Effect of the structure of butadiene-nitrile elastomers on the ozone resistance of their vulcanizates

A comparative analysis of the ozone resistance of vulcanizates based on butadiene-nitrile elastomers with the same network density but different contents of acrylonitrile units is performed. The role of the orientation of chain fragments of vulcanizate chains during the reaction of double bonds with ozone is demonstrated.     

Structure of the interfacial layer and properties of crosslinked heterophase blends based on butadiene-nitrile and ethylene-propylene-diene elastomers

The density of the interfacial layer and the number of formed crosslinks have been estimated by means of swelling in selective solvents for heterophase blends of butadiene and ethylene-propylene elastomers. Ethylene-propylene-diene elastomers are characterized by an increased content of ethylene units and diene groups, a higher degree of isotacticity of propylene chain fragments, and a higher Mooney viscosity at low stereoregularity of the propylene units. The effects of the above parameters on the interfacial interaction and the kinetics of ozone degradation of the diene matrix have been studied.     

Rotational mobility of the radical probe in butadiene-nitrile rubbers

The difference in co-monomer composition of the disordered phase of butadiene-nitrile rubbers of BNKS and SKN grades is determined by EPR spectroscopy. The degree of aggregation of fragments consisting of alternating units and looseness of the disordered rubber phase in the case of BNKSs are shown to be higher than those of SKNs. The rotational mobility of the radical-probe indicates the lowering of the straight chain flexibility to be more pronounced in the case of BNKS rubbers. This phenomenon is due to the more large-size nanostructures if compared to the ones in SKNs.     

Modification of unsaturated rubbers in low-temperature plasma as a method to improve their adhesion properties

The change in the contact-surface properties of the films of unsaturated rubbers under the effect of a direct-current discharge has been investigated in case of the placement of the samples at the anode. It has been demonstrated that the modification in plasma leads to a substantial improvement in the contact properties of rubber films.     

Rheological properties of ethylene-propylene-diene elastomers

The processing of rubbers comprises a combination of complicated processes which realization almost always requires knowledge of their rheological behavior. The goal of the present work is to describe the rheological behavior of the EPDM vulcanizates via rotational rheometry. The effect of the cross-linking density and plasticizer content on the rheological behavior of the EPDM vulcanizates is described. The viscoelastic characteristics of the samples are defined from the frequency dependences of elasticity modulus G' and loss modulus G".     

Effect of an anionic emulsifier on the structure of butadiene-nitrile elastomers

X-ray diffraction and TMA studies show that surfactant sodium alkyl sulfonate (C₁₅) forms one of its two LC structures (distinguished by the smallest layer periodicity) in butadiene-nitrile elastomers containing different amounts of acrylonitrile units. In this case, the surfactant serves as a structural plasticizer and facilitates a more complete selective segregation of microblocks of trans-1,4-butadiene units and, especially, of sequences of alternating trans-1,4-butadiene and acrylonitrile units.     

Ozone resistance of crosslinked blends of butadiene-acrylonitrile and ethylene-propylene-diene elastomers and interphase interaction in these blends

The relation of ozone resistance to the volume and structure of the interphase layer and the amounts of crosslinks in the interlayer was studied for covulcanizates of butadiene-acrylonitrile rubbers of various polarities with ethylene-propylene-diene (EPDM) elastomers that differed in the comonomer composition and stereoregularity of propylene units. It was shown that the ozone resistance is determined by the compatibility of the components, the interlayer volume and density, the amount of crosslinks in the interlayer, and the strength of the EPDM network.     

Criticisms of standard ozone resistance testing of wax protected rubbers under static conditions

Evidence is presented to support the criticism of current standard test methods for static ozone exposure that the test temperature and conditioning procedure normally used can produced misleading results. It is suggested that, for rubber which rely on migration of wax to the surface for protection, more realistic results are obtained if conditioning and testing are carried out at 0°C.     

Modification of polypropylene with long-chain elastomers

Physicomechanical and rheological properties of isotactic polypropylene modified with a high-molecular-weight amorphous polymer, polyoctene, were studied. Modification of polypropylene with polyoctene allows the impact resilience and relative elongation to be increased relative to the initial polypropylene and the processing temperature to be decreased.     

Modification of fluorocopolymer coatings by telomers to improve their hydrophobicity

In this work, modification of coatings based on FP-5182 lacquer that is prepared from the copolymer of trifluorochloroethylene and vinylidenefluoride (F-32L) has been performed in order to improve their hydrophobicity. Several approaches to modification have been suggested, among which is the use of telomeric solutions of tetrafluoroethylene that were synthesized in various solvents, variation of the roughness of the coating surface by the aerosil powder, and a combination of these two approaches. The wetting properties of coatings have been studied, and improvement of the hydrophobic characteristics during their modification has been demonstrated.     

Mechanism and kinetics of the isothermal thermodegradation of ethylene-propylene-diene (EPDM) elastomers

The thermal degradation behavior of a range of ethylene-propylene-diene (EPDM) elastomers, covering the whole range of composition, has been examined under isothermal conditions between 410 and 440 °C using thermogravimetric analysis. The kinetic parameters of degradation for the polymers have been evaluated using different mathematical models based on different proposed mechanisms of degradation. The experimental data were fitted to the models using non-linear regression analysis technique based on Marquardt-Levenberg algorithm. It appears that the degradation of EPDMs follows the Avrami-Erofeev two-dimensional nucleation model or a random chain-scission mechanism. No observable trend was found between the ethylene content of EPDM and the activation energy of degradation.     

Radiochemical ageing of ethylene-propylene-diene elastomers. 4. Evaluation of some anti-oxidants

The preceding papers of this series were devoted to the identification and quantification of the main chemical changes resulting from the radiochemical ageing of EPDM (77.9% ethylene, 21.4% propylene, 0.7% diene) and EPR (76.6% ethylene, 23.4% propylene) films irradiated under oxygen atmosphere using ⁶⁰Co γ-rays. It was shown that two processes are involved in the EPDM radio-oxidation. The random γ-radiolysis of the polymer provides a constant source of macro-alkyl radicals that are likely to initiate a selective oxidation of the polymer through free-radicals reactions involving the abstraction of labile hydrogen atoms. In the present paper, infrared spectroscopy has been used to study the γ-degradation of EPDM cross-linked with dicumyl peroxide and/or stabilised with two types of anti-oxidants (hindered phenol or amine-type). The results show that the anti-oxidants are not efficient in preventing oxidation. To understand the lack of efficiency of the stabilisers, the impacts of the various formulations on the rate of degradation of EPDM against chain oxidation involved in thermal and UV ageing were also studied.     

Effect of temperature on the ozone cracking of butyl rubbers

The rates of growth of single ozone cracks have been measured for vulcanizates of two butyl rubbers over the temperature range of 20–160°C. Over most of this range the rates are quantitatively related to the segmental mobility of the polymer and depend upon temperature in accord with the appropriate from of the WLF relation. The rates are also proportional to the concentration of ozone. It is therefore concluded that diffusion of ozone into the polymer before reaction is the rate-controlling step. This is contrasted with the behavior of butadiene–styrene copolymers, for which the rates of crack growth are also quantitatively related to the segmental mobility, but the rates are somewhat larger at equivalent mobilities and the dependence upon ozone concentration is smaller. The difference is attributed to different penetration distances before reaction in polymers containing low and high densities of reactive sites.     

Modification of epoxy resins with liquid polysulfide and carboxylated butadiene rubbers

In this work, we present the results of studying the effect of liquid carboxylated butadiene and polysulfide rubbers on the physicomechanical and adhesive properties of epoxy adhesive compositions with curing agents of different chemical nature—diethylene triamine and polyoxypropylene triamine. It is found that carboxylated butadiene rubbers are more effective modifiers than polysulfide rubbers because they yield a higher complex of properties. It is also shown that the change in the chemical nature of a curing agent has no significant effect on the properties of epoxy-rubber adhesive compositions, which allows one to control their key technological parameters without fear of losing strength characteristics.     

Kinetics and mechanism of the ozone degradation of nitrile rubbers in solution

The kinetics of the decrease in the molecular mass of three nitrile rubber samples, containing, respectively, 20, 28 and 39 mol% of acrylonitrile, has been studied viscosimetrically during their ozonisation in solution. By comparing the functional groups obtained during ozonolysis of the CC bonds with the amount of the ozone consumed, it has been found that approximately 1 mole of ozonides or 2 moles of aldehydes are formed from 1 mole of reacted ozone. It has been shown that the proportion of aldehyde groups relative to the ozone consumed, which can be used as a measure of the degradation intensity, is in the 50–70% range. An attempt has been made to prove our suggestion that the intensity of the ozone degradation in solution of polybutadiene elastomers with predominantly 1,4-trans bonded butadiene, is considerably higher than that of the 1,4-cis-polybutadiene rubbers.     

Control of the plasticity of organosilicon rubbers by their modification with polypyrrole

Modification of organosilicon rubbers SKTN and SKTV with polypyrrole was studied. The modifying agent was synthesized directly in the rubbers containing iron trichloride acting as oxidant and catalyst, using the diffusion procedure and impregnation of organosilicon rubbers with pyrrole-2-carboxylic acid in supercritical carbon dioxide. Changes in the ductility and viscosity of the composite materials were analyzed.     

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.     

Use of maleic anhydride compatibilization to improve toughness and other properties of polylactide blended with thermoplastic elastomers

Polylactide (PLA) being a very brittle biopolymer could be toughened by blending with thermoplastic elastomers such as thermoplastic polyurethane elastomer (TPU) and thermoplastic polyester elastomer (TPE); unfortunately, these blends are immiscible forming round domains in the PLA matrix. Therefore, the purpose of this study was to investigate the effects of using maleic anhydride (MA) compatibilization on the toughness and other properties of PLA blended with TPU and TPE. MA grafting on the PLA backbone (PLA‐g‐MA) was prepared separately by reactive extrusion and added during melt blending of PLA/thermoplastic elastomers. IR spectroscopy revealed that MA graft might interact with the functional groups present in the hard segments of TPU and TPE domains via primary chemical reactions, so that higher level of compatibilization could be obtained. SEM studies indicated that PLA‐g‐MA compatibilization also decreased the size of elastomeric domains leading to higher level of surface area for more interfacial interactions. Toughness tests revealed that Charpy impact toughness and fracture toughness (K_IC and G_IC) of inherently brittle PLA increased enormously when the blends were compatibilized with PLA‐g‐MA. For instance, G_IC fracture toughness of PLA increased as much as 166%. It was also observed that PLA‐g‐MA compatibilization resulted in no detrimental effects on the other mechanical and thermal properties of PLA blends. Copyright © 2014 John Wiley & Sons, Ltd.     

Radiolysis of a mixture of butadiene-nitrile rubber with polyvinyl chloride

The effect of γ-radiation (⁶⁰Co) on a mixture of butadiene-nitrile rubber with polyvinyl chloride was studied. The molecular weights of crosslinked irradiated SKN-40-PVC-30 rubber were determined with the use of a viscometer. The radiation-chemical yields of crosslinkage and formation of effective crosslinks in SKN-40-PVC-30 (per 100 eV of absorbed energy) were determined by sol-gel analysis. Changes in the molecular structure of irradiated SKN-40-PVC-30 rubber (800 kGy) were studied by IR spectroscopy.