The Brill Transition
The Brill Transition was reported in 1942 by R. Brill [J. Praktische Chemie, 161, 49-64 (1942)] and is a first order transition in polyamides, a sharp reversible polymorphic phase transition from the triclinic to psuedohexagonal structure at 162 C. Wolanov et al has shown that the change in the d spacings with temperature ofthe 010/110 diffraction, which precedes the Brilltransition, is characterized by a two step behavior. The step change is characterized by a sharp tilt followed by a steep increase of the d spacing all theway to the Brill transition temperature. It is claimedthat this step change reflects a critical free volumechange and an onset of segmental chain movementin the amorphous phase. Dynamic mechanical analysis identified in specifically treated nylon 66 and microcomposite samples a prominent process, which corresponds to this step change. Hence, the observed á′ relaxation and the Brill transition are taken as counterparts, wherein the occurrence of the first triggers that of the latter. (RDC 2/14/2011) [Express Polymer Letters, 3, #7, 452-457 (2009)]
Recent Journal Articles
Mechanism in Brill transition of polyamide 66 studied by two-dimensional correlation infrared spectroscopy
(230-237) European Polymer Journal 47 #2 (2011)
Luo et al of Sichuan University and Baling Petrochemical Industry Co, China used 2D correlation spectroscopy to study the sequential order of polyamide 66 chains with linear increment of temperature. The temperature range of the Brill transition determined by MW2D correlation spectroscopy was 90–170 °C. The movement of the methylene segments near to NH is earlier than those on the CO sides. At the same time, the methylene which is close to NH varies before the inner methylene. Three kinds of NH groups in polyamide 66 were found. The sequential order of their motions is as follows. The free hydrogen-bonded NH groups change first, and then the disordered hydrogen-bonded NH groups. Finally, the ordered hydrogen-bonded NH groups start to change. We also found that the changes of the ordered hydrogen-bonded NH groups follow with the methylene groups. (RDC 2/14/2011)