Introduction
Lubricants are essential additives in plastic processing. They help reduce friction between polymer chains and processing equipment, improving processing efficiency, melt flow, and surface quality of finished products.
Plastic lubricants are generally classified into several categories, including:
- Fatty acids
- Fatty acid amide lubricants
- Hydrocarbon lubricants
- Fatty acid ester lubricants
Each type provides different lubrication effects depending on the polymer system and processing conditions.
1. Fatty Acid Lubricants
Fatty acids are widely used lubricants in PVC processing.
Stearic Acid
Stearic acid is one of the most common fatty acid lubricants.
Functions:
- Acts as an internal lubricant at low temperatures
- Functions as an external lubricant at higher temperatures
It is widely used in PVC formulations to improve melt flow and reduce friction during processing.
2. Fatty Acid Amide Lubricants
Fatty acid amides are widely used because they provide excellent lubrication, anti-adhesion, and anti-static properties.
2.1 Stearamide (Stearic Acid Amide)
Stearamide offers excellent external lubrication performance.
Characteristics:
- Good transparency
- Good dispersibility
- Improves product gloss
- Excellent electrical insulation properties
- Non-toxic
Applications:
- PVC processing lubricant
- PS and UF resin processing aid
- Polyolefin smoothing and anti-blocking agent
Typical dosage:
0.1%–2.0%
2.2 Ethylene Bis-Stearamide (EBS)
EBS is widely used as a smoothing agent, anti-blocking agent, and external lubricant.
Characteristics:
- Non-toxic
- Excellent dispersibility
- Good anti-static properties
Applications:
- PE
- PP
- PS
- ABS resins
Typical dosage:
0.2%–2.0%
2.3 Oleamide
Oleamide functions as a smoothing and anti-adhesion agent.
Applications:
- PE
- PP
- PA plastics
Characteristics:
- Improves processing and forming performance
- Provides anti-static properties
- Reduces dust adhesion on product surfaces
In PVC processing, it can also function as a good internal lubricant.
2.4 Butyl Stearate
Butyl stearate acts mainly as an internal lubricant for resin processing.
Although it has limited compatibility with PVC, it is still useful in:
- PVC transparent sheet extrusion
- Injection molding
- Calendering processes
Typical dosage:
0.5%–1.0%
2.5 Glycerol Trihydroxystearate
This lubricant can be used in several polymers.
Applications:
- PVC
- ABS
- MBS
- Synthetic rubber
It can also act as a mold release agent.
Typical dosage:
0.25%–1.5%
3. Hydrocarbon Lubricants
Hydrocarbon lubricants are commonly used as external lubricants in plastic processing.
3.1 Microcrystalline Paraffin
Microcrystalline paraffin provides:
- Good thermal stability
- Better lubricity compared to regular paraffin wax
However, it may reduce the PVC gelation rate, so it is usually used in combination with butyl stearate or high-melting fatty acids.
Typical dosage:
0.1%–0.2%
3.2 Solid Paraffin Wax
Solid paraffin wax functions mainly as an external lubricant.
Advantages:
- Improves product surface gloss
Limitations:
- Poor compatibility and dispersibility
- Lower thermal stability
Applications:
- PVC
- PE
- PP
- PS
- ABS
- PBT
- PET
- Cellulose-based plastics
3.3 Polyethylene Wax (PE Wax)
Polyethylene wax provides excellent mid- and late-stage lubrication during processing.
Functions:
- Anti-adhesion agent
- Pigment dispersant in color masterbatch production
- Lubricant and mold release agent
Applications:
- PVC-U processing
- PE, PP, ABS, PET, PBT plastic molding
Typical dosage:
0.1%–0.5%
3.4 Oxidized Polyethylene Wax (OPE Wax)
OPE wax provides both internal and external lubrication.
Advantages:
- Improves product transparency
- Enhances surface gloss
- Good compatibility with many polymers
Applications:
- PVC
- PE
- PP
- ABS
- PET
- PBT
Typical dosage:
0.1%–1.0%
3.5 Fischer–Tropsch Wax (FT Wax)
FT wax is mainly used as:
- External lubricant
- Dispersing agent
It is widely used in:
- PVC processing
- Color masterbatch production
4. Fatty Acid Ester Lubricants
Fatty acid ester lubricants are widely used in transparent PVC formulations, particularly for films.
Common examples include:
- G60 lubricant
- G70 lubricant
- Glycerol Monostearate (GMS)
- Diglycerol Monostearate (DGM)
These lubricants help improve:
- Melt flow
- Surface gloss
- Processing stability
They are especially suitable for transparent PVC film applications.
Conclusion
Lubricants are critical additives in plastic processing, particularly for PVC formulations. Different types of lubricants—such as fatty acids, amide lubricants, hydrocarbon waxes, and fatty acid esters—provide different functions in controlling friction, improving melt flow, and enhancing product appearance.
Proper selection and combination of lubricants can significantly improve:
- Processing efficiency
- Product surface quality
- Mechanical performance
- Equipment cleanliness and stability
This makes lubricant optimization an important factor in high-quality PVC production.
