Measurement of the friction coefficient of a fluctuating contact line using an AFM-based dual-mode mechanical resonator

A dual-mode mechanical resonator using an atomic force microscope （AFM） as a force sensor is developed. The resonator consists of a long vertical glass fiber with one end glued onto a rectangular cantilever beam and the other end immersed through a liquid-air interface. By measuring the resonant spectrum of the modified AFM cantilever, one is able to accurately determine the longitudinal friction coefficient ξv along the fiber axis associated with the vertical oscillation of the hanging fiber and the traversal friction coefficient ξh perpendicular to the fiber axis associated with the horizontal swing of the fiber around its joint with the cantilever. The technique is tested by measurement of the friction coefficient of a fluctuating （and slipping） contact line between the glass fiber and the liquid interface. The experiment verifies the theory and demonstrates its applications. The dual-mode mechanical resonator provides a powerful tool for the study of the contact line dynamics and the rheological property of anisotropic fluids.     

通过高速挤出制备高性能PBS/PETG共混材料

通过高速挤出技术制备了高性能聚丁二酸丁二醇(PBS)/聚(乙二醇-co-环己烷-1, 4-二甲醇对苯二酸酯)(PETG)共混材料,研究了不同PETG含量和不同螺杆转速对共混材料相区尺寸和性能的影响.研究发现PETG质量分数存在一个最佳用量:即为20%时,随着转速的提高PETG分散相相尺寸从最初的2.27μm逐渐降低到0.89μm.与此同时,共混材料的屈服强度从最初的26.2 MPa增加到33.4 MPa,提高了27.5%.断裂伸长率也从最初的13.3%提高到133.3%,实现了从脆性断裂到韧性断裂的转变.而当PETG的质量分数为10%或30%时,提高转速对PETG分散相的相尺寸减少不多,对共混材料力学性能有一定提升.最佳用量的存在表明高速挤出引起的相区尺寸减少是一个破碎与聚并动态平衡的过程.将不同的组成和加工的转速下获得的共混物的屈服强度与分散尺寸作图,发现它们成近似的反比关系,进一步证明PETG减小分散相相尺寸对共混材料性能提升的重要性.