Unsaturated polyester as compatibilizer for styrene–butadiene (SBR)/acrylonitrile–butadiene (NBR) rubber blends

The effect of the addition of 5 and 10 phr of unsaturated polyester resin (UPE) on the compatibility and physicomechanical properties of styrene–butadiene (SBR) and acrylonitrile–butadiene (NBR) rubber blends was studied. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), electrical, and ultrasonic techniques were used to determine the degree of the compatibility (DC). The results obtained revealed that, by the addition of 10 parts per hundred parts of rubber (phr) UPE as a compatibilizer for SBR/NBR blends, the degree of compatibility was greatly enhanced. The rheological and mechanical properties of the blends were also improved. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2314–2321, 2002     

The role of a dechlorinated PVC as compatibiliser for PVC/polyethylene blends

Summary Reductive dechlorination of PVC was carried out to obtain a compatibiliser for PVC/polyethylene blends. The performance of this modified PVC is compared with the compatibilising effect of a random chlorinated polyethylene copolymer, analyzing morphology as well as rheological and mechanical properties. Received: 17 July 2001 /Revised version: 16 February 2002/ Accepted: 24 March 2002     

Reactive compatibilization and properties of recycled poly(ethylene terephthalate)/polyethylene blends

Summary Blends of recycled poly(ethylene terephthalate) (R-PET) and high-density polyethylene (R-PE), obtained from post-consumer packaging materials, were prepared both by melt mixing and extrusion processes and compatibilized by addition of various copolymers containing functional reactive groups, such as maleic anhydride, acrylic acid and glycidyl methacrylate. The effect of the type and concentration of compatibilizer, as well as the mixing conditions, on the phase morphology, thermal behaviour, rheological and mechanical properties of the blends was investigated. The results indicated that addition (5÷10 pph) of ethylene-co-glycidyl methacrylate copolymer (E-GMA) allows for a marked improvement of processability and physical/mechanical performances of R-PET/R-PE blends. Received: 1 March 2001/Revised version: 15 November 2001/ Accepted: 28 January 2002     

Morphology and micromechanical deformation behavior of styrene/butadiene‐block copolymers. I. Toughening mechanisms in asymmetric star block copolymers

Lamellae‐forming styrene/butadiene star block copolymers are studied to investigate the influence of morphology on micromechanical deformation mechanisms and mechanical properties by using transmission electron microscopy and tensile testing. A large homogeneous plastic deformation of polystyrene (PS) lamellae is found in styrene/butadiene star block copolymers on the basis of the new mechanism called thin‐layer yielding. This mechanism depends strongly on the thickness of the PS lamellae. At a critical thickness of PS lamellae of about 20 nm, a transition from thin‐layer yielding mechanism to a crazelike deformation was observed. These new deformation zones are similar to crazes with respect to their propagation perpendicular to direction of external stress and similar to shear bands with respect to an internal shear deformation component of the lamellae in the deformation zones. As a result of our investigations, the mechanical properties of star block copolymers can be understood in correlation with morphology and micromechanical deformation mechanisms. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 683–700, 2002     

Acoustic properties of nitrile butadiene rubber for underwater applications

Acoustic properties of nitrile butadiene rubber (NBR) specimens with carbon black as filler were investigated with different sulfur contents in the frequency range of 300‐1000 kHz. Their mechanical properties, such as density, hardness, tensile strength, were conventionally measured and correlated with their acoustic properties. Sound speeds in the specimens were increased with an increase in the sulfur content. The variation of sound speed was about 2–5% in the specimens, whereas the variation of density was less than 0.4%. Enhanced acoustic transmission was also observed with increasing sulfur content. It may be due to the hardness change from the increase of crosslinking density in the specimens. These results show that the mechanical properties of NBR can be nondestructively and accurately determined with the acoustic property measurements. By use of the desired mechanical and acoustic properties, the utilization of the NBR for underwater applications becomes less d ficult. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2764–2771, 2002     

Preparation,structure, and properties of a novel rectorite/styrene–butadiene copolymer nanocomposite

Rectorite/styrene–butadiene copolymer (SBR) nanocomposite was prepared by cocoagulating SBR latex and rectorite/water suspension. Transmission electron microscopy showed that the layers of rectorite were well dispersed in the SBR matrix and the aspect ratio (width/thickness) of it was higher than that of montmorillonite (MMT). X‐ray diffraction indicated that the nanocomposite produced by this method was of neither intercalated type nor exfoliated type. The gas barrier properties and mechanical properties of the novel nanocomposites were excellent. The nanocomposites are expected to be candidates for tire tube or inner materials. Rectorite appears to be a promising filler for the nanocomposite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 324–328, 2005     

Viscoelastic properties of heterophase blends of homopolymers and block copolymers

Stress relaxation and dynamic mechanical measurements were carried out for two types of heterophase polyblends. One is obtained by blending homopolymers of butadiene and styrene (high impact polystyrene or HIPS); the other by blending homopolymer of butadiene with a triblock copolymer of styrene-butadiene-styrene (SBS/B). It was found that for HIPS, time temperature superposition is difficult, and the shift factors cannot be adequately interpreted by a reasonable model. For SBS/B it is impossible to carry out superposition. Modulus-temperature and loss tangent curves determined by dynamic mechanical experiments indicate the presence of new transition near ?40°C. Possible mechanisms giving rise to this new transition are discussed.     

Dynamic mechanical properties of polycarbonate and acrylonitrile–butadiene–styrene copolymer blends

Blends of polycarbonate (PC) and poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) with different compositions are characterized by means of dynamic mechanical measurements. The samples show phase separation. The shift in the temperatures of the main dynamic mechanical relaxation shown by the blend with respect to those of the pure components is attributed to the migration of oligomers present in the ABS toward the PC in the melt blending process. A comparison with other techniques (dielectric and calorimetric analysis) and the application of the Takayanagi three block model confirm this hypothesis. In all the studied blend compositions (ABS weight up to 28.6%) the PC appears as the matrix where a disperse phase of ABS is present. The scanning and transmission electron microscopy micrographs show that the size of the ABS particles increases when the proportion of ABS in the blend increases. The FTIR results indicate that the interaction between both components are nonpolar in nature and can be enhanced by the preparation procedure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1507–1516, 2002     

The effect of mercapto‐modified EVA on rheological and dynamic mechanical properties of NBR/EVA blends

The effect of mercapto‐modified ethylene vinyl acetate copolymer (EVALSH) on the rheological and dynamic mechanical properties of acrylonitrile butadiene rubber (NBR) and ethylene vinyl acetate copolymer (EVA) blends was evaluated at different blend compositions. The addition of 5 phr of EVALSH in the blends resulted in an increase of the melt viscosity and a substantial decrease of the extrudate swell ratio. These results can be attributed to the interactions occurring between the double bond of the NBR phase and the mercapto groups along the EVALSH backbone. The power–law index also presents a slight increase in the presence of EVALSH, indicating a decrease in the pseudoplastic nature of the compatibilized blends. The reactive compatibilization of NBR/EVA blends with EVALSH was also confirmed by the decrease of damping values and an increase of glass transition temperature, in dynamic mechanical analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2335–2344, 2002     

The effect of structural features on mechanical properties of loose optical fiber poly(butylene terephthalate) tubes

Results of a study on the modifying mechanical properties of loose optical‐fiber poly(butylene terephthalate) (PBT) tubes, produced during the standard industrial extrusion process, show that heat treatment make the structure of their material to change. The study comprised measurements of mechanical strengths properties of the tubes (tensile strength, compression strength, kinking) and determination of tube material structure [by differential thermal analysis (DTA), wide angle X‐ray scattering analysis (WAXD), and scanning electron microscopy (SEM)]. Results of the study allowed observation that the annealing at 70°C for 34 h of the tubes caused the crystalline α phase to increase in the tube material from ～28.5% to ～31.5% and the structure of the existing crystallites to become more perfect. This made the values of certain mechanical properties of the tubes to increase even by as much as 30%. The tubes following such thermal treatment could be used in cables exposed to heavy‐duty operation in arduous environments, where a larger margin from the standpoint of mechanical properties is required. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2130–2134, 2002     

Rubber-modified epoxy resins: 1. Equilibrium physical properties

Dilatometry, thermal mechanical analysis, differential scanning calorimetry, electron microscopy and mechanical measurements are reported on a series of rubber-modified epoxy resins. The data obtained is discussed in terms of the interplay of molecular mobility, network and domain structure of the resins. Three transitions were identified; two being assigned respectively to the onset of motion of the acrylonitrile/butadiene units and epoxy units. The higher temperature transition is more difficult to assign, but appears to be associated with specific interactions involving the interface between the epoxy and acrylonitrile/butadiene interfaces or the crosslinked regions of the epoxy resin.     

Recycling of ABS and ABS/PC blends

The aim of this work within the framework of mechanical recycling of polymers is upgrading recycled engineering plastics by means of a blending technique. Four different plastics from dismantled Volvo cars have been investigated. They are poly(acrylonitrile‐butadiene‐styrene) (ABS) and ABS‐polycarbonate (ABS/PC) as major components and poly(methyl methacrylate) (PMMA) and polyamide (PA) as minor components. Blending recycled ABS and PC/ABS (70/30) with a small amount of methyl methacrylate‐butadiene‐styrene core‐shell impact modifiers gives the mixture better impact properties than any of its individual components. Some 10% of PMMA from tail light housings can follow the PC/ABS blends made. The property profile will rather be improved. However, PA is an incompatible component that should be sorted out from the mixture. Antioxidants and metal deactivators do not help the recyclates show better mechanical properties. Two toughness measurements, Charpy impact strength and J‐integral method, show complimentary results for such blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 510–515, 1999     

Oxazoline‐containing compatibilizers for polyamide/SAN and polyamide/ABS blends

Polyamide (PA) and acrylonitrile/butadiene/styrene copolymer (ABS) may appear as a mixture in the recycled plastic stream. The incompatibility of these blends results in a blend with poor mechanical properties. The aim of this work is to partially convert the nitrile groups of the acrylonitrile/styrene copolymer (SAN) into oxazoline groups by reaction with aminoethanol (AE). Such modified SAN (SAN‐m) can react with the amine or carboxylic acid end groups of PA, and therefore used as compatibilizers for blends of PA with ABS. SAN‐m was found to reduce the SAN‐domain size in the PA/SAN‐blends. The initial acrylonitrile content of SAN‐m had a strong influence on the degree of conversion into oxazoline groups and on the compatibilizing effect. Mechanical properties of SAN‐m compatibilized PA/ABS blends were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 449–455, 2002     

Blends of i‐PP and SBS. I. Influence of the in situ compatibilization on the morphology

This article concerns the in situ compatibilization of immiscible isotactic polypropylene/butadiene‐styrene‐butadiene triblock copolymer blends (i‐PP/SBS) by means of a reactive mixture. For this purpose, maleated PP (PP‐MAH) and SBS (SBS‐MAH) were used as functionalized polymers and 4,4′‐diaminediphenylmethane was used as a coupling agent between maleated polymers, resulting in a graft copolymer. Binary blends i‐PP/SBS, nonreactive ternary blends i‐PP/PP‐MAH/SBS, and reactive ternary blends i‐PP/PP‐MAH/SBS‐MAH with varying diamine and anhydride molar ratios were prepared. Torque measurements suggest a graft copolymerization during the melt blending for ternary reactive blends, but the extension of the grafting does not vary with the diamine and anhydride molar ratio, but with the elastomer concentration. The morphology of the blends was investigated by scanning electron microscopy. The morphology of binary and ternary nonreactive blends is similar, exhibiting elastomer domains disperse in the i‐PP matrix, whose sizes increase with elastomer concentration. On the other hand, the elastomer domain size in the ternary reactive blends is practically independent of the blends composition and of the diamine and anhydride molar ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 847–855, 2002     

Novel Polyisobutylene Stars. XXVIII. A star block comprising three poly (isobutylene-b-acrylonitrile) arms radiating from an aromatic core: Synthesis and characterization*

Summary The synthesis and characterization of a novel three arm star-block comprising a cumyl core out of which radiate three poly(isobutylene-b-acrylonitrile) arms is presented. The synthesis strategy comprised three major steps (see Scheme 1): 1. The synthesis of ?(PIB-OH)₃, 2. Quantitative transformation of the -OH termini to -OCOC(CH₃)₂Br termini, and 3. Controlled ATRP of acrylonitrile mediated by the latter termini. The definition of a suitable solvent system, methylene chloride/cyclohexanone (CH₂Cl₂/CHO) was critical for the synthesis. The ?(PIB-b-PAN)₃, M_{n,PIB block}= 6000 g/mol and M_{n,PAN block}= 1,800 g/mol was characterized by solid state ¹³C NMR spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. Received: 8 January 2002/Revised version: 4 March 2002/ Accepted: 5 March 2002     

Atom transfer radical polymerizations of styrene and butadiene as well as their copolymerization initiated by benzyl chloride / 1-octanol-substituted MoCl<Subscript>5</Subscript> / PPh<Subscript>3</Subscript>

A novel initiator system, benzyl chloride / 1-octanol-substituted MoCl₅ / triphenyl phosphine (PPh₃), was applied to the atom transfer radical polymerizations (ATRP) of both butadiene and styrene as well as their copolymerization. Characterization revealed a linear increase in the number average molecular weight with monomer conversion and rather wide molecular weight distributions of the polymerization products. Increasing the polymerization temperature promoted the reaction rate and narrowed the polydispersity index of polystyrene proportionally. The polymerization rule for butadiene catalyzed by the above Mo-based system catalyst is similar to that of styrene. The microstructure of the butadiene was investigated by IR and ¹H NMR. IR, ¹³C NMR and DSC measurements showed that the butadiene and styrene copolymer was a random copolymer. The chlorine atom at the ω end group of the polymer and the change in the valence state of molybdenum, as explored by UV-Vis spectroscopy, revealed that the polymerization proceeded in a manner closest to the mechanism of ATRP.     

Phase structure of solution cast films of α-methylstyrene/butadiene/styrene block copolymers

The phase structure of solvent cast films of α-methylstyrene/butadiene/styrene of differing compositions was investigated using physical methods. Both dynamic mechanical and differential scanning calorimetry measurements exhibited a single high temperature transition at 150°C. The transition has been shown to originate from a composite domain of the two glassy end blocks. Light scattering measurements showed that these domains varied in size from 0·35 to 0·40 μm and that they are randomly arranged within the butadiene matrix. The results are compared with the results of similar studies of ABA systems.     

THE IMPORTANCE OF SOLVENT COMPOSITION AND ADSORPTION EFFECTS ON THE FLOW PROPERTIES OF

Capillary rheometry data are presented for concentrated solutions of polybutadiene dissolved in mixed volatile solvent systems composed of benzene, butadiene, and butene 1. Unusual flow phenomena, associated with polymer adsorption at capillary tube walls, are observed for polybutadiene in a solvent composed of benzene and butene 1, but not observed at the same polymer concentration in a pure benzene solvent or for a mixed binary solvent where the butene 1 is replaced by butadiene. The unusual flow phenomena include a diameter dependency in the viscosity measurements when end effects are eliminated, and a diameter dependency in the end correction itself. Correction of the diameter dependent viscosity data is successfully made by postulating an effective negative slip velocity (polymer adsorption). The thickness of the polymer adsorbed layer relative to the tube diameter is of the same order as observations for other polymer solutions both in capillary and packed bed flows. It is argued that the flow phenomena observed in the polybutadiene-benzene-butene 1 solutions and not observed in the polybutadiene-benzene-butadiene solutions of identical composition is related to the solvent system itself—benzene and butadiene being a good mixed solvent for polybutadiene relative to benzene and butene 1 in the same ratio. The work was initiated and completed in response to material handling problems encountered in a commercial process for the manufacture of polybutadiene.     

Storage modulus changes with temperature in poly(vinyl alcohol), PVA,/poly(acrylic acid), PAA, blends

Summary Poly(vinyl alcohol), PVA, and poly(acrylic acid), PAA, blends were prepared by solution casting. These polymers were found to be miscible in the whole composition range as determined by DSC even though some crystallinity remains in blends with PVA concentrations above 50wt%. Dynamic mechanical measurements of these blends and PAA as a function of temperature show an increase in storage modulus, E', when they reach a temperature of 140°C that is well beyond their softening point. The E' increase in PAA beyond 140°C is attributed to an intramolecular reaction of cyclic anhydride formation that stiffens the chain. Isothermal storage modulus test as a function of time and FTIR measurements at 160°C of PAA and three blends show that this increase in E' is due to cyclic anhydride formation. Received: 4 November 1998/Revised version: 11 March 1999/Accepted: 11 March 1999     

1,2 Syndiotactic polybutadiene of controlled crystallinity by butadiene-isoprene copolymerization with CrCl2·(dmpe)2-MAO

Summary CrCl₂·(dmpe)₂-MAO gives crystalline 1,2 syndiotactic polymers from butadiene and 3,4 atactic polymers from isoprene. Butadiene-isoprene copolymerization gives copolymers in which butadiene and isoprene units have respectively a 1,2 and a 3,4 structure. Copolymers with less than 20% isoprene are crystalline, their melting point decreasing from ca. 160°C to ca. 50°C with increasing isoprene content. This makes possible to obtain 1,2 syndiotactic polybutadiene with controlled melting point. Copolymers with more than 20% isoprene are amorphous, with a glass transition temperature in the range 2÷5°C. Copolymer microstructure was determined by ¹³C NMR. Received: 10 February 2001/Revised version: 12 February 2002/ Accepted: 12 February 2002