| Popis: |
The longitudinal Poisson's ratios νlt of the crystal lattice of poly(p-phenylene terephthalamide), namely Kevlar 49 and Kevlar 29, were evaluated by X-ray diffraction. Linear contraction of the crystal lattice in the direction perpendicular to the chain axis was observed up to 800 MPa. The νlt values for the (1 0 0), (0 1 0) and (1 1 0) planes are obtained as follows: (1 0 0) v R =0.31 (0 1 0) v R =0.20 (1 1 0) v R =0.24 The small νlt value for the (0 1 0) plane is considered to correspond to the hydrogen bonds that exist in the direction perpendicular to the plane. Information on the elastic anisotropy of the crystal lattice can be obtained through this measurement. |
