白炭黑胶料混炼工艺探讨

研究GK270N型密炼机混炼排胶温度及氧化锌、防老剂加入顺序对白炭黑胶料密炼工艺性能、硫化特性及物理性能的影响。结果表明，排胶温度为160℃时混炼效果好;氧化锌在一段加入，混炼胶门尼粘度降低明显，定伸应力和抗撕裂性能较好；防老剂在一段加入，混炼胶工艺性能及其硫化胶物理性能最差。     

NH3-modified swelling of silica-filled silicone rubber

The NH₃-modified swelling method was used for fume silica-filled silicone rubber compounds and vulcanizates. The method provides an estimation of the polymer–filler interaction in the system. Bound rubber reduction due to the modified swelling is shown to be dependent on the silica surface silanol content in the compound. The swelling behavior of silica-filled vulcanizates was also studied in an NH₃ atmosphere. The fraction of polymer–filler attachments in the vulcanizates was found not to depend on the particle size of silica and its surface modification, depending only on the total polymer–filler contact area in the system. No relation was found between bound rubber content in a compound and swelling of a filled vulcanizate of the same composition. The strong rubber-to-filler adherence found in toluene changed to nonadherence under NH₃-modified swelling conditions. The NH₃-induced cleavage of silica–silicone rubber attachments was found to be nearly completely reversible. In the silica-filled silicone rubber vulcanizates, the fraction of polymer–filler attachments due to polymer–filler interaction represents a substantial contribution to the total number of network chains.     

Elucidation of segmental relaxations of silica-filled cis-polybutadiene rubber composites

There has been a lot of interest in characterizing polymer chain dynamics of rubber compounds because it is thought to underpin the exceptional mechanical properties of composites. We studied the effect of precipitated silica on segmental mobility of cis-polybutadiene rubber by using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). It was found that the calorimetric glass and melting transitions of silica-filled master batch materials were essentially identical to those of the gum rubber, showing no dependence of silica loading and silane treatment. And, we observed in calorimetric measurement a change in the melting transition step for the vulcanizates. The results were correlated to the change of chemical crosslinks caused by various factors filler agglomeration and adsorption effect that tended to decrease chemical crosslink density and silane modification increased it. The DMA results demonstrated that the second peak in loss modulus versus temperature curve for the quenched vulcanizates was assigned to melting peak, and this peak disappeared at a slow cooling rate, which coincided well with DSC results. Moreover, crystalline parts constrained amorphous regions such that the glass transition temperature was raised for the cooled vulcanizates with high chemical crosslinks.     

硅烷用量对白炭黑填充胶料交联密度的影响

该文描述了硫化过程中添加的游离硫黄在白炭黑-橡胶结合与基质交联间的优劣比较,对含硫官能硅烷偶联剂Si69及Si266的变量进行了两种统计性试验。可以看出,一方面硅烷用量的增加增强了白炭黑-橡胶结合,引起模量提高并有效降低拉断伸长率;另一方面,白炭黑-橡胶结合消耗游离硫黄产生低基质交联密度。由于两种交联反应同时发生,基质和白炭黑-橡胶网状结构之比不能随意变化。为了获得最佳补强效果并满足性能要求,已精确地对硅烷与硫黄的比率进行了调整。该研究的目的旨在深入了解白炭黑填充胶料的补强效果,并对指导怎样使胶料拥有最佳产品性能有很大意义。     

莫来石与沉淀法白炭黑填充丁苯橡胶复合材料的性能比较

在双辊开炼机中将未处理或用质量分数为3%的硅烷偶联剂A-189处理的莫来石粉体加入到丁苯橡胶(SBR)中制成复合材料.研究莫来石的加入量对SBR性能的影响,并与沉淀法白炭黑填充的SBR的性能进行了比较.结果表明,莫来石粉体对SBR表现出半增强特性;与沉淀法白炭黑填充的SBR相比,SBR/莫来石复合材料表现出良好的硫化特...     

Investigation and improvement of the scorch behavior of silica-filled solution styrene-butadiene rubber compound

Effects of different silane coupling agents on scorch time of silica-filled solution styrene-butadiene rubber compounds were studied. The flocculation of silica at high temperature, which was characterized by rubber processing analyzer (RPA) and transmission electron microscope (TEM), has been proved to be an important factor affecting the scorch time of the compounds. In order to prolong the scorch time, the hybrid silane technology, that is, combining different silanes such as bis(triethoxysilypropyl)-tetrasulfide (TESPT) and n-octyltriethoxysilane (OTES) together, was developed to improve silica dispersion and suppress silica flocculation. The results showed that when the content of TESPT is fixed, the increase of OTES can effectively increase the scorch time due to the suppression of silica flocculation while not affecting the polymer crosslinking. This phenomenon is absent for the case where the OTES content is fixed, but the TESPT content is varied because the sulfur atoms in the TESPT molecules will also participate in the vulcanization process, leading to the decrease in scorch time. Through the present study, a connection between silica flocculation and scorch time has been built up, which is important for rubber composite processing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47918.     

硅烷偶联剂对二氧化硅填充硅橡胶界面及性能的影响

研究了硅烷偶联剂六甲基二硅氮烷（HMDS）、KH-570与Si O2增强体系在甲基乙烯基硅橡胶（MVQ）中的应用,同时考察了硅烷偶联剂的种类对MVQ复合材料界面及拉伸性能的影响。结果表明,Si O2经HMDS和KH-570表面处理后与MVQ的界面作用增强。相比于HMDS,含有KH-570的复合材料体系,Si O2能与MVQ分子发生化学作用,因此界面区域的相互作用进一步增强,吸附橡胶分子层厚度从16.065 nm增加到21.217 nm,硫化后复合材料具有更好的拉伸性能。     

Pulsed NMR study on the hydration of poly(acrylic acid) salts

Summary Pulsed NMR was applied to measure the spin-lattice (T₁) and spin-spin (T₂) relaxation times of the equilibrium water absorbed in poly(acrylic acid) lithium salt, sodium salt, and potassium salt. T₁ and T₂ relaxation time curves for the samples of lithium and sodium salts studied showed single phase behavior, but the sample of potassium salt exhibited two-phase behavior, indicating the existence of water fraction of higher mobility.     

Fatty acid benzyl esters as bio-based plasticizers in silica-filled solution-polymerized styrene-butadiene rubber/butadiene rubber composites

Bio-oil based plasticizers have gained great attention in rubber industry as alternatives of petro-based plasticizers with high content of polycyclic aromatic hydrocarbons. In this work, five fatty acid benzyl esters were synthesized by the esterification of fatty acids (lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, which are obtained after hydrolysis of some vegetable oils) with benzyl alcohol. They were further applied as plasticizers in silica-filled solution-polymerized styrene-butadiene rubber/butadiene rubber (SSBR/BR) composites in order to study the structure-property relationship, compared with treated distillate aromatic extract (TDAE) as standard. The composites were studied for their processability, curing, static, and dynamic mechanical properties by developing through compatibility between bio-plasticizers and polymer matrix. The results show that benzyl laurate with suitable hydrocarbon chain length and benzyl oleate with a carbon-carbon double bond have comparatively improved performance compared to TDAE in the silica-filled SSBR/BR composites.     

Studies on peroxide vulcanization of silica-filled EPDM rubber in presence of vinyl silane coupling agent

The effect of vinyltris (2-methoxyethoxy) silane (hereafter referred to as A-172) on peroxide-vulcanization, rubber-filler interaction, network structure and fracture mode of EPDM rubber vulcanizate has been studied by chemical analyses and scanning electron microscopy (SEM). A-172 decreases the Mooney viscosity and increases the Mooney scorch time, thus showing improvement in processibility. Rubber-filler interaction and apparent crosslink density increase in the presence of A-172, which is reflected in the technical properties studied. Analyses of fracture surfaces by SEM show the reduction of hydrophilicity of silica filler and its subsequent improved compatibility with hydrophobic hydrocarbon rubber.     

Pulsed NMR study of elastomeric block copolymer under deformation

Deformation behavior of an elastomeric styrene–butadiene–styrene block copolymer (SBS) is studied by pulsed NMR techniques, and is related to lifetime distributions and the change of the microstructure in the stress relaxation process. By the measurement of spin–spin relaxation time, it is found that polybutadiene (PB) chains in the vicinity of polystyrene (PS) domains come to be in more constrained conformations with stretching than those remote from the domains mainly through the intramolecular interactions, followed by the enlargement of the constrained regions, which reflects the roles of both crosslinks and filler particles in crosslinked rubbers. In the stress relaxation process, however, the mean lifetime for SBS at the critical strain is longer than that at lower strain in contrast with the results for the crosslinked rubbers. It is estimated that the differences between the failure behaviors of SBS and those of the conventional crosslinked rubbers may be mainly caused by the characteristic change of the microstructure (the disruption of the weak interconnections between the spherical PS domains with high energy dissipation) in SBS on deformation, associated with the limited extensibility of the PB chains between the adjacent PS domains. It becomes clear that the pulsed NMR method complements the mechanical measurements with a more precise information on the heterogeneity in the rubbery polymers under deformation.     

Pulsed NMR measurements on polyethylene melts

Summary NMR measurements were carried out for studies on polyethylene fractions in the melt using Hahn's spin echo technique and the MW4 pulse sequence. The decays of transverse magnetization M(t) and the line shape function S(f) are discussed.     

Pulsed field gradient NMR

We show that self-diffusion coefficients derived indirectly from sedimentation or mutual diffusion do not agree with those obtained directly with PFGNMR. We believe that indirect determinations are not valid for random coils at finite concentrations. However the different physical factors governing self-diffusion and sedimentation can be exploited to obtain information on the static and dynamic critical exponents for polymers in semi-dilute solution. We show that such an analysis leads to an anomalously high static index for 110 000 M polystyrene in toluene.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, July 20–23, 1981Presently on leave at Physics Department, University of British Columbia, Vancouver, Canada     

A 13C NMR study of hydroxylated natural rubber

Two methods have been used to introduce hydroxyl groups into natural rubber. In the first method, epoxidized natural rubber was reduced with lithium aluminium hydride or aluminium hydride with the production of a tertiary alcohol. The ¹³C NMR spectrum of this product was assigned in terms of shift factors from model compounds and quantitative analysis of the spectra confirmed that the hydroxylation process of partially epoxidized rubber was a random process. At higher levels of epoxidation, evidence was obtained for the formation of larger rings from adjacent epoxy groups. The second method involved hydroboration of natural rubber followed by oxidation, which was expected to produce secondary alcohol groups, but gave a mixture of secondary and tertiary alcohol groups as shown by the ¹³C NMR spectrum. A reaction scheme was proposed to explain this result.     

Pulsed field gradient NMR study of surface diffusion in mesoporous adsorbents

Surface diffusion of n-heptane in two mesoporous adsorbents with different morphologies of the pore network, namely Vycor random porous glass and porous silicon with linear pores, have been studied using pulsed field gradient NMR. The experimentally obtained diffusivities revealed increasing mobility of guest molecules with increasing surface coverage, indicating heterogeneity of the surface properties. The diffusion studies at different temperatures have further confirmed this hypothesis. The activation energies for surface diffusion turned out to be a function of surface coverage. The experimental results obtained are analyzed using a model of surface diffusion taking account of a distribution of the transition rates.     

Effect of carbon nanotubes with different lengths on mechanical and electrical properties of silica-filled styrene butadiene rubber compounds

Carbon nanotubes (CNTs) having three different lengths of 5, 30, and 100 μm were added to silica-filled styrene butadiene rubber (SBR) compounds in order to investigate the effect of the CNT addition on the dynamic and electrical properties. The amounts of CNTs were 1, 2, 4, and 7 phr, while the amount of silica was set high at 80 phr to clearly demonstrate the performance of the CNTs as fillers. The effect of CNTs on the silica-filled SBR compounds on the tensile properties is not significant, but the addition of longer CNTs with high loading severely deteriorated the dynamic properties, but considerably enhanced electrical conductivity. The medium loading of CNTs in silica-filled SBR compounds is suitable for the improvement of the electrical conductivity without severely sacrificing the dynamic properties.     

Studies on mechanical,rheological, thermal and morphological properties of in situ silica-filled butadiene rubber composites

Silica is introduced in butadiene rubber (BR) in situ by solution sol–gel method at low and high content. This results in uniformly dispersed spherically shaped silica in rubber matrix as revealed from Scanning electron microscopy study. Incorporation of in situ silica imparts moderate reinforcement to BR composite. Mechanical property and silica distribution are eventually improved by using a silane coupling agent as a surface modifier. Thermal, rheological, morphological, mechanical and melting behaviours of the composites are evaluated and analysed in a comparative manner.     

Natural rubber-graft-poly(2-hydroxyethyl acrylate) on cure characteristics and mechanical properties of silica-filled natural rubber composites

The grafting of poly(2-hydroxyethyl acrylate) onto natural rubber (NR-g-PHEA) was used to compatibilize NR composites with silica filler. The NR/silica compounds were prepared with various grafting percentages of NR-g-PHEA (0, 6.5, 10.5, and 14.5%) and fixed amounts of 3 parts per hundred of rubber (phr) NR-g-PHEA and 20 phr silica. The cure characteristics were examined using a moving die rheometer. The physicomechanical properties of NR/silica composites were determined in terms of tensile strength, bound rubber content, and dynamic mechanical analysis. Thermal properties were assessed with thermogravimetric analysis. The results showed that scorch time and cure time tend to decrease with the level of grafting in NR-g-PHEA. The NR-g-PHEA decreased tan δ, whereas bound rubber content in NR/silica compounds increased, which indicates improved silica dispersion in the NR matrix. The mechanical properties improved with level of grafting in NR-g-PHEA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48738.     

Effect of ultrasonic extrusion of star styrene-butadiene rubber on properties of carbon black- and silica-filled compounds and vulcanizates

Extrusion of star styrene-butadiene rubber (SBR) without and with ultrasonic treatment at amplitudes 3.5, 5, 7.5, and 10 μm was carried out. The molecular structure of untreated and treated star SBR was determined. Significant reduction of die pressure was observed during ultrasonic treatment due to the thixotropic and degradation effects. Ultrasonic treatment of star SBR at 3.5 μm created molecules of higher molecular weight via long-chain branching without gel formation. Ultrasonic treatment of star SBR at 5 μm created a small amount of gel. At high ultrasonic amplitudes more gel was generated hindering mixing of star SBR with silica. Extruded star SBR was compounded with carbon black and precipitated silica, with and without silane. It was found that the long-chain branching induced by ultrasonic treatment improved the rubber–filler interaction in precipitated silica without silane, as confirmed by the increase of bound rubber content. The filler–filler interaction was reduced in silica compounds without silane, as indicated by study of Payne effect. The significantly improved rubber–filler interaction and reduced filler–filler interaction led to an increase of the modulus at 100% elongation and tensile strength of SBR/silica vulcanizates. Extensive comparisons were made with earlier study on ultrasonic treatment of linear SBR. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47451.