Preparation And Properties Of Micro-nano Coated Cotton Fabric With Flame-retardancy And Super-hydrophobicity

Cotton textiles are inexpensive and widely available,with excellent moisture-absorbing and breathable properties,skin-friendly and wear-resistant,and less prone to static electricity,so they are widely used in clothing,home textiles,transportation,medical care and many other fields.As a flammable material,however,cotton fabrics are a great fire safety hazard in use.Therefore,it is important to improve the fire safety performance of the fabric in order to build a fire barrier.The construction of flame retardant coatings on the surface of fabrics is currently one of the most effective and practical ways to achieve flame retardancy in cotton fabrics.However,the traditional flame retardant coating has a high loading capacity due to low flame retardant efficiency,which in turn seriously affects the softness and moisture absorption and breathability of the fabric,so there is an increasing need to develop a novel flame retardant coating with high efficiency and excellent performance.At the same time,cotton fabrics are also prone to contamination,non-waterproofing and single performance,so it is necessary to treat them with hydrophobic treatment.As a low surface energy substance,silicone compounds are green hydrophobic agents,and research has shown that combining them with metal organic framework（MOF）micro-nanoparticles to build a micro-nano coating with a rough structure can give the substrate surface superb hydrophobic and self-cleaning properties.In addition,both have good thermal properties and can act as synergistic flame retardants with flame retardants.Therefore,this thesis adopts a simple and easy method to synthesise a highly efficient halogen-free flame retardant and a fluorine-free micro-nano hydrophobic agent to prepare flame retardant and super hydrophobic dual-functional fabrics,to investigate the mechanism of synergistic flame retardancy of flame retardant and hydrophobic coatings,and to consider the effect of the composite coating on the serviceability of the dual-functional fabrics,so as to achieve an organic combination of flame retardancy and hydrophobicity while ensuring the serviceability of the fabrics.The specific research contents and the conclusions are as follows:（1）Synthesis and performance study of P/N/Si multi-element synergistic flame retardants:The flame retardant precursor octa-amino caged poly（sesquisiloxane）（A-POSS）was synthesized under acid-catalyzed conditions using 3-aminopropylethoxysilane（ATPES）as raw material,and then a P/N/Si multi-element synergistic flame retardant was prepared by grafting phosphite on the active amino group of the precursor through the Mannich reaction（PPA-POSS）,and a series of flame retardant fabrics with different coating loadings were prepared by finishing the flame retardant onto the surface of cotton fabrics through a simple impregnation treatment.Scanning electron microscopy（SEM）and Fourier transform infrared spectroscopy（FTIR）tests were used to confirm the successful construction of the flame retardant coating on the cotton fabric surface.The results show that at a flame retardant loading of only 4.2 wt%,the limiting oxygen index（LOI）of the flame retardant fabric（CTF2）increased from 18.0%to30%for pure cotton and was self-extinguishing in a vertical burn test.Further increasing the flame retardant loading to 6.4 wt%,the LOI of the flame retardant fabric（CTF3）continued to increase to 34%,with a damage length of only 28 mm in the vertical burn test,and the cone calorimetric（CONE）test results showed that the peak heat release rate（PHRR）and total heat release（THR）decreased by 47.6%and 33.9%respectively compared to cotton.The above findings indicate that the P,N and Si multi-element co-efficient flame retardant synthesized in this work has excellent flame retardant effect and very high flame retardant efficiency.（2）Preparation and properties of ZIF-67@PDMS micro and nano superhydrophobic coated fabrics:Two zeolitic imidazole ester skeletons-67（ZIF-67）with different morphologies were prepared using Co²⁺as the metal centre and 2-methylimidazole as the organic ligand,and their morphologies were analysed by field emission scanning electron microscopy（FESEM）.Further,the hydrophobic modification of the two ZIF-67 microparticles with polydimethylsiloxane（PDMS）was inspired by the specific wettability characteristics of living organisms such as the"lotus leaf effect"in nature,and they were deposited on the surface of cotton fabrics by a simple spraying method to construct hydrophobic coatings with micro-and nano-level rough structures.The effect of the ratio of PDMS to ZIF-67 on the hydrophobic properties of the modified fabrics was investigated.The effect of PDMS and ZIF-67 on the hydrophobic properties of the modified fabrics was investigated.The results show that the PDMS-modified low-temperature ZIF-67 is simple to prepare and the treated fabric（CTF-PHB2）has better superhydrophobicity with a contact angle（WCA）of 159.4°and exhibits excellent resistance to washing and rubbing,and after 50 rubbing cycles and 50 washes,CTF3-PHB2 still has good hydrophobicity with WCA 139.4°and 131.5°,respectively.Further results on drapability and breathability and moisture permeability show that the micro-nano hydrophobic coating retains similar flexibility and breathability and moisture permeability to the original cotton,making the finishing process a potential application.（3）Preparation of PPA-POSS@ZIF-67@PDMS micro and nano coated fabric and its performance study:Combining flame retardant finishing with hydrophobic finishing,the flame retardant super hydrophobic composite micro-nano dual function coated fabric CTF3-PHB2was prepared.The combustion performance analysis revealed that,compared to pure cotton PHRR,THR and average burning efficiency（av-EHC）values of CTF3-PHB2 were significantly reduced by 51.4%,56.2%and 68.4%,respectively,and the carbon residual rate was significantly increased by 94.6%.In addition,the fire safety performance of CTF3-PHB2was further improved compared to the pure flame retardant fabric CTF3,confirming that the hydrophobic coating can act as a synergistic flame retardant with the flame retardant coating.The hydrophobic performance results show that CTF3-PHB2 has a WCA of 159.3°,similar to that of the pure hydrophobic fabric CTF-PHB2,showing excellent superhydrophobicity,indicating that the introduction of the flame retardant coating did not affect the hydrophobicity of the coating.In addition,the morphology,element distribution and graphitization degree of the carbon residue were studied to reveal the mechanism of the influence of the hydrophobic coating on the flame retardant properties.A comprehensive assessment of the in-service properties of the fabrics was also carried out by analysing the mechanical properties,flexibility and draping properties of the flame retardant hydrophobic fabrics.The results show that the bifunctional fabrics still retain good original properties compared to the pure cotton fabrics.