1. Dab tsi yog ib qhopolymerkev pab ua cov ntaub ntawv? Nws muaj lub luag haujlwm dab tsi?
Lus Teb: Cov khoom ntxiv yog ntau yam tshuaj pab uas yuav tsum tau ntxiv rau qee cov ntaub ntawv thiab cov khoom lag luam hauv cov txheej txheem tsim khoom lossis kev ua haujlwm kom txhim kho cov txheej txheem tsim khoom thiab txhim kho kev ua haujlwm ntawm cov khoom. Hauv cov txheej txheem ntawm kev ua cov resins thiab roj hmab nyoos rau hauv cov khoom yas thiab roj hmab, ntau yam tshuaj pab yog qhov xav tau.
Kev Ua Haujlwm: ① Txhim kho cov txheej txheem ua haujlwm ntawm cov polymers, ua kom zoo dua cov xwm txheej ua haujlwm, thiab xa cov txheej txheem ua haujlwm zoo; ② Txhim kho kev ua tau zoo ntawm cov khoom, txhim kho lawv tus nqi thiab lub neej ntev.
2. Qhov sib xws ntawm cov khoom ntxiv thiab cov polymers yog dab tsi? Lub ntsiab lus ntawm kev txau thiab kev tawm hws yog dab tsi?
Lus Teb: Tshuaj tsuag polymerization - nag ntawm cov khoom ntxiv khov; hws - nag ntawm cov kua ntxiv.
Qhov sib xws ntawm cov khoom ntxiv thiab cov polymers hais txog lub peev xwm ntawm cov khoom ntxiv thiab cov polymers kom sib xyaw ua ke ntev ntev yam tsis muaj kev sib cais theem thiab nag lossis daus;
3. Lub luag haujlwm ntawm cov yas yas yog dab tsi?
Lus Teb: Ua kom cov kev sib txuas theem nrab ntawm cov polymer molecules qaug zog, hu ua van der Waals forces, ua rau cov polymer chains txav mus los ntau dua thiab txo lawv cov crystallinity.
4. Vim li cas polystyrene thiaj muaj kev tiv thaiv oxidation zoo dua li polypropylene?
Lus Teb: H tsis ruaj khov raug hloov los ntawm ib pawg phenyl loj, thiab qhov laj thawj uas PS tsis yooj yim laus yog tias lub nplhaib benzene muaj cov nyhuv tiv thaiv rau H; PP muaj tertiary hydrogen thiab yooj yim laus.
5. Dab tsi yog vim li cas PVC thiaj tsis ruaj khov cua sov?
Lus Teb: ① Cov qauv molecular saw muaj cov initiator residues thiab allyl chloride, uas ua kom cov pab pawg ua haujlwm. Qhov kawg pab pawg ob chav sib txuas txo qhov thermal stability; ② Qhov cuam tshuam ntawm oxygen ua kom nrawm dua qhov kev tshem tawm ntawm HCL thaum lub sijhawm thermal degradation ntawm PVC; ③ HCl tsim los ntawm cov tshuaj tiv thaiv muaj cov nyhuv catalytic rau qhov kev puas tsuaj ntawm PVC; ④ Qhov cuam tshuam ntawm cov tshuaj plasticizer.
6. Raws li cov txiaj ntsig tshawb fawb tam sim no, cov haujlwm tseem ceeb ntawm cov khoom siv cua sov yog dab tsi?
Lus Teb: ① Nqus thiab neutralize HCL, inhibit nws cov catalytic effect; ② Hloov cov allyl chloride atoms tsis ruaj khov hauv PVC molecules kom inhibit qhov extraction ntawm HCl; ③ Ntxiv cov tshuaj tiv thaiv nrog polyene qauv cuam tshuam kev tsim ntawm cov kab ke loj conjugated thiab txo cov xim; ④ Ntes cov free radicals thiab tiv thaiv cov tshuaj oxidation; ⑤ Neutralization lossis passivation ntawm cov hlau ions lossis lwm yam tshuaj lom neeg uas catalyze degradation; ⑥ Nws muaj kev tiv thaiv, tiv thaiv, thiab ua kom tsis muaj zog rau ultraviolet radiation.
7. Vim li cas lub teeb ultraviolet thiaj ua rau cov polymers puas tsuaj ntau tshaj?
Lus Teb: Cov nthwv dej ultraviolet ntev thiab muaj zog, rhuav tshem feem ntau cov polymer chemical bonds.
8. Cov tshuaj tua hluav taws intumescent yog hom synergistic system twg, thiab nws lub hauv paus ntsiab lus thiab kev ua haujlwm yog dab tsi?
Lus Teb: Cov tshuaj tiv thaiv hluav taws kub hnyiab yog cov khoom siv sib xyaw ua ke ntawm phosphorus nitrogen.
Txoj Kev Ua Haujlwm: Thaum cov polymer uas muaj cov tshuaj tua hluav taws kub, yuav muaj ib txheej ua npuas carbon sib npaug zos rau ntawm nws qhov chaw. Cov txheej no muaj peev xwm tua hluav taws kub zoo vim nws muaj kev rwb thaiv cua sov, kev rho tawm cov pa oxygen, kev tswj pa luam yeeb thiab kev tiv thaiv dej ntws.
9. Qhov ntsuas pa oxygen yog dab tsi, thiab qhov sib raug zoo ntawm qhov loj ntawm qhov ntsuas pa oxygen thiab qhov ua kom nplaim taws tsis kub yog dab tsi?
Lus Teb: OI=O2/(O2 N2) x 100%, qhov twg O2 yog tus nqi ntws oxygen; N2: Tus nqi ntws Nitrogen. Cov pa oxygen index yog hais txog feem pua ntawm cov pa oxygen uas xav tau hauv cov pa oxygen nitrogen thaum ib qho qauv tshwj xeeb tuaj yeem hlawv tas li thiab ruaj khov zoo li lub tswm ciab. OI <21 yog flammable, OI yog 22-25 nrog cov khoom tua tus kheej, 26-27 nyuaj rau hlawv, thiab siab dua 28 yog nyuaj heev rau hlawv.
10. Lub tshuab ua kom tsis txhob muaj hluav taws kub antimony halide ua rau muaj kev cuam tshuam li cas?
Lus Teb: Sb2O3 feem ntau siv rau antimony, thaum cov organic halides feem ntau siv rau halides. Sb2O3 / tshuab siv nrog halides feem ntau vim nws cuam tshuam nrog cov hydrogen halide tso tawm los ntawm cov halides.
Thiab cov khoom no raug cua sov ua rau SbCl3, uas yog cov roj volatile nrog lub point boiling qis. Cov roj no muaj qhov ceev ceev thiab tuaj yeem nyob hauv thaj chaw combustion ntev kom dilute cov roj flammable, cais cov huab cua, thiab ua lub luag haujlwm hauv kev thaiv olefins; Qhov thib ob, nws tuaj yeem ntes cov radicals dawb combustible kom txo cov nplaim taws. Tsis tas li ntawd, SbCl3 condenses rau hauv cov dej ntws zoo li cov khoom khov kho hla cov nplaim taws, thiab nws cov phab ntsa cuam tshuam ntau qhov kub, qeeb lossis nres qhov ceev combustion. Feem ntau hais lus, qhov sib piv ntawm 3: 1 yog qhov tsim nyog dua rau chlorine rau cov hlau atoms.
11. Raws li kev tshawb fawb tam sim no, cov txheej txheem ua haujlwm ntawm cov tshuaj tiv thaiv hluav taws yog dab tsi?
Lus Teb: ① Cov khoom lwj ntawm cov nplaim taws retardants ntawm qhov kub combustion tsim cov zaj duab xis iav tsis-volatile thiab tsis oxidizing, uas tuaj yeem cais cov cua reflection zog lossis muaj cov thermal conductivity qis.
② Cov tshuaj tua hluav taws kub hnyiab mus rau hauv qhov kub thiab txias kom tsim cov pa roj uas tsis kub hnyiab, yog li ntawd cov pa roj uas kub hnyiab thiab ua rau cov pa oxygen hauv thaj chaw kub hnyiab tsis sib xyaw; ③ Kev yaj thiab kev lwj ntawm cov tshuaj tua hluav taws kub nqus tau cua sov thiab haus cua sov;
④ Cov tshuaj tiv thaiv hluav taws xob txhawb kev tsim cov txheej rwb thaiv tsev thermal porous rau ntawm qhov chaw ntawm cov yas, tiv thaiv kev coj cua sov thiab kev kub hnyiab ntxiv.
12. Vim li cas cov yas thiaj li raug hluav taws xob thaum lub sijhawm ua lossis siv?
Lus Teb: Vim yog qhov tseeb tias cov saw hlau molecular ntawm cov polymer tseem ceeb feem ntau yog tsim los ntawm cov ntawv cog lus covalent, lawv tsis tuaj yeem ionize lossis hloov cov electrons. Thaum lub sijhawm ua thiab siv nws cov khoom, thaum nws los rau hauv kev sib cuag thiab kev sib txhuam nrog lwm yam khoom lossis nws tus kheej, nws raug them vim yog qhov nce lossis poob ntawm cov electrons, thiab nws nyuaj rau ploj mus los ntawm kev coj tus kheej.
13. Cov yam ntxwv ntawm cov qauv molecular ntawm cov neeg sawv cev antistatic yog dab tsi?
Lus Teb: RYX R: pawg oleophilic, Y: pawg txuas, X: pawg hydrophilic. Hauv lawv cov molecule, yuav tsum muaj qhov sib npaug zoo ntawm pawg oleophilic uas tsis yog polar thiab pawg polar hydrophilic, thiab lawv yuav tsum muaj qee qhov sib xws nrog cov ntaub ntawv polymer. Cov pawg alkyl saum toj no C12 yog cov pawg oleophilic ib txwm muaj, thaum hydroxyl, carboxyl, sulfonic acid, thiab ether bonds yog cov pawg hydrophilic ib txwm muaj.
14. Piav qhia luv luv txog cov txheej txheem ua haujlwm ntawm cov tshuaj tiv thaiv hluav taws xob.
Lus Teb: Ua ntej, cov neeg sawv cev tiv thaiv hluav taws xob tsim cov zaj duab xis txuas ntxiv mus rau saum npoo ntawm cov khoom, uas tuaj yeem muab qhov chaw ntawm cov khoom nrog qee qib ntawm hygroscopicity thiab ionization, yog li txo qhov resistivity ntawm qhov chaw thiab ua rau cov nqi hluav taws xob tsim tawm sai sai, txhawm rau ua tiav lub hom phiaj ntawm anti-static; Qhov thib ob yog muab qhov chaw ntawm cov khoom nrog qee qib ntawm lubrication, txo cov coefficient sib txhuam, thiab yog li ntawd suppress thiab txo qhov tiam ntawm cov nqi hluav taws xob.
① Cov neeg sawv cev tiv thaiv hluav taws xob sab nraud feem ntau siv ua cov kuab tshuaj lossis cov khoom sib cais nrog dej, cawv, lossis lwm yam kuab tshuaj organic. Thaum siv cov neeg sawv cev tiv thaiv hluav taws xob los impregnate cov ntaub ntawv polymer, qhov hydrophilic ntawm tus neeg sawv cev tiv thaiv hluav taws xob yuav nqus tau zoo rau ntawm qhov chaw ntawm cov khoom, thiab qhov hydrophilic nqus dej los ntawm huab cua, yog li tsim cov txheej conductive rau ntawm qhov chaw ntawm cov khoom, uas ua lub luag haujlwm hauv kev tshem tawm hluav taws xob zoo li qub;
② Tus neeg sawv cev tiv thaiv kev zoo li qub sab hauv yog sib xyaw rau hauv cov polymer matrix thaum lub sijhawm ua cov yas, thiab tom qab ntawd tsiv mus rau qhov chaw ntawm cov polymer los ua lub luag haujlwm tiv thaiv kev zoo li qub;
③ Cov tshuaj polymer sib xyaw ua ke uas tiv thaiv tau hluav taws xob tas mus li yog ib txoj kev sib xyaw cov polymers hydrophilic rau hauv cov polymer los tsim cov channel conductive uas coj thiab tso cov nqi hluav taws xob tas mus li.
15. Feem ntau muaj kev hloov pauv dab tsi hauv cov qauv thiab cov khoom ntawm roj hmab tom qab vulcanization?
Lus Teb: ① Cov roj hmab vulcanized tau hloov pauv ntawm cov qauv linear mus rau cov qauv network peb-seem; ② Cua sov tsis ntws lawm; ③ Tsis yaj hauv nws cov kuab tshuaj zoo lawm; ④ Txhim kho modulus thiab hardness; ⑤ Txhim kho cov khoom siv kho tshuab; ⑥ Txhim kho kev tiv thaiv kev laus thiab kev ruaj khov tshuaj lom neeg; ⑦ Kev ua tau zoo ntawm cov khoom nruab nrab yuav txo qis.
16. Qhov txawv ntawm sulfur sulfide thiab sulfur donor sulfide yog dab tsi?
Lus Teb: ① Sulfur vulcanization: Ntau cov sulfur bonds, tiv taus cua sov, tsis laus tsis kam, yooj ywm zoo, thiab deformation loj tas mus li; ② Sulfur pub: Ntau cov sulfur bonds, tiv taus cua sov zoo thiab tiv taus kev laus.
17. Tus neeg txhawb nqa vulcanization ua dab tsi?
Lus Teb: Txhim kho kev tsim khoom ntawm cov khoom siv roj hmab, txo cov nqi, thiab txhim kho kev ua tau zoo. Cov tshuaj uas tuaj yeem txhawb kev vulcanization. Nws tuaj yeem ua rau lub sijhawm vulcanization luv dua, txo qhov kub ntawm vulcanization, txo cov tshuaj vulcanizing, thiab txhim kho cov khoom siv lub cev thiab cov khoom siv kho tshuab ntawm roj hmab.
18. Qhov tshwm sim hlawv: hais txog qhov tshwm sim ntawm kev vulcanization thaum ntxov ntawm cov khoom siv roj hmab thaum lub sijhawm ua tiav.
19. Piav qhia luv luv txog kev ua haujlwm thiab cov hom tseem ceeb ntawm cov neeg sawv cev vulcanizing
Lus Teb: Lub luag haujlwm ntawm tus activator yog los txhim kho qhov kev ua haujlwm ntawm lub accelerator, txo cov koob tshuaj ntawm lub accelerator, thiab luv lub sijhawm vulcanization.
Tus neeg sawv cev nquag: ib yam khoom uas tuaj yeem ua rau cov organic accelerators ua haujlwm ntau dua, ua rau lawv siv tau zoo tag nrho, yog li txo cov accelerators siv lossis luv lub sijhawm vulcanization. Cov neeg sawv cev nquag feem ntau muab faib ua ob pawg: cov neeg sawv cev inorganic nquag thiab cov neeg sawv cev organic nquag. Inorganic surfactants feem ntau suav nrog cov hlau oxides, hydroxides, thiab cov carbonates yooj yim; Organic surfactants feem ntau suav nrog cov roj fatty acids, amines, xab npum, polyols, thiab amino alcohols. Ntxiv me ntsis ntawm activator rau cov roj hmab tuaj yeem txhim kho nws qib vulcanization.
1) Cov neeg sawv cev tsis muaj zog: feem ntau yog cov hlau oxides;
2) Cov neeg sawv cev ua haujlwm organic: feem ntau yog cov roj fatty acids.
Ceeb Toom: ① ZnO siv tau ua tus neeg sawv cev hlau oxide vulcanizing los txuas cov roj hmab halogenated; ② ZnO tuaj yeem txhim kho qhov kub tsis kam ntawm cov roj hmab vulcanized.
20. Cov teebmeem tom qab ntawm cov accelerators yog dab tsi thiab cov hom accelerators twg muaj cov teebmeem tom qab zoo?
Lus Teb: Hauv qab qhov kub ntawm vulcanization, nws yuav tsis ua rau vulcanization ntxov. Thaum qhov kub ntawm vulcanization raug ncav cuag, qhov kev ua haujlwm vulcanization siab, thiab cov khoom no hu ua post effect ntawm lub accelerator. Sulfonamides muaj cov teebmeem post effects zoo.
21. Kev txhais ntawm cov roj nplua nyeem thiab qhov sib txawv ntawm cov roj nplua nyeem sab hauv thiab sab nraud?
Lus Teb: Cov roj nplua nyeem - ib qho khoom ntxiv uas tuaj yeem txhim kho qhov kev sib txhuam thiab kev nplaum ntawm cov yas me me thiab ntawm cov yaj thiab cov hlau ntawm cov khoom siv ua haujlwm, ua rau kom muaj kev npliag ntawm cov resin, ua tiav lub sijhawm hloov kho cov resin plasticization, thiab tswj kev tsim khoom tas mus li, hu ua roj nplua nyeem.
Cov roj nplua nyeem sab nraud tuaj yeem ua rau cov yas nto zoo dua thaum lub sijhawm ua haujlwm, txo qhov sib txuas ntawm cov yas thiab cov hlau nto, thiab txo qhov sib txuas ntawm lub zog, yog li ua tiav lub hom phiaj ntawm kev ua tiav yooj yim tshaj plaws yam tsis ua rau cov khoom ntawm cov yas puas tsuaj. Cov roj nplua nyeem sab hauv tuaj yeem txo qhov sib txhuam sab hauv ntawm cov polymers, ua rau kom cov nqi yaj thiab cov yas hloov pauv, txo cov viscosity yaj, thiab txhim kho kev ua haujlwm yas.
Qhov sib txawv ntawm cov roj nplua nyeem sab hauv thiab sab nraud: Cov roj nplua nyeem sab hauv xav tau kev sib raug zoo nrog cov polymers, txo kev sib txhuam ntawm cov saw hlau molecular, thiab txhim kho kev ua haujlwm ntws; Thiab cov roj nplua nyeem sab nraud xav tau qee qib kev sib raug zoo nrog cov polymers kom txo kev sib txhuam ntawm cov polymers thiab cov chaw machined.
22. Cov yam ntxwv twg uas txiav txim siab qhov loj ntawm cov nyhuv txhawb nqa ntawm cov khoom sau yog dab tsi?
Lus Teb: Qhov loj ntawm cov nyhuv txhawb zog nyob ntawm qhov qauv tseem ceeb ntawm cov yas nws tus kheej, qhov ntau ntawm cov khoom me me, thaj chaw tshwj xeeb thiab qhov loj me, kev ua haujlwm ntawm qhov chaw, qhov loj me ntawm cov khoom me me thiab kev faib tawm, cov qauv theem, thiab kev sib sau ua ke thiab kev faib tawm ntawm cov khoom me me hauv polymers. Qhov tseem ceeb tshaj plaws yog kev sib cuam tshuam ntawm cov khoom me me thiab cov txheej txheem sib txuas uas tsim los ntawm cov saw hlau polymer, uas suav nrog ob qho tib si lub zog lub cev lossis tshuaj lom neeg uas ua los ntawm cov khoom me me ntawm cov saw hlau polymer, nrog rau kev siv lead ua thiab kev taw qhia ntawm cov saw hlau polymer hauv cov txheej txheem sib txuas.
23. Muaj tej yam dab tsi cuam tshuam rau lub zog ntawm cov yas uas muaj zog?
Lus Teb: ① Lub zog ntawm tus neeg sawv cev txhawb nqa raug xaiv los ua kom tau raws li qhov yuav tsum tau ua; ② Lub zog ntawm cov polymers yooj yim tuaj yeem ua tiav los ntawm kev xaiv thiab kev hloov kho ntawm cov polymers; ③ Qhov kev sib txuas ntawm qhov chaw ntawm cov yas thiab cov polymers yooj yim; ④ Cov ntaub ntawv teeb tsa rau cov ntaub ntawv txhawb nqa.
24. Tus neeg sawv cev sib txuas yog dab tsi, nws cov yam ntxwv ntawm cov qauv molecular, thiab ib qho piv txwv los piav qhia txog txoj hauv kev ua haujlwm.
Lus Teb: Cov neeg sawv cev txuas yog hais txog ib hom tshuaj uas tuaj yeem txhim kho cov khoom sib txuas ntawm cov khoom sau thiab cov ntaub ntawv polymer.
Muaj ob hom pawg ua haujlwm hauv nws cov qauv molecular: ib qho tuaj yeem dhau los ua cov tshuaj lom neeg nrog cov polymer matrix lossis tsawg kawg muaj kev sib raug zoo; Lwm hom tuaj yeem tsim cov tshuaj sib txuas nrog cov inorganic fillers. Piv txwv li, silane coupling agent, cov mis dav dav tuaj yeem sau ua RSiX3, qhov twg R yog ib pawg ua haujlwm nquag nrog kev sib raug zoo thiab kev ua haujlwm nrog cov polymer molecules, xws li vinyl chloropropyl, epoxy, methacryl, amino, thiab thiol pawg. X yog ib pawg alkoxy uas tuaj yeem hydrolyzed, xws li methoxy, ethoxy, thiab lwm yam.
25. Tus neeg ua npuas dej yog dab tsi?
Lus Teb: Tus neeg sawv cev ua npuas dej yog ib hom tshuaj uas tuaj yeem tsim cov qauv microporous ntawm roj hmab lossis yas hauv cov kua lossis yas hauv qee qhov viscosity.
Tus neeg sawv cev ua npuas ncauj: ib hom tshuaj uas ua tiav cov hom phiaj ua npuas ncauj los ntawm kev vam khom kev hloov pauv hauv nws lub cev thaum lub sijhawm ua npuas ncauj;
Cov tshuaj ua npuas ncauj: Thaum muaj qhov kub thiab txias, nws yuav ua rau lub cev puas tsuaj los tsim ib lossis ntau cov pa roj, ua rau cov polymer ua npuas ncauj.
26. Cov yam ntxwv ntawm cov tshuaj inorganic thiab cov tshuaj organic hauv kev rhuav tshem cov tshuaj ua npuas dej yog dab tsi?
Lus Teb: Cov txiaj ntsig thiab qhov tsis zoo ntawm cov organic foaming agents: ① zoo dispersibility hauv polymers; ② Qhov kub ntawm decomposition yog nqaim thiab yooj yim tswj; ③ Cov roj N2 tsim tawm tsis hlawv, tawg, yooj yim liquefy, muaj qhov sib txawv qis, thiab tsis yooj yim khiav tawm ntawm cov ua npuas ncauj, ua rau muaj qhov siab ntawm cov ntaub thaiv; ④ Cov khoom me me ua rau muaj cov qhov me me ua npuas ncauj; ⑤ Muaj ntau yam; ⑥ Tom qab ua npuas ncauj, muaj ntau cov seem, qee zaum siab txog 70% -85%. Cov seem no qee zaum tuaj yeem ua rau muaj ntxhiab tsw, ua rau cov khoom polymer paug, lossis tsim cov xwm txheej te; ⑦ Thaum lub sijhawm decomposition, nws feem ntau yog qhov tshuaj tiv thaiv exothermic. Yog tias qhov kub ntawm decomposition ntawm cov neeg sawv cev ua npuas ncauj siv siab dhau, nws yuav ua rau muaj qhov kub thiab txias loj sab hauv thiab sab nraud ntawm lub cev ua npuas ncauj thaum lub sijhawm ua npuas ncauj, qee zaum ua rau muaj qhov kub thiab txias sab hauv thiab ua rau puas tsuaj rau cov khoom siv lub cev thiab tshuaj ntawm cov polymer. Cov neeg sawv cev ua npuas ncauj organic feem ntau yog cov khoom siv hluav taws xob, thiab yuav tsum tau them sai sai rau kev tiv thaiv hluav taws thaum khaws cia thiab siv.
27. Xim masterbatch yog dab tsi?
Lus Teb: Nws yog ib qho kev sib xyaw ua los ntawm kev thauj cov xim lossis cov xim tsis tu ncua rau hauv cov roj hmab; Cov khoom tseem ceeb: cov xim lossis cov xim, cov neeg nqa khoom, cov khoom tawg, cov khoom ntxiv; Kev Ua Haujlwm: ① Pab tau rau kev tswj hwm cov tshuaj lom neeg thiab cov xim ruaj khov ntawm cov xim; ② Txhim kho qhov kev tawg ntawm cov xim hauv cov yas; ③ Tiv thaiv kev noj qab haus huv ntawm cov neeg teb xov tooj; ④ Cov txheej txheem yooj yim thiab kev hloov xim yooj yim; ⑤ Ib puag ncig huv si thiab tsis ua rau cov khoom siv puas tsuaj; ⑥ Txuag lub sijhawm thiab cov khoom siv raw.
28. Lub hwj chim ntawm kev pleev xim yog hais txog dab tsi?
Lus Teb: Nws yog lub peev xwm ntawm cov xim los cuam tshuam rau xim ntawm tag nrho cov sib tov nrog lawv tus kheej xim; Thaum cov neeg sawv cev xim siv rau hauv cov khoom yas, lawv lub zog npog yog hais txog lawv lub peev xwm los tiv thaiv lub teeb kom tsis txhob nkag mus rau hauv cov khoom.
Lub sijhawm tshaj tawm: Plaub Hlis-11-2024