High‐resolution solid‐state NMR and SEM study of the interaction behavior of poly(ethylene‐co‐vinyl acetate)/poly(vinyl acetate) blends

Binary blends formed by two types of ethylene‐co‐vinyl acetate (EVA), which have different vinyl acetate contents, and poly(vinyl acetate) (PVAc) were prepared in a Haake Rheocord 9000 plastograph. A series of samples were obtained varying the PVAc amount up to 50%. The studies were carried out employing solid‐state nuclear magnetic resonance spectroscopy (NMR) and scanning electronic microscopy (SEM). The xenon‐129 (¹²⁹Xe) and carbon‐13 (¹³C) NMR response together with the microscopy results showed that the systems are heterogeneous. Therefore, EVA with a higher vinyl acetate content presented some interaction between the polymer blend components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 116–124, 2002     

Reinforcement of ethylene‐acrylic elastomer with a dispersion of grafted PA6 droplets

Cured elastomers are commonly dispersed in thermoplastics, but the reverse morphology has received little attention. The present work examines dispersions of 0.5–2 μm PA6 droplets in ethylene‐acrylic elastomer (AEM), created by melt blending. After cooling, the blends are compounded with amine curative and crosslinked. Uncrosslinked blends exhibit high bound rubber levels compared to N990 carbon black filled AEM, but similar viscosity at equal filler volume fraction. Crosslinking the blends produces strong, heat resistant vulcanizates with minimal Payne effect and good compression set resistance. These properties result from extensive AEM‐PA6 grafting, absence of filler‐filler contacts, and beneficial modification of the oxidation profile under diffusion limited conditions. The data show rubber‐filler grafting strongly influences filler reinforcing ability, but does not directly influence the Payne effect. Relative to unfilled AEM, silica and carbon black fillers accelerate oxidative degradation in proportion to their reinforcing ability, whereas PA6 has a stabilizing effect. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43995.     

Influence of filler–rubber interactions on the viscoelastic properties of carbon‐black‐filled rubber compounds

The specific role of filler–rubber interactions in dynamic properties was investigated. Natural rubber compounds, filled with N330 carbon black, were used, and the filler surface was modified through a gas treatment in the solid phase. The effects of this filler surface treatment on the dynamic properties were systematically studied at equal filler dispersion levels. The dynamic properties were assessed for both uncured and vulcanized compounds, and a number of advanced investigative techniques were used to characterize not only the modification of the carbon particle surface by an oxidative treatment but also the structure of the filled rubber compounds. Particular attention was paid to techniques that gave access to the segmental mobility to explain the benefit observed with modified carbon black. A molecular interpretation, based on NMR measurements, was considered that took into account physicochemical parameters. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 577–588, 2004     

Solution and solid‐state NMR investigation of poly(methyl methacrylate)/poly(vinyl pyrrolidone) blends

The development of polymer blends has become very important for the polymer industry because these blends have shown to be a successful and versatile alternative way to obtain a new polymer. In this study, binary blends formed by poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) were prepared by solution casting and evaluated by solution and solid‐state NMR. Variations in the microstructure of PMMA were analyzed by ¹³C solution NMR. Solid‐state NMR promotes responses on physical interaction, homogeneity, and compatibility to use these blends to understand the behavior of the ternary blends. The NMR results led‐us to acquire information on the polymer blend microstructure and molecular dynamic behavior. From the NMR solution, it was possible to evaluate the microstructure of both polymer blend components; they were atactic. From the solid state, good compatibility between both polymer components was characterized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 372–377, 2004     

Natural abundance 15n solid‐state nmr study of nylon‐6 in blends

Natural abundance solid‐state nuclear magnetic resonance spectroscopy (NMR) of nitrogen‐15 (¹⁵N) was applied to investigate the films of nylon‐6 and their blends with poly(propylene oxide) (PPO). The NMR ¹⁵N results allowed us to identify the crystalline forms present in these blends and also confirmed the previous NMR results obtained by ¹³C‐NMR study. From all NMR data the antiplasticization phenomena and plasticization effects caused by PPO content, in the blends were characterized. The polyoxide action is a function of its proportion. However, because the samples were prepared by solution casting, the residual solvent action cannot be ignored. The ¹⁵N chemical shift changes were influenced by both PPO and residual solvent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3872–3875, 2003     

Influence of 1,2‐unit contents on retraction behaviors of SBR vulcanizates

Styrene‐butadiene rubber (SBR) has four different repeat units of styrene, cis‐1,4‐, trans‐1,4‐, and 1,2‐uints. Influence of the 1,2‐unit content on the retraction behaviors of SBR vulcanizates reinforced with silica or carbon black was studied. The retraction behaviors were compared in terms of the filler systems and the microstructures of SBR. The silica‐filled vulcanizates containing a coupling agent showed nearly the same retraction behaviors as the carbon black‐filled ones, but the silica‐filled vulcanizates without a coupling agent were recovered slower than the carbon black‐filled ones. The vulcanizates with lower 1,2‐unit content started to recover at lower temperature than that with higher 1,2‐unit content. The recovery rate increased with increase of the 1,2‐unit content of SBR. The experimental results were explained with the polymer‐filler interactions, filler dispersion, glass transition temperature, and modulus. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4707–4711, 2006     

Dynamic properties of star‐shaped,solution‐polymerized styrene–butadiene rubber and its cocoagulated rubber‐filled with silica/carbon black

The dynamic properties, including the dynamic mechanical properties, flex fatigue properties, dynamic compression properties, and rolling loss properties, of star‐shaped solution‐polymerized styrene–butadiene rubber (SSBR) and organically modified nanosilica powder/star‐shaped styrene–butadiene rubber cocoagulated rubber (N‐SSBR), both filled with silica/carbon black (CB), were studied. N‐SSBR was characterized by ¹H‐NMR, gel permeation chromatography, energy dispersive spectrometry, and transmission electron microscopy. The results show that the silica particles were homogeneously dispersed in the N‐SSBR matrix. In addition, the N‐SSBR/SiO₂/CB–rubber compounds' high bound rubber contents implied good filler–polymer interactions. Compared with SSBR filled with silica/CB, the N‐SSBR filled with these fillers exhibited better flex fatigue resistance and a lower Payne effect, internal friction loss, compression permanent set, compression heat buildup, and power loss. The nanocomposites with excellent flex fatigue resistance showed several characteristics of branched, thick, rough, homogeneously distributed cross‐sectional cracks, tortuous flex crack paths, few stress concentration points, and obscure interfaces with the matrix. Accordingly, N‐SSBR would be an ideal matrix for applications in the tread of green tires. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40348.     

Multinuclear solid‐state NMR investigation of the moisture distribution in PEEK‐PBI and PEKK‐PBI blends

Blends of polyaryletherketones (PAEK), such as polyetheretherketones (PEEK) and polyetherketoneketones (PEKK), with polybenzimidazole (PBI) are of commercial interest due to their improved high‐temperature stability and wear properties. The changes of PBI and its PEEK‐ and PEKK‐blends (50 : 50 wt %) after immersing them in liquid H₂O and D₂O, and exposing them to D₂O steam at elevated temperatures and pressures are investigated by multinuclear solid‐state NMR and IR spectroscopy. Macroscopic morphological and chemical changes on the molecular scale, which take place upon high‐temperature steam‐treatment and the extent and reversibility of moisture uptake have been investigated. Interactions and reactions of water, steam, and aqueous solutions of LiCl and ZnBr₂ with the functional groups of the polymer components have been studied using D₂O in combination with IR, ¹H wideline, ²H, ⁷Li, and ⁷⁹Br MAS, as well as ¹³C and ¹⁵N CP/MAS NMR spectroscopy. Different locations and types of water and protons in the blends have been described and PBI has been proven to be mainly responsible for water and salt uptake into the blends. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41421.     

Reinforcement of polyolefins‐based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (PP) and ethylene propylene copolymer (EPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated‐Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO₂ systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high‐shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization‐process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties. POLYM. ENG. SCI., 55:2328–2338, 2015. © 2015 Society of Plastics Engineers     

Effects of carbon fillers on the rheology of highly filled liquid‐crystal polymer based resins

Adding conductive carbon fillers to insulating resins increases the composite electrical and thermal conductivity. Often, enough of a single type of carbon filler is added to achieve the desired conductivity while still allowing the material to be molded into a bipolar plate for a fuel cell. In this study, various amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX liquid‐crystal polymer. The rheological properties of the resulting single‐filler composites were measured. In addition, the rheological properties of composites containing combinations of different carbon fillers were studied via a factorial design. In all cases, the viscosity increased with increasing filler volume fraction and followed a shear‐thinning power‐law model. The factorial design results indicated that each of the single fillers and all the filler combinations caused a statistically significant increase in the composite viscosity when compared at a shear rate of 500 s^?1 or at a stress of 10⁵ Pa. For composites containing synthetic graphite particles and/or carbon fiber, the viscosity variation with the volume fraction of carbon followed a modified Maron–Pierce equation. When compared at a constant volume fraction of carbon, composites containing carbon black showed viscosity enhancement above and beyond that shown by the other composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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 (E_a) was calculated from differential thermogravimetry curves obtained during pyrolysis analysis. For the SBR–BR blend, E_a 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 E_a values for the SBR–BR/30SiO₂ composite well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2273–2279, 2005     

Effect of polymer-filler interactions on PTC behaviors of LDPE/EPDM blends filled with carbon blacks

The dependence of electrical resistivities on the temperature of different polymer systems (including rubbers and plastic/rubber blends) loaded with carbon blacks (including oxidized and normal carbon blacks) were studied. We found that polymer-carbon black interactions could greatly influence the electrical resistivity and temperature relations of the polymer composites. The polymer blends filled with oxidized carbon black, or the elastomer which has polar functional groups filled with carbon black, have a very weak negative temperature coefficient (NTC) effect, which is due to the strong polymer-filler interactions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1885–1890, 1997     

Enhancing the air impermeability of a biobased poly(di‐isoamyl itaconate‐co‐isoprene) elastomer via the cocoagulation of latex and natural layered silicates

The gas‐barrier properties of elastomer are of particular importance, especially for airtight applications. Poly(di‐isoamyl itaconate‐co‐isoprene) (PDII) is a newly invented and respectable biobased elastomer, but the barrier properties of PDII and its composites with carbon black and silica are not satisfying at all. Because there are abundant ester groups in PDII macromolecules and these groups can contribute to the homogeneous dispersion of layer silicates, we applied layered silicates, including montmorillonite (MMT) and rectorite (REC), into the PDII matrix to improve the air impermeability. MMT/PDII and REC/PDII composites were prepared by a cocoagulation method, and the air impermeability of the PDII elastomer was highly improved. The smallest gas permeability index reached 1.7 × 10^?17 m² Pa^?1 s^?1 at an REC content of 80 phr; this implied a reduction of 85.5%. A comparison of the two types of silicate/PDII composites showed that the MMT/PDII composites had better properties at low filler contents, whereas the REC/PDII composites had better mechanical and gas‐barrier properties at high filler contents. Other structures and properties of the composites were investigated by X‐ray diffraction, transmission electron microscopy, and dynamic mechanical rheology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40682.     

13C‐NMR study on cure‐accelerated phenol‐formaldehyde resins with carbonates

Both liquid‐ and solid‐state carbon‐13–nuclear magnetic resonance (¹³C‐NMR) spectroscopies were used to investigate the cure acceleration effects of three carbonates (propylene carbonate, sodium carbonate, and potassium carbonate) on liquid and cured phenol‐formaldehyde (PF) resins. The liquid‐phase ¹³C‐NMR spectra showed that the cure acceleration mechanism in the propylene carbonate‐added PF resin seemed to be involved in increasing reactivity of the phenol rings, whereas the addition of both sodium carbonate and potassium carbonate into PF resin apparently resulted in the presence of ortho–ortho methylene linkages. Proton spin‐lattice rotating frame relaxation time (T_1ρH) measured by solid‐state ¹³C cross polarization/magic‐angle spinning NMR spectroscopy was smaller for the cure‐accelerated PF resins than that of the control PF resin. The result indicated that the cure‐accelerated PF resins are less rigid than the control PF resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1284–1293, 2000     

Properties of poly(ethylene terephthalate)–poly(ethylene naphthalene 2,6‐dicarboxylate) blends with montmorillonite clay

The production and properties of blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) with three modified clays are reported. Octadecylammonium chloride and maleic anhydride (MAH) are used to modify the surface of the montmorillonite–Na⁺ clay particles (clay–Na⁺) to produce clay–C18 and clay–MAH, respectively, before they are mixed with the PET/PEN system. The transesterification degree, hydrophobicity and the effect of the clays on the mechanical, rheological and thermal properties are analysed. The PET–PEN/clay–C18 system does not show any improvements in the mechanical properties, which is attributed to poor exfoliation. On the other hand, in the PET–PEN/clay–MAH blends, the modified clay restricts crystallization of the matrix, as evidenced in the low value of the crystallization enthalpy. The process‐induced PET–PEN transesterification reaction is affected by the clay particles. Clay–C18 induces the largest proportion of naphthalate–ethylene–terephthalate (NET) blocks, as opposed to clay–Na⁺ which renders the lowest proportion. The clay readily incorporates in the bulk polymer, but receding contact‐angle measurements reveal a small influence of the particles on the surface properties of the sample. The clay–Na⁺ blend shows a predominant solid‐like behaviour, as evidenced by the magnitude of the storage modulus in the low‐frequency range, which reflects a high entanglement density and a substantial degree of polymer–particle interactions. Copyright © 2005 Society of Chemical Industry     

13C‐NMR, 1H‐NMR,and FT‐Raman study of radiation‐induced modifications in radiation dosimetry polymer gels

¹H‐ and ¹³C‐NMR spectroscopy and FT‐Raman spectroscopy are used to investigate the properties of a polymer gel dosimeter post‐irradiation. The polymer gel (PAG) is composed of acrylamide, N,N′‐methylene‐bisacrylamide, gelatin, and water. The formation of a polyacrylamide network within the gelatin matrix follows a dose dependence nonlinearly correlated to the disappearance of the double bonds from the dissolved monomers within the absorbed dose range of 0–50 Gy. The signal from the gelatin remains constant with irradiation. We show that the NMR spin–spin relaxation times (T₂) of PAGs irradiated to up to 50 Gy measured in a NMR spectrometer and a clinical magnetic resonance imaging scanner can be modeled using the spectroscopic intensity of the growing polymer network. More specifically, we show that the nonlinear T₂ dependence against dose can be understood in terms of the fraction of protons in three different proton pools. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1572–1581, 2001     

Exploring the simultaneous effect of nano‐silica reinforcement and electron‐beam irradiation on a model LDPE/EVA‐based TPE system

BACKGROUND: The technical properties of polyolefinic thermoplastic elastomer (TPE) systems can be modified significantly using fillers like nano‐silica. Controlled irradiation can potentially be an effective way of tailoring the technical properties of such nano‐silica‐filled TPE systems. RESULTS: The effect of controlled electron‐beam irradiation on the properties of a pristine silica nanoparticle‐filled model low‐density polyethylene/ethylene–(vinyl acetate) (LDPE/EVA) TPE system is explored in this paper. The morphology of such a filled system was investigated using scanning electron microscopy (SEM) and field‐emission SEM. The dispersion of silica particles was analysed using transmission electron microscopy which clearly indicates that at low loading a fine dispersion of silica occurs in the polymer matrix. Swelling studies and Fourier transform infrared analyses indicate the occurrence of a favourable EVA–silica interaction. On the whole, it is observed that electron‐beam irradiation induces a high degree of reinforcement in all the silica‐filled samples through interfacial crosslinking as well as controlled crosslinking in the two polymer phases. In a few samples the processing characteristics are remarkably preserved following concurrent nano‐silica reinforcement and irradiation, while the technical properties of TPE systems, including set, solvent swelling and mechanical properties, are improved. However, the improvement in properties is a strong function of sequence of addition of filler in the LDPE/EVA blends. CONCLUSION: The green technique studied can be potentially extended for the improvement of the technical properties of conventional TPE systems. Copyright © 2009 Society of Chemical Industry     

Gas‐phase‐assisted surface polymerization of methyl methacrylate with Fe(0)/TsCl initiator system

To obtain a high polymer coated Fe(0) surface, gas‐phase‐assisted surface polymerization (GASP) of methyl methacrylate (MMA) was investigated using a zero‐valent iron (Fe(0))/p‐toluene sulfonylchloride (TsCl) initiator system, resulting in successful high polymer production on the solid surface. GASP was found to be initiated by radical species that might have been generated via redox reactions with Fe(0), Fe(II), Fe(III), and TsCl. From ¹H‐NMR analysis, the p‐toluene sulfonyl group was found at one end of the polymer chain. The molecular weight of obtained PMMA drastically decreased with increase in the composition ratio of Fe(0) in the initiator system, and increased with increase in polymer yield. From the results, it was assumed that the physically controlled polymerization of MMA proceeded by immobilized active species at gas–solid interfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1879–1886, 2007     

Polymer precursor‐derived HfC–SiC ultrahigh‐temperature ceramic nanocomposites

Due to poor mechanical properties and antioxidation properties, etc of single phase ultrahigh‐temperature ceramics (UHTCs), the second phase such as SiC was usually introduced for improving those properties. Herein, a novel stratagem for synthesis of binary HfC–SiC ceramics has been presented. A Hf–O–Hf polymer as a HfO₂ precursor has been synthesized for preparing soluble HfC–SiC precursors with high solid content and low viscosity solutions without additional organic solvents. The structure of PHO was characterized by FTIR and ¹H‐NMR, the crystalline behavior and morphologies of polymer‐derived ceramics were identified by XRD, SEM‐EDS, and TEM. It was shown that PHO firstly transformed into HfO₂, and then reacted with in situ carbon derived from DVB and PCS thus producing cubic HfC through carbothermal reduction. In addition, the obtained HfC–SiC nanopowders exhibited spherical morphology with a diameter less than 100 nm, while the Hf, Si, and C are homogeneously distributed.     

BIMS/filler interactions. II. Effects of filler concentration and BIMS structure

Brominated isobutylene para‐methylstyrene (BIMS) elastomer is a terpolymer of isobutylene, para‐methylstyrene (PMS), and para‐bromomethylstyrene (BrPMS). Viscoelastic measurements have been used to characterize the blends of this BIMS elastomer with different concentrations of a carbon black (CB) filler, N234. Data in the low temperature/high frequency region suggest that N234 at a concentration less than or equal to 15 vol % in BIMS appears not to affect the T_g of BIMS although a slight increase in relaxation time in the transition zone is observed. Also, the effects of BrPMS and PMS contents in BIMS on BIMS/N234 CB interactions have been qualitatively investigated by using the bound rubber measurements. To assess BIMS/CB interactions with reference to diene rubber/CB interactions, mixing of BIMS with various amounts of a polybutadiene rubber in the presence of CB has been performed. Atomic force microscopy and image processing have been employed to quantify filler phase distributions in these blends for a practical ranking of polymer/CB interactions. Preferential partition of CB in the BIMS or BR phase depends on the BrPMS content in BIMS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 659–667, 2006