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SynopsisBoric acid does not introduce crosslinks in poly(viny1 alcohol) solutions, but gelation does occur in the presence of cations. In this experimental study, the dynamic mechanical properties of these gels were determined using test-tube torsion pendulums and an air-bearing torsion pendulum. The modulus at a fixed concentration of polymer and boric acid increases with increasing sodium ion concentration up to the point where the atom ratio of sodium to boron reaches 1. Higher sodium concentrations do not increase the modulus. The log decrement, on the other hand, decreases with increasing sodium concentration continuously without reaching a plateau at the equal atom ratio. Log decrements as low as 0.02 can be measured. The storage modulus depends on the logarithm of borate concentration and on the 4.7 power of poly(viny1 alcohol) concentration. Only a very small portion of the borates in solution take part in effective crossliks. The activation energy for breaking individual bonds is a function of temperature and the cation to boron ratios. At a fixed cation concentration, this activation energy is more negative with increasing amount of boron ions due to a transformation of monomeric crosslinks into polymeric crosslinks, so that the storage modulus which measures crosslink density decreases as a temperature rises.

The free‐radical polymerization of phenylacetylene initiated by azobisisobutyronitrile at 50°C was studied in bulk and in the presence of benzene and toluene. The polymerization rate is approximately first‐order with respect to the initiator concentration. The number‐average molecular weight of the polymer is independent of the initiator concentration in bulk and is approximately proportional to the monomer concentration in the presence of the two diluents, but independent of their nature. The data are consistent with a mechanism based on first‐order decay of active to inactive radicals. This step appears to exert the major control over kinetic and molecular chain lengths. Chain transfer to the monomer is concluded to be absent or to make only a small contribution to molecular termination.

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Pyrolysis and regeneration kinetics of 1 1 spent activated carbons were studied using a thermal balance and a fludized bed reactor. The adsorbates were aromatic compounds with different types and number of side groups, and most of the side groups were lost on pyrolysis, leaving a residue about equal to the weight of the aromatic portion of the adsorbate. The residues from alkyl phenols reacted with oxygen at 770-920 K at rates up to 12 times the rate for the base carbon. There was a similar increase in oxygen chemisorption indicating increased number of active sites. The adsorption capacity of the carbons was mostly recovered by pyrolysis, even though the surface area and pore volume were reduced by the residue. Some oxidative regeneration is probably necessary to restore adsorption capacity for repeated use.