ISSN:
0887-624X
Keywords:
network polyester
;
ordered network structure
;
pyromellitic dianhydride
;
trimesic acid
;
soluble prepolymers
;
degree of reaction
;
heat distortion temperature
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Novel regular network polyester films were prepared from pyromellitic (X), biphenyltetracarboxylic (U), and 3,3′,4,4′-benzophenonetetracarboxylic (W) dianhydrides and ethylene glycol (2G). Prepolymers prepared by melt polycondensation were cast from DMF solution and successively post-polymerized at 260°C for various times to form a network. The resultant films were transparent, flexible, and insoluble in any solvents. The structure and properties of these network polyester films were compared with those of previously reported network polyester film from trimesic acid (Y) and 2G. Two diffraction peaks appeared in X-ray diffraction curves of 2GY, 2GX, and 2GU films. Peaks of 2GX and 2GU were broader than that of 2GY, suggesting less ordered structure of 2GX and 2GU by the less symmetric aromatic tetracarboxylic acid moieties. Densities of network films decreased with increasing the post-polymerization time. The degree of reaction (the degree of network formation) was estimated by the change of infrared absorption of hydroxyl and methylene groups. The degree of reaction obtained was 95 and 87% for 2GY and 2GX films post-polymerized for 12 h, respectively. Distortion temperature (Th) was measured by a penetration mode of thermomechanical analysis (TMA). Th, was 222 and 240°C for 2GY and 2GW films post-polymerized at 260°C for 12 h, respectively, while it disappeared for 2GX and 2GU films post-polymerized for more than 30 min and 1 h, respectively. Drastic decrease in TMA curves around 400°C corresponded to the rapid weight loss in TG curves due to the thermal decomposition. Young's modulus of network film was 2GX 〉 2GW = 2GU 〉 2GY, while the tensile strength and elongation were 2GY 〉 2GU 〉 2GW 〉 2GX. Water absorbing capacity was 2GX 〉 2GY 〉 undrawn PET, while the alkali resistance was undrawn PET = 2GY 〉 2GX.
Additional Material:
13 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1991.080291317
