weathering of kynar® fluoropolymers

WEATHERING OF KYNAR® FLUOROPOLYMERS

FIVE YEAR SOUTH FLORIDA & XENON ARC ACCELERATED WEATHERING

LEADING TO A NEW CHOICEIN CABLE TIES

Gregory O’BrienAmy LefebvreBryan DouglasNREL 2017

SUMMARY OF THE WORK WEATHERING STUDY PERFORMED

5 year southern Florida exposure● Extruded Film Samples● South facing● 45 degree angle● Optical testing yearly● Mechanical Testing at 2 years and 5 years● Exposures are continuing

Xenon arc accelerated weathering● Injection molded tensile bars● Irradiance at 340 nm of 0.8 W/m2/nm ● Chamber Temperature of 70 oC● Black Panel Temperature of 95 oC● Cycle: 102 min light, then 18 min light plus water spray● Samples tested optically and mechanically at 3000 & 5000 hr

2017 NREL PV Reliability Workshop2

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Spectral Power Distributions, Sunlight & Xenon

Sunlight (AM1)

Xenon Arc (D7869 spectrum)

MECHANICAL PROPERTY RETENTION – KYNAR® FILMS – 5 YRS IN FLORIDA

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Southern Florida Exposure Time (years)

Stress at Yield Percent Retention

Kynar Flex 3120 Kynar Flex 2800 Kynar Flex 2850

Kynar Flex 2750 Kynar Flex 2500

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Years Exposure vs Strain at Break



Film Thickness: 50 microns – except Kynar 2500 and Kynar 2750 at 125 micronsFive years in S. Florida – total UV exposure calculated at 1600 MJ/m2

Tensile yield strength maintained at no loss of elongation: UV dosage > 1600 MJ/m2

2017 NREL PV Reliability Workshop

MECHANICAL & CHEMICAL PROPERTIES OF KYNAR® FLEX FILMSBEFORE AND AFTER 5 YEARS OF EXPOSURE IN SOUTHERN FLORIDA

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Request: DFP-16-0357, 13499-148-1 Kynar 2850-07 controlRequest: DFP-16-0372, 13499-148-2 Kynar 2850-07 5 years outdoor exposure

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Kynar Flex 2850 controlKynar Flex 2850 – 5 yrs exposed

Kynar Flex® 2850 Tensile Stress-Strain Kynar Flex® 2850 ATR- FTIR

Full mechanical performance is maintained No UV attack of polymer backbone by FTIR


OPTICAL PROPERTIES OF KYNAR® FLEX FILMSBEFORE AND AFTER 5 YEARS OF EXPOSURE IN SOUTHERN FLORIDA

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Kynar Flex ® 2850 Light Transmission

5 Year Control

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Film Color Change (ΔE) vs Exposure Time



Color change is below the perception limit (< ΔE of 1.5)No color change and no significant change is light transmission show UV stability


KYNAR FLEX® FILMS SURFACE PROPERTIES SEM MICROGRAPH – BEFORE AND AFTER 5 YEARS IN FLORIDA

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Kynar Flex® 2850Unexposed Film

Kynar Flex® 2850Exposed 5 Years in Florida

No surface erosion or pitting shows the extreme UV resistance of Kynar® Fluoropolymers


MECHANICAL PROPERTIES OF KYNAR FLEX® TENSILE BARSBEFORE & AFTER 5000 HR XENON ARC ACCELERATED WEATHERING EXPOSURE

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Irradiance @ 340 nm of 0.8, 102 min of light with 18 min light & water sprayChamber Temp = 70 oC , BPT = 95 oCSamples = ASTM D638 type 1

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Tensile Elongation Retention (%)



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Tensile Yield Strength (psi)

Kynar Flex 2850 Kynar Flex 2800Kynar Flex 3120 Kynar Flex 2750Kynar Flex 2500

Results clearly show no embrittlement or degradation in accelerated weathering2017 NREL PV Reliability Workshop

MECHANICAL PROPERTIES OF KYNAR FLEX® GRADES OFFERS OPTIONSSTRENGTH AND FLEXIBILITY VARY – BUT ALL OFFER OUTSTANDING WEATHERING

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Material Exposure (hrs)

Stress at Yield (psi)

Strain at Break

(%)

Tensile Modulus (psi)

0 5850 44 170,814 Kynar Flex® 2850 3000 5900 46 178,697

5000 5950 46 176,375 0 4050 135 117,022

Kynar Flex® 3120 3000 4025 147 120,136 5000 4150 137 115,333

0 3875 276 91,435 Kynar Flex® 2800 3000 3865 327 93,598

5000 3975 323 89,442 0 3075 353 65,440

Kynar Flex® 2750 3000 3100 368 64,222 5000 3125 377 66,292

0 2600 491 46,955 Kynar Flex® 2500 3000 2625 604 48,524

5000 2625 638 45,511

Material Years Thickness (µm)

Stress at Yield (PSI)

Stress at Break (PSI)

Strain at Break (PSI)

Kynar Flex® 3120 0 50 4,470 9,418 6005 4,397 6,720 631

Kynar Flex® 2800 0 50 4,229 9,246 6055 4,111 6,759 608

Kynar Flex® 2850 0 50 5,907 7,233 3445 6,048 6,475 348

Kynar Flex® 2750 0 125 2,870 6,814 6755 2,839 7,026 954

Kynar Flex® 2500 0 125 2,475 6,313 7625 2,472 6,562 1,126

Injection Molded Part Properties Extruded Film Properties

A range of stiffness and strength offers component designers options For applications where extreme weathering performance is critical


STRONG CABLE TIES – FOR EXTREME CONDITIONS

Kynar® Films have shown outstanding weathering performance in PV backsheets

Kynar Flex® grades show no changes in properties in outdoor & Xenon weathering

Extreme weathering resistance, high strength and flexibility offer the designer choice to mold high performance cable ties

One company – Nile Polymers in offering Kynar® cable ties.

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http://www.nilepolymers.com/strong-ty-cable-ties/


weathering of kynar® fluoropolymers

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