On Jun 3, 9:04*pm, Paul Drahn wrote:
On 6/3/2013 10:16 AM, Frank wrote:



On 6/3/2013 12:56 PM, jeff_wisnia wrote:

The Craftsman humidifier I'd installed on the air handler of our home's
heat pump HVAC system started dripping water. I assumed that the float
valve which controls the water level in the plastic tray which wets the
motor driven rotating sponge drum had gotten leaky and wasn't shutting
off properly.

Much to my surprise, the float valve was fine, but the bottom of that
tray was "rotting through", and with a slight push my fingertip went
right through it.

The tray is molded from a hard gray plastic and the bottom which rotted
is about 3/32" thick. The rest of the tray is still hard as a rock.

The water in it was a dirty brown color and there was a fair amount of
brown "mud" in there too.

Might be my fault for not taking it apart and cleaning it more often,
but I'm still amazed that the plastic gave out that way.

BTW, I installed that humidifier about 23 years ago, so I'm not
complaining about "short life", just surprised to see "rotting" of
plastic. I hope some of the plumbing pipes in our home don't suffer the
same fate.(G)

Jeff

Depends on the type of plastic and exposure to light and chemicals.
Plastic degrades in many ways but usually it is scission of the polymer
chains and loss of properties. Since the surface gets attacked first it
may form a degraded coating. Rest assured that your plumbing pipes are
different plastic, not that it makes them have any longer lifetime.

I had one of those Craftsman humidifiers in my old house and am
surprised yours lasted that long. I remember having to constantly clean
out the residue. My current house has an Aprilaire which only needs a
pad changed every year or so but needs overflow to go to a drain or
French drain in my case.

Frank is correct about what happens to plastic. However, plastic resin
that is not natural color contains a separate resin with color. They are
mixed prior to molding and then when melted for injection, they are
stirred together by the molding machine. Either or both may be breaking
down. Or the color may not be compatible with the pan resin. If exposed
to ozone or UV, both color and the pan resin must have protection for
the polymers.

Paul- Hide quoted text -

- Show quoted text -

The color concentrates are usually pigments dispersed in the same
resin.
Lots of other materials like toughening agents, stabilizers and
fillers can be added to the mix.
What is important is that the producer subjects the final part to end
use conditions. You can run accelerated aging tests. Unfortunately
defects may not show up until years of end use.