PVC is a polymer with very useful properties and for processing it requires the addition of a stabilizer system, together with lubricants, of both internal and external.
PVC compounds are formulated for rigid and flexible applications and are adapted to a number of processing methods covering extrusion, injection and blow molding, as well as calendering. These techniques encompass the use of PVC in the fabrication of pipes, profiles, bottle, sheet and jacketing for wires and cables.
The MARCUS polyethylenes, both homopolymer and oxidized grades, are highly efficient lubricants for PVC compounds and each family has a specific function. The homopolymer grades (200, 300, 500 & 4040), being completely non polar and composed mainly of linear chains, are essentially incompatible with PVC. Consequently, they possess a very strong external lubricating power and have a pronounced influence upon inter-particle and melt-wall lubrication, and hence, prolong gelation time. Their efficiency is such that only small dosage rates are needed, which vary from 0.1% to 1.0%. The addition level is dependent upon the stabilizer system in play, the design parameters of the specific processing equipment, and the presence of other lubricants. Frequently, the inclusion of a high performance MARCUS homopolymer has a synergistic influence on the other external lubricants which can lead to an overall lower lubricant concentration being required, resulting in consequent cost savings.
The MARCUS oxidized grades have functional polar groups (carboxyl, hydroxyl, and ester), and although external in action also have a distinct internal lubricating action. Thus, they act to reduce the gelation time and are, like the homopolymers, effective at low incorporation levels, between 0.1 – 0.5%. They are of outstanding value in tin and calcium / zinc stabilized systems and find use in rigid and flexible clear articles. Frequently these oxidized polyethylenes are employed to their best effect in combination with the homopolymers to obtain the desired compound behavior in increasing or decreasing the gelation time to fit the design parameters of the processing equipment.
Although the levels of incorporation of wax are small, there is an accentuation of the high efficiency of lubrication as one of the virtues of wax. This aspect along with other key advantages highlight:
- Highly efficient lubricants by all conversion means.
- Excellent filler and modifier dispersants.
- Superb release agents.
- Significantly improve surface finish.
- Ease and speed processing rates.