colored upvc profiles

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colored upvc profiles

Postby nabilshihadeh on Mon Apr 11, 2005 11:51 am

we produce white pvc compounds for shutters profiles which are well ,with excellent dimentional stability,however ,when produced in bronze"champaign"color the shutters once at site and especially on the southern facade tend to warp.the pigment used is a mixture of silver,chrome yellow,red oxide and carbon black,the stabiliser system is a lead phsphite.wounder if the use of uv stabilizers will solve the problem.any suggestions,appreciate your help.
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Postby Louis on Mon Apr 11, 2005 12:58 pm

Coukld it be related to the BTU or Heat Absorption level of the new compound? Try setting up a test where you uses lamps to simulate the sun and take temperature readings of the extrusions.

Other than that, I can't see why a different additive would change the internal stress in the part enough to affect warpage. Unless of course your processing paramaters for that compound are drastically different.


Hope that helps


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Postby DwightDixon on Mon Apr 11, 2005 7:53 pm

The darker color absorb more of the sunlight resulting in higher temp and therefore the shutters will warp due to the extruded in stress. If you can reduce the stress, you may be able to get away with it, but I would not bet on it. it will be hard to control. Your formulation will have to be modified to give a higher Tg by the use of high temperature modifiers. A bolder choise would be to use CPVC like they do in hot watter pipes. The sun is sure hot in Jordon.
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Postby Skip on Mon Apr 11, 2005 11:16 pm

Even in the USA, darker colors are usually co-extruded with a "capstock formulation", containing the darker color, higher stabilizer levels,& UV absorbers, acrylic process aids, and maybe another resin than PVC----such as ASA. The substrate can be a lower cost formulation--usually 80-90% of total thickness. You might try to contact the Vinyl Siding Institute, Div. of SPI (they have a web site) to see if they have any publications on capstock technology. Many papers have been presented at SPE ANTECS on this subject.
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Postby DwightDixon on Tue Apr 12, 2005 7:47 am

Using cap stock is a great way to increase the exterior durability of the siding. Put the high price UV additives only in the area of the siding which needs them. Arylic and ASA have much better UV resistance than PVC. However; the man says his problem is immediate warping of the siding due to the hot sun in Jordon only on the darker color siding. As long as the color stays the same, the temperature the siding will rise to as a result of the sun will be the same and that is the cause for his problem. A higher temperature resistant formulation for the bulk of the siding or reduced extruded in stress are the only cures that matter for this problem. If the siding fails during the first summer due to warpage it never gets old enough to fail due to UV degradation.
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Postby Len2 on Mon Apr 18, 2005 7:35 am

Specific pigments can and do cause excessive warping of plastic parts. Classic example is phthalo blue in HDPE straws...the blue stripe is always spiral shaped around the barrel of the straw, while a red stripe can easily be made straight, a non-phthalo blue will make a straight stripe.

Warpage is indepedent of UV or heat exposure...though the latter can definately bring it to your attention!

Pigments can also cause differences in the cooling rate of a part, different crystallization rates, leading to part wrapage. Re-formulate your colors. I'll bet there's a bad actor or two amoug your "silver,chrome yellow,red oxide and carbon black" color match. I'm thinking that one or a combination of two or more of these pigments is causing the warping problem.

Some thoughts,

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warping in upvc

Postby hcachris on Fri Jun 17, 2005 11:06 am

Along the same lines...
if we look at the colorants selected for this match, better options may be available for the application. Red Oxide and Carbon Black (especially carbon black) are known for absorbing heat into the profile. If they absorb enough heat that the heat distortion level of the PVC is exceeded it will likely result in warping or oil canning. Pigment Black 7 has been banned in severla application for this reason alone...even in the substrate layer of a coextruded part.

If we switch to a co-ex capped product (ASA/Acrylic) keep in mind that the Heat build up is typically worse than in a PVC product due to the lower levels of TiO2 that are required for polymer stability.
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Re: warping in upvc

Postby Len2 on Fri Jun 17, 2005 7:55 pm

hcachris wrote:Along the same lines...
if we look at the colorants selected for this match, better options may be available for the application. Red Oxide and Carbon Black (especially carbon black) are known for absorbing heat into the profile. If they absorb enough heat that the heat distortion level of the PVC is exceeded it will likely result in warping or oil canning. Pigment Black 7 has been banned in severla application for this reason alone...even in the substrate layer of a coextruded part.

If we switch to a co-ex capped product (ASA/Acrylic) keep in mind that the Heat build up is typically worse than in a PVC product due to the lower levels of TiO2 that are required for polymer stability.


You're right, carbon black must dissipate the heat it absorbs. That heat goes into the plastic layer. Better use a UV absorber and a UVI, along w/ your best efforts to reduce built in stresses.

I do agree that pigment selection is a critical part of the answer.

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