Influence of nanofillers on the deformation process in layered silicate/polyamide-12 nanocomposites

PA12 Surface Treatment and Its Effect on Compatibility with Nutritional Culture Medium to Maintain Cell Vitality and Proliferation

This research investigates the suitability of printed polyamide 12 (PA12) and its dyed version to support cells in bioengineering applications. For this purpose, human gingival fibroblasts (hGF06) were cultured on PA-12 scaffolds that were 3D-printed by Multi Jet Fusion (MJF). The study examined the direct cultivation of cells on MJF-printed cell culture scaffolds and the effect of leachate of PA-12 printed by MJF on the cultured cells. The article presents research on the surface treatment of PA12 material used in 3D printing and the effect of automatic staining on cell vitality and proliferation in vitro. The study presents a unique device designed exclusively for staining prints made of the biocompatible material PA12 and demonstrates the compatibility of 3D-printed polyamide 12 parts stained in the novel device with a nutrient culture medium and cells. This novel PA12 surface treatment for biomedical purposes does not affect the compatibility with the culture medium, which is essential for cell viability and proliferation. Fluorescence microscopy revealed that mitochondrial fitness and cell survival were not affected by prolonged incubation with clear or dyed PA12 3D-printed parts.

Engineered Clay-Polymer Composite for Biomedical Drug Delivery and Future Challenges: A Survey

Clay materials are widely used in drug delivery systems due to their unique characteristics. Montmorillonite is a major component of bentonite and it has a large surface area, better swelling capacity, and high adsorption capacity. The modification of natural bentonite could improve its sorption ability for new emerging applications. Recent advancements in the polymer-silicate composite have novel biomedical applications in drug delivery, tissue regeneration, wound healing, cancer therapy, enzyme immobilization, diagnostic and therapeutic devices, etc. Perspective view of the montmorillonite- polymer composite as a pharmaceutical carrier in drug delivery systems has been discussed in this review. Different types of modification of montmorillonite for the development of pharmaceutical formulations have also been documented. Many challenges in clay nanocomposite systems of polymer of natural/synthetic origin are yet to be explored in improving antimicrobial properties, mechanical strength, stimuli responsiveness, resistance to hydrolysis, etc. Drug interaction and binding capability, swelling of clay may be carried out for finding possible applications in monitoring delivery systems. Pharmaceutical properties of active drugs in the formulation could also be improved along with dissolution rate, solubility, and adsorption. The clay-incorporated polymeric drug delivery systems may be examined for a possible increase in swelling capacity and residence time after mucosal administration.

MODIFICATION OF MONTMORILLONITE FOR OBTAINING NANOCOMPOSITES BASED ON POLAR POLYMERS

This review covers almost all known categories of compounds used to modify montmorillonite to obtain nanocomposites based on polar polymers. Organic modifiers such as quaternary ammonium ions, quaternary phosphonium ions, amino acids and other organic compounds are commonly used to modify montmorillonite (MMT). The main directions of scientific research in this field are considered, namely the modification of MMT with ammonium surfactants, phosphonium surfactants, amino acids and nonionic surfactants. The review used 67 sources related to peer-reviewed publications, mostly from the last 10-15 years. The largest number of publications devoted to the modification of MMT was published in the period from 2004 to 2016. Nanocomposites based on epoxy resins are especially widely presented in the literature. Epoxy-based materials have been used for many years as convenient matrices for dispersing MMT due to the advantages of properties of the obtained polymer nanocomposites, such as mechanical strength, non-flammability and thermal stability. The methods of surface modification of MMT with organic modifiers considered in the article are a powerful tool for the production of polymer nanocomposite materials based on polar polymers. Amine modification of MMT allowed the formation of highly effective materials, in particular epoxy/MMT materials. These nanocomposites have demonstrated extraordinary material properties compared to virgin polymers and can therefore be used as an alternative to conventional materials such as steel and wood, reducing the cost and weight of products. Nanocomposites based on polar polymers occupy an important place among all polymer nanocomposites as modern materials used in the aerospace, automotive and electrical industries.

Impact of a nanomixture of carbon black and clay on the mechanical properties of a series of irradiated natural rubber/butyl rubber blend

A series of natural rubber/butyl rubber NR/IIR blend loaded with N660 carbon black (CB) and triethoxy vinyl silane treated clay nanoparticles (TCNPs) were prepared using gamma irradiation in the presence of a polyfunctional monomer, trimethylolpropane triacrylate (TMPTA). The effect of incorporating different contents of N660 CB and five parts per hundred of rubber (phr) of treated clay on the mechanical properties of the prepared nanocomposites has been investigated. The addition of TCNP to CB/rubber composites markedly increase their tensile strength due to the increase of the cross-link density. These results indicated that the TCNP may be enclosed or trapped in the occluded structure of CB. The effect of CB and the TCNP content on the tensile strength (σ), elongation at break (ε b, %), and modulus of elasticity (E, MPa) of natural rubber/butyl rubber NR/IIR blend have been investigated. The incorporation of 5 phr of TCNP into 30 phr CB-loaded NR/IIR composites results in the increased tensile strength value by about 60%. Finally, theoretical models were used to interpret the experimental results.

Encapsulation of anion-cation organo-montmorillonite in terpolymer microsphere: structure, morphology, and properties

Exfoliated organo-montmorillonite (O-Mt) layers were successfully encapsulated in a terpolymer microsphere (PAAA) of acrylamide (AM)/acrylic acid (AA)/2-acrylamido-2-methylpropanesulfonic acid (AMPS) via in situ inverse suspension polymerization, with the aid of the organic modification by cetyltrimethylammonium bromide (CTAB) and sodium lauryl sulfonate (SLS). The chemical structure and properties of the Mt were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), which showed that SLS molecules successfully intercalated Mt interlayers and enhanced the thermostability of Mt. The microsphere morphologies of the polymer and its nanocomposites were detected by scanning electron microscopy (SEM). The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the exfoliated O-Mt dispersed in the polymer matrix. The introduction of well-dispersed O-Mt layers significantly enhanced the comprehensive performance of these microspheres, including thermostability and plugging properties. The Tmax of PAAA/1.5 wt.% O-Mt nanocomposite is increased by 46°C compared to the pure terpolymer. The plugging rate of PAAA/2.0 wt.% O-Mt reached up to 85.8%. Therefore, these selected nanocomposite microspheres can provide an effective plugging in the high-permeability layers.

Characterisation of Polyamide (PA)12 Nanocomposites with Montmorillonite (MMT) Filler Clay Used for the Incremental Forming of Sheets

In this paper, the preparation and characterisation of polymer materials suitable for single point incremental forming (SPIF) technology were performed. Three different kinds of mixtures were selected: a mixture of neat polyamide 12 (PA12), a nanocomposite with PA12 matrix and 1% clay (Cloisite 93A), and a nanocomposite with PA12 matrix and 3% clay (Cloisite 93A). Materials were produced using a melt intercalation method followed by compression moulding. According to the needs of SPIF technology, morphological and mechanical properties were investigated in the obtained mixtures. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize morphological properties. It was determined that the most desired obtained exfoliated structure of clay in the polymer matrix was achieved. Static tensile testing and dynamic mechanical analysis as well as the determination of glass transition temperature and crystallinity of all analysed materials were used to obtain mechanical and thermal properties of the mixtures. The results obtained for each mixture were compared with respect to the content of clay. The content of clay (Cloisite 93A) showed a strong influence on the properties of the obtained materials. The presence of clay (Cloisite 93A) affected the increase of tensile strength and Young’s modulus, while its influence on the attained elongation was not unique.

Thermal Degradation Kinetics and Viscoelastic Behavior of Poly(Methyl Methacrylate)/Organomodified Montmorillonite Nanocomposites Prepared via In Situ Bulk Radical Polymerization

Nanocomposites of polymers with nanoclays have recently found great research interest due to their enhanced thermal and mechanical properties. Deep understanding of the kinetics of thermal degradation of such materials is very important, since the degradation mechanism usually changes in the presence of the nano-filler. In this investigation, poly(methyl methacrylate)/organomodified clay nanocomposite materials were prepared by the in situ free radical bulk polymerization technique. The thermal degradation of the products obtained was studied by means of thermogravimetric analysis at several heating rates. Isoconversional kinetic analysis was conducted in order to investigate the effect of degradation conversion on the activation energy. Both, pure poly(methyl methacrylate) (PMMA) and its nanocomposites were found to degrade through a two-step reaction mechanism. Data arising from a differential and an integral method were used to disclose the correlation between activation energies (Eα) and the extent of degradation (α). It was found that Eα value improved for all nanocomposites at α values higher than 0.3. Moreover, the viscoelastic behavior of the obtained nanocomposites was examined by means of dynamic mechanical thermal analysis. All nanocomposites exhibited higher storage modulus in comparison to the virgin PMMA at room temperature, while the increment of clay amount improved their stiffness gradually.

Dielectric and relaxation properties of composites of epoxy resin and hyperbranched-polyester-treated nanosilica

Hyperbranched polyester is effective for enhancing molecular bond strength and improving the mechanical behavior of nanofilled polymers. This study examines the dielectric and polarization relaxation characteristics of epoxy resin composites filled with nanosilica 30 nm in diameter, which is treated by terminal carboxyl hyperbranched polyester. TEM and SEM analysis indicate that the nanosilica surface is grafted with a functional polymer layer ranging in thickness from several to tens of nanometers, and the nanosilica agglomeration in epoxy resin is remarkably inhibited. Measurements of thermally stimulated depolarization current and differential scanning calorimetry show that, deep traps with an energy of 1.09 eV are present in the nanocomposites, and the glass transition temperature (T_g) is increased by 11 °C at most at filler concentrations from 1 to 7 wt%. Moreover, the room-temperature relative permittivity and dielectric loss factor of the composites at 50 Hz are decreased by 0.22 and 1.3‰, respectively. Conductivity at 10 mHz to 1 kHz and dc conductivity are also significantly decreased when the operating temperature is below T_g. The polarization relaxation process of the nanocomposite is dominated by regional carrier migration, interfacial and dipole polarization. The relaxation frequency of dipole polarization at high temperature (>T_g) is transformed to satisfy the Vogel–Tammann–Fulcher law. This research suggests that both the dielectric and the polarization relaxation properties of the epoxy resin composites can be modified by filling hyperbranched-polyester-treated nanosilica, because it enhances the bond strength of the inorganic–organic interface and enlarges the molecular scale of the composites via cross-linking reactions.

Dielectric and relaxation properties of a nanofilled epoxy composite can be effectively modified by nanofiller treatment with a terminal carboxyl hyperbranched polyester.

Dynamically Cross-linked Elastomer Hybrids with Light-Induced Rapid and Efficient Self-Healing Ability and Reprogrammable Shape Memory Behavior

Pristine carbon nanotubes (CNTs) were activated to exhibit Diels-Alder (DA) reactivity in a polymer matrix, which was modified with monomers containing furan groups. The DA-active polymer matrix was transferred into a dynamic reversible cross-linked inorganic-organic network via a Diels-Alder reaction with CNTs, where pristine CNTs were used as dienophile chemicals and furan-modified SBS acted as the macromolecular diene. In this system, the mechanical properties as well as resilience and solvent resistance were greatly improved even with the presence of only 1 wt % CNTs. Meanwhile, the hybrids retained recyclability and exhibited some smart behaviors, including self-healing and reprogrammable shape memory properties. Furthermore, due to the photothermal effect of CNTs, a retro-Diels-Alder (rDA) reaction was activated under laser irradiation, and healing of a crack on the hybrid surface was demonstrated in approximately 10 s with almost complete recovery of the mechanical properties. Such fast and efficient self-healing performance provides a new concept in designing self-healing nanocomposites with tunable structures and mechanical properties. Furthermore, the DA and rDA reactions could be combined to reprogram the shape memory behavior under laser irradiation or thermal treatment, wherein the temporary shape of the sample could be transferred to a permanent shape via the rDA reaction at high temperature.

Fish DNA-modified clays: Towards highly flame retardant polymer nanocomposite with improved interfacial and mechanical performance

Deoxyribonucleic Acid (DNA) has been recently found to be an efficient renewable and environmentally-friendly flame retardant. In this work, for the first time, we have used waste DNA from fishing industry to modify clay structure in order to increase the clay interactions with epoxy resin and take benefit of its additional thermal property effect on thermo-physical properties of epoxy-clay nanocomposites. Intercalation of DNA within the clay layers was accomplished in a one-step approach confirmed by FT-IR, XPS, TGA, and XRD analyses, indicating that d-space of clay layers was expanded from ~1.2 nm for pristine clay to ~1.9 nm for clay modified with DNA (d-clay). Compared to epoxy nanocomposite containing 2.5%wt of Nanomer I.28E organoclay (m-clay), it was found that at 2.5%wt d-clay loading, significant enhancements of ~14%, ~6% and ~26% in tensile strength, tensile modulus, and fracture toughness of epoxy nanocomposite can be achieved, respectively. Effect of DNA as clay modifier on thermal performance of epoxy nanocomposite containing 2.5%wt d-clay was evaluated using TGA and cone calorimetry analysis, revealing significant decreases of ~4000 kJ/m² and ~78 kW/m² in total heat release and peak of heat release rate, respectively, in comparison to that containing 2.5%wt of m-clay.

Processing of Polypropylene-Organic Montmorillonite Nanocomposite by Equal Channel Multiangular Extrusion

By the example of polypropylene-organic montmorillonite composite (PP-OMMT), the abilities of the method of equal channel multiangular extrusion have been studied with respect to the modification of the structure and the properties of polymeric nanocomposites. With using X-ray structure analysis, TEM, DSC, and dilatometry, it has been demonstrated that this kind of processing provides an additional intercalation of the polymer into OMMT tactoids with the succeeding exfoliation and facilitates an increase in the aspect ratio, the degree of platelet orientation, the crystalline lamellar thickness, and a decrease in the dispersion of the crystallite thickness, as well as the formation of biaxial orientation of the OMMT and PP crystals. The observed structure rearrangements determine enhanced microhardness, ductility, and the heat distortion temperature of the PP-OMMT composite.

Aggregation States of Polymers at Hydrophobic and Hydrophilic Solid Interfaces

Aggregation states of polystyrene (PS) and poly(methyl methacrylate) (PMMA) at hydrophobic deuterated-octadecyltrichlorosilane (OTS-d) and hydrophilic SiO_x interfaces are discussed, focusing on the interaction strength between polymer and substrate. Sum-frequency generation spectroscopy revealed that PS exhibited oriented phenyl groups along the normal direction at the interface in a spin-coated film because of the centrifugal force generated during the film solidification process, whereas it did not in a solvent-cast film. This result was common for both hydrophobic and hydrophilic substrates. That is, the aggregation states of PS depended little on which kind of substrate was used. This is because the interaction between PS and the surfaces is weak. In the case of a PMMA film on the hydrophobic OTS-d substrate, the interfacial local conformation was also dependent on the method of film preparation. PMMA at the hydrophilic SiO_x interface, however, exhibited oriented ester methyl groups along the direction normal to the interface, regardless of the film preparation method. This is due to a stronger interaction via hydrogen bonding between carbonyl groups of PMMA and the substrate surface.

Dynamic crosslinked poly(styrene-block-butadiene-block-styrene) via Diels–Alder chemistry: an ideal method to improve solvent resistance and mechanical properties without losing its thermal plastic behavior

Poly(styrene-block-butadiene-block-styrene) (SBS) is a typical example of thermal plastic elastomers (TPE).

Elaboration of poly(lactic acid)/halloysite nanocomposites by means of water assisted extrusion: structure, mechanical properties and fire performance

This study shows the interest of elaborating polylactide/halloysite nanocomposites by means of water assisted extrusion (WAE). Besides, WAE gives access to materials with improved fire properties and prevents molecular degradation.

Hierarchical structures of olefinic blocky copolymer/montmorillonite nanocomposites with collapsed and intercalated clay layers

Hierarchical structures of two types of nanocomposite at different scales were characterized by various techniques.

Effect of nanoclay loading on the thermal and mechanical properties of biodegradable polylactide/poly[(butylene succinate)-co-adipate] blend composites

Polylactide/poly[(butylene succinate)-co-adipate] (PLA/PBSA)-organoclay composites were prepared via melt compounding in a batch mixer. The weight ratio of PLA to PBSA was kept at 70:30, while the weight fraction of the organoclay was varied from 0 to 9%. Small angle X-ray scattering patterns showed slightly better dispersion in PBSA than PLA, and there was a tendency of the silicate layers to delaminate in PBSA at low clay content. Thermal analysis revealed that crystallinity was dependent on the clay content as well its localization within the composite. On the other hand, thermal stability marginally improved for composites with <2 wt % clay content in contrast to the deterioration observed in composites with clay content >2 wt %. Tensile properties showed dependence on clay content and localization. Composite with 2 wt % clay content showed slight improvement in elongation at break. Overall, the optimum property was found for a composite with 2 wt % of the organoclay. This paper therefore has demonstrated the significance of the clay content and localization on the properties of the PLA/PBSA blends.

Enhanced visualization of biodegradable polymeric vascular scaffolds by incorporation of gold, silver and magnetite nanoparticles

Due to improved tissue regeneration and the enabling of post-operative minimally invasive interventions in the same vessel segment, biodegradable polymeric scaffolds represent a competitive approach to permanent metallic stents in vascular applications. Despite these advantages some challenges, such as the improvement of the scaffold mechanics and enhancement of scaffold visibility during the implantation procedure, are persisting. Therefore, the scope of our studies was to investigate the potential of gold, silver and magnetite nanoparticles incorporated in a polymeric blend of poly(L-lactide)/poly(4-hydroxybutyrate) for image enhancement in X-ray, magnetic resonance or near-infrared imaging. Their impact on mechanical properties of such modified scaffold materials was also evaluated.