Mechanical Properties Of Films Research Articles

Tailoring silk-based covering material with matched mechanical properties for vascular tissue engineering

Vascular covered stents play a significant therapeutic role in cardiovascular diseases. However, the poor compliance and biological inertness of commercial materials cause post-implantation complications. Silk fibroin (SF), as a biomaterial, possesses satisfactory hemocompatibility and tissue compatibility. In this study, we developed a silk film for use in covered stents by employing a layer-by-layer self-assembly strategy with regenerated SF on silk braiding fabric. We investigated the effects on the mechanical properties of the silk films in detail, which were closely correlated with fabric parameters and layer-by-layer self-assembly. The results showed that there was a significant relationship between these factors and both the compliance and mechanical strength. The 1 × 2/90°/100/SF6 film exhibited excellent mechanical properties. Notably, compliance reached 2.6%/100 mmHg, matching that of the human saphenous vein. Thus, this strategy shows promise in developing a novel covered stent, with biocompatible and comprehensive mechanical properties, and significant potential for clinical applications.

Tannic acid-loaded halloysite clay grafted with silver nanoparticles improved the mechanical, antimicrobial, and degradation properties of linear low-density polyethylene films

Synthetic polymers used for food packaging contribute to plastic pollution due to poor degradability. While they prevent the entry of microorganisms, they may not protect against spoilage microorganisms in the packed food. Nanofillers have been used to improve such properties, but end-of-life degradation remains an issue, making plastic a persistent pollutant. Here, we tested a nanocomposite (Nc) of tannic acid-loaded halloysite nanotubes grafted with silver nanoparticles as a reinforcement to enhance the mechanical, antimicrobial, and degradation properties of Linear low-density polyethylene (LLDPE) films. LLDPE films incorporated with Nc significantly improved tensile strength (TS), elongation at break (EB), and oxygen permeability rate. Nc incorporated (at 5%-and 10%) LLDPE films exhibited a 1.89-2.85 log10 reduction in multi-drug resistant Staphylococcus aureus 1158c in chicken fillets. Both film types demonstrated silver migration below the European Food Safety Authority-mandated acceptable limit. Nc/LLDPE films disintegrated faster when exposed to incandescent light for 6 h, evidenced by significant reduction of weight, TS, and EB. Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy suggested oxidative degradation and breakdown of the polymer. Conclusively, Nc improved the functional properties and degradation rate of LLDPE films when exposed to light, showing potential for enhancing the sustainability of synthetic polymers.

Comparison of the mechanical properties of Mo films by different nanoindentation techniques

Nanocrystalline Mo films were prepared by magnetron sputtering. Indentation size effect (ISE) on hardness (H) was both studied by constant strain rate method (CSR) and continuous stiffness method (CSM). Inverse ISE appears and H from CSR is higher than that from CSM. Significant dislocation motion barrier effect of increased grain boundary (GB) induces strengthening. Each step of CSM promotes the generation of heterogeneous GBs and enhances GB-emitting dislocations ability, leading to softening.

Substituting corn starch with wolf's fruit and butterfly lily starches in thermopressed films: Physicochemical, mechanical, and biodegradation properties

The industrial use of corn starch competes with food supplies, encouraging the investigation of native starches as an alternative for its partial replacement. This study aimed to analyze the effects of replacing corn starch (CS) with wolf's fruit (WFS) and butterfly lily (BLS) starches on the physicochemical, mechanical, and biodegradation properties of starch-based films. Plasticized (with glycerin and citric acid) and unplasticized films were prepared with a microwave (10 s) and by thermopressing (1.5 t/120 °C/2 min) and were analyzed for amylose, scanning electron microscopy, X-ray diffraction, and paste properties. Furthermore, the biodegradability of films was tested in two soils over 42 days. Our results show that BLS is not a suitable raw material to replace corn starch. WFS with 27.5 % apparent amylose content and granule size of 12.5 μm produced films with thickness, permeability, tensile strength, and elongation of ~110 μm, ~4.8 g (m.s.Pa)−1, ~2.5 MPa, and ~2.9 %, respectively, similar to CS. The biodegradability of WFS film showed greater resistance (≤61.4 %), increasing with the addition of plasticizers (89–93 % for WFS302) or partial replacement of CS (73–91 % for CSWFS303). These findings indicate that WFS can partially or fully replace CS in thermopressed films.

A straight-forward fabrication of yuba films with controllable mechanical properties by oil-in-water emulsion model system rather than soymilk

The traditional process of producing yuba films from soybeans strictly limits the development of its industrial production due to the numerous processes and intricate procedures involved. In this study, a straight-forward and effective strategy was proposed to substitute soymilk with an emulsion made from soybean protein isolate and soybean oil for the formation of yuba films. It was found that the mechanical properties of yuba films formed through this method were controlled by the concentrations of proteins and oils. As the protein concentrations increased, a higher ratio of adsorbed proteins adhered to the surface of oil droplets, which in turn facilitated the recombination of proteins and the formation of larger aggregates during heat incubation. The rheological properties and interfacial adsorption behavior suggested that larger protein aggregates exhibited a greater diffusion rate and were more prone to unfolding and re-crosslinking at the interface through heat induction, resulting in the formation of stronger protein networks. Confocal laser scanning microscope images revealed a notable increase in the density of oil distribution within the yuba films as the oil concentrations in the pre-emulsion rose. Combined with the dense protein network formed at high protein concentrations, the elongation of yuba films was significantly increased.

Improving Water Resistance and Mechanical Properties of Crosslinked Waterborne Polyurethane Using Glycidyl Carbamate

Waterborne polyurethane (WPU) often suffers from poor water resistance and mechanical properties due to hydrophilic emulsifiers. To address these issues, this study introduces glycidyl carbamate (GC) as a crosslinker to improve WPU performance. Three types of GC were synthesized using aliphatic, cycloaliphatic, and aromatic isocyanates, respectively. The crosslinked network was established through a reaction between the epoxide group of GC and the carboxylic acid and amine groups of WPU. Among these, the WPU film utilizing aromatic isocyanate-based GC exhibited the highest crosslink density, modulus, hardness, and water resistance, due to the rigidity of the aromatic molecular structure. However, the film displayed excessive brittleness, resulting in reduced tensile strength, along with yellowing typically associated with aromatic compounds. The WPU crosslinked with cycloaliphatic GC demonstrated the next best mechanical properties and water resistance, with a 2.7-fold increase in tensile strength, a 1.5-fold increase in hardness, and a 66% reduction in the water swelling ratio compared to neat WPU. This study presents a novel and effective strategy to enhance the water resistance and mechanical properties of WPU films, making them suitable for advanced coating applications.

The physicochemical, mechanical, and antifungal properties of sodium alginate film containing Japanese rice vinegar and peppermint (Mentha piperita) oil as bio-composite packaging

The physicochemical, mechanical, and antifungal properties of sodium alginate film containing Japanese rice vinegar and peppermint (Mentha piperita) oil as bio-composite packaging

Viscoelastic Properties of Electrospray‐Deposited Polymer Shells via Quartz Crystal Microbalance With Dissipation (QCM‐D)

AbstractMultilayer polymer films are extensively used in multiphase separation. Electrospray deposition (ESD) is an important technique for fabricating such films with tunable morphology. Viscoelastic properties of polystyrene (PS) nanoshell coatings produced by ESD on gold and spin‐coated PS surfaces are evaluated using Quartz Crystal Microbalance with Dissipation (QCM‐D). The thickness of PS films on gold increases with flow rate from ∼200 nm at 0.5 to ∼400 nm at 1.5 mL h−1, accompanied by an order‐of‐magnitude increase in dissipation due to larger particle sizes from shorter droplet flight times. This effect is absent on spin–coated PS films, suggesting the onset of the self‐limiting effect of charges. Although the shear moduli for ESD films calculated from Voigt models is only 0.08%–0.20% of the bulk PS modulus, the stiffness ratio of spray‐coated PS to a single shell is (5.00–13.3) × 103 m−1, due to shell–shell and shell–substrate interactions. These are novel results related to the interparticle friction obtained using QCM‐D for the first time. This work demonstrates that mechanical properties of particulate viscoelastic films with potential applications in high surface area sensors, such as size‐selective membranes for protein or electrolyte adsorption, can be evalauted by QCM‐D with nanograms of material.

Encapsulation of Bacillus subtilis in Electrospun Poly(3-hydroxybutyrate) Fibers Coated with Cellulose Derivatives for Sustainable Agricultural Applications

One of the latest trends in sustainable agriculture is the use of beneficial microorganisms to stimulate plant growth and biologically control phytopathogens. Bacillus subtilis, a Gram-positive soil bacterium, is recognized for its valuable properties in various biotechnological and agricultural applications. This study presents, for the first time, the successful encapsulation of B. subtilis within electrospun poly(3-hydroxybutyrate) (PHB) fibers, which are dip-coated with cellulose derivatives. In that way, the obtained fibrous biohybrid materials actively ensure the viability of the encapsulated biocontrol agent during storage and promote its normal growth when exposed to moisture. Aqueous solutions of the cellulose derivatives—sodium carboxymethyl cellulose and 2-hydroxyethyl cellulose, were used to dip-coat the electrospun PHB fibers. The study examined the effects of the type and molecular weight of these cellulose derivatives on film formation, mechanical properties, bacterial encapsulation, and growth. Scanning electron microscopy (SEM) was utilized to observe the morphology of the biohybrid materials and the encapsulated B. subtilis. Additionally, ATR-FTIR spectroscopy confirmed the surface chemical composition of the biohybrid materials and verified the successful coating of PHB fibers. Mechanical testing revealed that the coating enhanced the mechanical properties of the fibrous materials and depends on the molecular weight of the used cellulose derivatives. Viability tests demonstrated that the encapsulated B. subtilis exhibited normal growth from the prepared materials. These findings suggest that the developed fibrous biohybrid materials hold significant promise as biocontrol formulations for plant protection and growth promotion in sustainable agriculture.

Mechanism of the G/M ratio and zein in enhancing the mechanical and hydrophobic properties of sodium alginate films

This study developed an edible film based on calcium-crosslinked sodium alginate (SA) using the casting method. The investigation assessed how the α-L-guluronic acid/β-D-mannuronic acid (G/M ratio) and zein addition influence the film's physicochemical properties. Fourier transform infrared spectroscopy and scanning electron microscopy findings suggest that the G/M ratio modulates the film's physicochemical characteristics by altering SA molecular cross-linking strength and the film's network structure density. At a G/M ratio of 0.85, the film exhibits a more uniform network structure, enhanced moisture resistance, hydrophobicity, and mechanical properties. Zein, evenly dispersed within the film matrix, establishes strong hydrogen bonds and electrostatic interactions with SA, enhancing the film's network structure and boosting its thermophysical, mechanical, and moisture resistance characteristics. The study demonstrates that modifying the G/M ratio and incorporating zein enhances the film's mechanical and hydrophobic properties, broadening its potential applications in food packaging.

Host Material Viscoelasticity Determines Wrinkling of Fungal Films.

Microbial organisms react to their environment and are able to change it through biological and physical processes. For example, fungi exhibit various growth morphologies depending on their host material. Here, we show how the rheological properties of the host material influence the fungal wrinkling morphology. Rheological data of the host material was set in relation to the growth morphology. On host material with high storage modulus, the fungal film was flat, whereas on host material with low storage modulus, the fungus showed a morphology made of folds and wrinkles. We combined our findings with mechanical instability theories and found that the formation of wrinkles and folds is dependent on the storage modulus of the host material. The connection between the wrinkling morphology and the storage modulus of the host material is shown with simple scaling theories. The amplitude, number of wrinkles, and wrinkle length follow geometrical laws, and the mechanical properties of the fungal film are expected to increase with increasing host material elasticity. The obtained results show the connection between living biological films, how they react to their surroundings, and the underlying physical mechanisms. They can provide a framework to further design fungal materials with specific surface morphologies.

Natural Rubber Films Reinforced with Cellulose and Chitosan Prepared by Latex Aqueous Microdispersion.

In this paper, green composite films comprising natural rubber (NR), cellulose (CE), and chitosan (CS) were successfully fabricated through a simple, facile, cost-effective method in order to improve mechanical, chemical, and antimicrobial properties of NR composite films. Chitosan with a low molecular weight of 30,000-50,000 g/mol (CS-L) and a medium molecular weight of 300,000-500,000 g/mol (CS-M) was used for the fabrication. The composite films were prepared via a latex aqueous microdispersion method with different weight ratios of NR:CE:CS-L/CS-M. Fourier transform infrared spectroscopy (FTIR) results demonstrated strong interactions of hydrogen bonds between CE and CS-L/CS-M in the composite films. The tensile strength and the modulus of the composite films in dried form were found to significantly increase with the reinforcement of CE and CS-L/CS-M. The maximum tensile strength (13.8 MPa) and Young's modulus (12.7 MPa) were obtained from the composite films reinforced with CE at 10 wt.% and CS-L at 10 wt.%. The high elongation of 500-526% was obtained from the composite films reinforced with CE at 10 wt.% and CS (CS-L or CS-M) at 5.0 wt.%. The modification could also significantly promote antimicrobial activities and chemical resistance against non-polar solvents in the composite films. The NR composite films have potential uses as flexible films for sustainable green packaging.

Effect of γ-irradiation and antimicrobial agent on properties of poly(L-lactide) active films

Data on irradiation of poly(L-lactide) (PLLA) based active packaging is still limited. Therefore, effect of γ-irradiation on neat PLLA and active packaging with oligohexamethylene guanidine hydrochloride (OHMG·HCl) has been studied. Combined use of irradiation and active packaging technology is promising approach to maintain food safety and prolong shelf life. It has been found that regardless of the OHMG·HCl content PLLA undergoes chain scission during irradiation and this process becomes less pronounced at doses higher than 50 kGy. Slight racemization of PLLA during exposure has been observed using polarimetry and 13C NMR spectroscopy. Mechanical properties of films have been examined. Biocide addition led to a 30% decrease in films elongation at break. Irradiation either caused elongation decrease. Dose of 50 kGy and higher made PLLA active films brittle. Multiple melting behavior of irradiated PLLA has been analyzed by differential scanning calorimetry. Fraction of crystals with higher melting temperature rose with dose. Possible reason for this phenomenon is formation of α′ form with less ordered chain packaging that recrystallizes during heating. The biocide addition has not affected this process. Furthermore, in vitro antimicrobial test has shown efficacy of films with 2 wt.% of OHMG·HCl against gram-negative, gram-positive bacteria and fungi.

Influence of Oxygen and Nitrogen Flow Ratios on the Microstructure Evolution in AlCrTaTiZr High-Entropy Oxynitride Films

This study explores the influence of oxygen and nitrogen flow ratios on the microstructure and mechanical properties of AlCrTaTiZr high-entropy oxynitride films. Oxygen flow rates (0%–0.75%) were adjusted while maintaining a fixed nitrogen flow ratio (RN = 15%) to fabricate films with similar compositions. The results show that increasing oxygen flow enhanced hardness through solid solution strengthening and grain refinement, though excessive oxygen caused an amorphous structure and reduced hardness. After annealing at 900 °C, the hardness of all films was further increased. The film with a nitrogen flow ratio 40 times higher than oxygen exhibited the highest hardness of 21.8 GPa, along with superior mechanical performance. These findings highlight the potential of high-entropy oxynitride films for applications requiring high wear resistance and adhesion.

Photocurable Hypervalent Fluorinated Sulfur Containing Thin Films with Remarkable Hardness and Modulus.

Novel tetrafluoro-λ6-sulfanyl-containing oligomers prepared by visible light-promoted addition of 1,4-(bis-chlorotetrafluoro-λ6-sulfanyl) benzene or 1,3-(bis-chlorotetrafluoro-λ6-sulfanyl) benzene to either 1,4-diethynyl benzene or the 1,3-diethynyl isomers form hard, stress resistant thin films on spin casting. The isomeric oligomers were utilized to establish a structure-function relationship for the mechanical properties of films prepared from the oligomers. The Young's moduli of 145-nm-thick cured films could reach 60 GPa. The measured hardnesses, between 1.57 and 2.77 GPa, were more than double those of polymethyl methacrylate (PMMA) films. Curing of the tetrafluoro-λ6-sulfanyl-containing polymer films by UV irradiation resulted in coatings that exhibited remarkable hardness and modulus with good surface adhesion to silicon.

Reduced dielectric loss of MXene/PVDF composites with adding MnO2 nanorods

To reduce the dielectric loss of MXene/PVDF composites near the percolation threshold, a MnO2/MXene hybrid structure was successfully synthesized via an ultrasonic-assisted solution process, and MnO2/MXene/PVDF composite films were prepared by a solution casting method. The effects of different amounts of MnO2 nanorods on the microstructure, thermal stability, dielectric properties and mechanical properties of the composite films were investigated. At 1 kHz, the dielectric constant of 7 wt% MnO2/MXene/PVDF is 37.3, and the dielectric loss is as low as 0.05. The electric modulus curve, Nyquist curve and equivalent analog circuit of the composites revealed strong interface polarization and microcapacitance effects in the composites. In addition, the composite films exhibit excellent mechanical properties, and the storage modulus of the composite film loaded with 10 wt% MnO2 is 1990.5 MPa, which is 3.44 times that of pure PVDF. This study confirms that incorporating MnO2 nanorods into MXene/PVDF composites is an effective approach for fabricating high-performance dielectric composites.

Tailoring Mechanical and Optical Properties of Sputtered SiNx/BN Coatings.

The swift evolution of contemporary electronics products, such as flexible screens and wearable electronic devices, highlights the significance of flexible protective coatings, which combine superior mechanical and optical properties. Even though the recently developed polymer protective coatings can satisfy requirements for flexibility and transparency, their intrinsic nature often results in a hardness below 1 GPa, rendering them susceptible to scratches. On the other hand, traditional inorganic coatings, known for their high hardness and transparency, fall short of meeting flexibility requirements. In the present study, a SiNx/BN periodical nanolayered coatings (PNCs) structure has been tailored to achieve high mechanical durability, transparency, and flexibility. In SiNx/BN PNCs, the optical and mechanical properties of the single-layer SiNx film are crucial to the overall performance of the PNCs. Therefore, pulse direct current (DC) magnetron sputtering was optimized first to enhance the ionization efficiency of Si and N, thereby promoting their reaction and diminishing the presence of elemental silicon in SiNx. The effects of the pulse frequency and duty cycle on SiNx were evaluated. Additionally, the influence of the thickness ratio and modulation periods on the overall performance of the SiNx/BN PNCs was investigated. As a result, a SiNx/BN coating with sapphire-grade hardness, almost no optical absorption in the visible-near-infrared (vis-NIR) range, high wear resistance, and exceptional flexibility was demonstrated.

Enhancing mechanical properties of polyvinyl alcohol films through cellulose nanocrystals derived from corncob

Enhancing mechanical properties of polyvinyl alcohol films through cellulose nanocrystals derived from corncob

Development of multilayer composite film based on protein‐polysaccharides with the addition of onion waste extracts and their impact on the shallot quality

AbstractAt present, multilayer composite film is attractive in the production of biodegradable films due to its essential film properties. The current study mainly focused on overcoming the problems of poor water barrier and mechanical strength observed in monolayer films (SA‐CMC and G/SA‐CMC) made from gluten (G), sodium alginate (SA), and carboxymethylcellulose (CMC). The film was developed with the addition of onion waste extracts (OWEs), primarily from peel and stalk, to enhance functional properties. The multilayer composite film consists of three layers: an outer layer made of G, an inner layer made of SA, CMC, and a middle layer made of G/SA‐CMC. The developed composite film exhibited improved physical properties (thickness: 0.348–0.629 mm and moisture: 20.889%–21.403%), mechanical properties (tensile strength: 21.943–20.640 MPa), and barrier properties (WVP: 0.212–0.516 g/m.s.Pa × 10−14) compared to monolayer films (SA‐CMC and G/SA‐CMC). The addition of OWEs enhanced the multilayer film's phenolic (20.076 and 36.175 mgGAE/g) and antioxidant activity (73.850% and 42.667%). The study found that the multilayer control film had minimal changes in weight loss (9.75% ± 0.18%) and firmness (6.68 ± 0.64 N) compared to OWEs‐added films (9.93% ± 0.49–10.02% ± 0.14% and 6.61 ± 0.37 to 6.64 ± 0.18 N). However, fresh‐peeled shallot onion packed with control film exhibited higher bacterial counts (6.70 ± 0.42 CFU/g) and yeast and mold counts (5.08 ± 0.20 CFU/g) than those packed with the OWEs‐added film (6.49 ± 0.28–6.56 ± 0.27 CFU/g and 4.75 ± 0.18–4.89 ± 0.21 CFU/g), indicating that OWEs protect the onions from microbial degradation. Overall, the multilayer control film (without OWEs) showed better results for storing the fresh‐peeled shallot onion at 4°C for 21 days.Highlights Onion waste extracts have potent high antioxidant and antimicrobial properties Multilayer film's physical, mechanical, barrier, and functional properties improved Addition of onion waste extracts increased the film's antimicrobial activity Control film showed a better effect for storing fresh‐peeled shallot onion Developed film can store fresh‐peeled shallot onion for 21 days at 4°C.

Physical Crosslinking of Aqueous Polymer Dispersions: A Perspective

AbstractColloidal polymers, and in particular aqueous polymer dispersions, are widely used in commercial applications such as coatings and adhesives. Historically, the solvent resistance and mechanical properties of these systems have been improved by covalently crosslinking the polymer chains after drying. More recently, work has been directed toward replacing this covalent crosslinking, which typically involves highly reactive functional groups, by physical crosslinking through the use of supramolecular interactions. While conceptually similar to the use of covalent crosslinking, physical crosslinking has a unique influence on the rheology of the polymer, which leads to substantial differences in the development of mechanical strength during drying, as well as the mechanical properties of the final polymer film. In this perspective, the advantages and challenges of this approach are outlined, and an outlook for future research in this direction is provided.