The Effect Of PBAT On The Performances Of Stereo-Complexed Polylactide And Its Blended Fibers

Green development and green economy are the themes of the current society.In the processing and production of petroleum-based synthetic fibers,its energy consumes is high and those fibers are difficult to degrade in the natural environment,leading to the environmental problems.As the implementation policies about carbon emission peak,carbon neutrality and plastic bag ban,it is urgent to develop a new green fiber.Polylactic acid（PLA）is the main degradable material in the market.Its raw material is renewable and its products are degradable.PLA fiber has comparable mechanical properties to polyester,and it is considered as the most promising bio-based and degradable green fiber.However,PLA fiber have some defects,i.e.,poor heat resistance（easy to deform when heated）,poor hydrolysis resistance（durability is not as good as polyester）,and poor softness（high initial modulus makes the fabric uncomfortable to wear）.Compared with PLA,the thermal and hydrolytic properties of stereo-complexed polylactide（sc-PLA）and the toughness of PBAT/PLA blend are improved effectively.In order to improve the heat resistance,hydrolysis resistance and softness of PLA fiber at the same time,PBAT/sc-PLA blend fibers with good comprehensive performances were prepared by melt spinning of PBAT,PLLA and PDLA.Firstly,PBAT/PLLA/PDLA blends were prepared,where the mass ratio of PBAT was 0%to 12%and the mass ratio between PLLA and PDLA was 1:1.And its crystallization properties were studied by DSC under different isothermal crystallization temperature.The results show that blending PBAT accelerates the crystallization rate of PLLA/PDLA blends,increase the crystallinity of homogenous crystals（HC crystallization）,while reduce the crystallinity of the stereo-complexed crystals（SC crystallization）.Under the cold crystallization at 110℃,the blends have faster crystallization rate,lower HC crystallinity and higher SC crystallinity.When the crystallization temperature reaches more than 200℃,its crystallinity of SC increases obviously,and reaches complete stereo-complexation at 220℃.Subsequently,the PBAT/sc-PLA blends were obtained by PBAT/PLLA/PDLA blends crystallized at 110℃and 220℃,and the heat resistance,hydrolysis resistance and mechanical property were fully analyzed.The results show that the heat resistance of blends is greatly improved after crystallization at 220℃.But the high temperature damages the material,which seriously reduces its mechanical properties and hydrolysis resistance.After crystallization at110℃,the toughness of the blends gradually increases as the PBAT content increases,but its heat resistance and hydrolysis resistance gradually decrease.It is concluded that the blend has good heat resistance,hydrolysis resistance and toughness when the content of PBAT is 6%.Finally,the spinning properties of PLLA/PDLA blend with PBAT below 6%were studied,and the heat resistance,hydrolysis resistance and mechanical properties of PBAT/sc-PLA blended fibers were characterized.The results show that,with the increase of PBAT content,the performance trend of blended fibers is the same as that of blended materials,but the spinnability of the blended melt gradually deteriorates,and only PBAT/sc-PLA blended fibers with PBAT content of 1%,2%and 3%were prepared.Compared with PLA fiber,the heat resistance,hydrolysis resistance and flexibility of PBAT/sc-PLA blended fibers are improved.In addition,proper heat setting can increase the heat resistance and strength of fiber but reduce its softness.After heat setting at 150℃,the softening temperature,strength loss rate（after staining at 130°C）and initial modulus of blended fiber with 1%PBAT content are 104.3℃,65.1%and 41.31 c N·dtex^-1 respectively,and those performances of PLA fiber are 82.7℃,56.5%and 44.89 c N·dtex^-1 respectively.