Process lubrication for plastic working

Plastic Processing Lubricants

Plastic processing lubricants are used to reduce friction and improve plastic processing operations, including mold release, die casting, extrusion, injection molding and blow molding. These lubricants can be used to reduce the sticking of plastics, improve or reduce surface finish or texture, reduce cycle times and protect against rust or other corrosion. They can also be used to reduce noise, increase adhesion of coating materials, aid in assembly operations and prevent plastic degradation or thermal discoloration.

Types of Plastic Processing Lubricants

Plastic processing lubricants can be divided into two main types: synthetic and mineral oil-based. Synthetic lubricants can be further subdivided into three types of polymers: polyalkylene glycols, polyalkylmethylethers and polyalkylchloroparaffins.

Polyalkylene Glycols

Polyalkylene glycols are polymers composed of a chain of repeating glycol molecules, typically formed from ethylene oxide or propylene oxide. These polymers are used in a variety of lubricants, including lubricants for extrusion and injection molding, mold release, and die casting. They are typically non-toxic and have a low vapor pressure, making them an excellent choice for plastic processing applications.

Polyalkylmethylethers

Polyalkylmethylethers are synthetic polymers composed of a chain of repeating ether molecules, typically formed from butoxy, propoxy, or isopropoxy monomers. They are moisture-resistant, non-toxic and have lower volatile organic compounds (VOCs) compared to mineral oil-based lubricants. These polymers are often used in extrusion, injection molding and die casting applications.

Polyalkylchloroparaffins

Polyalkylchloroparaffins are synthetic polymers composed of a chain of repeating chlorine atoms and alkyl groups, typically formed from trichloroethane or tetrachloroethylene. These polymers are used in a variety of applications, including injection molding, extrusion and diecasting. They are relatively non-toxic and non-corrosive, making them an excellent choice for many plastic processing applications.

Mineral Oil-Based Lubricants

Mineral oil-based lubricants are derived from petroleum-based sources and are typically composed of light, medium or heavy viscosity oils. These lubricants are typically used in applications where temperature extremes are encountered or longer lubricant life is required. Some formulations include additional additives to improve lubricity, oxidation stability or corrosion protection.

Conclusion

The right choice of plastic processing lubricant depends on the application. It is important to consider the types of polymers used, the process temperature, the environmental conditions and any additional additives that may be required. Synthetic polymers provide many benefits over mineral oil-based lubricants, including improved thermal stability, better lubricity and lower volatility.

In plastic processing lubrication, the purpose of using a lubricant is to reduce friction and wear, prevent welding and foreign material accumulation, and improve product surface quality. To achieve these goals, a properly selected lubricant is needed.

The most used lubricants are water-based emulsions, oils, and solid wax-resin compounds. Water-based emulsions are widely used in plastic processing because of their low viscosity, good heat stability, and non-toxicity. The water-soluble oils have good low temperature performance and good compatibility with the plastic. Solid wax-resin compounds are highly effective in reducing the friction.

The essential factors for selecting a proper lubricant for plastic processing are the type of material, the working conditions, and lubricant compatibility. The material and working temperature need to be considered during the selection process to make sure the lubricant can adequately protect the plastic from wear and tear. Additionally, the lubricant should be compatible with the plastic and not have any harmful effects on the plastic’s properties.

In addition to lubricant selection, the lubrication technique should also be optimized. Lubrication methods such as flooding, spraying, and brushing should be used to ensure that the lubricant is evenly applied on the plastic. It is also important to use the appropriate lubricant flow rate and pressure to ensure that the lubricant is uniformly applied.

Finally, the lubricant should be properly monitored and checked for signs of contamination or depletion. Frequent lubricant replacement is necessary to ensure the plastic processing operation runs smoothly and efficiently.