Author: ClaV
Date: 2015-07-28 07:06
Dear Silversorcerer,
You wrote 3 messages with many letters.
I will be happy to support my statements word by word, as long as it will work for your satisfaction (and/or understanding the science).
First of all, bakelite is a thermoset, a type of polymer materials produced by irreversible reaction of two monomers, one of which is multifunctional, so the system is heavily cross-linked, and as a result non-uniform (e.g. speckles/grains on your multiple photographs). It is important, since properties of thermosets are inferior in many aspects due to this non-uniformity, and bakelite is a textbook example.
For bakelite, the monomers are formaldehyde and phenol. The reaction is poorly defined and it does not lead to well-defined linear polymer chains (as with many thermoplastics, for instance ABS).
Second, in thermosets, some of the monomers typically do not completely react, which practically results in heavy smell of fresh bakelite. Formaldehyde is quite toxic and there are strict regulations in place for handling it.
Practically, it means that bakelite takes efforts to produce safely and also, importantly, to handle safely when freshly produced. It should just be one more reason why no one makes bakelite clarinets now.
Here is one interesting article to illustrate the point about the safety of bakelite production back then: http://www.intelligencer.ca/2008/12/06/bakelites-toxic-legacy-cant-be-left-to-simmer
Surely, old bakelite samples, that you handle, lost most volatile compounds over the years, but when scratched/machined, you get the unmistakable phenol smell.
Now to the inferior mechanical properties. Bakelite is not uniform and while generally strong (as expected from cross-linked polymers), the weak links form breakage points. As I mentioned, I have few bakelite barrels, some of them are chirped. Just for you (since you seem to like empirical evidence) I chirped one more - very easy to do, very poor material compared to grenadilla and decent plastic, like ABS. Again, that is what called inferior mechanical properties.
To make it more complicated for properties characterization, bakelite, as most of thermosets, is typically used with fillers: partially to reduce the cost and partially to alleviate some non-uniformity. One typical filler for bakelite is a wood dust. Another common filler used to be asbestos fibers, which give better properties in fact, but hardly a material of choice today.
Sure, better fillers can make bakelite a better material but at a cost; and most importantly there are better materials than bakelite, e.g. polyester, nylons, which give superior materials, for example as a polymer matrix (reinforced) with carbon fibers. These materials based on carbon fibers, I believe (and here is just my reasonable thinking), would be superior for clarinets, as well.
Now, if we get to the values for mechanical properties, the data for bakelite give the range, e.g. tensile strength 5-9 ksi (5,000-9,000 psi). Here for instance, page 19: http://engr.bd.psu.edu/rxm61/METBD470/Lecture/PolymerProperties%20from%20CES.pdf
For Delrin, manufacturers specify 9,000 psi: http://www.sdplastics.com/delrin/delrin%5B1%5D.pdf
The weak link (smallest values) would be more relevant for catastrophic failures. I will be happy to discuss it more.
Finally, there is a great difference between "not shrinking and warping" referring to the post-transformation of the item already made and shrinking upon molding. For the molding, with all the polymers, the shrinkage is substantial due to polymerization reaction (and effective "compactization") so it is quite challenging to make precise molding (quite relevant for plastic student clarinets). Again, I will be happy to answer your further questions in more detail.
Very briefly, there were not enough East German clarinets for students in USSR (they were quite expensive and were not produced in large enough quantities).
Post Edited (2015-07-28 07:13)
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The Clarinet BBoard
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