High pressure-low density polyethylene (HP-LDPE, abbreviated as LDPE) hi kum 70 chuang zet chu industrialized a ni tawh a, mahse olefin polymerization catalyst hmuhchhuah leh siam chhuah a nih tak avangin polyethylene chi hrang hrang leh output hi a nasa hle a ni. Mahse, high-pressure polyethylene hian hmun pawimawh tak a la luah reng a ni. Ethylene hi temperature sang leh pressure sang takah free radical mechanism hmangin high molecular weight polyethylene ah polymerized a ni a, hei hian a hnuaia mi ang hian a nei a ni:
(1) Ethylene polymerization reaction process hi exothermic process chak tak a ni. Ethylene polymerization lumna chu 93.5kJ/mol (or 3.3kJ/g) vel a ni a, 235MPa leh 150~300 degree-a ethylene specific heat capacity chu 2.51~2.85J/(g· degree) a ni. Reaction lumna chu a hun taka lak chhuah theih a nih loh chuan, a vawi khatnaah Polymerization of 1% ethylene chuan temperature chu 12 to 13℃in a tisang ang. Temperature a san lutuk chuan ethylene a ti chhe bawk ang.
(2) Pressure sang tak hnuaiah ethylene chu airtight phase-ah density 0.5g/mL-ah compress a ni a, chu chu compress theih loh liquid nen a inang a ni. Hetih lai hian ethylene molecule inkar hlat zawng chu nasa takin a tawi a, chu chuan free radical leh ethylene molecule a tipung a ni. Collision probability a sang avangin polymerization reaction a awm duh hle.
(3) Temperature sang takah chuan chain lo thang lian zel free radical activity chu a lian hle a, chain transfer reaction pawh a awm duh hle a, polymer hmuh chhuah chu linear structure neiin branched chain tam zawk a nei bawk. A tlangpuiin carbon chain atom 1000 ah hian branch 20-30 vel a awm a, crystallinity 45%-65%, density 0.910-0.925g/mL, light weight, flexible, low temperature resistance leh impact resistance a ni.