The use of Fischer Tropsch waxes in processing of PVC & CPVC -2

3. PE waxes Vs. F. T. waxes:

Non-polar lubricants are neither accepted by PVC nor by the oxidized metal surfaces.

Their activity is a function of their incapability to get attached to PVC or metals, their melting points, melt viscosities and volatility.

Fischer-Tropsch wax and PE wax are two types of synthetic non-polar waxes that are used in various industries.

Compared with general polyethylene wax (PE wax), Fischer-Tropsch synthetic wax differs significantly in following aspects:

3.1 Molecular weight. The molecular weight of Fischer-Tropsch wax (500-1000) is much lower than that of PE wax (2000-5000), with fewer branched chains and high crystallinity.

3.2 Fischer-Tropsch wax is a saturated direct paraffin, with no double bond, hence have a strong antioxidant ability and good weather resistance.

3.3 Viscosity of Fischer-Tropsch wax is much lower, only about 10 percent, than that of PE wax. The same lubrication effect can be achieved with only 70-80 percent of F.T. wax.

3.4 According to the need, Fischer-Tropsch process can synthesize alkanes with different chain lengths, change the molecular weight of the final product, and form a series of products.

4. F. T. Waxes Vs. Paraffin waxes:

In contrast to synthetic F. T. waxes, paraffin waxes are kind of mineral waxes derived from petroleum fractions by processes like freezing, solvent dewaxing, de-oiling and refining.

The chemical structure of paraffin wax is primarily composed of saturated normal and iso – alkanes, naphthenes, and alkyl substituted and naphthene substituted aromatic compounds.

The degree of branching has an important influence on the properties of paraffin wax.

Paraffin waxes normally consists of hydrocarbon molecules having 20-40 carbon atoms.

Commercial paraffin waxes generally have molecular weight of 360-540, much lower, as compared to 500-1000 for F. T. waxes.

Depending on the degree of branching, melting points of paraffin waxescan be 40 – 68°C, as compared to melting point of F. T. waxes 95-110°

The viscosity of F. T. waxes is much lower (10) than the viscosity of paraffin waxes (20-60). 

Only small amount of F. T. waxes can give good lubrication. Paraffin waxes have relatively poor lubricating effect.

(TO BE CONTINUED...)