Metallocene polyethylene melting point

Polypropylene (PP) and polyethylene (PE) fibres float in water, they are not soluble in cold concentrated sulphuric acid but soluble in boiling perchloroethylene. They are also easily recognizable and distinguishable by their melting points PE 124-138 °C (occasionally up to 155 °C) (low density PE 105-129 °C), PP = 160-175 °C (if based on metallocene catalysis 15-20° C lower). 

Figure 6.15 DSC trace for metallocene polyethylene indicating multiple melting points.

The incorporation of the macromer was investigated and calculated by NMR measurements. The maximum incorporation rate was 0.52 mol%. This means that about 59.7 wt% of the polymer is composed of macromer units and, on average, every 400th carbon atom of the backbone chain is branched. The melting point of the long-chain branched polyethylene decreases from 136 to 12 PC, and the zero shear-rate viscosity increases from 142 to 280 Pa s. Such long-chain branched copolymer can be produced much more easily by metallocene/MAO catalysts than by Ziegler-Natta catalysts. 

Figure 5.9 shows the creep and recoverable compliances of a metallocene, linear, low-density polyethylene at 150 °C [36]. This polymer has a polydispersity index (Af, /M ) of about two. The data shown start in the transition from the plateau to the terminal zones, and the last few points are in the terminal zone, which corresponds here to steady flow. Note that the experiment had to be continued for about 2.5 hours to reach steady state, where J t) = /° +tlr)g and /j (f) = /°. (/r is the recoverable compliance defined in Eq. 4.26.) It is of interest to compare the creep compliance of an entangled polymer melt with that of a cross-linked elastomer. The latter cannot flow, so at long times /(t) approaches a constant value, the equilibrium compliance, /°. 

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