Study of β relaxation in polypropylene fibres modified by several techniques

Polypropylene fibres prepared from polypropylene (PP) blended with 8 wt% of an ethylene aminoalkylacrylate copolymer were studied by means of ¹H nuclear magnetic resonance (NMR) and dynamic mechanical techniques. Measurements were carried out on the fibres spun at the spinning speeds 400 and 1200 m.min⁻¹ and then drawn to the draw ratio λ = 3.5. Spin ‐ lattice relaxation time T₁ and storage E' and loss E'' components of a dynamic mechanical modulus were measured in the temperature region of the glass transition. Broad line NMR spectra were detected at 313 K. The experimental results show that drawing of the fibres prepared at both spinning speeds results in a restriction of the molecular motion. Simultaneously with the restriction, a chain mobility enhancement was observed in noncrystalline regions of the fibres. Similar effects were induced also by rising the spinning speed. Reasons for this behavior are discussed in the paper.