1. Santiranjan Shannigrahi
Polymer-Ceramic Composite Film Fabrication and Characterization for Harsh Environment Applications
Santiranjan Shannigrahi

2. Polymer-ceramics composites Basic applications Current pain Case study
OUTLINES:
Polymer-ceramics composites
Basic applications
Current pain
Case study
Conclusions

3. GRAPH OF MATERIALS PRODUCTION
Polymer – ceramic composites
Source: CES EduPack, University of Cambridge/Granta.

4. APPLICATIONS OF POLYMER COMPOSITES

5. CURRENT PAIN Harsh environment: Light/heat Moisture, UV illumination.
Significant Impact on polymer matrices

6. Composites: 1. Epoxy matrix
CASE STUDY
Composites: 1. Epoxy matrix
Temperature
Moisture
Reversibility
2. PE matrix
UV and temperature

7. COMPOSITE FILM FABRICATION
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Twin-Screw Extruder for mixWeatherability testing ing, compounding and processing
Twin-Screw Extruder for mixWeatherability testing ing, compounding and processing

8. UV-VIS characterization
HARSH ENVIRONMENTS AND CHARACTERIZATIONS
Humidity chamber (90% Rh & 90oC
Specimens
The total UV energy is W/m2
UV-Chamber
UV-3101 PC
UV-VIS-NIR-spectrophotometer SHIMADZU, ( nm)
UV-VIS characterization
Flexural testing using
three point bending set up
Mechanical testing
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9. EXPERIMENTAL DESIGN (EPOXY)
Three factors can affect the properties of the epoxy in hygrothermal environment
Elevated temperature
Relaxation of polymer matrix
Moisture ingression
Changed interchain hydrogen bonding force & plasticization
Chemical reaction
Bond scission on main chains (backbones)
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10. AVERAGE WEIGHT GAIN % THERMO MECHANICAL PROPERTY VARIATIONS
No equilibrium of moisture absorption after 90 days
– Non-Fickian behavior (I)
Irreversible process (Chemical reaction).
THERMO MECHANICAL PROPERTY VARIATIONS
Young’s modulus and Flexural stress variation.
Variation of glass transition temperature (Tg).
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11. MOISTURE EFFECT ON INTERFACIAL ADHESION
Moisture has significant effect on the interfacial mechanics and is strongly correlate with the oxidation of CNF surface
Two classes of carbon fiber surface are considered
No surface modification (Model-I)
Modified with –OH (Model-II)
The interactions across the interface are purely non-bonding, i.e., VDW + electrostatic interactions.
Added water plays a role of plasticizer at the CNF/epoxy interface, and it leads to wider attraction region.
After moisture ingression, interfacial force is enhanced with strong fluctuation. Possible reason: enhanced hydrogen bond interaction. Local stress may break some hydrogen bonds (cluster) and leads to the fluctuation.
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12. SIMPLIFIED MODEL SYSTEM
(1)
Reaction I
C-O bond breaking for C from aliphatic and benzene are:
Ea ≥ 265 kJ/mol and ≥ 259 kJ/mol respectively
(2)
Reaction II
C-N bond breaking: Ea ≥ 191 kJ/mol
The barriers are very high. → Hydrolysis (Chemical aging) is very slow in the neat epoxy resin!
A structure (97% crosslinked) contains ~550 C-N bonds in the main chains(328 from curing reaction and others from initial structure). Meanwhile, it contains only ~ 80 C-O bonds (side chains are neglected).
Bond scission on C-N bonds is more crucial for mechanical property degradation.
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13. EFFECT OF C-N BOND BREAKING
Structures with different percentages of broken bonds
0.0%, 4.0%, 7.0%, 10%, 15%
3 configurations for each degree of bond scission
Creating broken bonds leads to decreased density
Percolation Threshold?
Assuming that Young’s modulus is linearly correlated with the degree of bond broken, there exists a critical degree at which the epoxy resin breakdown completely.
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14. HYDRATED MODELS H2O cnf/water/epoxy cnf-OH/water/epoxy
Water at interface
Water embedded into bulk
cnf/water/epoxy
cnf-OH/water/epoxy
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15. EXPERIMENTS – REVERSIBILITY
Objective: To study reversibility of epoxies after ageing → Chemical ageing
After drying the wetted epoxies at 90°C for 48h, the following experiments have been conducted
3-Point Bending
DMA
FTIR
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16. REVERSIBILITY: TG
Decline in Tg of 20°C from as-received (dry) to 49 days (wet) is due to the lowering of intramolecular hydrogen bonding forces and increased moisture concentration which acts as ‘plasticizers’.
Wetted
No. of days
Tg (°C)
238.22 42
234.29 50
235.20 82
234.59
Re-dried
Tg declines weakly with ageing duration – Weak chemical degradation?
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17. REVERSIBILITY: FTIR RESULTS
Weakly increased O-H stretching peak
There is residual moisture inside the sample even after 2-days of drying.
Bands (cm-1)
Assignment
OH stretching
CH stretching of the alkyl
C-C stretching in aromatic ring
C-N stretching (aromatic amines)
C-N stretching (aliphatic amines)
C-O stretching (aromatics)
Irreversible effect due to chemical ageing
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18. UV BARRIER POLYMER-CERAMIC COMPOSITES

19. FEATURES OF THE CERAMIC FILLERS
Tunable ~55% Transmittance capability
Lead-free transparent ceramic; Thickness 0.8 mm
Patent no. 2014/ A1
Potential applications: Complete UV absorption; UV absorption indication through color change; Optical Coating and filter for UV; Tunable electro optic ceramics; etc..
Advantages: Nontoxic, robust and thermally stable, block UV, transparent to NIR, low thermal conductivity, electro optic tunability

20. POLYMER-CERAMIC COMPOSITE
Ceramic amount
PE Neat 5%
10%
20%
Film thickness is ~ 160 
Film
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21. UV-VIS SPECTROSCOPY ANALYSIS
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22. WEATHERABILITY TEST CONDITIONS
Specimens kept in UV chamber for a 40 h and tested for their physical (crack) and chemical (degradation) properties.
Q: How long will it take to reproduce 5 years of sunlight artificially?
A: Assuming that sunlight in Singapore is similar to sunlight in South Florida (both are sub-tropical environments) and 1 Y of total UV ( nm) in Miami is 280MJ.
The formula is: kJ = irradiance x 3.6 x N hours
So the 1080 hours  1 year. To duplicate 5 years of weathering, the total time would be  5400 h or 225 days. This is a crude assumptions for a guide.
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23. MECHANICAL PROPERTIES OF THE COMPOSITE FILMS BEFORE AND AFTER UV ILLUMINATION
Sample
Max Tensile strength after UV irradiation
Neat 8%
decrease 5%
14%
increase
10%
18%
20%
11%

24. CONCLUSIONS:
In epoxy based composite immersed in moisture and temperature, their properties become irreversible, which is due to chemical ageing
In PE based composites, UV absorbing ceramic fillers improve the mechanical properties, UV resistance and suitable for harsh environment applications.
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25. Thank you!