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Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals by Bob Ohm* & Dan Patton Lion Copolymer, LLC Compounding and Development Center 5955 Scenic.

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Presentation on theme: "Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals by Bob Ohm* & Dan Patton Lion Copolymer, LLC Compounding and Development Center 5955 Scenic."— Presentation transcript:

1 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals by Bob Ohm* & Dan Patton Lion Copolymer, LLC Compounding and Development Center 5955 Scenic Highway, Baton Rouge, LA * Speaker

2 Outline Introduction Bloom vs. Iridescence 2 3 Designed Experiment: Filler, Oil & Curative Effect of Cure Temperature & EPDM Polymer Surface Analysis Antioxidant Comparison Final Experiments Summary

3 Introduction Why weatherseals are based on EPDM Excellent Weatherability Impervious to Ozone Highly Resistant to Heat and Oxidation Highly Extendable Discoloration in Light Initial colors blue / red / green Change to bronze / gold Prior Work

4 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals Best viewed at shallow angle A long-standing issue Various solutions proposed: –Cure system –Filler –Polymer –Additives Root cause & permanent fix elusive

5 The Iridescent Color depends on the angle of view

6 Bloom and Bleed Surface Discoloration due to powdery solid (bloom) or liquid film (bleed) The remedy is straightforward: 1.Remove the material at the surface 2.Determine the composition of the material removed. 3.Lower the dose or eliminate the use of the material identified. Gold Iridescence Surface Discoloration due to The discoloration can not be readily removed. Methylene chloride removes - but only temporarily! ???

7 Thermal Desorption Results Eric Jourdain, Paper #42, 149 th ACS Rubber Division meeting (May 1996)

8

9 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals Five Studies: design for: A/ filler (furnace vs. thermal) B/ plasticizer (par oil vs. poly alpha-olefin), C/ cure system (sulfur vs. peroxide) and D/ cure time at 182°C (1.5 vs. 10 minutes) 2. effect of: A/ diene content (4 vs. 8%), B/ ethylene content (60 vs. 70%) and C/ cure temperature (230 vs. 340°C) 3. surface analysis 4. antioxidant comparison 5. polymer, filler & other variations

10 2 3 Designed Experiment Filler / carbon black Oil / plasticizer Cure System (Sulfur vs. Peroxide) Additive Package (the 3 Amigos)

11 Filler Comparison A.Furnace black: –made from crude oil –made in air –contains aromatic structures (staining) –contains sulfur, nitrogen B.Thermal black*: –made from natural gas –anaerobic manufacture (no oxygen) –minimum extractables (aromatics) –little/no sulfur, nitrogen * plus precipitated silica to equalize hardness

12 Plasticizer Comparison A.Parafinnic oil: –made from crude oil –contains aromatic structures –contains sulfur, nitrogen B.Poly -olefin: –made from decene –no residual unsaturation (removed by hydrogenation) –no sulfur, nitrogen

13 Cure System Comparison A.Sulfur cure: –contains sulfur, nitrogen –little/no oxygen –accelerator fragments found on surface B.Peroxide cure: –no sulfur, nitrogen –contains oxygen

14 Gold Ratings: 1 = best, 5 = worst 6 days exposure per SAE J1960 (exterior) 3 Am.= 5 3 Am. = 1 * = mat surface develops during light exposure

15 Gold Ratings: 1 = best, 5 = worst 6 days exposure per SAE J1885 (interior) 3 Am.= Am. = 1.5 * = mat surface develops during light exposure

16 Summary of 2 3 Experiment A.The filler system is most important for gold iridescence. A thermal black/ppt. silica blend develops a low-gloss (mat) surface during light exposure, minimizing the gold iridescence. B.The 3 Amigos are effective, esp./SAE J1885. C.A peroxide cure is poorer than the sulfur cure per SAE J1885 (no effect per SAE J1960). D.The PAO is better than paraffinic oil per J1960 (no effect or slightly poorer by J1885).

17 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals Five Studies: design for: A/ filler (furnace vs. thermal) B/ plasticizer (par oil vs. poly alpha-olefin), C/ cure system (sulfur vs. peroxide) and D/ cure time at 182°C (1.5 vs. 10 minutes) 2. effect of diene content (4 vs. 8%), ethylene content (60 vs. 70%) and cure temperature (230 vs. 340°C) 3. surface analysis 4. antioxidant comparison 5. polymer, filler & other variations

18 Polymers Evaluated Previous workers = best Previous workers = worst (Cure Temperature = 230 or 340 °C) Light Exposure = 6 days SAE J1885

19 Gold Ratings: 1 = best, 5 = worst UV* = 1 3 Am.= 1 UV* = 3 3 Am. = 2 Cure Temp. 10/230, 2/340 °C = NO EFFECT However, 10at 340°C = IMMEDIATE GOLD * = heavy white bloom on molded samples

20 Summary of Second Study A.The gold color can be developed by oxidation without light exposure. (However, this method leads to sample embrittlement.) B.High diene polymers give lower gold ratings. C.Gold ratings can be further lowered by addition of the Three Amigos. D.Ethylene level and cure temperature have little effect on gold in our laboratory work.

21 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals Five Studies: design for: A/ filler (furnace vs. thermal) B/ plasticizer (par oil vs. poly alpha-olefin), C/ cure system (sulfur vs. peroxide) and D/ cure time at 182°C (1.5 vs. 10 minutes) 2. effect of diene content (4 vs. 8%), ethylene content (60 vs. 70%) and cure temperature (230 vs. 340°C) 3. surface analysis 4. antioxidant comparison 5. polymer, filler & other variations

22 Surface Analysis Methods SEM TOF-SIMS XPS AFM Scanning Electron Microscopy Time of Flight - Secondary Ion Mass Spectroscopy X-Ray Photoelectron Spectroscopy Atomic Force Microscopy

23 Surface Analysis of Molded Test Pads Scanning Electron Micrograph (SEM) 10 m

24 Surface Analysis Techniques TOF-SIMS Time of Flight Secondary Ion Mass Spectroscopy * or ESCA, electron scattering for chemical analysis XPS X-Ray Photoelectron Spectroscopy* Found only siloxane (mold release).

25 XPS - Black Area Oxygen Carbon

26 XPS - Gold Area Carbon Oxygen

27 XPS Oxygen Results - 2 nd Study

28 XPS Nitrogen Results - 2 nd Study contains MSDPA amine antioxidant

29 XPS Zinc Results - 2 nd Study

30 Gold Matt Gold Shiny High Resolution AFM Surfaces Black

31 Surface Analysis Summary A.Molded samples under SEM appear to develop raised nodules. B.TOF-SIMS was not successful in identifying the composition of the nodules. C.XPS finds the gold surface is enriched in oxygen and, to a lesser extent, nitrogen and zinc. D.AFM finds black regions are smooth; light-exposed gold regions, especially low-gloss, are rough – nano structure.

32 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals Five Studies: design for: A/ filler (furnace vs. thermal) B/ plasticizer (par oil vs. poly alpha-olefin), C/ cure system (sulfur vs. peroxide) and D/ cure time at 182°C (1.5 vs. 10 minutes) 2. effect of diene content (4 vs. 8%), ethylene content (60 vs. 70%) and cure temperature (230 vs. 340°C) 3. surface analysis 4. antioxidant comparison 5. polymer, filler & other variations

33 Comparison of Antioxidants in the Three Amigos Blank Bisphenolic ODPA TMQ No AO (liquid) Light Exposure = 6 days SAE J1885

34 Comparison of Antioxidants in the Three Amigos (continued) MSDPA Sulfonated Bisphenol NBC Diphenyl- Phosphite amine Blend

35 Light-Induced Gold Iridescence (Sunburn) of EPDM Weatherseals Five Studies: design for: A/ filler (furnace vs. thermal) B/ plasticizer (par oil vs. poly alpha-olefin), C/ cure system (sulfur vs. peroxide) and D/ cure time at 182°C (1.5 vs. 10 minutes) 2. effect of diene content (4 vs. 8%), ethylene content (60 vs. 70%) and cure temperature (230 vs. 340°C) 3. surface analysis 4. antioxidant comparison 5. polymer, filler & other variations

36 Polymer, filler & other variations Gold Ratings = cured / uncured Peroxide Cures of: N762 blackN990 black & KE clay EPDM 4345 (DCPD)5/51/1 EPM 404 Copolymer5/42/2 EPDM 509 (ENB)4*/51/1 EPDM 509 / sulfur cure5*/4rainbow/ws The filler system of N990 & KE clay give a dull surface After SAE J1885 exposure, similar to N990 & ppt. silica. * Rating improves where Mylar film adhered.

37 Final Experiment Photo of Test Pad with Gold Iridescence Middle portion clamped 1 week at RT removes gold. 10 mm However: gold returns on oven aging or more light exposure.

38 Optical Properties of Nano Particles Chad A. Mirkin, George C. Schatz, et. al., Science, 294, pages (2001), as taken from Chemical & Engineering News, page 10 (Dec. 2, 2001) Silver nanoprisims scatter red light. Gold nanorods scatter orange light. Gold nanospheres scatter green light.

39 Summary A.Compression of the surface can remove the gold iridescence. B.However, this is not a practical solution because the gold is redeveloped during brief oven aging or additional light exposure. C.For future work, a permanent solution may require both chemical and physical (structure) control.

40 Thanks for your attention Any Questions?

41 In the scales of the green portion of the papillos wings, each concavity reflects bright yellow while the outer edges reflect bright blue… The papillo butterflys wings are covered with small textured scales (above right)… Tiny concavities within these scales (below left) create color through constructive interference…

42 The Three Amigos

43 Gold Region Particle Size of Additives Har d Cla y Soft Clay Zinc Oxide Precipitated Silica Whiting N990 N774 Carbon Black

44 High Resolution XPS Main Peak = C-(C1H) control sample A -O-C=O gold sample A C-O C=O C-N

45 AFM Surface Analysis Black Surface Shiny Sample Black Surface of Matt Sample Gold Shiny SurfaceGold Matt Surface 30 m

46 Gold Matt Gold Shiny High Resolution AFM Surfaces nm m 350 nm Black 475 nm 665 nm 130 – 250 nm


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