A small amount of poly(trimethylene succinate) (PTSu) were copolymerized or blended with poly(butylenes succinate) (PBSu) in this study. The range of intrinsic viscosity for PBSu and PBSu-enriched copolymers are between 1.62 and 0.97 dL/g; number-average molecular weights are in the range of 2.5x104 and 11.9x104 g/mol with polydispersity indices ranging from 1.52 to 3.94. Copolymer composition is calculated from 1H and 13C NMR spectra, and the distribution of BS and TS units in these copolymers are supported to be random from the evidence of a single glass transition temperature (Tg) and a randomness value close to 1.0. Tg of PBSu is -40.8 ¢XC. The Tg values of copolymers and blends increased with TS contents. The melting temperature (Tm) and the exothermic heat of crystallization of blends were not strongly affected by blending with PTSu.
The values of Avrami exponent (n) for PBSu, copolymers and blends ranging from 2.3 to 3.1 indicate that heterogeneous nucleation with three-dimensional growth and homogeneous nucleation with two-dimensional growth might happen during the crystallization process. Multiple melting behavior was observed for PBSu, PBSu- enriched copolyesters and blends. Their peak temperatures are denoted as Tm1, Tm2 and Tm3 in order of increasing temperature. Tm1 corresponds to the melting temperature of the so-called annealing peak which might be resulted from the competition between continuous melting and re-crystallization. In contrast the peak at Tm2 is attributed to the melting of the primary crystals formed during isothermal crystallization. The peak at Tm3 may arise from the melting of re-crystallized primary crystals. Equilibrium melting temperatures were determined by the Hoffman-Weeks linear extrapolations which yield of 127.4 ¢XC for PBS, 125.7 ¢XC for PBTSA95/05, 120.6 ¢XC for PBTSu90/10, 128.6 ¢XC for PBSu/PTSu 98/02, 127.0 ¢XC for PBSu/PTSu 95/05 and 125.5 ¢XC for PBSu/PTSu 90/10. The thickness coefficient ( ) is located between 0.77 and 0.80.
Three characteristics temperatures of thermal degradation, defined as temperature of thermal degradation at begining (Tstart), weight losses of 2% (Tloss2%) and maximum degradation rate (Tmax), were employed to characterize the thermal stability of polyesters and blends. The Tloss2% and Tstart values of PBTSu90/10 are higher than the values of the others because of its unusually high molecular weight.
Wide-angle x-ray diffraction patterns were obtained after complete isothermal crystallization. Diffraction peaks are in the same positions, and these peaks become sharper and increase in intensity as the crystallization temperature increases. This indicates that during the heating process, only one crystal form appears and both of the crystallite size and perfect degree increase. The isothermal growth rate of PBSu spherulite increases from 0.01 £gm/sec at 103 ¢XC to 3.33 £gm/sec at 75 ¢XC. When the TS units increase, the spherulitic growth rates of PBTSu95/05 and PBTSu90/10 copolyesters decline dramatically. One of the reasons is that the incorporation of TS units into PBSu significantly inhibits the crystallization behavior of PBSu. Growth rates data were treated with Lauritzen-Hoffman secondary nucleation theory to find the regime transition. Using the Williams-Landel-Ferry (WLF) values, regime II to III transition is found at 95.1 ¢XC for PBSu, 84.4 ¢XC PBTSu95/05, and 77.1 ¢XC for PBTSu 90/10. All melt-crystallized specimens formed two dimensional axial-like spherulites with negative birefringence. Extinction bands were observed when PBSu, PBSu- enriched copolymers and blends specimens were crystallized at large undercooling.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0724107-160220 |
| Date | 24 July 2007 |
| Creators | Peng, Jyun-siang |
| Contributors | Shih-tian Wei, Jin-long Hong, Ming Chen, Shih-rong Bai |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0724107-160220 |
| Rights | withheld, Copyright information available at source archive |
Page generated in 0.0022 seconds