Acetylene-terminated isoimide

This work discusses the thermal crosslinking and isomerization reactions occurring in the acetylene terminated isoimide prepolymer Thermid IP600. The techniques of Fourier Transform Infrared Spectrometry and Differential Scanning Calorimetry are used to determine the contribution of these two reactions during the thermal cure including their kinetics at 183° C. 

Structure of Thermid IP-600 Acetylene Terminated Isoimide Oligomer. 

Films of the polyisoimides were cast from DMAC at 55 °C under reduced pressure (0.1 mm). A study of the isomerization reaction was conducted by FTIR and showed that the isomerization began at approximately 100 °C and was complete after 3 h at 250 °C. In all cases the thermally treated films were insoluble in all solvents tested. Composite films were produced with XVII and three commercial matrix systems a polyarylsulfone (Radel), a polysulfone (Udel), and an acetylene terminated isoimide thermosetting resin (IP-600). Films of the matrix and XVII were cast from DMAC. Slightly cloudy films, indicating some phase separation, resulted with both the Radel and Udel systems. Composite films cast with IP-600, however, were completely clear and showed no signs of phase separation. The structural similarity of the IP-600 resin and XVII may account for the greater homogeneity of the system. Property assessment of these films before and after thermal treatment is currently underway. 

Researchers at IBM Research Center, San Jose, CA, particularly Dr. D. Y. Yoon, have done extensive work with the polyamic acid and polyimide from the reaction of pyromellitic dianhydride and 4,4 -oxydianiline. In private communication. Dr. Yoon reported that the thermally cyclodehydrated polyimide contained 4% isoimide as evidenced by ESCA (Electron Spectroscopy for Chemical Analysis). Dr. Fred Hedberg, AFWAL, Dayton, OH, is using Fourier Transform Infrared Spectroscopy (FTIR) to determine residual isoimide content in the thermally cured product from an acetylene-terminated isoimide oligomer. Dr. Hedberg reported in private communication that the major isoimide band is in the 929-936 cm region. Unfortunately, there are other weak bands in the IR spectra of polyimides which interfere with the isoimide band. The IR spectra of thermally cured polyimides from 3,3, 4,4 -benzophenonetetracarboxylie acid dianhydr ide exhibited... 

THERMID IP-600 National Starch Acetylene-terminated isoimide solution. 

By thermally induced isomerization of an isoimide to an imide, a series of molecular composites with polyarylsulfone, polysulfone and an acetylene terminated isoimide thermosetting resin were obtained [37]. After two flexible polymeric compounds were blended in solution, films were cast and the isomerization process was carried out. The thermally treated films were insoluble and showed no sign of phase separation. 

Acetylene terminated polyimide prepolymers have many advantages over conventional polyimides in the areas of processing and solvent resistance. In addition, the presence of the isoimide structure further extends the the utility of these systems by modification of the solubility properties and glass transition temperature. 

Acetylene-terminated oligomers, incorporation of isoimide functionality, 462 Acid functionalities, block copolymers, 258... 

Figure 19 Acetylene-terminated polyimide precursors synthesised by reacting BTDA 18 with less than the stoichiometric balance of 3,3 -(l,3-phenylenedioxy) bisbenzeneamine 44 and the complement to stoichiometry of 3-ethynylbenzeneamine 45 as end-capping agent. Low molecular weight polyamic acid 46 is then chanically cyclised to poly(isoimide) 47 or thermally cyclodehydrated to give polyimide 48.

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