β相聚偏氟乙烯基铁电微制件注塑成型的基础问题研究

β-phase PVDF-based ferroelectric microparts show their importance and prospects of wide spread use in the field of MEMS. So far, it is still a challenging and important research subject for mass production of β-phase PVDF-based ferroelectric microparts. Therefore, this project presents a new approach to achieve mass production of β-phase PVDF-based ferroelectric microparts using microinjection molding technology on the basis of the molecular chain orientation/filling synergistic effect of the PVDF-based nanocomposites with multi-field coupling. At the theoretical level, this project will focus on the following issues: melt rheology and non-isothermal crystallization behavior of PVDF/nanoclay (cobalt-ferrite nanoparticles) composites; formation and development mechanisms of the composites morphology and structure under the condition of multi-field coupling during microinjection molding; mechanism and key influencing factors of molecular chain orientation/filling synergistic effect on inducing the formation of β-phase during microinjection molding; relationship of morphology/structure and ferroelectric property for the microparts. At the technical level, key processing parameters and material formulas for molding β-phase PVDF-based microparts with good ferroelectric property will be investigated. The investigation results from the present project will provide theoretical basis and key technology for mass production of β-phase PVDF-based ferroelectric microparts with low cost and widen their application area.

β相PVDF基铁电微制件在MEMS领域具有广阔的应用前景和重要的地位。目前，批量化制备β相PVDF基铁电微制件仍是具有挑战性和战略意义的研究课题。为此，本项目提出基于多物理场耦合条件下PVDF基纳米复合材料分子链取向/填充协同效应的思想，利用微注塑成型技术批量成型β相PVDF基铁电微制件的新方法。在理论层面，研究PVDF/纳米粘土（纳米铁酸钴）复合材料的熔体流变性能及非等温结晶行为；揭示微注塑成型过程中复杂多物理场耦合作用下复合材料形态结构的形成和演变机理；探究在微注塑成型过程中分子链取向/填充协同诱导β相形成的机理及其关键影响因素；分析微制件形态结构与铁电性能间的内在联系。在技术层面，探究成型铁电性能良好的β相PVDF基微制件的关键工艺参数和材料配方。本项目研究结果将为大规模、低成本地制备β相PVDF基铁电微制件及拓宽其应用范围提供理论基础和关键技术。

在项目实际执行期间，制备了多种PVDF基纳米复合材料，并对它们的流变性能和非等温结晶行为进行了系统的研究。结果表明，纳米填料提高了PVDF熔体的黏度，并在结晶过程中促进PVDF形成α相。借助模压成型研究、阐明了应力场和温度场作用下PVDF基微制件中形态结构的形成机理。进一步研究了微制件的介电性能及导热性能与微观结构的内在联系，并据此构建了高导热、高介电常数和低损耗的PVDF基介电微制件的制备方法。在项目研究中取得一定成果的同时，也发掘新的问题：（1）纳米填料或低聚物对PVDF熔体增塑作用及其机理；（2）纳米填料或低聚物表面性质对PVDF熔体形成长反式序列及其稳定性的影响机制。凝练出的新问题为今后继续执行本项目的研究工作指明了方向。