| At present, the most raw materials for melt-blown nonwoven fabric are polyethylene terephthalate(PET), polypropylene(PP). As air filtration material, especially the disposable air filtration material, it faces difficult to clean, difficult recovery, easy to produce secondary pollution and many other problems, so green, environmentally friendly, fully biodegradable materials has appeal more and more attention from researchers. Poly(lactic acid)(PLA) and its products have won the world’s attention and favor due to its excellent performance, a wide range of applications, significant environmental and social benefits. Unfortunately, the application in the field of high efficiency filter of PLA has been limited because of its brittleness, low elongation at break, defects and poor flexibility. Poly(ε-caprolactone)(PCL) is a kind of fully biodegradable material like the PLA, and also is a semi-crystalline material, the glass transition temperature is about-60℃, at room temperature was rubbery, has good toughness, commonly blends with PLA to improve its brittleness. But the macroscopic phase separation between the PLA and PCL is obvious, toughening effect of PCL is not fully reflected, so we choose PLA-PCL-PLA as the phase compatibilizer of PCL and PLA, which has same molecular structure with PLA.In this paper, PLA-PCL-PLA was prepared by ring-opening polymerization, molecular structure, thermal properties and molecular weight of the PLA-PCL-PLA were researched by 1H-NMR, FTIR, TG and DSC and Ubbelohde viscometer method, PLA/PCL and PLA/PCL/PLA-PCL-PLA blends was prepared by method of melt blending, and the thermal properties, crystallization behavior, phase distribution and mechanical properties were studied. At the same time the rheological properties and spinnability of blending materials were analyzed. Finally, the influence of PLA-PCL-PLA to PLA/PCL blends melt-blown nonwovens on crystallization, fiber diameter distribution, pore size distribution and filtration resistance and mechanical properties was studied. The results were shown as follows:The analysis of 1H-NMR, FTIR showed that the ring opening polymerization reaction taking place between PLA and PCL generated the PLA-PCL-PLA triblock copolymer; There were two different decomposition temperatures in TGA curves, respectively represent the decomposition of PLA and PCL macromolecular segments and thermal stability decreased with LA increased; DSC showed that when the segmented was the amorphous PDLLA, triblock copolymer only have the melting peak of PCL, and when the segmented was PLLA, there are two melting peaks which refer to PLA and PCL. Ubbelohde viscometer showed that molecular weight increased with the increased of monomer content.With PLA-PCL-PLA increased, thermal stability of PLA/PCL blends was improved, the glass transition temperature of raw material PLA and PCL occurred relative movement, indicating that PLA-PCL-PLA had played a very good compatibility modification effect, the molecular weight of PLA-PCL-PLA have no effect on the thermal stability of PLA/PCL blends, but compared with other molecular weight, the viscosity-average molecular weight of the PLA-PCL-PLA was 3.84 × 104, glass transition temperature of the blending materials close to the largest degree.After the modification of PLA-PCL-PLA, the crystal type of PLA / PCL blend material did not change, but the two-phase interface becomes blurred, phase distribution size decreases, and dispersion evenness increased, embodies the good capacity of PLA-PCL-PLA. When the PLA-PCL-PLA content increased to 0.24%, the elongation at break of the blending material increased from 5.2% to 11.8%, when the PLA-PCL-PLA copolymer molecular weight was 3.84 × 104, found that PLA / PCL blends breaking elongation of the material was further increased to 12.7%.The melt index of PLA/PCL/PLA-PCL-PLA was higher than PLA/PCL blend material, showed the good liquidity, the apparent viscosity and viscous flow activation energy decreased with the increased of shear rate and the the rise of temperature. Compared to the meltblown material, the crystallinity of the resulting meltblown nonwoven material was improved; with the increase of content of PLA-PCL-PLA, meltblown fiber diameter increased, but when changing its molecular weight, fiber diameter, permeability and filtration efficiency of the material changed little. The addition of PLA-PCL-PLA copolymer had little effect on the tensile strength of the fiber material, but had a great influence on the elongation at break. |
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