Polymers thiab cov ntaub ntawv tsim los ntawm lawv, cov khoom siv hauv tsev, khoom siv yog ib feem tseem ceeb ntawm kev lag luam thiab tib neeg lub neej. Cov peev txheej ntuj, hmoov tsis, tau depleted heev thaum lawv siv. Yog li ntawd, tib neeg yuav tsum tau kawm yuav ua li cas los tsim cov khoom siv dag zog uas muaj cov yam ntxwv tseem ceeb