amy huang – newton north high school akhil meka – chelmsford high school professor marilyn minus
TRANSCRIPT
Graded Architecture Composites
Amy Huang – Newton North High SchoolAkhil Meka – Chelmsford High SchoolProfessor Marilyn Minus
Background
Materials Science and Engineering, William D. Callister Jr, Wiley Schematic courtesy of Jessica Faust
Lamellar crystals
Hybrid particles with lamellae (confined)
Semicrystalline matrix comprised of spherulites
Composite material
Alumina plateletAlumina with CNT crystal seeds
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
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.
Processing
Actual representation of powder after filtering
Syringe
Beaker
Hot Plate
Processing
Melt Film
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
Actual representation of film after melting
Temperature Profiles
Undercooling/ΔT
DSC and X-Ray Results
Alumina Particle Solution
Temperature(°C)
Tm (°C)𝝙H (J/g)
(ΔH*PP = 207 J/g)XC, DSC
(%)
6-65 165.4-168.0
96-131.7 47.3-63.6
Lamellae Crystallization=XC, XRD-XC, DSC
Mechanical Testing
Mechanical testing performed by an Instron machine
Mechanical TestingAlumina Particle
Solution Temperature
(°C)
Modulus, E
(MPa)
Tensile Stress, σ
(i.e., Strength)
(MPa)
Elongation, ε(%)
6 778.9 ± 46.7 29.9 ± 0.8 1055.4 ±
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 31.1424.8 (only
one sample tested)
51.2 895 ± 30.9 35.3 ± 0.7 36.9 ± 17.1
bubbles
scratches
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
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.
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.
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.
AcknowledgementsSpecial thanks to: ● Professor Marilyn Minus● Jessica Faust, Undergraduate Research
Assistant● Heng Li, Graduate Research Assistant● YSP Staff
o Claire Duggano Maddy Legero Maureen Cabrera
Funding for this research project was provided by the Air
Force Office of Scientific Research (AFOSR FA 9950-11-
1-0153) and the National Science Foundation (NSF
CMMI-1351657)
Thank you! Any Questions?