Whether the printing process of courier bags will affect their degradability is a question that has attracted much attention in the field of environmentally friendly packaging. The core of this issue lies in the interaction between the materials and process steps used in the printing process and the degradable characteristics of the courier bag itself, which needs to be analyzed from multiple dimensions such as ink composition, process treatment, and material compatibility.
From the perspective of ink materials, solvent-based inks commonly used in traditional printing processes contain a large amount of volatile organic compounds, which not only pollute the environment, but also may form a chemical film layer on the surface of courier bags that is difficult to degrade. When solvent-based inks are attached to the surface of degradable materials, the resin components and solvent residues they contain may hinder the decomposition of the courier bag substrate by microorganisms, resulting in a slowdown in degradation or even incomplete degradation. The water-based inks or soy-based inks used in environmentally friendly printing processes are different. These inks use water as a solvent or plant-based ingredients, have milder chemical properties, are more compatible with degradable materials, and have relatively less negative impact on the degradation process.
The surface treatment process before printing may also have an impact on degradability. In order to ensure the adhesion of ink on the surface of express bags, some printing processes require pretreatment of the bag body, such as corona treatment or coating of primer. If the coating material used in the pretreatment process is non-degradable, or the dense structure formed by the coating covers the molecular gap of the substrate, it may affect the contact between microorganisms and the substrate, thereby interfering with the degradation process. For example, some functional coatings may contain ingredients such as polyvinyl alcohol. If the coating thickness is not properly controlled or the degradation rate of the material itself does not match the substrate, a "protective layer" may be formed after the express bag is discarded, slowing down the overall degradation rate.
The selection and operation parameters of the printing process are also worthy of attention. Different processes such as flexographic printing, gravure printing, and screen printing have different requirements for the amount of ink and drying method. High-temperature drying processes may change the molecular structure of degradable materials and reduce the bioavailability of materials. Areas where ink is too thick may become "dead corners" in the degradation process because microorganisms are difficult to penetrate. In addition, full-page printing or the extensive use of dark inks may form a thicker ink layer on the surface of the courier bag. This physical barrier will directly affect the contact between the substrate and the degradation conditions such as microorganisms, moisture, and oxygen in the external environment, thereby inhibiting the degradation efficiency.
The impact of degradability is also reflected in the synergistic effect of materials and inks. The substrate of the courier bag is usually made of degradable materials such as polylactic acid (PLA) and starch-based polymers. The degradation of such materials depends on the enzymatic hydrolysis of microorganisms. If the printing ink contains antibacterial ingredients or chemical additives, it may inhibit the activity of microorganisms and thus destroy the biochemical process of degradation. For example, additives added to some inks to improve friction resistance may form an antibacterial layer on the surface of the material, making it difficult for microorganisms that can decompose the substrate to play a role, thereby extending the degradation cycle of the courier bag.
In practical applications, there have been many cases showing the relationship between printing technology and degradability. Some environmentally friendly courier bags printed with traditional inks have shown a phenomenon of delayed degradation in the ink-covered area in the composting environment, while the unprinted area or the area using environmentally friendly ink has more uniform degradation. This has also prompted the industry to explore more suitable printing solutions, such as using water-based inks with flexographic printing technology to control the amount of ink while ensuring printing clarity and reducing the impact on the degradation performance of the substrate. At the same time, some companies have tried to limit the printing content to non-major degradation areas, or use degradable printing auxiliary materials to balance the functionality and environmental protection of the packaging.
In order to reduce the impact of printing technology on degradation, some consensus measures have been formed in the industry. On the one hand, environmentally friendly inks with good compatibility with degradable substrates are preferred to ensure that the ink itself also has degradable properties; on the other hand, the printing process parameters are optimized to avoid excessive drying or ink accumulation, and lightweight printing design is adopted to reduce unnecessary ink coverage. In addition, the collaborative innovation of printing technology and material research and development is promoted, such as the development of degradable printing coatings or self-degradable ink connectors, so that the printing process from materials to processes can match the overall degradation requirements of environmentally friendly express bags, thereby realizing the packaging information transmission function while maintaining its environmental protection attributes to the greatest extent.
Overall, the impact of printing technology on the degradation of courier bags is not absolute, but depends on multiple factors such as ink type, process treatment, and material matching. Under the premise of rationally selecting environmentally friendly inks, optimizing printing processes and ensuring material synergy, the printing process can form a benign compatibility with the degradable characteristics of express bags. Solving this problem requires not only technological innovation, but also collaborative efforts from upstream and downstream of the industry chain in material research and development, process design, and standard setting to promote environmentally friendly packaging to achieve a true balance between function and environmental protection.
