Fig. 1
Theories of plasticization
Fig. 2
Mechanism of plasticiser's action
Fig. 3
Table 1
Properties of 6201D PLA according to manufacturer's data
| Property | Value | Method |
|---|---|---|
| Specific gravity, g/cm3 | 1.24 | ASTM D792 |
| Relative viscosity | 3.1 | CD Internal Viscotek Method |
| Melt index (210°C), g/10 min | 15–30 | ASTM D1238 |
| Glass transition temperature, °C | 55–60 | ASTM D3417 |
| Crystalline melt temperature, °C | 160–170 | ASTM D3418 |
Table 2
Substances used in the PLA plasticisation process
| Plasticiser | Producer | Mw′, g/mol | Structure |
|---|---|---|---|
| Glycerol triacetate (TAC) | ThermoFisher Scientific, Germany | 218 |  |
| Triethyl citrate (TEC) | Gentham, UK | 276 |  |
| Acetyl triethyl citrate (Ac-TEC) | TCI, Japan | 318 |  |
| Tributyl citrate (TBC) | Acros, USA | 360 |  |
| Acetyl tributyl citrate (Ac-TBC) | Merck, Germany | 402 |  |
[i] Sample indication:
[ii] base PLA; unmodified polymer
[iii] TAC: PLA with 10% wt. of glycerol triacetate
[iv] TEC: PLA with 10% wt. of triethyl citrate
[v] Ac-TEC: PLA with 10% wt. of acetyl triethyl citrate
[vi] TBC: PLA with 10% wt. of tributyl citrate
[vii] Ac-TBC: PLA with 10% wt. of acetyl tributyl citrate
Table 3
Thermal parameters obtained during the second heating
| Sample | Thermal analysis | |||||
|---|---|---|---|---|---|---|
| Tg′, °C | ΔCp′, J/gK | Tcc′, °C | ΔHcc′, J/g | Tm′, °C | ΔHm′, J/g | |
| base PLA | 60.0 | 0.50 | 123.9 | 42.1 | 165.9 | 42.2 |
| Plasticiser | Plasticised PLA | |||||
| TAC | 38.8 | 0.51 | 100.8 | 35.2 | 150.0 161.9 | 35.3 |
| TEC | 41.7 | 0.52 | 104.2 | 35.1 | 153.0 164.4 | 35.3 |
| Ac-TEC | 37.5 | 0.50 | 101.6 | 34.3 | 149.8 162.1 | 34.4 |
| TBC | 37.8 | 0.49 | 93.0 | 34.6 | 148.9 163.7 | 34.8 |
| Ac-TBC | 40.1 | 0.52 | 96.0 | 35.0 | 151.0 164.1 | 35.0 |
Fig. 4
Glass transition temperature after the second heating
Fig. 5
MFR values of the base and plasticised PLA
Fig. 6
Molar mass (Mw) estimated using RI detector
Fig. 7
Molar mass distribution curves
Fig. 8
Breaking tenacity of the base and plasticized PLA
Fig. 9
Elongation at break of the base and plasticized PLA
Fig. 10
Young's modulus of the base and plasticized PLA
Fig. 11
FTIR-ATR spectra for plasticized PLA
Fig. 12
FTIR-ATR spectra for plasticizers