Material Compatibility and Surface Adaptability
Release agents must have good compatibility with PE melt to avoid surface defects such as pits, haze or precipitates on products, which would affect appearance and subsequent processing performance. For PE products requiring painting, bonding or printing, release agents should also have low residue characteristics to prevent residual substances from hindering the adhesion of subsequent processes.
Release Efficiency and Durability
In mass production scenarios, release agents must ensure the effective release times after a single application to reduce downtime for reapplication. Industry-recognized high-quality release agents can achieve 50 to 100 effective releases per single spray, which not only meets the needs of high-efficiency production but also reduces the overall use cost of release agents.
Mold and Environmental Friendliness
Release agents must not cause corrosion or damage to the mold surface. Especially for highly polished mold cavities, they should have good lubricity rather than abrasiveness. Meanwhile, with the improvement of environmental protection production requirements, release agents must comply with low VOCs emission standards to avoid harmful gas emissions during use and ensure the safety of the production environment.
Internal Release Agents
Internal release agents achieve the release effect by being added to PE raw materials. Common types include stearates and fatty acid esters, with a recommended addition amount of 0.1% to 0.5% of the raw material mass, an industry-recognized safe and effective range. Their advantage lies in uniform release without manual reapplication, making them suitable for mass-produced standard parts such as PE pipes and bottle caps. However, they have a certain impact on product surface performance and are not suitable for products with extremely high appearance requirements or those requiring subsequent processing.
External Release Agents
External release agents function by being sprayed or brushed onto the mold surface, and are divided into solvent-based and water-based types. Solvent-based external release agents offer high release efficiency and fast film formation, suitable for short-term production of complex cavity parts, but their high VOCs emissions have gradually been restricted by environmental policies. Water-based external release agents use water as the dispersion medium, featuring good environmental friendliness and low residue. They are the mainstream development direction of the industry, applicable to most PE product production, especially scenarios with high requirements for the environment and product surface quality.
New Silicone-Free Release Agents
Silicone-free release agents are upgraded products in recent years, solving the problem that residues of traditional silicone-based release agents affect subsequent painting and bonding. Their release performance is comparable to that of silicone-based products, and they have better compatibility, making them suitable for high-end PE products requiring secondary processing such as automotive interior parts and home appliance shells, in line with the production trend of high-end products.
Selection by Product and Process
For standard PE parts with simple structure and no need for subsequent processing, internal release agents or conventional water-based external release agents can be selected. For complex cavity parts or thin-walled parts, water-based external release agents with high release efficiency are preferred, and a combination of internal and external release agents can be used if necessary. For high-end products requiring painting or bonding, silicone-free release agents must be selected to avoid residue affecting adhesion.
Balancing Environmental Protection and Production Efficiency
With the increasingly strict environmental policies, priority should be given to water-based or silicone-free release agents, and solvent-based products with high VOCs should be gradually phased out. Meanwhile, attention should be paid to the durability of release agents, and products with high effective release times per single application should be selected to improve production efficiency and reduce comprehensive costs by reducing the number of reapplications.
Optimizing Effects with Mold Maintenance
The application effect of release agents is closely related to mold conditions. Mold cavity surfaces should be polished to below Ra 0.2 μm, and carbon deposits and residues on the cavity surface should be cleaned regularly to avoid mold sticking caused by rough or contaminated mold surfaces. In addition, reasonable mold temperature control can also help improve the release effect. The mold temperature for PE injection molding is usually controlled at 20 to 40 °C, which can reduce the adsorption between the melt and the mold.
