Can plastic "rot" or "rust"?
 

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
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Can plastic "rot" or "rust"?
 

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.

Can plastic "rot" or "rust"?
 

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

Can plastic "rot" or "rust"?
 

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.

Jeff:
I would take the plastic tray back to Sears and ask for a replacement. My guess was it was defective from the start.
If this is happening to you, then I expect it's happened to a lot of people who own that same humidifier, and Sears probably realizes the trays weren't suitable for their application. I expect that if you show them the old one, they'll give you a new one, and it'll be made of a different plastic.

With utmost respect for Paul's knowledge and experience, some plastics are dyed (like fabrics) and some are pigmented (like paints) and still other plastics are the colour they are because they have printing ink on them.

Nylon or polyester carpet fiber, for example, is most often dyed to it's final colour. That's why when you spill bleach on such a carpet, the bleach will take the colour out of the carpet pile. If the plastic had the colour all the way through it, as was suggested, then bleach wouldn't affect the colour of the carpet pile because it couldn't penetrate into the plastic. The bleach could only affect plastics that are dyed to their final colour after they've been formed into their final shape, and that means that the colour is entirely on the outer surface of the plastic. It would be exactly the same story for plastic fibers that are woven into clothing fabrics, like polyester shirts or acrylic knit mittens.

Bleach won't harm a plastic telephone (for example) because that plastic is pigmented so the colour is all the way through the plastic, not just on the surface.

I think what Paul might be thinking is that in order to make transparent green plastic (for example) they melt a few green plastic pellets together with a lot of clear plastic pellets, and the result is a plastic that's still transparent, but has a greenish colour to it. But, the green plastic pellets they used were made of the very same plastic as the clear ones, it's just that they contained a lot of green pigments. So many green pigments, in fact, that the green plastic pellets were opaque as a result.

Titanium dioxide is a mineral that's pulverized into a fine powder and used to make paints, plastics, leather and even paper, white or whiter in colour. This web site shows the various types of titanium dioxide pigments that DuPont sells for colouring plastics:

http://www2.dupont.com/India_Country...tics_prdt.html

The Ti-Pure pigments sold by DuPont that are recommended for exterior use are coated somehow. The problem is that titanium dioxide acts as a catalyst in the reaction by which plastics deteriorate from UV light from the Sun, and so DuPont coats some of it's titanium dioxide pigments to prevent them from doing that. What kind of coating it is or how it works is something I don't know, and I suspect it's a trade secret.

Can plastic "rot" or "rust"?
 

In article ,
nestork wrote:

However, part of any designer's job is to ensure that the materials
they're using for their humidifier are appropriate to the job, and if
your plastic water tray has "rotted" out, then it wasn't an appropriate
material right from the get go.

Jeff-

Nestork may be right. It would be worth checking with Sears to see if
they will do anything for you. Success might depend on finding a Sears
manager who believes in customer satisfaction.

Before you do, check with Sears Parts to see if the tray is still
available. http://www.searspartsdirect.com/partsdirect/index.jsp You
will need the model number, which should be in the form of 123.456789.
The first part identifies the source, which might be 119 (Frigidaire) or
110 (Whirlpool) for example.

Fred

Can plastic "rot" or "rust"?
 

Fred McKenzie wrote:
In article ,
nestork wrote:

However, part of any designer's job is to ensure that the materials
they're using for their humidifier are appropriate to the job, and if
your plastic water tray has "rotted" out, then it wasn't an appropriate
material right from the get go.

Jeff-

Nestork may be right. It would be worth checking with Sears to see if
they will do anything for you. Success might depend on finding a Sears
manager who believes in customer satisfaction.

Before you do, check with Sears Parts to see if the tray is still
available. http://www.searspartsdirect.com/partsdirect/index.jsp You
will need the model number, which should be in the form of 123.456789.
The first part identifies the source, which might be 119 (Frigidaire) or
110 (Whirlpool) for example.

Fred


Thanks, I'll give it a try sust for S's and G's.

About ten years ago I took a failed Craftsman lawn sprinkler back to the
local Sears store and they did give me a free replacement. The
replacement didn't have the Craftsman name on it, so I asked the nice
guy I was dealing with if it still came with a "lifetime warranty" and
was told it didn't and that they no longer made sprinklers bearing the
Craftsman name. Can't complain, I never thought I'd live this long
anyway. (G)

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Can plastic "rot" or "rust"?
 

On 6/3/2013 11:56 AM, 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

Johnstone Supply sells an aerosol spray can of "Pan Spray" it's a sealer
for leaking plastic or metal drain pans in AC evaporators and I've found
many other uses for it. It applies as a layer much like the undercoat on
cars and will seal any sort of unpressurized container for water. If you
cant find a replacement pan, it may be some help. ^_^

http://www.johnstonesupply.com/store...ords=pan+spray

http://tinyurl.com/m82ekty

TDD