Study on melting and polymorphic behavior of poly(decamethylene terephthalamide)

Abstract

This work describes the melting and polymorphic behavior of poly(decamethylene terephthalamide) (PA 10T). Both solution‐crystallized (SC) and melt‐crystallized (MC) PA 10T show double melting endotherms in DSC. The SC crystal form melts at 260–300°C giving the first melting endotherm, and meanwhile undergoes a polymorphic transition forming the MC crystal form. The subsequent melting of the MC crystal form gives the second melting endotherm at 300–325°C. This irreversible polymorphic transition is confirmed by variable‐temperature WAXD and IR. Dynamic mechanical thermal analysis (DMTA) shows a glass transition temperature (Tg) at 127°C and the presence of an α′ transition at 203°C (0.1 and 1 Hz). This transition could be confirmed by DSC and variable‐temperature WAXD experiments. The α′ transition correlates with a reversible thermal process and a sudden change in intersheet spacing. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 465–472

Effect of Aliphatic Chain Length on the Stress–Strain Response of Semiaromatic Polyamide Crystals

“…[25][26][27][28][29][30][31][32] One such approach is to combine the rigidity of aromatic moieties and the flexibility of aliphatic moieties to create so-called aromatic-aliphatic polyamides. 11,20,[33][34][35][36][37][38] It is expected that even minor changes in the molecular structure of the aromatic-aliphatic polyamides might significantly affect the mechanical behavior. For example, longer spacer lengths for a given aromatic amide system leads to a reduction in hydrogen bond density which will lower the melting temperature.…”

“…Extensive research has been conducted to develop materials with properties comparable to PPTA but with potentially better processability . The high melting temperature of PPTA is a result of its rigid and extended conformation, which is due to the rigidity of the aramid backbone and strong intermolecular interactionshydrogen bonding (H-bonding) and π-stacking. ,− A variety of methods have been attempted by using chemical modification to lower the melting temperature, including introducing bulky, packing-disruptive groups into the polymer chain or as side groups, incorporating flexible groups into the polymer backbone, and by using meta -substituted or otherwise asymmetric monomers. − One such approach is to combine the rigidity of aromatic moieties and the flexibility of aliphatic moieties to create so-called aromatic–aliphatic polyamides. ,,− …”

Exploring Oxidative NHC‐Catalysis as Organocatalytic Polymerization Strategy towards Polyamide Oligomers

“…The number‐average molecular weight of 3 ba’’ was estimated with the Mark–Houwink Equation considering K = 5.58×10 −4 dL g −1 and α =0.81. These constants were initially calculated for PA12T [18a] and subsequently adopted for PA10T due to the similar molecular structures of these polymers [16e, 18b] . The resulting M n for 3 ba’’ was 22.3 kg mol −1 , a value which was in good agreement with that determined by NMR analysis ( M n =20.2 kg mol −1 ): …”

“…Indeed, size exclusion chromatography (SEC) of semi‐aromatic PAs is complicated by their low solubility in common organic solvents and the requirement of sophisticated equipment compatible with pure HFIP as eluent. On the other hand, viscometry is widely recognized as a reliable method for the determination of molecular weight for this class of polymers [16e, 18] . In particular, Mathias and co‐workers found a correlation between the number‐average molecular weight estimated by NMR spectroscopy and the intrinsic viscosity ([ η ]) of a series of PAs [18a] with M n in the range of about 2–25.2 kg mol −1 [18] .…”

Polyphthalamide polymers: A review on synthesis, properties, and advance manufacturing and emerging applications

“…Li studied how the crystallinity of PA10T changed, depending on the stage in which it was measured 31 : after the synthesis of the PPA through solution polymerization (SC), and after a DSC analysis on the sample had been performed (MC). Both crystalline structures had two endotherms, attributed to a melting-recrystallization of one crystal, further DSC analyzes using an isotherm and then confirming it.…”