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Common Additives in PVC Foamed Products

创建于12.04
The world of PVC foamed products may seem like a combination of powder, screws, and molds, but the real technical core lies in those small packages of "additives." Stabilizers, lubricants, foaming agents, calcium powder... Each silently influences the board's color, density, strength, and cell structure. Too little won’t work, and too much won’t either—they form a delicate "chemical balance." Today, we’ll explore the roles and common issues of these additives in PVC foamed products.
1. Stabilizers: Guardians of Product "Anti-Aging"
The most common stabilizers in PVC foam boards are lead salt systems and calcium-zinc systems. With stricter environmental requirements, calcium-zinc stabilizers have gradually become mainstream due to their cost-effectiveness and environmental advantages.
  • Insufficiency: Yellowing, scorching, brittleness, reduced strength, low foaming rate.
  • Excess: Premature decomposition of foaming agents, gas leakage from feed/vacuum holes, crack lines or shrinkage in products.
Key tip: Use enough stabilizer, but never "overdose."
2. External Lubricants: Smoother Extrusion
Common external lubricants include paraffin wax and PE wax. Paraffin wax tends to bloom, so PE wax is generally recommended.
  • Insufficiency: Difficult temperature control in extruders, yellowing, bubbling, rough board surfaces.
  • Excess: Poor plasticization, mold fouling, white streaks or ripples on surfaces.
Trick: Slightly insufficient is better than "overly slippery."
3. Internal Lubricants: "Invisible Hands" Controlling Plasticization
Common internal lubricants include stearic acid, 60#, monoglyceride, 316#, etc.
  • Insufficiency: Poor dispersion, uneven plasticization/thickness, mold sticking.
  • Excess: Brittleness, poor heat resistance, potential conversion to external lubrication leading to imbalance.
Summary of Lubrication Balance
  • Insufficient both :Melt adhesion to walls, decomposition and yellowing.
  • Excess both : Poor plasticization, reduced strength.
  • More external, less internal : Slow plasticization, brittle products.
  • More internal, less external : Easy mold sticking, yellow lines.
4. Calcium Powder: "Invisible Skeleton" of Cell Structure
1200-mesh light calcium carbonate is commonly used in foamed products. However, it is highly sensitive to moisture—moisture absorption easily causes bubbles, crazing, and surface discoloration.
  • Too large particle size: Uneven mixing, slow plasticization.
  • Too small particle size: Easy agglomeration.
  • Insufficiency: Few cells, high density.
  • Excess: Reduced melt strength, cell rupture on cross-sections.
Remember: Calcium powder is not just a "filler" but the "shaping core" of cells.
5. Foaming Regulators: Key to Uniform Cells
Foaming regulators are mostly high-molecular-weight acrylate-based additives. Choose different types for different products:
  • Wood-plastic products → Fast plasticization type.
  • Cabinet boards → Slow plasticization, high melt strength type.
  • Insufficiency: Poor melt strength, uneven cells, rough cross-sections.
  • Excess: Overly strong melt, difficult bubble expansion, increased density.
6. Foaming Agents: Soul of "Lightweight" Boards
The most commonly used are AC yellow foaming agent and NC white foaming agent. AC is exothermic and prone to yellowing; NC is endothermic and odorless. They are usually used in combination.
  • Insufficiency: Few cells, high density.
  • Excess: Reduced melt strength, cell collapse on cross-sections, even increased density.
  • More yellow than white: Large, round cells with unsatisfactory cross-sections.
Final Note: No Universal Formula—Only Balance
Accurate formulation ensures smooth production; unbalanced ratios lead to problems. The secret of PVC foaming formulations ultimately lies in the "art of coordination." Only through repeated testing to find the optimal balance between stabilizers, lubricants, calcium powder, and foaming agents can we achieve stronger melt, more stable cells, and smoother production—truly realizing stable efficiency, long-lasting operation, and outstanding products.
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