高密度ポリエチレンの分子量分布とレオロジー
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概要
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High density polyethylene (HDPE) has each its distinctive features in the rheological properties according to its manufacturing process. The present work proposes to present a quantitative relationship between its molecular weight distribution and the melt viscoelastic properties for some samples of HDPE. The samples have been fractionated by both the elution column technique and the precipitation technique. The number-average, weight-average and Z-average molecular weights have been calculated from the smoothed molecular weight distribution curve for each sample by the method of summation. The viscoelastic properties of some series of the commercial HDPE have been measured by means of a concentric cylinder type rheometer at different temperatures (150〜230℃). The angular frequency (ω) ranges from about 10_<-2> to 50 sec^<-1>. The ratio of flow rate at shear stress 10^6 dyne/cm^2 to at 10^5 dyne/cm^2 (=flow ratio ; FR), which gives a good indication of the non-Newtonian property of samples, have been measured by means of a melt indexer type rheometer. The results are as follows ; (1) The liner relationship is found between M_w/M_n and M_z/M_w, not to M_z/M_w for only a series of samples made by the same manufacturing process. (2) FR is found to be related to M_z/M_w, no to M_w/M_n. log FR=0.317 M_z/M_w+1.04 (3) Dynamic viscosity (η') and dynamic regidity (G') can be superposed according to the temperature-time superposition principle, and shift factors a_T from η' and G' are practically the same. Agreement with constancy of shift factor for various molecular weights (M_v=5〜10×10^4) and distributions is good, and the apparent activation energy (ΔH_a) calculated from the shift factor is 6-7 kcal/mol. ΔH_a of copolymer is also of the same value. (4) master curves also are constructed with respect to the molecular weight for measurements of η' and G' are the same. the relationship must also be right in the steady flow viscosity, and confirms that HDPE with The relationship must also be right in the steady flow viscosity, and confirms that HDPE with the same M_z/M_w have equal FR. (5) The relationship between η_0 and M_w is effected by the molecular weight distribution. log η_0=3.5 logM_w+log(M_z/M_w)-12.7.
- 社団法人日本材料学会の論文
- 1966-05-15