Non-invasive headspace measurement for characterizing oxygen-scavenging in polymers

A non-invasive headspace analysis method to measure rate and amount of oxygen uptake in oxygen-scavenging polymers is presented. Oxygen uptake data for metal-catalyzed poly(1,4-butadiene) at 30 °C are provided to illustrate the method. These data were obtained by measuring oxygen headspace concentration above the scavenging polymer with an OxySense^® 200T non-invasive oxygen sensor, and, for comparison, oxygen uptake was measured with an analytical balance. Excellent agreement was observed between these two independent experiments.     

The melting process and the rigid amorphous fraction of cis-1,4-polybutadiene

A thorough analysis of the melting behavior of cis-1,4-polybutadiene (cis-PBD) is detailed in this contribution. Isothermal crystallization at −26 °C, followed by cooling, provides a three-phase structure composed of a mobile amorphous fraction equal to 0.41₃, a crystallinity of 0.27₇, and a rigid amorphous fraction of 0.31₀. Similar to many other polymers, cis-PBD displays multiple melting after isothermal crystallization, and up to three main endotherms can be evidenced by calorimetry, in dependence of the scanning rate. The results of conventional and temperature-modulated calorimetry analyses presented in this contribution suggest a link between multiple melting and devitrification of the rigid amorphous fraction in cis-PBD. The small endotherm located a few degrees above the crystallization temperature appears to be caused by concurrent partial mobilization of both the crystal and the rigid amorphous portions. Additional partial mobilization of rigid amorphous segments seems to take place at around −11 °C, and it is only above this temperature that large reorganization of the crystal phase becomes possible, allowing partial melting and recrystallization/annealing/crystal perfection.     

顺丁橡胶用量对官能化溶聚丁苯橡胶/顺丁橡胶

考察了顺丁橡胶用量对官能化改性溶聚丁苯橡胶与顺丁橡胶并用作为胎面胶时的硫化特性、加工性能、物理机械性能及动态力学性能的影响。结果表明,随着顺丁橡胶用量的增加,并用胶的网络化程度增强,硫化进程加快,填料的分散性得以提高,但其静态力学和动态力学性能均有一定程度的损失,其中顺丁橡胶用量为20份（质量）时官能化改性溶聚丁苯橡胶的抗湿滑性能降低了50%左右。     

Interaction of n-alkanes with crosslinked cis-1,4-polybutadiene

Permeation of n-alkanes through cis-1,4-polybutadine crosslinked using conventional, efficient, and peroxide vulcanizing systems was studied by a gravimetric method. Four alkanes from n-hexane to n-nonane were used. In n-octane, the studies were conducted in the temperature range of 27–70°C.The sorption data was used to estimate the diffusion and permeability coefficients, the activation energy for diffusion and permeation, the entropy and enthalpy of sorption, polymer–solvent interaction parameter, and the degree of crosslinking. The various parameters estimated indicate that permeability of the membranes depends more on the degree of crosslinking than on the nature of crosslinks. Increase in permeant chain length was found to lower permeability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2404–2413, 2001     

制备工艺条件对铝阳极氧化膜膜厚度的影响

采用阳极氧化法制备了Al2O3-Al一体型多孔氧化铝膜,考查了制备工艺条件对氧化膜厚度的影响。结果表明,随着氧化电流密度、氧化时间、电解液浓度等参数的增加,氧化膜厚度亦随之增加。SEM研究结果表明,氧化膜由内层致密的阻挡层和外层的多孔层两部分组成。     

Effect of film thickness, blending and undercoating on optical detection of nitroaromatics using fluorescent polymer films

In this work, using a fluorescent poly(phenylene ethynylene) containing the rigid pentiptycene and large cholesteryl ester pendent groups, the fluorescence quenching properties of the polymer thin films in response to vapor of 2,4-dinitrotulene (DNT) have been investigated by varying the film thickness, applying an undercoating and blending with another polar polymer. A significant change in fluorescence intensity (51% in 60 s) in response to DNT vapor exposure at ambient temperature was achieved when the polymer film coated on glass plate was about 2 nm in thickness. In comparison with the film of polymer alone, the film undercoated with (3-aminopropyl)triethoxysilane and the film of polymer blend containing a non-fluorescent polymer showed additional 18.5% (in 20-s exposure) and 18.7% (in 5-min exposure) decrease in fluorescence intensity, respectively. The use of polymer or polymer blend coated on optic-fiber tip for detection of DNT vapor has also been demonstrated.     

Determination of ethylene-propylene rubber in crosslinked blends with 1,4-polybutadiene

Crosslinked blends of ethylene-propylene rubber (EPR) and 1,4-polybutadiene (BR) were investigated by metathesis degradation of the BR component; the percentage of EPR was determined by weighing the polymeric residue. The metathesis reaction was carried out with an excess of 1-octene in the presence of the catalyst WCl₆/(CH₃)₄Sn. In crosslinking with dicumyl peroxide, the best results were obtained with 10 to 30 wt.-% of EPR and medium crosslinking degrees. Analysis of sulphur vulcanizates (received with the accelerator N-cyclohexyl-2-benzothiazyl sulphenamide) gave tolerable results only for low sulphur contents (1.5 wt.-%). Determination of EPR was also possible in non-crosslinked blends with BR.     

Effect of wall slip on blown film thickness distribution

One of the most important materials for blown film is high‐density polyethylene (HDPE) with wide molecular weight distribution. First, we computed a wall stress at the entrance of a spiral groove in a particular die during blown film processing on a particular condition, to which a similar condition is widely utilized in a film works. The computed value is about 170 kPa, while the HDPE melt slips at die wall at stresses above approximately 50 kPa. The stress of 170 kPa is sufficiently large for the slip occurrence of the melt. Then, we investigated the effects of wall slip and melt visosity on film thickness distribution in the circumferential direction; the distribution tends to decrease with decreasing wall slip and melt viscosity. This tendency is explained by considering flow distribution in a spiral mandrel die and polymer melt flow characteristics.     

低顺式聚丁二烯橡胶的生产技术进展及开发方向

综述了低顺式聚丁二烯橡胶的生产技术进展及科研开发状况,提出了国内低顺式聚丁二烯橡胶的科研开发方向。     

Thermal crosslinking of cis-1,4-polybutadiene at ultrahigh pressures

cis-1,4-Polybutadiene (BR) samples, in the absence of crosslinking agents, were simultaneously compressed by ultrahigh pressures (>4.0 GPa) and annealed between 25 and 180°C. The BR samples were crosslinked when the annealing temperatures were above 100°C. The Vickers microhardness of the treated BR increased and the extent of swelling decreased rapidly as the annealing temperature increased, indicating that the crosslinking density increased. Solid-state carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy results showed that some C=C bonds in the BR were opened to form the crosslinking network structures with C—C linkages and that a partial cis–trans isomerization took place during the treatments. Differential scanning calorimetry studies revealed that the glass transition temperature increased and the crystallinity decreased as the annealing temperature increased. When the annealing temperature exceeded 140°C, the treated BR samples lost their rubbery elastic characteristics completely and became brittle materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2131–2140, 1998     

Effect of Y concentration and film thickness on microstructure and electrical properties of HfO2 based thin films

In this work, we introduced a simple solution processing method to prepare yttrium (Y) doped hafnium oxide (HfO₂) based dielectric films. The films had high densities, low surface roughness, maximum permittivity of about 32, leakage current < 1.0 × 10^?7 A/cm² at 2 MV/cm, and breakdown field >5.0 MV/cm. In addition to dielectric performance, we investigated the influence of YO_1.5 fraction on the electronic structure between Y doped HfO₂ thin films and silicon (Si) substrates. The valence band electronic structure, energy gap and conduction band structure changed linearly with YO_1.5 fraction. Given this cost-effective deposition technique and excellent dielectric performance, solution-processed Y doped HfO₂ based thin films have the potential for insulator applications.     

氯化顺丁橡胶的合成及基本性能

在300t/a氯化顺丁橡胶装置上利用顺丁橡胶和氯化剂合成出氯化顺(CBR）以及不同反应时间，碱胶比和碱浓度对氯化反应的影响，研究了CBR胶液的流变特性和CBR的基本性能。     

Effect of long branching and strain-induced crystallization of cis-1,4-polybutadiene observed in nonlinear viscoelastic behavior

The effect of long branching on the deformational behavior has been examined for four commercial high cis-polybutadienes with particular interest as to its implication on their processability. The techniques used were oscillatory shear measurements at small deformation and tensile stress-strain measurements at large deformation. In the shear measurements (linear behavior), the temperature dependence of the shift factor in the time-temperature superposition is related to the degree of branching obtained from dilute solution viscosity. In the tensile measurements (nonlinear behavior), the rubbers showed either strain-hardening or strain-softening. The difference was not related to the degree of branching determined by dilute solution viscosities. This means that the dilute solution viscosity is not an adequate means to explain the processability difference of the rubbers. The branch length, although the absolute value is unknown, is characterized as short or long on the basis of the strain-softening or strain-hardening behavior. Both small shear and large elongational measurements are necessary for characterization of branching pattern and processability. Rubbers with relatively short branches (strain-softening type) or with the smallest amount of long-branching (non-strain-hardening type) were found to strain-crystallize most easily. The absence of strong resistance to stretching is the apparent reason for the ease of crystallization. © 1996 John Wiley & Sons, Inc.     

壬基酚聚氧乙烯醚接枝顺丁橡胶的研制

探讨以过氧化二异丙苯为引发剂，壬基酚聚氧乙烯醚(环氧乙烷分子数为10)为接枝物，采用熔融混炼法制备壬基酚聚氧乙烯醚接枝顺丁橡胶的最佳因子组合。结果得出，熔融混炼法制备壬基酚聚氧乙烯醚接枝顺丁橡胶的最佳因子组合为：壬基酚聚氧乙烯醚用量2份，过氧化二异丙苯用量3份，反应温度150℃，反应时间4min；壬基酚聚氧乙烯醚接枝顺丁橡胶的润湿性显著优于BR。     

顺丁橡胶溶液的分离技术进展

简述了国内外顺丁橡胶溶液的釜式凝聚，塔式凝聚，直接干燥法和相分离法等的发展概况。     

Kinetics of graft polymerization of styrene on cis-1,4-polybutadiene

By measurements of polymerization rate, grafting efficiency and number-average molecular weight of free and grafted polystyrene, the α-dicumyl peroxide initiated polymerization of styrene on cis-1,4-polybutadiene at 100°C and at low extents of reaction was studied. The polymerization rate and the polystyrene molecular weights decreased with the rubber content of the solution. The grafting efficiency was found to be substantially independent of the peroxide concentration, but to increase with rubber content. A rigorous mathematical model of the reaction was developed, from which it has been possible to confirm the proposed mechanism and to establish the value of many kinetic constants.     

低相对分子质量反式-1,4-聚丁二烯的环氧化改性

采用以汽油为溶剂的预制过氧乙酸法和二甲苯为溶剂的过氧甲酸原位法,对低相对分子质量反式-1,4-聚丁二烯(LMTPB)进行了环氧化改性。通过核磁共振仪分析了环氧化LMTPB的结构,测定了环氧度,对化学滴定法测定的环氧度进行了修正。并研究了反应条件对环氧化LMTPB环氧度的影响。结果表明,LMTPB发生了环氧化反应,以环氧度为16·79%作为拐点,得到2个不同的线性回归校正方程。预制过氧乙酸法合成的环氧化LMTPB的环氧度较低,小于30%;过氧甲酸原位法合成的环氧化LMTPB的环氧度最高可达80%。温度和时间对环氧化反应的影响随着具体反应条件和反应体系的不同而不同,但LMTPB环氧化反应温度不宜超过45℃,反应时间不大于4h。环氧化LMTPB的环氧度随溶剂极性的增加而增加。     

不同粒径二氧化钛对顺丁橡胶/二氧化钛复合材料性能的影响

分别采用7 种不同粒径的二氧化钛制备了顺丁橡胶/二氧化钛复合材料,通过核磁共振交联密度仪、橡胶加工分析仪等研究了二氧化钛的粒径对其硫化特性、交联密度、物理机械性能和动态力学性能的影响。结果表明,在顺丁橡胶中填充纳米级二氧化钛后,复合材料的正硫化时间比填充微米级二氧化钛者明显延长,且前者的拉伸强度可达到纯顺丁橡胶的6 倍; 当二氧化钛的粒径为20 nm 和50 nm时,顺丁橡胶/二氧化钛复合材料的损耗因子、储能模量和损耗模量要远大于填充微米级填料者,且呈现出明显的Payne 效应。     

顺丁橡胶装置回收单元的改造

介绍了顺丁橡胶装置丁二烯回收单元的技术改造情况,改选后回收单元处理能力提高５８．５％,能耗降低１０．６４％,回收丁二烯可直接作为丁苯聚合的单体。     

Toughening mechanisms of rubber modified thin film epoxy resins

An epoxy terminated polybutadiene (ETPB) was synthesized and utilized to enhance the toughening of an epoxy system, in both bulk and coating states. In the first step, the fracture energy of the modified samples was determined using a single edge notched type specimen in a three point bending (SEN3PB) geometry. The effective toughening mechanisms of bulk epoxy specimens were examined using scanning electron microscopy (SEM). The results showed that plastic void growth, cavitation and shear yielding mechanisms were the main toughening mechanisms of the bulk epoxy systems. In the next step, mechanical properties (i.e. impact resistance, flexibility, cupping resistance and hardness) and adhesion of the thin film specimens were evaluated in accordance to the amount of synthesized ETPB. The results showed that the mechanical properties of the ETPB modified epoxy resins considerably improved. In all cases, it was found that the improvement of the mechanical properties reached a maximum at 7.5 wt.% and then began to decrease with further increase in ETPB content. The effective toughening mechanisms in the modified thin films were also examined using SEM and compared to the bulk types. In contrast to the bulk types, the results showed that crack arresting and shear yielding were active mechanisms in thin films. The contribution of these mechanisms led to the improvement of adhesion and mechanical properties by energy dissipation.