Span 80 is a compound that is a lipophilic nonionic surfactant. It can be used in cosmetics, food and pharmaceutical production.
Bamboo has the characteristics of fast growth, high yield, and degradability, and has great economic development value. However, because bamboo tissue is rich in nutrients such as starch, soluble sugar, and protein, it provides nutritional conditions for the growth and reproduction of mold. Mildew can easily occur under suitable temperature and humidity conditions, affecting the appearance and use of bamboo products. Therefore, it is of great significance to develop a green, environmentally friendly and mildew-proof method that can be applied to bamboo food utensils.
In order to enhance the anti-fungal properties of bamboo, using bamboo as a research material, the researchers first performed ultrasonic pretreatment on the bamboo, prepared an antibacterial paraffin emulsion, and impregnated and modified the bamboo.
The moisture content, water absorption, waterproof efficiency and mildew-proof performance of the modified bamboo were tested. 2-Hydroxy-1,4-naphthoquinone in natural plants was selected as the antifungal agent, and Span 80 and Tween 80 were selected as the compound emulsifier of No. 58 food-grade paraffin to prepare a stable antibacterial paraffin emulsion.
After using antibacterial paraffin emulsion to impregnate the ultrasonic-treated bamboo slices, an orthogonal experimental design was adopted, with the solid content of the paraffin emulsion, drying temperature and drying time as factors, and the moisture content and waterproofing efficiency after soaking for 768 hours as test indicators.
The results show that when the mass ratio of Span 80 and Tween 80 is 2:3 and the hydrophilic-lipophilic balance (HLB) value is 10.72, the paraffin emulsion has the best stability. It can be seen from the SEM image that the microscopic morphology of bamboo does not change significantly after ultrasonic treatment. Ultrasonic treatment can effectively remove starch in bamboo; a dense paraffin layer is formed on the surface of bamboo modified by paraffin emulsion impregnation.
The influences on the moisture content of modified bamboo from large to small are paraffin emulsion solid content, drying temperature, and drying time. When the solid content of the paraffin emulsion is 5%, the drying temperature is 70°C, and the drying time is 1.5 h, the minimum moisture content of the specimen is 4.11%. The effects on bamboo waterproofing efficiency after soaking for 768 hours are, from large to small, drying temperature, solid content of paraffin emulsion, and drying time.
When the solid content of the paraffin emulsion is 15%, the drying temperature is 40°C, and the drying time is 1.5 hours, the maximum waterproof efficiency of the specimen is 32.15%. Ultrasonic treatment cannot effectively prevent the mildew of bamboo. The anti-mildew performance of bamboo modified by ultrasound combined with antibacterial paraffin emulsion is significantly improved. The surface of the modified bamboo has no hyphae or mildew spots after a 28-day mildew test.
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Reference
- Effect of ultrasonic-antibacterial paraffin treatment on the antifungal performance of bamboo. Journal of Forestry Engineering, 2022,7(1):45-51.
