Rubbers with low flammability

Ways to decrease the flammability of rubber materials based on organosilicon rubbers of different structures and on ethylene–propylene–diene rubbers are shown. Data on the influence of the structure of organosilicon rubbers on their flammability and the influence of metal hydroxides and their dispersion on the decrease in the flammability of rubbers are given.     

Addition-curable type liquid silicone rubbers based on phenyl-containing organopolysiloxanes with terminal vinyl groups

Russian Chemical Bulletin - A series of organosilicon rubbers of the addition-curable type containing dimethyland methylphenylsiloxy, or diphenylsiloxy units with terminal vinyl groups were...     

Derivatives of carbamide, symmetrical triazines, and heptazines: Ecologically clean fire retardants for different thermostable compositions

The problems of replacing conventional halogen-containing fire retardants with alternative products, such as carbamide and symmetrical triazines and heptazines obtained on its basis, as well as different phosphates and ammonium polyphosphates, are considered. The main properties of the suggested compounds are described. It is shown that the range of compounds can be used, not only as fire retardants, but also as curing or modifying agents for polymer compositions, thermostabilizers of resins (based on ethylene-propylene rubbers) and sealants, and components of thermostable organosilicon compositions.     

Research and synthesis of organosilicon nonthrombogenic materials containing sulfobetaine group

A novel organosilicon sulfobetaine was synthesized through the reaction of organosilicon containing tertiary amino with 1,3-propanesulfone. Then this organosilicon sulfobetaine was coated onto polyurethane and organosilicon surface to improve their blood compatibility. The existence of sulfobetaine structure on the surface of materials was revealed by ATR-FTIR and XPS. The thermo-capability of synthesized silicone rubber, containing sulfobetaine was revealed by TGA. The blood compatibilities of organosilicon sulfobetaine and other materials such as silicone and PU as reference coated with them were evaluated by platelet-rich plasma adhesion experiment. The novel segmented silicone rubber containing sulfobetaine structure showed perfect blood compatibility.     

Chemiluminescence spectral analysis of styrene-butadiene and acrylonitrile-butadiene rubbers using a multichannel Fourier-transform chemiluminescence spectrometer

The chemiluminescence spectra of styrene-butadiene and acrylonitrile-butadiene rubbers isothermally heated in the range between room temperature and 200 °C were measured with a multichannel Fourier-transform chemiluminescence spectrometer. The observed spectra were analyzed by a least-squares fit using a Gaussian function to determine the peak intensity and the peak wavelength of emission bands. It was found that the peak wavelength of acrylonitrile-butadiene rubbers was slightly longer than that of styrene-butadiene rubbers due to the influence of the nitrile groups. The peak intensity of chemiluminescence from styrene-butadiene rubbers decreased with the styrene content, while that from hydrogenated acrylonitrile-butadiene rubbers increased with the iodine value. From these experimental results, it is concluded that the content of double bonds in the butadiene units in rubbers is measurable by chemiluminescence spectral analysis.     

3-dinitrobenzoylhydrazones of organosilicon carbonyl compounds

Conclusions The reaction of 3,5-dinitrobenzoylhydrazide with organosilicon aldehydes and ketones was investigated. It was shown that this reagent forms readily crystallizing 3,5-dinitrobenzoylhydrazones and is suitable for the identification of organosilicon carbonyl compounds.     

Experimental branching results for diene polymers by use of gel-permeation chromatography

Branching analyses in styrene–butadiene rubbers and polybutadiene rubbers have revealed large differences in branching between rubbers polymerized in different ways. The functionalities of several star-branched solution-polymerized styrene–butadiene rubbers were calculated and compared to their expected structures. Emulsion-polymerized polybutadiene rubber and a series of solution-polymerized polybutadienes made with different catalysts had different degrees of random branching, and evidence is presented indicating that the different available catalyst systems provide some latitude in making rubbers of different branching contents. Random branching analyses on a series of emulsion-polymerized styrene–butadiene rubbers revealed the dependency of branching on molecular weight and molecular weight distribution. The influence of polymerization temperature on the branching of emulsion-polymerized styrene–butadiene rubber was also studied.     

具有生物活性的有机硅化合物研究近况

生物有机硅化合物的研究进展迅速,而且越来越受到人们的重视。实际上,它是有机硅化学的一个新的分支。本文对有机硅化合物的毒理学、有机硅药物化学以及有机硅农药作了简要的论述。     

Synergistic effect between POSS and fumed silica on thermal stabilities and mechanical properties of room temperature vulcanized (RTV) silicone rubbers

In this paper, both divinyl-hexa[(trimethoxysilyl)ethyl]-POSS (DVPS) and fumed silica were firstly introduced into polydimethylsiloxane (PDMS) system using as the cross-linker and the reinforcing filler respectively. And a series of novel RTV silicone rubbers synergistically enhanced by DVPS and fumed silica were prepared. The cross-linked networks in the novel RTV silicone rubbers have been studied by attenuated total reflection infrared spectroscopy, and the dispersions of POSS and fumed silica in these novel RTV silicone rubbers have been observed by means of scanning electron microscope (SEM). And thermal stabilities, thermo-oxidative stabilities and mechanical properties of these novel RTV silicone rubbers were studied by means of thermal gravimetric analysis and universal tensile testing machine, respectively. From the obtained results, it was found that synergistic effect between POSS-rich areas and fumed silica on thermal stability and mechanical property of RTV silicone rubber indeed existed. And the experimental results also exhibited that the thermal stabilities and mechanical properties of the novel RTV silicone rubbers were far better than those of the reference materials (DVPR and MTFR). The striking enhancements in thermal properties and improvements on mechanical properties of novel RTV silicone rubbers were likely attributed to the synergistic effect between POSS-rich domains and fumed silica. Meanwhile, it was found that the mechanical properties of RTV silicone rubbers prepared with a given amount of POSS cross-linker were enhanced with the increment of the loading amount of fumed silica.     

An investigation of radiation-induced structural changes in nitrile rubber

The mechanism of radiation-induced structural changes in nitrile rubber with different acrylonitrile contents were investigated by ESR, NMR, and FTIR. To investigate new structures solid-state NMR methods had to be used due to crosslinking of the irradiated rubbers, and higher probe temperatures were used to obtain better resolution. The radicals generated on the acrylonitrile groups were found to abstract hydrogen from the adjacent butadiene units resulting in the formation of allylic radicals. These allylic radicals reacted to form intermolecular crosslinks and cyclisation. Cyclisation of the butadiene units were found to occur in the initial stages of the irradiation. Radiation yields of radicals increased with acrylonitrile content from 1.42, 1.58, to 2.42 for 18, 30, and 45% acrylonitrile rubbers. The radiation yields for intermolecular crosslinking were higher in rubbers with higher acrylonitrile contents, giving G values of 17.8, 21.3, and 24.5 for 18, 30, and 45% acrylonitrile rubbers, respectively. However, the crosslink clustering was found to be less in the rubbers with a higher acrylonitrile content. © 1996 John Wiley & Sons, Inc.     

Heterophase polymerization of styrene in the presence of organosilicon compounds of various natures

The heterophase polymerization of styrene has been carried out in the presence of surfactants—organosilicon compounds with different solubilities in aqueous and styrene phases and surface activities at the interface. It has been demonstrated that the stability of polymer suspensions prepared with water-insoluble organosilicon compounds is much higher than that in the presence of organosilicon surfactants soluble in organic and aqueous phases. In the former case, suspensions with narrower particle-size distributions are produced. The stability of polymer microspheres prepared at various monomer-to-water volume ratios has been tested. An increase in the monomer concentration above 25 vol % leads to the loss of system stability.     

有机硅-丙烯酸酯聚合物乳液合成及粒径分析

通过种子乳液半连续法合成了有机硅改性丙烯酸酯聚合物乳液,并对其粒子形态及分布进行分析。结果表明:通过种子乳液半连续聚合工艺可制备出固含量42wt%,乳化剂含量4wt%(基于单体量)、窄分布纳米粒子的有机硅改性丙烯酸酯聚合物乳液。随反应进行,粒径分布变窄,平均粒径逐渐增大。随乳化剂中SDS与OP-10的摩尔比减少,粒径增大。     

Diene Rubber Modification Using Thiol-Type Derivatives

Thiol-containing antioxidants such as 4-(mercaptoacetamido)-diphenylamine (MADA) undergo ready addition of-SH groups to the double bonds in diene rubbers in the presence of initiators. The reaction is a radical chain process leading to rubbers with improved thermooxidative resistance. The modification reaction has been carried out on high cis-polyisoprene and polybutadiene, and conditions under which the physicochemical properties (e.g., inherent viscosity, gel content, and microstructure) are less affected have been found. An oxygen absorption test and DSC were used as rapid methods for evaluation of thermooxidative stability of modified rubbers. The superiority of rubbers with MADA chemically attached (ranging from 1 to 4 phr) was shown by a circulating air oven test and by an extraction process which simulates the aggressive environments experienced by many rubbers under practical conditions. The results obtained show that a small degree of modification (1 phr MADA) is large enough to provide good thermooxidative stability without alteration of the molecular characteristics of the parent rubbers. At higher degrees, cistrans isomerization can occur.     

Surface characterization of polybutadiene and natural rubbers oxidized by silver(II)

Silver (II) ion is a powerful oxidizing mediator that was used for surface modification of vulcanized polybutadiene rubber (BR) and natural rubber (NR) through mediated electrochemical oxidation (MEO). Scanning electron microscopy (SEM) pictures showed that surface morphology of the oxidized rubbers was changed so that some cracks and holes appeared on the surface in macroscopic scale. This is possibly due to chain scission caused by alkane group formation which is in turn in accordance with the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra. The amounts of hydroxyl and carbonyl type surface functional groups were also increased in both oxidized rubbers. The results obtained by atomic force microscopy (AFM) showed that the surface roughness for both rubbers was changed significantly from nano- to micro-scale. Energy dispersive X-ray analysis (EDXA) expresses that surface concentration of atomic oxygen for both BR and NR was increased significantly. Also surface polarity of the treated rubbers was enhanced based on contact angle measurements leading to a higher hydrophilicity. Finally it was found that silver(II) has a somewhat greater oxidation impact on the surface of natural rubber than polybutadiene rubber.     

Effect of glycoluril and its derivatives on the flame resistance and physico-mechanical properties of rubber

The effect of bicyclic bisureas (glycolurils) and their derivatives functionalized with hydroxymethyl, halomethyl, and dimethoxyphoshorylmethyl groups on the flame resistance and physico-chemical properties of synthetic isoprene and divinyl rubbers was studied, and the procedures for preparing these agents were suggested. The rubbers with the addition of the synthesized bicyclic bisureas demonstrated satisfactory levels of flame resistance and physico-mechanical parameters.     

Liquid hydrocarbon rubbers and their fields of application

The classification of liquid rubbers with terminal functional groups depending on their composition and structure is presented. Polydieneurethanes, as well as liquid rubbers with terminal carboxylic groups, are of the greatest interest for industry. The particular variants of applications of modified liquid rubbers for producing sealants, adhesives, compounds, and protective coatings with unique properties are presented.     

Toughening of highly cross-linked polycyanurates with epoxy- and phenol-terminated butadiene-acrylonitrile rubbers

Polycyanurate from dicyanate of bisphenol A was modified with epoxy- and phenol-terminated butadiene-acrylonitrile rubbers. Rubber-resincopolymerisation was followed by multiple-detection gel-permeation chromatography (GPC). It was found that both the epoxy-terminated and phenol-terminated rubbers react with the cyanate and thus are covalently bound with the polycyanurate network. The influence of rubber content, acrylonitrile content and type of end group on phase structure was investigated using dynamic mechanical analysis. Fracture toughness was measured for these modifications.     

Synthesis of some triphenylmethyl- and triphenylethylsiloxanes

Summary For the first time 8 pure oxygen-captaining organosilicon compounds were prepared; some of them can be utilized for the preparation of high-molecular organosilicon polymers.     

Gasoline- and oil-proof rubbers based on cyclic α-oxides for heavy-duty rubber technical goods

The physicomechanical properties of oil- and gasoline-proof rubbers based on cyclic α-oxides (epichlorohydrin, propylene oxide) and hydrocarbon rubbers (butadiene-nitrile, chloroprene) are described. It is shown that epichlorohydrin rubbers (EKhGKs) have some advantages over butadiene-nitrile and chloroprene rubbers, particularly for operation in extreme conditions in oil drilling and gas equipment for environments with a high content of hydrogen sulfide. Examples of the application of low-molecular EKhGKs as adhesives and sealants are given.     

The synthesis of organosilicon diacetylene alcohols with conjugate tertiary bonds

Summary A method was developed for obtaining organosilicon diacetylene alcohols with conjugate tertiary bonds.