Styrene Phase Research Articles

Investigation of the effects of scale and cure environment on the properties of vinyl ester polymer

This work involves the study of the cure kinetics of a commercial bisphenol-epoxy vinyl ester resin as a function of sample thickness and environment atmosphere. It has been previously suggested that cured vinyl ester polymer is a diphasic material consisting of a lower Tg styrene phase and a higher Tg vinyl ester phase. The cure kinetics of each phase have been observed to have a significant effect on the thermal properties of the system, such as the degree of crosslinking, glass transition temperature and final conversion. DSC, DMA and FTIR were employed to characterize two vinyl ester resin systems and study the material property transferability from macroscale to microscale. The effect of reduced styrene content on resin curing and polymer thermal behaviour was studied. The effect of oxygen interaction during initial cure was investigated at both microscale and macroscale and found to have a significant effect on final polymer performance.

The Role of Lipid Chains as Determinants of Membrane Stability in the Presence of Styrene

Biofermentative production of styrene from renewable carbon sources is crucially dependent on strain tolerance and viability at elevated styrene concentrations. Solvent-driven collapse of bacterial plasma membranes limits yields and is technologically restrictive. Styrene is a hydrophobic solvent that readily partitions into the membrane interior and alters membrane-chain order and packing. We investigate styrene incorporation into model membranes and the role lipid chains play as determinants of membrane stability in the presence of styrene. MD simulations reveal styrene phase separation followed by irreversible segregation into the membrane interior. Solid state NMR shows committed partitioning of styrene into the membrane interior with persistence of the bilayer phase up to 67 mol % styrene. Saturated-chain lipid membranes were able to retain integrity even at 80 mol % styrene, whereas in unsaturated lipid membranes, we observe the onset of a non-bilayer phase of small lipid aggregates in coexistence with styrene-saturated membranes. Shorter-chain saturated lipid membranes were seen to tolerate styrene better, which is consistent with observed chain length reduction in bacteria grown in the presence of small molecule solvents. Unsaturation at mid-chain position appears to reduce the membrane tolerance to styrene and conversion from cis- to trans-chain unsaturation does not alter membrane phase stability but the lipid order in trans-chains is less affected than cis.

Porous layer open-tubular column with styrene and itaconic acid-copolymerized polymer as stationary phase for capillary electrochromatography-mass spectrometry.

Enhancing the specific surface area of stationary phase is important in chromatographic science, especially in open-tubular column in which the coating only exists on the inner surface. In this work, a porous layer open-tubular (PLOT) column with stationary phase of styrene and itaconic acid-copolymerized polymer was developed. Thermal-initiated polymerization method with strategies like controlling the ratio of reaction reagents to solvents and reaction time, confinement by the narrow inner diameter of capillary were used for preparing the stationary phase with uniform structure and relatively thick layer. Due to the high separation efficiency and capacity, the PLOT column was used for capillary electrochromatography (CEC) separation of multiple groups of analytes like alkylbenzenes, phenyl amines, phenols, vanillins, and sulfonamides with theoretical plates (N) up to 1,54,845 N/m. In addition, due to high permeability of the CEC column and large electroosmotic flow mobility generated by abundant carboxyl groups in the coating material, the PLOT-CEC column was successfully coupled with mass spectrometry (MS) through a sheath flow interface. The developed PLOT-CEC-MS method was used for the analysis of antiseptics like parabens and herbicides like pyridines.

Effect of acrylonitrile–butadiene–styrene/polyethylene terephthalate blends on dimensional stability, morphological, physical and mechanical properties and after aging at elevated temperature

A melt blending method was used to prepare acrylonitrile–butadiene–styrene terpolymer and polyethylene terephthalate blends to develop a new blend which can withstand higher temperatures required especially for automotive or home appliance paint curing processes. Blends were characterized by rheological, thermal and mechanical properties. Dimensional stability at 125°C was used to correlate with injection molded part shrinkage. The melt viscosity–composition curves for acrylonitrile–butadiene–styrene/polyethylene terephthalate blends exhibited a trend like the rule of mixtures in which adding acrylonitrile–butadiene–styrene to polyethylene terephthalate improved the processability. Scanning electron microscopy examination revealed different morphologies depending on the composition such as dispersed, co-continuous and phase inverted, which indicated that the binary blends were immiscible and form a two-phase structure. Tensile properties increased with an increase in the polyethylene terephthalate content while the unnotched impact strength reached a maximum at 40 wt.% acrylonitrile–butadiene–styrene content. In differential scanning calorimetry analysis, no partial miscibility was observed from the polyethylene terephthalate phase melting temperature shifts as compared to those of the neat component. Also, acrylonitrile–butadiene–styrene phases acted as nucleating agents due to change in polyethylene terephthalate cold crystallization temperature. In applied post shrinkage measurements by heat aging, we saw that the acrylonitrile–butadiene–styrene dimensional stability was improved with added polyethylene terephthalate.

Microbeads and hollow microcapsules obtained by self-assembly of pickering magneto-responsive cellulose nanocrystals.

Cellulose microbeads can be used as immobilization supports. We report on the design and preparation of magneto-responsive cellulose microbeads and microcapsules by self-assembled shells of cellulose nanocrystals (CNC) carrying magnetic CoFe2O4 nanoparticles, that is, a mixture of isotropic and anisotropic nanomaterials. The magnetic CNCs formed a structured layer, a mesh, consisting of CNCs and magnetic particles bound together on the surface of distinct droplets of hexadecane and styrene dispersed in water. Because of the presence of CNCs the highly crystalline mesh was targeted to provide an improved barrier property of the microbead shell compared to neat polymer shells, while the magnetic particles provided the magnetic response. In situ polymerization of the styrene phase led to the formation of solid microbeads (∼8 μm diameter) consisting of polystyrene (PS) cores encapsulated in the magnetic CNC shells (shell-to-core mass ratio of 4:96). The obtained solid microbeads were ferromagnetic (saturation magnetization of ∼60 emu per gram of the magnetic phase). The magnetic functionality enables easy separation of substances immobilized on the beads. Such a functionality was tested in removal of a dye from water. The microbeads were further utilized to synthesize hollow microcapsules by solubilization of the PS core. The CNC-based, magneto-responsive solid microbeads and hollow microcapsules were characterized by electron microscopy (morphology), X-ray diffraction (phase composition), and magnetometry (magnetic properties). Such hybrid systems can be used in the design of materials and devices for application in colloidal stabilization, concentration, separation, and delivery, among others.

Influence of the epoxidation degree of a polystyrene–polybutadiene–polystyrene (SBS) triblock copolymer on the compatibilization with an organomodified nanoclay

In this work, the addition of organophilic-modified montmorillonite into polystyrene–polybutadiene–polystyrene (SBS) triblock copolymers was investigated with and without the use of epoxidized SBS as a compatibilization agent. The nanocomposites were prepared by melting mixture at 60 rpm and 130 °C. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), tensile tests, and dynamic-mechanical analysis (DMA). XRD and TEM showed the formation of an intercalated dispersion of clay platelets oriented on the SBS surface. The AFM showed the typical lamellar microstructure of the styrene and butadiene phases of SBS. The estimation of the average distance between the styrene lamellae by AFM analysis showed that the platelets are anchored between the phases, and this structural feature caused an increase in elastic modulus. DMA analysis showed that the T g of butadiene decreased in the nanocomposites. The decrease of the T g and the increase in the elastic modulus are correlated to mechanisms at the micro- and the macro-scales, respectively. The decrease in the T g indicates flexibilization at the interface, whereas the intercalation of the platelets restricted the interphase macroscale deformation.

Electric‐Field‐Induced Alignment of Block Copolymer/Nanoparticle Blends

External electric fields readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-field-induced alignment of a lamellae-forming polystyrene-block-poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-field-assisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such films under benign experimental conditions.

Effects of stirring prior to starting emulsion polymerization of styrene with nonionic emulsifier on particle formation and its incorporation

Emulsion polymerization of styrene with a nonionic emulsifier (polyoxyethylene nonylphenyl ether, E911) and potassium persulfate as initiator was carried out at different stirring rates (240–500 rpm) at 70 °C, which was started by the addition of initiator after stirring for 100 min at 70 °C. Resulting polystyrene (PS) particles at 240 rpm were 70-nm-sized, spherical particles and incorporated only 5 wt.% of total E911. On the other hand, particles at 500 rpm were 1-μm-sized, nonspherical particles, which were formed by coagulation of small particles, and incorporated above 70 wt.% of E911 in the inside. Before starting emulsion polymerization, E911 and styrene, respectively, transferred from an aqueous phase to a styrene phase and from the styrene phase to the aqueous phase (water and micelles) faster at 500 rpm than 240 rpm. At 240 rpm, there were a lot of almost empty micelles (ca. 5 nm) in the aqueous phase, on the other hand at 500 rpm, 70 wt.% of total E911 transferred to the styrene phase and the micelles were swollen with much monomer (ca. 40 nm) even if the number was smaller. Stirring prior to starting the emulsion polymerization greatly affected partitionings of monomer to the aqueous phase and the nonionic emulsifier to the styrene phase, resulting in the differences in the particle formation and the incorporation of the nonionic emulsifier inside PS particles.

STUDY OF MECHANICAL BEHAVIOR OF REPROCESSING HIGH IMPACT POLYSTYRENE, RECOVERY WITH SEBS

The effect of reprocessing High Impact Polystyrene (HIPS) has been studied in this paper. To simulate recycled HIPS, we reprocessed virgin HIPS through 5 cycles. The HIPS has been mechanically characterized after the various cycles of reprocessing in order to evaluate their corresponding properties and correlate them with the number of cycles undergone. Our results show that tensile strength increases, while lengthening at break decreased as the number of reprocessing cycles increases. 1. INTRODUCCTION High Impact Polystyrene is a thermoplastic formed in two phases: a styrene phase and a butadiene phase. Among the diverse applications of this material is its use in the manufacture of packaging materials. This type of product can be characterized as having a short life cycle, and consequently a huge quantity of domestic waste is generated, which must be dealt with to reduce environmental impact. The problems which arise in the recovery of polymer materials are basically the variations that occur in their properties, due to either thermic degradation or the presence of impurities. Many studies have been carried out on the degradation of polymers. Su (3) analyzed the influence of the reprocessing cycles on the mechanical properties of polyamide 6 (PA6). Su's work is relevant to our work because he carried out a study of mechanical and rheological properties, although it was with a different material. Su's work is interesting, but we do not consider that reprocessing the material 16 times is very useful, because other studies show that the loss of property occurs in the first 5 reprocessed. (2,8) Other authors, including Santana (8) in their work in 2002 and Soriano (3) have carried out similar studies on HIPS. Santana investigated the themo-mechanical properties of post- consumer HIPS (from disposable cups) through five consecutive injection moulding steps to simulating the recycling cycles. Santana states that tensile strength, modulus of elasticity and elongation at break properties of HIPS were slightly reduced, which indicate an effect of decreasing of molecular weight. Soriano analyzes influence of the number of processing cycles on the microstructure and macroscopic properties on a HIPS in coextruded sheet, maintaining a constant composition of 70 wt% of virgin HIPS and 30 wt% of recycled HIPS. On the other hand, Balard (6) analyzed the compatibility of polycarbonate (PC) with acrylonitrile-butadiene-styrene (ABS) using waste material from the electrical sector, reaching the conclusion that the composition range comprised between 10 and 20 wt% PC is most interesting in order to obtain an industrial material with balanced properties, for different reasons: firstly, mechanical ductile properties do not decrease. Secondly, processing conditions are similar to other styrenic derivatives and finally, this composition range reflects the generation ratio of these wastes which is close to 4:1 for ABS/PC. Finally, Navarro (7) and Garcia (1) analyzed mixtures of polymers with the aim of improving properties of the recovered material. Navarro, in his study of the influence of polyethylene (PE) on recycled polyethylene terephtalate (PET) analyzed, among other things, mechanical and rheological properties.

STUDY OF RHEOLOGICAL BEHAVIOR OF REPROCESSING HIGH IMPACT POLYSTYRENE

The effect of reprocessing High Impact Polystyrene (HIPS) has been studied in this paper. To simulate recycled HIPS, we reprocessed virgin HIPS through 5 cycles. The HIPS has been rheologically characterized after the various cycles of reprocessing in order to evaluate their corresponding properties and correlate them with the number of cycles undergone. Our results show that viscosity decrease, as the number of reprocessing cycles increases. 1. INTRODUCCTION High Impact Polystyrene is a thermoplastic formed in two phases: a styrene phase and a butadiene phase. Among the diverse applications of this material is its use in the manufacture of packaging materials. This type of product can be characterized as having a short life cycle, and consequently a huge quantity of domestic waste is generated, which must be dealt with to reduce environmental impact. The problems which arise in the recovery of polymer materials are basically the variations that occur in their properties, due to either thermic degradation or the presence of impurities. Many studies have been carried out on the degradation of polymers. Su (3) analyzed the influence of the reprocessing cycles on the mechanical properties of polyamide 6 (PA6). Su's work is relevant to our work because he carried out a study of mechanical and rheological properties, although it was with a different material. Su's work is interesting, but we do not consider that reprocessing the material 16 times is very useful, because other studies show that the loss of property occurs in the first 5 reprocessed. (2,12) Other authors, including Santana (12) in their work in 2002 and Soriano (3) have carried out similar studies on HIPS. Santana investigated the themo-mechanical properties of post-consumer HIPS (from disposable cups) through five consecutive injection moulding steps to simulating the recycling cycles. Santana states that tensile strength, modulus of elasticity and elongation at break properties of HIPS were slightly reduced, which indicate an effect of decreasing of molecular weight. Soriano analyzes influence of the number of processing cycles on the microstructure and macroscopic properties on a HIPS in coextruded sheet, maintaining a constant composition of 70 wt% of virgin HIPS and 30 wt% of recycled HIPS. With respect to the rheological properties, Soriano shows that the viscosity of the material subjected to one processing cycle is higher than of the virgin material, especially at low shear rate, but as shear rate increases, all, curves tent to concur to a similar value and this difference in viscosities becomes very small. After the second and up to the sixth processing cycle, the viscosity decreases. Soriano calculates the value of n (the model constant which symbolizes the pseudoplastic behavior slope of the material) obtaining a value of 0.31 for virgin material and 0.35 for the sixth processing cycle. This data is calculated from apparent viscosity (ηap) as Soriano used only one die (L/D 30mm) instead of the three recommended by ISO 11443. On the other hand, Balard (10) analyzed the compatibility of polycarbonate (PC) with acrylonitrile-butadiene-styrene (ABS) using waste material from the electrical sector,

Effect of stirring rate on particle formation in emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene

Particle formation during the initial stages of emulsifier-free organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene at 60°C was investigated at two stirring rates (220 and 1000 r.p.m.), in which the styrene phase floated as a layer on an aqueous phase at 220 r.p.m. or became dispersed as droplets at 1000 r.p.m. A water-soluble TERP agent, poly(methacrylic acid) (PMAA)-methyltellanyl (PMAA30-TeMe) and a water-soluble thermal initiator, 4,4′-azobis(4-cyanovaleric acid), at alkaline pH were used. The control/livingness was better at 1000 r.p.m. than at 220 r.p.m., and the particle size distribution was also affected by the stirring rate: both nanometer-sized and submicrometer-sized particles were observed at 220 r.p.m., and mainly nanometer-sized particles were observed at 1000 r.p.m. Because the percentage of PMAA30-TeMe consumed in the initial stage was much higher at 1000 r.p.m. than at 220 r.p.m., self-assembly nucleation preferentially occurred at 1000 r.p.m., resulting in nanometer-sized particles and good control/livingness. Stirring at 1000 r.p.m. only in the initial stage of the emulsion TERP followed by 220 r.p.m. induced good control/livingness and the formation of mainly nanometer-sized particles. It is concluded that a high stirring rate in the initial stage is important for the emulsion TERP of styrene to obtain good control/livingness and to control the particle formation mechanism. Particle formation in an initial stage of emulsifier-free organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene at 60°C was investigated at two stirring rates (220 and 1000 r.p.m.), at which styrene phase floated as a layer on an aqueous phase at 220 r.p.m. or dispersed as droplets at 1000 r.p.m. Because percentage of PMAA30-TeMe consumed in the initial stage was much higher at 1000 r.p.m. than 220 r.p.m., self-assembly nucleation preferentially occurred at 1000 r.p.m., resulting in nanometer-sized particles and good control/livingness.

Poly(styrene-<i>b</i>-butadiene-<i>b</i>-styrene)-Dye-Coupled Polyhedral Oligomeric Silsesquioxanes

Dye-coupled polyhedral oligomeric silsesquioxane (POSS) were prepared and the coloured POSS particles were ultrasonically solution dispersed in poly(styrene-b-butadiene-b-styrene) (SBS). POSS molecules contained either isobutyl or phenyl groups to provide selective compatibility with either the soft (butadiene) or hard (styrene) phase within the block copolymer. The composition and thermal stability were characterised using thermogravimetry. Colour coordinates were measured. Tensile mechanical properties, creep and recovery were determined. Creep was modeled using the 4-element model of Maxwell and Kelvin-Voigt, while recovery correlated with the stretched-exponential function of Kohlrausch, Williams and Watts.

Pickering emulsions stabilized by self-assembled colloidal particles of copolymers of P(St-alt-MAn)-co-P(VM-alt-MAn)

A new type of copolymer containing two alternating segments, poly-(styrene-alt-maleic anhydride)-co-poly (7-(4-vinylbenzyloxyl)-4-methylcoumarin-alt-maleic anhydride) P(St-alt-MAn)-co-P(VM-alt-MAn)(PSMVM), was prepared. The copolymer self-assembled into nanoparticles with internal microphase structures in water because the hydrophilicity of segment P(VM-alt-MAn) is higher than that of P(St-alt-MAn). The particle size, morphology, ζ potential and surface properties and their dependence on the pH and slat concentrations were studied with a combination of techniques. The nanoparticles of PSMVM showed surface activity and pH sensitivity for producing Pickering oil-in-water emulsions. The emulsion volume increased and the size of oil/water droplet decreased with increasing salt concentration. Furthermore, cross-linked nanoparticles (CLPs) were obtained by photo-dimerization of the pendent coumarin groups in PSMVM under UV irradiation. The emulsions produced by using the CLPs as emulsifiers showed even better stability upon standing. Solid oil-phase droplets were obtained by preparation of CLPs-stabilized Pickering emulsions with an oil phase of styrene containing the initiator AIBN followed by the polymerization of styrene. Thus, the enrichment and aggregation of the CLPs on the emulsion droplets was visible because the solid droplets remained unchanged during the SEM sample preparation.

Synthesis of Structurally Stable Colloidal Composites as Magnetically Recyclable Acid Catalysts

In this study, we provide a simple and reproducible method for the preparation of highly active and recyclable colloidal acid catalysts. First, 16-heptadecenoic acid-functionalized magnetite nanoparticles were encapsulated in monodisperse cross-linked polymer spheres. This was achieved by emulsion copolymerization technique in an aqueous phase of styrene and divinylbenzene (DVB). Different ratios of styrene and DVB were used to tune the structural stability and surface morphology of the composites. With increase in DVB content, the surfaces of the colloidal composites become increasingly rougher. The obtained colloids were functionalized with sulfonic acid groups to obtain magnetically recyclable catalysts with H+ contents in the range of 2.2−2.5 mmol g−1 and surface areas of 45−120 m2 g−1. For the condensation reaction of benzaldehyde and ethylene glycol, magnetic acid catalyst prepared only from DVB precursor was found to be active and with high selectivity and long-term stability.

Surface-Initiated Free Radical Polymerization at the Liquid−Liquid Interface: A One-Step Approach for the Synthesis of Amphiphilic Janus Silica Particles

Amphiphilic Janus silica particles with hydrophobic polystyrene (PS) and hydrophilic poly(sodium methacrylate) (PSMA) brushes on two hemispheres were prepared at the liquid-liquid interface by surface-initiated polymerization. After introduction of free-radical initiator modified silica particles into a mixture of styrene and water, the silica particles were adsorbed at the liquid-liquid interface. One hemisphere of a silica particle is immersed in aqueous phase, and the other one is in styrene phase. After initiation at an elevated temperature, PSMA chains grow on one hemisphere and PS chains grow on the other one. Thermogravimetric analysis and infrared spectra results confirmed the grafting of polymer brushes on the surfaces. Transmission electron microscopy was used to characterize the asymmetric surface structure and aggregation structure of the Janus particles.

EFFECT OF COMPOSITON ON THE VISCOELASTIC RELAXATION AND PHASE MORPHOLOGY OF LINEAR STYRENE-BUTADIENE-STYRENE TRIBLOCK COPOLYMERS

研究了不同组成的苯乙烯-丁二烯苯乙烯嵌段共聚物（SBS）的相形态与粘弹弛豫.用透射电子显微镜(TEM)表征了SBS的形态，结果显示，几种SBS均呈层状结构，随着苯乙烯含量的降低，聚苯乙烯（PS）相的尺寸稍有减小，而聚丁二烯（PB）相尺寸明显增大.用动态流变学方法考察了不同温度下SBS嵌段大分子的弛豫行为，结果表明，苯乙烯含量减少，PS相玻璃化转变和有序无序转变温度均降低；苯乙烯含量少的，在有序无序转变过程中呈现出高且宽的损耗峰，表明有序无序转变过程中能量的耗散主要由两相溶合时分子链间的内摩擦所决定，分子链越长，内摩擦越大，能量耗散越大.

Heterophase polymerization of styrene in the presence of organosilicon compounds of various natures

The heterophase polymerization of styrene has been carried out in the presence of surfactants—organosilicon compounds with different solubilities in aqueous and styrene phases and surface activities at the interface. It has been demonstrated that the stability of polymer suspensions prepared with water-insoluble organosilicon compounds is much higher than that in the presence of organosilicon surfactants soluble in organic and aqueous phases. In the former case, suspensions with narrower particle-size distributions are produced. The stability of polymer microspheres prepared at various monomer-to-water volume ratios has been tested. An increase in the monomer concentration above 25 vol % leads to the loss of system stability.

Aspects of the thermal and photostabilisation of high styrene–butadiene copolymer (SBC)

The thermal and photo-oxidative stabilisation of high styrene–butadiene copolymer (SBC) with high styrene content (K-Resin) has been studied using a variety of analytical and spectroscopic methods including yellowness, luminescence and FT-IR spectroscopy coupled with hydroperoxide analysis in order to understand the nature and effectiveness of the processes involved. The next stage of the program was to evaluate the effects of various chemical/solvent treatments on the role of metal ions/residual catalysts and hydroperoxides in the thermal and photostabilisation of SBS as well as combinations of phenolic antioxidants and phosphites/phosphonites. Other additives, such as HALS and a metal deactivator, were also added to the combinations of phenolic and phosphite antioxidants in order to study their behaviour and efficiency. The chemical treatments appeared to stabilise SBS against thermal oxidation to a greater or lesser extent. Phosphoric acid treatment via reflux and zinc dithiocarbamate treatments showed better performances than the rest of the treatments, the latter was particularly effective at inhibiting the discolouration. During photo-oxidation, on the other hand, chemical treatments involving phosphoric acid and pre-thermal effects showed the importance of catalyst effects. The addition of phenolic antioxidants, phosphites/phosphonites, metal deactivator and HALS was found to stabilise the SBS against thermal and photo-oxidation. In thermal oxidation, the combination of Irganox ® 1010/Irgafos ® 168 was found to effectively stabilise the polymer when the finalisation of the polymerisation was with adipic acid. When the same antioxidants were used, but with polymer finalised with BHT, strong yellowing was observed and a higher amount of hydroperoxides and oxidation products. Increasing the amount of antioxidants did not increase the stabilisation efficiency. The stabilisation efficiency of Irganox ® 1010 combined with Alkanox ® P-24 was found to be more effective than when it was combined with Irgafos ® 168. The formulations containing Irgafos ® 168/Irganox ® 1010 and Irgafos ® 168/Irganos ® 1330 were more effective in colour protection and retarding the formation of oxidation products than the combinations of Irgafos ® 168/Irganox ® 3114 and Irgafos ® 168/Lowinox ® 1790. The effect of the addition of HALS, such as Tinuvin ® 770, Tinuvin ® 622 and Chimassorb ® 944, and a metal deactivator, such as Irganox ® MD 1024, to the combination of Irgafos ® 168/Irganox ® 1010 was found to be antagonistic. In photo-oxidation, a combination of Irganox ® 1010/Irgafos ® 168 protected the polymer efficiently, when the polymerisation of the polymer was finalised with adipic acid. When the polymerisation was finalised with BHT, a higher amount of hydroperoxides and oxidation products was found. An increase in the amount of antioxidants did not enhance the stability of the polymer. The addition of Alkanox ® P-24 exhibited an opposite effect to that seen in thermal oxidation, as the stabilisation efficiency was less effective than with Irgafos ® 168. The formulation containing Irgafos ® 168/Irganox ® 1010 was found to be the most efficient compared with the other phenolic antioxidants. The addition of Tinuvin ® 770 to the formulation Irgafos ® 168/Irganox ® 1010 was found to have a synergistic effect. The addition of polymeric HALS or Irganox ® MD 1024, a metal deactivator, had an antagonistic effect on the stabilisation of the polymer. Disruption of the excimer sites in the styrenic phase also correlated with stabilisation effects.

Thermal and scanning electron microscopy/energy-dispersive spectroscopy analysis of styrene-butadiene rubber-butadiene rubber/silicon dioxide and styrene-butadiene rubber-butadiene rubber/carbon black-silicon dioxide composites

Silica as a reinforcement filler for automotive tires is used to reduce the friction between precured treads and roads. This results in lower fuel consumption and reduced emissions of pollutant gases. In this work, the existing physical interactions between the filler and elastomer were analyzed through the extraction of the sol phase of styrene–butadiene rubber (SBR)–butadiene rubber (BR)/SiO2 composites. The extraction of the sol phase from samples filled with carbon black was also studied. The activation energy (Ea) was calculated from differential thermogravimetry curves obtained during pyrolysis analysis. For the SBR–BR blend, Ea was 315 kJ/mol. The values obtained for the composites containing 20 and 30 parts of silica per hundred parts of rubber were 231 and 197 kJ/mol, respectively. These results indicated an increasing filler–filler interaction, instead of filler–polymer interactions, with respect to the more charged composite. A microscopic analysis with energy-dispersive spectroscopy showed silica agglomerates and matched the decreasing Ea values for the SBR–BR/30SiO2 composite well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2273–2279, 2005

Morphology of nylon 6/acrylonitrile–butadiene–styrene blends compatibilized by a methyl methacrylate/maleic anhydride copolymer

AbstractThe morphologies of nylon 6/acrylonitrile–butadiene–styrene blends compatibilized with a methyl methacrylate/maleic anhydride copolymer, with 3–20 wt % maleic anhydride, were examined by transmission electron microscopy. Some staining techniques were employed for identifying the various phases. The binary blends were immiscible and exhibited poor mechanical properties that stemmed from the unfavorable interactions among their molecular segments. This produced an unstable and coarse phase morphology and weak interfaces among the phases in the solid state. The presence of the copolymer in the blends clearly led to a more efficient dispersion of the acrylonitrile–butadiene–styrene phase and consequently optimized Izod impact properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3512–3518, 2003