Low Molecular Antistatic Agents – Ensuring Safety in Various Industries
Antistatic agents are important additives used in the manufacturing of plastic and other polymeric materials. They help reduce the build-up of static electricity on these surfaces by increasing their surface electrical conductivity. Low molecular weight antistatic agents are effective in providing antistatic properties without significantly altering the physical properties of the base polymer. This article discusses the types, properties and applications of low molecular weight antistatic agents.
Types of Low Molecular Weight Antistatic Agents
There are mainly two types of low molecular weight antistatic agents used - glycerol esters and alkyl sulfonic acid esters.
Glycerol Esters
Glycerol monostearate is the most commonly used glycerol ester. It has a molecular weight of about 430 g/mole. Being non-ionic in nature, glycerol monostearate is compatible with a wide range of polymers like polyethylene, polypropylene, polystyrene etc. It migrates to the surface and forms a monomolecular layer that enhances surface conductivity. Other glycerol esters like glycerol monooleate are also used.
Alkyl Sulfonic Acid Esters
Esters of alkyl sulfonic acids like sorbitan monolaurate are effective Anionic Antistatic Agents. They have surface active properties and a molecular weight between 400-600 g/mole. Alkyl sulfonic acid esters are generally more effective than glycerol esters in providing antistatic characteristics. However, their compatibility is limited to non-polar polymers only.
Properties and Performance
Low molecular weight antistatic agents possess properties like:
- Low volatility - They do not evaporate easily from the polymer surface.
- Thermal stability - Remain effective over a wide temperature range.
- Surface activity - Possess hydrophilic and hydrophobic groups to migrate to surfaces.
- Compatibility - Compatible with several polyolefins and thermoplastics.
- Conductivity - Enhance surface and bulk conductivity at low additive levels(<5%).
- Processability - Do not interfere significantly with polymer processing techniques.
Being non-bleeding and having a molecular weight less than 1000, low molecular antistatic agents provide durable antistatic effects without jeopardizing mechanical properties, aesthetics or functionality of parts.
Applications
Due to their effectiveness and compatibility, low molecular antistatic agents are used in several applications:
Plastic Packaging Films
They are blended with polyethylene and polypropylene films used extensively in food, pharmaceutical and electronic device packaging. This prevents electrostatic charges from accumulating that can damage the products inside.
Injection Molding
Injection molded parts like CD and DVD cases, electrical component housings used them to enable smooth ejection of final parts from molds without adhesion or migration issues.
Blow Molding
Industrial containers, bottles etc. produced using blow molding contain these additives. This protects the fluid inside from getting ignited due to static sparks.
Fibers and Textiles
Synthetic fibers and textiles made from nylon and polyester utilize low molecular antistatics. This allows easier fabrication processes like spinning, weaving, knitting without facing problems arising from static build-up.
Calendaring of Plastics
The calendaring or rolling of plastic sheets requires proper antistatic protection. Low level additives provide requisite conductivity without altering the finished product properties.
To summarize, low molecular weight antistatic agents are a class of effective antistatic additives having specialized properties. Widely compatible and durable in performance, they facilitate smooth fabrication of a variety of plastic and polymeric items. Their usage helps save costs and improve productivity by reducing downtimes and waste generation associated with electrostatic issues. Proper selection of type and concentration during formulation results in high quality finished articles with in-built antistatic characteristics.
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