Aligning α‐alumina platelets via uniaxial pressing of ceramic‐filled polymer blends for improved sintered transparency. Issue 6 (10th February 2020)

• Record Type: Journal Article
• Authors: Costakis, William J.; Schlup, Andrew; Youngblood, Jeffrey P.; Trice, Rodney W.
• Is Part Of: Journal of the American Ceramic Society. Volume 103:Issue 6(2020)
• Page Start: 3500
• Page End: 3512
• Publication Date: 2020-02-10
• Subjects: optical materials/properties -- rheology/rheometry -- alumina -- hot pressing; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.17044
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: Uniaxial warm pressing was used to align alumina platelet‐filled polyethylene‐based copolymer blends. The solids loading (30‐40 vol.%) and platelet diameter (1.2 and 11 μm) were varied to compare effects on viscosity, percent reduction, and final alignment. All ceramic‐filled thermoplastic polymer blends exhibited pseudoplastic behavior. Crystallographic alignment of green body samples was quantified by the orientation parameter ( r ) and grain misalignment angle (full width at half maximum, FWHM) obtained from rocking curve analysis. Blends with 11 μm diameter platelets displayed a higher temperature sensitivity constant, better flow properties, and higher alignment compared to blends with 1.2 μm diameter platelets. Optimal samples produced with blends containing 30 vol.% of 11 μm diameter platelets demonstrated an alignment of r = .251 ± .017; FWHM = 11.16° ± 1.16°. A sample with optimal alignment was hot‐pressed to transparency and obtained an in‐line transmission of 70.0% at 645 nm. The final alignment of this pre‐aligned hot‐pressed sample ( r = .254 ± .008; FWHM = 11.38° ± 0.54°) improved when compared to a non‐pre‐aligned sample ( r = .283 ± .005; FWHM = 13.40° ± 0.38°).