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There was a post in Seasoned Advice which piqued my personal interest (seeing as how I'm ABC myself). Rice cooker pots are by no means "cheap", so I thought I'd look into it myself in order to see if I could arrive to a definitive answer.

My initial search led me to this paper:

Porosity and hardness of long-grain Brown rice kernels in relation to their chemical compositions (.pdf backup)

...as well as these "specifications" (Note: Dupont has a disclaimer disqualifying their table as a "specification", basically due to data error tolerances/variability/lack of precision or control uniformity, but for lack of a better word...):

Properties Of Teflon™ Coatings (.pdf backup)

Mechanical Properties of Teflon® Coatings (.pdf backup)

Unfortunately, as far as I was able to determine, it seems that the properties enumerated by the study and the tables are not directly comparable (from a purely arithmetic perspective?), as the former derived "64.6 to 213.7 N" (which, if I'm understanding correctly, was given as Newtons — a unit of measure for force — for its measure of tensile and breaking strength, whereas of the latter sources, one had no quantitative measures at all and cited qualitative descriptors in-lieu of, and the other reported an ambiguous range — with no additional clarification of parameters save the "Scratch Resistance scratch master" — as "5.1kg–13.2kg", which is a mass measure.

As I understand it, when we talk about a material's "hardness" and "scratch susceptibility", the specific context needs to established in order to disambiguate the lexical term "hardness", which can apparently refer to a variety of distinct (but possibly) correlated material properties and characteristics. For example, "Hardness correlates linearly to Ultimate Tensile Strength through the empirical (although theoretically [un]explained[sic]) equation H=UTS/k".

According to the Encyclopedia of Materials: Science and Technology (2001)...

Scratch hardness is defined as the hardness of a material when it is scratched by a stylus dragged along its surface under a given load. Unlike pure indentation-based hardness tests, scratch hardness defines the resistance of material to plowing (i.e., a combination of indentation cum sliding) by a hard stylus...Many of the common tribological phenomena like sliding, abrasive, and cutting wear are characterized by a harder material plowing into the softer wearing material. Thus, for correlating the tribological performance of many materials, scratch hardness (Hs) is expected to be a better correlating parameter than the indentation hardness.

Unfortunately, I've gone about as far as my two-decade-old high school Physics B education is able to take me. It seems there are cases where we can strongly correlate such properties based on empirical, but I lack the requisite knowledge to apply such relationships to the specified context in any meaningful manner. Can someone kindly explain whether a definitive and quantitative or evidence-based answer can be derived from the given data? Or if not, exactly how indeterminate is it (i.e., can we extrapolate a probabilistic answer with some degree of confidence?). Thank you!

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If it were possible to predict things like scratch resistance from some list of first principles then there would be no need of the field of materials science nor its practitioners (like I once was).

It is such a complex business that the best you can do is to develop standard testing & characterization methodology so that meaningful data on things like scratch resistance can be collected. In the best case you could hope for, you could then derive useful general (semi-empirical) correlations between things like ultimate strength, yield strength, rockwell hardness, charpy impact, etc. and scratch resistance.

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  • $\begingroup$ You wouldn't happened to have worked with rice grains and Teflon coatings at any point during your career, would you? Haha. $\endgroup$
    – Arctiic
    Jun 17, 2023 at 3:12
  • $\begingroup$ Sorry, no! But I had a friend who worked in a rice mill's hull conveyor system and learned a lot about this from him. $\endgroup$ Jun 17, 2023 at 16:23

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