Kodi Moisture-cured polyurethane ndi chiyani

Kodi Moisture-cured polyurethane ndi chiyani

Polyurethane yopangidwa ndi chinyezi ndi gawo limodzi la polyurethane kuti mankhwala ake ndi chinyezi cha chilengedwe. Polyurethane yochiritsira chinyezi imakhala ndi isocyanate-terminated pre-polymer. Mitundu yosiyanasiyana ya pre-polymer ingagwiritsidwe ntchito kupereka katundu wofunikira. Mwachitsanzo, ma polyether polyether polyols a isocyanate amagwiritsidwa ntchito kuti azitha kusinthasintha chifukwa cha kutentha kwa magalasi otsika. Kuphatikiza gawo lofewa, monga polyether, ndi gawo lolimba, monga polyurea, limapereka kuuma kwabwino komanso kusinthasintha kwa zokutira. Komanso, katunduyo amawongoleredwa posankha mitundu ya isocyanate kuti aphatikizidwe ndi pre-polymer.

Mitundu iwiri ikuluikulu ya isocyanate ndi onunkhira isocyanate ndi aliphatic isocyanate. Aromatic isocyanate ali ndi reactivity kwambiri. Komabe, ili ndi kusakhazikika bwino kwakunja komanso kusinthika kwakukulu. Zitsanzo zina za ma isocyanate onunkhira ndi toluene diisocyanate(TDI) ndi 4,4'diphenylmethane diisocyanate(MDI). Kumbali ina, aliphatic isocyanate, monga, isophorone diisocyanate (IPDI), imapereka nyengo yabwino kwambiri komanso mtundu kusunga; komabe, reactivity ya aliphatic isocyanate ndi yotsika, kotero zothandizira zina zingafunike. Chifukwa chake, mitundu ya isocyanate ndiyofunikira kuti mupeze katundu wofunikira. Kuphatikiza apo, zowonjezera, zosungunulira, zopaka utoto, ndi zina zotere zitha kuonjezedwa potengera ntchito. Komabe, zida zopangira ma polyurethanes otetezedwa ndi chinyezi ziyenera kuyendetsedwa kuti zisakhale ndi chinyezi kuti zipeze kukhazikika kosungirako komanso katundu wafilimu.

Ubwino wina wa polyurethane yochizira chinyezi ndikuti ndi gawo limodzi. Choncho, ndizosavuta kugwiritsa ntchito popeza palibe kusakaniza koyenera koyenera, poyerekeza ndi zokutira zamagulu awiri. PU yochiritsidwa ndi chinyezi imalumikizidwa ndi momwe Isocyanate-terinated pre-polymer ndi madzi mumlengalenga, kupanga ma amines ndi mpweya wochepa wa carbon dioxide. Pomaliza, momwe ma amine ndi ena onse a isocyanate-terminated pre-polymer amachitika zomwe, zimapanga kulumikizana kwa urea.