Dynamic dielectric analysis (DDA) has been used to study curing polymer systems and thermoplastics. Measurements have been made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity ε*, specific conductivity σ(ohm−1 cm−1), and the relaxation time τ, parameters which are characteristic of the cure state of the material and independent of the size of the sample. Dynamic dielectric measurements have been used to monitor polymer processing in UDEL‐P1700, LARC‐160, polyphenyl quinoxaline (PPQ), and Epon 828 cured with Agent U. Dynamic dielectric measurements have been correlated with viscosity for the polysulfone thermoplastic UDEL‐P1700 and with viscosity and ultrasonic measurements on the DGEBA type epoxy Epon 828 cured with Agent U. The experimental results suggest that when ionic processes dominate the dielectric response, the intensive property σ is a good monitor of the resin's viscosity. The results show that the dielectric relaxation time τ can be used to monitor the state of the system and the extent and rate of the reaction. Solvent evolution can also be easily observed.

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synopsisThe polyimide resin LARC-160 was prepared from diethyl-3,3',4,4'-benzophenone tetracarboxylate (BTDE). ethyl-5-norbornene-2,3-dicarboxylate (NE), and Jeffamine AP-22. The imidization reactions of and BTDE were studied by HPLC, 13C-NMR, and I R NE imidizes slowly at 1 2 O C ; BTDE imidizes when the resin is heated above 100°C. Both imidization reactions proceed directly to the imide. Neither amic acid is present in significant quantities a t any stage of the imidization reactions. The monomer mixture has been stored at 12°C for periods up to 14 months. The effects of resin aging a t this temperature on the chemical composition of the resin monomer mixture and the imidized polymer formed on curing were investigated. Aging the resin monomer mixture has the effect of partially advancing the imidization reaction. Aging also results in the formation of slightly higher-molecular-weight polyimide chains after curing of the resin at 140 and L1W0C.Bisnadimide (BNI) is observed as a major reaction product, regardless of resin age.