How Do They Make PVC Trim So Shiny And Smooth?

As anyone who has used PVC trim knows, the product is basically S4S, i.e. shiny and smooth on all sides.
As anyone who has ripped PVC trim also knows, the newly exposed surface is pretty rough.
Well, as of today I can attest that you can't just sand the exposed surface and get it anywhere close to the shiny and smooth surface of the uncut product - not that I really expected that I could.
However, I really didn't expect to see tiny voids show up - little circles like there were bubbles in the material. They can be sanded out, but you never know when some more might show up.
So how do they get such a smooth surface when they manufacture the product? At first I though that maybe it was a "molded product" but then I saw this at one Cellular PVC company's site:
"And because we make custom shaping knives, we can provide virtually any moulding style desired. "
So, how do they get the final surface so perfect? Why don't those little voids show up when they are milling the product?
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On 11/6/2011 8:27 PM, DerbyDad03 wrote:

Molded from the melt onto smooth surface will give smooth surface or it could be cast as a sheet continuously and run between smooth rollers.
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That doesn't explain "profiles" like brick mold or bead board.
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wrote:

Maybe because PVC extruded rather than "shaped"?
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On Sun, 06 Nov 2011 19:45:34 -0600, " snipped-for-privacy@att.bizzzzzzzzzzzz"

Bingo! The "knives" they talk about are actually the extrusion nozzles.
They also make PVC pipe the same way. It poops out of a die.
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On Nov 6, 9:59pm, snipped-for-privacy@aol.com wrote:

http://blog.versatex.com/Blog/bid/25430/Keys-to-Successful-Moulding-or-Milling-of-Cellular-PVC
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wrote:

http://blog.versatex.com/Blog/bid/25430/Keys-to-Successful-Moulding-or-Milling-of-Cellular-PVC
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There is a heavy duty foam core shaped to suit the final product and then those foam cores are extruded through a machine which applies a coating of PVC on the outside -- PVC trim is like an M&M candy... Crunchy on the outside and chewy on the inside...
If you need to "rip" PVC trim board down you are buying the wrong size for whatever application you are using it in...
Joints where PVC is end cut should be sealed with caulking both to seal the joint and stick it together... You shouldn't ever have a need to sand it smooth if you are using the material correctly...
You will notice that any sort of railing system made of PVC has actual PVC piping inside of it to provide the "structure" and be the load bearing bones inside...
~~ Evan
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Safety Warning: Do Not Eat.
--
Tegger

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...
Really?
So PVC trim comes in an infinite range of widths to fit every single application known to man? I didn't know that.
Check out Figure 4 at this site:
http://www.coastalcontractor.net/article/37.html
...

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Yup, it comes in many widths...
Your choice of the PVC material as the trim will dictate the range of sizes you will have available to use...
You can machine it to join pieces together but you would not want to leave a machined edge exposed, and you seal all the joints on the basis that you want to protect the building behind the PVC as if you left it without caulking and it develops a leak from any sort of mechanical damage you don't want the building behind the rot proof trim rotting out from underneath and the first sigh of trouble being the trim piece falling off and taking parts of the building with it...
~~ Evan
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So I assume that you are retracting your assertion that:
"If you need to "rip" PVC trim board down you are buying the wrong size for whatever application you are using it in..."
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