3-14a Polyethylene Radical chain polymerization of ethylene to polyethylene is carried out at high pressures of 120-300 MPa (7,000 43.000 psi) and at temperatures above the Tim of polyethylene. Batch processes are not useful since the long residence time gives relatively poor control of product properties. Long-chain branching due to intermolecular chain transfer becomes excessive with deleterious effects on the physical properties. Continuous processes allow better control of the polymerization.