[Premium-Rx] Nylon gears

Thu Aug 21 21:30:10 EDT 2003

Well Barry, I just opened up my laser printer because I was curious too after your comment.  My printer is an older HP LJ III and has had plenty of use/ stays on all the time.  Most of the gears inside are carbon fiber... but I did notice two Nylon gears... and they have now yellowed.  They have not broken yet... but they are no longer pliable as when new.

I didn't put this in my last note due to the complexity of the issue, but the yellow color is the result of the formation of free radicals in the polymer.... free radicals indicate that some "ends" of the polymer chains have come lose... and are now charged.  As a side bar (but more related to the topic of this reflector).. .this can happen to transmission lines too (coax!) and the result is... a once very good dielectric material has degraded into a substance that is no longer so dielectric (and now brittle too!).  While this is not specifically germane to the printer gears, it does explain why receiving transmission lines get lossy over time, and transmitter feed lines have been known to explode!  

OZONE in particular promotes free radical formation and will destroy polymers faster than anything short of mere burning/ melting them!  Over time they will become very brittle as the chains are broken in the matrix.  I suspect this is causing your big gears to split (I'll bet the fractured surface looks like that of a broken rock).  

Toner actually is more of a help than a hurt... can actually lubricate the gears... but of course is a mess.  Graphite is an ok/ allowed lubricant for Nylon, but falls into that mess category too.... and of course should not be used inside radios... as it is conductive!  

In general, I really feel that you should NOT lubricate Nylon.  It, and other polymers like PTFE (Teflon) are naturally slippery...  most lubricants will cause more harm than good.  

Sincerely,

Dr. William J. Schmidt, II  K9HZ

"Collector of Edison Wind-up Phonographs... Do you have one for me?"
Email: bill at wjschmidt.com
Alternate Email: wmschmidt at charter.net
WebPage: www.wjschmidt.com

  ----- Original Message ----- 
  From: Barry Hauser 
  To: Dr. William J. Schmidt, II ; Premium Receiver List 
  Sent: Thursday, August 21, 2003 7:52 PM
  Subject: Re: [Premium-Rx] Nylon gears

  You frequently see nylon gears in laser printers and copiers.  They are often exposed to heat, toner and ozone.  How do those affect nylon? 

  I once contacted HP to ask about a suitable lubricant for the nylon gears.  They told me they used Dow Metal Assembly Paste, which is actually a molybdenum lubricant.  It's more jelly-like than greasy in consistency.  Didn't seem right so I stopped using it for that, but when rubbed and buffed into metal sliding parts works well to fill the pits and pores with moly.  The "goo" is not so much a lubricant as a vehicle for application.

  Used to be tempted to use petroleum jelly on nylon gears.  Is that one of the bad choices?

  In some of the big laser printers we have, some of the nylon gears are prone to splitting.

  Barry

    ----- Original Message ----- 
    From: Dr. William J. Schmidt, II 
    To: Premium Receiver List 
    Sent: Thursday, August 21, 2003 8:15 PM
    Subject: Re: [Premium-Rx] Nylon gears

    Much of the ability to restore the pliability and elasticity of Nylon can be gleaned from a simple understanding of the Nylon manufacture process.  It is, in fact an aqueous polymeric process of reacting a dimer and co-polymer agent in the presence of a catalyst.  Very often the catalyst for this process is TiO2.. which with water, stays occluded in trace amounts in the polymer structure.  The water molecules actually add to the pliability of the Nylon compound (whereas the TiO2 molecules act as stress points).  This is why rehydration after many years of "matrix drying" seems to rejuvenates Nylon.  Small molecule greases can penetrate the matrix too... and basis upon my comments in the next paragraph... can help or destroy the Nylon matrix.

    Nylon degrades by one of two basic methods... mechanical fracture or rearrangement of the structure.  We need not go too far down the mechanical fracture mode... but it is safe to say that the more solid impurities in the structure, the more likely a fracture/ failure will occur (screwed from the start!).  Rearrangement, "unbonding", or transformation is the worst case... and goes mostly unnoticed (except for possibly a color change in the worst case).  Light (UV in particular), heat, and acid all promote degradation of the polymeric structure to varying degrees by acting, again, as a catalyst to reactions.  The insertion of non-Nylon co-polymer compounds like a long chained hydrocarbon grease can cause an irreversible reaction to rearrange the polymeric structure... replacing otherwise strong Nylon cross links... with weaker links.  This process is almost always irreversible.

    Recipe for keeping Nylon usable:  Water/ hydration is good... warm water treatment works wonders.  Any acid compounds are bad... even those that occur in trace amounts in a lubricating medium like a grease will ruin Nylon.  Therefore natural lubricants (non acidic) will be preferred. Water based are best.   Keep Nylon away from heat and UV light.  Hydrocarbon lubricants are ok so long as they are pure.  Inorganic lubricants are ok too if the molecules are big (lithium compounds are preferred because they cannot absorb into the Nylon matrix due to their size).... and IF they do not contain acidic carriers.

    That should be enough.

    Sincerely,

    Dr. William J. Schmidt, II  K9HZ

    "Collector of Edison Wind-up Phonographs... Do you have one for me?"
    Email: bill at wjschmidt.com
    Alternate Email: wmschmidt at charter.net
    WebPage: www.wjschmidt.com

      ----- Original Message ----- 
      From: Gary Geissinger 
      To: premium-rx at ml.skirrow.org 
      Cc: Gary Mattie ; Dale Lister ; Skip Cubbedge 
      Sent: Thursday, August 21, 2003 11:10 AM
      Subject: RE: [Premium-Rx] Nylon gears

      Guys,

      Although nylon is generally considered to be compatible with both petroleum based and synthetic lubricants, I would be careful here.

      Nylon is closely related to benzene and therefore it degrades when exposed to benzene and compounds containing benzene such as benzene chloride.  Unfortunately benzene is a contaminant in many types of petroluem based lubricants. (It also is a contaminant in petroleum derived ethanol...that's a good reason why grain derived ethanol is the preferred additive to New Year's punch.)

      I bet a good synthetic (or vegetable) based lubricant might be a better bet.  Attached is a good compatiblity chart.

      The warm water idea is interesting..I may try that on the 8640 in the lab.  Just the gears though.

      Gary WA0SPM

        -----Original Message-----
        From: Jim Carrington [mailto:jcall11 at comcast.net]
        Sent: Thursday, August 21, 2003 1:22 AM
        To: premium-rx at ml.skirrow.org
        Subject: Fw: [Premium-Rx] Nylon gears

        Hi folks,
        I've been a quiet member of the group so far but decided to throw my 2 cents in here. I have several of the 8640B's with cracked gear problems and have talked with 2 people who also have tackled the cracked gears but in different ways. The first guy thought that the nylon had shrunk with time, causing the gear to crack around the shaft. His solution was to remove the damaged gear ,  glue the pieces back together (I forget if he used epoxy or super glue) and then carefully enlarge the shaft hole very slightly so it was a slide on fit to the shaft. He then glued the gear back onto the shaft and said it worked well. 
        The second guy thought that the cracking problem was caused by excessive force on the gears from old hardened grease in the mechanisms that the gears drive. He has had some success wrapping wire around the base of the cracked gear to keep it from cracking further ( I suppose after cleaning and relubing the mechanism) . Note, my own try at this with some fine steel wire was not successful as the wire broke when I tried to twist it tight. 
        I think I lean towards the glue it back together solution after cleaning and relubing but havent had a chance to try this yet. It might be a good idea to also soak the pieces in water first before glueing. 

        Regards
        Jim Carrington
        KD6JTY

        ----- Original Message ----- 
        From: john phillips 
        To: premium-rx at ml.skirrow.org 
        Sent: Wednesday, August 20, 2003 4:47 PM
        Subject: [Premium-Rx] Nylon gears

        Hi Guys:
        Nylon needs to have moisture in its chemistry to stay srong & resilient. Age 
        drives out the moisture and the stuff gets very brittle. Model airplane builders discovered this decades ago and there have been instances of shattering props. 
        So, they would place the props in warm water for 24 hours or so and restore the moisture content and a return to a non-shattering state. 

        So I would think the same could be done for the gears under recent discussion if otherwise they are in good condition. By good condition I mean not cracked. If its an old gear it looks good but does not have the strength it had due to drying out. Give it the H2O treatment to preserve its continued strength.

        For what its worth. 

        Cheers, 
        John Phillips
        VE6XI

------------------------------------------------------------------------

        _______________________________________________

        Premium-Rx Mailing List
        To Post: premium-rx at ml.skirrow.org
        For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx

--------------------------------------------------------------------------

      _______________________________________________

      Premium-Rx Mailing List
      To Post: premium-rx at ml.skirrow.org
      For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx

----------------------------------------------------------------------------

    _______________________________________________

    Premium-Rx Mailing List
    To Post: premium-rx at ml.skirrow.org
    For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/premium-rx/attachments/20030821/90d69f67/attachment.htm