随Si69用量的增加而持续提高。加入Si69还可以减小热空气老化过程中硫化胶的应力松弛系数和交联密度的增长率,该增长率随Si69用量的增加而减小。加入Si69可以减轻硫化胶的喷霜现象,硫化胶表面的喷出物主要为白炭黑。     

热空气老化对丁基橡胶交联密度和力学性能的影响

采用热空气老化试验机研究了丁基橡胶（IIR）的老化行为,获得了不同老化温度和老化时间对IIR交联密度和力学性能的影响规律。结果表明,随着老化时间的延长,IIR硫化胶的交联密度先增大后减小,并随老化温度的升高变化幅度较为明显。拉伸强度、定伸应力和硬度均出现类似变化规律,而拉断伸长率先迅速下降后逐渐趋于平缓。     

MG49改性陶土与NR的相互作用

以天甲橡胶ＭＧ４９改性陶土。采用ＩＲ、ＳＥＭ及结合胶质量分数、表观交联密度、界面作用强度表征值、蠕变和力学性能的测定,研究了ＭＧ４９改性陶土与ＮＲ的相互作用及改性效果。结果表明：ＭＧ４９湿法改性陶土提高了混炼胶的结合胶质量分数,增加了材料的表观交联密度,增强了陶土与ＮＲ间界面的作用强度,改善了硫化胶的网络结构,提高了硫化胶的力学性能。     

双马来酰亚胺在ACM橡胶中的应用

研究了N,N－间苯撑双马来酰亚胺（MPBM）对ACM橡胶力学性能、热空气老化性能以及耐热油性能的影响。结果表明：随着MPBM用量增大,ACM硫化胶的100％定伸应力和硬度增大,拉促强度有所提高,拉断伸长率下降,表观交联密度增大,热空气老化性能以及耐热油性能仍可保持较高水平。     

防护体系对NBR/EVM硫化胶交联密度及耐老化性能的影响

在过氧化物硫化剂DCP(过氧化二异丙苯)作用下,研究了防老剂MB(二硫醇基苯并咪唑)用量、防老剂MB/RD(2,2,4-三甲基-1,2-二氢化喹啉聚合体)并用比对NBR/EVM并用胶硫化特性、两相交联密度、力学性能及热空气老化性能的影响。结果表明,随着防老剂MB用量的增大,NBR/EVM硫化胶的交联密度微增,热空气老化后其交联密度增大,并认为是由NBR相交联密度增大造成的。在防老剂MB用量为0.6~1.8份时,交联密度变化率最小。硫化胶的硬度和200%定伸应力均逐渐增大,在防老剂MB用量为1.2份时,其耐热空气老化性能最佳。随着防老剂MB/RD并用体系中RD所占比例的增大,NBR/EVM并用胶的交联密度逐渐减小,操作安全性逐渐变好,硫化速率逐渐减小。在防老剂MB/RD并用比为1.6/0.4和1.2/0.8时,老化前后交联密度、邵尔A硬度和拉伸强度变化最小,其耐热空气老化性能最佳。防老剂MB和防老剂RD并用时具有协同效应,防护效果好。在防老剂MB/RD并用比为1.2/0.8时,随着热空气老化时间的延长,NBR/EVM硫化胶的交联密度逐渐增大,100%定伸应力、200%定伸应力和300%定伸应力逐渐增大。     

耐125℃热空气丁腈橡胶硫化体系探究

分别研究了6种硫化体系(硫黄、硫黄+促TMTD、促TMTD、DCP、DCP+硫黄、DCP+硫黄+促TMTD)对丁腈橡胶硫化特性、力学性能、耐热空气老化性能以及压缩永久变形的影响。结果表明,经125℃×72h热空气老化后,纯DCP硫化胶力学性能变化不大,压缩永久变形最小,但因交联密度太大,硫化胶弹性及动态性能较差,弯折处易产生裂纹,可在125℃静态条件下长期使用。以DCP+硫黄为硫化剂的过氧化物/半有效硫化体系硫化胶综合性能最优,能满足实际使用要求,适宜在125℃动态条件下长期使用。     

RPA分析硫黄用量对天然橡胶动态性能的影响

用橡胶加工分析仪(RPA)分析硫黄用量对NR动态性能的影响。结果表明:不同硫黄用量的混炼胶的动态模量随频率的升高和温度的降低而增加,损耗因子降低;应变超过28%,混炼胶的储能模量下降。不同硫黄用量的硫化胶随交联密度的提高,动态性能对频率的依赖性变小,对应变的依赖性变强;而温度越高,硫化胶的"橡胶弹性"越明显。     

三种微生物脱硫废乳胶及其填充天然橡胶的力学性能比较

利用三种微生物鞘氨醇单胞菌、脂环酸芽孢杆菌和酵母菌对废乳胶(WLR)进行了脱硫再生,考察了脱硫过程中微生物的生长情况以及脱硫前后WLR溶胀和交联密度的变化,并将WLR和脱硫WLR(DWLR)以不同份数填充到天然橡胶(NR)中,对比了DWLR/NR硫化胶和WLR/NR硫化胶的力学性能和交联密度。结果表明,利用鞘氨醇单胞菌脱硫的WLR溶胀值较高,交联密度较低。随着乳胶用量的增加,填充NR硫化胶的拉伸强度和交联密度逐渐降低,扯断生长率逐渐增加。DWLR/NR硫化胶的力学性能明显优于WLR/NR硫化胶,且鞘氨醇单胞菌脱硫的DWLR/NR的力学性能明显优于其它两种微生物脱硫的DWLR/NR硫化胶。     

Effects of hot‐air aging and dynamic fatigue on the structure and dynamic viscoelastic properties of unfilled natural rubber vulcanizates

The effects of hot‐air aging and dynamic tensile fatigue on the network structure and dynamic viscoelastic properties of unfilled natural rubber (NR) vulcanizates were investigated with magnetic resonance crosslink density spectrometry, Fourier transform infrared spectroscopy/attenuated total reflection (FTIR–ATR), and dynamic mechanical analysis. The results showed that there was a carbonyl weak absorption peak at 1723 cm^?1 in the FTIR–ATR spectra of unfilled NR vulcanizates after hot‐air aging; The crosslink density decreased continuously as the aging time increased. The dynamic modulus of an aged specimen declined considerably, and the value of tan δ after 72 h of aging greatly increased. There was a large difference in the FTIR–ATR spectra of unfilled NR vulcanizates before and after tensile fatigue. The peaks at 1597, 1415, and 1015 cm^?1 increased concurrently with the tensile fatigue time. Initial analysis suggested that structures such as conjugated dienes appeared in the network structure. The modulus declined sharply, whereas the value of tan δ increased noticeably, after tensile fatigue. The effects of hot‐air aging and tensile fatigue on the crosslink density and FTIR–ATR spectra of unfilled NR vulcanizates were different, but both affected the viscoelastic properties dramatically. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

低滞后炭黑DZ13对胎面胶物理性能及疲劳破坏行为的影响

采用以天然橡胶(NR)、NR/顺丁橡胶(BR)和NR/BR/溶聚丁苯橡胶(SSBR)为基体的轮胎胎面胶配方,研究低滞后炭黑DZ13对3种硫化胶物理性能和疲劳破坏行为的影响。结果表明:低滞后炭黑DZ13部分替代炭黑N234后,NR,NR/BR和NR/BR/SSBR硫化胶的物理性能变化规律相似,即定伸应力略有增大、拉断伸长率和撕裂强度减小;耐磨性能、耐压缩疲劳性能和耐割口增长性能的变化依赖于基体橡胶;其中NR/BR硫化胶的屈挠疲劳次数提高,但疲劳破坏界面的微观形貌更加粗糙。     

Bis(trifluoromethylsulfonyl)imide Ionic Liquids Applied for Fine-Tuning the Cure Characteristics and Performance of Natural Rubber Composites

The goal of this work was to apply ionic liquids (ILs) with bis(trifluoromethylsulfonyl)imide anion (TFSI) for fine-tuning the cure characteristics and physico-chemical properties of elastomer composites based on a biodegradable natural rubber (NR) matrix. ILs with TFSI anion and different cations, such as alkylpyrrolidinium, alkylammonium, and alkylsulfonium cations, were applied to increase the efficiency of sulfur vulcanization and to improve the performance of NR composites. Thus, the influence of ILs on the vulcanization of NR compounds, as well as crosslink density and physical properties of NR vulcanizates, including tensile properties, thermal stability, and resistance to thermo-oxidative aging was explored. The activity of ILs seems to be strongly dependent on their cation. Pyrrolidinium and ammonium ILs effectively supported the vulcanization, reducing the optimal vulcanization time and temperature of NR compounds and increasing the crosslink density of the vulcanizates. Consequently, vulcanizates with these ILs exhibited higher tensile strength than the benchmark without IL. On the other hand, sulfonium ILs reduced the torque increment owing to the lower crosslinking degree of elastomer but significantly improved the resistance of NR composites to thermo-oxidation. Thus, TFSI ILs can be used to align the curing behavior and performance of NR composites for particular applications.     

Effect of crosslink structures on dynamic mechanical properties of natural rubber vulcanizates under different aging conditions

The effects of crosslink structures on the dynamic mechanical properties (DMPs) of unfilled and carbon black N330‐filled natural rubber (NR) vulcanizates cured with conventional (CV), semiefficient (SEV), and efficient (EV) cure systems and having about the same total crosslink densities were investigated before and after aerobic and anaerobic aging at 100°C. The three unfilled NR vulcanizates cured with the CV, SEV, and EV systems had about the same mechanical loss factor (tan δ) values at about 0°C but showed some apparent differences in the tan δ values in the order EV > SEV > CV at relatively high temperatures of 40–80°C before aging. However, N330‐filled NR vulcanizates gave higher tan δ values than the unfilled vulcanizates and showed little effect of the crosslink types on the tan δ at different temperatures over the glass‐transition temperature (T_g) before aging. Aerobic heat aging increased the T_g and tan δ values of the vulcanizates over a wide range of temperatures from ?80 to 90°C that was mainly due to the changes in the total density and types of crosslinks. The unfilled vulcanizates cured with the CV system showed the greatest change in DMP because of their poor resistance to heat aging. Aerobic heat aging of NR vulcanizates caused a more significant change in the DMP than anaerobic heat aging because of the dominant effect of the oxidative degradation during aerobic heat aging on the main‐chain structure, crosslink structures, and DMPs of the vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 710–718, 2001     

环氧化天然橡胶共交联改性EPDM/NR共混物的性能

将三元乙丙橡胶(EPDM)与环氧化天然橡胶(ENR)共交联改性后,再与天然橡胶(NR)共混,考察了ENR共交联改性EPDM/NR共混胶的硫化特性、硫化胶的物理机械性能、溶胀指数和耐热空气老化性能,并对该硫化胶进行了差示扫描量热分析。结果表明,EPDM经过ENR共交联改性后与NR共混,ENR共交联改性EPDM/NR共混胶的交联程度明显提高,各相达到了同步交联,硫化胶的综合性能得到了显著改善。     

使用核磁共振交联密度仪测试不同方法凝固天然橡胶的交联密度和性能的关系

用核磁共振(NMR)法测定不同方法凝固天然橡胶的交联密度,研究其与性能之间的关系。结果表明,硫化胶的交联密度不仅影响其核磁共振的横向弛豫时间(T1),而且影响其纵向弛豫时间(T2)。随着交联密度大,硫化胶的核磁共振弛豫时间缩短。另外,微生物凝固天然橡胶硫化胶的交联密度、正硫化时刻扭矩和拉伸强度均大于酸凝固天然橡胶硫化胶的。     

Study on variation of structure and properties of natural rubber during accelerated storage

The dynamic variations of molecular structure and properties of natural rubber (NR) during the accelerated storage have been studied. The results showed that, with the prolonging of the storage time, the average molecular weight and the gel content increased, the width index of molecular weight distribution decreased, the gel size increased gradually, but the crosslinking density of gel fluctuated only within a narrow range. Besides, the initial plasticity increased, whereas the plasticity retention index decreased. The studies with thermal analyses and infrared spectroscopy showed that the thermal degradation temperature dropped, the thermal degradation rate increased, and the thermal stability has decreased after the storage of NR. The molecular structure and properties of NR are in a state of dynamic variation during accelerate storage. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1779–1783, 1998     

促进剂种类对NR硫化胶动态性能的影响

探讨促进剂NS、CZ、DZ对天然橡胶(NR)硫化胶动态性能的影响。结果表明,由不同的促进剂得到的硫化胶的交联密度不同,硫化胶的动态性能对频率、温度和应变的依赖性也不完全相同。由NS和CZ得到的硫化胶的交联密度较高且相近,其储能模量(G′)随频率和温度的升高而增加的变化趋势几乎重合,但在较低的应变下硫化胶的G′随应变振幅的提高而降低;而由促进剂DZ得到的硫化胶,由于交联密度较低,其G′随温度的升高而略有增加。