Study On The Preparation And Hydrophilic Properties Of PP/CHA Nonwovens

Melt-blown nonwovens possess a 3-dimentional network structure fabricated by ultrafine fibers, which gives them small pore size, high porosity, good filtration and absorption properties. Most of melt-blown nonwovens are made from polypropylene (PP), because of its low cost, ease of processing, favorable chemical and physical properties, such as lack of heat shrinkage, impact strength, tensile strength, and its ability to be drawn into very fine fibers. Therefore, PP melt-blown nonwovens have been produced for a wide range of applications. However, the inherently hydrophobic, low-free-energy, chemically inert surface of PP fiber limits the use of its nonwoven fabrics in many applications. At present, many nonionic surfactants have been used as migratory additives to render PP nonwovens'surface hydrophilic. But most of the traditional hydrophilic additives can only give temporary hydrophilic property to PP nonwoven fabrics, therefore, they can only be used as disposable products. CHA(commercial hydrophilic additive) is a hydrophilic internal additive for PP melt-blown nonwovens and endows PP nonwovens with durable hydrophilicity. In this article, the properties of PP melt-blown nonwoven fabrics modified by blending with CHA in different melt-blown process conditions are investigated.In this study, the property of the polymer materials is firstly investigated in order to establish the appropriate dual-slot-die parameters of melt-blowing process.Via differential thermal analysis (DSC), the melt temperature of PP is 160℃, while RZ(the traditional hydrophilic additive) and CHA show more complicatedly on DSC curve which have multi-melting points performance. By rheological analysis, the fluid viscosity decreases and the sheer stress increases of the three raw materials with the rise of temperature, so they are typical non-Newtonian fluids. Via X-ray diffractive analysis, the result shows the degree of crystallization is lower than before.The whole process is carried out by Polymer System invented by Engineering Research Center of Technical Textiles in Donghua University. Process conditions of spinning and formation have been discussed, which mainly include spinet temperature, hot air temperature, hot air pressure and distance from die to collector (DCD). What's more, it has studied on structure and properties of PP/CHA melt-blown nonwovens produced in different process conditions. Fibre diameter, web intensity, air permeability, filtration efficiency are investigated in order to analyze the effects of the parameters in melt-blowing process. The results show that:fibre diameter decreases at first and then increases with hot air temperature increasing and it decreases with hot air pressure increasing. Web intensity increases with hot air pressure increasing and decreases with DCD increasing. Filtration efficiency increases with hot air temperature and pressure increasing. Air permeability increases at first and then decreases with hot air temperature increasing and it increases with DCD increasing. In this experiment, the single regulator method are used and all process schemata are evaluated by Borda excess method, the results reveal that the comprehensive product properties are better when the process conditions are as follows:the concentration of CHA is 5.5%,the spinet temperature is 240℃,the air temperature is 295℃, the air pressure is 0.3Mpa and DCD is 12cm.In this research, the hydrophilic property, softness and antistatic property are further investigated. The hydrophilic property of PP/CHA melt-blown nonwoven fabrics is studied by testing the static water contact angle, the liquid absorptive capacity, the liquid wicking rate and the liquid strikethrough time. The static contact angle test proves that hydrophilic properties are obtained by means of using CHA, while the addition of RZ does not. The liquid absorptive capacity test illustrates that PP/CHA nonwoven fabric can absorb more than 10 times their weight in water. The liquid wicking rate test shows PP/CHA nonwoven fabric has the highest liquid wicking rate due to its hydrophilic groups transferred to the surface and form a hydrophilic film. The multiple liquid strikethrough time indicates that nonwoven fabric treated by RZ lost its wettability after 3 insults, while nonwovens containing 5.5% CHA remain hydrophilic even after 12 insults. It can conclude that PP/CHA melt-blown nonwoven fabrics have durable hydrophilic property. Furthermore, the softness is measured by testing the average friction coefficient and the antistatic property is measured by testing the surface specific resistance, and the results show that PP/CHA nonwoven fabrics have much better soft feel and antistatic property. Due to its specific advantages, PP/CHA melt-blown nonwoven fabric will be used more and more widely in many applications.