Barrier properties and abrasion resistance of biopolymer‐based coatings on biodegradable poly(lactic acid) films

Coated polylactic acid (PLA) films consisting of crosslinked‐chitosan/beeswax layer were prepared to improve barrier properties and abrasion resistance of the base substrate. The effect of crosslinking the chitosan layer on durability and barrier properties of the coatings was investigated. Crosslinked samples exhibited lower degree of swelling compared to uncrosslinked samples and 50% reduction in water vapor transmission rate (WVTR) compared to neat PLA films. The beeswax coating decreased the WVTR of chitosan‐coated PLA films significantly (by 100%). However, it had a marginal effect on the oxygen transmission rate. Water vapor transmission was less affected by abrasion than oxygen transmission for both uncrosslinked and crosslinked samples. The WVTR of crosslinked samples were retained even after being subjected to abrasion, whereas WVTR of uncrosslinked samples dropped by 50%. Results obtained using the Taber test method also show that the weight loss of crosslinked coatings are about 75% less than that of uncrosslinked samples and can withstand a greater number of cycles before rupture. These translucent‐coated films retained good barrier and mechanical properties along with providing improved abrasion resistance after crosslinking. This approach provides exciting new possibilities for expanding the use of biodegradable polymers in packaging applications. POLYM. ENG. SCI., 59:1874–1881, 2019. © 2019 Society of Plastics Engineers     

The effect of professor ethnicity and gender on student evaluations: Judged before met.

Ethnic minority academicians face a number of challenges in the “ivory tower.” One set of challenges arises from the racial stereotypes that others hold, and the current research investigates the stereotypes held by students before they even meet such professors. After providing college preparatory students with a CV of a professor (differing in their race—White, Black, or Asian; their gender—male or female; and their academic discipline—Science or Humanities), students evaluated the professor on measures of competence, legitimacy, and interpersonal skills. We found that students evaluated Black professors to be significantly less competent and legitimate than their White and Asian counterparts. Both Black and Asian professors were judged to have significantly less interpersonal skills than White professors. No gender main effects emerged. Professors in science were judged to be more competent and legitimate than professors in humanities. Very few interactions surfaced. We discuss our results in terms of previous stereotype research and the implications our results have for further compounding the challenges that Black professors face in academia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)