一,The anti-static genes of natural fibers: from their physical structure to their material characteristics
Waste paper, sugarcane bagasse, and bamboo fiber are all natural plant fibers that are used to make molded pulp. The three-dimensional network fiber structure of molded pulp provides natural anti-static properties. The friction coefficient between fibers is minimal, and the surface of plant fibers has polar groups like hydroxyl groups that can provide weak conductive pathways and stop static charge from building up. The experimental data indicates that the surface resistivity of molded raw pulp lacking anti-static treatment can attain values between 10¹¹ and 10¹² Ω·cm. While this does not fully satisfy the protective requirements for electronic equipment, it represents a substantial improvement over traditional EPS foam, which has a surface resistivity exceeding 10¹ Ω·cm.
More significantly, natural fibers can control the humidity inside the package since they let water through. When the humidity in the air is kept between 40% and 60%, the water molecules that stick to the fiber surface can form a conductive film. This makes it even less likely that static electricity would build up. This property allows molded pulp to actively keep the microenvironment inside the packaging stable while precision electronic parts are stored for a long time. This keeps humidity changes from causing electrostatic discharge (ESD) incidents.
二, Changes in anti-static technology: from covering the surface to changing the slurry
To meet the demanding criteria of electronic devices for anti-static performance, molded pulp technology has developed three main technical routes:
1. An anti-static agent is added to the slurry, which is a basic solution.
When alkyl sulfates and zwitterionic polymers are added to the pulp during the pulping process, they can produce a conductive network on the surface of the fibers. For example, Shandong Juli's internal anti-static agent works by using polar groups to pull moisture from the air, creating a dynamic conductive route, and keeping the surface resistivity of pulp molding at 10 ⁶ -10 ⁹ Ω· cm. The anti-static effect lasts for more than 12 months. This approach only costs 0.3 to 0.5 yuan per kilogram, which is 60% less than the old way of coating things from the outside. It also works well with natural materials like sugarcane bagasse and bamboo fiber, and it doesn't change how well the substance breaks down.
2. Conductive fiber composite technology: making a three-dimensional conductive network
The industry has created graphite/carbon black composite fiber reinforcing technology for situations that require very high accuracy, including new energy batteries and semiconductors. A turbine beater evenly spreads conductive fibers throughout the pulp, creating a three-dimensional conductive channel. This can lower the volume resistivity to as low as 0.015 Ω· cm. After a certain brand of mobile phone employed a 4:3 ratio of graphite/carbon black fibers, the surface resistance of the packing liner went down to 10 ⁴ Ω. This fixed the scratch problem that was caused by electrostatic adsorption on the camera module. The yield of the product went up from 92% to 98.5%.
3. New ideas for surface coatings: a big step forward in functional integration
The industry has made multifunctional composite coatings to satisfy the needs of coatings that are anti-static, waterproof, and resistant to oil. For instance, spraying a nano hydrophobic coating with a carbon black conductive agent on the surface of pulp molding can create an electrostatic discharge channel and make the surface waterproof by making the contact angle 150 °. When this technology is used to package a given medical device, the packaging's surface resistance is ≤ 10 ⁸ Ω, and it meets the IPX4 waterproof level and ISO 13485 medical certification.
三, Covers many types of applications, from consumer electronics to industrial equipment
The anti-static properties of molded pulp have permeated the entire electronic equipment industry chain:
In the world of consumer electronics, the packaging for the Apple iPhone 15 series is made of 100% fiber-based materials. To get a surface resistance of ≤ 10 ΩΩ, anti-static chemicals are added to the slurry. When combined with wet pressing technology, a buffer layer is made that fits the shape of the phone perfectly. This not only protects the parts from damage caused by electrostatic adsorption, but it also makes the unboxing experience better.
Tesla charging stations come with a double-layer pulp molding construction in the industrial equipment area. To make the outer layer impact-resistant, conductive fibers are added. To protect the circuit board, the inner layer is covered with an anti-static coating. ISTA 3A transportation testing has shown that the single box loading capacity is now 60% higher than it was with plastic packing.
Cochlear cochlear implants are packaged with antibacterial and anti-static pulp molding in the high-end medical area. The surface resistance is < 10 ⁸ Ω, and the implants are coated with nano silver ions for double protection. This keeps the environment sterile and protects the precise components.
