Air permeability is one of the core performance indicators of white silicone paper, directly affecting its application in packaging, medical, and electronics fields. Optimizing air permeability requires comprehensive adjustments across seven dimensions: material formulation, coating process, fiber structure control, composite technology, post-processing, environmental adaptability design, and refined control of process parameters, to achieve a balance between air permeability and other properties.
Material formulation is the foundation of air permeability optimization. The substrate of white silicone paper is typically composed of plant or synthetic fibers. The type, length, and interlacing density of the fibers directly affect the porosity. For example, short fibers, due to their loose arrangement, can form more pores, improving air permeability, but this must be balanced with strength requirements. Furthermore, adding micropore-forming agents, such as paraffin hollow microspheres, to the silicone coating can create a nanoscale porous structure on the coating surface, retaining waterproof and oil-repellent functions while significantly enhancing air permeability.
The coating process has a decisive impact on air permeability. Traditional PE coatings or wax coatings will seal the pores on the paper surface, leading to a decrease in air permeability. Partial or gradient coating techniques can preserve the porous structure in critical areas while meeting moisture and oil resistance requirements. For example, in medical dialysis paper, optimizing the sizing amount and adding borax can reduce the sealing of fiber pores by the adhesive, decreasing moisture retention and thus improving air permeability.
Fiber structure control is a key method for optimizing air permeability. By adjusting the ratio of softwood pulp to hardwood pulp, paper strength and air permeability can be balanced. Softwood pulp fibers are longer, enhancing paper toughness; hardwood pulp fibers are shorter, increasing porosity. Using a mixture of both can create a multi-level porous structure, ensuring both air permeability and maintaining necessary mechanical properties. Furthermore, cold plasma treatment technology can control fiber surface wettability, reducing droplet adhesion and thus lowering air permeability resistance.
Composite technology provides new ideas for optimizing air permeability. Composite white silicone paper with air-permeable membrane materials (such as air-permeable nonwoven fabrics or metal microporous membranes) can form a gradient barrier structure. This structure satisfies the requirement for high breathability while enhancing overall mechanical properties through the synergistic effect of different materials. For example, in food packaging, composite aluminized BOPP film can strengthen packaging while maintaining uniform breathability and extending the shelf life of food.
Post-processing significantly improves breathability. Sanding or laser perforation techniques can create micropores on the surface of silicone paper, directly increasing air permeability channels. However, it is crucial to control the pore size and distribution to avoid affecting paper strength or allowing dust penetration. Furthermore, optimizing the drying process, such as adjusting drying temperature and airflow, can reduce paper shrinkage and maintain pore structure stability, thus ensuring breathability.
Environmentally adaptable design is an important direction for optimizing breathability. White silicone paper has diverse applications, requiring adjustments to breathability based on specific environments. For example, in high-humidity environments, paper easily absorbs moisture and expands, causing pore closure and reduced breathability. Adding waterproof adhesives or optimizing the wood pulp ratio can reduce moisture penetration while maintaining microporous air permeability channels. In high-temperature environments, silicone materials with better heat resistance must be selected to prevent a decrease in porosity due to thermal shrinkage.
Precise control of process parameters is essential for optimizing air permeability. During production, key parameters such as beating degree, coating amount, and drying temperature must be strictly controlled. Excessive beating leads to increased fiber fibrillation, increased paper density, and decreased air permeability; excessive coating amount closes pores, affecting air permeability. Through advanced equipment such as a closed-loop tension control system and a UV curing unit, precise control of process parameters can be achieved, ensuring the stability and consistency of the air permeability of white silicone paper.
