Ba kamar thermoplastics, elastomers yawanci ana amfani da su akan yanayin zafi da yawa kuma suna da girma sama da yanayin canjin gilashin su (Tg). Fa'idodin elastomers akan thermoplastics shine ikon su na dawo da kusan gaba ɗaya daga yanayin juzu'i (mai girman ƙarfi), da kuma elasticity ɗin su na gabaɗaya, ƙarancin tauri da ƙananan kaddarorin modulus. Lokacin da aka yi amfani da elastomers a ƙasa da zafin jiki, suna nuna haɓakar taurin kai, haɓakar modules, da raguwar elasticity. Lokacin da aka yi amfani da elastomers a ƙasa da zafin jiki, akwai yanayi don taurin haɓaka, haɓakawa don haɓakawa, elasticity don raguwa (ƙananan ƙarfi) da matsawa saitin ƙara. Dangane da matsalar elastomer, al'amura guda biyu na iya faruwa a lokaci guda - tauraruwar gilashi da ɓangarorin crystallization - CR, EPDM, NR wasu misalan elastomers ne waɗanda ke nuna crystallization.
1. Bayanin gwajin ƙananan zafin jiki
Brittleness, matsawa m nakasawa, ja da baya, hardening da cryogenic hardening da aka yi amfani da shekaru masu yawa domin ya kwatanta polymer Properties a low yanayin zafi. Matsakaicin danniya sabon abu ne kuma yana mai da hankali kan tantance ƙarfin rufe abu na wani lokaci a ƙarƙashin yanayi daban-daban na muhalli.
2. Rage zafin jiki
ASTM D 2137 yana bayyana zafin jiki mara ƙarfi a matsayin mafi ƙarancin zafin jiki wanda roba mai lalacewa ba zai nuna karaya ko fashewa a ƙarƙashin ƙayyadadden yanayin tasiri ba. Ana shirya samfurori guda biyar na roba na siffar da aka riga aka ƙaddara, an sanya su a cikin ɗaki ko matsakaicin ruwa, an sanya shi a yanayin zafin jiki na 3 ± 0.5min, sa'an nan kuma an ba da tasirin tasiri na 2.0 ± 0.2m / s. Ana cire samfuran kuma an yi gwajin tasiri ko fashewa. Ana cire samfurin kuma an gwada don tasiri ko karaya, duk ba tare da lalacewa ba. An sake maimaita gwajin har zuwa zafin jiki mai rauni - mafi ƙarancin zafin jiki wanda ba a sami karaya ba ya kusan 1 ° C.
3. Low Temperature Compression Set and Low Temperature Hardening
Hanyar gwaji don saitin matsawa mai ƙananan zafin jiki yana kusa da wancan don daidaitaccen saitin matsawa, sai dai yanayin zafin jiki yana sarrafa ta wasu hanyoyin makamashi, kamar busassun ƙanƙara, nitrogen ruwa, ko hanyoyin inji, kuma ƙimar tana cikin ± 1 ° C na zafin jiki da aka saita. Bayan murmurewa daga na'urar, ana kuma sanya samfurin a ƙananan zafin jiki da aka saita kuma an tsara shi zuwa diamita na 29 mm da kauri na 12.5 mm. Saitin matsawa ƙananan zafin jiki hanya ce kai tsaye don rufe aikace-aikacen fili da ake tambaya. Kwanciyar damuwa shine hanya kai tsaye kuma za'a tattauna daga baya. Ƙarƙashin zafin jiki kuma yawanci ana ƙaddara ta amfani da samfurin vulcanized compression set (29mm x 12.5mm), amma an sake gwada shi a ƙananan zafin jiki, wanda yayi daidai da na saitin matsawa, sannan kuma a yanayin zafi ɗaya kamar yadda aka saita yanayin zafin su. Hardening da low-zazzabi matsawa saitin an kai tsaye shafi sanyaya, amma kuma da hali na polymer to crystallize, tare da kudi na crystallization dogara a kan zafin jiki, misali, CR crystallizes sauri a kusa da -10 ° C, sa'an nan ragewa a ƙananan yanayin zafi, yafi saboda da immobility na polymer sarkar segments (da kwayoyin chains daskare kafin daskare sarƙoƙi).
4. Gehman Ƙarƙashin zafin jiki
ASTM D 1053 yana bayanin hanyar taurin ƙananan zafin jiki kamar haka: jerin samfuran polymer na roba suna kayyade a kan waya tare da sananniya mai tsauri, kuma ɗayan ƙarshen waya an haɗa shi da kan torsion wanda zai iya ba da izinin murɗa waya. Ana nutsar da samfuran a cikin matsakaicin matsakaicin zafi a wani takamaiman zafin jiki ƙasa da al'ada, lokacin da aka karkatar da kan torsion da 180 °, sa'an nan kuma ana murɗa samfuran da adadin (kasa da 180 °) wanda ya dogara da juzu'i na sassauci da taurin samfurin. Sa'an nan kuma yi amfani da adadin goniometer don sanin adadin jujjuya samfurin, kusurwar karkatarwa da taurin kayan roba. Ana ƙara yawan zafin jiki na tsarin a hankali a wannan lokaci, kuma ana samun makirci na kusurwar karkatarwa da zafin jiki. Yanayin yanayin da modules ya kai T2, T10, da T100 yawanci ana rubuta su daidai da ƙimar modul a zafin ɗaki.
5. Ƙarƙashin Ƙarƙashin Zazzabi (Gwajin TR)
Ana amfani da gwajin TR don ƙididdige ikon samfuri a cikin yanayin jinkiri lokacin da nakasar dindindin na dindindin da shakatawa na damuwa da aka ƙaddara ta matsananciyar damuwa ana amfani da su don ƙayyade ƙananan tasirin zafi. Kamar yadda aka bayyana a baya, da yawa polymers kamar NR da PVC za su crystallize a low yanayin zafi, amma mikewa kuma iya crystallize, haifar da ƙarin dalilai lokacin da kallon low zafin jiki Properties. Don aikace-aikacen kimantawa kamar dakatarwar shaye-shaye, TR ƙarƙashin tashin hankali ya dace sosai kuma ana amfani dashi akai-akai. A cikin wannan gwajin, samfurin yana elongated (sau da yawa da 50% ko 100%) kuma a daskare a cikin elongated jihar. An saki samfurin, a lokacin da zafin jiki ya tashi a ƙayyadaddun ƙididdiga don auna dawo da samfurin, an auna tsayin raguwa kuma an rubuta elongation. Yanayin zafi wanda samfurin ke raguwa da 10%, 30%, 50%, da 70% yawanci ana lura dashi azaman TR10, TR30, TR50, da TR70. TR10 yana da alaƙa da zafin jiki na brittleness; TR70 yana da alaƙa da nakasawa na dindindin na samfurin a cikin matsananciyar zafi; kuma ana amfani da bambanci tsakanin TR10 da TR70 don auna crystallization na samfurin (mafi girma bambanci, mafi girma da hali don crystallize).
6 . Ƙarƙashin Ƙarƙashin Ƙwararrun Ƙwararru (CSR)
Ana iya amfani da gwajin CSR don yin tsinkaya game da aiki da rayuwar kayan rufewa. Lokacin da aka ba da fili na elastomeric gyare-gyare akai-akai, an halicci ƙarfin haɗin gwiwa, kuma ikon kayan don kula da wannan karfi a cikin wani yanki na muhalli yana auna ikonsa na hatimi. Dukansu hanyoyin jiki da na sinadarai suna ba da gudummawa ga shakatawa na danniya, dangane da lokaci da zafin jiki, wani abu zai mamaye, ana lura da shakatawa na jiki a ƙananan yanayin zafi, nan da nan bayan da aka ba da damuwa, wanda zai haifar da sake tsara sarkar da canje-canje a cikin roba-filler da filler-filler surfaces, kuma shakatawa na tsarin kawar da damuwa yana canzawa. A yanayin zafi mafi girma, nau'in sinadarai yana ƙayyade adadin shakatawa, lokacin da matakan jiki sun riga sun kasance ƙananan kuma shakatawar sinadarai ba zai iya jurewa ba, yana haifar da raguwar sarkar da haɗin kai. Yin hawan zafin jiki ko haɓakar zafin jiki ba zato ba tsammani na iya yin tasiri akan shakatawar damuwa a cikin elastomers. A lokacin gwajin CSR, ana sanya samfurin gwajin
A lokacin gwajin CSR, annashuwa damuwa yana ƙaruwa lokacin da samfurin gwajin ya kasance ƙarƙashin yanayin zafi. Idan shakatawa na danniya ya faru a farkon gwajin, adadin ƙarin shakatawa yana ƙaruwa da farko kuma yana da matsakaicin ƙimar yayin zagayowar farko. A cikin wani tensile babban gwajin yanki don samar da gasket samfurori (19mm m diamita, ciki diamita na 15mm), tare da wani roba tsayarwa za a matsa zuwa ga samfurin zuwa dakin zafin jiki kauri na 25%, da kuma a 25 ℃ a cikin muhalli gwajin jam'iyyar, da zazzabi a 25 ℃ don kula da 24h, sa'an nan kuma kula da 24h ℃, sa'an nan kuma kasa zuwa -2h. tsakanin -20 ~ 110 ℃ sake zagayowar na 24h, da dukan gwajin lokaci a gwajin zazzabi, da gwajin zafin jiki, ci gaba da ƙarfi kayyade. Ana yin ma'aunin ƙarfin ci gaba a duk lokacin gwaji a zazzabi na gwaji.
7. Tasirin Abun Ethylene
7.1 Abubuwan da ke cikin Ethylene suna da tasiri mafi girma akan ƙarancin zafin jiki na EPDM polymers. Polymers tare da abun ciki na Ethylene daga 48% zuwa 72% an kimanta su a ƙarƙashin ingantattun hanyoyin rufewa. Duk nufin rage bambance-bambance a cikin dankowar wata ta hanyar gabatar da ENB a cikin waɗannan polymers daban-daban.
Rubber EPDM amorphous ne idan rabon ethylene/propylene yayi daidai kuma rarraba monomers guda biyu a cikin sarkar polymer bazuwar. EPDM tare da 48% da 54% abun ciki ethylene baya yin crystallize a ko sama da zafin dakin. Lokacin da abun ciki na ethylene ya kai 65%, jerin ethylene sun fara karuwa a lamba da tsayi kuma suna iya samar da lu'ulu'u, waɗanda aka lura a cikin kololuwar crystallization a kan madaidaicin DSC a kusa da 40 ° C. Mafi girman kololuwar DSC, mafi girman lu'ulu'u da ke samuwa.
7.2 Baya ga tasirin abun ciki na ethylene akan ƙananan kaddarorin zafin jiki da aka tattauna daga baya, girman crystallite yana rinjayar sauƙin haɗuwa da sarrafa abubuwan da ke ɗauke da lu'ulu'u. Girman girman girman crystallite, ana buƙatar ƙarin zafi da aiki mai ƙarfi a matakin haɗuwa don cikar cakuda polymer tare da sauran abubuwan haɗin gwiwa. Ƙarfin roba mai ƙarfi na mahadi na EPDM yana ƙaruwa tare da haɓaka abun ciki na ethylene. A cikin gyare-gyaren hatimi inda aka auna tasirin abun ciki na ethylene, haɓakar abun ciki na ethylene daga 50% zuwa 68% ya haifar da aƙalla haɓakar ƙarfin roba sau huɗu. Har ila yau, taurin-zazzabi na ɗaki yana ƙaruwa tare da haɓaka abun ciki na ethylene. Shore A taurin mannen polymer amorphous shine 63 °, yayin da Shore A taurin polymer tare da mafi girman abun ciki na ethylene shine 79°. Wannan shi ne saboda karuwa a cikin jerin ethylene, karuwa a cikin crystallization a cikin m, da kuma karuwa mai dacewa a cikin polymers na thermoplastic.
7.3 Lokacin da aka auna taurin a ƙananan yanayin zafi, ya bambanta da polymers tare da babban abun ciki na ethylene, ƙwayoyin amorphous suna nuna ƙananan canji a cikin taurin, yayin da canji a cikin taurin mafi girman abun ciki na ethylene ba ya nuna alamar layi kuma taurin ya kasance mai girma a dakin da zafin jiki, saboda haka polymers dauke da mafi girma ethylene abun ciki na ci gaba da samun mafi girma taurin a low zazzabi.
7.4 Saitin matsawa ya dogara da yawa akan zafin gwajin. Idan an gwada shi a 175 ° C, babu bambanci a cikin matsawa saiti tsakanin kowane nau'in polymers (saitin yana tasiri ta hanyar zane na fili da zaɓin tsarin vulcanization). Bayan narkewar lu'ulu'u na ethylene, polymer yana nuna nau'in amorphous, kuma don bincika tasirin abun ciki na ethylene, an yi gwaje-gwaje a 23 ° C. Polymers da ke da babban abun ciki na ethylene a fili suna da nakasu na dindindin (fiye da sau biyu), kuma tasirin abun cikin ethylene ya fi girma idan an gwada shi a -20 ° C da -40 ° C. Polymers tare da fiye da 60% abun ciki na ethylene suna da babban nakasar dindindin (> 80%); a -40°C, kawai cikakken amorphous polymers suna da ƙarancin nakasu na dindindin (17%).
7.5 Tasirin Abun Ethylene akan Ƙarfin Ƙarfin Zazzabi daga Gwajin Gehman. Idan aka ba da yanayin zafi, mafi girman kusurwar, ƙananan haɓakar ƙima (ko karuwa a modules). A ƙananan yanayin zafi, ƙarfin ƙarfin ƙarfin yana ƙaruwa sosai tare da haɓaka abun ciki na ethylene. Domin amorphous polymers, T2 shine -47 ° C, yayin da mafi girman ethylene abun ciki polymer yana da T2 na -16 ° C kawai.
7.6TR Auna raguwar dawo da samfurori bayan daskarewa tsawo, abun cikin ethylene yana da tasiri mai mahimmanci akan hanyar gwajin, wanda kuma yayi kama da gwajin Gehman.
Wannan yayi kama da gwajin Gehman. Ƙunƙarar (%) na nau'in polymers daban-daban ya bambanta a matsayin aikin zafin jiki, tare da amorphous polymers suna da mafi girman farfadowa na raguwa a ƙananan yanayin zafi; duk da haka, kamar yadda aka annabta, farfadowa yana raguwa yayin da abun ciki na ethylene ya karu a yanayin da aka ba.
farfadowa ya lalace. Darajar TR10 ya bambanta daga -53 ° C don amorphous polymers zuwa -28 ° C don polymers tare da babban abun ciki na ethylene.
7.7 Zagayowar shakatawa na damuwa (CSR).
Zagayowar Matsa mahadi, ba su damar shakatawa a 25 ° C na sa'o'i 24, sa'an nan kuma sanya su a cikin sake zagayowar yanayin zafi daga -20 ° C zuwa 110 ° C na lokaci-lokaci na sa'o'i 24. Lokacin da aka matsa a karon farko, bayan lokacin daidaitawa, crystalline polymer E yana da asarar damuwa fiye da amorphous polymer, kuma lokacin da aka saukar da shi zuwa -20 ° C ƙarfin rufewa na polymers guda biyu ya ragu, yayin da amorphous polymer A yana da babban riƙewa na damuwa (mafi girma F / F0). Dumama fili zuwa 110 ° C ya mayar da ƙarfin rufewa, kuma lokacin da aka dawo da shi zuwa -20 ° C, sauran ƙarfin rufewa na polymer ɗin crystalline bai wuce 20% na ƙimarsa ba, wanda yawanci ana la'akari da shi don mafi yawan aikace-aikace, tare da amorphous polymer yana riƙe da fiye da 50% na ƙarfin rufewa, kuma polymer amorphous yana sake samun farfadowa fiye da polymerline. Zagaye na gaba ya haifar da irin wannan ƙarshe. A bayyane yake cewa amorphous polymers sun fi girma don aikace-aikacen rufewa inda ake buƙatar babban aiki da ƙananan zafin jiki.
8. Tasirin Abun Diolefin
Don samar da madaidaicin madaidaicin da ake buƙata don vulcanization, diolefins waɗanda ba a haɗa su kamar ENB, HX da DCPD ana ƙara su zuwa polymers na ethylene propylene. Ɗayan haɗin kai guda biyu yana amsawa a cikin matrix polymer, yayin da na biyu yana aiki a matsayin mai dacewa ga sarkar kwayoyin polymerized kuma yana ba da ma'anar ɓarna don vulcanization rawaya sulfur. An kimanta tasirin ENB a cikin bayanan mashaya na iska (ruwan sama). An kwatanta polymers dauke da 2%, 6% da 8% ENB. Bugu da ƙari na ENB yana da tasiri mai mahimmanci akan halayen vulcanization da ƙananan haɗin haɗin gwiwa. Modulus ya karu yayin da tsawo ya ragu sosai. Taurin ya karu kuma saitin matsawa ya inganta yayin hawan zafin jiki. Yayin da abun ciki na ENB ya karu, lokacin caji ya zama guntu.
ENB abu ne mai amorphous, kuma lokacin da aka ƙara shi zuwa kashin baya na polymer, yana rushe crystallization na ɓangaren ethylene na polymer, ta yadda za'a iya samun polymers tare da abun ciki na ethylene guda ɗaya, kuma mafi girman abun ciki na ENB yana inganta ƙananan yanayin zafi. A yanayin zafi na ɗaki, babban abun ciki na ENB yana ɗan inganta saitin matsawa saboda ingantacciyar ƙima. Koyaya, a ƙananan yanayin zafi, saitin matsawa na polymers tare da babban abun ciki na ENB yana da mahimmanci fiye da na polymers tare da abun ciki na 2% ENB. Tasirin abun ciki na ENB akan zafin jiki na raguwa, raguwar zafin jiki, da gwajin Gehman bai nuna wani bambanci mai mahimmanci ba a cikin zafin jiki na brittleness tsakanin polymers gabaɗaya, kuma don gwajin Gehman da gwajin TR, kowane polymer ya nuna haɓakawa a cikin ƙananan yanayin zafin jiki tare da ƙara yawan abun ciki na ENB.
9. Tasirin Dankowar Mooney akan Ƙananan Zazzabi Properties
An san cewa mooney danko (kwayoyin kwayoyin halitta) yana da tasiri mai mahimmanci akan halayen sarrafawa na elastomers. A cikin aikace-aikacen extrusion da gyare-gyare A cikin aikace-aikacen extrusion da gyare-gyare, yana da mahimmanci don zaɓar wani fili tare da ƙimar dankon Mooney mai dacewa. Yin amfani da tsari iri ɗaya da aka yi amfani da shi don bincika tasirin monomer na uku, ENB, akan kaddarorin ƙananan zafin jiki don bincika dankon Mooney, an kwatanta polymers tare da ƙoƙon Mooney na 30, 60, da 80, kuma ƙarancin Mooney na mahadi ya ƙaru yayin da Mooney danko na polymers da aka yi amfani da su ya karu. Ƙarfin ɗaure, modules, da ɗanyen ƙarfin roba ya ƙaru tare da ƙara danƙowar Mooney. Tasirin dankowar Mooney akan ƙarancin zafin jiki na EPDM ba shi da mahimmanci. Koyaya, matsi na dindindin nakasawa a cikin ɗaki, -20°C da -40°C yana ƙaruwa tare da ƙara yawan ƙwayoyin ƙwayoyin cuta. Duk da haka, matsawa da aka saita a zafin jiki, -20 ° C da -40 ° C ba su canza sosai ba tare da karuwar kwayoyin halitta, yayin da matsawa da aka saita a yanayin zafi mai girma (175 ° C) ya nuna wasu canje-canje ga mafi girman mooney viscosities na EPDM adhesives.
10. Kammalawa
Abubuwan da ke cikin ethylene da diolefin suna da tasiri mai mahimmanci akan aikin elastomers na EPDM a cikin ƙananan aikace-aikacen zafin jiki, tare da polymers tare da ƙananan abun ciki na ethylene suna aiki da kyau da kuma polymers tare da babban abun ciki na diolefin yana inganta saboda rushewar crystallization na ethylene sashi na polymer. Ya kamata a yi amfani da ƙananan abubuwan abun ciki na ethylene lokacin da ƙarancin zafin aiki ya kasance iyakance.
