Inqubekela phambili Yocwaningo Nge-Non-Isocyanate Polyurethanes
Kusukela kwethulwa ngo-1937, izinto ze-polyurethane (PU) ziye zasetshenziswa kabanzi emikhakheni eyahlukene okuhlanganisa ezokuthutha, ezokwakha, amakhemikhali kaphethroli, izindwangu, ubunjiniyela bemishini nogesi, izindiza, ezempilo, kanye nezolimo. Lezi zinto zisetshenziswa ngezindlela ezifana nepulasitiki ye-foam, imicu, ama-elastomer, izinto zokuvimbela amanzi, isikhumba sokwenziwa, izembozo, izinamathiselo, izinto zokugandaya kanye nezinto zezokwelapha. I-PU yendabuko yenziwa ngokuyinhloko kusuka kuma-isocyanate amabili noma ngaphezulu kanye nama-polyol e-macromolecular kanye ne-extenders encane yama-molecule chain. Kodwa-ke, ubuthi obungokwemvelo bama-isocyanate bubeka izingozi ezinkulu empilweni yabantu kanye nemvelo; ngaphezu kwalokho ngokuvamile zivela ku-phosgene—isandulela esinobuthi obukhulu—kanye nezinto zokusetshenziswa ze-amine ezifanayo.
Ngenxa yokuphishekela kwemboni yamakhemikhali yanamuhla imikhuba yokuthuthukisa okuluhlaza nokusimeme, abacwaningi bagxila kakhulu ekushintsheni ama-isocyanate ngezinsiza ezinobungani nemvelo ngenkathi behlola imizila emisha yokwenziwa kwama-polyurethane angewona ama-isocyanate (i-NIPU). Leli phepha lethula izindlela zokulungiselela i-NIPU ngenkathi libuyekeza intuthuko ezinhlotsheni ezahlukene zama-NIPU futhi lixoxa ngamathuba azo esikhathi esizayo ukuze linikeze inkomba yocwaningo olwengeziwe.
1 Ukwenziwa kwe-Non-Isocyanate Polyurethanes
Ukwenziwa kokuqala kwamakhemikhali e-carbamate anesisindo esiphansi kusetshenziswa ama-carbonate e-monocyclic ahlanganiswe nama-diamine e-aliphatic kwenzeka kwamanye amazwe ngawo-1950—okuphawula isikhathi esibalulekile sokwenziwa kwe-polyurethane okungeyona i-isocyanate. Njengamanje kunezindlela ezimbili eziyinhloko zokukhiqiza i-NIPU: Eyokuqala ihilela ukusabela kokwengeza okuhamba kancane phakathi kwama-carbonate e-cyclic e-binary kanye nama-amine e-binary; eyesibili ihilela ukusabela kwe-polycondensation okubandakanya ama-diurethane intermediates kanye nama-diols alula ukushintshana kwesakhiwo ngaphakathi kwama-carbamates. Ama-Diamarboxylate intermediates angatholakala ngezindlela ze-cyclic carbonate noma ze-dimethyl carbonate (DMC); ngokuyisisekelo zonke izindlela zisabela ngamaqembu e-carbonic acid akhiqiza ukusebenza kwe-carbamate.
Izigaba ezilandelayo zichaza izindlela ezintathu ezihlukene zokwenza i-polyurethane ngaphandle kokusebenzisa i-isocyanate.
1.1 Umzila We-Binary Cyclic Carbonate
I-NIPU ingakhiwa ngokungezwa okuhamba kancane okubandakanya i-binary cyclic carbonate ehlanganiswe ne-binary amine njengoba kuboniswe kuMfanekiso 1.
Ngenxa yamaqembu amaningi e-hydroxyl akhona ngaphakathi kwamayunithi aphindaphindayo ekwakhekeni kwayo okuyinhloko kweketanga le ndlela ngokuvamile iveza lokho okubizwa ngokuthi i-polyβ-hydroxyl polyurethane (PHU). ULeitsch et al., bathuthukise uchungechunge lwama-PHU e-polyether asebenzisa ama-polyether aqediwe yi-cyclic carbonate kanye nama-amine e-binary kanye nama-molecule amancane atholakala kuma-carbonate e-binary cyclic—beqhathanisa lokhu nezindlela zendabuko ezisetshenziselwa ukulungiselela ama-PU e-polyether. Okutholakele kwabo kubonise ukuthi amaqembu e-hydroxyl ngaphakathi kwama-PHU akha kalula izibopho ze-hydrogen nama-athomu e-nitrogen/oxygen atholakala ngaphakathi kwezingxenye ezithambile/eziqinile; ukuhlukahluka phakathi kwezingxenye ezithambile nakho kuthinta ukuziphatha kokubopha kwe-hydrogen kanye namazinga okuhlukanisa i-microphase kamuva athinta izici zokusebenza zizonke.
Ngokuvamile kwenziwa ngaphansi kwamazinga okushisa angaphezu kuka-100 °C, le ndlela ayikhiqizi imikhiqizo engaphansi ngesikhathi sezinqubo zokusabela okwenza ingabi nandaba nomswakama ngenkathi ikhiqiza imikhiqizo ezinzile ngaphandle kwezinkinga zokuguquguquka kodwa idinga izinyibilikisi eziphilayo ezibonakala nge-polarity enamandla njenge-dimethyl sulfoxide (DMSO), i-N, i-N-dimethylformamide (DMF), njll. Ngaphezu kwalokho, izikhathi zokusabela ezengeziwe ezisukela noma yikuphi phakathi kosuku olulodwa kuya ezinsukwini ezinhlanu zivame ukukhiqiza isisindo esiphansi sama-molecule esivame ukwehla ngaphansi kwemingcele ezungeze i-30k g/mol okwenza ukukhiqizwa okukhulu kube nzima ngenxa yokuthi izindleko eziphakeme ezihambisana nakho zihambisana namandla anganele aboniswa yi-PHU ephumela naphezu kwezicelo ezithembisayo ezihlanganisa ukudambisa izizinda zezinto zokwakha imemori yesakhiwo ukwakheka kwe-adhesive izixazululo zokumboza amagwebu njll.
1.2Umzila we-Monocylic Carbonate
I-monocylic carbonate isabela ngqo ne-diamine ephumela ku-dicarbamate enamaqembu okuphela kwe-hydroxyl abese edlula ekusebenzelaneni okukhethekile kwe-transesterification/polycondensation kanye nama-diol ekugcineni akhiqiza i-NIPU efana neyamasiko endabuko eboniswe ngokubonakalayo ngeSithombe 2.
Izinhlobo ze-monocylic ezisetshenziswa kakhulu zifaka phakathi i-ethylene kanye ne-propylene carbonated substrates lapho ithimba likaZhao Jingbo eBeijing University Of Chemical Technology lisebenzise ama-diamine ahlukahlukene asabela kuzo ngokumelene nalezo zinto ezijikelezayo ekuqaleni zathola izixhumi ze-dicarbamate ezahlukahlukene ngaphambi kokuqhubekela ezigabeni zokujiya zisebenzisa i-polytetrahydrofuranediol/polyether-diols eziholela ekwakhekeni okuphumelelayo kwemigqa yomkhiqizo ekhombisa izakhiwo ezishisayo/zomshini ezifinyelela phezulu ezindaweni zokuncibilika ezijikeleza ibanga elifinyelela cishe ku-125 ~ 161°C amandla okubamba afinyelela phezulu eduze kwamazinga okunwebeka angama-24MPa asondela ku-1476%. UWang nabanye, ngokufanayo basebenzise inhlanganisela equkethe i-DMC ehlanganiswe ngokulandelana ne-hexamethylenediamine/cyclocarbonated precursors synthesizing hydroxy-terminated derivatives kamuva bafaka ama-dibasic acid asekelwe ku-bio njenge-oxalic/sebacic/acids i-adipic-acid-terephtalics efinyelela imiphumela yokugcina ekhombisa ububanzi obuhlanganisa amandla okudonsa angu-13k~28k g/mol ashintshashintshayo9~17 MPa ende ehlukahluka35%~235%.
Ama-ester e-cyclocarbonic asebenzisana ngempumelelo ngaphandle kokudinga ama-catalyst ngaphansi kwezimo ezijwayelekile agcina izinga lokushisa lifinyelela cishe ku-80°kuya ku-120°C, ama-transesterification alandelayo avame ukusebenzisa izinhlelo ze-catalytic ezisekelwe ku-organotin eziqinisekisa ukuthi ukucubungula okuhle akudluli ku-200°. Ngaphandle kwemizamo nje yokujiya okuqondiswe kokufakwayo kwe-diolic okukwaziyo ukuzilungisa/ukuzisusa kwe-glycolysis okwenza kube lula ukukhiqiza imiphumela efiselekayo kwenza indlela ibe nobungane nemvelo ikakhulukazi ekhiqiza izinsalela ze-methanol/ama-molecule amancane-diolic ngaleyo ndlela iveze ezinye izindlela zezimboni ezisebenzayo eziqhubekayo.
1.3 Umzila we-Dimethyl Carbonate
I-DMC imele enye indlela ephilile/engenabo ubuthi equkethe izingxenye eziningi ezisebenzayo ezifaka phakathi ukwakheka kwe-methyl/methoxy/carbonyl okuthuthukisa amaphrofayili okusabela okuvumela kakhulu ukuzibandakanya kokuqala lapho i-DMC ixhumana ngqo nama-diamine akha ama-intermediaries amancane aqediwe e-methyl-carbamate kulandele ngemuva kwalokho izenzo zokuncibilikisa ezifaka ezinye izakhi ze-small-chain-extender-diolics/larger-polyol eziholela ekuveleni kwezakhiwo ze-polymer ezifunwayo eziboniswe ngokufanele nge-Figure3.
UDeepa nabanye basebenzise amandla ashiwo ngenhla ngokusebenzisa i-catalysis ye-sodium methoxide ehlela ukwakheka okuhlukahlukene okuphakathi kamuva okubandakanya izandiso eziqondiwe ezifinyelela esilinganisweni esilinganayo sezingxenye eziqinile ezifinyelela isisindo sama-molecule esicishe sibe (3 ~ 20)x10^3g/mol amazinga okushisa okuguquka kwengilazi aqala (-30 ~ 120°C). I-Pan Dongdong ikhethe ukubhanqa okunesu okuhlanganisa i-DMC hexamethylene-diaminopolycarbonate-polyalcohols eqaphela imiphumela ephawulekayo ekhombisa amamethrikhi okuqina okushintshashintshayo kwe-10-15MPa ende esondela ku-1000%-1400%. Izinto ezicwaningwayo ezizungeze amathonya ahlukene okwandisa uchungechunge zembule izintandokazi ezivumelanisa kahle ukukhethwa kwe-butanediol/hexanediol lapho ukulingana kwenombolo ye-athomu kugcina ukulingana okukhuthaza ukuthuthukiswa kwekristali okuhleliwe okubonwe kuwo wonke amaketanga. Iqembu likaSarazin lilungiselele izinhlanganisela ezihlanganisa i-lignin/DMC kanye ne-hexahydroxyamine ezibonisa izimfanelo zobuchwepheshe ezanelisayo ngemuva kokucutshungulwa ku-230℃. Ukuhlola okwengeziwe okuhlose ukuthola ama-non-isocyante-polyureas asebenzisa ukubandakanyeka kwe-diazomonomer okulindelwe ukuthi kube nezicelo zopende ezingaba khona ezivela izinzuzo zokuqhathanisa kunezilinganisi ze-vinyl-carbonaceous ezigqamisa ukusebenza kahle kwezindleko/izindlela zokuthola ezibanzi ezitholakalayo. Ukuhlolisisa okufanele mayelana nezindlela ezenziwe ngobuningi ngokuvamile kudinga izindawo zokushisa okuphezulu/i-vacuum ezilahla izidingo ze-solvent ngaleyo ndlela kunciphisa ukugeleza kwemfucuza okukhawulela kakhulu kuphela ukungcola kwe-methanol/molecule encane-diolic okusungula amapharadigm okwenziwa okuluhlaza jikelele.
Izingxenye ezi-2 ezithambile ezahlukene ze-polyurethane engeyona isocyanate
2.1 I-polyurethane ye-Polyether
I-polyether polyurethane (PEU) isetshenziswa kabanzi ngenxa yamandla ayo aphansi okuhlangana kwezibopho ze-ether kumayunithi aphindaphindayo ezingxenye ezithambile, ukujikeleza okulula, ukuguquguquka okuhle kakhulu kwezinga lokushisa eliphansi kanye nokumelana ne-hydrolysis.
UKebir nabanye bahlanganisa i-polyether polyurethane ne-DMC, i-polyethylene glycol kanye ne-butanediol njengezinto zokusetshenziswa, kodwa isisindo sama-molecule sasiphansi (7 500 ~ 14 800g/mol), i-Tg yayiphansi kune-0℃, kanti nephuzu lokuncibilika laliphansi (38 ~ 48℃), kanti amandla nezinye izinkomba kwakunzima ukuhlangabezana nezidingo zokusetshenziswa. Iqembu locwaningo likaZhao Jingbo lisebenzise i-ethylene carbonate, i-1, i-6-hexanediamine kanye ne-polyethylene glycol ukuhlanganisa i-PEU, enesisindo sama-molecule esingu-31 000g/mol, amandla okudonsa angu-5 ~ 24MPa, kanye nokwandiswa lapho kuphuka okungu-0.9% ~ 1 388%. Isisindo sama-molecule ochungechunge oluhlanganisiwe lwe-aromatic polyurethanes singu-17 300 ~ 21 000g/mol, i-Tg ingu-19 ~ 10℃, iphuzu lokuncibilika lingu-102 ~ 110℃, amandla okudonsa angu-12 ~ 38MPa, kanti izinga lokululama lokunwebeka okungu-200% okuqhubekayo lingu-69% ~ 89%.
Iqembu locwaningo likaZheng Liuchun noLi Chuncheng lalungisa i-intermediate 1, 6-hexamethylenediamine (BHC) ene-dimethyl carbonate kanye ne-1, 6-hexamethylenediamine, kanye ne-polycondensation enama-molecule amancane ahlukene ama-diols aqondile kanye ne-polytetrahydrofuranediols (Mn=2 000). Kwalungiswa uchungechunge lwama-polyether polyurethanes (NIPEU) anomzila ongeyona i-isocyanate, futhi inkinga yokuxhumanisa ama-intermediates ngesikhathi sokusabela yaxazululwa. Isakhiwo kanye nezakhiwo ze-polyether polyurethane (HDIPU) yendabuko elungiselelwe yi-NIPEU kanye ne-1, 6-hexamethylene diisocyanate kwaqhathaniswa, njengoba kuboniswe kuThebula 1.
| Isampula | Ingxenye yesisindo sengxenye eqinile/% | Isisindo sama-molecule/(g)·mol^(-1)) | Inkomba yokusatshalaliswa kwesisindo sama-molecule | Amandla okudonsa/i-MPa | Ukwelulwa ngesikhathi sokuphumula/% |
| I-NIPEU30 | 30 | 74000 | 1.9 | 12.5 | 1250 |
| I-NIPEU40 | 40 | 66000 | 2.2 | 8.0 | 550 |
| I-HDIPU30 | 30 | 46000 | 1.9 | 31.3 | 1440 |
| I-HDIPU40 | 40 | 54000 | 2.0 | 25.8 | 1360 |
Ithebula 1
Imiphumela kuThebula 1 ikhombisa ukuthi umehluko wesakhiwo phakathi kwe-NIPEU ne-HDIPU ubangelwa kakhulu yisigaba esiqinile. Iqembu le-urea elikhiqizwa ukusabela ohlangothini lwe-NIPEU lifakwa ngokungahleliwe kuchungechunge lwama-molecule lwesigaba esiqinile, liphula isigaba esiqinile ukuze lakhe ama-hydrogen bonds ahlelekile, okuholela ezibophweni ze-hydrogen ezibuthakathaka phakathi kwama-molecule chains esigaba esiqinile kanye ne-crystallinity ephansi yesigaba esiqinile, okuholela ekuhlukanisweni kwesigaba esiphansi se-NIPEU. Ngenxa yalokho, izakhiwo zalo zemishini zimbi kakhulu kune-HDIPU.
2.2 I-Polyester Polyurethane
I-polyester polyurethane (PETU) ene-polyester diols njengezingxenye ezithambile inokubola okuhle, ukuhambisana kwezinto eziphilayo kanye nezakhiwo zemishini, futhi ingasetshenziswa ukulungiselela izicafu zobunjiniyela bezicubu, okuyinto yezokwelapha enamathuba amahle okusetshenziswa. Ama-polyester diols avame ukusetshenziswa ezigabeni ezithambile yi-polybutylene adipate diol, i-polyglycol adipate diol kanye ne-polycaprolactone diol.
Ngaphambilini, uRokicki nabanye baphendule i-ethylene carbonate nge-diamine kanye nama-diols ahlukene (1, 6-hexanediol,1, 10-n-dodecanol) ukuthola i-NIPU ehlukile, kodwa i-NIPU eyenziwe yayinesisindo esiphansi sama-molecule kanye ne-Tg ephansi. UFarhadian nabanye balungiselela i-polycyclic carbonate besebenzisa uwoyela wembewu yelanga njengezinto zokusetshenziswa, base bexuba nama-polyamine asekelwe ku-bio, ambozwe epuletini, futhi ahlanzwa ku-90 ℃ amahora angama-24 ukuthola ifilimu ye-polyester polyurethane e-thermosetting, ebonise ukuzinza okuhle kokushisa. Iqembu locwaningo likaZhang Liqun laseSouth China University of Technology lenze uchungechunge lwama-diamine nama-cyclic carbonate, base behlanganisa ne-biobased dibasic acid ukuthola i-polyester polyurethane esuselwe ku-bio. Iqembu locwaningo likaZhu Jin e-Ningbo Institute of Materials Research, i-Chinese Academy of Sciences lilungiselele i-diaminodiol hard segment besebenzisa i-hexadiamine kanye ne-vinyl carbonate, bese kuba yi-polycondensation ene-bio-based unsaturated dibasic acid ukuthola uchungechunge lwe-polyester polyurethane, engasetshenziswa njengopende ngemva kokwelashwa kwe-ultraviolet [23]. Iqembu locwaningo likaZheng Liuchun noLi Chuncheng lisebenzise i-adipic acid kanye nama-aliphatic diol amane (i-butanediol, i-hexadiol, i-octanediol kanye ne-decanediol) anezinombolo ze-athomu ze-carbon ezahlukene ukuze kulungiselelwe ama-polyester diol afanayo njengezingxenye ezithambile; Iqembu le-non-isocyanate polyester polyurethane (PETU), eliqanjwe ngenani lama-athomu e-carbon ama-aliphatic diols, latholakala ngokuncibilikisa i-polycondensation nge-hydroxy-sealed hard segment prepolymer elungiselelwe yi-BHC nama-diols. Izakhiwo ze-PETU ziboniswe kuThebula 2.
| Isampula | Amandla okudonsa/i-MPa | Imodulus enwebekayo/MPa | Ukwelulwa ngesikhathi sokuphumula/% |
| I-PETU4 | 6.9±1.0 | 36±8 | 673±35 |
| I-PETU6 | 10.1±1.0 | 55±4 | 568±32 |
| I-PETU8 | 9.0±0.8 | 47±4 | 551±25 |
| I-PETU10 | 8.8±0.1 | 52±5 | 137±23 |
Ithebula 2
Imiphumela ikhombisa ukuthi ingxenye ethambile ye-PETU4 inobuningi obukhulu kakhulu be-carbonyl, isibopho se-hydrogen esinamandla kakhulu nengxenye eqinile, kanye nezinga eliphansi kakhulu lokuhlukaniswa kwesigaba. Ukukristala kwezingxenye ezithambile neziqinile kulinganiselwe, okubonisa iphuzu eliphansi lokuncibilika kanye namandla okudonsa, kodwa ubude obuphezulu kakhulu lapho kuphuka.
2.3 I-polycarbonate polyurethane
I-Polycarbonate polyurethane (PCU), ikakhulukazi i-aliphatic PCU, inokumelana okuhle kakhulu kwe-hydrolysis, ukumelana ne-oxidation, ukuzinza okuhle kwezinto eziphilayo kanye nokuhambisana kwezinto eziphilayo, futhi inamathuba amahle okusetshenziswa emkhakheni wezokwelapha nge-biomedicine. Njengamanje, iningi le-NIPU elilungisiwe lisebenzisa ama-polyol e-polyether kanye nama-polyol e-polyester njengezingxenye ezithambile, futhi kunemibiko embalwa yocwaningo nge-polycarbonate polyurethane.
I-polyurethane ye-polycarbonate engeyona isocyanate elungiselelwe yiqembu locwaningo likaTian Hengshui eSouth China University of Technology inesisindo sama-molecule esingaphezu kuka-50 000 g/mol. Ithonya lezimo zokusabela esisindweni sama-molecule se-polymer liye lafundwa, kodwa izakhiwo zayo zomshini azikabikwa. Iqembu locwaningo likaZheng Liuchun noLi Chuncheng balungiselele i-PCU besebenzisa i-DMC, i-hexanediamine, i-hexadiol kanye ne-polycarbonate diols, futhi baqamba i-PCU ngokwengxenye yobuningi beyunithi ephindaphindayo yesigaba esiqinile. Izakhiwo zomshini ziboniswe kuThebula 3.
| Isampula | Amandla okudonsa/i-MPa | Imodulus enwebekayo/MPa | Ukwelulwa ngesikhathi sokuphumula/% |
| I-PCU18 | 17±1 | 36±8 | 665±24 |
| I-PCU33 | 19±1 | 107±9 | 656±33 |
| I-PCU46 | 21±1 | 150±16 | 407±23 |
| I-PCU57 | 22±2 | 210±17 | 262±27 |
| I-PCU67 | 27±2 | 400±13 | 63±5 |
| I-PCU82 | 29±1 | 518±34 | 26±5 |
Ithebula 3
Imiphumela ikhombisa ukuthi i-PCU inesisindo esikhulu sama-molecule, kufika ku-6×104 ~ 9×104g/mol, iphuzu lokuncibilika kufika ku-137 ℃, kanye namandla okuthamba afika ku-29 MPa. Lolu hlobo lwe-PCU lungasetshenziswa njengepulasitiki eqinile noma njenge-elastomer, enethuba elihle lokusetshenziswa emkhakheni wezokwelapha (njengezicafu zobunjiniyela bezicubu zabantu noma izinto zokufakelwa kwenhliziyo).
2.4 I-polyurethane ehlanganisiwe engeyona i-isocyanate
I-hybrid non-isocyanate polyurethane (i-hybrid NIPU) ukwethulwa kwe-epoxy resin, i-acrylate, i-silica noma amaqembu e-siloxane ohlakeni lwama-molecular e-polyurethane ukuze kwakhiwe inethiwekhi ehlanganisayo, kuthuthukiswe ukusebenza kwe-polyurethane noma kunikezwe imisebenzi ehlukene ye-polyurethane.
UFeng Yuelan nabanye baphendule uwoyela wesoya we-epoxy osekelwe ku-bio nge-CO2 ukuze kuhlanganiswe i-pentamonic cyclic carbonate (CSBO), futhi bethula i-bisphenol A diglycidyl ether (i-epoxy resin E51) enezingxenye zeketanga eziqinile ukuze kuthuthukiswe i-NIPU eyakhiwe yi-CSBO eqiniswe nge-amine. Iketanga lama-molecule liqukethe ingxenye yeketanga ende eguquguqukayo ye-oleic acid/linoleic acid. Liphinde liqukethe izingxenye zeketanga eziqinile, ukuze libe namandla aphezulu okusebenza kanye nokuqina okuphezulu. Abanye abacwaningi baphinde bahlanganisa izinhlobo ezintathu zama-prepolymer e-NIPU anamaqembu okuphela kwe-furan ngokusebenzisa ukusabela kokuvula kwe-diethylene glycol bicyclic carbonate kanye ne-diamine, bese bephendula nge-polyester engagcwalisiwe ukuze kulungiselelwe i-polyurethane ethambile enomsebenzi wokuziphilisa, futhi baphumelela ekutholeni ukusebenza kahle okuphezulu kokuziphilisa kwe-NIPU ethambile. I-Hybrid NIPU ayinazo nje kuphela izici ze-NIPU ejwayelekile, kodwa futhi ingaba nokunamathela okungcono, ukumelana nokugqwala kwe-asidi kanye ne-alkali, ukumelana nokunyibilika kanye namandla okusebenza.
3 Ukubuka
I-NIPU ilungiswa ngaphandle kokusebenzisa i-isocyanate enobuthi, futhi okwamanje ihlolwa ngesimo se-foam, i-coating, i-glue, i-elastomer neminye imikhiqizo, futhi inezinhlobo eziningi zamathemba okusetshenziswa. Kodwa-ke, iningi lazo lisakhawulelwe ocwaningweni lwelabhorethri, futhi akukho ukukhiqizwa okukhulu. Ngaphezu kwalokho, ngokuthuthukiswa kwezindinganiso zokuphila zabantu kanye nokukhula okuqhubekayo kwesidingo, i-NIPU enomsebenzi owodwa noma imisebenzi eminingi isibe isiqondiso esibalulekile socwaningo, njengokulwa namagciwane, ukuzilungisa, inkumbulo yesimo, ukuvimbela ilangabi, ukumelana nokushisa okuphezulu njalonjalo. Ngakho-ke, ucwaningo lwesikhathi esizayo kufanele luqonde ukuthi lungazidabula kanjani izinkinga ezibalulekile zokuthuthukiswa kwezimboni futhi luqhubeke nokuhlola isiqondiso sokulungiselela i-NIPU esebenzayo.
Isikhathi sokuthunyelwe: Agasti-29-2024