1. Graded Architecture Composites
Amy Huang – Newton North High School
Akhil Meka – Chelmsford High School
Professor Marilyn Minus
Graded Architecture Composites

2. Background Semicrystalline matrix comprised of spherulites
Lamellar crystals
Composite material
Hybrid particles with lamellae (confined)
Amy
Explain: spherulites; CNTs have been shown to induce crystallization; CNTs are ONLY being used to induce crystallization; looking for a film with high toughness (modulus, strength, and elongation)
Alumina platelet
Alumina with CNT crystal seeds
Materials Science and Engineering, William D. Callister Jr, Wiley
Schematic courtesy of Jessica Faust

3. Materials
Polypropylene (MW = ~250,000 g/mol) dissolved in Xylene at 140 °C
Hybrid particles (Alumina platelets and single-walled carbon nanotubes) in Dimethyl formamide at varying temperatures
Akhil

4. Our Focus
This study is aimed at understanding the appropriate solution crystallization conditions under different rates of cooling for the solvent in order to optimize the growth of polypropylene crystals on hybrid particles in a graded composite.
Akhil

5. Actual representation of powder after filtering
Processing
Syringe
Actual representation of powder after filtering
Beaker
Hot Plate
Amy
Explain: run through step-by-step; spherulites in film
Ignore: solvent/solvent problems
****ADD LABELS

6. Processing Uniform Dispersion Melt Film Mechanical Testing
Hot Plate, T = 180°C
Glass Slide
PP Film
Heavy Preheated Steel Plate
Film is heated to 180°C for 1min 30sec and pressed into a thin film
Mechanical Testing
Uniform Dispersion
Amy
Explain: run through step-by-step; less spherulites
Melt the spherulites, but reformed
Take powder picture and show them
Actual representation of film after melting

7. Temperature Profiles
Undercooling/ΔT
Akhil

8. Alumina Particle Solution Temperature
DSC and X-Ray Results
Alumina Particle Solution Temperature
(°C)
Tm (°C)
𝝙H (J/g)
(ΔH*PP = 207 J/g)
XC, DSC (%)
6-65
Akhil
Differential Scanning Calorimetry
***1 ROW USE RANGES (BOX AROUND ENTHALPY AND %), BOX CRYSTALLINITY IN XRAY, TEXT BOX ABOUT CONFINED (XC DSC- XC XRD), SCHEMATIC ABOUT CONFINED CRYSTAL
Lamellae Crystallization=XC, XRD-XC, DSC

9. Mechanical Testing Mechanical testing performed by an Instron machine
Amy
Transition: After confirming that the crystals we wanted were there…
Explain: performed mechanical testing on an Instron machine at 10mm/min

10. Alumina Particle Solution Temperature
Mechanical Testing
Alumina Particle Solution Temperature
(°C)
Modulus, E
(MPa)
Tensile Stress, σ
(i.e., Strength)
Elongation, ε
(%) 6
778.9 ± 46.7
29.9 ± 0.8
± 746.3
20.1
746.3 ± 34.6
27.5 ± 0.1
63.1 ± 51.9
38.3
664.1 ± 39
27.6 ± 4.9
511.3 ± 479.9
41.3
955.5 ± 130.8
34.1 ± 2.4
85.1 ± 67
45.5
811.7
31.14
24.8 (only one sample tested)
51.2
895 ± 30.9
35.3 ± 0.7
36.9 ± 17.1
scratches
bubbles
Amy
Explain: interest is primarily in the modulus and the yield strength; there is a significant increase in modulus; however, there are no consistent trends in the yield strength due to processing inconsistencies; some elongation indicates that the material retains high ductility

11. Mechanical Testing Most samples had similar degrees of undercooling
The area with the same degree of undercooling exhibits a trend in the elastic modulus
Trend is associated with the cooling rate
Amy
Explain: difference between rate and undercooling

12. Key Results
DSC crystallinity values, based on crystal melting, showed similar results regardless of crystallization conditions.
Greater crystallinity measured by X-ray analysis as compared to DSC confirms that confined crystals exist in the samples, which is consistent with the interphase morphology.
Slower cooling rates were associated with higher particle injection temperatures.
Defects present during film melt-processing procedures limit strength and elongation trends in the films.
Akhil

13. Conclusion
This study shows the impact of solution crystallization conditions on the formation of interphase polypropylene crystals.
Changing the particle injection temperature allows for control of the cooling rates in the final solution.
Slower rates allow the crystals more time to fully develop and mature, contributing to better mechanical properties of the film.
Coupled DSC and X-ray analysis confirmed the presence of confined interphase crystals proving that this is a viable technique for processing hybrid particles useful in graded film architectures.
Akhil
Have four things to say, just abbreviate

14. Future Work/Recommendations
Improvement in the melt processing for final films improve consistency and reduce defects such as air bubbles and presence of dust particulates.
Increase the sample size for data collection in order to eliminate outliers improve accuracy of resultant trends.
Particle injection rate was kept consistent in this work. Future studies should add variation to this factor to further explore its effect on crystallization and/or properties of the subsequent film.
Refine the overall experimental set-up to reduce sources of error such as contamination of the solution or environmental exposure.
Amy
Have 4 things to say, just abbr.

15. Acknowledgements Special thanks to: Professor Marilyn Minus
Jessica Faust, Undergraduate Research Assistant
Heng Li, Graduate Research Assistant
YSP Staff
Claire Duggan
Maddy Leger
Maureen Cabrera
Funding for this research project was provided by the Air Force Office of Scientific Research (AFOSR FA ) and the National Science Foundation (NSF CMMI )
Amy

16. Thank you! Any Questions?