Nylon–selected topics

Abstract

ABSTRACT:Elements of the technology of nylon fibers and nylon plastics are reviewed. These include the development of equations to quantify the effects of endgroup imbalance and chain-ending impurities, the kinetics of the polymerization of caprolactam, the solid-state polymerization of nylon-66, and the dependence of fiber tensile strength on molecular weight. This is followed by remarks that include comments on the significance of the amidation equilibrium for melt behavior and estimates of the activation energy of viscous flow, the pyrolysis of nylon, the use of the glass-transition temperature (T g ) to predict the effect of moisture on properties, and the prospect for new nylons.

Step Polymerization

“…7). Poly(hexamethylene adipamde) [IUPAC: poly(iminohexanedioyliminohexane-1,6-diyl) or poly(iminoadipoyliminohexane-1,6-diyl)], also referred to as nylon 6/6, is synthesized from hexamethylene diamine and adipic acid [Zimmerman, 1988;Zimmerman and Kohan, 2001]. A stoichiometric balance of amine and carboxyl groups is readily obtained by the preliminary formation of a 1 : 1 ammonium salt (XIII) in aqueous solution at a concentration of 50%.…”

A comprehensive single‐particle model for solid‐state polymerization of poly(L‐lactic acid)

“…According to the Flory theory, the kinetics models describe propagating reaction kinetics of second order, assuming equal reactivities of the functional end groups, for reversible SSP reactions. Power law models basically correlate the rheological properties with the MW buildup during SSP 25…”

“…Power law models basically correlate the rheological properties with the MW buildup during SSP. 25 SSP is a step growth polycondensation process, in which the terminal end groups of the growing polymer chains, react with each other, to form much longer chain molecules, with simultaneous removal of byproducts such as water. In addition, other effects occur simultaneously: these include (1) significant decrease in diffusivities of reactive end groups of polymer chains and of reaction byproducts, due to decrease in chain mobility, caused by MW and crystallinity (X c ) increase; and (2) although end-groups are consumed during SSP, this decrease in their effective concentrations in the amorphous region is countered by the decrease in the amorphous volume fraction, because crystallization occurs during SSP.…”

Polyamide solid state polymerization: Evaluation of pertinent kinetic models

“…Higher molecular weights may be reached through solid state polymerization (SSP) at temperatures between the glass transition and the onset of melting 3–11. Polycondensation progresses through chain‐end reactions in the amorphous phase of semicrystalline polymers,12, 13 which in most cases are flakes or powder. Reaction byproducts are removed by the application of vacuum or by the passage of an inert gas through the polymer 8, 10…”

“…The SSP kinetic models may be transformed to take into consideration the two‐phase model, as suggested by Zimmerman 12, 13. The end groups and low‐molecular‐weight substances (condensate and oligomers) are exclusively in the amorphous regions, in which the equilibrium is the same as that for a completely amorphous or molten polymer at the same temperature.…”