Thermal Stability Of Composite Films Research Articles

Highly responsive reduced graphene oxide embedded PVDF flexible film-based room temperature operable humidity sensor

The current study reports a flexible, free-standing nanocomposite thick film based on reduced graphene oxide incorporated PVDF for room temperature humidity sensing application. A facile, cost-effective solvent casting method fabricates PVDF-RGO (PR) films with varied nanofiller loadings (0.1, 0.2, and 0.3 vol%). The structural properties, including the variation in the α, β, and γ polymorphic phases, are studied in detail from XRD, FTIR, and Raman spectra, confirming the β phase’s dominance in composite films at lower RGO content. Optical studies confirm the nanofiller-induced changes in absorbance, bandgap, and Urbach energy. For films with lower RGO concentration (PR1 and PR2), a significant increase in bandgap is observed compared to pure PVDF, and the trend reverses at a higher RGO content (PR3), whereas Urbach energy has depicted an increasing trend with the filler content. Surface morphology and roughness of the film are analyzed using FESEM and AFM images, respectively. Maximum surface roughness is observed for PR3, which is one of the reasons for the exceptional humidity response of the latter sample. The compositional analysis via XPS verified the interaction between RGO and PVDF, leading to the phase transformation. The thermogram of the films manifested the increased thermal stability of composite film due to the inclusion of RGO as a nano additive. The humidity sensing measurements show that the composite films have exhibited excellent sensitivity for the relative humidity range of 11–97% compared to pure PVDF. PR3 has shown maximum sensitivity of 98.99% with a rapid dynamic response and recovery time of 21 s and 26 s, respectively. Hence, the prepared composite has revealed an outstanding humidity response in terms of sensitivity, response/ recovery time, long-term stability, and negligible hysteresis.

Relaxor-antiferroelectric hybrids for pyroelectric energy conversion from low-grade heat using flexible PVDF-TrFE-CTFE-NaNbO3 nanocomposite films

Nowadays, researchers focus more on developing smart materials that respond to different stimuli for harvesting energy output. In this paper, the pyroelectric energy harvesting capabilities of smart terpolymer poly(vinylidene-fluoride-trifluoroethylene-chlorotrifluoroethylene) [PVDF-TrFE-CTFE]-based nanocomposites have been investigated. Sodium niobate (NaNbO3) from the perovskite family is selected as the filler. The Sol-gel method is used to synthesise NaNbO3 nanoparticles, and solvent-cast films for different weight fractions (0–20%) of fillers have been fabricated. Structural, morphological, and dielectric properties of the polymer nanocomposite samples were done at room temperature. The ferroelectric properties of the terpolymer is improved with filler addition. The thermal stability of composite films was confirmed using differential scanning calorimetric (DSC) studies. The thermodynamic Olsen cycle was applied to nanocomposites for calculating the harvested energy output. Maximum energy density is obtained for higher filler loading (20 wt % sodium niobate). The operating temperatures were selected at 303 K and 333 K with an applied field of 130 kV/cm. The results show that including NaNbO3 in the relaxor terpolymer matrix considerably enhances the energy harvesting density of the nanocomposites, indicating that they are promising materials for designing thermally stable energy harvesting systems.

Chemical combination of nano‐silica and alkaline lignin for property enhancement of polylactic acid‐based composite films

AbstractAs a key byproduct from alkaline pulping industry, alkaline lignin (AL) exhibits tremendous potentials for the development of high‐value‐added biomaterials, ascribed to its renewability and unique polymeric structure. In this study, the alkaline lignin was first oxidized and then modified with aminated nano‐silica. After further hydrophobic modification with a silane coupling agent, a novel lignin‐based filler was finally prepared and applied for property enhancement of PLA‐based composite films. As revealed from SEM results that, a uniformed state of filler distribution could be achieved if the filler content is no more than 1%. Under this condition, the thermal stability of composite film could be effectively improved, as well as the enhancement of tensile strength (50.7 MPa) and Young's modulus (2847 MPa). Notably, the composite films also exhibit selective resistance against UV lights rather than visible lights, especially at higher filler content.

Fabrication and characterization of waste fish scale-derived gelatin/sodium alginate/carvacrol loaded ZIF-8 nanoparticles composite films with sustained antibacterial activity for active food packaging

An environmental-friendly composite films containing waste fish scale-derived gelatin (FSG), sodium alginate (SA) and carvacrol loaded ZIF-8 (CV@ZIF-8) nanoparticles were designed and fabricated to develop active food packaging materials capable of sustained antibacterial activity. The microstructure and physicochemical properties of the FSG/SA/CV@ZIF-8 composite films were investigated. The incorporation of CV@ZIF-8 into FSG/SA matrix significantly enhanced the UV-light blocking and the elongation at break, improved water resistance and reduced water vapor permeability, and improved the thermal stability of composite film. The FSG/SA/CV@ZIF-8 film not only exhibited strong antioxidant activity with DPPH radical scavenging rate of 92.35 %, but also showed the satisfactory and long-acting antibacterial ability against E. coli and S. aureus due to slow release of CV from composite film. Strawberry preservation experiment revealed that FSG/SA/CV@ZIF-8 film decelerated the texture deterioration and retarded the growth of spoilage microorganism, resulting in the prolonged shelf-life of 8 days under ambient condition, indicating its promising application prospect in food preservation packaging.

Utilization of peel of white pomelo for the development of pectin based biodegradable composite films blended with casein and egg albumen

Biodegradable composite films were developed using casting method from white pomelo peel pectin, casein and egg albumin at different proportions. The pectin was incorporated to modify the properties of films and the effect of pectin incorporation on various properties of films was investigated. In comparison to other edible films, the composite films prepared from white pomelo peel pectin, casein protein and egg albumin protein at a ratio of 50:50:0 (F4) and 50:25:25 (F7) possessed highest tensile strength and lowest water vapour permeability. The X-Ray diffraction (XRD) analysis of composite films indicated that the major portion of the film was amorphous. Fourier Transform Infrared Spectroscopy (FTIR) analysis of composite films indicated the increase in the intermolecular interactions of polymers resulting in increase in compactness of film matrix. The curves obtained by Differential Scanning Calorimetry (DSC) indicated that addition of pectin into casein and egg albumin increased the melting temperature and the peak temperature, indicating increased thermal stability of composite films.

Production, Properties and Applications of Cellulose/Waste Leather Buff Composite (WLB) for Environmental Sustainability and Recyclability

This work aimed to utilize waste leather buff (WLB) as a packing filler in cellulose to produce degradable composite. Imidazolium-based ionic liquids was used to dissolve the cellulose and WLB in a coagulation bath and the resultant homogenous solution formed was casted in a clean glass plate to form cellulose/WLB composite film, washed in deionized water and dried in a desiccator. The composite film was characterised by FT-IR, SEM and thermogravimetric analysis. The modulus of elasticity and tensile strength properties of the composite film were lower than those obtained from cellulose matrix alone. There is also high thermal stability of composite film due to the cross-linkage between the collagen protein in the leather fibres of the WLB. The fractography of the composite film indicated that a good interfacial bond exists between the films, hence the composite film has been used as a wrapper/packaging application for environmental sustainability and material recyclability. Keywords: Fibre; Fibre/matrix bond; Recycling; Thermal analysis, Climate Change

Understanding the Mechanical Reinforcement of Metal-Organic Framework-Polymer Composites: The Effect of Aspect Ratio.

The aspect ratio (AR) of filler particles is one of the most critical determinants for the mechanical properties of particle-reinforced polymer composites. However, it has been challenging to solely study the effect of particle AR due to the difficulties of controlling AR without altering the physical and chemical properties of the particle. Herein, we synthesized PCN-222, a zirconium-based porphyrinic metal-organic framework (MOF) with preferential longitudinal growth as a series of particles with ARs increasing from 3.4 to 54. The synthetic MOF conditions allowed for the chemical properties of the particles to remain constant over the series. The particles were employed as reinforcers for poly(methyl methacrylate) (PMMA). MOF-polymer composite films were fabricated using doctor-blading techniques, which facilitated particle dispersion and alignment in the PMMA matrix, as revealed by optical microscopy and wide-angle X-ray diffraction. Mechanical measurements showed that both elastic and dynamic moduli increased with particle AR and particle concentrations but started to decrease as particle loading increased beyond 0.5 wt % (1.12 vol %). The data obtained at low particle loadings were fitted well with the Halpin-Tsai model. In contrast, the percolation model and the Cox model were unable to adequately fit the data, indicating the mechanical reinforcement in our system mainly originated from efficient load transfer between particles and the matrix in the particle orienting direction. Finally, we showed that the thermal stability of composite films increased with the addition of MOF particles because of the high thermal degradation temperature and restricted polymer chain mobility.

Preparation of treelike and rodlike carboxymethylated nanocellulose and their effect on carboxymethyl cellulose films

AbstractIn this work, carboxymethyl cellulose (CMC) with low substitution degree, followed by different posttreatments, was applied to prepare treelike CMC nanofibrils (CMCNFs) and rodlike CMC nanocrystals (CMCNCs), and their performance in CMC composite film was evaluated simultaneously. From transmission electron microscopy results, it was found that the treelike CMCNCFs exhibited a lager aspect ratio compared to the rodlike CMCNCs. As for reinforcing CMC film, 4 wt% was the best adding amount, at this time, the tensile strength of CMC/CMCNFs and CMC/CMCNCs composite films was increased by 72.1% and 47.3%, respectively. Moreover, adding these nanofillers to CMC also could enhance the thermal stability of composite films slightly, while the transmittance of composite films was reduced at the same time. In addition, CMC/CMCNFs film was designed as a packaging box to determine its performance. Therefore, this study could reveal the differences of properties for composites with different types of nanocellulose and provide a foundation for further application of nanocellulose.

Effects of colloidal silica on the properties of POSS-containing fluorinated poly(styrene–acrylate)/SiO2 composite materials

Polyhedral oligomeric silsesquioxane (POSS)-containing fluorinated poly(styrene–acrylate)/SiO2 (POSS-FPSA/SiO2) composite materials were prepared by preemulsification and direct blending method. The SiO2 particles were induced aggregated onto the surface of POSS, and sol–gel processes were simultaneously carried out with addition of co-solvent to form raspberry-like structure. 29Si NMR and XRD results confirmed that POSS were successfully grafted to polymer and were evenly dispersed uniformly in polymer matrix. The average diameter of composite latexes increased from 63 to 81 nm with increasing addition of SiO2 content. AFM and WCA images confirmed that sol–gel processes were promoted by increasing addition of SiO2 content, which improved the roughness and hydrophobicity of composite films. XPS spectra displayed that two kinds of Si–O bonds existed on the surface of composite films. One was related to the Si–O groups of SiO2, and the other was attributed to the Si–O–Si groups obtained from the sol–gel processes. The peak area of the former decreased from 56.86% to 38.78%, while the latter increased from 43.14% to 62.22%. TGA curves demonstrated that the composite film exhibited better thermal stability when the SiO2 content was 10.0%. In addition, serious phase separation would decrease the thermal stability of composite films.

Preparation and characterization of corn starch/PVA/glycerol composite films incorporated with ε-polylysine as a novel antimicrobial packaging material

Abstract Corn starch/polyvinyl alcohol (PVA)/glycerol composite films incorporated with ε-polylysine were prepared, and their properties were investigated. The Fourier-transform infrared (FTIR) spectroscopy indicated that the interactions happened between the amino group of ε-polylysine and hydroxyl group starch/PVA composite films. X-ray diffraction (XRD) analysis showed that the addition of ε-polylysine decreased the intensity of all crystal peaks. Thermogravimetric (TGA) analysis suggested that ε-polylysine improved the thermal stability of composite films. Scanning electron microscopic (SEM) analysis showed that the upper surface of composite films incorporated with ε-polylysine presented more compact and flat surface. The antimicrobial activity of the composite film progressively increased with the increasing of ε-polylysine concentration (P < 0.05). The tensile strength, elongation at break and water absorption significantly increased, whereas water solubility decreased with the increasing of ε-polylysine concentration (P < 0.05). Therefore, the corn starch/PVA/glycerol composite films incorporated with ε-polylysine had good mechanical, physical and antimicrobial properties and could have potential application as a novel antimicrobial packaging material.

Spathodea campanulata bud fluid reinforced mechanical, hydrophilicity and degradation studies of poly (vinyl alcohol) matrix

The present study aims to scrutinize the influence of Spathodea campanulata (SC) bud fluid on various properties of PVA. The different volumes of SC bud fluid doped PVA films were prepared by the solvent evaporation technique and analyzed by various characterization techniques. The molecular interactions of PVA with SC bud fluid was confirmed by FTIR studies. Tensile properties such as tensile strength and Young’s modulus increased from 48 ± 4 to 59 ± 10 and 2069 ± 110 to 2537 ± 404 MPa respectively compared to PVA. The DSC measurements of prepared films depicted an increased glass transition temperature than PVA. The thermal stability of composite films was not affected compared to the pristine PVA. The XRD results of all the films represented a semi-crystalline material with a characteristic peak at 2θ = 20°. The morphology studies revealed the homogeneous surface due to the good dispersion of SC bud fluid. The water contact angle findings shown the composite films were hydrophilic. Composite film solubility in water increased after the incorporation of SC bud fluid. The water vapor transmission rate of composite films were assessed. The Soil Burial tests indicated the degradation rate of PVA increased in composite films due to increased hydrophilicity.

Thermal and barrier properties of poly(butylene adipate-coterephthalate) incorporated with zeolite doped potassium ion for packaging film

In this research, the works were focused on development of film packaging of poly(butylene adipate-co-terephthalate) (PBAT) incorporated with modified zeolite using (3-aminopropyl) trimethoxysilane. PBAT composites were compounded by melt mixing using twin screw extrusion then molded into film by cast film extrusion process. Effects of zeolite 13X at 1 wt% and zeolite doped potassium ion (K+) on thermal properties, permeability of gases (oxygen, carbon dioxide and water vapor) and also absorption of ethylene gas of PBAT composites films have been studied. Typically, zeolite would act as a nucleating agent. Therefore, adding zeolite would increase the degree of crystallinity of PBAT. Comparing zeolite with and without cation exchange, the degree of crystallinity in film tended to increase for the one doped with potassium ion. Either zeolite with or without potassium exchange had no impact on thermal stability of composite films. Gas permeation of PBAT/zeolite film possessed lower permeation of oxygen and carbon dioxide whereas the water vapor transmission showed relatively higher rate than the neat PBAT. After cation exchange with zeolite, the permeation of oxygen and carbon dioxide has reduced 21.04% and 21.90% respectively but the effect of K+ exchange had no effect on water vapor transmission compared with PBAT. Film of PBAT and zeolite doped with cation could absorb ethylene gas more than the one with zeolite.

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%.

Potential of using multiscale corn husk fiber as reinforcing filler in cornstarch-based biocomposites

In this study, biodegradable composite films were prepared by using thermoplastic cornstarch matrix and corn husk fiber as a reinforcing filler. The composite films were manufactured via a casting technique using different concentrations of husk fiber (0–8%), and fructose as a plasticizer at a fixed amount of 25% for starch weight. The Physical, thermal, morphological, and tensile characteristics of composite films were investigated. The findings indicated that the incorporation of husk fiber, in general, enhanced the performance of the composite films. There was a noticeable reduction in the density and moisture content of the films, and soil burial assessment showed less resistance to biodegradation. The morphological images presented a consistent structure and excellent compatibility between matrix and reinforcement, which reflected on the improved tensile strength and young modulus as well as the crystallinity index. The thermal stability of composite films has also been enhanced, as evidenced by the increased onset decomposition temperature of the reinforced films compared to neat film. Fourier transform infrared analysis revealed increasing in intermolecular hydrogen bonding following fiber loading. The composite materials prepared using corn husk residues as reinforcement responded to community demand for agricultural and polymeric waste disposal and added more value to waste management.

Fast and simple construction of composite films with renewable Eucommia ulmoides gum and Poly(ε-caprolactone)

Eucommia ulmoides gum (EUG) and Poly(ε-caprolactone) (PCL), a degradable, promising and “green” feedstock, can be used to fabricate composite films by a rapid and simple solution casting method, which have characteristics of degradability, hydrophobicity, strength, and toughness. Herein, EUG was extracted with petroleum ether from seed coats of Eucommia ulmoides and characterized with Fourier transform infrared (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). The FT-IR and NMR revealed that the construction of the EUG and PCL of composite films are a physical blending process. Besides, the addition of PCL effectively enhances the thermal stability of composite films. The concentration of PCL is 0.84 wt% in composite film (P0.84 wt%), which exhibits an excellent elongation at break and energy density at break of 514.3% and 106.4 MJ/m3, respectively. The maximum tensile strength of the resultant film is 1.8 times higher than that of the control film. The hydrophobicity and water vapor barrier property of P0.84 wt% film is increased by 26.6% and 84.0%, respectively, than that of the control film. It is believed this work provided a rapid and simple strategy to fabricate degradable, strong, and tough film.

Alginate-based nanocomposite films reinforced with halloysite nanotubes functionalized by alkali treatment and zinc oxide nanoparticles

Functionalized halloysite nanotubes were prepared by surface activation of halloysite (Hal) with sodium hydroxide and deposition of zinc oxide nanoparticles (ZnONP). The surface charge of Hal was changed from 0.18 ± 0.6 mV to −35.2 ± 2.8 mV after alkali treatment. The functionalized Hal (AT-Hal/ZnONP) was incorporated into alginate biopolymer as a reinforcing filler with different concentration of AT-Hal/ZnONP (1, 3, 5, and 7 wt% of alginate). Alginate films with AT-Hal/ZnONP exhibited a significant increase in the mechanical, water vapor barrier, and UV light barrier properties. The thermal stability of composite films has not changed after AT-Hal/ZnONP incorporation. The AT-Hal/ZnONP incorporated alginate films demonstrated strong antibacterial activity against food-borne pathogenic bacteria, Escherichia coli and Listeria monocytogenes. The nanocomposite film with 7 wt% of AT-Hal/ZnONP exhibited complete sterilization of E. coli and L. monocytogenes after 3 and 9 h of treatment, respectively.

Preparation of gelatin-based films modified with nanocrystalline cellulose

Gelatin is a natural biological macromolecule derived from the collagen in the connective tissue of the skin, bone and other tissues. It has been widely used in medicine, food and industrial production and other fields for easy molding, excellent compatibility and biodegradability. However, physical and chemical disadvantages impede its further application, seriously. Therefore, modification of the gelatin films becomes more and more important. In this study, the gelatin/nanocrystalline cellulose (NCC) composite films were prepared by casting method with 4% glycerol as plasticizer. The effect of NCC on the properties of the composite films was investigated by the characterization of its morphology and mechanical, thermal, and optical properties and water adsorption. The results showed that mechanical, thermal stability and water absorption properties of the gelatin/NCC composite film were obviously improved. The composite films showed the highest tensile strength (13.56 ± 0.25 MPa) when the mass concentration of NCC was 0.6%. Adding NCC to gelatin benefited the thermal stability of composite films. The gelatin/NCC composite film of 0.4% NCC had the highest melting transition temperature (138.9 °C). The composite films exhibited the lower water absorption (271.1%) when mass concentration of NCC was 1.0%. Thus, these results indicated that NCC could affect the properties of gelatin-based composite films, and showed it has potential for application in food packing.

Characterization of whey protein-carboxymethylated chitosan composite films with and without transglutaminase treatment

Edible composite packaging has the advantage of complementary functional properties over its each bio-components. However, reports on whey protein concentrates (WPC)-carboxymethylated chitosan (CMC) composite films have not yet been released. To investigate the preparation of WPC-CMC composite films and its functional properties, four types of WPC-CMC composite films were prepared with and without Transglutaminase (TGase) treatment by mixing WPC aqueous solutions (10%, w/v) with CMC aqueous solutions (3%, w/v) at WPC to CMC volume ratios of (100:0), (75:25), (50:50), and (25:75). SDS-PAGE confirmed that TGase catalyzed crosslinking of whey protein. Results revealed that CMC incorporation conferred a smooth and even surface microstructure on the films and markedly improved the transparency, water barrier properties, mechanical properties and solubility of the composite film. Furthermore, TGase resulted in an improvement in the water vapor barrier properties and mechanical properties of WPC-CMC (75:25 and 50:50, v/v) composite films, and there was no impairment of thermal stability of composite films. Therefore, TGase successfully facilitated the formation of WPC-CMC composite films with some improved functional properties. This offers potential applications as an alternative approach to the preparation of edible packaging films.

Effect of SiO<SUB align="right">2 nanoparticles on the thermal properties of dielectric composite films

In order to investigate the influence of SiO2 nanoparticles on the thermal properties of polyimide (PI) composite films, the experimental data of nanocomposite films with changing heat is determined by thermal-gravimetric analysis (TGA) and differential thermal analysis (DTA). The results show that the thermal stability of composite films increases from 500°C to 100°C; the requirement of decomposition heat increases from 30 nw to 60 nw, which is twice as large as the requirement of pure PI; the initial decomposition temperature of composite films is remarkable higher than pure PI and when the weight loss is 5 wt% the temperature increases from 200°C to 520°C, which is 2.5 times. This suggests that adding inorganic nanoparticles can effectively improve the thermal properties of composite film. With increasing content, nanoparticles can form thermal network in the matrix, which is one of important reasons to improve the thermal properties of composite films.

The utilization of carbon nitride to reinforce the mechanical and thermal properties of UV-curable waterborne polyurethane acrylate coatings

Abstract The waterborne polyurethane-acrylate (WPUA and Wsi-PUA) oligomers were prepared by anionic self-emulsifying method, using isophorone diisocyanate (IPDI), polyethylene glycol (PEG), dimethylol propionic acid (DMPA), vinyl hydroxyl silicone oil (VHSO) and hydroxyethyl methyl acrylate (HEMA) as raw materials. Then, a series of UV-curable waterborne Wsi-PUA–C 3 N 4 composites containing different content of g-C 3 N 4 were obtained with oligomer and photoinitiator Darocur 1173. FTIR, XRD, TEM, SEM, and TGA were employed to investigate the structure, morphology and thermal property of the Wsi-PUA–C 3 N 4 composite films. The effect of g-C 3 N 4 content on the performance was also investigated. The mechanical performance, water resistance and gel content of UV-PUA films were measured. It was found that with g-C 3 N 4 particle was introduced into Wsi-PUA oligomer, the hardness, tensile strength, gel content, water resistance and thermal stability of composite films were significantly augmented. Moreover, when the content of g-C 3 N 4 was 1.0 wt.%, the UV-curable film had the best mechanical property. The obtained composite is promising for a number of applications, e.g., for protecting the surfaces of metal and wood.