Dynamic mechanical behavior of some high polymers at temperatures from 6°K.: Polyethylene, nylon 66, polypropylene, poly(vinyl chloride), poly‐(d,l‐propylene oxide), polybutene‐1, poly(4‐methyl‐pentene‐1), poly(methyl methacrylate), poly(ethyl methacrylate), poly‐4‐methylpentene‐1 and poly(isobutyl methacrylate)

Measurements of the dynamic mechanical properties of various polymers have been made in the 6–300°K. temperature range at resonant frequencies of about 10 4 cycles/sec. by using a longitudinal vibration apparatus. The polymers studied include polyethylene, nylon 66, three poly(methacrylate esters), and five poly‐α‐olefins and related polymers. Results for poly(methyl methacrylate) and poly(ethyl methacrylate) indicate the occurrence of low temperature relaxation processes (6°K. and 52°K., respectively) involving configurational rearrangements in the hydrocarbon portion of the ester side groups. The data provide no evidence for mechanical loss processes associated with hindered rotation of the main‐chain methyl groups in the poly(methacrylate esters) or polypropylene. Very weak relaxation processes or loss plateaus are observed in the 20°K. region for polypropylene, poly(vinyl chloride), poly( d , l ‐propylene oxide), poly(isobutyl methacrylate) and possibly nylon 66, while for poly‐4‐methylpentene‐1 a sizeable loss peak is observed at 25°K. The mechanisms responsible for these loss peaks are not yet understood. No relaxation phenomenon is observed below 77°K. for either polyethylene or polybutene‐1. For poly( d , l ‐propylene oxide) a loss maximum or shoulder appears at 70–120°K. which is possibly associated with chain motions accompanying the methyl reorientation process.