The mechanical behavior of semicrystalline Nylon 11 was studied at strain r
ates between 10(-3) and 8800 s(-1). X-ray diffraction and DSC were employed
to examine the crystal structure and the crystallinity content. The as-rec
eived material comprised a mixed structure of a predominately triclinic (a)
form. DSC revealed that the material gave rise to two melting peaks. The c
ompressive flow stress of Nylon 11 experienced a large increase at 1200 s(-
1) and decreased at higher strain rates. The maximum level of the flow stre
ss corresponded with a higher level of crystallinity and a structure mainly
of a pseudohexagonal form. The subsequent drop in stress at higher rates w
as associated with a decrease in the crystallinity content and a mixed crys
tal structure, different from that observed in the as-received material. Af
ter compression, the low melting peak disappeared and the material melted o
ver an increased temperature range. (C) 2001 John Wiley & Sons, Inc.