The rate mechanism of crystal plasticity was studied in quasi-single c
rystalline (QSC) Nylon 6 prepared by plane strain compression in a cha
nnel die to equivalent extensional strains on the order of 1.39. Speci
mens of such highly oriented material were probed in simple shear expe
riments on the (001)[010] and (100)[010] monoclinic chain slip systems
by means of strain rate change experiments in the temperature range o
f 255-366 K. These experiments demonstrated that while there is a well
developed glass transition in the shear moduli of the material there
is no corresponding transition in the plastic resistances, indicating
that the plastic behavior of the QSC material is derived entirely from
the crystalline component. Analysis of the experiments with reference
to dislocation mechanics has disclosed that the plastic shear resista
nce for the chain slip systems is made up of several components. These
include an athermal component due to random internal stresses of misf
it, a lattice resistance, most probably affecting only the screw dislo
cations, and a terminal nonhardening flow resistance due to close rang
e interaction of these dislocations with a family of small crystalline
packing imperfections such as chain crossovers, slack pockets, etc. A
ctivation analysis has indicated that the activation volumes Delta ups
ilon() governing this interaction are linearly dependent on stress, r
esulting at zero stress in Delta upsilon() = 6 x 10(-21) cm(3) for th
e (001)[010] chain slip system and 2.73 X 10(-21) cm(3) for the (100)[
010] chain slip system. Moreover, from the stress level where the acti
vation volume vanishes athermal overall shear resistances of 8.2 % and
14.2% of the respective shear moduli of the (001)[010] and (100)[010]
slip systems are obtained respectively. Experiments were also carried
out on untextured Nylon 6 for purposes of comparison. These gave resu
lts intermediate to those of the chain slip systems.