Investigation on the polyamide 6/organoclay nanocomposites with or without a maleated polyolefin elastomer as a toughener

Current synthesis and characterization techniques for clay-based polymer nano-composites and its biomedical applications: A review

Clays and its composites have received considerable attention recently due to their low cost, wide availability and low environmental impact. The development of various preparation processes and applications of innovative polymer-nanoclay composites has been aided by recent breakthroughs in material technologies. Novel polymer-nanoclay composites with better qualities have been effectively adopted in a variety of fields, including aerospace, car, construction, petroleum, biomedical, and wastewater treatment, owing to innovative production processes. Due to their superior qualities, such as increased density, strength, relatively large surface areas, high elastic modulus, flame retardancy, and thermomechanical/optoelectronic/magnetic capabilities, these composites are acknowledged as potential advanced materials. Hence the present paper reviews the advances in synthesis and preparation of clay-polymer nanocomposites. In addition, this study also focuses on the various techniques used for clay-polymer nanocomposites characterization e.g. scanning electron microscope (SEM), transmission electron microscope (TEM), thermo-gravimetric analysis (TGA) and differential colorimetric analysis (DSC), x-ray diffraction (XRD) analysis, Nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopic (FTIR) characterization. These advanced physico-mechanical and chemical characterization techniques would be effective in understanding the most appropriate application of clay polymer nanocomposites. In addition, the application of clay polymer nanocomposites in biomedical sector is also discussed in brief.

Lead-adsorbing ionogel-based encapsulation for impact-resistant, stable, and lead-safe perovskite modules

Despite the high-efficiency and low-cost prospect for perovskite solar cells, great concerns of lead toxicity and instability remain for this technology. Here, we report an encapsulation strategy for perovskite modules based on lead-adsorbing ionogel, which prevents lead leakage and withstand long-term stability tests. The ionogel layers integrated on both sides of modules enhance impact resistance. The self-healable ionogel can prevent water permeation into the perovskite layer and adsorb lead that might leak. The encapsulated devices pass the damp heat and thermal cycling accelerated stability tests according to International Electrotechnical Commission 61215 standard. The ionogel encapsulation reduces lead leakage to undetectable level after the hail-damaged module is soaked in water for 24 hours. Even being rolled over by a car followed by water soaking for 45 days, the ionogel encapsulation reduces lead leakage by three orders of magnitude. This work provides a strategy to simultaneously address lead leakage and stability for perovskite modules.

Polyamide 6/Poly(vinylidene fluoride) Blend-Based Nanocomposites with Enhanced Rigidity: Selective Localization of Carbon Nanotube and Organoclay

Polyamide 6 (PA6)/poly(vinylidene fluoride) (PVDF) blend-based nanocomposites were successfully prepared using a twin screw extruder. Carbon nanotube (CNT) and organo-montmorillonite (30B) were used individually and simultaneously as reinforcing nanofillers for the immiscible PA6/PVDF blend. Scanning electron micrographs showed that adding 30B reduced the dispersed domain size of PVDF in the blend, and CNT played a vital role in the formation of a quasi-co-continuous PA6-PVDF morphology. Transmission electron microscopy observation revealed that both fillers were mainly located in the PA6 matrix phase. X-ray diffraction patterns showed that the presence of 30B facilitated the formation of γ-form PA6 crystals in the composites. Differential scanning calorimetry results indicated that the crystallization temperature of PA6 increased after adding CNT into the blend. The inclusion of 30B retarded PA6 nucleation (γ-form crystals growth) upon crystallization. The Young's and flexural moduli of the blend increased after adding CNT and/or 30B. 30B exhibited higher enhancing efficiency compared with CNT. The composite with 2 phr 30B exhibited 21% higher Young's modulus than the blend. Measurements of the rheological properties confirmed the development of a pseudo-network structure in the CNT-loaded composites. Double percolation morphology in the PA6/PVDF blend was achieved with the addition of CNT.

Ionic Liquids Incorporating Polyamide 6: Miscibility and Physical Properties

The effects of 1-vinyl-3-butyl imidazole chloride (VBIM) on the structure and properties of Polyamide 6 (PA6) were investigated systematically. It was found that PA6/VBIM blends were homogeneous without phase separation. The glass transition temperature (Tg) of PA6 increased with small VBIM loadings followed by the decreasing in Tg with further increasing the amount of VBIM. The crystallization temperature decreased with the addition of VBIM because of the strong interactions between VBIM and the PA6 matrix, as well as the dilution effect when large amounts of VBIM was introduced to the matrix. According to rheological testing, small amounts of VBIM enhanced the storage modulus and melt viscosity of PA6. Tensile tests also show an increase in strength and modulus at relatively low loadings of VBIM. The strength of PA6 with only 1 wt % VBIM improved by 108% compared to that of neat PA6. Fourier transform infrared (FTIR) investigations revealed that the ions of VBIM preferred to form hydrogen bonds with amide groups in PA6. Therefore, VBIM acts as physical connection point for the neighboring PA6 molecular chains. The specific interactions between VBIM and PA6 account not only for the enhanced melt viscosity of PA6, but also for the improved mechanical properties. Moreover, outstanding antistatic property was also observed. The surface resistivity of the sample with 1 wt % VBIM was 1.50 × 1010 Ω/sq, which means good electric dissipation property.

The effect of organoclay contents on morphological characterization, mechanical and thermal properties of epoxidized natural rubber-50 toughened polyamide 6 nanocomposites

Nanocomposites consisting of polyamide 6 (PA6) matrix with epoxidized natural rubber-50 (ENR-50) and organoclay-modified montmorillonite (OMMT) were prepared by melt blending in a twin-screw extruder followed by injection molding. The influence of varying amounts (0–6 phr) of OMMT loadings on ENR-50 (10 wt.%) toughened PA6 nanocomposites was examined. Morphological characterizations and mechanical and thermal properties of the blend and nanocomposites were investigated. The addition of OMMT resulted in an increase in tensile strength and modulus, while impact strength and elongation at break reduced. Thermal study revealed no significant change in thermal properties with OMMT loadings. Exfoliated structure was observed from X-ray diffraction (XRD) patterns for <4 phr OMMT and was confirmed by transmission electron microscopy (TEM) images.

Surprising high hydrophobicity of polymer networks from hydrophilic components

We report a simple and inexpensive method of fabricating highly hydrophobic novel materials based on interpenetrating networks of polyamide and poly(ethyl cyanoacrylate) hydrophilic components. The process is a single-step solution casting from a common solvent, formic acid, of polyamide and ethyl cyanoacrylate monomers. After casting and subsequent solvent evaporation, the in situ polymerization of ethyl cyanoacrylate monomer forms polyamide-poly(ethyl cyanoacrylate) interpenetrating network films. The interpenetrating networks demonstrate remarkable waterproof properties allowing wettability control by modulating the concentration of the components. In contrast, pure polyamide and poly(ethyl cyanoacrylate) films obtained from formic acid solutions are highly hygroscopic and hydrophilic, respectively. The polymerization of ethyl cyanoacrylate in the presence of polyamide promotes molecular interactions between the components, which reduce the available hydrophilic moieties and render the final material hydrophobic. The wettability, morphology, and thermo-physical properties of the polymeric coatings were characterized. The materials developed in this work take advantage of the properties of both polymers in a single blend and above all, due to their hydrophobic nature and minimal water uptake, can extend the application range of the individual polymers where water repellency is required.

Preparation and Properties of Metallocene-catalyzed PE/Starch Nanocomposites: Role of Nanocompatibilizer

The properties of metallocene catalyzed polyethylene (mPE)/starch blends and nanocomposites containing mPE-g-maleic anhydride (mPE-g-MA) compatibilizer, reinforced with 1 phr commercial organoclay (20A) at various amounts of pristine starch are discussed. The results from X-ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that nanocomposites were achieved in all cases. No observable diffraction peaks in the low angle region were detected. Clay was preferentially located within the mPE and starch interface and the mPE matrix. The crystallization temperatures of nanocomposites increased with the addition of clay acting as a nucleating agent. However, the melting temperatures and the glass transition temperatures remained largely unchanged. Clay incorporation provided a heat barrier that profoundly increased the blend thermal stability. A maximum increase in tensile strength and Young's modulus was obtained, up to 60% and 105%, respectively, using nanoclay reinforced compatibilizer (termed nanocompatibilizer) in comparison with neat compatibilizer for pristine starch filled cases. Slightly lower water absorption capability was observed for nanocompatibilizer reinforced cases through the sheet-like structure of clay compared with neat compatibilizer cases.

Characterization of Nanocomposites by Thermal Analysis

In materials research, the development of polymer nanocomposites (PN) is rapidly emerging as a multidisciplinary research field with results that could broaden the applications of polymers to many different industries. PN are polymer matrices (thermoplastics, thermosets or elastomers) that have been reinforced with small quantities of nano-sized particles, preferably characterized by high aspect ratios, such as layered silicates and carbon nanotubes. Thermal analysis (TA) is a useful tool to investigate a wide variety of properties of polymers and it can be also applied to PN in order to gain further insight into their structure. This review illustrates the versatile applications of TA methods in the emerging field of polymer nanomaterial research, presenting some examples of applications of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA) and thermal mechanical analysis (TMA) for the characterization of nanocomposite materials.

Improved electrical conductivity of polyamide 12/graphene nanocomposites with maleated polyethylene-octene rubber prepared by melt compounding

Electrically conductive polyamide 12 (PA12)/graphene binary nanocomposites with a low percolation threshold of 0.3 vol % were prepared by melt compounding. A rapid increase in electrical conductivity from 2.8 × 10(-14) S/m of PA12 to 6.7 × 10(-2) S/m was achieved with ~1.38 vol % graphene. It is shown that graphene sheets were homogeneously dispersed in PA12 matrix. Furthermore, polyethylene-octene rubber grafted with maleic anhydride (POE-g-MA) was used to further enhance the electrical conductivity of PA12/graphene nanocomposites. Three compounding sequences were adopted to tailor the microstructure and properties of the ternary nanocomposites. Both highest electrical conductivity and storage modulus were obtained when most graphene sheets were located in PA12 matrix rather than in POE-g-MA phase.

Nanocompósitos de poliamida 6 e argila organofílica: estudo da cristalinidade e propriedades mecânicas

Nanocompósitos de poliamida 6 e argila organofílica claytone 40 foram preparados por intercalação por fusão, utilizando misturador de câmara interna equipado com rotores do tipo Roller. A adição de teores crescentes de claytone 40 na matriz de PA6 foi avaliada quanto ao grau de dispersão, cristalinidade, propriedades térmicas e as propriedades mecânicas. As composições obtidas foram caracterizadas por difração de raios X (DRX), calorimetria diferencial de varredura (DSC), microscopia eletrônica de varredura (MEV) e propriedades mecânicas. Os difratogramas e as micrografias sugeriram a ocorrência de formação de estruturas parcialmente esfoliadas e/ ou intercaladas, fato que foi associado com o aumento nos valores de tensão e o módulo elástico. A comparação entre os resultados de DSC e DRX das misturas revelaram alterações estruturais na cristalinidade em relação à PA6 correlacionando a cristalinidade à variação nas propriedades mecânicas.

Avaliação do comportamento térmico por DSC na região da pele e do núcleo de amostras injetadas de nanocompósitos de poliamida 6/argila organofílica

Nanocompósitos de poliamida 6/argila organofílica foram preparados pelo método de intercalação por fusão. A argila foi tratada com o sal quaternário de amônio (Cetremide) visando-se à obtenção da argila organofílica (OMMT). Esta foi caracterizada por fluorescência de raio X (FRX), Espectroscopia no Infravermelho (FTIR) e Difração de Raio X (DRX). Os resultados dessas análises evidenciaram incorporação do sal entre as camadas da argila, tornando-a organofílica. Os nanocompósitos foram obtidos em extrusora de rosca dupla corrotacional, com 3% em peso de argila, e estes foram posteriormente injetados. A caracterização dos nanocompósitos por DRX mostrou uma estrutura esfoliada e/ou parcialmente esfoliada. As análises por Calorimetria Exploratória Diferencial (DSC) foram realizadas nas regiões da pele (superfície) e do núcleo (centro) dos corpos de prova e, mostraram as fases cristalinas α e γ na pele e apenas a fase α no núcleo e que o grau de cristalinidade na pele foi menor do que no núcleo.