Effect of organic modifiers on dispersion of organoclay in polymer nanocomposites to improve mechanical properties

Synthesis of Nano Pigments Using Clay Minerals and Organic Dyes and Their Application as Colorants in Polymer Matrix

A new generation of clay-based nano pigments has been introduced, providing the advantage of both inorganic pigments and organic dyes. These nano pigments have been synthesized through a stepwise procedure where, initially, an organic dye is adsorbed onto the surface of the adsorbent, and then dye adsorbed adsorbent is used as pigment for further applications. The objective of the current paper was to examine the interaction of non-biodegradable toxic dyes, Crystal Violet (CV) and Indigo Carmine (IC), with clay minerals (montmorillonite (Mt), vermiculite (Vt), and clay bentonite (Bent)) and their organically modified forms (OMt, OBent, and OVt) and to develop a novel methodology for the synthesis of the value-added products and clay-based nano pigments without creating second generation waste materials. In our observation, the uptake of CV was more intense onto pristine Mt, Bent, and Vt, and the uptake of IC was more onto OMt, OBent, and OVt. CV was found to be in the interlayer region of Mt and Bent, as supported by XRD data. Zeta potential values confirmed the presence of CV on their surface. In contrast, in the case of Vt and organically modified forms, the dye was found on the surface, confirmed by XRD and zeta potential values. In the case of indigo carmine, the dye was found only on the surface of pristine Mt, Bent, Vt, and organo Mt, Bent, Vt. During the interaction of CV and IC with clay and organoclays, intense violet and blue-colored solid residues were obtained (also known as clay-based nano pigments). The nano pigments were used as colorants in a poly (methyl-methacrylate) (PMMA) polymer matrix to form transparent polymer films.

An Investigative Study on the Structural, Thermal and Mechanical Properties of Clay-Based PVC Polymer Composite Films

The present study aims to explore the impact of pristine and surfactant-modified clays (montmorillonite, bentonite and vermiculite) on the thermomechanical properties of a poly (vinyl chloride) (PVC) polymer film. Initially, clay was modified by employing the ion exchange method. The modification of clay minerals was confirmed by the XRD pattern and thermogravimetric analysis. Pristine PVC polymer film and clay (montmorillonite, bentonite and vermiculite)-based PVC polymer composite films were fabricated using solution casting. The ideal dispersion of surfactant-modified organo-clays was observed in the PVC polymer matrix due to the hydrophobic nature of modified clays. The resultant pure polymer film and clay polymer composite film were characterized using XRD and TGA, and their mechanical properties were determined using a tensile strength tester and Durometer. From the XRD pattern, the intercalation of the PVC polymer film was found in the interlayer of organo-clay while exfoliation or partial intercalation and exfoliation were observed for pristine clay mineral-based PVC polymer composite films. Thermal analysis indicated a lowering of the decomposition temperature of the composite film as clay promotes the thermal degradation temperature of PVC. Improvement in the tensile strength and hardness was found to be more frequent in the case of organo-clay-based PVC polymer films, which is only due to the hydrophobic nature of organ clays, resulting in greater compatibility with the polymer matrix.

Physical and mechanical evaluation of dental resin composite after modification with two different types of Montmorillonite nanoclay

OBJECTIVES

Evaluation of degree of conversion (DC), flexural properties, micro-hardness and color change (ΔE₀₀) of dental resin composite after modification with two types of organo-modified Montmorillonite (MMT) nanoclay; an experimentally synthesized polymethyl-methacrylate modified MMT nanoclay (PMMA/MMT), and a commercially available one (Cloisite20A).

METHODS

MMT was synthesized by sol-gel technique, organo-modified with polymethyl-methacrylate and characterized using EDX, XRD and FTIR. PMMA/MMT and Cloisite20A nanoclay were added to flowable resin composite in 0.5, 1 and 1.5 wt% concentrations. Unmodified resin composite was used as control group. DC was assessed by FTIR, flexural properties were tested by three-point bending test using a universal testing machine, micro-hardness was analyzed by Vickers micro-hardness tester and color change (ΔE₀₀) was evaluated using a reflective spectrophotometer. SEM and elemental mapping assessment were performed to evaluate nanoclay distribution in resin composite. Data were analyzed using One-way ANOVA followed by Tukey's post hoc test, in addition to Two-way ANOVA (p ≤ 0.05). Weibull analysis was used to analyze flexural strength results.

RESULTS

Characterization results revealed successful preparation of PMMA/MMT. DC results showed insignificant difference up to 1 wt% of nanoclay concentration. Addition of 0.5 wt% of PMMA/MMT significantly increased flexural properties, while addition of 1.5 wt% of PMMA/MMT significantly decreased flexural properties. Micro-hardness results revealed a significant increase in PMMA/MMT groups in all tested concentrations. ΔE₀₀ results showed that color change was clinically acceptable on adding 0.5 wt% nanoclay.

CONCLUSION

PMMA/MMT in 0.5 wt% is a promising nanofiller for resin composite that significantly enhanced flexural strength and micro-hardness without compromising DC and color.

Effect of POSS-Modified Montmorillonite on Thermal, Mechanical, and Electrical Properties of Unsaturated Polyester Nanocomposites

Montmorillonite (MMT) displays excellent cohesion with an unsaturated polyester (UP) matrix to generate a material which exhibits an extensive range of commercial applications. The organic modification of MMT using polyhedral oligomeric silsesquioxanes (POSS) and the effect of POSS-MMT on the thermal, mechanical, and electrical properties of UP are reported here. Transmission electron microscopy (TEM) images were used to characterize the modification of MMT using POSS. Modified MMT (POSS-MMT) was incorporated, at different wt.% (0.5, 1, 3, 5), into UP via in-situ polymerization. The presence of POSS-MMT enhanced the characteristic properties of UP as a consequence of good dispersion in the polymer matrix. Scanning electron microscopy (SEM) images support effective POSS-MMT dispersion leading to tensile strength enhancement of a UP/POSS-MMT nanocomposite (3 wt.% POSS-MMT) by 54.7% as compared to that for unmodified UP. TGA displays a 35 °C improvement of thermal stability (10% mass loss) at 5% POSS-MMT incorporation, while the electrical conductivity is improved by 10⁸ S/m (3 wt.% POSS-MMT) in comparison to that for unmodified UP. The conventional obstacle of UP associated with shrinkage weight loss during curing seems to be moderated with POSS-MMT incorporation (3%) resulting in a 27.8% reduction in shrinkage weight loss. These fabricated nanocomposites expand the versatility of UP as a high-performance material owing to enhancements of properties.

Preparation and characterization of polyphenylene sulfide/graphene nanoplatelets composite fibers with enhanced oxidation resistance

Composite masterbatches of polyphenylene sulfide (PPS) with functionalized graphene nanoplatelets (GNPs) were prepared by melt blending via a twin-screw extruder. The structure and morphology of composite masterbatches were characterized by scanning electron microscopy and X-ray diffraction analysis. The PPS/functionalized GNPs composite fibers were then manufactured by a self-made spinning equipment via melt spinning. The oxidation resistance and other properties of PPS composite fibers were also examined. The results showed that the pure PPS fibers exhibited smooth surface, whereas the surface of PPS/functionalized GNPs composite fibers was rough. The addition of functionalized GNPs could be acted as heterogeneous nucleating agents to improve the crystallization and increase the degree of crystallinity. The retention rate of breaking strength of PPS/functionalized GNPs composite fibers could maintain up to 85% after the oxidation treatment. The improvement in the oxidation resistance of PPS/functionalized GNPs composite fibers is the results of comprehensive effects characterized by the X-ray photoelectron spectroscopy analyses. The addition of functionalized GNPs could limit the damage of the C–S group and retard the generation of sulfuryl groups (–SO–) during the oxidation treatment. The chemical combination of the elements sulfur (S) and oxygen (O) could also be restricted, thus weakening the oxidation activity.

A Review on Effect of Nanoreinforcement on Mechanical Properties of Polymer Nanocomposites

Polymer nanocomposites represent a new class of materials that offer an alternative to the conventional filled polymers. In this new class of materials, nanosized reinforcement are dispersed in polymer matrix offering tremendous improvement in performance properties of the polymer. The combination of nanoscale reinforcement and polymer matrix possess outstanding properties and functional performance which play an important role in many field of applications. This review addresses the types of nanoscale materials reinforced in polymer matrix such as nanocellulose, carbon nanotubes (CNTs), graphene, nanofibers and nanoclay followed by the discussion on the effect of these nanoscale reinforcement on mechanical properties of polymer nanocomposites. Besides, the potential use of polymer nanocomposite reinforced with those nanoscale reinforcements in various field of applications also discussed.

Nonisothermal crystallization kinetics, morphology, and tensile properties of polyphenylene sulfide/functionalized graphite nanoplatelets composites

Polyphenylene sulfide (PPS)/graphite nanoplates (GNPs) nanocomposites were manufactured by simple melt compounding. The GNPs were first functionalized using synthesized benzimidazolium salt to improve the compatibility with PPS matrix. The functionalized GNPs showed an exfoliated dispersion in PPS matrix, which also could significantly improve the tensile properties of composites. Differential scanning calorimetry was used to investigate the nonisothermal crystallization kinetics of PPS/functionalized GNPs composites. The results showed that the PPS/functionalized GNPs composites always had a higher crystallization peak temperature ( Tc) than pure PPS resin at different cooling rates due to the addition of GNPs. The GNPs could also play the role of heterogeneous nucleating agents to accelerate the crystallization; however, at high content, they could also limit the mobility of PPS macromolecular chains and hinder the crystallization. The Mo equation could be used to analyze the nonisothermal crystallization kinetics, whereas the Ozawa equation was not suitable for the nonisothermal crystallization process. Consistent with a previous analysis, the results also showed that the addition of GNPs could also decrease the crystallization activation energy ( Ec) of PPS resin at low content while increasing the Ec at high content.

Ultrasonic-promoted rapid preparation of PVC/TiO2-BSA nanocomposites: Characterization and photocatalytic degradation of methylene blue

In the present project in order to prevent agglomeration and better dispersion of TiO₂ nanoparticles (NPs) in the poly(vinyl chloride) (PVC) matrix, initially, the surface of TiO₂ NPs was covered by bovine serum albumin protein (BSA) via sonication method. Then, the TiO₂-BSA powders were embedded into the PVC matrix using ultrasonic irradiations. With mechanical and magnetic stirring homogenous mixture was not obtained. So sonication process was very essential and vital. Physical, chemical and structural properties of the samples were investigated with various tools. Morphology studies showed the well distribution of spherical TiO₂ NPs in the PVC matrix. TGA analysis showed that nanocomposites (NCs) have higher thermal stability than the pristine polymer. The photocatalytic activity tests by destroying the methylene blue dye on the pristine TiO₂ NPs, TiO₂-BSA NPs and PVC/TiO₂-BSA NC 6 wt% were examined. The results showed that the photocatalytic activity of TiO₂ NPs was reduced in the presence of BSA and PVC. It can be concluded that the TiO₂-BSA NPs and PVC/TiO₂-BSA NC 6 wt% have UV shielding properties and can protect film from degradation by UV.

Enhanced Oxidation Resistance of Polyphenylene Sulfide Composites Based on Montmorillonite Modified by Benzimidazolium Salt

Organic montmorillonite (MMT) modified by 1,3-dihexadecyl-3H-benzimidazolium bromide (Bz) was used to prepare polyphenylene sulfide (PPS)/MMT composites by melting intercalation. The PPS/MMT composites showed mixed morphology, being comprised of exfoliated and intercalated structures with slight agglomerates. The tensile property of PPS/MMT composites was significantly improved due to the good dispersion of the MMT nanolayers. The test results showed that the tensile strength retention of PPS/MMT composites was higher than that of pure PPS after the oxidation treatment. Moreover, FTIR and XPS analyses were also used to evaluate the oxidation resistance of PPS composites. The FTIR analysis confirmed that adding MMT could better limit the damage of the C⁻S group and retard the generation of sulfuryl groups (⁻SO₂⁻) during the oxidation treatment compared to pure PPS. The XPS analysis also suggested that the addition of MMT could reduce the chemical combination of the elements sulfur (S) and oxygen (O) during oxidation treatment. Furthermore, the MMT nanolayers could also promote the transfer of S from a C⁻S bond into an ⁻SO₂⁻ group.