Solid-state extrusion of nylons 11 and 12: processing, morphology and properties

Abstract

Monofilaments of poly(11-amino-undecanoic acid) (nylon 11), and poly(laurylactam) (nylon 12) have been produced using solid-state extrusion methods in an Instron capillary rheometer. The resulting morphology, physical and mechanical properties were investigated. For nylon 11, at an extrusion ratio (ER) of 12, the crystalline melting-point temperature increased by 16° C, over the undrawn material, while the per cent crystallinity,Xc, increased by 23%. Nylon 12, extruded to a maximum ER of 6, realized an increase inTm of 4° C at ER=5 and anXc increase of 14%. Young's modulus for nylon 11 increased from 3 GPa at an ER=3 to 5.5 GPa at an ER=7 and levelled off at greater ER. For nylon 12, the Young's modulus climbed from 2.5 GPa at ER=3 to about 3.3 GPa at E R=5.5. Conventionally melt-spun and cold-drawn nylon 11 and nylon 12 fibres exhibited Young's modulus values of 2.7 GPa and 2.9 GPa respectively. Atmospheric moisture loss was found not to affect solid-state extrusion of these higher nylons. Increases in extrusion temperature and/or pressure increased the extrusion rate. The flow activation energy of nylon 11 was 73 kcal mol−1 at 0.24 GPa extrusion pressure, and 124 kcal mol−1 at 0.49 GPa extrusion pressure. Calculated apparent viscosities were about 1014 poise and 1015 poise, respectively. The morphologies were shown by electron microscopy to be microfibrillar and the resulting monofilaments were transparent to visible light.