Kuhambana na ti thermoplastics, ti elastomers hi ntolovelo titirhisiwa eka mahiselo yohambana hambana naswona ehenhla swinene ka mahiselo ya tona ya glass transition (Tg). Swipfuno swa ti elastomers eka ti thermoplastics i vuswikoti bya tona byo vuyelela kwalomu ka hinkwaswo kusuka eka xiyimo xa tensile (high elasticity), xikan’we na generalized elasticity ya tona, low hardness xikan’we na swivumbeko swa modulus yale hansi. Loko ti elastomer ti tirhisiwa ehansi ka mahiselo ya kamara, ti kombisa ku tlakuka ka ku tiya, ku tlakuka ka modulus, na ku hunguteka ka elasticity. Loko ti elastomers titirhisiwa ehansi ka mahiselo ya kamara, kuna ntolovelo wa ku tiya ka ku tlakuka, modulus kuva yi engeteleka, elasticity yihunguteka (low tensile) xikan’we na compression leyi vekiweke kuva yi tlakuka. Kuya hi xiphiqo xa elastomer, swiendlakalo swimbirhi swinga humelela hi nkarhi wun’we - ku nonoka ka nghilazi na ku crystallization ka xiphemu - CR, EPDM, NR i swikombiso swin’wana swa ti elastomers leti kombisaka crystallization.
1. Nkatsakanyo wa ku kamberiwa ka mahiselo ya le hansi
Brittleness, compression permanent deformation, retraction, hardening na cryogenic hardening switirhisiwile kuringana malembe yotala leswaku kuta kombisiwa swivumbeko swa polymer eka mahiselo yale hansi. Compressive stress relaxation i yintshwa swinene naswona yi kongomisa eka ku kumisisa matimba yo pfalela ya nchumu eka nkarhi wokarhi ehansi ka swiyimo swohambana hambana swa mbango.
2. Ku hisa ka Brittleness
ASTM D 2137 yi hlamusela mahiselo ya brittleness tani hi mahiselo yale hansi swinene laha rhaba leyi vulcanized yingata kombisa ku tshoveka kumbe ku pandzeka ehansi ka swiyimo leswi boxiweke swa nkucetelo. Ntlhanu wa swikombiso swa rhaba swa xivumbeko lexi vekiweke ka ha ri emahlweni swa lulamisiwa, swi vekiwa eka kamara kumbe liquid medium, swi endliwa eka mahiselo lawa ya vekiweke kuringana 3±0.5min, kutani swi nyikiwa rivilo ra ku khumbeka ra 2.0±0.2m/s. Swikombiso swa susiwa kutani swi endliwa xikambelo xa ku khumbeka kumbe ku phatluka. Xikombiso xa susiwa kutani xi kamberiwa ku vona loko xi khumbekile kumbe xi tshovekile, hinkwaswo swi nga onhakanga. Xikambelo lexi xi phindhiwile kuya fika eka mahiselo ya brittleness - mahiselo yale hansi swinene laha kunga kumekanga ku tshoveka akuri ekusuhi swinene na 1°C.
3. Seti ya Ntshikelelo wa Mahiselo ya le Hansi na Ku nonoka ka Mahiselo ya le Hansi
Endlelo ra xikambelo xa low-temperature compression set ri le kusuhi swinene na leri ra standard compression set, handle ka leswaku mahiselo ya lawuriwa hi ndlela yin’wana ya eneji, kufana na dry ice, liquid nitrogen, kumbe tindlela ta michini, naswona nhlayo yile ndzeni ka ± 1°C ya mahiselo lawa ya vekiweke. Endzhaku ko vuyiseriwa kusuka eka fixture, xikombiso xitlhela xivekiwa eka mahiselo yale hansi lawa ya vekiweke naswona xi vumbiwa kuya eka diameter ya 29 mm xikan’we naku enta ka 12.5 mm. Low-temperature compression set i ndlela leyinga kongomangiki yaku pfalela switirhisiwa swa compound leyi ku vulavuriwaka hi yona. Compressive stress relaxation i ndlela yo kongoma naswona yita xopaxopiwa endzhaku. Ku nonoka ka mahiselo yale hansi switala ku kumiwa hiku tirhisa vulcanized compression set specimen (29mm x 12.5mm), kambe switlhela swikamberiwa eka vulawuri bya mahiselo yale hansi, leswi fanaka na leswinga eka compression set, kutani nakambe eka mahiselo lawa ya fanaka na mahiselo ya vona lawa ya vekiweke. Ku nonoka na low-temperature compression set swi khumbeka hiku kongoma hiku kufumela, kambe switlhela swi khumbeka hiku olova ka polymer kuva yi crystallize, laha mpimo wa crystallization wutitshegeke hi mahiselo, xikombiso, CR yi crystallize hiku hatlisa swinene kwalomu ka -10°C, kutani yihunguteka eka mahiselo yale hansi, ngopfu ngopfu hikokwalaho ka ku nga fambi ka swiphemu swa polymer chain (ti molecular chains ti freeze emahlweni ku hleriwa hi vuntshwa).
4. Ku nonoka ka Gehman hi Mahiselo ya le Hansi
ASTM D 1053 yi hlamusela ndlela yo nonokisa hi mahiselo yale hansi hindlela leyi landzelaka: nxaxamelo wa swikombiso swa elastic polymer swi khomanisiwile hiku tiya eka waya lowungana torsional constant leyi tivekaka, naswona makumu yan’wana ya waya ya khomanisiwile na nhloko ya torsion leyi kotaka ku pfumelela waya ku soholotiwile. Ti specimens ti nyuperisiwa eka heat transfer medium eka mahiselo yokarhi yale hansi ka ntolovelo, hi nkarhi walowo nhloko ya torsion yi soholotiwile hi 180°, kutani swikombiso swi soholotiwile hi nhlayo (ehansi ka 180°) leyi titshegeke hi inverse ya specimen’s flexibility na stiffness. Kutani tirhisa nhlayo ya goniometer ku kumisisa nhlayo ya specimen twist, angle ya twist xikan’we naku tiya ka swilo swa rhaba. Mahiselo ya sisiteme ya engeteriwa hakatsongotsongo eka ndzhawu leyi, naswona ku kumiwa plot ya angle ya twist kuya hi mahiselo. Mahiselo lawa modulus yifikaka eka T2, T10, na T100 hi ntolovelo ya rhekhodiwa tani hi leyi ringanaka na nhlayo ya modulus eka mahiselo ya kamara.
5. Ku tlheriseriwa endzhaku ka mahiselo ya le hansi (TR Test) .
Xikambelo xa TR xitirhisiwa ku kambela vuswikoti bya xikombiso eka xiyimo xa tensile loko compressive permanent deformation na compressive stress relaxation leyi kumiweke hi compressive stress switirhisiwa ku kumisisa mbuyelo wa mahiselo yale hansi. Tani hilaha swinga hlanganisiwa hakona ekusunguleni, ti polymers totala tofana na NR na PVC tita crystallize eka mahiselo yale hansi, kambe ku ololoka swinga tlhela swi crystallize, leswi yisaka eka swilo swo engetelela loko ku langutiwa swivumbeko swa mahiselo yale hansi. Eka switirhisiwa swo kambela swofana na exhaust suspension, TR ehansi ka tension yifanele swinene naswona yitala kutirhisiwa. Eka xikambelo lexi, xikombiso xi lehisiwile (hakanyingi hi 50% kumbe 100%) naswona xi titimela eka xiyimo xo leha. Xikombiso xa humesiwa, laha mahiselo ya tlakusiweke hi mpimo lowu vekiweke ku pima ku vuyelela ka xikombiso, ku leha ka ku hunguteka ka pimiwa naswona ku leha ka kona ku rhekhodiwa. Mahiselo lawa xikombiso xihungutekaka eka wona hi 10%, 30%, 50%, na 70% hi ntolovelo ya xiyiwa tani hi TR10, TR30, TR50, na TR70. TR10 yi fambelana na mahiselo ya brittleness; TR70 yi fambelana na ku onhaka ka nkarhi hinkwawo ka xikombiso eka ntshikelelo wa mahiselo yale hansi; naswona ku hambana exikarhi ka TR10 na TR70 ku tirhisiwa ku pima crystallization ya xikombiso (loko ku hambana ku ri kukulu, ku va na mboyamelo wo crystallize).
6 . Ku Pfuxetiwa ka Ntshikelelo wa Ntshikelelo wa Mahiselo ya le Hansi (CSR) .
Xikambelo xa CSR xinga tirhisiwa ku endla vuprofeta mayelana na matirhelo na vutomi bya switirhisiwa swo pfalela. Loko nkatsakanyo wa elastomeric wu nyikiwa ku onhaka loku nga cincekiki, ku endliwa matimba lama hlanganeke, naswona vuswikoti bya nchumu lowu byo hlayisa matimba lawa endzeni ka ndhawu yo karhi ya mbango byi pima vuswikoti bya wona byo pfalela. Havumbirhi maendlelo ya physical na ti khemikhali ya hoxa xandla eka ku olova ka ntshikelelo, kuya hi nkarhi na mahiselo, nchumu wun’we wuta lawula, ku ntshunxeka ka miri ku voniwa eka mahiselo yale hansi, hiku hatlisa endzhaku ka ntshikelelo lowu nyikiweke, leswi yisaka eka ku lulamisiwa nakambe ka ti chain xikan’we naku cinca eka swiphemu swa rubber-filler na filler-filler, naswona ku ntshunxeka ka sisiteme yo susa ntshikelelo swa tlheriseriwa endzhaku. Eka mahiselo yale henhla, xivumbeko xa ti khemikhali xi veka mpimo wa ku ntshunxeka, loko maendlelo ya physical se yari matsongo naswona ku olova ka ti khemikhali kunga hundzuki, leswi yisaka eka ku tshoveka ka chain xikan’we na cross-linking reactions. Ku rhendzeleka ka mahiselo kumbe ku tlakuka ka mahiselo hi xitshuketa swinga va na mbuyelo eka ku olovisiwa ka ntshikelelo eka ti elastomers. Hi nkarhi wa xikambelo xa CSR, xikombiso xa xikambelo xa vekiwa
Hi nkarhi wa ku kamberiwa ka CSR, ku ntshunxeka ka ntshikelelo ku engeteriwa loko xikombiso xa xikambelo xi endliwa mahiselo yale henhla. Loko ku ntshunxeka ka ntshikilelo ku humelela eku sunguleni ka xikambelo, nhlayo ya ku ntshunxeka loku engetelekeke yi engeteleka ku sungula naswona yi na ntikelo lowukulu hi nkarhi wa xirhendzevutani xo sungula. Eka xiphemu lexikulu xa xikambelo xa tensile kuva ku humelerisa tisampulu ta gasket (19mm outer diameter, inner diameter ya 15mm), na elastic fixture yita tshikileriwa kuya eka specimen kuya eka room temperature thickness ya yona ya 25%, naswona eka 25 °C kuya eka environmental test chamber, mahiselo eka 25 °C kuva ya hlayisa 24h, kutani ya hunguteka kuya eka -20 °C, ya hlayisiwa kuringana 24h, ku landzela mahiselo lawa ya landzelaka exikarhi ka -20 ~ 110 °C cycle ya 24h, nkarhi hinkwawo wa xikambelo eka mahiselo ya xikambelo, mahiselo ya xikambelo, ku tiyimisela ka matimba lama yaka emahlweni. Ku pimiwa ka matimba ku endliwa hiku ya emahlweni eka nkarhi hinkwawo wa xikambelo eka mahiselo ya xikambelo.
7. Vuyelo bya Nhlayo ya Ethylene
7.1 Nhlayo ya ethylene yina nkucetelo lowukulu eka matirhelo ya mahiselo yale hansi ya ti polymers ta EPDM. Ti polymers letingana nhlayo ya Ethylene kusuka eka 48% kuya eka 72% ti kamberiwile ehansi ka ti formulations ta khwalithi yale henhla to sealing. Hinkwaswo swi kongomisa eka ku hunguta ku hambana ka mooney viscosity hiku nghenisa ENB eka ti polymers leti tohambana hambana.
Rhaba ya EPDM ayi na xivumbeko loko ethylene/propylene ratio yi ringana naswona ku hangalasiwa ka ti monomers timbirhi eka polymer chain swinga random. EPDM leyingana 48% na 54% wa ethylene ayi crystallize eka kumbe ehenhla ka mahiselo ya kamara. Loko nhlayo ya ethylene yifika eka 65%, ntlhandlamano wa ethylene wusungula ku tlakuka hi nhlayo na ku leha naswona swinga endla ti crystals, leti voniwaka eka tinhlohlorhi ta crystallization eka ti curves ta DSC kwalomu ka 40°C. Loko tinhlohlorhi ta DSC tiri tikulu, ti crystals leti vumbekaka tiva tikulu.
7.2 Ku engetela eka mbuyelo wa nhlayo ya ethylene eka swivumbeko swa mahiselo yale hansi leswi ku buriweke ha swona endzhaku, vukulu bya crystallite byi khumba ku olova ka ku hlanganisiwa na ku lulamisiwa ka swihlanganisi leswingana ti crystals. Loko vukulu bya crystallite, ntirho wotala wo hisa naku tsemeta wu laveka eka xiteji xo hlanganisa leswaku kuta hlanganisiwa hiku hetiseka polymer na swiphemu swin’wana. Matimba ya rhaba yoka yanga swekiwanga ya ti compounds ta EPDM ya tlakuka loko ethylene yi tlakuka. Eka ti formulations to pfalela laha mbuyelo wa ethylene a wu pimiwa, ku tlakuka ka ethylene kusuka eka 50% kuya eka 68% swiendle leswaku kuva na ku tlakuka ka kwalomu ka mune eka matimba ya rhaba. Ku tiya ka mahiselo ya kamara switlhela swikula loko ethylene yi tlakuka. Ku tiya ka Shore A ka amorphous polymer adhesive i 63°, kasi ku tiya ka Shore A ka polymer leyingana nhlayo yale henhla ya ethylene i 79°. Leswi swivangiwa hiku tlakuka ka ntlhandlamano wa ethylene, ku tlakuka ka crystallization eka adhesive, na ku tlakuka loku fambelanaka na ti thermoplastic polymers.
7.3 Loko ku tiya ku pimiwa eka mahiselo yale hansi, ku hambana na ti polymers letingana nhlayo yale henhla ya ethylene, ti polymers ta amorphous ti kombisa ku cinca kutsongo eka ku tiya, kasi ku cinca ka ku tiya ka nhlayo yale henhla ya ethylene aswi kombisi xivumbeko xa linear naswona ku tiya ku tshama kuri e henhla eka mahiselo yale henhla, leswaku ti polymers letingana nhlayo yale henhla ya ethylene ti ya emahlweni tiva na ku tiya ka le henhla eka mahiselo yale hansi.
7.4 Seti ya ntshikelelo yi titshege ngopfu hi mahiselo ya xikambelo. Loko ku kamberiwa eka 175°C, akuri na ku hambana eka compression set exikarhi ka yin’wana na yin’wana ya ti polymers (set yikuceteriwa hi dizayini ya compound xikan’we naku hlawuriwa ka vulcanization system). Endzhaku ko n’oka ka ti crystals ta ethylene, polymer yikombisa xivumbeko xa amorphous, naswona leswaku kuta kamberiwa mbuyelo wa ethylene content, swikambelo swiendliwile eka 23°C. Ti polymers letingana nhlayo yale henhla ya ethylene swile rivaleni leswaku tina deformation yale henhla ya nkarhi hinkwawo (ku tlula kambirhi), naswona mbuyelo wa nhlayo ya ethylene wukulu swinene loko wukamberiwa eka -20°C na -40°C. Ti polymers letingana kutlula 60% wa ethylene tina deformation yale henhla ya nkarhi hinkwawo (>80%); eka -40°C, i ti polymers letinga amorphous hiku hetiseka ntsena letingana deformation yale hansi ya nkarhi hinkwawo (17%).
7.5 Vuyelo bya Nhlayo ya Ethylene eka ku nonoka ka mahiselo yale hansi kusuka eka swikambelo swa Gehman. Loko ku nyikiwa mahiselo, loko khoneni yiri e henhla, ku tlakuka ka ku tiya (kumbe ku tlakuka ka modulus swiva ehansi). Eka mahiselo yale hansi, modulus ya stiffness yi tlakuka swinene loko ku tlakuka nhlayo ya ethylene. Eka ti amorphous polymers, T2 i -47°C, kasi polymer leyingana ethylene yale henhla yina T2 ya -16°C ntsena.
7.6TR Ku pima ku vuyiseriwa ka shrinkage ka swikombiso endzhaku ka extension freezing, nhlayo ya ethylene yina mbuyelo lowukulu eka ndlela ya xikambelo, leyi nakambe yi fanaka na xikambelo xa Gehman.
Leswi swi fana ni xikambelo xa Gehman. Ku hunguteka (%) ka ti polymers to hambana hambana kuya hi ntirho wa mahiselo, laha ti amorphous polymers tingana ku vuyiseriwa ka shrinkage yale henhla swinene eka mahiselo yale hansi; hambiswiritano, tani hileswi swinga languteriwaka, ku vuyelela ka nyanya loko nhlayo ya ethylene yi tlakuka eka mahiselo lawa ya nyikiweke.
ku hola ka nyanya. Nhlayo ya TR10 yihambana kusuka eka -53°C eka ti amorphous polymers kuya eka -28°C eka ti polymers letingana ethylene yale henhla.
7.7 Xirhendzevutani xa ku olovisa ntshikelelo wa ntshikelelo (CSR).
Ndzendzeleko. Tshikelela ti compounds, ti pfumelela kuva ti wisa eka 25°C kuringana 24 h, kutani u ti veka eka xirhendzevutani xa mahiselo kusuka eka -20°C kuya eka 110°C hiku hambana hambana kuringana 24 h. Loko yi tshikileriwa rosungula, endzhaku ka nkarhi wa equilibration, crystalline polymer E yina ku lahlekeriwa lokukulu ka ntshikelelo kutlula amorphous polymer, naswona loko yi hungutiwa kuya eka -20°C matimba yo pfalela ya ti polymers timbirhi ya hunguteka, kasi amorphous polymer A yina ku khomiwa lokukulu ka ntshikelelo (F/F0 yale henhla). Ku hisa compound kuya eka 110°C swivuyise matimba ya yona yo pfalela, naswona loko yi vuyiseriwa ehansi kuya eka -20°C, matimba yo pfalela lawa yanga sala ya crystalline polymer ayari ehansi ka 20% wa nkoka wa yona, leswi hi xitalo switekiwaka swiri ehansi swinene eka switirhisiwa swotala, laha amorphous polymer yi hlayisaka kutlula 50% wa matimba ya yona yo pfalela, naswona amorphous polymer nakambe yiva na ku vuyelela lokukulu kutlula polymer ya kristala. Xirhendzevutana lexi landzeleke xi humese makumu lama fanaka. Swi le rivaleni leswaku ti amorphous polymers ti tlakukile eka switirhisiwa swo pfalela laha ku lavekaka matirhelo ya mahiselo yale henhla na yale hansi.
8. Vuyelo bya Nhlayo ya Diolefin
Ku nyika unsaturated point leyi lavekaka eka vulcanization, ti non-conjugated diolefins tofana na ENB, HX na DCPD ti cheriwa eka ti ethylene propylene polymers. Double bond yin’we yi endla reaction eka polymer matrix, kasi ya vumbirhi yitirha tani hi complement eka polymerized molecular chain naswona yinyika vulcanization point eka sulphur yellow vulcanization. Vuyelo bya ENB byi kamberiwile eka ti windshield (rain) bar profiles. Ti polymers letingana 2%, 6% na 8% ENB ti pimanyisiwile.Ku engeteriwa ka ENB swive na mbuyelo lowukulu eka swihlawulekisi swa vulcanization na crosslink density. Modulus yi tlakukile kasi elongation yi hungutekile swinene. Ku tiya swi engetelekile naswona compression set yi antswisiwile hi nkarhi wa ku tlakuka ka mahiselo. Loko nhlayo ya ENB yikula, nkarhi wa charring wuva wuntsongo.
ENB i nchumu lowu nga riki na xivumbeko, naswona loko wu cheriwa eka nkolo wa polymer, wu kavanyeta ku crystallization ka xiphemu xa ethylene xa polymer, leswaku ti polymers letingana nhlayo ya ethylene leyi fanaka tinga kumiwa, naswona nhlayo yale henhla ya ENB yi antswisa swivumbeko swa mahiselo yale hansi. Eka mahiselo ya kamara, nhlayo yale henhla ya ENB yi antswisa nyana compression set hikokwalaho ka ku antswisiwa ka crosslink density. Hambiswiritano, eka mahiselo yale hansi, compression set ya ti polymers letingana ENB yale henhla yi antswa swinene kutlula ya ti polymers letingana 2% wa ENB. Vuyelo bya nhlayo ya ENB eka mahiselo ya brittleness, ku tlhelela endzhaku ka mahiselo, na xikambelo xa Gehman a byi kombisanga ku hambana lokukulu eka mahiselo ya brittleness exikarhi ka ti polymers hiku angarhela, naswona eka xikambelo xa Gehman na xikambelo xa TR, polymer yin’wana na yin’wana yi kombisile ku antswisiwa eka swivumbeko swa mahiselo yale hansi hiku tlakuka ka nhlayo ya ENB.
9. Vuyelo bya mooney Viscosity eka Swihlawulekisi swa Mahiselo yale Hansi
Switiveka kahle leswaku mooney viscosity (molecular mass) yina mbuyelo lowukulu eka mahanyelo ya processing ya ti elastomers. Eka switirhisiwa swa extrusion na molding Eka switirhisiwa swa extrusion na molding, swina nkoka ku hlawula compound leyingana nhlayo leyi faneleke ya Mooney viscosity. Hiku tirhisa xivumbeko lexi fanaka lexi tirhisiweke ku lavisisa mbuyelo wa monomer ya vunharhu, ENB, eka swivumbeko swa mahiselo yale hansi ku kambela Mooney viscosity, ti polymers letingana Mooney viscosities ya 30, 60, na 80 ti pimanyisiwile, naswona Mooney viscosity ya ti compounds yi tlakukile loko Mooney viscosity ya ti polymers leti tirhisiweke yi tlakuka. Matimba ya tensile, modulus, na matimba ya rhaba yoka yanga swekiwanga swi engetelekile loko ku tlakuka ka Mooney viscosity. Vuyelo bya Mooney viscosity eka swivumbeko swa mahiselo yale hansi ya EPDM a byi nga ri bya nkoka. Hambiswiritano, compression permanent deformation eka mahiselo ya kamara, -20°C na -40°C yi tlakuka loko ku engeteleka ka molecular mass. Hambiswiritano, compression leyi vekiweke eka mahiselo ya kamara, -20°C na -40°C ayi cincanga ngopfu hiku tlakuka ka molecular mass, laha compression leyi vekiweke eka mahiselo yale henhla (175°C) yikombe ku cinca kun’wana eka mooney viscosities yale henhla ya ti EPDM adhesives.
10. Mahetelelo
Nhlayo ya ethylene na diolefin yina mbuyelo lowukulu eka matirhelo ya ti EPDM elastomers eka switirhisiwa swa mahiselo yale hansi, laha ti polymers letingana nhlayo yale hansi ya ethylene ti tirhaka kahle naswona ti polymers letingana nhlayo yale henhla ya diolefin ti antswisiwa hikokwalaho ka ku kavanyetiwa ka crystallization ya xiphemu xa ethylene xa polymer. Ti polymers ta ethylene yale hansi tifanele kutirhisiwa loko matirhelo ya mahiselo yale hansi yari xipimelo.
