Study On The Structure And Properties Of Polymer Membranes Regulated By Functional Nanofluids

Plastics are widely used because of their light weight,corrosion resistance,water resistance,durability and low cost,but the massive use of non-degradable plastics has put a huge pressure on the environment.This topic intends to address this issue from the perspective of plastic degradability and improving the durability of plastics.On the one hand,the project is inspired by skin perspiration and the need to extend the life of materials by giving them wear resistance without sacrificing their properties.On the other hand,a multifunctional biodegradable dressing with antibacterial properties was prepared by electrostatic spinning of cellulose nanocrystalline fluids and biodegradable polylactic acid(PLA)by ion-exchange.The main work in this project is as follows:(1)Silica nanoparticles were used as the core and the quaternary ammonium silane coupling agent was grafted onto the surface by covalent bonding,followed by the grafting of surfactants onto the outer layer by ion-exchange.The chemical structure and core-shell structure of the silica nanofluids were characterised by FTIR and TEM,and the liquid-like behaviour and temperature responsiveness of the silica nanofluids were confirmed by rheological tests.Monodisperse solvent-free silica nanofluid and PMMA were co-mixed and solution casting to obtain homogeneous multifunctional films.The COF of the composite films was found to decrease with increasing Si O₂ nfs content by friction testing machine,and the lowest COF of the composite films was found at 10%weight of Si O₂ nfs(3 times lower compared to the pure sample).The thermal responsiveness of the films was characterised by WCA,AFM,XPS and SEM,and these data show that the COF of the composite films appeared to decrease upon heating when the Si O₂ nfs content was less than or equal to 10%.Due to the small size and bilayer ionic structure of Si O₂ nfs on the PMMA surface,the composites showed excellent hydrophilicity(WCA of the composite film remained around 15°after mixing with Si O₂ nfs),anti-fogging,anti-static properties and high transparency(all samples had a light transmission of>85%).(2)The cellulose powder was converted into cellulose crystals by acid hydrolysis and then prepared into cellulose nanocrystalline fluids(CNCfs)by ion-exchange.The core-shell structure was characterised using FTIR and TEM;the heat resistance was characterised by thermogravimetric analysis(TG),and the rheological tests demonstrated the fluid-like behaviour and low viscosity.The PLA/CNCfs fibrous membrane was prepared by embedding it into PLA by means of electrostatic spinning.Instron were used tested the mechanical properties of the composite films,demonstrating the ability of CNCfs to simultaneously enhance the toughening effect;the hydrophilicity of the composite films was characterised by Water contact angle measurement,moisture permeability measurement and capillary height measurement,showing that PLA/CNCfs has outstanding superhydrophilicity(water contact angle of 0^o)and super water absorption capacity,and WVTR=3.612 g·m^-2·h^-1(81 times higher than that of pure PLA membranes).In addition,a series of physical properties of the membranes were tested using infrared thermography,bulk resistance and thermal conductivity instruments,and the results showed that the PLA/CNCfs fibre membranes had good antistatic properties,and excellent heat dissipation(2°C less relative to the PLA body),where PLA/CNCfs had the highest thermal conductivity when the CNCfs content was 20 wt.%(up to0.27 W/m K).The antibacterial peculiarities of the composites were characterized by antibacterial experiments,which showed that PLA/CNCfs had good antibacterial properties,with inhibition rates of up to 98.5%and 92.7%for E.coli and S.aureus respectively.