In order to clarify the actual circumstances of radiation-induced depolymerization of cellulose (dissolving pulps), DP distribution of cellulose trinitrates (CTN) obtained from low DP pulps by irradiation have been studied by using gel permeation chromatography (GPC).
(1) A GPC calibration curve (counts vs. DP) covering wide DP range has been able to be drawn up with the fractions of two cellulose nitrates prepared from high DP wood pulps and rayon staple fibers. Since all of the fractions are not monodisperse, this calibration curve is rather qualitative but indicates the mean values of corresponding DP against the wide count range.
(2) Low DP pulps irradiated uniformly show more uniform DP distribution than unirradiated original pulps. Moreover, DP distributions of CTN prepared from alkali cellulose (just before xanthation) and rayon staples which have been obtained from the “no-aging” viscose process of the uniformly irradiated pulps, are similar to those of corresponding CTN from the conventional process.
(3) In order to improve the uniformity of irradiation by electron beams, the use of electron filters for high voltage electron accelerator (1.7 MeV) and the application of back-scattering for low voltage electron accelerator (0.5 MeV) were studied previously, and in this investigation it has been confirmed, from DP distribution of low DP pulps obtained through above methods, that these methods are effective for the irradiation of pulps by electron beams.