A History of Rubber Cables

Transcription

1 A History of Rubber Cables ICC Spring Meeting Nashville, TN 23 March 2010 Mark F. Welker, ExxonMobil Chemical Co. Steven Boggs, University of Connecticut Carl Zuidema, Okonite Company Wes Kegerise, Okonite Company Robert Fleming, Kerite Company

2 Rubber Cables Almost Endless Varieties Exist Today How did we get here? Why EPR? 2

3 What is Rubber? A rubber is defined as a polymer with a large elastic limit which normally results from large entanglement of the polymer chains Elasticity is the rapid recovery of a material to its approximate shape and dimensions after substantial deformation by force and subsequent release of that force A polymer is a large, high molecular weight molecule made from the linkage of many small, low molecular weight molecules (monomers) Crystalline polymers are characterized by a high degree of molecular order Amorphous polymers are characterized by a high degree of molecular disorder Vulcanization is the formation of chemical cross-links, where new bonds are formed between different polymer chains Segments of different polymer chains Crystalline Ordered Regular Amorphous Disordered Random Coil Vulcanized Cross-linked Cured 3

4 Natural Rubber An American Invention S S 4 S Moderately stable (~120 C) C-S and S-S bonds between polymer chains

5 Conformational Elasticity 5

6 The Application of Natural Rubber to Electrical Insulation The transmission and distribution of telegraph, telephone, and electrical systems became the driving forces for the development of electrical insulation compounding technology 1837: Samuel Morse invents the telegraph 1844: First air-insulated telegraph line: Washington, DC to Baltimore 1846: Baltimore to Philadelphia telegraph line Insulation of telegraph lines was problematic, especially where they had to be buried or placed underwater Austin Goodyear Day, a relative of Charles Goodyear, wanted to improve the performance and lower the cost of natural rubber, while also looking for new applications to expand his business Vulcanized rubber, if it could be properly modified, or compounded, appeared to be a natural candidate for electrical insulation 6

7 Kerite Insulated Telegraph Cables Charles Goodyear had died in 1860, but A.G. Day built upon his extensive work and 1844 patent for vulcanization, carrying out over 3000 experiments in an attempt to improve upon the properties of natural rubber Eventually, Day added Kerite to natural rubber, improving the ozone, moisture, and temperature resistance and thereby enabling reliable cable operation when placed overhead, buried, or submerged in either fresh or salt water Probably derived from the Greek word Keros, meaning wax, Kerite, was one of the earliest examples of rubber compounding Kerite included fillers, curatives, and plasticizers to yield an oil based rubber At about this same time, A.G. DeWolf, who was A.G. Day s Plant Superintendent, invented the crosshead extruder, which was critical for the manufacture of rubber insulated cable With Kerite and the De Wolfe extruder, A.G. Day s company was now positioned to become a major supplier of insulated wire and cable By 1868, over 200 Kerite-insulated telegraph cables had been installed in the US, Canada, Panama, and Egypt 7

8 Kerite Cable Technology The Kerite Formulation Combine coal tar (25 lbs) and asphalt (15 lbs) Heat together at 350 F for ½ hour Add linseed oil (70 lbs) Continue heating at 350 F for 7 hours Let stand overnight After heating to 240 F, add sulphur (10 lbs) Heat again to 300 F for 30 minutes Add sulphur (4 lbs) Heat to 300 F Add talc (56 lbs) Keep at 300 F for 30 to 45 minutes After vulcanization is complete, the mixture can be poured into molds or allowed to cool in mass An early De Wolf crosshead extruder, ca

9 Bell, Edison, and Cheever Alexander Graham Bell invented the telephone in 1876 At about this same time, John Haven Cheever developed a moisture resistant natural rubber-based insulation that was coined Okonite The name Okonite was derived from the telegraph sign-off OK and nite, from the natural rubber compound called vulcanite Okonite Compounded Rubber India Rubber 49.6% Sulphur 5.3% Lampblack 3.2% Zinc Oxide 15.5% Litharge [Lead(II) Oxide] 26.3% Silica 0.1% In September 1878, Thomas Edison declared that he would light a half mile radius of lower Manhattan with his new invention, the incandescent light bulb In 1882, when Edison flipped the switch at the first US electric power station on Pearl Street in New York City, it was energized with Okonite cables that were insulated with a natural rubber-based compound 9

10 Increased Use of Rubber Insulated Power Cables 1880 s Okonite pursued power applications for rubber insulated cables Kerite insulated cable dominated electrical signal applications in the telegraph, telephone, and railroad industries Late 1880 s Kerite entered the cable market for power distribution 1889 Kerite insulated cables were operating at up to 1100 V for the Seymour Electric Light Company 1898 Kerite insulated 1000 kcm submarine cable laid across the Gowanus Canal by the Coney Island and Brooklyn Railway By the 1920 s, natural rubber compound for electrical insulation included a wide variety of potential ingredients (e.g., zinc oxide, litharge, whiting, colloidal clays, talc, paraffin waxes, plasticizing oils, and resins) and was used for insulated cables up to 7500 V AC By 1931, 25 kv Okonite and Kerite rubber insulated power cables were being supplied to a wide range of electric utilities 10

11 Rubber Insulation Outstanding Environmental Stability First Submarine Power Cable Installed in New York City Fishers Island, NY First Underground Residential Distribution (URD) Cable System 11

12 Polymer Chemistry Comes of Age Fundamental problems existed for higher voltage applications, especially the thermal aging characteristics inherent to sulfur cured natural rubber By the early 20 th century, the burgeoning field of modern organic chemistry would give rise to the first truly synthetic polymers The Germans first made synthetic rubber during World War I, but it was not practical for industrial applications In the 1930 s, butadiene was copolymerized with styrene by Walter Bock and Edward Tschunkur at I.G. Farben in Germany Buna-S was the first synthetic rubber with good strength and wear properties Standard Oil acquired the technology in the US, which eventually became known as GRS for Government Rubber-Styrene GRS was produced under the Rubber Reserve Program during WWII The more descriptive SBR, for Styrene Butadiene Rubber, was applied later SBR was used extensively for wire insulation into the 1960 s and remains one of the largest volume synthetic rubbers today, but not for wire and cable due to Poor thermal stability (maximum rated temperature of 85 C) Very poor tracking resistance SBR insulated secondary cable is responsible for most manhole events 12

13 Synthetic Rubber 13

14 Ethylene Propylene Rubber (EPR) 1955 Nobel Prize in Chemistry jointly awarded to Carl Ziegler and Guilio Natta Ziegler developed a novel catalyst for polymerization of ethylene to polyethylene Natta extended the development to other monomers such as propylene Co-polymerizing ethylene with propylene yields a new elastomer, EPM Later extended to the development of many other polymers, e.g., EPDM Significant EPR interest - potential for excellent environmental stability & low cost Early 1960 s - two manufacturers in Europe & three in US had begun production 1950 s - GE pioneered dialkyl peroxides Very reactive molecules, generating free radicals above a specific temperature Produce cross-links in saturated polymers and unsaturated polymers The C-C cross-links formed are more stable than C-S or S-S cross-links First applied to cross-linking polyethylene, but a natural fit for EPR Wire and Cable producers were quick to recognize the advantages of EPR and were offering EPR insulated cables by

15 Rubber Polymers C H 3 C H 3 C H 3 Natural Rubber Highly unsaturated polymer backbone n cis-polyisoprene Natural Rubber Carbon to carbon double bonds Latent reactivity and/or instability Cross-linking and/or oxidation SBR Control over monomer incorporation x Control over properties Styrene Butadiene Rubber CH 2 y Highly unsaturated (backbone, pendant groups) H 3 C CH 3 H 3 C C CH 3 H 3 C CH 3 H 3 H 3 C CH 3 CH3 H 3 C Isoprene Isobutylene Rubber x CH 3 CH3 y Butyl Rubber Control of monomer incorporation, properties Lower unsaturation in polymer backbone Better stability and compounding technology. improved water resistance and the dielectric. properties Butyl-based insulations rated to 85 C at 15 kv 15

16 EP(D)M Polymerization Copolymers ethylene EPM (aka EPR, EP Rubber ) Control ethylene to propylene ratio (crystallinity) H C CH CH H 2 C 3 Control molecular weight Saturated backbone very good oxidative stability EPM CH 3 propylene CH 3 Terpolymers EPDM Control ethylene to propylene ratio (crystallinity) Control diene type and abundance (control reactivity) Control molecular weight Saturated backbone - very good oxidative stability H C CH H 2 C CH CH 3 CH 3 H 3 C ENB EPDM CH 3 16

17 Heat and Oil Resistance of Commercial Rubbers Type Heat Resistance ( C) H G F E D C B A IIR EPM EPDM SBR/NR/BR EACM CSM CR MQ Class A B C D E F G J K Oil Resistance (% swell) ACM CO NBR FKM MFQ IIR = Butyl Rubber CR = Neoprene CSM = Hypalon ACM = Acrylate MQ = Silicone NBR = Nitrile CO = Epichlorhydrine MFQ = Fluorosilicone FKM = Fluor. rubber Many rubber types - in response to industry demand 17

18 New Synthetic Ethylene Propylene Rubber Manufacturing test run in Baton Rouge, LA in

19 First Commercial Advertisement for EPR 404 EPR 404 still available today as Vistalon 404 January 1962 Issue of Rubber World 19

20 EP(D)M and EPR Key Product Attributes EP(D)M Saturated backbone molecule Thermal and oxidative stability Stable to light/uv/air/heat Chemical resistance Good resistance to polar solvents Wide range of compositions From low to high ethylene content From zero to high ENB VNB for improved cross-linking & stability Wide range of molecular weights Low specific gravity (< 0.9) Compared to SBR, CR Long thin flexible molecule Can be easily vulcanized (S or peroxide) Remains flexible at low temperatures Product form Supplied in bales or pellets EPR Compounds Ozone resistance Weathering stability (light, UV) Heat resistance (up to 160 C) Wide durometer range (25A to 40D) Electrical resistance Low temperature flexibility Compatible with a wide variety of fillers and additives leading to finely tailored properties Replaced natural and general purpose synthetic rubbers in many applications where temperature resistance, UV resistance, and/or water/steam resistance is required Ideal material for electrical applications Insulators (low to medium voltage) Semiconductors 20

21 EPR Electrical Insulation Formulas EP(D)M polymer Clay (treated) Silane Dialkyl peroxide Co-agent(s) Plasticizer(s) Metal oxide(s) Antioxidant(s) Matrix dielectric Hard dielectric Improve clay-polymer interface Cross-link initiator Cross-link modifier Viscosity modifiers, processing aids Stabilizers Improved aging, stability 21

22 EPR Temperature Stability 1600 Stress/Strain EPR C 1200 Stress, psi C 90 C to ASTM D Elongation % 22

23 EPR Compound Production 23

24 EPR Class ICEA S , Insulation Type EPR I - Earliest EPR Based Insulation Compounds II - 2 nd Generation EPR Based Insulation Compounds, Based on Semi-Crystalline Polymers III C Rated EPR Based Insulation Compounds IV C Rated EPR Based Insulation Compounds 24

25 ICEA Requirements ICEA Class I II III IV Tensile Strength (psi) Elongation (%) Oven Aging Test Temperature 121 C 121 C 136 C 121 C % Retention, T/E 75/75 80/80 75/75 75/175 (psi, abs.) Hot Creep, Elongation/Set (%) 50/5 50/5 50/5 50/5 ICEA S , Insulation Type EPR 25

26 The 21st Century New Technologies Continue to Advance Rubber Based Insulations In the late 1990 s, ExxonMobil Chemical introduced an advanced EPDM polymer having low metal residues as well as an architecture specifically tailored for wire and cable applications (Vistalon 1703P). More recently, a new generation of catalysts has enabled better control over polymer architecture and purity. The 2005 US Patent 7,511,104 B2 led to the commercialization of a metallocene catalyzed EPM specifically designed for medium voltage compound performance (Vistalon 722). The implementation of High Throughput Technologies for polymer development has enabled the screening of large numbers of catalysts and polymers in relatively short times. Work that used to take months is now compressed to days. The widespread use of Statistical Design of Experiments provides highly detailed information on the contributions of individual components to compound performance using a minimum number of experiments. The number of experiments needed to understand complex relationships has been reduced by an order of magnitude or more. New testing and analytical capabilities continue to provide additional insights into critical attributes that provide high performance or contribute to failure mechanisms. 26

27 Summary Driven by the difficult environmental demands of transmission and distribution for telegraph, telephone, and electrical systems in the latter half of the 1800 s, early rubber compound technology provided the first generation of natural rubber based insulations that helped to progress these new industries Rubber technology, manufacturing technology, and the power industry advanced simultaneously to enable the widespread use of 25kV power cables by the early 1930 s The significant enhancements provided by the development of synthetic polymers in the mid 20 th century greatly improved the capability of power distribution cables In the latter half of the 20 th century, insulation based on EPR compounds evolved to provide the highest standards for safety and reliability of power distribution The new technologies available in the 21 st century promise the continued advancement of rubber based insulation compounds 27

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