Functional Modification And Life Prediction Of Polyamide Parachute Fabric Coating

Parachute is a kind of special textile.According to the use of the parachute,the design of the parachute must meet the requirements of light weight,softness,airtightness,good mechanical properties,high dimensional stability,aging resistance and so on.The main way to obtain the standard parachute is to use nylon as the fabric and finish it with coating.At present,water-based polyurethane(WPU),which is environmentally friendly and has good toughness,is mostly used as the coating agent for the coating finishing of parachute coats.However,during the use of the parachute,due to the influence of multiple aging factors such as solar radiation,humidity,temperature in the high-altitude environment,and seawater immersion in the sea rescue process,the service life of the parachute will be affected,so it is necessary to carry out light aging and corrosion resistance functional modification of the parachute.Graphene oxide(GO)with high aspect ratio lamellar structure can improve the coating for water blocking performance so as to achieve the effect of corrosion resistance,and the chelated ring structure of polydopamine(PDA)can effectively absorb ultraviolet rays.In this paper,PDA grafted GO(PGO)composite nanoparticles were prepared and blended with WPU to improve the uv and corrosion resistance of WPU coating.In addition,according to the working condition of the use of sea rescue parachute in engineering application,the effects of three aging conditions of seawater immersion,xenon lamp aging and seawater immersion xenon lamp composite aging on the chemical structure,surface morphology,mechanical properties,air tightness and corrosion resistance of the coating are studied.Combined with the parachute implementation standards,the service life of the parachute is predicted,which is of great significance for the research and development of parachutes and the safe use of equipment.Firstly,the chemical structure,emulsion stability,thermal stability and hydrophilicity of four commercially available WPUs were compared,as well as coating performance for nylon parachute fabric,and the surface density,air permeability,corrosion resistance and uv resistance of coated parachute fabric.The results show that the coated parachute fabric with 12 wt% solid content LP-903 WPU meets the implementation standard,and has excellent shielding performance and uv resistance.Its low frequency impedance is the highest and UV resistance is the best.Then,PDA was grafted onto the surface of GO to prepare PGO composite nanoparticles by the carboxyl and epoxy groups on the surface of GO,and WPU was blends modified.When the addition amount of PGO ? 0.75 wt %,homogeneous stable emulsion can be obtained after mixing.The hydrophobicity of coated parachute fabric is improved,and the low-frequency impedance value is the highest,showing good corrosion resistance.In addition,PGO can effectively absorb UV light,So the UV protection performance is improved.Finally,an artificial simulated aging test was carried out on the double-coated parachute by referring to the operation conditions of the parachute used for sea rescue,and the effects of seawater immersion,xenon lamp aging and seawater immersion-xenon lamp combination aging treatment on the chemical structure,mechanical properties,air permeability and corrosion resistance of the coated parachute were studied.The results show that in the process of seawater immersion,the coating mainly hydrolyzes with WPU molecular chain ester group,which has little influence on the mechanical properties,corrosion resistance and air permeability of the parachute fabric.Compared with seawater immersion,under light conditions,light triggers the free radical reaction of ether bonds in the WPU molecular chain,leading to the fracture of the molecular chain.After 2 days of xenon lamp aging,the fracture strength of the parachute fabric decreases to the required strength.Under the condition of seawater soaking and xenon lamp aging,xenon lamp aging still plays a leading role in the mechanical properties of the parachute fabric.After soaking in seawater for 90 days and xenon lamp aging for 45 h,the breaking strength of the parachute fabric decreases from98.33 MPa to 79.73 MPa,and the parachute fabric fails when the aging time is extended.According to the actual working conditions,the safety service life of the polyamide garment is more than 680 days or more than 680 times in natural environment.