Polyethylene crystallization nucleated by carbon nanotubes under shear.

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Understanding polymer crystallization behavior is crucial for developing advanced materials.
• Carbon nanotubes (CNTs) offer unique properties that can influence polymer morphology.
• The effect of different types of CNTs (single-wall, few-wall, multiwall) on polyethylene crystallization under shear is not fully understood.

Purpose of the Study:

• To investigate the influence of single-wall, few-wall, and multiwall carbon nanotubes (CNTs) on polyethylene crystallization under shear.
• To analyze the structural changes and orientation of polyethylene chains in the presence of CNTs.
• To examine the thermal stability and morphological transformations of CNT-templated polyethylene crystals.

Main Methods:

• Polyethylene crystallization was induced under shear in the presence of various types of CNTs.
• X-ray diffraction (XRD) was used to measure polyethylene crystal d-spacings for (110) and (200) planes.
• Thermal stability was assessed by attempting to redissolve crystals in boiling xylenes, followed by morphological analysis.

Main Results:

• Polyethylene/CNT composites exhibited smaller crystal d-spacings compared to pure polyethylene.
• Polymer chains in the composites were observed to be oriented along the CNT axis.
• Single-wall carbon nanotube (SWNT)-templated polyethylene crystals retained their orientation even after transformation to an amorphous state in boiling xylenes, and SWNT crystal peaks were detected in polyethylene/SWNT fibers.

Conclusions:

• CNTs act as effective templates for polyethylene crystallization, promoting smaller crystal structures and axial alignment.
• SWNTs significantly enhance the thermal stability of polyethylene crystals, preserving chain orientation even under harsh conditions.
• The findings suggest potential for developing novel polymer nanocomposites with tailored properties using CNTs.