The amorphous orientation of linear polyethylene (PE) was investigated by a dye dichroism method using a fluorescent dye, Whitex. Inflation films of linear PE (Sholex-6000) were drawn in hot water at 60°C and then dyed for the subsequent measurement of dichroism. The value of φ
D, defined by φ
D=(
D_??_-
D⊥)/(
D_??_+2
D⊥), were determined for the samples drawn to various ratios, and compared with the amorphous orientation factor
fa derived from the birefringence and the crystalline orientation factor
fg determined by X-ray method.
In the relatively lower range of draw ratio, the φ
D agrees well with
fa, i.e.,
fa≅φ
D. Thus the dicroism orientation factor
fD defined by
fD=φ
D/φ
D° can be obtained by putting φ
D°=1, where φ
D° is the value of φ
D coresponding to the perfectly uniaxial orientation. In the case of highly drawn specimen, the relation between φ
D and
fa differs from that obtained in the lower draw ratio.
This indicates that the does dichroism dres not reflect precisely the orientation behavior of the amorphous region in the highly drawn specimen, suggesting that the sites of dye absorption are not only in the amorphous region but also on the surface of fibrils resulted from the higher drawing.
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