Amphiphilic particulate phase semi-interpenetrating polymer networks based on recycled rubber matrix

The goal of this study is to enable the utilization of recycled rubber particles in aqueous media by producing amphiphilic particulate phase semi-interpenetrating polymer networks (PPSIPNs). Rubber granulates obtained from post-consumer rubber items were pulverized into fine particles using a solid state shear extrusion (SSSE) process. Reaction mixtures composed of toluene, acrylic acid (AA) monomer and azobisisobutyronitrile (AIBN) as an oil-soluble initiator were prepared and used to impregnate the produced rubber particles. Toluene was added as a co-swelling agent to induce more swelling of the rubber particles and, consequently, enhancement in the absorption of AA in the rubber network. The swollen particles were introduced into a micro-domain suspension polymerization reactor where the ionic strength of the aqueous phase was sufficient to prevent desorption of AA from the particles during the reaction. This resulted in formation and interpenetration of hydrophilic poly(acrylic acid) in the intermolecular structure of hydrophobic rubber network. The resulting composite particles are water dispersible and suitable for use in a variety of aqueous applications such as, additives to waterborne emulsions and vehicles for wastewater treatment.     

Good dispersion of hydrophilic nanoscale calcium carbonate particles in nitrile butadiene rubber matrix

Using the industrial technologies of rubber latex irradiation, hydrophilic nanoscale calcium carbonate (HNCC) slurry preparing and spray drying, we have prepared a novel ultrafine full-vulcanized powder nitrile butadiene rubber (UFPNBR)/HNCC nanocompound, in which the UFPNBR particles and HNCC particles are isolated and adhered to each other. When the UFPNBR/HNCC nanocompound powder is mixed with crude NBR, UFPNBR particles are easily dispersed well in NBR matrix because of their good compatibility, thus the HNCC particles are also dispersed in NBR matrix because of the carrier aidance of UFPNBR particles in 7 phr HNCC loading range, then the novel NBR/UFPNBR/HNCC ternary nanocomposites is fabricated. Compared with NBR/organic reagent-treated HNCC (ONCC) binary composites, the NBR/UFPNBR/HNCC ternary nanocomposites has shorter vulcanization time and better properties of abrasive resistance, oil resistance, dynamic compression properties and flame retardancy in fire.     

Rubber toughening of an amorphous polyamide by functionalized SEBS copolymers: morphology and Izod impact behavior

Rubber toughening of an amorphous polyamide (Zytel 330) using combinations of triblock copolymers of the type SEBS and a maleic anhydride functionalized version, SEBS-g-MA, was investigated and the results compared with those of nylon 6 and nylon 66. The effects of rubber content and the type of extruder on the morphology, Izod impact behavior and the ductile-brittle transition temperature were explored. The shape and sizes of the rubber particles in blends with this amorphous polyamide were found to be more similar to those in nylon 6 than in nylon 66 blends. The twin screw extruder produced smaller particles with a more narrow distribution of sizes than the single screw extruder. Higher rubber contents generally yielded tougher blends; there is a critical rubber particle size above which the ternary blends are brittle at 20 wt% total rubber. The ductile-to-brittle temperature was found to decrease with increased rubber content and decreased rubber particle size. In general, the trends for this amorphous polyamide are rather similar to those reported earlier for semi-crystalline nylon 6 and nylon 66.     

CM和HDPE对再生橡胶物理机械性能的影响

研究CM和HDPE对再生橡胶物理机械性能的影响。结果表明,再生橡胶的门尼粘度随着CM用量的增加而降低,随着HDPE用量的增加而增加。再生橡胶的拉伸强度和拉断伸长率随着CM和HDPE用量的增加逐渐增加;扫描电镜研究表明,添加CM的再生橡胶硫化胶的拉伸断面相对平整,断层更均匀。综合比较当CM用量为8phr时,再生橡胶的综合性能最佳。     

废轮胎橡胶粉在自粘聚合物改性沥青防水卷材中的应用探究

本文探索了采用橡胶粉制备自粘聚合物改性沥青防水卷材的可行性及影响因素。结果表明采用20%的60目橡胶粉可以制备满足GB23441-2009要求的自粘聚合物改性沥青防水卷材。由于橡胶粉交联态属性限制了分子链运动能力,不能充分发挥线性化橡胶的特性。为充分实现橡胶粉中橡胶特点,本文探索了脱硫胶粉用于制备自粘聚合物改性沥青防水卷材可行性。结果表明采用脱硫降解程度（活化度）在50%左右的脱硫胶粉可用于制备性能优异的防水卷材。适宜的配比为（以沥青为100质量份计）50%的脱硫胶粉、6% SBS以及60%滑石粉。由于活化胶粉中的小分子组分与相容剂、线性化大分子橡胶组份以及甲苯不可溶物与SBS作用机理类似,上述共同作用可替代传统方案中的相容剂、橡胶粉以及部分SBS,并得到优异的综合物理性能     

Effects of high hydrostatic pressure on the mechanical behavior of a crystalline polymer–polyoxymethylene

The true stress-true strain behavior of polyoxymethylene, n(-CH₂O), as an example of a bulk semi-crystalline polymer, has been investigated for constant hydrostatic environmental pressures from 1 atmosphere to 8 kilobars with the principal objectives of elucidating the factors controlling flow and fracture. Experiments were conducted in uniaxial tension at room temperature and constant strain rate. The tensile observations were supplemented by measurements of bulk compressibility and stress relaxation behavior at pressure. In contrast with metals and inorganic compounds, the modulus, yield stress and fracture stress of POM increase strongly with pressure by a factor of approximately three at 8 kilobars. The modulus increase is shown from the stress relaxation measurements to be associated with a pressure-induced increase in the β-transition temperature which points to the potential usefulness of the concept of pressure-temperature super-position of mechanical behavior. The characteristics of the pressure dependence of the yield stress demonstrate that yield criteria based on continum mechanics considerations, including the Mohr or Coulomb-Navier criterion, are not valid for general deformation (non-plane strain) conditions in this polymer. The concept of a critical volume change determining the initiation of yielding is suggested to be applicable to semi-crystalline polymers. Comparison with analogous changes in yield stress with temperature points to an increasing contribution to the control of yielding by the initially disordered regions with increasing pressure or decreasing temperature. The fracture behavior observed at pressure eliminates the concepts of a critical stress as a fracture criterion for POM and of a simple reduction in normal stress at points of stress concentration as the principal effect of the applied pressure on fracture.     

Preparation of composites with globular carbon nanoparticles distributed in an amorphous carbon matrix

Carbon composite materials based on nanoglobular carbon distributed in the volume of a porous carbon matrix were prepared. A reactive polymer with a conjugated system??polyvinylene chloride, which is formed upon the dehydrochlorination of chlorinated polyvinyl chloride, a carbon-chain perchloropolymer??was used as the precursor of porous carbon. Globular carbon, which was prepared by the thermal oxidative pyrolysis of heavy catalytic cracking gas oil, was dispersed in the reaction medium in the synthesis of polyvinylene chloride. The thermal treatment of the resulting compositions in an atmosphere of CO₂ to 900°C led to the formation of carbon-carbon micro-mesoporous nanocomposites, as confirmed by transmission electron-microscopic data and pore structure parameters determined using an adsorption method. It was found that nanoglobular carbon exerted a clearly pronounced nucleating effect on the formation of a carbon structure from a polymer precursor.     

螺杆泵定子橡胶力学试验及本构模型研究

对螺杆泵定子橡胶材料分别进行不同温度下常规与油浸介质下的单轴拉伸与平面剪切试验。基于试验数据,运用ABAQUS软件,对常规与油浸定子橡胶不同温度下的单轴拉伸与平面剪切组合的应力-应变状态分别采用M-R,Yeoh,Ogden,A-B和VDW五种本构模型进行拟合对比分析,确定出拟合效果较好的螺杆泵定子橡胶材料本构模型为Ogden模型且50℃下模型参数较优。     

Contribution of physico-chemical properties of interfaces on dispersibility, adhesion and flocculation of filler particles in rubber

Reinforcing fillers are added to elastomeric compounds to improve and adjust several mechanical, dynamical, tribological, etc. properties with respect to different applications, i.e. for automotive tires, or technical rubber goods. Carbon black and precipitated silica are widely used as rubber reinforcing fillers; however, some new classes of nanosized substances like organophilic modified clay or carbon nanotubes are presently intensive studied as possible future filler systems in combination with carbon black or silica.An important parameter for the dispersibility and compatibility of the filler in the polymer matrix of rubber compounds is the surface energy and surface polarity of the solid filler particles. Therefore, we systematically measured and compared the dynamic contact angles of a collection of different filler types (carbon blacks, silica, carbon nanotubes and organoclays) using the Wilhelmy method, whereby the particles were fixed as a thin layer at a double-sided adhesive tape. From the contact angle values the polar and disperse part of the surface energies of the filler particles were calculated by fitting Fowkes formula. For an estimation of the compatibility of the fillers with different types of rubber polymers we additionally analyzed the surface energy and polarity of the gum (unfilled) elastomers. From the evaluated surface energies and polarities, thermodynamic predictors for the dispersibility (enthalpy of immersion), the adhesion between filler particles and polymer matrix in the nanocomposite, and for the flocculation behaviour of the particles in a rubber matrix (difference in the works of adhesion) were derived. These thermodynamic predictors improve considerably the compounding process of novel rubber nanocomposites with respect to target-oriented adjustment of rubber properties.     

Influence of fillers on the mechanical response of an amorphous liquid‐crystalline polymer

A semirigid and amorphous commercial liquid‐crystalline copolyester (Rodrun) was filled with mica and calcium carbonate (up to 25 wt %) by direct injection molding. The fillers led to decreases in the processability, as observed by torque increases, but maintained the thermal resistance of Rodrun. The effects of the two fillers on the modulus of elasticity, ductility, and tensile strength were the same or very similar. The decrease in the tensile strength (20% for a 10% filler content) was compensated by a generally slight increase in the modulus of elasticity, whatever the filler content was. This balance of properties found in these new liquid‐crystalline‐polymer‐based materials and the important savings that the fillers bring may spread the applications of these materials' matrices. © 2003 Wley Periodicals, Inc. J Appl Polym Sci 88: 998–1003, 2003     

Effects of primary and quaternary amine intercalants on the organoclay dispersion in a sulfur-cured EPDM rubber

The effects of primary and quaternary amine modified montmorillonite (MMT) on the nanocomposite formation in an ethylene/propylene/diene rubber (EPDM) were studied. The organoclay was introduced in 10 parts per 100 rubber (phr) amount in the related recipes. X-ray diffraction spectra (XRD) were recorded in various stages of their processing in order to get information about the intercalation process. The curatives found to play a crucial role, as they promote the intercalation/exfoliation phenomena. Incorporation of MMT modified with octadecylamine (MMT-PRIM) in the EPDM and its more polar version (contains maleic anhydride grafted EPDM, EPDM-MA) resulted in intercalated and exfoliated structures, respectively. Deintercalation of the clay (collapse of the layers), generated in both EPDM and EPDM-MA during vulcanization, was attributed to the reactivity of the PRIM and to its ability to participate in complex formation with the curatives (vulcanization intermediates). This explanation was supported by the non-collapse of the MMT layers when the less reactive modifier, viz. octadecyltrimethylamine served as MMT intercalant (MMT-QUAT). In the latter case the corresponding nanocomposite contained mostly intercalated clay layers based on XRD and transmission electron microscopic (TEM) results.     

Characterization of the effect of the filler dispersion on the stress relaxation behavior of carbon black filled rubber composites

In the present work a new evaluation method for the characterization of the stress relaxation behavior of rubber-carbon black (CB) composites is presented. Using the chart of the online measured electrical conductance received from the recording equipment in the mixing chamber different rubber-CB composites with well defined state of the CB network have been produced for the stress relaxation investigation. The development of CB dispersion degree and the rubber-layer bonded on the CB surface have been characterized systematically using the method of the online measured electrical conductance and the thermogravimetric analysis of rubber-filler gel. The analysis of the stress relaxation curves is based on the division of the initial stress into several stress components and the consideration of the structure of the composites as a combination of different networks. The contribution of the stress component to the corresponding network is the focus of the present work. Based on the systematic variation of material parameters and test conditions we could divide the applied stress into six stress components which are originated from the rubber matrix and CB. It is obvious that the debonding of the rubber-layer from the CB surface and the collapse of a part of the CB network can be described by the relaxing stress component Δσ^{CB(rubber-layer)} and Δσ^CB(network), respectively. The non-relaxing stress components σ_∞^{CB(rubber-layer)} and σ_∞^CB(network) are dependent on the amount of the time-stable bonding in the rubber-layer and the stable part of the CB network. The mechanical performance of the composites and especially the time and temperature dependent mechanical behavior could be specifically modified by CB addition.     

胶料预处理对补强硅橡胶性能的影响

本文研究了胶料预处理的不同方式对硅橡胶补强的影响。结果表明：无论含羟基硅油与否,170℃预处理硅橡胶的拉伸强度最高,放置处理试样的拉伸强度介于未处理和170℃预处理之间;胶料预处理与否对不含羟基硅油的硅橡胶硬度没有影响。含羟基硅油的硅橡胶中,170℃预处理的试样硬度最低,未处理的试样硬度最高。含羟基硅油的硅橡胶断裂伸长率变化不大。不含羟基硅油的硅橡胶断裂伸长率为170℃预处理的试样最低。     

Effects of cure levels on adhesion between rubber and brass in the composites made up of rubber compound and brass-plated steel cord

The adhesion between rubber compound and brass-plated steel cord of rubber-brass composites with different cure levels was investigated in relation to the formation and growth of their adhesion interphase examined with AES spectroscopy. The optimum-cured adhesion sample showed a maximum pullout force, but the pullout forces of samples under-cured and over-cured were low. The adhesion property of under-cured adhesion samples enhanced with humidity aging due to further curing of rubber and supplementary growth of the adhesion interphase. Cure level exhibiting good adhesion was discussed based on the composition and structure of the adhesion interphase and the crosslinking density of the rubber layer attached to the interphase. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University (Gon Seo).     

Effect of the composition of structured rubber particles on the toughness of poly(methylmethacrylate)

Composite natural rubber (NR) and monodisperse poly(n-butylacrylate) (PBuA) based latex particles were tested as possible impact modifiers for a poly(methylmethacrylate) (PMMA) matrix. A continuous extrusion process was used for the incorporation of wet latexes directly into a twin-screw extruder. All latexes had been coated by a PMMA shell. Furthermore, polystyrene (PS) subinclusions were introduced into the NR core. The impact resistance of the prepared PMMA blends can be most effectively improved by NR particles containing a large weight fraction of compatibilising PMMA in the shell. The degree of crosslinking of the shell polymer has to be restricted. PBuA based latex particles of 180 nm in size are ineffective to toughen the PMMA matrix. The degree of grafting of the NR phase in core–shell particles containing PS subinclusions is not crucial. Scanning electron microscopy was used to analyse the failure processes in composite rubber particle toughened PMMA blends at fast (impact conditions) and slow (tensile testing) deformation speeds.     

Size effect on mechanical properties of micron-sized PS-DVB polymer particles

A nanoindentation-based flat punch method has been developed to determine the stress-strain behaviour of single micron-sized Ugelstad polystyrene-co-divinylbenzene (PS-DVB) particles in compression. Five groups of particles with identical chemical compositions but different diameters have been tested. The diameter of the PS-DVB particles varied from 2.6 μm to 25.1 μm. Constant relative deformation rate has been applied with two maximum strain levels of 5% and 10%. Results show that the particle compressive stress-strain behaviour is strongly size-dependent. The smaller the particle size is, the stiffer the particle behaves. Analyses indicate that the pre-load and adhesion during the flat punch test play a minor role on the size effect. The presence of a core-shell structure can possibly be a main contribution to the size effect. Finite element analyses have been carried out to demonstrate this surface shell effect.     

Effects of polymer matrix and processing on the conductivity of polymer blends

The influence of different hosts, processing conditions and conducting fillers on the percolation threshold (Φ_c) of the resulting conducting blends was investigated. Results indicate that microscopic properties, such as the dipole moments of the side‐groups, and distribution of these groups on the host polymer backbone govern the strength of host–filler interactions, and to a large extent, the value of Φ_c, rather than macroscopic properties such as surface tension. The grade of carbon black used in this experiment was found to be polar in nature and it resulted in lower values of Φ_c with the polar hosts, contrary to published literature. In general, melt blending has been shown to result in higher values of Φ_c when compared to hot pressing alone. In the latter method the conductive filler was found to be isolated at the grain boundaries of the polymer host, resulting in the formation of continuous conducting pathways at low filler concentration. © 2001 Society of Chemical Industry     

橡胶材料对甲醇汽油的抗溶胀性研究

甲醇作为一种性能优良的替代燃料,其对橡胶材料具有很大的溶胀危害,这在很大程度上制约了甲醇汽油的发展。选取汽车上常用的几种橡胶材料分别进行汽油和甲醇汽油的溶胀试验,分析出可用于甲醇汽油上的抗溶胀性较好的橡胶材料。     

Effects of short fiber tip geometry and inhomogeneous interphase on the stress distribution of rubber matrix sealing composites

The normal and interfacial shear stress distributions with flat fiber tip of short‐fiber‐reinforced rubber matrix sealing composites (SFRC) compared with the shear lag model were investigated by using the finite element method (FEM). The results indicate that stress values do not agree with those calculated by the shear lag model. The effect of different geometrical shapes of fiber tip on the stress distributions of SFRC was also investigated. The geometrical shapes of fiber tip under present investigation are flat, semi‐elliptical, hemispherical, and circular cone, respectively. The results show that the hemispherical fiber tip transfers the load with less stress concentration and is contributed to controlling the interface debonding failure more effectively than other shapes of fiber tip. Further study on the effect of the inhomogeneous interphase properties on the normal and interfacial shear stresses of hemispherical fiber tip was also conducted. The results indicate that the normal stress increases with the increase of the interphase thickness and interfacial shear stress remains unchanged, and the normal stress values of SFRC with interphase are higher than those without interphase. The interphase elastic modulus has no influence on the stress distributions along the direction to the fiber axis. The stress distributions along the radial direction in the interphase end are largely dependent on the interphase elastic modulus, and the interfacial shear stress is larger than the normal stress, which reveals that a significant part of the external load is transferred from the fiber to the matrix through shear stresses within the interphase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41638.     

Effect of maleimide curing on mechanical properties of ground tyre rubber/waste polypropylene blends

Abstract

Blends of ground tyre rubber and waste polypropylene with a maleimide curing system (50∶50 blends of ground tyre rubber/waste polypropylene) were prepared in a Haake Rheocord Polylab System, at 180°C and 90 rev min^–1 for 5 min. The curing agent and the activator used were N,N′-meta-phenylene dimaleimide (HVA-2) and di(tert-butylperoxyisopropyl) benzene (DTBPIB) respectively. The HVA-2 level varied from 0 to 5 parts per hundred parts (pphp), while the DTBPIB level varied from 0 to 1 pphp. Melt viscosity, tensile strength and elongation at break showed an increase with HVA-2 content, while the impact energy showed an optimum at 3 pphp level. The addition of the DTBPIB increased melt viscosity further and produced a homogeneous phase morphology of the blends. Impact energy improved with the DTBPIB level, while elongation at break and tensile strength showed an optimum at 0·6 pphp. Swelling behaviour and gel/sol from the boiled xylene extractions were studied, and the results obtained were correlated with the impact and tensile properties.