244 Introduction to Renewable Biomaterials
Table 8.5Effect of four different ionic liquids on PLA thermal properties.
Sample
Decomposition
temperature (∘C)
Glass transision
temperature (∘C)
Melting
peak (∘C)
PLA 357 60.6 164.2
PLA+10% [MPI][BF 4 ] 364 62.8 174.1
PLA+20% [MPI][BF 4 ] 368 62.3 174.3
PLA+10% [MPI][BF 4 ] 366 63.6 174.6
PLA+20% [MPI][BF 4 ] 370 62.9 175.6
PLA+10% [MPI][TFSI] 362 53.8 172.6
PLA+20% [MPI][TFSI] 364 51.4 172.9
PLA+10% [DMPI][TFSI] 363 59.6 173.8
PLA+20% [DMPI][TFSI] 365 57.9 174.2
Chenet al. 2013 [6]. Reproduced with permission of Elsevier.
0
0
10
10
20
20
30
30
40
40
Strain (%)
PLA
+[MPI][TFSI]
+[MPI][BF 4 ]
+[MPI][PF 6 ]
+[DMPI][TFSI]
Stress (MPa)
50
50
60
Figure 8.2Stress–strain curves of neat PLA and PLA modified with four different ionic liquids.
Chenet al. 2013 [6]. Reproduced with permission of Elsevier.
They demonstrated that ionic liquids can improve ductility of PLA and slightly
improve its thermal stability but with a considerable reduction in both tensile strength
and modulus.
Another interesting and fairly new thermoplastic bio-derived polymer is thermo-
plastic starch (TPS). Starch is a high available renewable source, present in many
different plants such as potato, corn, wheat or waxy corn [7]. Granules of starch
are composed of amylose and amylopectin in different percentages, affecting their
mechanical properties. In fact, amylose is a linear polymer of d-glucose units attached
atα-1,4, and amylopectin is a highly branched polymer of d-glucose units attached
atα-1,4 andα-1,6. The amylose/amylopectin ratio depends on plant source, and this
effect is evident in Figure 8.3.
