Rashin damuwa game da muhalli

Rashin damuwa na muhalli (ESC) yana daya dag cikin abubuwan da suka fi dacewa da g ba zato ba tsammani na polymers na thermoplastic (musamman amorphoussani a halin yanzu.  A cewar ASTM D883, an ayyana fashewar damuwa a matsayin "tsagewar waje ko ta ciki a cikin robobi da ke haifar da damuwa mai ƙarancin ƙarfi fiye da ƙarfin injinsa na ɗan gajeren lokaci".  Wannan nau'in fashewa yawanci ya haɗa da tsinkewa, tare da ɗan ko babu zanen abu daga saman gazawar sa.   Fasawar damuwa na muhalli na iya yin lissafin kusan kashi 15-30% na duk gazawar bangaren filastik a cikin sabis.  Wannan hali yana da yawa musamman a cikin gilashin, amorphous thermoplastics.  Amorphous polymers suna nuna ESC saboda ƙarancin tsarinsu wanda ke sauƙaƙa wa ruwa ya shiga cikin polymer.  Amorphous polymers sun fi dacewa da ESC a zazzabi sama da zafin canjin gilashin su (Tg) saboda ƙarar ƙarar kyauta.  Lokacin da aka kusanci Tg, ƙarin ruwa zai iya shiga cikin sarkar polymerpolymer. 

 Bayyana polymers ga masu narkewa 
ESC da juriya ga ESC (ESCR) an yi nazarin shekaru da yawa. Bincike ya nuna cewa fallasa polymers ga sunadarai na ruwa yana hanzarta tsarin hauka, yana fara hauka a damuwa wanda ya fi ƙasa da damuwa da ke haifar da hauka a cikin iska. Ayyukan ko dai damuwa ko ruwa Mai lalatawa shi kaɗai ba zai isa ya haifar da gazawar ba, amma a cikin ESC farawa da ci gaban tsagewa ya haifar da haɗin aikin damuwa da ruwa mai lalata. Wadannan ruwan muhalli masu lalata ana kiransu 'masu sinadarai na biyu', sau da yawa suna da kwayoyin halitta, kuma ana bayyana su a matsayin masu narkewa da ba a sa ran su shiga hulɗa da filastik a lokacin rayuwarsa. Rashin nasara ba shi da alaƙa da wakilai na sinadarai na farko, saboda ana sa ran waɗannan kayan su shiga hulɗa da polymer a lokacin rayuwarsa, kuma ta haka ne ana tabbatar da jituwa kafin amfani. A cikin iska, gazawar saboda creep an san shi da raguwar creep, yayin da iska ke aiki a matsayin mai sarrafa filastik, kuma wannan yana aiki a layi daya da fashewar damuwa ta muhalli.

Ya ɗan bambanta da lalacewar polymer a cikin wannan damuwa fashewa baya karya haɗin polymer. Maimakon haka, yana karya haɗin na biyu tsakanin polymers. Wadannan suna karyewa lokacin da matsin lamba na inji ke haifar da raguwa a cikin polymer kuma suna yaduwa da sauri a ƙarƙashin yanayin muhalli mai tsanani. An kuma ga cewa rashin nasara mai ban tsoro a karkashin damuwa na iya faruwa saboda harin reagent wanda ba zai kai farmaki ga polymer a cikin yanayin da ba a damu ba. Rashin damuwa na muhalli yana hanzarta saboda yanayin zafi mafi girma, ɗorawa, karuwar damuwa, da gajiya."Plastics Engineering – November/December 2015 – Plastic Failure through Environmental Stress Cracking". read.nxtbook.com. Retrieved 23 May 2019.

Masu ilimin ƙarfe yawanci suna amfani da kalmar damuwa ta lalace ko lalacewar muhalli don bayyana irin wannan gazawar a cikin karafa.

 Abubuwan da ke rinjayar ESC 
Kodayake an san abin da ya faru na ESC shekaru da yawa, bincike bai riga ya ba da damar yin hasashen irin wannan gazawar ga duk mahalli da kowane nau'in polymer ba. Wasu al'amuran sanannu ne, an rubuta su ko kuma ana iya hango su, amma babu cikakkiyar bayani ga duk haɗuwa da damuwa, polymer da muhalli. Adadin ESC ya dogara da dalilai da yawa ciki har da sinadarin sinadarai na polymer, haɗin kai, crystallinity, tsananin farfajiyar, nauyin kwayoyin da damuwa. Har ila yau, ya dogara da yanayin sinadarai na ruwa da maida hankali, zafin jiki na tsarin da kuma yawan damuwa.

 Hanyoyin ESC 
Akwai ra'ayoyi da yawa g da yadda wasu reagents ke aiki a kan polymers a karkashin damuwa. Saboda ana ganin ESC sau da yawa a cikin polymers amorphous maimakon a cikin polymer semicrystalline, ra'ayoyi game da tsarin ESC sau biyu suna juyawa a kan hulɗar ruwa tare da yankuna amorphous na polymers. Ɗaya daga cikin irin wannan ka'idar ita ce ruwa na iya yadawa cikin polymer, yana haifar da kumburi wanda ke kara motsi na sarkar polymer. Sakamakon shine raguwar damuwa da sauyin zafin jiki na gilashi (Tg), da kuma filastik na kayan wanda ke haifar da hauka a ƙananan damuwa da damuwa. Ra'ayi na biyu shi ne cewa ruwa na iya rage makamashi da ake buƙata don ƙirƙirar sabbin farfajiyoyi a cikin polymer ta hanyar yayyafa saman polymer kuma saboda haka yana taimakawa wajen samar da ramuka, wanda ake zaton yana da mahimmanci a farkon matakan fashewa. ESC na iya faruwa a kai a kai, ko kuma farawa da kuma dakatar da tsari mai hikima

Akwai jerin shaidu da aka samo ta hanyar gwaji don tallafawa ka'idodin da ke sama:

 Da zarar an kafa hauka a cikin polymer wannan yana haifar da hanya mai sauƙi don harin muhalli ya ci gaba kuma tsarin hauka zai iya hanzarta.
 Haɗin sunadarai tsakanin muhalli da polymer yana sarrafa adadin da muhalli zai iya kumbura da filastik polymer.
 Ana rage tasirin ESC lokacin da tsinkaye ke girma sosai. Wannan ya faru ne da farko saboda rashin iyawar ruwa don ci gaba da ci gaban tsagewa.
 Da zarar an raba shi daga sauran sarƙoƙi, polymers sun daidaita, don haka suna ba da damar raguwa.

ESC gabaɗaya yana faruwa a saman filastik kuma baya buƙatar wakili na sinadarai na biyu don shiga cikin kayan sosai, wanda ke barin yawancin kaddarorin ba a canza su ba."Plastics Engineering – November/December 2015 – Plastic Failure through Environmental Stress Cracking". read.nxtbook.com. Retrieved 23 May 2019.

Wani ka'idar don tsarin yaduwar hauka a cikin polymers amorphous Kramer ne ya gabatar da ita. Dangane da ka'idarsa, samar da farfajiyar ciki a cikin polymers yana sauƙaƙe ta hanyar tashin hankali na polymeric wanda aka ƙayyade ta hanyar hulɗar sakandare da gudummawar sarkar ɗaukar kaya wanda dole ne ya karye ko zamewa don samar da farfadowa. Wannan ka'idar tana ba da bayani game da raguwar damuwa da ake buƙata don yada hauka a gaban abubuwan da ke aiki a saman kamar su detergents da zafin jiki.

 Hanyar ESC a cikin polyethylene 
Semi-crystalline polymers kamar polyethylene suna nuna karyewar karyewa a karkashin damuwa idan an fallasa su ga masu fashewar damuwa. A cikin irin waɗannan polymers, ana haɗa crystallites ta hanyar ƙwayoyin ɗaure ta hanyar yanayin amorphous. Kwayoyin ɗaure suna taka muhimmiyar rawa a cikin kayan aikin injiniya na polymer ta hanyar canja wurin kaya. Masu fashewar damuwa, kamar su detergents, suna aiki don rage ƙarfin haɗin kai wanda ke kula da kwayoyin ɗaure a cikin lu'ulu'u, don haka sauƙaƙe "cirewa" da rarraba su daga lamellae. A sakamakon haka, ana fara fashewa a ƙimar damuwa ƙasa da matakin damuwa na kayan.

Gabaɗaya, tsarin damuwa na muhalli a cikin polyethylene ya haɗa da rarraba kwayoyin ɗaure daga lu'ulu'u. Yawan kwayoyin ɗaure da ƙarfin lu'ulu'u da ke ɗaure su ana ɗaukar su abubuwan sarrafawa wajen ƙayyade juriyar polymer ga ESC.

 Bayyana ESC 
Ana amfani da hanyoyi daban-daban don kimanta juriya ta polymer ga fashewar damuwa ta muhalli. Hanyar da aka saba amfani da ita a masana'antar polymer ita ce amfani da jig na Bergen, wanda ke ba da samfurin zuwa nau'i mai canzawa yayin gwaji ɗaya. Sakamakon wannan gwajin ya nuna matsanancin damuwa ga fashewa, ta amfani da samfurin daya kawai. Wani gwajin da aka yi amfani da shi sosai shine gwajin Bell Telephone inda aka fallasa sassan da aka karkatar da su ga ruwa mai ban sha'awa a ƙarƙashin yanayin sarrafawa. Bugu da ƙari, an haɓaka sabbin gwaje-gwaje inda aka kimanta lokacin farawa a ƙarƙashin ɗorawa da kuma mai narkewa mai ƙarfi (10% Igepal CO-630 bayani). Wadannan hanyoyin sun dogara da indentor don jaddada kayan a hanyar biaxially, yayin da suke hana maida hankali ga damuwa. Polymer mai jaddada yana zaune a cikin wakili mai tsananin fushi kuma ana kallon filastik mai jaddara a kusa da indentor don kimanta lokacin da za a samu fashewa, wanda shine hanyar da aka ƙayyade juriyar ESC. Kayan gwaji don wannan hanyar an san shi da Telecom kuma yana samuwa a kasuwanci; gwaje-gwaje na farko sun nuna cewa wannan gwajin yana ba da sakamako daidai da ASTM D1693, amma a ɗan gajeren lokaci. Bincike na yanzu yana ma'amala da aikace-aikacen injiniyoyin fashewa ga nazarin abubuwan da suka faru na ESC.   A taƙaice, duk da haka, babu wani mai bayyanawa guda ɗaya wanda ya dace da ESC - maimakon haka, takamaiman fashewa ya dogara da kayan, yanayi, da kuma sinadarai na biyu da ke akwai.

An yi amfani da microscopy na lantarki da hanyoyin fractographic a tarihi don nazarin tsarin gazawar, musamman a cikin polyethylene mai yawa (HDPE). Kashewar daskarewa ya tabbatar da amfani sosai don bincika kinetics na ESC, yayin da suke ba da hoto a lokacin yaduwar fashewa.

 Rashin ƙarfi a matsayin ma'auni na tsayayyar tsananin muhalli (ESCR) 
Akwai hanyoyi daban-daban don auna ESCR. Koyaya, tsawon lokacin gwaji da tsada mai yawa da ke tattare da waɗannan hanyoyin sun rage ayyukan R & D don tsara kayan da ke da tsayayya da raguwar damuwa. Don shawo kan waɗannan ƙalubalen, SABIC ta haɓaka sabuwar hanya mai sauƙi da sauri don tantance ESCR don kayan polyethylene (HDPE). A cikin wannan hanyar, ana hasashen juriya na saurin tsagewa ko tsagewar muhalli daga ma'auni mai sauƙi a zafin jiki na 80 ° C.Kureleca, L.; Teeuwenb, M.; Schoffeleersb, H.; Deblieckb, R. (2005). "Strain hardening modulus as a measure of environmental stress crack resistance of high density polyethylene". Polymer. 46 (17): 6369–6379. doi:10.1016/j.polymer.2005.05.061. Lokacin da polyethylene ya lalace a ƙarƙashin tashin hankali na uniaxial, kafin yawan amfanin ƙasa, ƙaƙƙarfan lokacin crystalline na polymer yana fuskantar ƙananan nakasawa yayin da yankunan amorphous suna lalacewa sosai.  Bayan ma'anar yawan amfanin ƙasa amma kafin abun ya sha wahala, lamellae crystalline yana zamewa inda duka lokaci na crystalline da amorphous yanki suna ba da gudummawa ga ɗaukar nauyi da damuwa.  A wani lokaci, yankunan amorphous za su shimfiɗa cikakke a lokacin da taurin zai fara.  A cikin yanki mai taurin rai, yankunan amorphous masu elongated sun zama lokacin ɗaukar kaya yayin da lamellae crystalline ke fuskantar karaya kuma yana buɗewa don daidaitawa don canjin iri.  Sarƙoƙi masu ɗaukar kaya a cikin yankunan amorphous a cikin polyethylene an yi su ne da ƙwayoyin taye da sarƙoƙi.  Saboda muhimmiyar rawar taye-kwayoyin da ke tattare da juna a cikin tsayayya da damuwa na muhalli a cikin polyethylene, yana biye da cewa ESCR da halayen hardening na iya kasancewa da alaƙa sosai.[1]. 

A cikin hanyar karfafawa, ana lissafin gangaren yankin karfafawa (sama da rabo na halitta) a cikin ƙuƙwalwar damuwa ta gaskiya kuma ana amfani da ita azaman ma'auni na ESCR. Wannan gangaren ana kiransa strain hardening modulus (Gp). Ana lissafin ƙarfin ƙarfin ƙarfin a duk yankin da ke ƙarfafa ƙarfin a cikin yanayin damuwa na gaskiya. Yankin da ke karfafawa na ƙuƙwalwar damuwa ana ɗaukarsa a matsayin ɓangaren da ke da rikice-rikice sama da rabo na halitta, wanda aka ƙayyade ta kasancewar yaduwar wuyan, kuma a ƙasa da matsakaicin tsawo.Kureleca, L.; Teeuwenb, M.; Schoffeleersb, H.; Deblieckb, R. (2005). "Strain hardening modulus as a measure of environmental stress crack resistance of high density polyethylene". Polymer. 46 (17): 6369–6379. doi:10.1016/j.polymer.2005.05.061. Matsakaicin ƙarfin ƙarfin lokacin da aka auna shi a 80 °C yana da hankali ga abubuwan kwayoyin iri ɗaya waɗanda ke sarrafa jinkirin tsayayya a cikin HDPE kamar yadda aka auna ta hanyar gwajin ESCR mai sauri inda ake amfani da wakili mai aiki. An gano cewa ƙarfin ƙarfin ƙarfin ƙarfin da ƙimar ESCR don polyethylene suna da alaƙa sosai da juna. 
Misali a bayyane na buƙatar tsayayya da ESC a rayuwar yau da kullun shine masana'antar kera motoci, inda yawancin polymers daban-daban ke ƙarƙashin ruwa da yawa. Wasu daga cikin sunadarai da ke cikin waɗannan hulɗar sun haɗa da man fetur, ruwan birki da maganin tsaftacewa na iska. Plasticisers leaching daga PVC kuma na iya haifar da ESC na dogon lokaci, misali. Ɗaya daga cikin misalai na farko na matsalar ya shafi ESC na LDPE. An fara amfani da kayan ne don rufe igiyoyin lantarki, kuma fashewa ya faru ne saboda hulɗar rufin tare da mai. Maganin matsalar ya kasance ne ta kara nauyin kwayoyin polymer. An kirkiro gwajin fallasawa ga mai tsabta mai ƙarfi kamar Igepal don ba da gargadi ga ESC.

 Styrene acrylonitrile mai saukin kamuwa da ketone solvent 
Wani takamaiman misali ya zo ta hanyar maɓalli na piano da aka yi daga allurar styrene acrylonitrile (SAN).  Maɓallin yana da ƙarshen ƙugiya wanda ke haɗa shi da maɓuɓɓugar ƙarfe, wanda ke sa maɓallin ya koma baya bayan an buga shi.  A lokacin hada piano an yi amfani da manne, kuma abin da ya wuce gona da iri wanda ya zube a wuraren da ba a bukata an cire shi ta amfani da sinadarin ketone.  Wasu tururi daga wannan kaushi yana takushe akan saman ciki na maɓallan piano.  Wani lokaci bayan wannan tsaftacewa, karaya ya faru a mahadar inda ƙarshen ƙugiya ya hadu da bazara.

Don tantance dalilin karyewar, an dumama maɓallin piano na SAN sama da zafin Canjin gilashi na ɗan gajeren lokaci. Idan akwai matsin lamba a cikin polymer, yanki zai ragu lokacin da aka riƙe shi a irin wannan zafin jiki. Sakamakon ya nuna cewa akwai raguwa mai mahimmanci, musamman a ƙarshen ƙugiya-spring junction. Wannan yana nuna maida hankali kan damuwa, mai yiwuwa haɗuwa da raguwar damuwa daga samarwa da aikin bazara. An kammala cewa kodayake akwai damuwa mai raguwa, fashewar ta kasance ne saboda haɗuwa da damuwa mai ƙarfi daga aikin bazara da kasancewar mai narkewa na ketone.

 Tsarin polymer mai saukin kamuwa da sinadarin siminti 
Kayan aikin polymer na iya fama da gazawar kwatsam yayin yin simintin, wanda gabaɗaya yana da alaƙa da matsin lamba da jikakken simintin ke yi akan siraran ƙirar filastik.  Irin wannan gazawar za a iya ƙara haɓakawa ta hanyar ɓarnawar ɓacin rai na ƙwanƙolin rigar kankare, wanda ke da pH na kusan 13. Wasu thermoplastics sun fi tasiri sosai, musamman waɗanda ke cikin nau'in amorphous, kamar PLA, PET da PC.  Wannan al'amari ya ma fi bayyana a cikin 3D-bugu na polymer formworks, inda akwai dangantaka tsakanin muhalli danniya fasa inji da Layer interface grooves, inda damuwa mayar da hankali..

 Dubi kuma 

 Injiniyanci na lalatawa
 Gudun daji
 Yankin da ke fashewa
 Rashin jituwa
 Rashin damuwa na muhalli
 Injiniyanci
 Injiniyan polymer na bincike
 Rashin Rashin Rarraba
 Rashin saurin
 Rashin damuwa Rashin lalacewa
 Rashin tsari
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