Bob,
Thanks! Interesting history. This plus Brian's!
I learned something new in this whole discussion - I did not realize that
Bakelite was machinable . I just thought it would smoke and burn if you
hit it with a mill. Is the feed & speed published somewhere?
I have an old Dumont scope that spent 20 years in the basement in Southern
Indiana where the humidity gets nasty. All the knobs have white fuzz on
them. Something apparently likes to munch on whatever plastic they are made
from. Scope still works [but not as well as the much newer Tek!]
Best regards
Steve C
From: Bob Landman [mailto:[log in to unmask]]
Sent: Saturday, June 23, 2012 10:57 AM
To: TechNet E-Mail Forum; Steven Creswick
Subject: Re: [TN] DH 99 Bakelite laminate - NTC
Hi Steve,
I don't believe so. I have a large sheet of it (1/2" thick) in my machine
shop in my cellar (old Victorian farm house with granite boulder foundation
which does get humid and moldy on the walls). The bakelite is still as
pristine as when I purchased it back in CA in the 1980s from McMaster-Carr.
I used the stuff to make what we called a T-format spectrofluorometer - the
Bakelite surrounded the sample compartment and the two photomultiplier tubes
as it made an excellent opaque thermal insulating compartment. The quartz
cuvette was placed in a square block of OFHC copper bonded to and
heated/cooled by a thermoelectric plate via a feedback loop from a
thermocouple that measured the water temp.
My customers (scientists) were measuring the intrinsic viscosity of neuronal
cell membranes using a very cleverly designed fluorescent probe molecule
that was absorbed into the membranes. Polarized UV light illuminated the
solution and if the fluorescent probe molecules tumbled quickly, the emitted
visible light was depolarized. The signals from two PMs with polarizers
oriented 90 degrees to each other were then processed to yiled a log ratio
which was the measure of the fluidity of the membranes. Couldn't have done
it without Bakelite.
I found in an old text "Handbook of Engineering Fundamentals" edited by Ovid
Eshbach (2nd ed. 1952) the following electrical properties (chp 13- p73)
Bakelite, wood molding mixture 17.7 to 21.6 Kv per mm, 1X10(12) volume
ohm-cm, 4.5 to 5.5 air unity (?) specific inductive capacity
Bakelite, asbestos molding mixture up to 9.8 Kv per mm, 4X10(11) volume
ohm-cm,
Bakelite, Micarta-213 (I think this is what I have) up to 31.4 Kv per mm,
5X10(11) volume ohm-cm, 5 air unity (whatever that is!)
(volts per mil, multiply Kv per mm by 25.4)
References from General Bakelite Co which Baekeland founded in 1910
Ah, the good old days....
Bob
_____
From: Steven Creswick [mailto:[log in to unmask]]
To: [log in to unmask]
Sent: Sat, 23 Jun 2012 07:28:43 -0500
Subject: Re: [TN] DH 99 Bakelite laminate - NTC
Bob,
Is Bakelite a nutrient to fungus growth? I seem to recall seeing fuzzy
white stuff growing on old O-scope knobs stored in a damp basement for a
number of years. Possibly the knobs were not Bakelight..
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Friday, June 22, 2012 12:29 PM
To: [log in to unmask]
Subject: Re: [TN] DH 99 Bakelite laminate
McMaster-Carr carries what to me is the equivalent (I have purchased large
sheets of the stuff).
See http://www.mcmaster.com/#garolite/=i38d13
They call it Garolite
Bakelite is named for Leo Baekeland who invented the stuff. Us physics
types used a ton of it over the years as it machines easily, does not dull
cutting tools. http://en.wikipedia.org/wiki/Leo_Baekeland
Here are collections of items made from the stuff
http://www.amsterdambakelitecollection.com/
http://kaufmann-mercantile.com/bakelite/
A book on its properties
http://pubs.acs.org/doi/abs/10.1021/ie50308a012
A lot more on it from ACS
http://portal.acs.org/portal/acs/corg/content?_nfpb=true
<http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTI
C> &_pageLabel=PP_ARTIC
LEMAIN&node_id=924&content_id=WPCP_007586&use_sec=true&sec_url_var=region1&_
_uuid=82c1c58c-ec86-4aab-afc2-2949d2bc9b01
Bob Landman
H&L instruments, LLC
_____
From: Mike Fenner [mailto:[log in to unmask]]
To: [log in to unmask]
Sent: Fri, 22 Jun 2012 06:41:04 -0500
Subject: Re: [TN] DH 99 Bakelite laminate
Bakelite is/was a brand name for one of the earliest synthetic polymers,
it's a phenolic resin.
It's likely that what is meant by 'Bakelite laminate' is paper phenolic,
Bakelite being a brand name that tended to be used as a generic term.
(like
Gas , Xerox, Hoover etc)
Early PCBS were made from layers of paper impregnated with phenolic resin,
and was replaced by glass epoxy years ago. It lingered in mass market
stuff
into at least the late 1970s as it was cheap. FR2 would likely be a
functional equivalent, a proper PCB guy would probably know, but you might
need to find an old timer to understand the question. Or try googling of
course!
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger M Unwin
Sent: Tuesday, June 19, 2012 3:38 PM
To: [log in to unmask]
Subject: [TN] DH 99 Bakelite laminate
Hi TechNet,
Does anyone know if DH 99 Bakelite laminate is still available, or what
a modern equivalent might be ?
The drg that specifies it is dated 1973, and is for an Antenna of some
type.
Many Thanks
--
Roger M Unwin
P+M Services (R) Ltd Tel : 01706 815212 Fax : 01706 818636
http://www.p-m-services.co.uk
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