THE EFFECT OF LASER-RADIATION ON THE STRU CTURE, THERMAL, AND OPTICAL-PROPERTIES OF POLY(ACRYLONITRILE)

The transmitted and reflected fractions of the radiant energy density of a beam of the CO2 laser, incident onto a PAN film sample, depends o n the state of-molecular mobility initiated by the laser beam, As the intensity of the molecular motion increases, both the transmitted and reflected fractions tend to decrease, which is indicative of an increa se in the coefficient of absorption of the radiant energy in the polym er sample, The transition from continuous to pulsed irradiation regime , provided a constant average energy flux density, decreases the level of absorption, The shorter the pulse length, the greater is the reduc tion effect, Cooling the zone of laser action is also a factor decreas ing the fraction of the radiant energy absorbed, Both the transition f rom continuous to pulsed irradiation and the sample cooling during the exposure decrease the rate of energy dissipation and increase the pro bability of the energy accumulation on chemical bonds, thus stimulatin g degradation processes in laser-irradiated PAN samples.