What group or class of chemicals has the greatest tensile strength?
select ?ent where { ?ent wdt:P31 wd:Q17339814 . ?ent wdt:P5479 ?obj . ?ent wdt:P31 wd:Q17339814 } ORDER BY DESC(?obj)LIMIT 5 
group or class of chemical substances: Q17339814 group or class of chemical substances: Q17339814