Gabatarwar sarrafa Polymer Part 2

Dan Adam ya yi amfani da kayan polymeric na halitta kamar itace, fata da ulu tun farkon tarihi, amma roba.polymersya zama mai yiwuwa ne kawai bayan haɓaka fasahar roba a cikin 1800s.John Wesley Hyatt ne ya kirkiro Ž rst roba polymer abu, celluloid, wanda John Wesley Hyatt ya ƙirƙira a 1869, daga cellulose nitrate da camphor.Babban ci gaba a cikin polymers na roba shine ƙirƙirar Bakelite ta Leo Hendrik Baekeland a cikin 1907. Ayyukan Hermann Staudinger a cikin 1920 sun nuna a fili yanayin macromolecular na dogon sarƙoƙi na maimaita raka'a.1 Kalmar 'polymer' ta fito daga Girkanci, kuma tana nufin 'da yawa. sassa'.Saurin haɓaka masana'antar polymer ya fara ne jim kaɗan kafin yakin duniya na biyu, tare da haɓaka polymers na acrylic, polystyrene, nailan, polyurethane da gabatarwar polyethylene, polyethylene terephthalate, polypropylene da sauran polymers a cikin 1940s da 1950s.Yayin da kusan tan miliyan 1 ne aka samar a shekarar 1945, yawan robobin da ake samarwa ya zarce na karfe a shekarar 1981, kuma gibin ya ci gaba da karuwa tun daga lokacin.

Yawan zafin jiki ana sarrafa su a cikin narkakkar yanayi.Molten polymers suna da ƙima mai girman danko sosai kuma suna nuna halayen ɓacin rai.Yayin da adadin shear ɗin ya ƙaru, danko yana raguwa, saboda alignments da rarrabuwa na dogayen sarƙoƙi na ƙwayoyin cuta.Danko kuma yana raguwa tare da ƙara yawan zafin jiki.Baya ga halayen danko, narkakkun polymers suna nuna elasticity.Nauyi yana da alhakin adadin abubuwan al'ajabi na rheological.1 ,5 - 7 Waɗannan sun haɗa da shakatawa na damuwa da bambance-bambancen damuwa.Jin daɗin jinkirin damuwa yana da alhakin daskarewa a cikin damuwa a cikin gyare-gyaren allura da samfuran da aka fitar.Bambance-bambancen danniya na yau da kullun suna da alhakin wasu rashin kwanciyar hankali yayin sarrafawa da kuma fitar da kumburi, watau alamar ba za ta iya karuwa a cikin yanki ba lokacin da narkakkar kayan ke fita daga mutuwa.

Mafi mahimmancin ayyukan sarrafa polymer shine extrusion da gyare-gyaren allura.Extrusion abu ne mai ƙarfi kuma gyare-gyaren allura yana da ƙarfin aiki.Duk waɗannan hanyoyin sun haɗa da jerin matakai masu zuwa: (a) dumama da narkewar polymer, (b) yin famfo polymer zuwa naúrar siffa, (c) samar da narke cikin siffar da ake buƙata da girma da (d) sanyaya da solidiŽ cation. .Sauran hanyoyin sarrafawa sun haɗa da calendering, busa gyare-gyare, thermoforming, matsawa gyare-gyaren da juyawa.Akwai fiye da maki 30 000 na polymers da aka sarrafa ta waɗannan hanyoyin.An yanke shawarar dacewa da wani abu don wani tsari na musamman akan tsarin narkewar ow (MFI, wanda ake kira melt ow rate ko MFR).Wannan juzu'in ma'aunin danko ne wanda ya dogara da ɗanyen gwajin da ya ƙunshi extrusion na polymer ta hanyar mutuƙar daidaitattun ma'auni ƙarƙashin aikin da aka ƙayyade.8 MFI shine adadin gram na polymer da aka tattara daga na'urar gwaji a cikin 10. min.Ƙananan ƙimar MFI suna nufin babban danko da babban nauyin kwayoyin halitta, kuma manyan ƙimar MFI suna nuna akasin haka.Mai zuwa shine kewayon MFI na yau da kullun don wasu matakai: extrusion 0 .01 – 10, gyare-gyaren allura 1 – 100, gyare-gyaren busa 0 .01 – 1, gyare-gyaren juyawa 1.5 – 20.

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