| At present,polyurethane(TPU)is the main raw material of elastic nonwovens in the domestic and foreign markets.However,TPU has high price,high viscosity and some defects in actual production.Therefore,it is a requirement for further development to look for elastic materials with low viscosity and suitable for melt blown.In this paper,polypropylene(PP)and ethylene vinyl acetate copolymer(EVA)were used as the main raw materials to prepare elastic melt blown non-woven fabric.The elastic non-woven fabric has a wide application prospect in the fields of medical and health materials,conductive materials and pressure sensors.Firstly,the properties of PP/EVA elastic melt blown masterbatch were discussed.In this paper,melt blown PP and EVA with high melt index were used as raw materials,and antioxidant was added in proper proportion.Each group of samples was melt blended by twin-screw extruder.The blends were prepared according to the proportion of 5%,10%,15%,20% and 25% EVA,and the properties of the blends were characterized and analyzed.The results of SEM showed that the blends had a "Sea Island" structure.The TG curves showed that the initial temperature of thermal decomposition and the corresponding temperature of 50% mass loss of blends were low.The thermal stability of the blends was poor,and there was obvious thermal decomposition at 364.7?C and 450?C.The DSC curves showed that there were two more and more obvious peaks on the melting curve and crystallization curve of the blends,which proved that the blends had two-phase structure.The rheological test showed that although the fluidity of the blends was better,the fluidity of the blends became worse with the increase of EVA content.Secondly,in order to further increase the compatibility of PP and EVA and improve the two-phase structure of PP/EVA blends,the effect of compatibilizer on the two-phase compatibility was studied by adding PP-g-MAH to PP/EVA blends.SEM results showed that PP/EVA/PP-g-MAH blends also had a "Sea Island" structure,but the distribution of EVA in PP phase was more uniform,which showed that compatibilizers could improve the compatibility of the two-phase interface,reduce the surface tension and strengthen the physical interaction between the two phases.TG curves showed that compared with PP/EVA blends,there was only one thermal decomposition process of PP/EVA/PP-g-MAH,and the corresponding temperature increases when the initial temperature and mass loss of the thermal decomposition are 50%,indicating that the addition of compatibilizer improved the thermal stability of the blends.DSC curves showed that there was only one melting peak and crystallization peak in PP/EVA/PP-g-MAH blends.The increase of crystallization temperature and crystallinity indicated that the compatibilizer improved the compatibility of PP and EVA.Rheological tests showed that the blends were slightly lower than that of PP/EVA blends,but the normal spinning could still be carried out.Thirdly,melt blown spinning experiments were carried out on PP/EVA blends with simple mixture,and the process was studied.Different receiving distance,hot air temperature and extrusion frequency were set up to analyze the influence of various parameters on fiber morphology,diameter,air permeability,thickness and mechanical properties.The results showed that the fiber diameter increased with the increase of receiving distance,extrusion frequency and EVA content,decreased first and then increased with the increase of hot air temperature.The permeability and thickness increased with the increase of receiving distance,hot air temperature,extrusion frequency and EVA content.The strength decreased with the increase of receiving distance,extrusion frequency and EVA content,and first increased and then decreased with the increase of hot air temperature.According to this,the best process parameters were: receiving distance was 30 cm,hot air temperature was 250?C,extrusion frequency was 1.5 Hz,and the blends with low EVA content were selected.Finally,PP/EVA/PP-g-MAH elastic melt blown nonwovens were prepared,and the effect of PP-g-MAH addition on the properties of PP/EVA melt blown nonwovens was discussed.The results showed that EVA in PP/EVA/PP-g-MAH melt blown nonwovens was more evenly dispersed in PP than PP/EVA.With the increase of EVA content,the fiber diameter was also significantly smaller than that of PP / EVA melt blown fabric,and the ejection state of the fiber also changed from intermittent to more continuous and uniform in the spinning process,which showed that the compatibilizer could improve the compatibility of PP and EVA,and make the melt blown nonwovens mesh more evenly.Although the strength was reduced,the elongation at break and the elastic recovery rate were significantly increased.The elongation at break increased from 24.6% to 40.2%,and the elastic recovery increased to 40%,indicating that PP-g-MAH could enhance the elasticity of PP/EVA melt blown nonwovens. |
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