Cov khoom siv ntawm tsheb roj taw
Cov khoom siv ntawm cov roj hmab ko taw ncoo yog ib hom hluavtaws polymer. Nws yog cov kua nyeem ua kua lossis cov khoom uas muaj peev xwm tuaj yeem muag los ntawm cua kub. Nws feem ntau muaj huab cua yaj melting los yog muag muag thaum kub. Nws tuaj yeem xav tias lub xeev ntws ntawm cov zog sab nraud. Qee cov khoom muaj ntsis zoo ib yam li resins ntuj.