Introduction
Experimental
Materials
Synthesis of thiourethane prepolymer with reactive isocyanate groups
Synthesis of IPDI filled polythiourethane microcapsules
Preparation of epoxy composites
No. | Composite name (type of shell wall/amount of microcapsules/additives) | Amount of components (phr) | |||
---|---|---|---|---|---|
Epidian 5 | ET | PTURmcaps | DMP-30 | ||
1 | p-TUR-DODT/18 | 100 | 18 | 18 | 0 |
2 | p-TUR-TTMP/18 | 100 | 18 | 18 | 0 |
3 | p-TUR-PETMP/18 | 100 | 18 | 18 | 0 |
4 | IPDI-TTMP/18 | 100 | 18 | 18 | 0 |
5 | IPDI-PETMP/18 | 100 | 18 | 18 | 0 |
6 | IPDI-PETMP/30 | 100 | 18 | 30 | 0 |
7 | IPDI-PETMP/30/DMP | 100 | 18 | 30 | 1 |
Optical microscopy
Atomic force microscopy (AFM)
Three-point bending test
Fourier transform infrared (FT-IR) analysis
Scratch test
Scale 1: self-healing efficiency | Point | Scale 2: chemical resistance | Point |
---|---|---|---|
No self-healing observed | 0 | No changes on surface | A |
Low efficiency | 1 | Low level of changes | B |
Average efficiency | 2 | Average level of changes | C |
Good efficiency | 3 | High level of changes | D |
Excellent efficiency | 4 | Severe damage on sample | E |
Results and discussion
Synthesis and characterization of prepolymer and microcapsules
Self-healing mechanism characterization
Optical microscopy
AFM
Three-point bending test
No. | Composite name | Flexural stress at break (σ
fB) (MPa) | Flexural modulus (E
f) (MPa) | Microcracks self-healing efficiency (%) | |||
---|---|---|---|---|---|---|---|
Standard method (virgin) | Custom method (after 20 N pre-bending) (healed) | Standard method (virgin) | Custom method (after 20 N pre-bending) (healed) |
σ
fB
|
E
f
| ||
0 | Reference sample | 43.7 | – | 2580 | – | – | – |
1 | p-TUR-DODT/18 | 16.7 | 17.3 | 1980 | 2010 | 103.6 | 101.5 |
2 | p-TUR-TTMP/18 | 22.0 | 14.3 | 1680 | 1580 | 65.0 | 94.0 |
3 | p-TUR-PETMP/18 | 31.4 | 24.7 | 2280 | 2050 | 78.7 | 89.9 |
4 | IPDI-TTMP/18 | 24.2 | 17.8 | 1840 | 1940 | 73.6 | 105.4 |
5 | IPDI-PETMP/18 | 19.7 | 25.6 | 1630 | 2510 | 129.9 | 154.0 |
6 | IPDI-PETMP/30 | 12.7 | 19.7 | 1290 | 1720 | 155.1 | 133.3 |
7 | IPDI-PETMP/30/DMP | 9.6 | 17.0 | 1230 | 2060 | 177.1 | 167.5 |
FT-IR analysis
Composite number → | 0 | 1 | 1A | 2 | 2A | 3 | 3A | 4 | 4A | 5 | 5A | 6 | 6A | 7 | 7A |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Approximate assignment ↓ | |||||||||||||||
N–H and O–H stretching (alcohols, amines, amides) | 3396 | 3360 | 3388 | 3359 | 3393 | 3360 | 3393 | 3360 | 3397 | 3360 | 3397 | 3360 | 3396 | 3361 | 3390 |
C=O stretching, (amide groups: ureas, thiourethanes and urethanes); aromatic ring overtone* | 1654* | 1656 1652 1648 1644 | 1656 1651 | 1653 | 1650 | 1652 1641 | 1656 1645 | 1652 1644 | 1648 | 1652 | 1648 | 1644 | 1651 | 1651 | 1657 1650 |
N–H bending (amines, thiourethanes and urethanes) | 1580 | 1579 | 1579 | 1580 | 1575 | 1580 | 1580 1574 | 1579 | 1581 | 1577 1560 1556 | 1578 1544 | 1580 | 1574 1543 | 1581 1556 | 1574 |
–NH–CO–S– bending (thiourethanes); triazine compounds (isocyanurates) | 1506 | 1508 | 1505 | 1510 | 1506 | 1507 | 1506 | 1506 | 1508 | 1509 | 1507 | 1508 | 1507 | 1507 | |
C–N axial stretching (isocyanate group [42]) | 1383 | 1386 | 1384 | 1388 | 1384 | 1386 | 1383 | 1383 | 1390 | 1388 | 1382 | 1387 | 1383 | 1386 | |
C–H bending in geminal dimethyl group (IPDI) | 1361 | 1362 | 1361 | 1361 | 1361 | 1362 | 1361 | 1361 | 1362 | 1361 | 1362 | 1361 | 1362 | ||
–CH2–S– bending [33]; C–O stretching (alcohols)* | 1039* 1028* | 1030 | 1034 | 1030 | 1037 | 1031 | 1029 | 1031 | 1027 | 1032 | 1038 | 1026 | 1038 | 1031 | 1028 |
C–S stretching | 553 | 556 | 552 | 547 | 554 | 559 546 | 553 | 552 | 553 547 | 546 | 552 | 547 | 553 | 552 |
Scratch test
No. | Composite name | Solvent/solution | |||||
---|---|---|---|---|---|---|---|
– | Water | 20% KOH aq. | 20% H2SO4 aq. | THF | DMSO | ||
0 | Reference sample | 0.A | 0.A | 0.A | 0.A | 0.B | 0.C |
1 | p-TUR-DODT/18 | 1.A | 2.A | 2-3.A | 3.B-C | 3.B | 3.B |
2 | p-TUR-TTMP/18 | 3.A |
3-4.A
| 3.A-B | 2.A-B | 2-3.A-B | 2.A-B |
3 | p-TUR-PETMP/18 | 2.A |
3-4.A
| 2-3.A | 2-3.A-B | 2-3.B | 2-3.Da
|
4 | IPDI-TTMP/18 | 0-1.A | 0-1.A | 1.B | 2.C | 2.A-B | 1-2.B |
5 | IPDI-PETMP/18 | 0-1.A | 0-1.A | 1.C-D | 1.A | 2.B | 2.B-C |
6 | IPDI-PETMP/30 | 1-2.A | 2.A | 2-3.A | 1-2.B | 2-3.A-B | 2.B-C |
7 | IPDI-PETMP/30/DMP | 1-2.A | 1-2.A | 1.B-C | 1-2.B | 2.A-B | 2.C |