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Carbon neutrality is a global goal for more than 130 countries and regions. Therefore, clean and environmentally friendly packaging materials using bio-based and biomass materials are being developed. However, conventional packaging materials available in the market, such as polyethylene, polypropylene, and polyethylene terephthalate, are non-biodegradable and mostly derived from petroleum, thus causing adverse effects on nature, especially the marine environment [5]. In addition, biodegradable packaging materials cannot maintain their quality without improving their performance. Therefore, it is strongly recommended to develop affordable, non-toxic, and biodegradable food packaging polymers.
The main point of this paper
Challenges of PVA film:
Although PVA film has advantages such as biodegradability and biocompatibility, its low water resistance, high water vapor permeability and poor thermal properties limit its application in some fields.
Electrospinning technology:
Electrospinning technology is used to manufacture fiber nanomaterials with different chemical and physical properties, which can improve the thermal, mechanical and electrical properties of polymer nanocomposites.
Application of PCL nanofibers:
Hydrophobic PCL nanofibers are used to improve the physical properties of PVA film. PCL is a biodegradable material with good mechanical properties and easy processing.
Interface interaction problem:
Poor interface interaction between hydrophilic PVA substrate and hydrophobic PCL nanofibers affects adhesion and delamination, and reduces physical properties such as tensile strength and thermal properties.
Surface modification technology:
A new surface modification technology is proposed in the study. By changing the pre-drying time, PVA and PCL nanofiber (PVA/PCL) composite films are prepared by direct electrospinning on the surface of PVA film with different solvent contents.
Performance Study:
The chemical and physical properties of PVA/PCL composite films were investigated to determine their feasibility as surface modifiers for hydrophilic PVA films, aiming to enhance the physical bonding and interaction between PCL nanofibers and PVA films.
Limitations of PVA Nanofiber Membrane:
PVA Nanofiber Membrane has excellent oxygen barrier and biodegradability, but its hydrophilicity leads to poor physical properties.
Surface modification technology:
The surface of PVA film is modified by controlling the pre-drying conditions of PVA Nanofiber Membrane and adjusting the electrospinning process of PCL nanofibers.
Effect of pre-drying time:
The shorter the pre-drying time, the higher the residual solvent content and the better the flexibility of the coated PVA film.
Improved interface bonding:
With the shortening of drying time, the physical bonding of PCL nanofibers to the PVA surface is improved and the penetration depth is increased.
Contact angle change:
The contact angle of PVA/PCL composite Nanofiber Membrane with different pre-drying times increases from 8.3° to 95.1°, indicating that the surface hydrophilicity and hydrophobicity are significantly changed.
Improved physical properties:
The tensile strength of pure PVA Nanofiber Membrane increased significantly from 7.5 MPa to 77.4 MPa, and the oxygen permeability decreased from 5.5 cc/m2-day to 1.9 cc/m2-day.
Cost-effectiveness:
The newly developed technology is highly cost-effective and can modify the surface and physical properties of hydrophilic polymers.
In this study, PVA/PCL composite films exhibited enhanced mechanical strength, excellent barrier properties, WCAs, and physical bonding between hydrophobic nanofibers and the hydrophilic polymer matrix. Control of predrying conditions and optimization of the electrospinning process were key steps in achieving the film properties. The effect of predrying time on the penetration depth of PCL nanofibers was investigated, revealing a relationship between predrying time and penetration depth. Moreover, this finding was associated with the change in residual solvent content in the predried PVA films. Higher solvent content in the PVA films increased the mobility of polymer chains, facilitating the penetration of PCL nanofibers into the PVA films. The difference in penetration depth had a significant effect on the physical properties of the materials. The results showed a significant correlation between predrying time and WCA of PCL/PVA composite films, which was attributed to the higher exposure of PCL nanofibers on the film surface. PVA/PCL composite films, especially PD-15, showed substantial improvements in mechanical properties due to the presence of PCL nanofibers and reduced pore formation. Independent of the predrying time, the incorporation of PCL nanofibers improved the oxygen barrier properties. Therefore, optimizing predrying conditions and precisely tuning electrospun nanofibers can improve the physical bonding and surface chemical properties of hydrophilic polymer film substrates and expand their packaging applications.
