异相成核和拉伸诱导对生物基PHBV复合纤维结晶结构与力学性能的影响

采用熔融纺丝法制备了聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)/二硫化钨(WS_2)复合纤维.利用示差扫描量热仪(DSC)、热台偏光显微镜、二维广角射线衍射仪(2D-WXRD)、纤维强力仪研究了WS_2异相成核作用和牵伸诱导作用对纤维的结晶结构和力学性能的影响.研究表明,WS_2显著提高了PHBV的结晶温度,当使用2 wt%WS_2时,复合材料的结晶温度提高到115~130oC,比纯PHBV(99~105oC)提高了约25oC.WS_2不仅没有影响PHBV球晶的径向生长速率,且明显提高了PHBV/WS_2复合材料的晶核密度,熔体成核活性Φ由1.0降低为0.49.随着牵伸倍率和WS_2用量的增加,纤维的拉伸强度呈现出先增加后减小的趋势.当添加1 wt%WS_2并采用单向牵伸3.8倍时,纤维中的晶体取向产生了β晶结构,使复合纤维的拉伸强度由纯PHBV的37 MPa提高至155 MPa,断裂伸长率由2.4%增加至45%.

Enhanced Mechanical Properties of Melt-spun Bio-based PHBV Fibers:Effect of Heterogeneous Nucleation and Drawing Process

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV),a biodegradable bio-based polyester,has a limited application in fibers because of its slow crystallization rate and large spherulite size.Therefore,the key to expand applications of PHBV fibers is to control its crystallization behavior.In consideration that the characteristics of the original bio-based materials PHBV will be changed after chemical modification,nano-hybrid technology is applied in this study to regulate heterogeneous nucleation behavior of PHBV after introducing nano-tungsten sulfide into PHBV system.In addition,drawing induced during melt crystallization process tends to change the crystalline structure of the polymers and thus to change the mechanical properties of PHBV fibers.Hence,effects of heterogeneous nucleation and draft induction on the crystal structure and the mechanical properties of the fibers were studied in this paper via differential scanning calorimeter (DSC),polarizing microscope (POM) equipped with hot stage,two-dimensional wide-angle X-ray diffraction (2D-WXRD) and fiber strength tester.It was found that the crystallization temperature of PHBV increased obviously with the induction of WS2 nanoparticle.When the content of WS2 was 2 wt％,the crystallization temperature of the composite materials increased to 115-130 ℃,about 25 ℃ higher than that of neat PHBV.When WS2 component was induced,the nucleation density of PHBV/WS2 composite materials was enhanced significantly and the nucleation activity Φ of the resultant composite decreased from 1.0 to 0.49 without influencing the radial growth rate of PHBV spherulites.With the increase in draft rate and WS2 content,the tensile strength of fibers increased first and then decreased.When the addition of WS2 content was 1 wt％ and a uniaxial draw of 3.8 times was adapted,the crystal orientation of the fibers was enhanced,and the β-form crystal structure was produced,and thus the tensile strength of composite fibers increased from 37 MPa for pure PHBV to 155 MPa and the elongation at break increased from 2.4％ to 45％.