Weight Polybutadiene Research Articles

The component miscibility evolution during polymerization of the polybutadiene containing styrene solutions

In situ graft copolymerization of polystyrene (PS) on polybutadiene (PB) during polymerization of PB solution in styrene monomer was investigated to determine the performance of grafting process, chain structure of generated copolymers, and their effectiveness as compatibilizing agents for incompatible PS-rich and PB-rich phases. The amount of copolymers and their chain structures at different stages of polymerization were determined by gel permeation chromatography (GPC) curves of the reactive blends (taken directly from the reaction) and physical blends (physically prepared based on total composition of reactive blends). It was demonstrated that copolymer formation started from the early stage of polymerization and continued up to the phase inversion stage. In addition, PS grafting on PB occurred initially via single-chain attachment and then converted to a double-chain scenario later on. Compatibilizing efficiency of the copolymers was evaluated by Huggins coefficient (k H) obtained by performing dilute solution viscometry (DSV) on samples taken at different stages of conversions. The effect of molecular weight of PB on the grafting process and the effectiveness of copolymers generated were also studied. It was found that while compatibilizing role of the copolymers produced from high molecular weight PB (HPB) increases as conversion goes further, the compatibilizing efficiency of the copolymers produced from low molecular weight PB (LPB) shows a very sharp variation in a small range of conversion. Plotting k H of physical blends against weight fraction of PB molecules in solid content of the solutions (w PB) showed negative deviation from mixture law with a W-like pattern containing two minima with a maximum in between. While a negative deviation was assumed as indication of immiscibility of the components, upward deviation at middle values of w PB was attributed to molecular segregations that reduce the interface between the incompatible PS-rich and PB-rich phases.

Some properties of composites based on vulcanized liquid polybutadiene matrix and inorganic particulate fillers

AbstractThis study is primarily focused on the possibility to use a sulfur vulcanized low‐molecular weight polybutadiene with isocyanate end groups in the main chain as a matrix for composite materials reinforced with common inorganic particulate fillers (calcium carbonate, titanium dioxide, titanium dioxide modified with zinc, respectively). The isocyanate groups were used for a preliminary crosslinking of the oligomeric polybutadiene with glycerol as a three‐functional crosslinker. The prepared polybutadiene‐based polyurethane gel was subsequently vulcanized with sulfur. It has been shown that the vulcanized liquid polybutadiene could be successfully applied as the matrix for composite materials with inorganic filler. The resulting composite materials exhibited enhanced mechanical properties (tensile strength, flexural strength, hardness) and retain a high chemical resistance against hydrolysis and aqueous solutions of chemicals. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Shear induced finite orientational order in urethane/urea elastomers

New experimental results on urethane/urea free standing thin films (60 μm) prepared from a polypropylene oxide isocyanate terminated triol prepolymer (PU) and polybutadiene diol (PBDO) in the amount of 60% (PU/60PBDO) by weight of polybutadiene, which exhibit periodic patterns upon the application of a mechanical field are used to critically analyse these systems. We focus in this work on the analysis of the casting conditions and on the solid film characterization before and after UV irradiation. The casting of the different solutions was observed by polarizing optical microscopy (POM) coupled to a shearing system. The stress–strain and swelling data collected for the film before UV irradiation allowed the detection of an orientational order induced by the solution casting conditions, involving shear and evaporation of the solvent, which manifests itself in the anisotropy of the stress–strain and swelling film's properties in toluene. After UV irradiation of the elastomeric film, the interlinking of PBDO chains and amines linkages enhances the orientational order enabling instabilities to appear and the mesophase to become evident in the system as shown by POM, stress–strain and small angle light scattering data. Segregated soft and hard parts of the copolymer are thought to constitute the material unit, which is anisotropically distributed. The results here presented reinforce the earlier made claim that these systems do have an anisotropic structure akin to liquid crystallinity.

Shear-Induced Order Effects in Bi-Soft Segment Urethane/Urea Elastomers

In this work we study shear-induced order effects, observed on thin films (∼20–60 μm) of urethane/urea elastomers prepared from a polypropylene oxide based isocyanate terminated triol prepolymer (PU) and polybutadiene diol (PBDO) in the amount of 25% (PU/25PBDO), 50% (PU/50PBDO), 60% (PU/60PBDO) and 75% (PU/75PBDO) by weight of polybutadiene. Optical microscopy and light scattering as a function of temperature were used in this study. The initial isotropic elastomers, PU/60PBDO and PU/75PBDO, after cessation of a uniaxial mechanical deformation relax to a band texture, consisting of equidistant bright and black lines perpendicular to the shear direction. If the uniaxial mechanical stress is applied again perpendicular to the band structure in PU/60PBDO, a new periodicity with wave vector perpendicular to the axis of the field develops, while for PU/75PBDO two new periodicities can be observed, one with wave vector perpendicular to the axis of the field and the other transverse. The process of band formation is completely reversible in cycles of increasing and decreasing strain ratios. In samples PU/25PBDO and PU/50PBDO this kind of effect is not observed. The bands periodicity is temperature independent. The temperature dependence of the scattered intensity produced by the bands is different for bands perpendicular and transverse to the axis of the stress field. We show evidence that the urethane linkage is responsible for the relaxation instabilities observed, in this kind of material.

Block Polymers Derived from Poly(ethylene Oxide) and Hydroxy-Terminated Polybutadiene

Abstract Block polymers of AB, BAB, and ABA type, derived from preformed poly(ethylene oxide) (PEO) of different molecular weight and hydroxy-terminated polybutadiene (HTPB) were prepared. Poly(ethylene oxide-b-butadiene) and poly(butadiene-b-ethylene oxide-b-butadiene) were prepared by reaction of PEO, which was previously endcapped with TDI, with HTPB at a 1:1 or 1:2 reactants molar ratio. Poly(ethylene-oxide-b-butadiene-b-ethylene oxide) were prepared by reaction of isocyanate-endcapped HTPB with PEO at a molar ratio of reactants of 2:1. High reaction yields were obtained. Correlation between tensile properties and water absorption with block polymer composition was found.

Extensional stresses during polymer flow in ducts

During the flow of high molecular weight, narrow-, and broad-distribution polybutadienes and polyisoprenes rheo-optical measurements were conducted of extensional stresses acting along the flow axis in the preentrance and entrance regions of the duct and of their subsequent relaxation in the duct. The extensional stresses increase in the preentrance region, reach their maximum values at a distance of two or three tenths of the duct width from its edges, and then relax. The position of the maximum extensional stress is independent of polymer characteristics, shear stresses in the duct, and shape of the entrance and dimensions of the rectangular duct. The dependence of the maximum extensional stress on the shear stress of the duct wall can be assumed to be linear for small values. The length of the stress relaxation zone depends on the shear stress at the duct wall and the molecular mass distribution. It is independent of the molecular masses in narrow-distribution polymers. For the polymers investigated, a generalized dependence was obtained for the reduced duct length over which the extensional stresses relax to zero from the reduced deformation rate. This dependence takes into account the characteristic polymer relaxation times and the value of the molecular mass of the chain between the fluctuation entanglement. A considerable decrease in the duct's length-to-width ratio leads to an increase in the maximum values of the extensional stresses. A decreases in the duct entrance angle causes a reduction in the rate of increase of extensional stresses, the maximum values, and the acceleration of the relaxation processes in the duct. A decrease in the ratio of the width of the preentrance region to the duct width leads to a reduction in the maximum in extensional stresses. It is shown that one of the causes for the instability of the polymer flow in the ducts can be the rupture of polymers due to their extension in the preentrance and entrance regions. Calculations were done that describe satisfactorily the relationship between the values of the maximum extensional stresses and the shear rate and stresses on the duct wall.

Time, Temperature and Concentration Dependence of Ultimate Property in Fluid Fracture

Fluid fracture processes were considered from time, temperature and concentration dependence of the ultimate property during the course of an investigation of fracture processes of polymeric liquids, rubberlike and hard plastic polymers. The samples were liquid polybutadiene (PBD)-benzen solutions with six different volume fractions of PBD (v2) ranging from 0.374 to 0.782. The method and an apparatus used for the experiment are described in a previous report.1) The drop weight W and the breaking time tb were measured with various drop sizes at four different temperatures from 25°C to 40°C for each sample. The results may be summarized as follows:(1) Time and temperature dependence; (i) Weight vs. time curves at different temperature for each sample can be superposed into an almost unified master curve by the horizontal shift along the time axis. (ii) The shift distance logaT seem to follow the prediction of the Arrhenius equation. (iii) The apparent activation energy for the viscoelastic process from a plot of logaT against l/T systematically increases with decreasing v2.(2) Time and concentration dependence; (i) Time-concentration superposition is possible on a plot of W vs. logtb at each temperature, but it is impossible on a plot of W(ρs/ρ) vs. log tb, where ρ is weight of PBD per unit volume of the solution, ρs is a ρ selected arbitrarily as reference. (ii) The shift distance logac was examined from the following two equations; -1/logac=f(vs)+[f(vs)]2/γ(v1-vs)…(1), logac=log(η/ηs)={b(v2-vs)+c(v22-vs2)}/RT…(2), where v1=1-v2, vs is a reference volume concentration, b, c are constants. The Eq. (1) has been presented by Fujita and Kishimoto3), and corresponds to WLF equation. The Eq. (2) was lead from Andrade's viscosity equation η=A exp (U/RT), where U is replaced by interaction energy between polymer chain elements and solvent molecules in the from U=a+bv2+cv22 which was obtained form thermo-dynamical consideration of polymer solution. The present temperature-concentration region may be divided into three parts where logac obtained from experiment follow approximately the Eq>. (1) only, the Eq. (2) only, and both the Eqs.

Investigations of Molecular Weight “Jump” Reactions in Polybutadienes

Abstract Stereospecific, solution polymerization of butadiene to cis-1, 4 polybutadiene, using a catalyst system consisting of a cobalt compound and an organoaluminum compound, is a homogeneous reaction. In such a reaction, a diminution in catalyst activity accompanies the chain growth and chain transfer processes. Towards the end of the polymerization, the number of active catalyst centers is very small. The average molecular weight of polybutadiene can be raised in a definitive and reproducible manner, after completion of polymerization, by adding cocatalysts, e.g., alkyl or acyl halides, or certain active hydrogen compounds. Among other things, experiments in which (14C)-tert-butyl chloride was the cocatalyst have substantiated a cationic mechanism for this reaction. Changes in molecular structure are discussed on the basis of molecular weight fractionations with a Baker—Williams column and of results of viscometric and light scattering measurements.

Copolymerization of dienic hydrocarbons with alkyl vinyl ethers Communication 2. Low-temperature emulsion copolymerization of butadiene with alkyl vinyl ethers

1. In the emulsion copolymerization of butadiene with alkyl vinyl ethers in an alkaline medium the specific action of carbon tetrachloride is suppressed and the process proceeds almost entirely by the free-radical mechanism. 2. Introduction of ether units greatly reduces the molecular weight of polybutadiene (from 108,000 to 3,000). 3. The introduction of up to 20% of ether units in the polybutadiene chain has little effect on its stability to frost (TV = − 84°). When there is a predominance of ether units (70%), the stability to frost is greatly reduced (TV = − 30°), though the chemical stability is increased.