ʻO ka pilina waiwai o ka PTFE

ʻO kahi ala e hoʻomaopopo ai i ka hopena o ka fluorine ʻo ka ʻimi ʻana i nā ʻokoʻa ma waena o ka linear polyethylene (PE) a me PTFE ʻo ia ka fluoropolymer hope loa e pili ana i nā waiwai a me nā ʻano.

Aia nā ʻokoʻa koʻikoʻi ma waena o nā waiwai o PE a me PTFE:

• * ʻO PTFE kekahi o nā polymers ikehu haʻahaʻa
• *ʻO ka PTFE ka polymer kūʻokoʻa kemika
• *ʻO PTFE kekahi o nā polymers kūpaʻa loa
• *ʻOi aku ka helu heheʻe a me ka umekaumaha kikoʻī o ka PTFE ma mua o ka pālua o ka polyethylene

Loaʻa nā ʻokoʻa PTFE a me PE i nā ʻokoʻa o nā paʻa CeF a me CeH.ʻO nā ʻokoʻa o nā waiwai uila a me nā nui o F a me H ke alakaʻi i kēia mau ʻike:

• *ʻO F ka mea electronegative loa o nā mea a pau (4 Paulings)
• *Loaʻa iā F nā paʻa electron kaʻana like ʻole
• *Hoʻololi maʻalahi ka F i Fe
• *ʻOi aku ka ikaika paʻa o CeF ma mua o CeH
• *ʻOi aku ka nui o F ma mua o H

ʻO ka electronegativity o carbon ma 2.5 Paulings ʻoi aku ka kiʻekiʻe ma mua o ka hydrogen a haʻahaʻa ma mua o ka electronegativity o fluorine.No laila, ua kū'ē ka polarity o ka paʻa CeF i ko ka paʻa CeH, a ʻoi aku ka polarized o ka paʻa CeF.I loko o ka paʻa CeF, hoʻopiʻi maikaʻi ʻia ka hopena fluorine o ka paʻa i ka hoʻohālikelike ʻia me ka paʻa CeH kahi i hoʻopiʻi maikaʻi ʻia ke kalapona.

ʻO ka ʻokoʻa o ka polarity paʻa o CeH a me CeF pili i ka paʻa pili o nā conformations o nā kaulahao polymer ʻelua.Hana ʻia ka crystallization o ka polyethylene i kahi hoʻonohonoho planar a me ka trans conformation.Hiki ke koi ʻia ʻo PTFE i loko o ia conformation ma ke kaomi kiʻekiʻe loa.PTFE, ma lalo o 19 C, crystallizes e like me ka helix me 0.169 nm no ka mamao hou: lawe ia i 13 C atoms no ka 180 huli e pau.Ma luna o 19 C, piʻi ka mamao hou i 0.195 nm ʻo ia hoʻi he 15 mau kalapona kalapona e koi ʻia no ka huli 180.Ma luna o 19 C hiki i nā kaulahao ke hoʻoneʻe i ka angular, e piʻi ana ma luna o 30 C a hiki i ka helu heheʻe (327 C).

ʻO ka hoʻololi ʻana o F no H i loko o ka paʻa CeH e hoʻonui nui i ka ikaika pili mai 99.5 kcal/mole no ka paʻa CeH i 116 kcal/mole no ka paʻa CeF.No laila, ʻoi aku ka kiʻekiʻe o ka paʻa wela a me ke kūpaʻa kemika o PTFE ma mua o PE no ka mea e koi ʻia ka ikehu e wāwahi i ka paʻa CeF.ʻO ka polarity a me ka ikaika o ka paʻa CeF e hoʻolilo i ka mīkini abstraction F atom no ka paʻakikī.ʻO ka hoʻohālikelike ʻana, hiki ke hoʻohui ʻia ka polyethylene lālā nui (> 8 mau lālā no 100 carbon atoms).ʻAʻole hiki ke hoʻohana ʻia ka mīkini branching ma ke ʻano he mea hana e hoʻoponopono ai i ka crystallinity no PTFE.Pono nā comonomers me nā pūʻulu pendent e polymerized me TFE.

ʻO ka crystallinity o ka PTFE i hoʻoheheʻe ʻole ʻia ma ka laulā o 92e98%, kūlike me kahi ʻano kaulahao ʻole.ʻO FEP, he copolymer o TFE a me HFP, he crystallinity like-polymerized o 40e50%.I ka FEP, ua hoʻopaʻa ʻia ka pūʻulu CF3 i hoʻopaʻa ʻia i kahi kalapona kumu ʻoi aku ka liʻiliʻi o ka wela ma mua o nā ʻātoma kalapona mua a me ka lua.Hōʻike nā ʻōkuhi hoʻohaʻahaʻa i ka wela o ka hoʻomaka ʻana o ka degradation o 300 C no FEP (0.02% pohō kaumaha) a me 425 C no PTFE (0.03% pohō kaumaha).