Thermal induced crystalline transition of bio-based polyamide 56

High Concentration Lignin Biocomposites with Low Melting Point Biopolyamide

“…2a and b. All the synthesized samples presented typical FTIR characteristic peaks of polyamides reported in the literature [41,42]. There were as follows: a peak at 3297 cm −1 assigned for the N -H bond, two sharp peaks at 2930 cm −1 and 2850 cm −1 , respectively, attributed to CH 2 asymmetric and symmetric stretch; two peaks at 1640 cm −1 and 1545 cm −1 , respectively, corresponded to amide I (stretch C--O) and amide II (-NH-CO-), a peak at 1466 cm −1 due to C--O bending, and a peak at 945 cm −1 arose from amide IV.…”

Furfural-Based Polyamides with Tunable Fluorescence Properties via Ugi Multicomponent Polymerization

“…The peaks at 1680 and 1625 cm –1 correspond to the typical CO stretching (band I of amide). The appearance of characteristic peak at 1570 cm –1 is attributed to the band II of amide. ,, The bands at 3417 and 3326 cm –1 are assigned to the free and hydrogen-bonded N–H stretching, respectively. , In addition, the CC stretching vibrations in furan structure probably overlaps with the amide characteristic peak . The signals at 1415 and 1370 cm –1 correspond to characteristic peaks from the tert -butyl groups.…”

“…The appearance of characteristic peak at 1570 cm −1 is attributed to the band II of amide. 27,30,31 The bands at 3417 and 3326 cm −1 are assigned to the free and hydrogen-bonded N−H stretching, respectively. 32,33 In addition, the C�C stretching vibrations in furan structure probably overlaps with the amide characteristic peak.…”

Thermal-Field-Tuned Heterogeneous Amorphous States of Poly(vinylidene fluoride) Films with Precise Transition from Nonpolar to Polar Phase

“…Building a relationship between structure evolution and thermodynamic factors is of great significance for physical science, because the thermal field around a matter can be tuned readily by controlling the temperature in most cases. − Thermally treating a material above its glass transition temperature ( T g ) can activate molecules inside it and thus influences its morphology and multiscale structures. − Due to the complex structure evolution in semicrystalline polymeric materials during the heating process, the temperature selected for thermal treatment (i.e., the self-nucleation temperature, denoted T s ) plays an essential role in the morphology developed upon subsequent cooling. ,− Generally, a temperature between T g and the melting temperature ( T m ) of a polymer enables lamellar crystals to thicken, while a temperature above T m induces melting of crystals. Nevertheless, the melting of polymers usually occurs in a gradual way and covers a wide temperature range, resulting in a series of intermediate thermodynamic nonequilibrium states between the crystalline and melt states. − That is to say, polymer chains can experience a variety of states from dense packing in crystals to random distribution in the homogeneous isotropic melt, determined by melting temperature and time.…”