The thermo–oxidative degradation of acrylonitrile–butadiene–styrene copolymers during processing as studied by chemiluminescence

The glow curve obtained upon processing acrylonitrile–butadiene–styrene copolymers (ABS), through various machines, reaches a peak at 180°C. The proper assignment of that peak has required the study of the chemiluminescence (CL) shown by related polymers such as: polybutadiene (PB), styrene–acrylonitrile copolymer (SAN), and polyacrylonitrile (PAN). Three hydroperoxide types associated with the structural units, that is, 1, 2, and cis- and trans-1,4, exhibiting CL peaks at 180, 240, and 340°C, respectively, have been identified in the PB sample. The activation energy (E_a), recorded for the hydroperoxides thermal decomposition, was 15.0 ± 1.0, 17.85 ± 0.9, 20.7 ± 0.8 kcal/mol. PAN shows a CL peak at 180°C. Its occurance is related to the color developed during the thermal treatment. That PAN peak has been attributed to the hydroperoxides generated on the acrylonitrile units neighboring the azomethinic structures. The corresponding E_a is 23.3 ± 1.0 kcal/mol. The same peak (having an identical position and E_a) has been identified with processed ABS and SAN copolymers. As is evident by CL studies, the processing induced oxidation mainly occurs within the SAN phase of the ABS copolymers, though it was also noted within 1,2 units of the PB phase.     

Chemiluminescence from amine cured epoxy resins modified with halogenated phenylglycidyl ethers

Chemiluminescence from thermooxidized epoxide alone and that modified with phenyl glycidyl ethers has been investigated in isothermal and nonisothermal regime. Isothermal curves are characterized by a monotonous fall of chemiluminescence intensity from some initial value to very low levels of light emission. Nonisothermal curves show a maximum intensity at temperatures above 473 K. The luminescence intensity is influenced by both T_g and thermal stability of epoxide. The higher T_g or higher thermal stability brings about the higher intensity of light emission and vice versa. © 1994 John Wiley & Sons, Inc.     

Determination of the oxidative stability of vegetable oils by rancimat and conductivity and chemiluminescence measurements

The oxidative stability of five different oils was determined by Rancimat analysis with conductivity and chemiluminescence measurements for evaluation of the induction periods. Samples of oil, taken at intervals from the Rancimat apparatus, were used for chemiluminescence measurements. The chemiluminescence results were plotted vs. time, and the resulting curves were evaluated with a graphical tangential procedure in the same way as the curves of the Rancimat method (conductivity measurement). Induction periods of the oils assessed by Rancimat and chemiluminescence methods showed a significant linear correlation (r=0.9865). The temperature dependence of the induction periods evaluated by chemiluminescence and by conductivity was investigated with walnut oil. A marked temperature dependence was observed for both.     

Synthesis and characterization of graft copolymers of syndiotactic polystyrene with polybutadiene and 4‐methylstyrene

The basic method for synthesizing syndiotactic polystyrene‐g‐polybutadiene graft copolymers was investigated. First, the syndiotactic polystyrene copolymer, poly(styrene‐co‐4‐methylstyrene), was prepared by the copolymerization of styrene and 4‐methylstyrene monomer with a trichloro(pentamethyl cyclopentadienyl) titanium(IV)/modified methylaluminoxane system as a metallocene catalyst at 50°C. Then, the polymerization proceeded in an argon atmosphere at the ambient pressure, and after purification by extraction, the copolymer structure was confirmed with ¹H‐NMR. Lastly, the copolymer was grafted with polybutadiene (a ready‐made commercialized unsaturated elastomer) by anionic grafting reactions with a metallation reagent. In this step, poly(styrene‐co‐4‐methylstyrene) was deprotonated at the methyl group of 4‐methylstyrene by butyl lithium and further reacted with polybutadiene to graft polybutadiene onto the deprotonated methyl of the poly(styrene‐co‐4‐methylstyrene) backbone. After purification of the graft copolymer by Soxhlet extraction, the grafting reaction copolymer structure was confirmed with ¹H‐NMR. These graft copolymers showed high melting temperatures (240–250°C) and were different from normal anionic styrene–butadiene copolymers because of the presence of crystalline syndiotactic polystyrene segments. Usually, highly syndiotactic polystyrene has a glass‐transition temperature of 100°C and behaves like a glassy polymer (possessing brittle mechanical properties) at room temperature. Thus, the graft copolymer can be used as a compatibilizer in syndiotactic polystyrene blends to modify the mechanical properties to compensate for the glassy properties of pure syndiotactic polystyrene at room temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rheological properties of concentrated polymer solution: Polybutadiene in good and θ solvents

The zero shear viscosity, η° of three polybutadiene samples having different molecular weights over a wide range of concentration (1.0–35.0% polymer) in good and θ solvents has been studied. Superposition of viscosity data has been made to give a single composite curve for each solvent by shifting them vertically by a factor (M°/M)^3.4, where M° represents the molecular weight of the reference sample. The shift factor is found to be proportional to M^3.4 in the region of higher concentration, which indicates that the 3.4-power law is valid for the data of polybutadiene. The double-logarithmic plots of relative viscosity η°_r as a function of c⁵M^3.4 yielded a single composite curve approximating a straight line with slope of unity at the higher values of the variables. The results indicate that over a considerable range of the variables (molecular weight and concentration) at a constant temperature, the relative viscosity is a single function of c⁵M^3.4. The results for double-logarithmic plots of zero shear specific viscosity η°_csp as a function of concentration confirmed those observed in polycholoroprene samples studied earlier that the η0_sp values in θ solvents at higher concentration region are found to be higher than those found in good solvents, whereas in the moderately concentrated region the values are just opposite in θ and good solvents. The viscosity crossover in θ solvents is not as sharp as is found in case of polychloroprene samples and that crossover, too, has taken place in the range of concentration of 11.7–31.6% polymer, which is comparatively higher than that of polychloroprene samples (6.06–21.0% polymer). The results indicate some relation between viscosity crossover and polymer polarity, supporting the idea of enhanced intermolecular association in poor solvents. To correlatethe viscosity data obtained in good and poor solvents, two methods, one given by Graessley and the other given by Dreval and coworkers involving the correlating variable c[η], were considered. The plots of relative viscosity η°, versus the correlating variable c[η] in benzene (good solvent) yielded one curve, but in the case of θ solvents (dioxane and isobutyl acetate), the same plots yielded three separate curves instead of a single curve, which is rather unusual. The appropriate correction on the correlating variable for chain contraction in the concentrated region in a good solvent moved the data to a common curve, especially in lower concentration region, but at the higher concentration region a slight overestimation of data seems to have been effected. On the other hand, the plots of log η as a function of correlating variable c[η] yielded a single curve for three samples in the good solvent benzene, but in poor solvents (diozane and isobutyl acetate) the same plots yielded three separate curves for three samples instead of a single curve, the reason for which is not known at present. However, the normalization of the correlating variable c[η] with Martin constant K_M reduced all experimental data of the polymer samples to a common curve. The correlation of the viscosity data by either of the two methods seems to be possible in the case of the nonpolar flexible polymer, polybutadiene.     

Studies on thermodynamic compatibility of nitrile rubber and polybutadiene by inverse gas chromatography

Inverse gas chromatography technique has been used to study the thermodynamic compatibility of the industrially important elastomers polybutadiene (BR) and polybutadiene copolymerised with acrylonitrile (NBR). The NBR used in this study had nitrile contents of 18 and 34%. The ratio of BR/NBR in blends varied between 1 and 0.25 in both cases and retention volume of twelve probes was measured at 80°C. The Flory-Huggins interaction parameter X′₂₃, computed using a standard procedure, and also the interaction parameter B₂₃ showed that BR and NBR are incompatible in all compositions and that incompatibility increases with nitrile content. © 1995 John Wiley & Sons, Inc.     

Swelling and static–dynamic mechanical behavior of mica-reinforced linear and star-branched polybutadiene composites

Physical properties of mica-reinforced linear (LPB) and star-branched polybutadiene (SPB) composites have been studied with special reference to the effect of silane coupling agent, degree of crosslinking, and degree of mica loading, as well as the molecular architecture of polybutadienes. Tensile properties increase and swelling decreases with addition of mica for linear polybutadiene. Star-branched polybutadiene shows a reverse behavior, especially beyond 5% of mica. The improvements in mechanical properties are more pronounced in the case of silane-treated mica compositions of both type of polybutadienes. Dynamic mechanical spectra were obtained for linear and star-branched polybutadienes. Effects of mica loading and silane treatment on dynamic moduli are discussed. Dynamic mechanical moduli (E′, E′) of composites increase with increasing mica content for linear polybutadiene but decrease for star-branched polybutadiene beyond certain mica loadings. Effective damping regions were determined in terms of frequency and temperature. The glass transition temperature (T_g) increased slightly, and the damping peak (tan δ) broadened due to the rubber—filler interaction, especially after silane treatment for both polymers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1943–1952, 1997     

High performance elastomer composites containing ultra high cis polybutadiene with high abrasion and low rolling resistances

A series of rubber composites with ultra high cis polybutadiene (UBR), NUC1–3, SBC1–4, SUS1–4, was prepared, and their vulcanized properties were measured and analyzed. The ultra high cis polybutadiene was prepared with the monomeric neodymium catalyst, Nd(neodecanoate)₃·(neodecanoic acid). NUC composites were composed of natural rubber, ultra high cis polybutadiene, and carbon black. In the composite of a low carbon black content (NUC1, 45 phr), a high abrasion‐resistance and a significantly low rolling resistance (tan δ_60°C, 0.04) were obtained. According to the AFM study of NUC composites, abrasion resistance was closely related with surface morphology. In the SUS composites prepared with SSBR (solution styrene–butadiene copolymer), UBR, and silica, as the content of ultra high cis polybutadiene increased, Δcure torque (M_H–M_L) increased with fast cure kinetics. SUS4 showed high elongation and tensile strength with excellent abrasion resistance. Rolling resistance was improved as the content of ultra high cis polybutadiene increased. The SBC composites were prepared with SBR (emulsion styrene–butadiene copolymer), ultra high cis polybutadiene (or high cis polybutadiene), and carbon black. It is remarked that abrasion resistance and Δtan δ (tan δ _60°C ? tan δ_0°C) are increased with ultra high cis polybutadiene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thin‐film nanostructure and polymer architecture in semicrystalline syndiotactic poly(p‐methylstyrene)–(cis‐1,4‐polybutadiene) multiblock copolymers

The thin‐film morphology of stereoregular syndiotactic poly(p‐methylstyrene)–(cis‐1,4‐polybutadiene) (sP(pMS–B)) multiblock copolymers has been investigated using tapping mode atomic force microscopy with variation of the polymer composition and monomer block lengths. The morphology of the thin films ranges from isolated circular domains of sP(pMS) embedded into a matrix of polybutadiene (PB) to isolated domains of PB embedded into a matrix of sP(pMS), passing through bicontinuous (jagged) lamellae when the pMS concentration is in the range 20–67 mol%. Multiple folding of the polymer segments, i.e. where reciprocal inclusions of polymer segments to each other phase are able to generate greater domain, has been postulated and validated by considerations on the polymer architecture and the thermal and crystalline behaviour. © 2019 Society of Chemical Industry     

LIQUID-GEL EXTRACTION OF U-ACYLPYRAZOL-5-ONATO COPPER COMPLEXES

Extracting hydrophobic gels have been prepared by swelling cross-linked polybutadiene with solutions of 4-acylpyrazol-5-ones (HL) in toluene, chloroform and carbon tetrachloride. The extraction of copper from perchlorate medium has been studied. Distribution curves close to those obtained in the pure liquid-liquid extraction show that the polymer has no effect on the thermodynamics of the liquid-gel extraction. The diffusion of the copper chelates CuL₂into the gels appears as a controlling rate factor of the extractions which depends on the polybutadiene cross-linkage.     

Thermoplastic interpenetrating polymer networks based on a poly(styrene-b-butadiene) copolymer and an ionically-terminated polybutadiene ionomer

Thermoplastic interpenetrating polymer networks (IPN) are mixtures of two physically crosslinked polymers. Thermoplastic IPNs were prepared by blending an SBS triblock elastomer with a 1,2-polybutadiene that was ionically-terminated at both ends. The morphologies of these IPNs were studied using differential scanning calorimetry and dynamic mechanical thermal analysis. It was concluded that the ionomer was incompatible with the SBS elastomer, since the T_gs of both the 1,2-polybutadiene from the ionomer and the essentially 1,4-polybutadiene from the SBS component were observable at temperatures that were close to those of the individual components. The addition of the polybutadiene material had, however, an influence on the relaxation processes of the polystyrene blocks. The polystyrene glass transition in the pure SBS copolymer is broadened by the interfacial region between polystyrene and polybutadiene. The low temperature shoulder was much more pronounced when the ion-terminated polybutadiene was present, indicating it has a preference to be located in these interfacial regions. © 1994 John Wiley & Sons, Inc.     

Thermomechanical investigation of hydroxyl-terminated polybutadiene-based linear polyurethane elastomers

The present work describes the trend of linear polyurethane elastomers for its thermal and mechanical behavior. The linear polyurethane elastomers have been synthesized in two different series by changing the composition of the polymers. Both series have common macrodiol of hydroxyl-terminated polybutadiene and butanediol while they vary in the presence of diisocyanate. One of the series, contain an aromatic diisocyanate, toluene diisocyanate (TDI), and the other consist of 1,6-hexamethylene diisocyanate (HDI) as an aliphatic diisocyanate. For linear structure, ratio of OH and NCO group has been maintained 1.0. The hydrogen bonding index is determined from Fourier transform infrared to calculate the extent of interchain hydrogen bonding which manifest the microphase separation. Young's modulus (5.79 MPa) and tensile strength (1.14 MPa) are recorded for HDI-derived elastomers, while Young's modulus varies from 1.14 to 1.63 MPa for TDI-based elastomers which also resulted in higher thermal stability. Thermogravimetric curves exhibit two-step degradation with the stability of 300 °C. HDI-based polyurethane elastomers show better tensile properties and HDI but poor thermal stability as compared to TDI-based elastomers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47289.     

Preparation and properties of graft and block copolymers of poly(p-phenylene terephthalamide) with polybutadiene

Graft copolymers of polybutadiene (PBD) onto poly(p-phenylene terephthalamide) (PPTA) were prepared by the nucleophilic substitution of N-metalated PPTA with telechelic PBD having bromide end groups. Block copolymers were synthesized by the condensation reaction of telechelic PBD having acid chloride end groups with amino-group-terminated PPTA. The structure of these copolymers was identified by IR spectra. Graft and block copolymers contained PBD segments up to 85 wt % and 45 wt %, respectively. Thermomechanical analyses (TMA) proved the existence of distinctive primary absorption peak corresponding with T_g of PBD for both graft and block copolymers. The T_g's of both types of the copolymers were further ascertained by the DSC curves. TMA curves suggested that the microphase separation occurred between PPTA and PBD. The incorporation of PPTA segments into PBD increased the decomposition temperature compared with the blend polymer composed of PPTA and PBD with the same composition.     

Determination of platelet-activating factor by a chemiluminescence method and its application to stimulated guinea pig neutrophils

A simple, rapid and sensitive chemiluminescence method has been developed to measure platelet-activating factor (PAF). Hydrogen peroxide generated from PAF, upon phospholipase D cleavage, by choline oxidase is determined as chemiluminescence by a luminol-microperoxidase system. The detection limit of PAF by this method is 5 pmol/tube. The method is reproducible with a 5.5% coefficient of variation at 10 pmol of PAF (n=5). Lipids were extracted from guinea pig neutrophils after stimulation with cytochalasin B andN-formyl-methionyl-leucylphenylalanine, and PAF was isolated by high-performance liquid chromatography and determined by chemiluminescence measurements. The amount of PAF detected was 96.1±39.7 (mean ± SD, n=7) pmol/10⁸ cells. This highly sensitive method could be useful for the determination of PAF generated under pathophysiological conditions. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Polytriazoles based on alkyne terminated polybutadiene with and without urethane segments: Morphology and properties

Alkyne terminated polybutadiene with urethane segments (PUPB), a well‐controlled macromolecule, is synthesized with a two‐step routine and characterized by ¹H NMR, IR spectroscopy as well as gel permeation chromatograph. Alkyne terminated polybutadiene without urethane segments (PTPB) is also synthesized and characterized. The two alkyne terminated polybutadiene are cured to generate corresponding polytriazoles. It is found that the mechanical properties of PUPB based polytriazoles are superior to that of PTPB. The fractured surfaces of PTPB based polytriazoles exhibit smooth microstructures whereas PUPB based polytriazoles show the rough microstructures. The atomic force microscopy images reveal well‐established microphase‐separated morphology in polytriazoles with the promotion of urethane segments. Thus, the strong hydrogen bonding interaction existed in urethane has a remarkable effect on the morphology and then the mechanical properties of the as‐prepared polytriazoles. In addition, dioctyl sebacate can serve as an excellent plasticizer to PUPB based polytriazoles, lowering the glass transition temperature (T_g) and improving the ductility. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45178.     

FTIR spectroscopic characterization of hydrogenated polyoctenamer and polynorbornene and DSC study of their thermal properties

Diimide-hydrogenated polyoctenamer and polynorbornene have been characterized by FT-infrared spectroscopy and differential scanning calorimetry (DSC). Hydrogenated polyoctenamer has been studied in comparison with hydrogenated polybutadiene and polyethylene. A crystallinity ranging from 71% to 77% was found, while the melting point of hydrogenated polyoctenamer was found to be in the range 127–129°C. Hydrogenated polyoctenamer as well as hydrogenated polybutadiene resemble high density polyethylene (HDPE). Polynorbornene, which is completely amorphous, after hydrogenation shows a certain degree of crystallinity and a melting point of 140.8°C.     

Green analogs of polybutadienes from carbon dioxide and epoxy-based feedstocks

Polybutadiene has widespread use as a commodity as well as a specialty polymer, but currently, it is prepared from non-renewable feedstocks. Herein, we report the synthesis of rubbery unsaturated polycarbonates (RUPCs) as green alternatives for polybutadiene. We prepared two RUPCs (respectively, denoted as RUPC1 and RUPC2) via the copolymerization of carbon dioxide (CO₂) and a mixture of saturated and unsaturated long-chain epoxides using a Co(III) catalyst. The RUPCs were reacted with a styrene monomer via free-radical polymerization to prepare RUPC-graft-Polystyrene. All of the prepared polymers were characterized by ¹H nuclear magnetic resonance spectroscopy and gel permeation chromatography. For RUPC, the number average molecular weight (M_n) increased by three-fold after the grafting reaction. Differential scanning calorimetry analysis confirmed that the glass transition temperature (T_g) of the RUPCs were low (~ −40°C) and approached those of polybutadienes. After polystyrene chains had been grafted onto the RUPC backbone, the T_g increased to 81°C. These green RUPCs have the potential to replace non-renewable polybutadiene in some applications such as high impact materials.     

Preparation and characterization of high‐impact polystyrene using different types of polybutadiene

The mechanical, morphological, and rheological properties of polymer blends based on polystyrene (PS) and three different types of polybutadiene (PB) were studied. The polymer blends containing 20% of PB were processed in a Haake mixer at 180°C and 60 rpm for 6 min. The materials exhibited impact strength superior to that of the PS. An increase was observed in the impact strength of 138, 208, and 823%, when low‐cis polybutadiene (PB_l), high‐cis polybutadiene (PB_h), and styrene–butadiene block copolymer (PB_co), were respectively used. The materials presented dispersed morphology with polybutadiene domains, with sizes inferior to 1 μm, randomly distributed in the PS matrix. The viscous and storage moduli increased as the applied frequency increased. The flow activation energy, calculated by Arrhenius equation, varied from 34 to 71 kJ/mol. In the rheological experiments all polymer blends presented pseudoplastic behavior, showing decreasing viscosities as the shear rate increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Stress-induced chemiluminescence from nylon 66 fibers

The emission of visible light during the tensile deformation of medium- and high-tenacity nylon 66 yarns in air has been studied at strain rates of 0.63–200%/min and at temperatures of 20–110°C. Emission is observed only in an oxidative atmosphere and increases with temperature according to an Arrhenius relation. The activition energy decreases with applied stress. The intensity at any temperature can be described by the sum of a component linear with stress and another exponential in stress above ～60% of the ultimate strength. These results and the measured spectral distribution suggest that light emission arises from bimolecular termination of alkyl peroxy macroradicals. The chemiluminescence growth curves indicate that the applied stress increases the oxidation rate of the fiber due to internal and external frictional heating while, at high strains, stress-induced main-chain scission occurs up to fiber failure. The growth curve is sensitive to the load history of the fiber. The chemiluminescence decay curves are a sensitive probe of radical reactions such as cage termination and stabilizer scavenging in the amorphous region of the polymer.     

Crystallization kinetics of cis‐1,4‐polybutadiene

The isothermal and nonisothermal crystallization kinetics of cis‐1,4‐polybutadiene has been investigated with respect to the content of cis units and the linearity of the main chain. The rate of spherulite growth increases with chain regularity as the presence of branches as well as segments with different configurations slows the crystallization rate. The major parameter that determines the crystallization rate is the presence in the formulation of heterogeneities that favor the formation of primary nuclei and determine an anticipated onset of crystallization. As the activity of the heterogeneous nuclei depends more on the type and number of foreign particle than on any chain parameter, no straightforward information on the influence of the chain structure on the crystallization rate can be derived by mere calorimetric analysis, at least for analyzed samples. It is only with combined analysis by optical microscopy that comprehensive information on the crystallization kinetics of cis‐1,4‐polybutadiene can be derived. The results reported in this contribution point out the importance, in polymer science, of preferring complementary instrumentation and not limiting experimental investigations to a single technique of analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010