Synthetic Polyester Wax in PA and PET: What to Consider When Switching from Montan Wax

Core Engineering Mechanism & Formulation Overview

PA (polyamide) and PET are processed at high temperatures, which puts tighter demands on a lubricant's heat resistance, volatility and compatibility with polar resins than commodity plastics do. Montan waxes, such as montan ester waxes and partially saponified montan ester waxes, have long been used in these resins. More recently, considerations such as raw material source, supply and batch consistency have led more processors to look at synthetic polyester waxes. RL-691A is produced at our own production bases and can be customized to application needs.

Changing wax is not a simple one-to-one swap. This article covers what montan wax does in PA and PET, common reasons for switching, and four performance areas to consider.

What Does Montan Wax Do in PA and PET?

Montan wax comes from lignite and, after refining and esterification or saponification, contains long-chain ester and acid structures whose polarity suits PA and PET reasonably well. In these resins it is mainly used for:

• Mold release: It forms a release layer at the mold surface, reducing sticking and ejection damage. Montan esters act mainly as external lubricants.
• Melt flow: It helps processing flow to some extent and lowers load during extrusion and injection molding.
• Appearance of glass-fiber reinforced parts: The lubricant system is one factor in surface appearance, alongside fiber wetting, mold temperature and screw design.

Common Reasons for Switching

Processors usually consider switching for these reasons:

• Raw material source and supply: A wish for a lubricant option with more diversified sourcing.
• Batch consistency: Synthetic routes are generally easier to control in composition, though actual performance varies by grade and producer.
• Color requirements: Light-colored and natural parts are more sensitive to lubricant color and heat discoloration.
• Overall cost: Optimizing the lubricant system cost while meeting performance needs.

About RLWAX RL-691A

RL-691A is a synthetic polyester wax in the RLWAX range. It is a powder, positioned as a lubricant for engineering plastics and corresponds to the montan wax E class.

Typical values. Please refer to the TDS for specifications.

Our Strengths

• Built for high-temperature processing: RL-691A is designed for high-temperature processing of polar engineering plastics such as PA and PET, with attention to thermal stability, volatility and exudation.
• Wetting and dispersion: In formulations with glass fiber, flame-retardant powders or color pigments, the lubricant system is one factor in filler dispersion and part surface. RL-691A can help improve filler wetting, reduce floating fibers and improve surface finish.
• Customization: We can develop grades tailored to your resin system, equipment, molding process and performance targets, and keep adjusting with you based on your trial feedback.

Four Performance Areas to Consider

• Mold release: Smooth, stable release in continuous production directly affects part appearance and efficiency.
• Melt flow: This affects thin-wall filling and processing load, especially in high glass-fiber formulations.
• Appearance and color: Surface gloss, floating fibers, any exudation, and color change in light-colored parts.
• Thermal stability: In high-temperature processing, more volatiles mean smoke and fouled mold vents, which disrupt continuous production.

These four areas are interrelated. Which matters most depends on your resin system, part design and processing conditions.

How We Support Your Selection

Our technical team provides selection advice and starting-dosage references based on your resin system and current lubricant system, and keeps adjusting with you based on your trial feedback. We can also develop grades tailored to your needs.

To speed up our recommendation, please share:

1. Base resin and reinforcement: e.g., PA6, PA66, glass-fiber reinforced PA, PET or PBT
2. Current lubricant system and dosage
3. Processing method and temperature range: compounding, injection molding, and part design
4. Main concern: mold release, floating fibers, color, or cost and supply

TDS and SDS are available. For samples and custom evaluation, please contact us →

Frequently Asked Questions (FAQ)

Q1: Can RL-691A directly replace montan wax?

Resins, parts and processes differ, so we do not suggest treating it as a direct replacement. We provide selection advice and starting-dosage references based on your current system, and keep adjusting based on your trial feedback.

Q2: How do synthetic polyester wax and montan wax differ?

Montan wax comes from natural lignite, so its composition reflects the raw material. Synthetic polyester wax is made by a synthetic process, so its composition is generally easier to control. Dropping point, acid value and other indicators vary by grade, so please check the TDS of the specific grade.

Q3: Does adding a lubricant affect mechanical properties?

Both the type and dosage of a lubricant can affect mechanical properties to some degree, depending on the resin system. We take this into account in our selection advice.