SynopsisRadicals produced in Co60 irradiated normal and l,l&-polypropylene have been examined by electron spin resonance. It is concluded that 80% of the radicals are -CH2--CH(CH, )-and 20'33 are -CH2-C(CH1)-CH2in both atactic and isotactic polymer. In the isotactic, but not in the atactic material, the primary radical disappears much faster than the secondary one when heated. Interpretation of the spectra of polybutylene and polyisobutylene is also given.

Polyethylene was irradiated in vacuo at liquid nitrogen temperature and allowed to warm up. The concentration of free radicals, as observed by electron spin resonance (ESR) spectroscopy, decays very quickly to a relatively stable value which is temperature dependent. This behavior is interpreted to mean that these reactive radicals are relatively close to one another as opposed to random distribution. The cold‐irradiated sample was exposed to air, and the formation of the peroxy radical was observed at −80°C. Only 40–45% of the radicals reacted. This was interpreted to mean that 90–95% of the radicals trapped at −195°C. are in the amorphous phase

With the increased use of high-speed gel-permeation chromatographs (GPC) interfaced with mini-computers for quick communication of results, it is desirable to use a rapid reliable method of calibration. Consider a set of columns with an appropriate distribution of pores over the desired range such that the calibration curve may be described aswhere V is the elution count, C1 and C2 are constants, and M is the molecular weight. If we have a standard polymer with a broad distribution of molecular weights over the range of interest, and the weight-average and number-average molecular weights, aw and a,,, have been accurately determined by such methods as liiht scattering and osmometry, it is a simple matter to write a computer program to calculate the linear constants.From the definitions:where w is the weight fraction, it is trivial to show that:We calculate eq. (1) 36 times to find a unique C2 to the nearest 5 2 0 . The fact that the above expression is independent of C1 allows a simpler and faster calculation of C1 and C2 than the twovariable iteration method.' From an arbitrary C1 a final C1 is obtained by iterating the expression (usually twice): until This method can be extremely useful for polymer systems where narrow fraction standards are not available.

No abstract

No abstract