Temperature characteristics of dynamic modulus
E′, and dynamic loss
E″, of polypropylene (PP) monofilament grafted with acrylic acid and further treated with metallic salts or tris (1-aziridinyl) phosphine oxide (APO) were measured using the direct-reading dynamic viscoelastometer at 110 c. p. s. over a temperature range from-20°C to 200°C.
Primary peak in the low temperature side of PP (
da), obtained from the temperature characteristic of
E″, tends to shift to higher temperature side and to decrease its intensity by the grafting with acrylic acid. These tendencies may be caused by the increased restriction of molecular chains of PP in the amorphous region by some crosslinking action of the dimesized polyacrylic acid chains of the grafted branches. The crystalline absorption (
dc) of PP in the high temperature side (110°C) is broadened for the samples with a low degree of grafting due to the superposition of the glass transition of polyacrylic acid and of the
dc transition of PP, but new well-defined absorption peak is appeared at 140°C for the samples with a high degree of grafting. The location of this higher temperature absorption, 140°C, is in accordance with the glass transition temperature of polyacrylic acid anhydride.
The
dc-absorption tends to shift to higehr temperature side and the intensities of both
da-and
dc-absorptions tend to decrease for the grafted samples treated with metallic salts in order to convert the carboxylic groups in the grafted chains to salt-forms, and the peak characteristic of the glass transition temperature of polyacrylic acid anhydride is almost disappeared with these samples. The
E′ of these grafted and treated samples shows remarkable decrease in the vicinity of the temperature of the melt-dispersion of PP, though somewhat increased by the grafting and the treatment with metallic salts below this temperature.
As for the treatment with APO, which may be expected to form crosslinking by covalent bond in the grafted material, higher
E′ value is observed for the 36.9% acrylic acid grafted
PP than that of the grafted PP untreated or treated with metallic salts even at the temperature as high as 200°C beyond the melt-dispersion temperature of PP.
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