View detail
If you're running PE wood-plastic composite (WPC) extrusion lines and dealing with issues like surface blooming, die buildup, unstable output, or material degradation, the root cause often points back to one thing: inadequate or poorly matched lubrication. This page covers everything you need to know about PE WPC composite lubricant — what it is, how it works, and how to choose the right grade for your production.
A PE WPC composite lubricant is a specially formulated processing additive designed for polyethylene-based wood-plastic composite systems. Unlike standard polymer lubricants developed for PVC or pure polyolefin applications, this type of additive is engineered to handle the unique challenges of a hybrid matrix — one that combines PE resin with high loadings of wood flour, bamboo powder, or other lignocellulosic fillers, often at ratios of 50% filler or higher.
In a typical PE WPC formulation, wood flour acts as a reinforcing filler but also introduces significant processing difficulties. Wood flour is hygroscopic, thermally sensitive, and has poor compatibility with nonpolar PE. At processing temperatures between 160°C and 200°C, the melt viscosity of the composite rises sharply compared to unfilled PE, increasing shear stress throughout the extruder and die.
A wood plastic composite lubricant addresses these challenges by acting simultaneously on the melt bulk and at the polymer–metal interface. The result is lower processing temperature, reduced motor load, smoother surface finish, and longer equipment life.
The term "composite lubricant" is key. Unlike a single-component lubricant (for example, pure EBS wax or pure polyethylene wax), a composite lubricant is a pre-engineered blend of multiple functional components — each selected to address a different aspect of the process. This multi-component architecture is what gives it a broader performance window and synergistic effects that single additives cannot match.
Most formulators focus on mechanical properties, filler loading ratio, or colorant selection when optimizing a WPC compound. Lubrication is often treated as an afterthought — until something goes wrong. In practice, lubrication directly controls three critical parameters:
High wood-flour loadings dramatically increase melt viscosity and can cause non-uniform flow inside the screw channels. Insufficient lubrication leads to uneven shear distribution, localized overheating, and inconsistent output rate. A properly dosed PE WPC additive reduces apparent melt viscosity, allowing stable throughput at lower barrel temperatures. This also reduces energy consumption and thermal degradation risk for the wood component.
In unfilled PE, contact stress on metal surfaces is relatively low. In WPC, abrasive wood particles and high processing pressure combine to accelerate die lip erosion, screw flight wear, and barrel wear. External lubrication establishes a thin film between the polymer melt and the metal surface, significantly reducing friction and abrasive contact. For high-output extrusion lines, this translates directly to reduced maintenance frequency and longer tooling service life.
Surface defects in WPC profiles — including shark skin, flow marks, pitting, and weld lines — are frequently the result of poor melt flow at the die exit. Die drool (material accumulating and burning at the die lip) is another common consequence of inadequate external lubrication. A correctly balanced composite lubricant ensures the melt releases cleanly from the die at consistent speed, producing smooth, visually uniform profiles with minimal post-processing requirements.
For a technical overview of the full PE WPC processing system, see the PE Wood-Plastic Composite comprehensive technical solutions page.
Understanding the distinction between internal and external lubrication is essential when selecting or troubleshooting a WPC lubricant system. These two mechanisms operate differently and must be balanced carefully.
Internal lubricants are components that are partially or fully compatible with the PE matrix. They disperse within the melt and reduce intermolecular friction between polymer chains and between the polymer and filler particles. The effect is a reduction in melt viscosity and processing torque. Common functional types in this role include certain ester waxes and modified polyolefin waxes with controlled compatibility.
In WPC systems, internal lubrication is especially important because wood flour particles create a tortuous melt flow path. Without adequate internal lubrication, the high shear zones around wood particles can cause localized chain scission, generating degradation products that discolor the profile and weaken mechanical performance.
Too much internal lubrication, however, delays fusion and reduces the mechanical strength of the finished part, since the polymer chains don't achieve adequate entanglement.
External lubricants have low compatibility with the PE matrix. Rather than dissolving into the melt, they migrate toward the melt–metal interface during processing, where they form a thin, low-friction boundary layer. This layer performs two functions: it reduces wall friction inside the screw/barrel, improving pressure buildup efficiency, and it provides die release — allowing the melt to separate cleanly from the die lip without sticking, drooling, or smearing.
In WPC applications, external lubrication is also directly tied to anti-exudation performance. Poorly designed external lubricants can bloom to the surface of the finished profile after cooling — especially under elevated temperatures or humidity — producing a greasy, chalky, or oily appearance that is commercially unacceptable.
The products in Joysun's PE WPC composite lubricant range are formulated to balance both mechanisms within a single additive package, eliminating the complexity of managing multiple single-component additions.
A single-component lubricant such as EBS (ethylene bis-stearamide), oxidized polyethylene wax, or stearic acid can improve one aspect of WPC processability — but never all of them simultaneously. Each single lubricant has a narrow performance window. Use too little and you don't solve the problem; use slightly too much and you introduce new ones, such as plate-out, blooming, or loss of mechanical properties.
A well-designed wood plastic composite lubricant combines components with complementary activity profiles:
One component may provide strong internal viscosity reduction early in the screw, while another activates at the die zone to provide release. A third component may be specifically selected for its non-migrating character — anchoring itself in the matrix to prevent post-process surface exudation under thermal stress.
This synergistic architecture gives the composite lubricant several practical advantages over single-component approaches:
First, the processing window is wider. The composite works across a broader range of barrel temperatures and throughput rates, making it more forgiving during line speed changes or temperature fluctuations.
Second, dosage is simpler. Rather than calculating and weighing multiple separate lubricants for each batch, the compounder uses a single pre-balanced product, reducing formulation error and improving batch-to-batch consistency.
Third, anti-exudation performance is significantly better. Single external lubricants that provide good die release tend to bloom easily. The multi-component balance in a composite lubricant allows the external-acting component to be kept at a lower individual level, reducing migration tendency while maintaining adequate processing performance.
Joysun's products are tested against specific anti-exudation benchmarks — for example, H838L and H101L grade products show no exudation after 72-hour immersion in water at temperatures up to 100°C, a standard relevant to outdoor decking, marine applications, and other thermally demanding environments.
Formulators working with PE WPC extrusion encounter a recurring set of problems. The following are the most common, along with how the right PE WPC additive addresses each:
Symptoms include pressure surging, inconsistent profile dimensions, and fluctuating motor amperage. This is typically caused by uneven melt flow or intermittent slippage along the barrel wall. A composite lubricant with balanced internal/external components stabilizes the flow regime, producing consistent output without requiring constant parameter adjustments.
One of the most commercially damaging problems in WPC production. After the profile cools and is shipped, lubricant migrates to the surface, leaving a greasy or powdery residue that affects appearance and paint/coating adhesion. This is caused by lubricant components with insufficient compatibility with the PE matrix. Anti-exudation grades such as H101L, H838L, and H201L are specifically formulated with high-retention components to eliminate this issue even under thermal cycling conditions.
When material is held at processing temperature too long — due to dead zones in the die, excessive residence time, or overheating caused by high friction — thermal degradation generates black carbonized particles that contaminate the profile. Adequate internal lubrication reduces screw torque and barrel temperature, lowering the thermal load on the wood flour and eliminating the conditions that cause carbonization.
Material accumulates at the die exit, chars, and periodically breaks off onto the profile surface, causing surface defects and requiring frequent line stoppages for cleaning. This is a classic external lubrication deficiency. A properly balanced composite lubricant maintains a continuous release film at the die lip, preventing buildup.
In severe under-lubrication, material can stick to the screw surface and rotate with it rather than advancing forward — reducing output and creating erratic pressure profiles. External lubricant components resolve this by reducing adhesion between the melt and the metal screw surface.
When WPC products require flame retardancy — for building products, wall cladding, or electrical enclosures — standard lubricants can interact with halogen-free flame retardant additives, reducing their effectiveness or destabilizing the compound. H912L is a dedicated grade formulated for flame-retardant WPC systems, maintaining full lubrication performance without compromising the flame retardancy rating.
Zhejiang Joysun Advanced Material Co., Ltd., established in 2005 and operating from its manufacturing base in the Dushangang Chemical Industrial Park in Pinghu, has developed a structured range of PE WPC composite lubricants to address the full spectrum of production requirements — from premium anti-exudation grades for demanding outdoor applications to cost-optimized general-purpose grades for standard profiles.
The complete product range is detailed on the PE Wood-Plastic Composite technical solutions page. A summary of available grades is provided below:
H101L — Ultra-High Anti-Exudation Grade
Recommended dosage: 2.2–3.2%. Designed for applications where surface cleanliness is critical even under prolonged thermal exposure. Passes 72-hour water immersion tests at 70°C, 80°C, 90°C, and 100°C without surface exudation. Suitable for outdoor decking, marine WPC products, and any application with strict surface stability requirements.
H838L — Premium Anti-Exudation Grade
Recommended dosage: 2.2–3.2%. Premium performance grade with confirmed no exudation after 72-hour immersion at 100°C. Excellent all-around lubrication with a strong anti-blooming profile.
H201L — Mid-to-High-End Anti-Exudation Grade
Recommended dosage: 1.5–2.5%. Balances anti-exudation performance (passes 80°C immersion test) with a lower usage level, making it well-suited for mid-range PE WPC products where surface quality is important but extreme thermal resistance is not required.
H771L — Mid-to-Low-End General-Purpose Grade
Recommended dosage: 1.0–1.8%. High cost-performance ratio with stable basic lubrication and improved anti-exudation versus single-component alternatives. The preferred choice for cost-sensitive WPC profiles where economy and production stability need to be balanced.
H912L — Flame-Retardant Dedicated Grade
Recommended dosage: 2.0–3.0%. Specifically engineered for flame-retardant PE WPC systems. Maintains compatibility with halogen-free flame retardant packages, does not reduce LOI or fire class, and delivers superior extrusion lubrication performance in these technically demanding formulations.
In addition, POE01 (a compatibilizer, dosage 3–6%) is available as a complementary additive that improves interfacial bonding between PE or PP matrix and wood flour, resulting in better mechanical strength, toughness, and heat resistance — often used alongside the above lubricant grades in high-performance WPC formulations.
For full technical data sheets, please visit the product detail page or contact us directly.
Joysun holds ISO 9001 quality management certification, multiple national invention patents, and is recognized as a National High-Tech Enterprise and Zhejiang Province Specialized, Refined, Unique, and New SME. The company serves over 600 clients worldwide and operates a production capacity of 70,000 tons per year across its dual-factory infrastructure.
Standard PE processing lubricants are designed for unfilled or lightly filled polyethylene systems. They do not account for the dramatically increased melt viscosity, the abrasive nature of wood filler, or the anti-exudation requirements specific to WPC end-use environments. Using a generic lubricant in a WPC system typically results in poor surface quality, blooming, carbonization, or mechanical property loss.
The primary selection criteria are the anti-exudation requirement of your end product and your cost target. For outdoor, marine, or high-temperature applications where surface stability is non-negotiable, H101L or H838L are the appropriate choices. For indoor profiles or applications with moderate thermal exposure, H201L offers a good performance-to-cost balance. H771L is recommended for cost-sensitive, standard-grade WPC production where basic lubrication and reasonable anti-exudation are the main requirements.
Depending on the grade, typical usage levels range from 1.0% to 3.2% by weight of the total formulation. Dosage should be optimized based on your specific filler loading, resin grade, processing temperature, and line speed. Technical support from Joysun's R&D team is available to help determine the optimal dosage for your system.
Yes. In fact, combining a composite lubricant with a compatibilizer such as POE01 or maleic anhydride-grafted PE is standard practice in high-performance WPC formulations. The compatibilizer improves interfacial adhesion and mechanical strength, while the lubricant handles processability. These two functions do not conflict, provided the lubricant is selected to avoid interfering with the coupling reaction at the filler interface.
The standard industry test involves immersing finished WPC profile samples in water at elevated temperatures (70°C, 80°C, 90°C, 100°C) for 72 hours and then visually inspecting and wiping the surface for lubricant migration. Joysun's product specifications include immersion test pass temperatures for each grade, providing a clear benchmark for qualification.
No. H912L is specifically developed to be compatible with halogen-free flame retardant additive systems. It does not reduce the effective concentration or activity of the flame retardant, and it does not introduce elements that would compromise the flame class rating of the finished product.
This depends on the foaming agent and system design. Joysun also manufactures chemical foaming agents and can advise on lubricant–foaming agent compatibility for foamed WPC profiles. Contact the technical team for formulation-specific guidance.
Samples, technical data sheets, and formulation recommendations are available through the contact page or by emailing sale@joysunsh.com directly. Joysun provides comprehensive technical support as part of its service offering, not just raw material supply.