Butadiene Copolymer Research Articles

Telechelic oligomers obtained by metathetic degradation of both polyisoprene and styrene–butadiene rubbers. Applications for recycling waste tyre rubber

Metathetic degradation of synthetic cis-1,4-polyisoprene (PI) and styrene–butadiene copolymer (SBR) was performed with cis-1,4-diacetoxy-2-butene (DAB) as chain transfer agent (CTA) using Grubbs II catalyst. Well-defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a wide range of targeted average molecular weights from 350 g mol−1 to 98,000 g mol−1, with a polydispersity index of around 2. Starting from SBR, a similar structure control was obtained with a range of Mn from 1400 g mol−1 to 65,000 g mol−1. It was found that precise selection of catalyst concentration and solvent is the major factor to obtain targeted products with high Mn control. Moreover, preliminary tests using such a procedure have shown its efficiency starting from waste tyre. This methodology thus suggests the possibility to recycle such rubber waste leading to high value liquid rubber.

Characterization of pyrolysis products formed from styrene-1,2-unit heterosequence of styrene–butadiene copolymer

Styrene–butadiene rubbers (SBRs) were pyrolyzed and the pyrolysis products were analyzed using gas chromatography/mass spectrometry (GC/MS). 3-Phenylcyclopentene (3-PCP) and 4-phenylcyclohexene (4-PCH) were found to be characteristic pyrolysis products formed from the styrene-1,2-unit heterosequence. 4-PCH can be also generated from the styrene-1,4-unit heterosequence. Relative abundance of 4-PCH was larger than that of 3-PCP. Relative intensities of 3-PCP and 4-PCH decreased with increasing the pyrolysis temperature. By comparing the (3-PCP+4-PCH)/butadiene ratios of bound and unbound rubbers of an SBR compound, relative abundance of the styrene-1,2-unit heterosequence in the bound rubber was found to be smaller than that in the unbound one. Degree of the styrene-1,2-unit heterosequence of raw SBR or bound rubber can be estimated by analyzing the 3-PCP and 4-PCH using pyrolysis-GC/MS.

Synthesis and characterization of in-chain silyl-hydride functional SBR and self-crosslinking elastomer

Abstract Functional in-chain silyl-hydride (Si-H) SBR copolymers of 4-vinyiphenyldimethylsilanol (VPDMS) and butadiene were synthesized by living anionic polymerization, in which active group Si-H was not lost and its content was controllable. Corresponding self-crosslinking elastomers were obtained by hydrosilation of Si-H group with vinyl bonds in chain. The copolymers and elastomers were characterized by 1 H NMR, size exclusion chromatography (SEC), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA) techniques.

A new liquid rubber‐assisted dispersion of organoclay in carbon black filled carboxylated acrylonitrile–butadiene rubber matrix

AbstractA novel route for the preparation of rubber–carbon black–nanoclay (NC) nanocomposites with XNBR as a matrix and a carboxyl‐terminated copolymer of butadiene and acrylonitrile (CTBN) as a low‐molecular‐weight modifier for commercially available NC is presented in this article. The addition of NC to the rubber (after the NC was mixed with CTBN in a 2 : 1 ratio) showed remarkable improvement in the mechanical properties. The clay loading was varied from 0 to 10 parts per hundred rubber (phr). An amount of 20 phr N330 black was incorporated into all of the formulations. The properties were compared with those of a control XNBR compound having only 20 phr N330. X‐ray diffraction revealed a combination of a high level of intercalated and exfoliated structures in such nanocomposites. Transmission electron microscopy confirmed the improvement in dispersion as a result of addition of CTBN. A 127% increase in the tensile strength and a 53% increase in the elongation at break were achieved. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Enhancement in the Photoluminescence Properties of SiO2:Ge Embedded in a Polymeric Matrix

Polymer films of styrene butadiene copolymer (SBC) mixed with SiO2:Ge powder were successfully obtained by the drop casting method. The SBC concentration (in chloroform solution) was 10%w/v and the SiO2:Ge powder was mixed (mass ratio 80:20 respectively). The thicknesses of the films obtained were 50, 100, and 200 μm. In addition, polymer films of polytetrafluoroethylene (PTFE) preparation (60% dispersion in water), were obtained mixing 2 ml of PTFE and 0.05g of SiO2:Ge powder with a mass relation of 98% polymer and 2% SiO2:Ge. The photoluminescence emission spectra (PL) of SBC doped with SiO2:Ge resulted in similar characteristics to those for SiO2:Ge powders, although their intensity shows an increase 3.5 times approximately, compared with the pure powder. On the other hand, the PTFE films with SiO2:Ge present just one peak in the PL emission at 439 nm but their intensity increases 18 times respect to the powder. The photoluminescence excitation (PLE) spectra of the SiO2:Ge powders show the characteristic peaks at 248 nm (most intense) and at 366 nm. However, when the powder is embedded either in SBC or PTFE the peak at 366 nm shows an important increase which seems to indicate an energy transfer from the polymer to the SiO2:Ge.

Method of composition heterogeneity reduction in copolymer of butadiene with isoprene in ionic coordination polymerization with supported titanium catalysts

Compositional heterogeneity of copolymers of butadiene with isoprene in copolymerization with supported titanium catalyst was investigated. The causes of compositional heterogeneity were found based on solution of an inverse problem of formation of the molecular weight distribution. It was shown that the pre-hydrodynamic effects in a turbulent reactor at the stage of the reaction mixture formation allowed the synthesis of more uniform composition of the copolymer.

Electromagnetic interference shielding effectiveness of nanoreinforced polymer composites deposited with conductive metallic thin films

The effect of using conductive metallic thin films deposited on high density polyethylene (HDPE) and styrene butadiene copolymer (SBC) in conjunction with carbon nanofiber (CNF) reinforcement of HDPE and SBC was investigated in order to improve the electromagnetic interference shielding effectiveness (EMI SE) of the structures. Thin films of copper, silver and aluminum were deposited by thermal evaporation onto the polymeric matrices and its composites (0–20wt.% of CNFs). Results show a synergistic effect of the two approaches (metallic coating and CNF reinforcement) toward improving the EMI SE. The chemical composition, surface morphology, carbon nanofiber distribution, thickness and microstructure of metallic coated polymers are examined using X-Ray Diffraction and Scanning Electron Microscopy.

Mechanical and AFM investigations of elastomers filled with multiwall carbon nanotubes

Strong reinforcing effects are observed when multiwall carbon nanotubes are incorporated in a styrene–butadiene copolymer. The good level of dispersion of carbon nanotubes in the host matrix that allows to take advantage of their high aspect ratio as well as their orienting capability under uniaxial extension, appear to be the main parameters for mechanical reinforcement. Atomic force microscopy carried out in the unstretched and stretched states has been shown to bring important insights for the understanding of the mechanical properties of the composites.

Mechanical, thermal, and transport properties of nitrile rubber–nanocalcium carbonate composites

AbstractThe article describes the properties of acrylonitrile butadiene copolymer (NBR)–nanocalcium carbonate (NCC) nanocomposites prepared by a two‐step method. The amount of NCC was varied from 2 phr to 10 phr. Cure characteristics, mechanical properties, dynamic mechanical properties, thermal behavior, and transport properties of NBR–NCC composites were evaluated. For preparing NBR nanocomposites, a master batch of NBR and NCC was initially made using internal mixer. Neat NBR and the NBR–NCC masterbatch was compounded with other compounding ingredients on a two roll mill. NCC activated cure reaction upto 5 phr. The tensile strength increased with the nanofiller content, whereas NBR–NCC containing 7.5 phr exhibited the highest modulus. The storage modulus (E′) increased up to 5 phr NCC loading; the reinforcing effect of NCC was seen in the increase of modulus which was more significant at temperatures above Tg. The effect of nanofiller content and temperature on transport properties was evaluated. The solvent uptake decreased with NCC content. The mechanism of diffusion of solvent through the nanocomposites was found to be Fickian. Transport parameters like diffusion, sorption, and permeation constants were determined and found to decrease with nanofiller content, the minimum value being at 7.5 phr. Thermodynamic constants such as enthalpy and activation energy were also evaluated. The dependence of various properties on NCC was supported by morphological analysis using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis of random or tapered solution styrene–butadiene copolymers in the presence of sodium dodecylbenzene sulfonate as a polar modifier

AbstractRandom or tapered solution styrene–butadiene copolymer (SSBR) is very difficult to prepare in an isothermal batch process without the use of polar modifiers because of the diverse reactivity ratios of the styrene and the butadiene in hydrocarbon solvents. In the presence of polar modifiers, the random SSBR can be synthesized by anionic living polymerization with the variety of microstructures, which results in the change of glass transition temperature (Tg). This article will discuss the use of sodium dodecylbenzene sulfonate as a polar modifier in isothermal batch process that controls the microstructure of the SSBR resulting in a random as well as tapered SSBR with low Tg (−67°C to −80°C). The Tg of SSBR was controlled by the styrene content rather than the microstructure of polybutadiene. Physical properties of SSBR compounding were discussed for tire tread applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The clay mineral modifier as the key to steer the properties of rubber nanocomposites

An innovative organoclay containing polybutadiene chains was prepared in order to make rubber nanocomposites based on natural rubber or styrene–butadiene copolymer. It was obtained by reacting a maleinised polybutadiene oligomer with the CH2CH2OH moieties present in the ammonium cation of a commercially available organoclay (Cloisite 30B). Elastomeric nanocomposites were also prepared with a reference organoclay, formed by intercalation during mixing with dialkyl dimethylammonium chloride. Sulphur cured nanocomposites were characterised in terms of curing kinetics, morphology, tensile and dynamic-mechanical properties; chemical interactions between the modifier of the new organoclay and the matrices can be inferred by experimental evidences.

Biomimetic Monolayer and Bilayer Membranes Made From Amphiphilic Block Copolymer Micelles

The deposition of amphiphilic poly(ethylene oxide)-block-poly(butadiene) (PEO-b-PBD) copolymer micelles is demonstrated on solid substrates. Depending upon surface chemistry, micelle adsorption creates either monolayer or bilayer films. Lateral diffusion measurements reveal that strong coupling between hydrophilic surfaces and PEO blocks creates immobile bilayers, while monolayers retain the fluidity previously observed in vesicular assemblies.

MODELING AND OPTIMIZING PROPERTIES OF NANOCLAY–NITRILE RUBBER COMPOSITES USING BOX–BEHNKEN DESIGN

Abstract The mechanical behavior of acrylonitrile butadiene copolymer (NBR)–organomodified layered silicate (nanoclay) was modeled using design of experiments approach. A Box–Behnken design with three factors and three levels was used to model the relationship between properties of NBR nanocomposites and the ingredients. The factors considered in the design were silica content, nanoclay loading, and dicumyl peroxide content. The nanocomposites were evaluated for tensile strength, modulus, elongation at break, oxygen permeation rate, and effect of oil and heat aging on mechanical properties. Regression equations were generated to model the properties of interest and generate response surfaces and contour plots. The predicted properties of the nanocomposites were in good agreement with the experimental results. The contour plots were overlaid within the applied constraints to identify the combination of factor ranges that gives the optimal performance of the nanocomposites for application as control system bladders in satellite launch vehicles.

Styrene butadiene co-polymer based conducting polymer composite as an effective corrosion protective coating

Electroactive conducting polymer composite coatings of polyaniline (PANI) are electrosynthesized on styrene–butadiene rubber (SBR) coated stainless steel electrode by potentiostatic method using aqueous H2SO4 as supporting electrolyte. The protective behaviour of these coatings in different corrosion media (3.5% NaCl and 0.5M HCl) is investigated using Tafel polarization curves, open circuit potential measurements and electrochemical impedance spectroscopy. The results reveal that SBR/PANI composite coating is much better in corrosion protection than simple PANI coating. The corrosion potential of composite films shifts to more noble values indicating that SBR/PANI composite coating act as an effective corrosion protective layer.

High‐performance EMI shielding materials based on short carbon fiber‐filled ethylene vinyl acetate copolymer, acrylonitrile butadiene copolymer, and their blends

AbstractThe composites of carbon fiber with EVA, NBR, and their blends have been made by melt mixing technique. Stress–strain plots of different composites show that the necking phenomenon is increasing with the increase in fiber concentration in the polymer matrix. The scanning electron microscopic analysis and swelling study exhibit poor interaction between the short carbon fiber and polymer matrix. The decrease in DC resistivity with the increase in short carbon fiber concentration has been explained on the basis of percolation theory. EMI SE increases slightly with the increase in frequency of electromagnetic radiation but increases sharply with the increase in fiber concentration. EMI SE also depends on blend composition and increases with the increase in EVA concentration in the blend. Return loss is decreasing but absorption loss is increasing with the increase in fiber loading. A linear relationship is observed between the EMI SE and thickness of the composites. The EMI SE is found to increase exponentially with the increase in conductivity of the composite. The permeability value is decreasing with the increase in frequency as well as fiber loading. Thermal properties of the composites have been evaluated by thermogravimetric analysis and dynamic mechanical analysis. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Effect of the hydrodynamic action on the microstructure of butadiene-isoprene copolymers

270 In copolymerization of denies in the presence of Ziegler-Natta ioncoordination catalytic systems, each of the monomers affects the microstructure of units of the other monomer in the copolymer chain (1). For example, in copolymerization of butadiene with isoprene in the presence of catalytic systems based on titanium halides, an increase in the fraction of isoprene in the initial monomer mixture caused a

Comparison of the transient stress-strain response of rubber to its linear dynamic behavior

Master curves of the small strain and dynamic shear modulus are compared with the transient mechanical response of rubbers stretched at ambient temperature over a seven-decade range of strain rates (10−4 to 103 s−1). The experiments were carried out on 1,4- and 1,2-polybutadienes and a styrene–butadiene copolymer. These rubbers have respective glass transition temperatures, Tg, equal to −93.0, 0.5, and 4.1 °C, so that the room temperature measurements probed the rubbery plateau, the glass transition zone, and the onset of the glassy state. For the 1,4-polybutadiene, in accord with previous results, strain and strain rate effects were decoupled (additive). For the other two materials, encroachment of the segmental dynamics precluded separation of the effects of strain and rate. These results show that for rubbery polymers near Tg the use of linear dynamic data to predict stresses, strain energies, and other mechanical properties at higher strain rates entails large error. For example, the strain rate associated with an upturn in the modulus due to onset of the glass transition was three orders of magnitude higher for large tensile strains than for linear oscillatory shear strains. © 2011 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys, 2011

Glass transitions and ionic conductivity in a poly(butadiene-acrylonitrile)–LiAsF 6 system

The intention of this work was to investigate the concentration dependence of glass transitions and ionic conductivity in a solvent-free polymer electrolyte system based on an amorphous polymer matrix. The study was carried out on an elastomeric random copolymer of butadiene and acrylonitrile (PBAN) containing LiAsF 6 in the range from pure PBAN to 3.35 mol kg −1 (or a CN/Li ratio of 2.25:1), which covered both the homogenous (up to CN/Li = 4:1) and two-phase regions of the system. The results demonstrated that both T g and ionic conductivity slightly increased with salt content up to a CN/Li ratio of 10:1, and typical behaviour for amorphous solid polymer electrolytes was observed within this concentration range. For higher salt contents, CN/Li ratios from 8:1 to 6:1, the increases in T g was much larger than expected, and rapid decrease in conductivity were also observed. Near the limit of the homogeneity region of the PBAN–LiAsF 6 system (CN/Li = 5.75:1 to 4:1), broad dispersion of the experimental T g and conductivity values were observed. In individual cases, abrupt decreases in T g were observed simultaneously with dramatic increase in electrolyte conductivity (up to 10 −4 S cm −1). For highly concentrated samples (CN/Li = 5.75:1 to 4:1), as well as for two-phase samples up to 3.25:1, glass transitions and conductivity were established to be strongly dependent on the sample pre-history, which is typical for the metastable state of a system. The complicated behaviour of glass transitions and ionic conductivity of the PBAN–LiAsF 6 electrolytes must be attributed to the specific transformations of their ionic and molecular structures. Structural changes are related to diffuse phase transitions that have been proposed at moderate (2nd order) and limiting (1st order) salt concentrations.

Impact of Filler Surface Modification on Large Scale Mechanics of Styrene Butadiene/Silica Rubber Composites

In material science of elastomers the influence of nanoscale and nanostructured filler particles is of utmost significance for the performance of innovative rubber products, i.e., passenger car tires with ultralow rolling resistance but high wet-grip performance. A better understanding of the physical characteristics of the filler–rubber interface and the filler–rubber interphase as well is necessary to improve the overall macroscopic properties of these elastomeric nanocomposites. Therefore, the surface energies and polarities of filler particles with different modified surfaces were measured by a modified Wilhelmy technique. In all cases the rubber matrix consisted of a solution - styrene butadiene copolymers, filled with 20 or 40 phr pyrogenic or precipitated silica grades with different surface modifications by silanes, and a carbon black sample as reference. A moving die rheometer was employed to observe the filler flocculation at elevated temperatures (160 °C) in rubber mixtures containing no curati...

Optimizing properties of nanoclay–nitrile rubber (NBR) composites using Face Centred Central Composite Design

The properties of acrylonitrile butadiene copolymer (NBR)–nanoclay composites were modelled using response surface methodology (RSM). A Face Centred Central Composite Design (FCCD) with four factors and three levels was used to obtain the relationship between nanocomposite properties and levels of ingredients. The factors considered in the design were silica content, nanoclay content, vulcanization system and dicumyl peroxide content. The nanocomposites were evaluated for tensile strength, modulus, elongation at break, oxygen permeation rate and effect of oil ageing on mechanical properties. Regression equations were generated to model the properties of interest and generate response surfaces and contour plots. The predicted properties of the nanocomposites were in good agreement with the experimental results. The contour plots were overlaid within the applied constraints to identify the combination of factor ranges that gives the optimal performance of the nanocomposites for application in control system bladders for launch vehicle applications.