[3]
73 pCBT /CNT-0. 05.
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[3]
44 pCBT /CNT-0. 1.
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[3]
26 pCBT /CNT-0. 25.
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[2]
92 pCBT /CNT-0. 5.
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[2]
33 pCBT /CNT-1.
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[2]
18 DSC. The results of DSC were reported in Fig. 1 and Table 2. A double peak endotherm was observed for the melting of neat pCBT as well as for the nanocomposites with low content of MWCNT. They could be explained by remelting–recrysallization processes during DSC scanning, the lower one represented the melting of imperfect or smaller/thinner crystals, and the higher one represented bigger crystallites. The melting peak located at the low temperature (Tm1) increased and that at the higher temperature (Tm2) gradually decreased with the increasing of content of the MWCNT. The values of Tm2 for all nanocompostites were lower than that of pure pCBT and the value differences between Tm1 and Tm2 became smaller as with more MWCNT. When the conten of MWCNT was higher than 0. 25wt%, the Tm2 disappeared and the pCBT/MWCNT nanocomposite displayed a single melting peak. These results indicated that the fact that MWCNT as heterogeneous nucleating agents accelerated the crystallization rate, at the same time, the mobility of the pCBT chains was restricted by the covalent links between the pCBT and MWCNT, this resulted in more imperfect or smaller/thinner crystallites. Fig. 1 DSC thermograms for pCBT and pCBT/MWCNT nanocompositions measured during melting (a) and cooling (b) Data in DSC measured during cooling clearly confirmed the nucleating effect of MWCNT through the increase of the crystallization peak temperature(Tc) as increasing MWCNT content. During cooling the MWCNT served as nucleation points from where crystallization can start. The more the MWCNT in the system the earlier the crystallization starts. Table 2 showed that the Tc of the pCBT/MWCNT nanocomposites with a small amount of MWCNT (1wt%) was increased to 199. 2℃, 10℃ higher than that of neat pCBT. It also could be seen in table 2 that the degree of supercooling (Tm- Tc) of the nanocomposites decreased with respected to that of neat pCBT. At the same time, the ΔHc was incrased slightly with the incrasing MWCNT content. Nevertheless the effect of MWCNT on crystallinity was small, increases in the melting enthalpy of less than 2% were observrd in the nanocomposites with 1wt% MWCNT. Table 2 DSC data of the pCBT and pCBT/MWCNT nanocomposites Sample Heating Cooling Tm1[℃] Tm2[℃] ΔHm[J/g] Tc[℃] ΔHc[J/g] Xc, DSC[%] pCBT 217. 1 224. 9.
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[52]
1 188. 9.
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[37]
6 pCBT /CNT-0. 05 219. 4 223. 5.
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[52]
9 193. 1.
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[37]
8 pCBT /CNT-0. 1 219. 8 222. 9.
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[53]
2 193. 2.
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[37]
9 pCBT /CNT-0. 25 219. 3 221. 4.
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[53]
6 193. 8.
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[38]
4 pCBT /CNT-0. 5 221. 5.
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[53]
9 195. 1.
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[38]
7 pCBT /CNT-1 222. 1.
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[54]
8 199. 2.
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[39]
6 Thermogravimetrical analysis. The role played by MWCNT on the thermal stability of pCBT was investigated by thermogravimetric analysis, performed under nitrogen, results were collected in Fig. 2 and Table 3, where temperatures corresponding to the initial thermal composition (Ti), to maximum rate of weight loss (Tmax) and the residue at 550℃ were reported. It could be noted that all of the samples displayd one step decomposition behavior, the degradation of nanocomposites was slower than that of the pure pCBT and the char yield tends to increase with increasing amount of MWCNT. However, the thermal stability of the nanocomposites based on the Ti and Tmax was observed not remarkable change as increasing MWCNT content. Similar phenomena have been also observed in some papers. It was accepted that the thermal degradation of polyester was led by random chain scission or specific chain-end scission [] F.J. Wu, G.S. Yang, Synthesis and Properties of Poly(butylene terephthalate)/Multiwalled Carbon Nanotube Nanocomposites Prepared by In Situ Polymerization and In Situ Compatibilization, J Appl Polym Sci. 118 (2010).
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8 Mechanical properties of pCBT. To examine the effect of the MWCNT on the mechanical properties of pCBT, the samples of pCBT and nanocomposites were prepared by injection molding. The flexural, tensile and impact data is summarized in Table 4 and 5. It should be noted that the toughness of pCBT and nanocomposites with 0. 05wt% and 0. 1wt% MWCNT was very good, and the samples do not break in three point bending test, but show a yield point. However, the samples with high content of MWCNT broken in a brittle manner with very low strain at break. It could be observed that the modulus and strength increased with MWCNT concentration in the nanocomposites, whether tested in tensile and flexural testing, but when samples contained more than 0. 25wt% of MWCNT, they decreased. Table 4 Flexural properties of pCBT and pCBT/MWCNT nanocomposites sample Flexural strength [MPa] Flexural modulus.
DOI: 10.1002/mame.201000381
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[88]
8±0. 8 2354. 4±5. 1 - - pCBT /CNT-0. 05.
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[93]
5±0. 6 2508. 7±4. 5 - - pCBT /CNT-0. 1.
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[94]
0±0. 6 2633. 7±3. 8 - - pCBT /CNT-0. 25.
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[98]
6±1. 0 2781. 4±2. 6.
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6±0. 1 pCBT /CNT-0. 5.
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[93]
3±1. 2 2754. 7±3. 2.
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4±0. 1 pCBT /CNT-1.
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[85]
3±1. 8 2709. 9±3. 9.
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3±0. 1 Table 5 Tensile properties and impact strength of pCBT and pCBT/MWCNT nanocomposites sample Tensile strength [MPa] Tensile modulus [MPa] Elongation at break [%] Absorbed energy at break [J] Impact strength.
DOI: 10.3403/01864183u
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[54]
6±0. 6 1156. 5±3. 7 525. 9±8. 3.
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[5]
5±0. 2 pCBT /CNT-0. 05.
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[54]
8±0. 9 1209. 6±3. 8 421. 4±9. 6.
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[5]
2±0. 3 pCBT /CNT-0. 1.
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[56]
2±0. 5 1316. 3±3. 4 112. 6±6. 1.
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[5]
1±0. 2 pCBT /CNT-0. 25.
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[58]
2±0. 8 1356. 2±1. 4.
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[4]
6±0. 3 pCBT /CNT-0. 5.
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[57]
1±0. 4 1345. 3±4. 8.
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[4]
2±0. 4 pCBT /CNT-1.
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[55]
3±1. 0 1343. 2±2. 4.
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[3]
8±0. 5 One could notice that when the content of MWCNT more than 0. 5wt%, a large drop was found for the flexural strength and tensile strength which did not appear in the flexural modulus and tensile modulus response. This could be explained by the fact that modulus was sensitive to the filler amount, whereas, the strength was strongly influenced by the filler dispersion and the interaction between the filler and matrix [] G. Romhany, J. Vigh, R. Thomann, J. Karger-Kocsis, I.E. Sajo, pCBT/MWCNT Nanocomposites Prepared by In situ Polymerization of CBT After Solid-Phase High-Energy Ball Milling of CBT with MWCNT, Macromol Mater Eng. 296 (2011).
DOI: 10.1002/mame.201000381
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