Sab hauv tov khoom yog tsuas yog siv rau hauv kev lag luam roj hmab thiab kev lag luam yas.
Hauv kev lag luam roj hmab, nws tau siv dav hauv kev tsim cov log tsheb tsheb. Cov log tsheb tsheb yuav tsum tau ntau cov roj hmab thiab cov roj hmab sib xyaw ua ke, cov roj hmab sib xyaw ua ke, cov roj hmab muaj cov khoom siv sib xyaw zoo, kev tiv thaiv thiab lub zog. Nyob rau tib lub sijhawm, nws kuj tseem siv los ua ntau yam khoom siv roj hmab, xws li cov ntaub pua roj hmab, cov khoom lag luam tuaj yeem tau elasticity zoo, muaj kuab lom thiab lwm yam khoom.
Hauv kev lag luam plastics, cov tov khoom sab hauv tuaj yeem siv los ua cov thermoplastics. Piv txwv li, thaum ua cov tshuaj polyvinyl chloride (pvc, cov kav dej sib xyaw nrog cov khoom sib xyaw thiab cov khoom siv ntxiv thiab txhim kho lub cev ntawm cov plastics. Nws tseem haum rau kev ua cov thermosetting plastics, xws li cov kev sib xyaw ntawm phenolic resin, uas pab kom kho kom zoo dua thaum lub sij hawm moulding txheej txheem thiab txhim kho qhov zoo ntawm cov khoom.
