偏氟乙烯-六氟丙烯共聚物纤维结构与性能表征

Structures and Properties of Poly(vinylidene fluoride-co-hexafluoropropylene) Fibers

采用熔融纺丝技术制备偏氟乙烯-六氟丙烯共聚物[P(VDF-HFP)]初生纤维,在90°C下分别拉伸2、4、6倍,用X射线衍射(XRD)、傅里叶红外光谱(FTIR)、热重分析(TG)、示差扫描量热分析(DSC)、拉伸试验等研究了纤维结晶、热性能、力学性能、弹性回复性能等.结果表明:P(VDF-HFP)纤维晶区主要源于偏氟乙烯(VDF)链段,具有α和β2种晶型;随着拉伸倍数的增大,α晶型转变为β晶型并逐步增加,纤维结晶度提高;拉伸倍数为6倍时,P(VDF-HFP)纤维在氮气氛围下的热分解温度为452.3°C,熔融温度为126.9°C,断裂强度为502.6 MPa,定伸长为20%时,重复拉伸50次的弹性回复率为81%.

In order to promote the development of poly（vinylidene fluoride-co-hexafluoropropylene） [P（VDF- HFP）] fibers in industry, P（VDF-HFP） fibers were fabricated via single screw melt spinning machine. The fibers were drawn by thermal stretching process, and the polyvinylidene fluoride （PVDF） fibers were prepared as a reference. The crystal structure, melting behavior and mechanical properties of the fibers were investigated by X-ray diffraction, Fourier transform infrared spectroscopy （FTIR）, differential scanning calorimetry （DSC）, thermogravimetric analysis （TG） and fiber strength test. The results revealed that the crystal morphology of fibers had a P（VDF-HFP） and β polymorphic forms, similar to PVDF fibers contributing to the regularly stacking of VDF moiety. The addition of HFP had an effect on crystallization, resulting in lower crystallinity in P（VDF-HFP） fibers. The increase of draw ratio not only facilitated the transition of crystalline phase from a to β phase, but also improved the crystallinity of the fibers. When the tensile strength was equal, a higher transformation of the crystalline form from a to ,8 phase was observed in P（VDF-HFP） fibers than that in PVDF fibers, due to the steric effect in HFP structural unit. The thermal stability of the fibers was also improved and their crystallization consummated with stretching. The melting tempera^tre and thermal decomposition temperature of P（VDF-HFP） fibers under draw ratio of 6 reached 126.9 and 452.3 ~C, respectively. With the increase of the draw ratio, the tensile strength increased owing to the regular rearrangement of the molecular chains along with the axial direction, and the optimal tensile strength of P（VDF-HFP） fibers was as high as 502.6 MPa at draw raio of 6. After repeatly stretched for 50 times under constant elongation of 20%, the elastic recovery rate of P（VDF-HFP） fibers under the draw ratio of 6 was 81%, which was much higher than that of PVDF fibers, indicating that the incorporation of the HFP segments into the PVDF molecular chains was beneficial to improvement of the flexibility of the fibers.