Chiyambi cha Polima Processing Gawo 2

Anthu akhala akugwiritsa ntchito zida zachilengedwe za polymeric monga nkhuni, zikopa ndi ubweya kuyambira chiyambi cha mbiri, koma zopangidwama polimazinatheka kokha pambuyo pa chitukuko cha luso la labala m'zaka za m'ma 1800.Zoyamba zopanga polima za Ž, celluloid, zidapangidwa ndi John Wesley Hyatt mu 1869, kuchokera ku cellulose nitrate ndi camphor.Kupambana kwakukulu mu ma polima opangidwa ndi kupangidwa kwa Bakelite ndi Leo Hendrik Baekeland mu 1907. Ntchito ya Hermann Staudinger m'zaka za m'ma 1920 ikuwonetseratu chikhalidwe cha macromolecular cha maunyolo aatali a mayunitsi obwerezabwereza.1 Mawu oti 'polima' amachokera ku Chigriki, ndipo amatanthauza 'ambiri magawo'.Kukula kofulumira kwa makampani a polima kunayamba itangotsala pang'ono Nkhondo Yachiwiri Yapadziko Lonse, ndikukula kwa ma polima a acrylic, polystyrene, nayiloni, polyurethanes ndi kukhazikitsidwa kotsatira kwa polyethylene, polyethylene terephthalate, polypropylene ndi ma polima ena m'ma 1940 ndi 1950.Ngakhale kuti matani pafupifupi 1 miliyoni okha ndi omwe anapangidwa mu 1945, kupanga mapulasitiki ambiri kuposa zitsulo mu 1981, ndipo kusiyana kwakhala kukukulirakulirabe kuyambira pamenepo.

Thermoplastics nthawi zambiri kukonzedwa mu chikhalidwe chosungunuka.Ma polima osungunuka ali ndi ma viscosity apamwamba kwambiri ndipo amawonetsa kumeta ubweya wa ubweya.Pamene kuchuluka kwa kumeta kukuchulukirachulukira, kukhuthala kwa ma viscosity kumachepa, chifukwa cha kulumikizana ndi kusokonezeka kwa maunyolo aatali a maselo.The mamasukidwe akayendedwe amachepetsa ndi kuwonjezeka kutentha.Kuphatikiza pa mawonekedwe a viscous, ma polima osungunuka amawonetsa kukhazikika.Kuthamanga kwachangu kumayambitsa zochitika zingapo zachilendo za rheological.1 ,5 - 7 Izi zimaphatikizapo kupumula kupsinjika ndi kusiyana kwa normalstress.Kupumula kwapang'onopang'ono kumayambitsa kuzizira muzinthu zomwe zimapangidwa ndi jakisoni komanso zotulutsa.The yachibadwa maganizo kusiyana ndi udindo ena instabilities pa processing ndi extrudate kutupa, mwachitsanzo, kuwonjezeka signiŽ cant m'dera mtanda-gawo pamene chinthu chosungunuka ndi extruded kunja kufa.

Ntchito zofunika kwambiri polima polima ndi extrusion ndi jekeseni akamaumba.Extrusion ndizovuta kwambiri ndipo kuumba jekeseni kumakhala kovuta kwambiri.Njira zonsezi zimaphatikizapo ndondomeko zotsatirazi: (a) Kutenthetsa ndi kusungunula polima, (b) kupopera polima kumalo opangira mawonekedwe, (c) kupanga kusungunula mu mawonekedwe ndi miyeso yofunikira ndi (d) kuziziritsa ndi solidiŽ cation. .Njira zina zogwirira ntchito zikuphatikizapo calendering, kuwomba, thermoforming, compression akamaumba ndi rotational akamaumba.Pali mitundu yopitilira 30 000 ya ma polima okonzedwa ndi njira izi.Kuyenerera kwa chinthu panjira inayake nthawi zambiri kumasankhidwa pamaziko a melt ow index (MFI, yomwe imatchedwanso melt ow rate kapena MFR).Uwu ndi muyeso wosiyana wa mamasukidwe amphamvu otengera kuyeserera koyipa komwe kumaphatikizapo kutulutsa polima kudzera mu miyeso yofananira molingana ndi kulemera kwake. min.Makhalidwe otsika a MFI amatanthawuza kukhuthala kwakukulu ndi kulemera kwakukulu kwa maselo, ndipo makhalidwe apamwamba a MFI amasonyeza zosiyana.Zotsatirazi ndizosiyana zamtundu wa MFI pazigawo zina: extrusion 0 .01 - 10, jekeseni akamaumba 1 - 100, kuwomba akamaumba 0 .01 - 1, rotational akamaumba 1.5 - 20.

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