Effect of Annealing on Structural and Mechanical Properties of Compacted Reactor Powders of UHMWPEстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 4 января 2018 г.
Местоположение издательства:Road Town, United Kingdom
Первая страница:307
Последняя страница:311
Аннотация:The effect of annealing temperatures ranging from 20 to 130°C on mechanical properties of compacted
reactor powders of ultra-high-molecular-weight polyethylene was studied. The dependence of strength
on the annealing temperature may be presented as a sum of two exponential functions, which describe changes
in strength due to the occurrence of two concurrent processes: formation of cohesion bonds between grains and
breakdown of dense contacts between grains in the compacted reactor powder. The latter process is provided
by a partial shape recovery of grains due to relaxation of stresses stored in deformed polymer regions during
compaction. In the temperature interval of α-transition, the shape recovery of grains is completed quickly, and
its effect on the number of newly formed cohesion bonds between contacting grains ceases. As a result, strength
and elongation-at-break increase at a higher rate as compared with their increase in the case of the same variations
in the annealing temperature in a lower temperature region. The preliminary annealing of the reactor powder
in the temperature region corresponding to the α-transition prevents the formation of intergrain entanglements
during compaction, and the resultant behavior of nascent and annealed reactor powders during compaction
and subsequent annealing of pellets is controlled by the same mechanisms.