Bisel REU 2014 poster

Tucker Bisel,1,2 Ching-Chang Chung,2 Jacob L. Jones2 1. Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634

2. Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695

Investigation of Phase Transitions and Relaxation Events of Polymers and Barium Titanate Ceramics Using Dynamic Mechanical Analysis

• Dynamic Mechanical Analysis (DMA) is useful for observing relaxation events and phase transitions in various materials

• Phase transitions and relaxation events reveal changes in the physical characteristics of materials

Introduction DMA Polymer Results

Objectives

• Run DMA on four polymers, polyethylene terephthalate (PET), polypropylene (PP), low density polyethylene (LDPE), and high density polyethylene (HDPE) at select frequencies while increasing temperature

• Prepare samples of barium titanate (BT) and analyze using DMA at select frequencies while increasing temperature

• Investigate characteristic relaxation events and phase transitions of ceramics and polymers

Conclusions

• Polymers and ceramics show distinct differences in internal relaxation behavior and phase transitions

• Differences in physical characteristics give rise to the observed differences in behavior

• α and β relaxations were observed at 75˚C and 0˚C in LDPE and at 50˚C and -10˚C in HDPE – α relaxations result from molecular reorientation in the crystalline

regions of the polymers – β relaxations may result from molecular chain motion in the

regions that connect amorphous and crystalline regions of semi-crystalline polymers2

We acknowledge NSF support for the REU site on Advanced Materials for Environmental Sustainability under grant EEC 1156762.

Methods

Sample Preparation:

• Polymer sheets were ordered from McMaster-Carr

• BT samples were made using powder from Alfa-Aesar – Uniaxially pressed in a 10 x 10 mm die at 7 MPa – Isostatically pressed at 250 MPa – Sintered at 1350˚C for 4 hours

• Using a wire saw, polymer and BT samples were cut into approximately 1 x 3 x 15 mm bars – BT samples were annealed for 4 hours at 650˚C after cutting

• Samples were assessed to confirm the material’s identity: – BT was assessed for purity using x-ray diffraction – Polymers were assessed using thermomechanical analysis to

determine melt temperature

Sample Testing:

• DMA tests were run using a PerkinElmer DMA 8000 in single cantilever mode, heating at 2˚C/min

• Data was collected for storage modulus (stiffness) and Tan δ (mechanical loss)

• Four frequencies were tested during each run: 0.1, 1, 10, and 30 Hz for polymers and 0.1, 0.5, 1, and 10 Hz for BT

• The glass transition for polymers was taken as the peak in Tan δ

LDPE

HDPE

PET

PP

BT

Samples:

DMA - single cantilever mode

References

1) Cheng, B.L., Gabbay, M., Fantozzi, G. (1996). “Anelastic relaxation associated with the motion of domain walls in barium titanate ceramics”. Journal of Materials Science, 31 (15), p. 4141.

2) Jeziórska R., Zielecka M., Gutarowska B., and Żakowska Z. “High-Density Polyethylene Composites Filled with Nanosilica Containing Immobilized Nanosilver or Nanocopper: Thermal, Mechanical, and Bactericidal Properties and Morphology and Interphase Characterization”. International Journal of Polymer Science, vol. 2014, Article ID 183724, 13 pages, 2014. doi:10.1155/2014/183724

• Polymers displayed frequency dependence in the onset temperature of relaxation events and phase transitions

• BT showed less frequency dependence during phase transitions (P1 and A1) than polymers

• The ferroelectric to paraelectric phase transition in BT at 125˚C resulted in the P1 and A1 peaks1

• Thermally activated domain wall motion in BT resulted in the R1

peak1

DMA Ceramic Results

Tan δ data was smoothed for clarity Tg = glass transition temperature