Polyamide–silica nanocomposites: mechanical, morphological and thermomechanical investigations (original) (raw)
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Dispersion of surface-modified, aggregated, fumed silica in polymer nanocomposites
Journal of Applied Physics, 2020
Surface modification of model silica to enhance compatibility in nanocomposites has been widely studied. In addition to model spherical silica, several authors have investigated the impact of surface conditions on compatibility in commercial aggregated carbon black and silica. In this paper, dispersion is investigated for a series of nanocomposites produced from commercially modified fumed silica mixed with styrene butadiene rubber, polystyrene, and polydimethylsiloxane. Surface modification includes variation in surface hydroxyl content, siloxane, and silane treatment. Qualitatively, hydroxyl groups on the silica surface are considered incompatible with non-polar polymers, while methyl groups are compatible with oleophilic polymers. X-ray scattering was used to analyze the filler aggregate structure before and after dispersion, and the second virial coefficient was used to quantify nanodispersion. The content of surface moieties was determined from Fourier-transform infrared spectroscopy. It is observed that modified silica can display mean field or specific interactions as reflected by the presence of a correlation peak in x-ray scattering. For systems with specific interactions, a critical ordering concentration is observed related to the free energy change for structuring. A van der Waals model was used to model the second virial coefficient as a function of accumulated strain, yielding the excluded volume and an energetic term. The excluded volume could be predicted from the structural information, and the bound polymer layer was directly related to the surface methyl content, whereas the energetic term was found to synergistically depend on both the methyl and hydroxyl surface content.
Journal of Applied Polymer Science, 2012
Organic-inorganic nanocomposites consisting of co-poly(vinyl chloride-vinyl acetate-vinyl alcohol) and silica were prepared via sol-gel process. Two types of hybrids were prepared, one in which interactions between hydroxyl group present in the copolymer chain and silanol groups of silica network were developed. In the second set, extensive chemical bonding between the phases was achieved through the reaction of hydroxyl groups on the copolymer chains with 3-isocyanatopropyltriethoxysilane (ICTS). Hydrolysis and condensation of tetraethoxysilane and pendant ethoxy groups on the chain yielded inorganic network structure. Mechanical and thermal behaviors of the hybrid films were studied. Increase in Young's modulus, tensile strength, and toughness was observed up to 2.5 wt % silica content relative to the neat copolymer. The system in which ICTS was employed as binding agent, the tensile strength and toughness of hybrid films increased significantly as compared to the pure copolymer. Thermogravimetric analysis showed that these nanocomposite materials were stable up to 250 C. The glass transition temperature increases up to 2.5 wt % addition of silica in both the systems. Field emission scanning electron microscope results revealed uniform distribution of silica in the copolymer matrix. V C 2012 Wiley Periodicals, Inc. J Appl Polym
European Polymer Journal, 2007
Polymer-silica nanocomposites based on poly(2-hydroxyethyl acrylate) (PHEA) have been prepared by the simultaneous polymerization of the organic and the silica phases in a sol-gel process with the silica precursor tetraethyl orthosilicate (TEOS). The structure of this system is investigated using atomic force microscopy (AFM) in the tapping mode and in nanoindentation experiments. The structure of the PHEA/silica hybrids strongly depends on the ratio of both components in the system. For silica weight fractions lower than 0.15, the system consists of aggregated silica particles dispersed in the organic matrix; above that concentration of silica the structure is co-continuous with that of the organic matrix, similarly to two interpenetrated networks.
Polymer and nanocomposites: Symposium, 21-22 February 2018, Abstract book
2018
Poly(imide siloxane) monomer blocks which are produced from the combination of polysiloxane and polyimide has processable property [1]. Flexible block copolymers were synthesized by using Benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BTDA),4,4'-Oxydianiline (ODA) and Polydimethylsiloxane, bis(3-aminopropyl) (APPS). BTDA and APPS composed soft block of the copolymer. The length of polysiloxane soft blocks increased with increasing the length of polyimide hard block. These materials have a potential usage as substrates in several industrial areas.
Multiscale Effects of Interfacial Polymer Confinement in Silica Nanocomposites
Macromolecules, 2015
Dispersing hydrophilic nanofillers in highly hydrophobic polymer matrices is widely used to tune the mechanical properties of composite material systems. The ability to control the dispersion of fillers is closely related to the mechanical tunability of such composites. In this work, we investigate the physical−chemical underpinnings of how simple end-group modification to one end of a styrene−butadiene chain modifies the dispersion of silica fillers in a polymer matrix. Using surface-sensitive spectroscopies, we directly show that polymer molecular orientation at the silica surface is strongly constrained for silanol functionalized polymers compared to nonfunctionalized polymers because of covalent interaction of silanol with silica. Silanol functionalization leads to reduced filler aggregation in composites. The results from this study demonstrate how minimal chemical modifications of polymer end groups are effective in modifying microstructural properties of composites by inducing molecular ordering of polymers at the surface of fillers.
Morphology and thermo-mechanical properties of compatibilized polyimide-silica nanocomposites
Journal of Applied Polymer Science, 2005
Polyimide-silica nanocomposites have been prepared from an aromatic polyamic acid derived from pyromellitic dianhydride and oxydianiline and a silica network using the sol-gel reaction. Compatibilization of the two components was achieved by modifying the silica network with imide linkages. Morphology, thermal, and mechanical properties of these composite materials were studied as a function of silica content and compared with the one in which reinforcement of the polyimide was achieved using a pure silica network. There was considerable reduction in the silica particle size with more homogeneous distribution in the matrix when imide spacer groups were introduced in the silica network. The tan δ spectra obtained from dynamic thermal mechanical analysis shows a large increase in the glass transition temperature with increasing silica content for the compatibilized system in contrast to the un-compatibilized one. Mechanical properties of the polyimide composites improved due to better interaction between the organic and inorganic phases. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2521–2531, 2005
Journal of Polymer Science Part B-polymer Physics, 2003
Poly(vinyl alcohol) (PVA) composite films filled with nanometric, monodisperse, and spherical silica particles were prepared by the mixing of an aqueous PVA solution and SiO2 colloidal suspension and the evaporation of the solvent. Adjusting the solution pH to 5 and 9 controlled the PVA-SiO2 interaction. Adsorption isotherms showed a higher PVA/surface affinity at a lower pH. This interaction influenced the composite structure and the particle distribution within the polymer matrix, which was investigated by small-angle neutron scattering, electron microscopy, and swelling measurements. Most of the mechanical properties could be related to the composite structure, that is, the distribution of clusters within the polymer matrix. The progressive creation of a cluster network within the polymeric matrix as the silica volume fraction increased reduced the extensibility or swelling capacity of the composite. The effect was more acute at a higher pH, at which the surface interaction with PVA was weaker and promoted the interconnection between clusters. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3127–3138, 2003
Structure & strength of silica-PDMS nanocomposites
Polymer, 2010
Silica nanoparticles having specific surface area (SSA) 50e300 m 2 g À1 were admixed into vinylterminated dimethylsiloxy monomer with a dual asymmetric centrifuge (planetary mixer) and cured to form PDMS-based nanocomposites containing up to 12 vol% SiO 2 . Thin sections of cured nanocomposites obtained by a cryostate-microtome were analyzed by TEM while small and ultra small angle X-ray scattering (U/SAXS) was used to determine nanocomposite structure: filler primary particle, aggregate (chemically or sinter-bonded particles) and agglomerate (physically-bonded particles) size as a function of mixing duration and filler concentration. More aggregated silicas with higher SSA exhibited denser crosslinking than less aggregated ones regardless of crosslinker content as determined by swelling nanocomposites in toluene at equal filler content. The nanocomposite strength was determined by tensile tests (Young's modulus and elongation at break). Consistent with "bound rubber" theory, the Young's modulus of the nanocomposites increased non-linearly with increasing filler volume fraction.
Poly (methyl acrylate) plus mesoporous silica nanohybrids: Mechanical and thermophysical properties
2007
A mesoporous silica MCM-48 is used as a reinforcement agent for poly(methyl acrylate) (PMA). Methyl acrylate is introduced into the mesoporous silica that has an interconnected porous structure, allowing monomer diffusion into the pores before the polymerization reaction. In order to improve the silica plus polymer adhesion and to decrease the silica agglomeration, the silanol groups of the silica are functionalized with methyl groups without decreasing significantly the pore size. The silica is characterized by nitrogen adsorption, scanning electronic microscopy (SEM) and infrared (IR) spectroscopy. The nanohybrids so obtained are analyzed by tensile testing, thermogravimetry (TGA), differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA). The highest improvement of mechanical and thermophysical properties is achieved for nanohybrids containing 5 wt. % mesoporous silica. At 10 % silica, agglomeration of the filler takes place and the dispersed phase is less effective in reinforcing the polymer matrix.
Nanocomposites of Silica Reinforced Polypropylene: Correlation Between Morphology and Properties
Polypropylene/fumed hydrophilic silica nanocomposites were prepared via melt mixing method using a singlescrew extruder. Comparative study with and without compatibilizing copolymer agent (maleic anhydride grafted polypropylene: PP-g-AM) was conducted. The obtained results were interpreted in terms of silica nanoparticle–silica nanoparticle and silica nanoparticle-polymer interactions. These results have shown that the addition of nanofillers improves the properties of the nanocomposites. From transmission electron microscopy, it was found that agglomerations of silica particles into the PP matrix increased in average size with increasing silica contents, except in presence of the copolymer. Storage modulus values of the nanocomposites measured by dynamic mechanical thermal analysis were sensitive to the microstructure of the nanocomposites. Higher silica contents resulted in higher storage modulus, revealing that the material became stiffer. By adding the compatibilizer, a further increase of storage modulus was observed due to the finer dispersion of the filler in the matrix and the increased interfacial adhesion. Crystallization rates were found to increase with the increase of silica nanoparticles as well as PP-gMA content. In addition, silica nanoparticles and the compatibilizing agent present centers of germination and nucleation of crystallites. Thus, the use of the coupling agent resulted in a further enhancement of mechanical properties of the nanocomposites due to the reduction of silica agglomeration.