Polyimide/kaolinite composite films: Synthesis and characterization of mechanical, thermal and waterproof properties

Development of biodegradable film from cactus (Opuntia Ficus Indica) mucilage loaded with acid-leached kaolin as filler

Nowadays, substituting petroleum-based plastics with biodegradable polymers made from polysaccharides loaded with various reinforcing materials has recently gained attention due to the impact of conventional plastics wastes. In this study, polysaccharidic mucilage from Ethiopian cactus (Opuntia Ficus Indica) was derived using microwave-assisted extraction technique to develop biodegradable polymers that were inexpensive, readily available, simple to make, and ecofriendly. The effect of microwave power 300-800 W, solid-liquid (cactus-sodium hydroxide solution) ratio 1:5-1:25, sodium hydroxide concentration 0.1-0.8 mol/L, and extraction time 2-10 min on mucilage extraction were studied and the maximum yield of mucilage was attained at optimized parameters of 506 W, 1:20, 0.606 mol/L, and 9.5 min, respectively. Biodegradable polymers made with mucilage alone have poor mechanical characteristics and are thermally unstable. Thus, to overcome the stated problems, glycerol as a plasticizer and acid-leached kaolin crosslinked with urea as a reinforcing material were used. Moreover, the effect of acid-leached kaolin and glycerol on the physico-chemical properties of the films was studied, and a maximum tensile strength of 6.74 MPa with 18.45 % elongation at break, thermally improved biodegradability of 26 %, were attained at 10 % acid-leached kaolin and 20 % glycerol crosslinking with 2 % urea. But the maximum degradability of 53.5 % was attained at 30 % glycerol content. The control and reinforced biodegradable films were characterized using TGA, FTIR, SEM, and XRD to determine the thermal, functional group, morphology, and crystallinity of the bioplastics, respectively. These biodegradable plastics may be used for packaging application.

Preparation and Property of Bio-Polyimide/Halloysite Nanocomposite Based on 2,5-Furandicarboxylic Acid

Bio-based polyimide (PI)/halloysite nanotube (HNT) nanocomposites based on 2,5-furandicarboxylic acid were prepared by in situ polymerization. The pristine HNTs were modified by tetraethoxysilane (TEOS) and 4,4′-oxybisbenzenamine (ODA). The bio-based PI/HNT nanocomposite film exhibited lower moisture absorption than pure bio-based polyimide, showing that the water resistance of the bio-based polyimide film was improved. The thermal stability and glass transition temperature (Tg) of PI/HNTs nanocomposites were improved with the addition of modified HNTs. Both the tensile strength and Young’s modulus of bio-based PI/HNTs nanocomposite films were enhanced. A 37.7% increase in tensile strength and a 75.1% increase in Young’s modulus of bio-based PI/HNTs nanocomposite films, with 1 wt% of the modified HNTs, were achieved. The result confirmed that 2,5-furandicarboxylic acid could replace the oil-based material effectively, thus reducing pollution and protecting the environment. Finally, a preparation mechanism to prepare bio-based PI/HNTs nanocomposite is proposed.

Overview of Silica-Polymer Nanostructures for Waterborne High-Performance Coatings

Combining organic and inorganic components at a nanoscale is an effective way to obtain high performance coating materials with excellent chemical and physical properties. This review focuses on recent approaches to prepare hybrid nanostructured waterborne coating materials combining the mechanical properties and versatility of silica as the inorganic filler, with the flexural properties and ease of processing of the polymer matrix. We cover silica-polymer coupling agents used to link the organic and inorganic components, the formation of hybrid films from these silica-polymer nanostructures, and their different applications. These hybrid nanostructures can be used to prepare high performance functional coatings with different properties from optical transparency, to resistance to temperature, hydrophobicity, anti-corrosion, resistance to scratch, and antimicrobial activity.

The Influence of Kaolin Clay on the Mechanical Properties and Structure of Thermoplastic Starch Films

The aim of study was to investigate the influence of kaolin on the physical properties and utility of film produced from native starch. The work involved measurements of strength, structure, and thermal properties. The films were prepared by the casting method. Composite films with 0%, 5%, 10%, and 15% kaolin additives were examined. Measurements of mechanical properties were carried out using the uniaxial tensile test, the nanoindentation test, and nanoscratching. Surface properties were examined by atomic force microscopy and contact angle measurements. Structure was determined by the X-ray diffraction method, and thermal properties were determined by differential scanning calorimetry. A significant influence of kaolin on the strength parameters and thermal and barrier properties of composite films was found. An increase in kaolin content reduced the tensile strength, Young’s modulus, and Poisson’s ratio. Structural analysis showed a partial intercalation and the layered arrangement of kaolin particles. Kaolin additives increased the barrier properties of water vapor in composite films of about 9%. Biopolymer modification by nanoclay reduced the thermal stability of composite films by 7% and could accelerate the biodegradation process. Increasing the concentration of kaolin in the biopolymer matrix led to heightened surface roughness (approximately 64%) and wettability of the surfaces of the film composites of 58%.

Effect of polyimide addition on mechanical properties of PMMA-based denture material

The aim of the study was to evaluate the effect of modifying polymethyl methacrylate (PMMA) denture base material with polyimide (PI) on its flexural property and biocompatibility. Low molecular weight (1,500 g/mol) PI was synthesized and small amount of PI (0.4, 0.6, 0.8 and 1 wt%) was dispersed into the PMMA matrix. Three-point bending tests, scanning electron microscopy and thermal cycling were used to measure the mechanical properties, while MTT assay was used to evaluate the biocompatibility of the denture base material. The results showed that 0.6% addition of PI significantly increased flexural strength of PMMA denture base material by 13.5%, compared with the control group (p<0.05). Even after 5,000 hydrothermal cycling the reinforce effect still existed. However, when the PI content further increased, flexural strength of the denture base material decreased due to particle agglomeration. The MTT assay confirmed that the addition of PI did not change the biocompatibility of the PMMA denture base material. The present study suggested that blending polyimide in the proper proportion can be a potential method to strengthen the PMMA-based denture base material.