| Melt-blown process can produce superfine fiber nonwovens in mass.The nonwovens are widely used in medical and health care,adsorption and filtration,heat preservation,oil absorption and other fields due to their characteristics of small fiber diameter and interfiber aperture,large porosity and super-fluffy fiber net structure.However,most melt-blown nonwovens currently in circulation on the market are made from polypropylene(PP),which is a non-renewable petroleum-based polymer material.Not only does the synthesis process requires a lot of energy,but is greatly hard to degrade after waste,which brings enormous challenges to resources and environment.Consequently,it will be crucial to develop environment-friendly melt-blown nonwovens that are both recyclable and biodegradable to completely replace PP melt-blown nonwovens.In recent years,polylactic acid(PLA),a biodegradable material,has entered the human field of vision inch by inch.It has both renewable and degradable properties,good biocompatibility and processability,so melt-blown nonwovens using PLA as raw material will have a very broad application prospect.However,the inherent mechanical brittleness of PLA leads to poor toughness of melt-blown nonwovens,and the application of the products is also limited.In order to obtain PLA melt-blown nonwovens with excellent toughness and biodegradability,which can be applied in a wider range of fields,in this paper,PLA melt-blown nonwovens were toughened by polyethylene glycol(PEG)with molecular weights of 1000,2000,4000 and 8000(They are named PEG-1000,PEG-2000,PEG-4000,and PEG-8000respectively).PLA/PEG-1000,PLA/PEG-2000,PLA/PEG-4000 and PLA/PEG-8000 blend materials for melt-blown were prepared through the melt blending.The infrared spectrum,section morphology,crystal construction,isothermal crystal morphology and mechanical properties of PLA and PLA/PEG blend materials used for melt-blown were tested and analyzed.Then,the spinnability was evaluated by characterizing and analyzing the flow properties,rheological properties,thermal stability and thermal-crystallization properties of PLA and PLA/PEG blend materials used for melt-blown,which furnishes reference for the setting of preparation parameters of PLA and PLA/PEG melt-blown nonwovens.On this basis,further PLA and PLA/PEG melt-blown nonwovens containing different molecular weights of PEG were prepared,and the apparent morphology,fiber diameter and diameter distribution,surface density,thickness,porosity,pore size and pore size distribution between fiber,hydrophilic and hydrophobic properties,filtration performance,electret stability,tensile properties,bursting properties was tested and analyzed.Finally,the toughening mechanism of PEG toughened PLA melt-blown nonwovens is summarized.The primary conclusions of every section are as described below:(1)PEG has good compatibility with PLA,and the smaller the molecular weight,the better the compatibility.The introduction of PEG can promote the transformation from?'crystal to?crystal in PLA,at the same time,the crystallization rate of PLA was improved,and the crystallization capacity was also improved,the effect was more apparent when the PEG molecular weight was smaller.The elongation at break of PLA was also markedly increased by adding PEG,but mildly reduced the yield strength.Particularly when the molecular weight of PEG was 1000,the elongation at break of PLA/PEG-1000 blend material increased by about183%and the yield strength decreased by about 33%compared with that before modification.(2)The introduction of PEG can significantly improve the melt flow index of PLA,especially at 250?,the melt flow index of PLA/PEG-1000 blend material is 585.347g/10min.PEG also diminished the apparent viscosity,glass transition temperature and cold crystallization temperature of PLA,whereas,its thermal stability is lowered.Generally speaking,PLA and PLA/PEG blend materials have good spinnability and can meet the production requirements of melt-blown process.(3)Compared with PLA melt-blown nonwovens,fiber fineness,pore size between the fibers,porosity and air permeability of PLA/PEG melt-blown nonwovens are lower.In addition,the addition of PEG improves the hydrophilicity and filtration efficiency of PLA melt-blown nonwovens,whereas impairs the electret stability.In the aspect of mechanical properties,compared with before modification,PLA/PEG-1000 and PLA/PEG-2000 melt-blown nonwovens have more toughness.In particular,the vertical toughness of PLA/PEG-1000melt-blown nonwovens has been increased from 0.25MJ·m-3 to 0.53MJ·m-3,increasing by nearly 112%.The horizontal toughness increased from 0.18MJ·m-3 to 0.26MJ·m-3,increasing by nearly 44%.However,when the molecular weight of PEG was 4000 and 8000,the vertical and horizontal toughness was similar to that before the modification or even slightly decreased. |
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