Use of the frequency dependence of the impedance to monitor viscosity during cure

Abstract

The ability to conveniently and continuously measure the processing properties of polymer resins is important both to the resin supplier and to the fabricator. Frequency dependent electromagnetic sensors (FDEMS) provide an in‐situ technique for continuous measurement of the resin's rheological changes both in a laboratory press and in manufacturing tools in an autoclave. In this paper the frequency dependence of ϵ*(w) is used to quantitatively monitor the viscosity for a tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) amine epoxy, to quantitatively monitor the viscosity during processing In a styrene‐polyester resin, and to monitor the cure process in an autoclave during cure of a high temperature polyimide‐graphite prepreg. In addition, the technique is used to measure the viscosity at various ply positions in a thick TGDDM graphite epoxy laminate during processing in an autoclave.

Evolution of ion mobility in cured epoxy-amine system as determined by time-of-flight method

“…These processes are accompanation of properties, making them one of the most nied by changes of the physical properties of the important polymer groups that have a wide range system connected with phase transitions: gelation of applications where a high performance in terms and/or vitrification. An important problem is the of resistance to chemical, mechanical, and electridetermination of the viscosity of the reacting system in situ, as a function of curing time and tem-In recent years, electrical techniques, like mi-measurements of the evolution of ionic mobility in a course of resin curing by means of the timecrodielectrometry, [1][2][3][4][5][6][7] have attracted increasing of-flight (TOF) method. interest because they allow continuous monitoring of the advancement of reaction of the curing resin in a nondestructive way.…”

Cure monitoring via different techniques: Isothermal cure of an epoxy-novolac molding compound

“…It has been clearly established [13, 18-2l] that ionic conductivity (which may be extracted from Equation 5 when ionic conductivity dominates the dielectric response) can be used as a useful index for the progress of cure. It has also been previously suggested [ 18,[22][23][24][25]] that values of Cr or "t, which correspond respectively to the far intercept of the arc with c Log wr the e'-axis or tile reciprocal of the angular frequency at the maximum of the arc, may be adopted to represent the progress of cure. In the present case, these approaches are definitely inapplicable in the early stage of cure and may subject to significant experimental uncertainties even in the later stage.…”

Dielectric monitoring of curing process for some epoxide-amine thermosets

“…This technique enables monitoring of changes in molecular and ionic mobility during the reaction, through real-time measurement of complex electric permittivity e as a function of temperature and frequency. The works of Senturia and Sheppard [5] and Kranbuehl with co-workers [6] have shown direct value of this technique applied to commercially developed systems.…”