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세계에서 가장 많이 생산되는 플라스틱 소재

Materials Science & Polymers Global Industrial Scale $140 billion

개요

Polyethylene (PE) is the most produced plastic globally, manufactured through catalytic polymerization of ethylene. Three major grades exist: HDPE (high density, linear chains via Ziegler-Natta or chromium catalysts), LDPE (low density, branched chains via free-radical high-pressure process), and LLDPE (linear low density, gas-phase with metallocene catalysts). The development of Ziegler-Natta catalysts earned Karl Ziegler and Giulio Natta the 1963 Nobel Prize in Chemistry.

화학 공정

For HDPE: ethylene is polymerized at 80-150 degrees C and 10-80 bar using Ziegler-Natta (TiCl4/MgCl2 + AlEt3) or Phillips (CrO3/SiO2) catalysts in gas-phase fluidized bed or slurry reactors. For LDPE: ethylene is polymerized at 150-300 degrees C and 1000-3000 bar using peroxide initiators in tubular or autoclave reactors.

nCH2=CH2 ->[catalyst] -(CH2-CH2)n- (addition polymerization, DeltaH = -93.6 kJ/mol)

원자재

Ethylene (C2H4) — Steam cracking of hydrocarbons (Monomer)
1-Hexene or 1-butene — Oligomerization of ethylene (Comonomer (for LLDPE))
Ziegler-Natta catalyst (TiCl4/MgCl2) — Chemical synthesis (Polymerization catalyst)

최종 제품

Polyethylene resin pellets — Films, bottles, pipes, containers, toys (HDPE (0.941-0.965 g/cm3), LDPE (0.910-0.940 g/cm3))

Environmental Impact

Polyethylene is a major contributor to plastic pollution in oceans and landfills. Only about 30% is recycled globally. Microplastic formation from PE degradation is an emerging concern. Production from fossil ethylene contributes to CO2 emissions, though bio-based PE from sugarcane ethanol is now commercially available.

안전 고려사항

⚠ Ethylene is extremely flammable and explosive
⚠ High-pressure LDPE reactors operate at 1000-3000 bar -- catastrophic failure risk
⚠ Organoaluminum co-catalysts are pyrophoric
⚠ Fine polymer dust is an explosion hazard

최근 혁신

Chemical recycling via pyrolysis converts PE waste back to monomers.
Bio-based polyethylene from sugarcane ethanol (Braskem I'm green PE) provides a renewable alternative.
Single-site metallocene catalysts enable precise control of molecular architecture.