METHOD OF DEPOSITING AND FUSING CHARGED POLYMER PARTICLES ON CONTINUOUS FILAMENTS

Abstract

Process for making a tow pre-preg (or tow-preg) comprising long continuous fibers coated with a thermoplastic polymer. A spread tow of long continuous fibers, preferably carbon or glass, is grounded and coated with electrostatically charged particles. The fiber diameter is about 5-50 microns and the mean particle diameter is about 0.1-40 microns. A particle laden air stream is formed by aspirating fluidized polymer particles into a flowing air stream whose velocity exceeds the settling velocity of the particles. The particles in the flowing air stream are continuously electrostatically charged by means of an applied voltage of at least about 20 kV. The flowing air stream with electrostatically charged particles suspended therein is then contacted with the continuously moving grounded spread fiber tow. The particle laden air stream is flowing downwardly and the fiber tow moving horizontally at the time of contact. The fibers with thermoplastic particles clinging thereto are continuously heated to a temperature sufficient to cause fusion of the thermoplastic polymer. This results in long continuous fibers coated with the thermoplastic polymer. The resulting tow-preg, or tow of coated fibers, is useful in the preparation of structural composites in which the fibers service reinforcing fibers. The thermoplastic coating polymer is a high performance polymer, such as thermoplastic polyimide (TPI), where high performance and the structural composite is desired. Polymer coating weights may vary from about 20% to about 90% of the total tow-preg weight.

Source: Google Patents

35 USC §181 Secrecy Order

Inventor

• 1JAMES L. THRONE

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