Abstract:

Objective Virus epidemic takes place frequently worldwide, and the demand for medical protective clothing as an emergency epidemic prevention material is soaring. At present, the use of disposable protective clothing is a common practice, but it is difficult to deal with the medical wastes, which brings great load to the environment. In addition, medical staff are prone to sweltering, dizziness, nausea and other problems when carrying out high-intensity work. Therefore, there is a need for biological protective materials with high protection, high moisture permeability, washing resistance and applicability to the preparation of medical protective clothing.
Method Integrated design of biological protective materials was carried out with properties including high barrier, bacteria resistance, virus resistance, contamination resistance, high moisture permeability and washing resistance. Nano silver (AgNPs) antibacterial agent was prepared by chemical in-situ reduction with silver nitrate (AgNO₃) as silver source and waterborne polyurethane (WPU) as protective agent. It was mixed into thermoplastic polyurethane (TPU) solution and electrospun to prepare silver-loaded TPU nanofiber membrane, which was used as the inner layer of biological protective material. With the help of plasma technology, nano-scale grooves were etched in the surface of polyester fiber, and polydimethylsiloxane (PDMS) was used as hydrophobic finishing agent to treat polyester fabric, and PDMS hydrophobic film was formed on its surface, and this was used as the outer layer of biological protective material. The inner layer and the outer layer were glued together and compounded to obtain a complete biological protective material.
Results The surface of pure TPU nanofiber membrane was smooth, while uniform AgNPs particles were seen on the surface of silver-loaded TPU nanofiber membrane(Fig.1), suggesting that silver nanoparticles were successfully loaded on the TPU nanofiber membrane. The original polyester fiber has a smooth and flat surface. After plasma treatment, obvious grooves appear in the surface. After hydrophobic treatment, PDMS film is formed on the fiber surface (Fig.3). After hydrophobic finishing, the water contact angle of polyester fabric reaches about 140°, and after washing for 50 cycles, there is no downward trend(Fig.5), which indicates that PDMS is firmly combined with polyester matrix after film formation. When the silver content of the bioprotective material is 200 mg/kg, after washing for 50 cycles, the antibacterial rates of the biological protective material to Escherichia coli and Staphylococcus aureus are 99.89% and 99.27%, respectively. When the silver content increased to 300 mg/kg, after washing for 50 cycles, the antibacterial rate to Escherichia coli and Staphylococcus aureus was 99.99%. (Tab.1). The spraying wetting grade of biological protective materials is grade 5, and it drops to grade 4 after 50 cycles of washing (Tab.2). After 50 cycles of washing, the moisture permeability and tensile property of the biological protective material hadn't changed obviously, the water vapor transmission rate kept 2 654.8 g/(m²·24 h), and the breaking strength kept around 450 N (Fig.6). After 50 cycles of washing, the filtration performance of the bioprotective material remained stable, and the waterproof performance declined slightly. The filtration efficiency of solid particles remained above 99%, and the hydrostatic pressure decreased from 73.5 kPa to 53.6 kPa (Fig.7).
Conclusion The biological protective material prepared by the above method can be possibly used for the development of reusable medical protective clothing with active antibacterial and antiviral functions while efficiently blocking, thus achieving the purpose of efficient protection. TPU nano-fiber membrane enables both micro-pore and molecular moisture conductions at the same time, and the subsequent dispensing compound technology ensures the high comfort of medical staff to the maximum extent. In the future, reusable medical protective clothing is expected to popularly used, and lightweight and portable temperature regulating devices can be possibly prepared by 3D printing technology, so as to endure a medical protective clothing with high protection, high moisture permeability, temperature regulation and contamination resistance.

Key words: protective clothing, nano silver, polyurethane, polydimethylsiloxane, antibacterial, anti-contamination, biological protection