Cold Top Mold: Complete Formulas, Technical Specifications | YNmold

11 Sep,2026

In a high-filler formulation system with a heavy calcium carbonate (CaCO₃) ratio as high as 75 phr (i.e., PVC : CaCO₃ = 100 : 75), the rheological properties of the material change significantly: melt viscosity increases drastically, fluidity decreases, wear on the extrusion die and calibrators accelerates, and melt fracture easily occurs.

For Cold Top / Cold Calibration Extrusion Tooling, the calibration section relies on cooling to rapidly build up outer profile wall hardness. Under a high CaCO₃ formulation, improper lubrication or plasticization can easily cause excessive internal drag resistance inside the calibrator, resulting in surface scoring, cracking, or profile plugging (jamming).

For this high filling ratio,YNmold here is a recommended basic reference formulation for high-filler PVC cold top profile/sheet extrusion (Unit: phr, parts per hundred parts of PVC resin by weight):

Basic Reference Formulation (PVC : CaCO₃ = 100 : 75)

Raw Material

Recommended Dosage (phr)

Key Function & Process Adaptation

PVC Resin (SG-5 / K-67)

100

Base resin; provides melt strength and essential mechanical properties.

Heavy Calcium Carbonate ( CaCO₃, 800-1250 mesh)

Filler to reduce cost; must be surface-treated with coupling agents or stearic acid (activated CaCO₃) to prevent agglomeration and reduce die wear

Compound Lead Salt / Ca-Zn Stabilizer

4.5 – 5.5

High filler content adsorbs stabilizer, and high shear generates significant frictional heat, requiring a higher stabilizer dosage. If using Ca-Zn, select a high-filler dedicated grade.

ACR Processing Aid (e.g., ACR-401)

1.5 – 2.0

Promotes uniform plasticization, enhances melt cohesion, and prevents melt fracture caused by high filler loading.

CPE (Chlorinated Polyethylene, 135A)

8.0 – 10.0

Impact modifier; at 75 phr filler, matrix brittleness increases, so higher CPE dosage is needed to maintain toughness and drop-hammer impact performance.

PE Wax / Oxidized Polyethylene Wax (OPE)

0.4 – 0.6

External lubricant; prevents high-viscosity melt from sticking to screw and runner, reducing drag friction entering the cold calibration unit.

Stearic Acid

0.3 – 0.5

Internal/external lubricant; works with PE wax to balance metal release and melt flowability.

Lubricating Processing Aid (e.g., ACR-175 / 318)

0.5 – 1.0

Improves metal release, reducing demolding resistance in the die channel and cold calibrator inlet.

Titanium Dioxide (R-902)

3.0 – 4.0

Weather resistance and opacity pigment (adjust based on color and indoor/outdoor specs).

Formulation Adjustments & Cold Top Extrusion Key Points

High-filler formulations generate extreme shear heat. If external lubricant (PE wax/OPE wax) is insufficient, rapid skin cooling and shrinkage upon entering the cold calibrator creates massive wall friction, leading to profile breakage or transverse surface cracking. Excessive external lubricant will cause poor plasticization or plate-out (blooming).

ACR quality must be strictly ensured. In a high-filler system, if melt strength and encapsulation capacity are insufficient, the profile surface becomes dry and brittle upon die exit, leading to vacuum chamber collapses or water ingress during cold calibration.

High-filler compounds generate high frictional heat; barrel temperatures in rear zones can be set with a clear gradient, while front zones and die temperatures must be strictly controlled to prevent thermal degradation. Die temperature is generally kept at 185℃ - 195℃ to avoid degradation in dead spots along the flow channels.

The above information is provided by YNmold and is for reference only

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