Transcript All-aromatic Liquid Crystalline Polyester Thermosets with

High Tg ester based liquid
crystal thermosets:
synthesis and characterization
PhD Candidate: Martino Marchetti
Department: ASM
Section: Novel Aerospace Materials
Supervisor: Prof. Theo Dingemans
Promoter: Prof. Theo Dingemans
Start date: 01-01-2013
Thermal stability
Liquid crystal thermosets are a unique sub-set of high-performance polymers that combine
desirable processing characteristics with outstanding thermo-mechanical properties after
cure. LCTs are prepared via the so called reactive oligomer approach, where the oligomer
backbone is terminated with latent end-groups that can react in a successive thermal post
treatment step to form a network structure. In this work we have explored the most rigid,
high Tg (~ 400 oC) LCT formulation known to data, i.e. based on 4-hydroxybenzoic acid
(HBA), terephthalic acid (TA) and 4,4’-biphenol (BP).
Herein we will discuss the thermo mechanical performance of these new polymers.
Nitrogen
100
5K Oligomers
Air
N2
75
Weight [%]
Introduction
50
Air
5% weight loss
[ºC]
Char yield 595 oC
[%]
5% weight loss
[ºC]
HBA/BP/TA (20)
486
54
482
HBA/BP/TA (25)
490
50
475
HBA/BP/TA (30)
495
50
484
HBA/BP/TA (35)
487
49
475
25
Oligomer synthesis
Nitrogen
0
75
150
225
300
375
450
525
600
9K Oligomers
5% weight loss
[ºC]
Char yield 595 oC
[%]
5% weight loss
[ºC]
HBA/BP/TA (20)
490
51
484
HBA/BP/TA (25)
497
53
484
HBA/BP/TA (30)
496
50
488
HBA/BP/TA (35)
491
48
486
Temperature [°C]
Thermal
stability
of
the
HBA/BP/TA(20)-9K
cured
thermosets, measured from room
temperature to 600 ºC, under
nitrogen atmosphere (red) and air
atmosphere (blue), using a heating
rate of 10 ºC/min.
Air
Thermo-mechanical behavior
2,0
HBA/BP/TA (20)
Melt behavior of the oligomers
5K Oligomer
Onset Temperature [ºC]
Peak maximum (TK-N )[ºC]
HBA/BP/TA (20)
252
311
HBA/BP/TA (25)
290
327
HBA/BP/TA (30)
301
328
HBA/BP/TA (35)
304
332
20
25
30
35
N
K
E' [Pa]
378
9
1,5
10
0.65
HBA/BP/TA (25)
405
0.81
HBA/BP/TA (30)
419
0.79
HBA/BP/TA (35)
427
0.95
9K thermosets
Glass Transition
Temperature Tg [ºC]
Storage modulus
at 300 ºC [GPa]
HBA/BP/TA (20)
357
0.59
HBA/BP/TA (25)
380
0.44
HBA/BP/TA (30)
425
1.5
HBA/BP/TA (35)
430
0.75
1,0
8
10
0,5
7
10
100
200
300
0,0
500
400
Temperature (°C)
Representative DMTA scan for
HBA/BP/TA(35)-5K. The experiment
was performed under a N2
atmosphere using a heating rate of 2
ºC/min and a frequency of 1 Hz.
Tg data were obtained from DMTA
experiments and defined by the
maximum of the E’’ peak.
Exotherm
10
10
9K Oligomer
Onset Temperature [ºC]
Peak maximum (TK-N )[ºC]
10
HBA/BP/TA (20)
262
316
10
9
8
100
HBA/BP/TA (25)
306
346
HBA/BP/TA (30)
324
353
HBA/BP/TA (35)
328
363
150
200
250
300
350
DMTA
data
showing
HBA/BP/TA(35)-5K film (red)
and a commercial available
polyether-ketoneketone (PEKK)
sample (black).
Temperature [°C]
DSC signals of the 5K oligomers
series. First heat using a
heating rate of 20 ºC/min.
Phase behavior
7
10
PEKK
HBA/BP/TA(35)-5K
6
10
E' [Pa]
Aerospace Engineering
5K thermosets
Series 9000 g/mol - HBA/TA/BP
• 60%/20%/20%
• 50%/25%/25%
• 40%/30%/30%
• 30%/35%/35%
Series 5000 g/mol - HBA/TA/BP
• 60%/20%/20%
• 50%/25%/25%
• 40%/30%/30%
• 30%/35%/35%
Storage modulus
E’ at 300 ºC [GPa]
tan 
Synthesis of the all-aromatic ester-based reactive liquid crystalline oligomers
end-capped with phenylethynyl reactive end-groups.1
Glass Transition
Temperature Tg [ºC]
E'' [Pa]
Samples
5
10
4
10
3
10
2
10
1
10
0
10
50
100
150
200
250
300
350
400
450
Temperature (°C)
Conclusions and future Work



A
B
Nematic textures of HBA/BP/TA(25)-9K observed by polarized microscopy.
A– Low viscous sample at 370 ºC during cure. B– Crosslinked sample at 550 ºC
after the complete cure.
1. Mazhar Iqbal, Theo J. Dingemans, European Polymer Journal, 2010, 46, 2174–2180.


The reactive oligomer approach is an excellent method towards novel processable allaromatic liquid crystalline polyesters based on all-para-substituted monomers
(HBA/BP/TA).
High Tg (> 350 oC) and high thermal stability (Td5% (N2) > 475 oC) make this class of
polymers promising for demanding high-performance applications.
All cured polymers show excellent storage moduli (E’) as function of temperature and
easily out performs PEKK.
Melt and cure rheology analyses are in progress.
One or two reactive oligomers will be selected and used as matrix in carbon fiber
reinforced composites.