Ho thoeng kepolyurethaneke khutsufatso ea polyurethane, e entsoeng ke karabelo ea polyisocyanates le polyols, 'me e na le lihlopha tse ngata tse pheta-phetoang tsa amino ester (- NH-CO-O -) ka ketane ea limolek'hule.Ka har'a li-resin tse entsoeng ka polyurethane, ntle le sehlopha sa amino ester, ho boetse ho na le lihlopha tse kang urea le biuret.Li-polyols ke tsa limolek'hule tse telele tse nang le lihlopha tsa hydroxyl qetellong, tse bitsoang "likarolo tsa ketane e bonolo", ha polyisocyanate e bitsoa "likarolo tsa ketane e thata".
Har'a li-resin tsa polyurethane tse hlahisoang ke likarolo tse bonolo le tse thata tsa ketane, ke karolo e nyenyane feela ea li-amino acid ester, kahoo ho ka 'na ha se ke ha e-ba ho loketseng ho li bitsa polyurethane.Ka kutloisiso e pharaletseng, polyurethane ke motsoako oa isocyanate.
Mefuta e fapaneng ea li-isocyanate e sebetsana le metsoako ea polyhydroxy ho hlahisa mekhoa e sa tšoaneng ea polyurethane, kahoo e fumana thepa ea polymer e nang le thepa e fapaneng, e kang polasetiki, rabara, liphahlo, likhoele, likhomaretsi, joalo-joalo.
Rabara ea polyurethane ke ea mofuta o khethehileng oa rabara, e entsoeng ka polyether kapa polyester e nang le isocyanate.Ho na le mefuta e mengata ka lebaka la mefuta e fapaneng ea lisebelisoa tse tala, maemo a karabelo le mekhoa ea ho kopanya.Ho latela pono ea sebopeho sa lik'hemik'hale, ho na le mefuta ea polyester le polyether, 'me ho latela mokhoa oa ho sebetsa, ho na le mefuta e meraro: mofuta oa ho kopanya, mofuta oa ho lahla, le mofuta oa thermoplastic.
Synthetic polyurethane rabara ka kakaretso e entsoe ka polyester e melang kapa polyether e nang le diisocyanate ho etsa prepolymer e tlase ea boima ba molek'hule, e ntan'o ba tlas'a karabelo ea ketane ho hlahisa polymer e phahameng ea boima ba limolek'hule.Ka mor'a moo, li-crosslinking agents tse loketseng lia eketsoa le ho futhumatsoa ho e phekola, 'me e fetoha rabara e chesitsoeng.Mokhoa ona o bitsoa prepolymerization kapa mokhoa oa mehato e 'meli.
Hape hoa khoneha ho sebelisa mokhoa oa mohato o le mong - ho kopanya ka ho toba polyester ea mohala kapa polyether e nang le diisocyanate, li-chain extenders, le li-crosslinking agents ho qala karabelo le ho hlahisa rabara ea polyurethane.
Karolo ea A ka har'a limolek'hule tsa TPU e etsa hore liketane tsa macromolecular li be bonolo ho potoloha, li fa rabara ea polyurethane e nang le elasticity e ntle, e fokotsang ntlha ea ho nolofatsa le ntlha ea phetoho ea bobeli ea polymer, le ho fokotsa ho thatafala ha eona le matla a mochine.Karolo ea B e tla tlama ho potoloha ha liketane tsa macromolecular, ho etsa hore ntlha ea ho nolofatsa le ntlha ea phetoho ea bobeli ea polymer e eketsehe, e leng se etsang hore ho be le keketseho ea boima le matla a mochine, le ho fokotseha ha elasticity.Ka ho fetola tekanyo ea molar pakeng tsa A le B, li-TPU tse nang le thepa e fapaneng ea mochine li ka hlahisoa.Sebopeho sa li-cross-link tsa TPU ha sea lokela ho nahana feela ka li-cross-link tse ka sehloohong, empa hape le li-cross-link tsa bobeli tse entsoeng ka likamano tsa hydrogen pakeng tsa limolek'hule.Khokahano ea mantlha ea sefapano sa polyurethane e fapane le sebopeho sa vulcanization sa rabara ea hydroxyl.Sehlopha sa eona sa amino ester, sehlopha sa biuret, sehlopha sa urea formate le lihlopha tse ling tse sebetsang li hlophisitsoe ka karolo ea ketane e tsitsitseng le e arohaneng, e hlahisang sebopeho sa marang-rang se tloaelehileng sa rabara, se nang le khanyetso e ntle ea ho roala le lisebelisoa tse ling tse babatsehang.Taba ea bobeli, ka lebaka la boteng ba lihlopha tse ngata tse sebetsang tse momahaneng tse kang urea kapa lihlopha tsa carbamate ka rabara ea polyurethane, li-hydrogen bond tse entsoeng pakeng tsa liketane tsa limolek'hule li na le matla a phahameng, 'me li-crosslinking tsa bobeli tse entsoeng ke li-hydrogen bond le tsona li na le phello e kholo ho thepa. rabara ea polyurethane.Khokahano ea bobeli ea sefapano e thusa rabara ea polyurethane hore e be le litšobotsi tsa li-elastomer tsa thermosetting ka lehlakoreng le leng, 'me ka lehlakoreng le leng, khokahanyo ena ea sefapano ha e hlile ha e hokahane, e etsa hore e be sehokelo se hlakileng.Boemo ba ho kopanya lifapano bo itšetlehile ka mocheso.Ha mocheso o ntse o eketseha, khokahano ena ea sefapano e fokotseha butle-butle ebe e nyamela.Polima e na le mokelikeli o itseng 'me e ka kenngoa ts'ebetsong ea thermoplastic.Ha mocheso o fokotseha, khokahano ena ea sefapano e hlaphoheloa butle-butle ebe e theha hape.Ho eketsoa ha palo e nyane ea li-filler ho eketsa sebaka se pakeng tsa limolek'hule, ho fokolisa bokhoni ba ho theha maqhama a hydrogen pakeng tsa limolek'hule, 'me ho lebisa ho fokotseha ho hoholo ha matla.Lipatlisiso li bontšitse hore tatellano ea botsitso ba lihlopha tse fapaneng tse sebetsang ka rabara ea polyurethane ho tloha holimo ho ea tlaase ke: ester, ether, urea, carbamate, le biuret.Nakong ea ts'ebetso ea botsofali ea rabara ea polyurethane, mohato oa pele ke ho robeha ha maqhama a hokahanyang pakeng tsa biuret le urea, ho lateloa ke ho khaoha ha li-carbamate le urea bond, ke hore, ketane e kholo ea ketane.
01 Ho nolofatsa
Li-elastomers tsa polyurethane, joalo ka lisebelisoa tse ngata tsa polymer, li nolofatsa mocheso o phahameng 'me li fetoha ho tloha boemong bo tsitsitseng ho ea ho boemo ba phallo ea viscous, e leng se bakang ho fokotseha ka potlako ha matla a mochine.Ho ea ka pono ea lik'hemik'hale, mocheso o kokobetsang oa elasticity haholo-holo o itšetlehile ka lintlha tse kang motsoako oa lik'hemik'hale, boima ba limolek'hule tse lekanyelitsoeng le ho teteana ha li-crosslinking.
Ka kakaretso, ho eketsa boima ba molek'hule, ho eketsa ho tiea ha karolo e thata (e kang ho kenya selikalikoe sa benzene ka har'a molek'hule) le likahare tsa karolo e thata, le ho eketsa boima ba li-crosslinking kaofela li molemo bakeng sa ho eketsa mocheso o fokolang.Bakeng sa li-elastomer tsa thermoplastic, sebopeho sa limolek'hule se na le mela, 'me mocheso o bonolo oa elastomer le ona oa eketseha ha boima ba limolek'hule bo eketseha.
Bakeng sa li-elastomer tsa polyurethane tse hokahantsoeng ka sefapano, sekhahla sa khokahano se na le tšusumetso e kholo ho feta boima ba molek'hule.Ka hona, ha ho etsoa li-elastomers, ho eketsa ts'ebetso ea isocyanate kapa polyols ho ka theha marang-rang a tsitsitseng a tsitsitseng a lik'hemik'hale tse kopanyang limolek'hule tse ling, kapa ho sebelisa likarohano tse feteletseng tsa isocyanate ho theha sebopeho se tsitsitseng sa isocyanate 'meleng oa elastic mokhoa o matla oa ho ntlafatsa ho hanyetsa mocheso, ho hanyetsa solvent, le matla a mochine oa elastomer.
Ha PPDI (p-phenyldiisocyanate) e sebelisoa e le thepa e tala, ka lebaka la ho hokahana ka ho toba ha lihlopha tse peli tsa isocyanate le lesale la benzene, karolo e thata e entsoeng e na le selikalikoe se phahameng sa benzene, se ntlafatsang ho tiea ha karolo e thata, kahoo e ntlafatsa. ho hanyetsa mocheso oa elastomer.
Ho ea ka pono ea 'mele, mocheso o bonolo oa li-elastomers o itšetlehile ka tekanyo ea karohano ea microphase.Ho ea ka litlaleho, mocheso o bonolo oa li-elastomers tse sa arohaneng le microphase o tlase haholo, ka mocheso oa ho sebetsa o ka bang 70 ℃, ha li-elastomers tse kenang karohano ea microphase li ka fihla ho 130-150 ℃.Ka hona, ho eketsa tekanyo ea karohano ea microphase ho elastomers ke e 'ngoe ea mekhoa e sebetsang ea ho ntlafatsa ho hanyetsa mocheso oa bona.
Tekanyo ea karohano ea li-microphase ea li-elastomer e ka ntlafatsoa ka ho fetola kabo ea boima ba limolek'hule ea likarolo tsa ketane le litaba tsa likarolo tse thata tsa ketane, ka hona, li matlafatsa ho hanyetsa mocheso.Bafuputsi ba bangata ba lumela hore lebaka la ho arohana ha microphase ka polyurethane ke ho se lumellane ha thermodynamic pakeng tsa likarolo tse bonolo le tse thata.Mofuta oa li-chain extender, karolo e thata le litaba tsa eona, mofuta oa karolo e bonolo, le bonding ea hydrogen kaofela li na le tšusumetso e kholo ho eona.
Ha ho bapisoa le diol chain extenders, diamine chain extenders tse kang MOCA (3,3-dichloro-4,4-diaminodiphenylmethane) le DCB (3,3-dichloro-biphenylenediamine) li theha lihlopha tse ngata tsa polar amino ester ka elastomers, le li-hydrogen bond tse ngata li ka ho thehoa pakeng tsa likarolo tse thata, ho eketsa tšebelisano pakeng tsa likarolo tse thata le ho ntlafatsa tekanyo ea ho arohana ha microphase ho elastomers;Symmetric chain extensions tse kang p, p-dihydroquinone, le hydroquinone li molemo bakeng sa ho tloaeleha le ho paka ka thata ha likarolo tse thata, kahoo li ntlafatsa karohano ea microphase ea lihlahisoa.
Likarolo tsa li-amino ester tse entsoeng ke li-aliphatic isocyanate li lumellana hantle le likarolo tse bonolo, e leng se etsang hore ho be le likarolo tse thata tse qhibilihang likarolong tse bonolo, ho fokotsa tekanyo ea karohano ea microphase.Likarolo tsa amino ester tse entsoeng ke li-isocyanate tse nkhang hamonate li na le kamano e fokolang le likarolo tse bonolo, ha tekanyo ea karohano ea microphase e phahame.Polyolefin polyurethane e na le hoo e batlang e le e feletseng ea karohano ea microphase ka lebaka la hore karolo e bonolo ha e thehe li-hydrogen bond le li-hydrogen bond li ka etsahala feela karolong e thata.
Phello ea hydrogen bonding sebakeng se nolofatsang sa elastomer le eona e bohlokoa.Le hoja li-polyethers le carbonyls karolong e bonolo li ka etsa palo e kholo ea likamano tsa hydrogen le NH karolong e thata, e boetse e eketsa mocheso o bonolo oa li-elastomers.Ho netefalitsoe hore li-hydrogen bond li ntse li boloka 40% ho 200 ℃.
02 Ho senyeha ha mocheso
Lihlopha tsa amino ester li na le ho bola ho latelang ka mocheso o phahameng:
- RNHCOOR – RNC0 HO-R
- RNHCOOR – RNH2 CO2 ene
- RNHCOOR – RNHR CO2 ene
Ho na le mefuta e meraro ea mantlha ea ho bola ha mocheso oa thepa e thehiloeng ho polyurethane:
① Ho theha li-isocyanate tsa mantlha le polyols;
② α— Tlamahano ea oksijene motheong oa CH2 e ea robeha ebe e kopana le bond e le 'ngoe ea haedrojene ho CH2 ea bobeli ho etsa li-amino acid le alkenes.Li-amino acid li senyeha ho ba amine e le 'ngoe ea mantlha le carbon dioxide:
③ Foromo ea 1 ea bobeli ea amine le carbon dioxide.
Ho senyeha ha mocheso oa sebopeho sa carbamate:
Aryl NHCO Aryl, ~ 120 ℃;
N-alkyl-NHCO-aryl, ~ 180 ℃;
Aryl NHCO n-alkyl, ~ 200 ℃;
N-alkyl-NHCO-n-alkyl, ~ 250 ℃.
Ho tsitsa ha mocheso oa li-amino acid ester ho amana le mefuta ea lisebelisoa tsa ho qala tse kang isocyanates le polyols.Li-aliphatic isocyanate li phahame ho feta li-isocyanate tse nkhang hamonate, athe lino tse mafura li phahame ho feta lino tse nkhang hamonate.Leha ho le joalo, lingoliloeng li tlaleha hore mocheso oa mocheso oa ho bola oa aliphatic amino acid ester o pakeng tsa 160-180 ℃, le oa li-ester tse nkhang hamonate tsa amino acid o pakeng tsa 180-200 ℃, tse sa lumellaneng le lintlha tse ka holimo.Lebaka le ka 'na la amana le mokhoa oa ho hlahloba.
Ha e le hantle, aliphatic CHDI (1,4-cyclohexane diisocyanate) le HDI (hexamethylene diisocyanate) li na le mocheso o betere ho feta o sebelisoang hangata o nkhang hamonate oa MDI le TDI.Haholo-holo trans CHDI e nang le sebopeho sa symmetrical e 'nile ea nkoa e le isocyanate e thibelang mocheso ka ho fetisisa.Li-elastomer tsa polyurethane tse lokiselitsoeng ho tsoa ho eona li na le ts'ebetso e ntle, khanyetso e ntle ea hydrolysis, mocheso o phahameng o nolofatsang, mocheso o tlase oa phetoho ea likhalase, mocheso o tlase oa mocheso, le khanyetso e phahameng ea UV.
Ntle le sehlopha sa amino ester, polyurethane elastomers e boetse e na le lihlopha tse ling tse sebetsang tse kang urea formate, biuret, urea, joalo-joalo. Lihlopha tsena li ka senyeha ha mocheso o le mocheso o phahameng:
NHCONCOO - (aliphatic urea formate), 85-105 ℃;
- NHCONCOO - (monko o monate oa urea formate), ka mocheso oa mocheso oa 1-120 ℃;
- NHCONCONH - (aliphatic biuret), ka mocheso ho tloha ho 10 ° C ho ea ho 110 ° C;
NHCONCONH - (aromatic biuret), 115-125 ℃;
NHCONH - (aliphatic urea), 140-180 ℃;
- NHCONH - (urea e nkhang hamonate), 160-200 ℃;
selikalikoe sa isocyanurate> 270 ℃.
Thempereichara ea ho bola ea biuret le urea e thehiloeng ho formate e tlase haholo ho feta ea aminoformate le urea, athe isocyanurate e na le botsitso bo botle ba mocheso.Tlhahisong ea li-elastomers, li-isocyanate tse feteletseng li ka sebetsana le sebopeho sa aminoformate le urea ho theha meaho e hokahaneng ea urea le biuret.Le hoja li ka ntlafatsa thepa ea mechine ea li-elastomers, ha li tsitse ho chesa haholo.
Ho fokotsa lihlopha tse sa tsitsang tsa mocheso tse kang biuret le urea formate ho li-elastomers, hoa hlokahala ho nahana ka karo-karolelano ea thepa e tala le ts'ebetso ea tlhahiso.Ho lokela ho sebelisoa litekanyo tse feteletseng tsa isocyanate, 'me mekhoa e meng e lokela ho sebelisoa ka hohle kamoo ho ka khonehang ho qala pele ho etsa mehele ea isocyanate ka har'a thepa e tala (haholo-holo li-isocyanate, polyols, le li-chain extender), ebe joale li kenya ka har'a elastomer ho latela mekhoa e tloaelehileng.Ona e se e le mokhoa o sebelisoang ka ho fetesisa oa ho hlahisa li-elastomer tsa polyurethane tse hanyetsanang le malakabe.
03 Hydrolysis le thermal oxidation
Li-elastomer tsa polyurethane li na le tšekamelo ea ho bola ha mocheso likarolong tsa tsona tse thata le liphetoho tsa lik'hemik'hale tse lumellanang le likarolo tsa tsona tse bonolo mochesong o phahameng.Li-elastomer tsa polyester ha li na metsi hantle 'me li na le tšekamelo e matla ea ho hydrolyze ka mocheso o phahameng.Bophelo ba tšebeletso ea polyester/TDI/diamine bo ka fihla likhoeling tse 4-5 ho 50 ℃, libeke tse peli feela ho 70 ℃, le matsatsi a seng makae feela ka holimo ho 100 ℃.Li-bond tsa Ester li ka bola ho ba li-acids le lino tse tahang ha li pepesetsoa metsi a chesang le mouoane, 'me lihlopha tsa urea le amino ester ka elastomer le tsona li ka ba le karabelo ea hydrolysis:
RCOOR H20- → RCOOH HOR
Ester joala
RNHCONHR e le 'ngoe H20- → RXHCOOH H2NR -
Ureamide
E 'ngoe RNHCOOR-H20- → RNCOOH HOR -
Amino formate ester Amino formate alcohol
Li-elastomer tse thehiloeng ho polyether li na le botsitso bo fokolang ba mocheso oa oxidation, le li-elastomer tse thehiloeng ka ether α- Hydrojene e holim'a athomo ea carbon e oxidized habonolo, e etsa hydrogen peroxide.Ka mor'a ho senyeha ho eketsehileng le ho phunyeha, e hlahisa li-radicals tsa oxide le hydroxyl radicals, tse qetellang li senyeha ho ba lifomate kapa aldehydes.
Li-polyester tse fapaneng ha li na phello e fokolang ho hanyetsa mocheso oa li-elastomers, ha li-polyester tse fapaneng li na le tšusumetso e itseng.Ha ho bapisoa le TDI-MOCA-PTMEG, TDI-MOCA-PTMEG e na le sekhahla sa ho boloka matla sa 44% le 60% ka ho latellana ha se le lilemo li 121 ℃ ka matsatsi a 7, 'me ea morao-rao e le betere ho feta ea pele.Lebaka e ka 'na ea e-ba hore limolek'hule tsa PPG li na le liketane tse nang le makala, tse sa lumellaneng le tlhophiso e tloaelehileng ea limolek'hule tsa elastic le ho fokotsa ho hanyetsa mocheso oa' mele oa elastic.Taelo ea botsitso ba mocheso oa li-polyethers ke: PTMEG>PEG>PPG.
Lihlopha tse ling tse sebetsang ka har'a polyurethane elastomers, joalo ka urea le carbamate, le tsona li fumana karabelo ea oxidation le hydrolysis.Leha ho le joalo, sehlopha sa ether ke sona se nang le oxidized habonolo, ha sehlopha sa ester ke sona se nang le hydrolyzed habonolo.Taelo ea ho hanyetsa ha bona ea antioxidant le hydrolysis ke:
Mosebetsi oa Antioxidant: esters>urea>carbamate>ether;
Hydrolysis resistance: ester
Ho ntlafatsa khanyetso ea oxidation ea polyether polyurethane le hydrolysis resistance ea polyester polyurethane, li-additives li boetse li eketsoa, joalo ka ho eketsa 1% phenolic antioxidant Irganox1010 ho PTMEG polyether elastomer.Matla a matla a elastomer ena a ka eketsoa ka makhetlo a 3-5 ha a bapisoa le ntle le li-antioxidants (liphetho tsa liteko ka mor'a botsofali ho 1500C bakeng sa lihora tse 168).Empa ha se antioxidant e 'ngoe le e' ngoe e nang le phello ho polyurethane elastomers, feela phenolic 1rganox 1010 le TopanOl051 (phenolic antioxidant, thibela amine light stabilizer, benzotriazole complex) e na le liphello tse kholo, 'me ea pele ke eona e molemo ka ho fetisisa, mohlomong hobane phenolic antioxidants e lumellana hantle le elastomers.Leha ho le joalo, ka lebaka la karolo ea bohlokoa ea lihlopha tsa phenolic hydroxyl mochineng oa botsitso oa phenolic antioxidants, e le ho qoba ho itšoara le "ho hlōleha" ha sehlopha sena sa phenolic hydroxyl se nang le lihlopha tsa isocyanate tsamaisong, karo-karolelano ea isocyanate ho polyols ha ea lokela ho ba teng. e kholo haholo, 'me li-antioxidants li tlameha ho eketsoa ho li-prepolymers le li-extensions tsa ketane.Haeba e eketsoa nakong ea tlhahiso ea li-prepolymers, e tla ama haholo phello ea botsitso.
Li-additives tse sebelisetsoang ho thibela hydrolysis ea polyester polyurethane elastomers haholo-holo ke metsoako ea carbodiimide, e sebetsanang le carboxylic acid e hlahisoang ke ester hydrolysis ka limolek'hule tsa polyurethane elastomer ho hlahisa lintho tse tsoang ho acyl urea, ho thibela hydrolysis e eketsehileng.Ho eketsoa ha carbodiimide ka karolo ea boima ba 2% ho isa ho 5% ho ka eketsa botsitso ba metsi a polyurethane ka makhetlo a 2-4.Ho phaella moo, tert butyl catechol, hexamethylenetetramine, azodicarbonamide, joalo-joalo le tsona li na le liphello tse itseng tsa anti hydrolysis.
04 Litšobotsi tsa mantlha tsa ts'ebetso
Li-elastomer tsa polyurethane ke li-copolymers tse ngata tse nang le li-block block, tse nang le liketane tsa limolek'hule tse entsoeng ka likarolo tse tenyetsehang tse nang le mocheso oa likhalase o tlase ho feta mocheso oa kamore le likarolo tse thata tse nang le mocheso oa likhalase o phahameng ho feta mocheso oa kamore.Har'a tsona, li-poligomeric polyols li etsa likarolo tse tenyetsehang, ha li-disocyanate le li-extensions tse nyane tsa molek'hule li theha likarolo tse thata.Sebopeho se kentsoeng sa likarolo tse tenyetsehang le tse thata tsa ketane li etsa qeto ea ts'ebetso ea tsona e ikhethang:
(1) Mefuta e thata ea rabara e tloaelehileng hangata e pakeng tsa Shaoer A20-A90, athe mefuta e thata ea polasetiki e mabapi le Shaoer A95 Shaoer D100.Li-elastomer tsa polyurethane li ka fihla tlase ho Shaoer A10 le holimo ho Shaoer D85, ntle le tlhoko ea thuso ea ho tlatsa;
(2) Matla a phahameng le elasticity li ntse li ka bolokoa ka har'a mefuta e mengata ea boima;
(3) Khanyetso e ntle ea ho apara, makhetlo a 2-10 a rabara ea tlhaho;
(4) Ho hanyetsa metsi, oli le lik'hemik'hale ka tsela e babatsehang;
(5) Ho hanyetsa matla a phahameng, ho hanyetsa mokhathala, le ho hanyetsa ho sisinyeha, ho loketse bakeng sa likopo tse phahameng tsa maqhubu;
(6) Khanyetso e ntle ea mocheso o tlase, e nang le brittleness ea mocheso o tlase -30 ℃ kapa -70 ℃;
(7) E na le ts'ebetso e babatsehang ea ho kenya letsoho, 'me ka lebaka la mocheso o tlaase oa mocheso, o na le phello e ntle ea ho pata ha e bapisoa le rabara le polasetiki;
(8) Biocompatibility e ntle le thepa ea anticoagulant;
(9) Motlakase o motle haholo, ho hanyetsa hlobo, le botsitso ba UV.
Li-elastomer tsa polyurethane li ka etsoa ho sebelisoa lits'ebetso tse ts'oanang le rabara e tloaelehileng, joalo ka polasetiki, ho kopanya le vulcanization.Li ka boela tsa bōptjoa ka mokhoa oa rabara ea metsi ka ho tšela, ho bopa ka centrifugal, kapa ho fafatsa.Li ka boela tsa etsoa lisebelisoa tsa granular 'me tsa etsoa ka ente, extrusion, rolling, blowing, le mekhoa e meng.Ka tsela ena, ha e ntlafatse ts'ebetso ea mosebetsi feela, empa e boetse e ntlafatsa ho nepahala le ponahalo ea sehlahisoa.
Nako ea poso: Dec-05-2023