Document MrwjpY25Qe6OVDj1NqLrYeLy
Paint Research July, 1966
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Prolect #177 - Pigment Studies
He have recently completed a study ol various pigments with regard to their ability to absorb and ref] ect ultraviolet radiation. The study includes white and colore d pigments as well as extender pigments. Each pigment was dispersed in an alkyd varnish at a concentration of 10 pounds per 100 ga llons. A low concentration was chosen to allow some transmissicin by such pigments as rutile titanium dioxide. All data are repor ted for dry films having a corrected thickness of 2 mils. Also Reported is the wave length at which transmission by the film bjecomes Ojt. The results of this study are shown in Table I.
The data are reported as percent tran smission, the renalnder of the light being absorbed or reflectedd by the film. It should be pointed out that the alkyd resin will absorb some of the radiation and therefore it cannot be assumed t>ha t all absorption is by the pigment only. However, the alkyd res in is constant throughout all samples and the transmission of one pigmented film relative to another should be quite meaningful.
It is interesting to note that calclui|m carbonate transmits more ultraviolet radiation than magnesium silicjate. We repeatedly observe that calcium carbonate extended paints exhibit better tint retention than magnesium silicate. This sugges ted that perhaps it absorbed and/or reflected more U7 energy than mSgnesium silicate, thereby protecting the binder. However, the repults are contrary to this thought. It therefore appears that the oil demand of each pigment is of more importance. Calcium carbonajte having less oil demand leaves mere free vehicle to function as pigment binder. It can also be assumed that because there is more total free vehicle the percentage of degraded binder would be les3 in a calcium carbon*te extended paint at any point in the exposure history, leaving Bore vehicle to bind the pigment particles toge :her into a continu<*> film.
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Paint Research July, 1966
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Table I
Transmission of Ultraviolet by Pigments
* Transmission S-W Code 280 - 400 m /s
tutile titanium dioxide
66 53 00
3.62*
Anatase titanium dioxide 66 00 22
2.88*
Magnesium silicate Calcium carbonate
62 32 00 63 01 00
24.3* 29.2*
Aluminum silicate
62 02 27
22.6*
Barium sulfate
63 70 00
25.0*
Nepheline syenite
Minex-4
26.0*
Potassium titanate
PKT 6.0*
Zinc oxide
67 21 00
21.2*
Leaded zinc oxide
68 22 00
10.8*
Basic lead silicate
68 01 00
24.1*
Basic lead sulfate
68 10 00
19.0*
Basic lead carbonate
68 05 00
18.2%
Black iron oxide
71 50 00
9.25*
Carbon black (10#)
70 50 00
0*
Carbon black (1#)
70 50 00
17.8*
Phthalocyanine Green
Monastral Green B 0*
Dolamer Yellow
0*
Quinacridone Red
Monastral Red B
39*
Wavelength of Zero Transmission
300 m/
353 300 304 303 305 313 335 310 320 310 310 310
315 400 310 400 487 357
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r edac t ed
(A6) Class 68 05 00
Lead Containing And Lead Free Pigments In A-100 Undercoater
Series 41173 - 41192 was examined and retired after 24 s exposure at Miami, Florida. It includes A6 V 32 and A6 W 23 ondercoaters with and without lead carbonate. Zirconium sui ts was added to the lead free formulation as a stain control
Regular A-100 is the topcoat.
The results of this series indicate no large difference performance of lead containing primers compared with lead free yrlairs except in mildew resistance. The lead containing primers
rated one to two points better than the lead free formulation.
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