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High T g 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. - PowerPoint PPT Presentation
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Oligomer synthesis
Synthesis of the all-aromatic ester-based reactive liquid crystalline oligomers end-capped with phenylethynyl reactive end-groups.1
DSC signals of the 5K oligomers series. First heat using a heating rate of 20 ºC/min.
Melt behavior of the oligomers
Thermal stability
Tg data were obtained from DMTA experiments and defined by the maximum of the E’’ peak.
Introduction
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.
Conclusions and future Work
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.
The reactive oligomer approach is an excellent method towards novel processable all-aromatic 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.
Series 5000 g/mol - HBA/TA/BP• 60%/20%/20%• 50%/25%/25%• 40%/30%/30%• 30%/35%/35%
Series 9000 g/mol - HBA/TA/BP• 60%/20%/20%• 50%/25%/25%• 40%/30%/30%• 30%/35%/35%
75 150 225 300 375 450 525 6000
25
50
75
100
Wei
ght [
%]
Temperature [°C]
Air N
2
Thermo-mechanical behavior
Phase behavior
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.
A B
5K Oligomers
Nitrogen 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
9K Oligomers
Nitrogen Air
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
5K OligomerOnset 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
9K OligomerOnset Temperature
[ºC]Peak maximum (TK-N )[ºC]
HBA/BP/TA (20) 262 316
HBA/BP/TA (25) 306 346
HBA/BP/TA (30) 324 353
HBA/BP/TA (35) 328 363
100 150 200 250 300 350
20 25 30 35
Temperature [°C]
Exo
the
rm
KN
SamplesGlass Transition
Temperature Tg [ºC]
Storage modulus E’ at 300 ºC [GPa]
5K thermosets
HBA/BP/TA (20) 378 0.65
HBA/BP/TA (25) 405 0.81
HBA/BP/TA (30) 419 0.79
HBA/BP/TA (35) 427 0.95
9K thermosetsGlass 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
100 200 300 400 500
107
108
109
E' [
Pa]
Temperature (°C)
tan
E''
[Pa]
0,0
0,5
1,0
1,5
2,0
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.
50 100 150 200 250 300 350 400 450100
101
102
103
104
105
106
107
108
109
1010
E' [
Pa]
Temperature (°C)
PEKK HBA/BP/TA(35)-5K
DMTA data showing HBA/BP/TA(35)-5K film (red) and a commercial available polyether-ketoneketone (PEKK) sample (black).
Aero
space
Eng
ineeri
ng
High Tg ester based liquid crystal thermosets:
synthesis and characterization
PhD Candidate: Martino MarchettiDepartment: ASMSection: Novel Aerospace MaterialsSupervisor: Prof. Theo DingemansPromoter: Prof. Theo DingemansStart date: 01-01-2013
1. Mazhar Iqbal, Theo J. Dingemans, European Polymer Journal, 2010, 46, 2174–2180.