气相生长碳纤维填充聚苯乙烯的熔体动态流变行为

DYNAMIC RHEOLOGY OF VAPOR GROWN CARBON NANOFIBER FILLED POLYSTYRENE MELTS

采用修正的两相模型讨论加工条件对不同体积分数(φ=0～0.05)气相纳米碳纤维(VGCF)填充聚苯乙烯(PS)熔体(200℃)频率(ω)依赖性动态流变的影响.与弱剪切条件(190℃;30 r/min-5 min)下所制备的材料相比,VGCF在强剪切条件(190℃;120 r/min-10 min)下所制备材料中分散均匀,"粒子相"应变放大因子Af(φ)较低,而松弛指数n较高.将应变(γ)依赖性G″(ω,φ)应变放大因子Af(φ,γ)与"粒子相"特征模量Gf'(φ,γc),Gf″(φ,γc)引入两相模型,讨论加工条件对γ依赖性非线性流变行为的影响.研究结果表明,两相模型可定量讨论填充熔体动态流变行为.加工条件影响VGCF在基体中的分散性,但不影响"粒子相"弹性贡献Rf'(φ)与n的关系、Gf'(φ,γc)与非线性应变幂律指数x的关系以及Gf″(φ,γc)与非线性应变幂律指数y的关系,说明"粒子相"对填充熔体黏弹性的贡献与其弛豫特性及结构稳定性密切相关。

Influence of processing conditions on frequency（ω）-dependent dynamic rheology of vapor grown carbon nanofiber（VGCF） filled polystyrene（PS） melt（200℃） with different VGCF volume fractions（φ=0-0.05） was studied in the framework of a modified two phase model.In comparison with the composites processed in a strong-shear mixing condition（190℃;120 r/min-10 min）,VGCF formed aggregates to a higher degree in those processed in a weak-shear mixing condition（190℃;30 r/min-5 min）.The filler aggregation was characterized by a higher value of strain amplification factor Af（φ） and a smaller relaxation exponent n related to the ＂filler phase＂.Furthermore,strain（γ）-dependent amplification factor,Af（φ,γ）,and characteristic elastic and viscous moduli,G′ f（φ,γc） and G″ f（φ,γc）,were introduced to the two phase model for discussing the nonlinear rheology with increasing γ.The results showed that the two phase model allowed discussing dynamic rheology of filled melts qualitatively.The processing condition influenced the dispersion of VGCF in the matrix while it did not influence relationships of elastic contribution R′ f（φ） against n for ω-dependent rheology as well as elastic modulus G′ f（φ,γc） against nonlinear strain exponent x and viscous modulus G″ f（φ,γc） against nonlinear strain exponent y,suggesting that the viscoelastic contribution of the ＂filler phase＂ was closely related to its relaxation and structural stability.