The quartz crystal microbalance (QCM) was used to measure the time-dependent mechanical properties of an alkyd resin throughout the transition from its application as a liquid to the formation of a solid film. Three different regions of curing were observed, corresponding to solvent evaporation; early stage curing, where the mass increases as oxygen is incorporated into the film; and long-term curing, where the mass decreases as volatile compounds are released. Mechanical property changes obtained at 15 MHz with the QCM were correlated with measurements at much lower frequencies utilizing traditional dynamic mechanical analysis. These mechanical property changes were in turn correlated to chemical changes tracked with Raman spectroscopy. From the temperature dependence of the curing process we obtain an effective activation energy of 4.1 kcal/mol.

Please cite this article as: L.F. Sturdy, M.S. Wright, A. Yee et al., Effects of zinc oxide filler on the curing and mechanical response of alkyd coatings, Polymer (2020), doi: https://doi. AbstractThe mechanical properties of an alkyd resin filled with zinc oxide pigment were studied at different concentrations over a wide range of time scales using dynamic mechanical analysis, quartz crystal rheometry and nanoindentation. The motivation for this work stems from the interest in accessing the long-term properties of paint coatings by studying the mechanical properties of historic paints. In this foundational work, we compare three different modalities of mechanical measurements and systematically determine the effect of pigment filler loading on the measured properties. Quantitative agreement between the methods is obtained when the characteristic time scales of each of the methods is taken into account. While nanoindentation is the technique most readily applied to historic paint samples, the rheometric quartz crystal microbalance (rheo-QCM) is the best suited for obtaining mechanistic information from measurements of paint properties over time, provided that appropriate thin-film samples can be produced. In these studies we find that ZnO increases the rate of oxidation of the alkyd during the initial stages of cure by an amount that depends on the ZnO content. J o u r n a l P r e -p r o o f Journal Pre-proof 2. Materials and Methods 2.1. Materials The alkyd films were prepared from Gamblin Artists Colors (Portland, OR) Galkyd mixed with Fischer Z50 zinc oxide ranging from 0.05 to 0.60 wet weight fraction. When necessary to change 2 J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof 7 J o u r n a l P r e -p r o o f Journal Pre-proof Thermogravimetric (TGA) experiments were conducted on naturally aged 5-month-old alkyd samples for four of the zinc oxide filler loadings listed in Table 1 to confirm the amount of zinc oxide pigment present relative to the binder after solvent evaporation. These results are shown in Figure 8 J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof -Zinc oxide accelerates the oxidative curing of alkyd paints. -Consistent results obtained with nanoindentation, dynamic mechanical analysis and high frequency rheometry. J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof Declaration of interest: none J o u r n a l P r e -p r o o f Journal Pre-proof

Bloom's taxonomy is a classification of learning objectives originally developed for general educational purposes. The taxonomy was subsequently revised to expand beyond cognitive processes and to include an additional knowledge dimension. The revision was prompted by psychometric measurements indicating inconsistencies in the original taxonomy, and the revised taxonomy has been adapted for use in many disciplines. However, biology education researchers and practitioners continue to use the original taxonomy despite the concerns of validity. To facilitate the use of the revised Bloom's taxonomy in biology, we developed a discipline‐specific rubric from an analysis of assessment items from diverse biology disciplines.Implicit learning objectives of 1,432 assessment items were coded by two researchers. Items were collected from AP Biology, MCAT, and both introductory and advanced undergraduate biology courses. A biology‐specific rubric was generated using the revised taxonomy as a model. Problems were coded independently by two raters in batches of 50–100, followed by a consensus process. After coding 831 items, a revised rubric was developed and tested on the remaining 601 items. Inter‐rater reliability was 0.76 and 0.70 (Cohen's κ) for the cognitive‐process and knowledge dimensions respectively.Using thematic analysis as the methodology over two versions of our rubric, we identified distinctive features among biology assessment items that define the six cognitive processes and four types of knowledge in the revised Bloom's taxonomy. Quantitative analysis indicates that our data set contains problems mostly in the remember or understand categories (43.9% and 37.3% respectively) but rarely in the apply, analyze, evaluate, or create categories (7.0%, 5.2%, 4.7%, 2.0% respectively). These results are aligned with existing biology education research literature using the original Bloom's taxonomy. In the knowledge dimension, factual, conceptual, and procedural knowledge are over‐represented (38.4%, 48.7%, 12.8% respectively), with essentially no metacognitive knowledge (0.2%). This suggests a potential area for change in biology education, as metacognition is critical to how people learn.We performed statistical analyses on the 601 items coded with our revised rubric to examine the Bloom's taxonomy framework. Contingency analysis indicates that the cognitive processes and knowledge dimensions are not independent (χ2 = 249.05, df = 10, p < 0.0001). Correspondence analysis identifies two components that account for 100% of the inertia or variation in how the two dimensions are related, with three distinct clusters of knowledge and cognitive process: factual knowledge with the remember cognitive process, procedural knowledge with the apply cognitive process, and conceptual knowledge with the remaining four cognitive processes. Together, these results provide a two‐dimensional, non‐hierarchical framework of Bloom's taxonomy for use of in biology.Support or Funding InformationThis project was supported in part by an institutional award for undergraduate education from the Howard Hughes Medical Institute and the Office of Undergraduate Research at Northwestern University.