Abstract
Environmentally friendly and biodegradable polyvinyl alcohol (PVOH) film combined with Phellodendron amurense extract was used to prepare an anti-UV composite film through thermal flow molding technology. The prepared PVOH composite film containing Phellodendron amurense extract exhibited UV-resistant properties, with the composite film made from leaf extract showing the highest UV resistance. Additionally, the tensile strength and toughness of the PVOH composite film with added Phellodendron amurense extract significantly increased compared to pure PVOH film. Studies on film-forming and UV-resistant mechanisms have revealed that extract particles can act as nucleating agents to promote the local ordered arrangement of PVOH molecular chains, forming microcrystalline regions. This enhances the tensile strength of composite films while maintaining their toughness. During the film-forming process, the extract forms hydrogen bonds with PVOH, and the benzene ring conjugated double bonds in the extract can absorb ultraviolet light, contributing to the UV resistance of the PVOH composite film. The composite film prepared from Phellodendron amurense extract and PVOH with UV resistance and high strength can be applied in fields such as packaging, food, and sunscreen products, which is of great significance for promoting the efficient development and utilization of biomass resources.
Download PDF
Full Article
High-Strength UV-Resistant Polyvinyl Alcohol Composite Films Based on Phellodendron amurense Rupr Extract
Feng Li,a Hongpeng Li,a Guo Li,a Yujia Zhang,b Haoyu Ma,c and Min Tang a,*
Environmentally friendly and biodegradable polyvinyl alcohol (PVOH) film combined with Phellodendron amurense extract was used to prepare an anti-UV composite film through thermal flow molding technology. The prepared PVOH composite film containing Phellodendron amurense extract exhibited UV-resistant properties, with the composite film made from leaf extract showing the highest UV resistance. Additionally, the tensile strength and toughness of the PVOH composite film with added Phellodendron amurense extract significantly increased compared to pure PVOH film. Studies on film-forming and UV-resistant mechanisms have revealed that extract particles can act as nucleating agents to promote the local ordered arrangement of PVOH molecular chains, forming microcrystalline regions. This enhances the tensile strength of composite films while maintaining their toughness. During the film-forming process, the extract forms hydrogen bonds with PVOH, and the benzene ring conjugated double bonds in the extract can absorb ultraviolet light, contributing to the UV resistance of the PVOH composite film. The composite film prepared from Phellodendron amurense extract and PVOH with UV resistance and high strength can be applied in fields such as packaging, food, and sunscreen products, which is of great significance for promoting the efficient development and utilization of biomass resources.
DOI: 10.15376/biores.20.4.8725-8736
Keywords: Composite film; Phellodendron amurense Rupr; Extract; UV-resistant
Contact information: a: Research Institute of Characteristic Flowers and Trees, Chengdu Agricultural College, Chengdu, 611130 China; b: Wood Industry and Furniture Engineering Key Laboratory of Sichuan Provincial Department of Education, Sichuan Agricultural University, Chengdu, 611130 China; c: Taiyuan Institute of Forestry Sciences, Taiyuan, 030002 China; *Corresponding author: mintang991@gmail.com
GRAPHICAL ABSTRACT
INTRODUCTION
Environmental pollution and human health issues caused by social development are receiving increasing attention (Xu et al. 2022). Using effective protective measures can mitigate the harm caused by environmental factors such as ultraviolet radiation to the human body (Khan et al. 2020). Traditional UV protection methods mostly rely on chemically synthesized materials, which suffer from poor environmental friendliness and high costs (Egambaram et al. 2020). However, under the influence of environmental hazards such as ultraviolet radiation, natural plants still maintain good growth conditions while thriving in their natural habitats (Ueda and Nakamura 2011). As a result, the inherent UV-resistant properties of plants have attracted widespread attention.
The Amur cork tree (Phellodendron amurense Rupr) is a deciduous tree belonging to the Rutaceae family and is distributed in the northeastern and northern provinces of China (Zhang et al. 2023). Its wood is widely used in furniture and decoration, and its extracts can be processed into soap, lubricants, insecticides, and dyes (Ji et al. 2023). The cork layer of Phellodendron amurense bark can be used to make cork stoppers. The alkaloid components such as berberine, palmatine, and jatrorrhizine contained in its leaf and fruit extracts have significant antibacterial, antioxidant, antitumor, anti-inflammatory, hypoglycemic, and immunosuppressive activities. Also, the extracts from different parts of P. amurense have demonstrated excellent activity and broad applications (Akihisa et al. 2017). However, the use of pure Phellodendron extracts is limited in scope, particularly as there have been no reported studies on utilizing its components for UV protection research. Therefore, the potential and applications of Phellodendron extracts await further exploration.
Composite materials combine the advantages of more than one material, enabling the integration of materials with different functionalities (Gibson 2010). Polymer-based biomass film composite materials are widely used in various fields such as food packaging, agricultural settings, and outdoor protection (Bhardwaj et al. 2020). Film composite materials have broad application prospects in areas such as UV-resistant functionalization (Dai et al. 2025). By incorporating strong ultraviolet absorbers such as benzotriazoles, light stabilizers, and nanofillers (TiO2, ZnO) into the film composites, the materials’ UV resistance and shielding capabilities can be enhanced (Zhang et al. 2024). However, these additives face issues of high economic and environmental costs such as photodegradation, migration, and environmental persistence. While benzotriazole derivatives typically exhibit strong UV absorption in the range of 290 to 360 nm, their compatibility with polymer matrices and long-term stability can be problematic. Newly developed natural UV-resistant substances based on lignin, tannins, and plant extracts provide fresh perspectives for the development of UV-resistant film composites. For example, bio-based films were found to suppress UV transmittance very well below 400 nm, along with improved transparency and environmental friendliness (Wang et al. 2023). In particular, plant extracts have garnered widespread attention in UV-resistant film composites due to their advantages of low cost, abundant resources, and easy accessibility. Plant extracts have gained increasing attention as natural UV-shielding agents due to their abundance of bioactive compounds, such as flavonoids, polyphenols, and alkaloids, which possess strong UV-absorbing capabilities. These compounds typically contain conjugated double bonds and aromatic ring structures that enable them to absorb and dissipate harmful ultraviolet radiation, particularly in the UVA and UVB ranges (Chandran et al. 2024). However, the poor mechanical properties caused by the compatibility issues between the polymer matrix and plant extracts have become a major obstacle in the preparation of UV-resistant composite films. Therefore, it is imperative to develop a plant extract-based UV-resistant film composite with excellent compatibility and superior anti-UV performance.
To address the efficient development and utilization of Phellodendron amurense extracts and the preparation of plant extract-based UV-resistant film composites, this study combined extracts from different parts of P. amurense with PVOH. Using thermal flow molding technology, UV-resistant composite films were successfully prepared, and they demonstrated excellent UV-blocking performance in the UVB range as well as high tensile strength. Meanwhile, based on the compositional characteristics of P. amurense extract and its binding properties with PVOH, the mechanical reinforcement and UV resistance mechanisms of the composite film were investigated. The preparation and mechanism analysis of PVOH-based UV-resistant composite films derived from P. amurense extracts not only provides a foundation for the refined and high-value utilization of P. amurense but also offers new perspectives for the development of UV-resistant composite materials.
EXPERIMENTAL
Materials
The Phellodendron amurense tree was harvested from Laoban Mountain in Yucheng District, Ya’an City, Sichuan Province, China. A total of 10 g of dried and crushed fruit, branch, and leaf powder were wrapped separately with qualitative filter paper and placed in a 250 mL Soxhlet extractor. Ethanol (250 mL) was used for extraction in a 500 mL round-bottom flask for 8 h to obtain the extract. The three extracts were concentrated to remove the remain ethanol by rotary evaporation.
Polyvinyl alcohol (PVOH) was commercially sourced with a polymerization degree of 1700 to 1800, molecular weight of 84,000 to 89,000, viscosity of 21 to 26 Pa·s, pH 5 to 7, and mesh size of 120 mesh.
Method
First, 1 g of polyvinyl alcohol (PVOH) was dissolved in 20 mL of ultrapure water at 85 ℃ with continuous magnetic stirring to prepare a 5 wt% PVOH solution. The ethanol extracts of branches, fruits, and leaves were added into the PVOH solution, which was stirred slowly for 15 min. The mixture was poured into a plastic Petri dish with a diameter of 8.5 cm (ensuring uniform thickness of the PVOH composite film by adding the same mass of the mixed solution). After solvent evaporation, the film was peeled from the dish and cured at room temperature for 24 h before characterization. The preparation process for the pure PVOH film was the same, except without the addition of ethanol extracts from the plant parts. A total of 3 sample groups were prepared, each with 4 mass gradients (0.05 wt%, 0.15 wt%, 0.25 wt%, and 0.35 wt%, respectively). Each group of specimens with 4 mass gradients was tested 3 times for the follow properties test.
Character
UV-resistant properties
The prepared composite films were cut into 10 mm × 20 mm pieces, then placed in cuvettes and pressed against the sidewall near the light source. A spectrophotometer was used to perform wavelength scanning within the range of 190 to 800 nm.
The color of the film surface
The prepared PVOH composite film was subjected to color testing using a colorimeter. The prepared composite film was placed under the colorimeter, and D65 standard illuminant with TAPPI/ANSI T 524 om-20 (2020). The CIE LAB color space was used for color specification. In that system, L* represents the value on the white/black axis, a* represents the value on the red/green axis, and b* represents the value on the blue/yellow axis. The a* value best reflects the variation between green and red, where a lower a* value indicates a greener color of the sample. The b* value reflects yellow/blue, with a lower b* value indicating a bluer sample.
Mechanical properties
The prepared film was cut into dimensions of 50 × 5 × 0.12 mm for mechanical property testing. The testing was performed using a DZW-103A micro-mechanical testing machine from Sichuan Ruili Zhongheng Technology Co., Ltd. (Chengdu, China).
Film formation and UV resistance mechanism
The prepared composite film was observed for surface morphology using SEM (ZEISS Sigma 360, Germany). FTIR (Thermo Fisher Scientific Nicolet iS20, USA) testing was performed with a scanning range of 800 to 4000 cm-1 and a resolution of 4 cm-1.
RESULTS AND DISCUSSION
UV Resistance of the Film
The PVOH film composite with Phellodendron amurense extract exhibited excellent UV resistance, while films incorporating extracts from leaves, fruits, and tree branches showed varying UV resistance properties. Additionally, films with different extract addition amounts also demonstrated distinct UV resistance capabilities (Fig. 1a, b, c). The film using P. amurense leaf extract exhibited maximum UV absorbance in the UVB range (280 to 315 nm). Among them, the composite film with a 0.35 wt% addition showed the highest UV absorbance. However, the highest UV absorbance of the composite film with 0.05 wt% addition was lower than that of the PVOH film without extract (Fig. 1a, b), indicating that the composite film only was able to demonstrate UV resistance when the concentration of P. amurense leaf extract exceeded a certain threshold.