SPC Flooring Raw Material Formula: PVC, CaCO3, Stabilizers & Additives

An SPC flooring raw material formula combines PVC resin, calcium carbonate, heat stabilizers, lubricants, processing aids and, where required, impact modifiers. Each ingredient affects how the compound processes and how the finished core performs.

For manufacturers, the challenge is balancing material cost with reliable extrusion, dimensional stability and strong click-lock edges.

A formula that produces a smooth sheet may still perform poorly after profiling or heat exposure. Successful formulation therefore requires testing the finished flooring, not simply checking whether the material passes through the extruder.

This guide explains the main SPC core ingredients, how to read formulation ratios, and how to evaluate a recipe before commercial production.

What Materials Are Used in SPC Flooring?

SPC stands for stone plastic composite, also commonly called stone polymer composite. Its rigid core consists primarily of mineral filler held within a PVC matrix.

The core formula does not describe the entire finished plank. Decorative film, wear layer, surface coating and attached backing are separate materials with their own specifications.

Understanding SPC Formula Ratios: PHR vs Weight Percentage

Before comparing recipes, establish the calculation basis.

PVC formulations often use phr, meaning parts by weight per hundred parts of resin.

If PVC is listed as 100 phr and calcium carbonate as 300 phr, the recipe contains three parts calcium carbonate for every one part PVC by weight.

It does not mean the finished compound contains 300% calcium carbonate.

How to Convert PHR into Weight Percentage

Use this calculation:

Ingredient weight percentage = Ingredient phr ÷ Total formulation phr × 100

For a simplified blend containing only 100 parts PVC and 300 parts calcium carbonate:

• PVC represents 25% of the blend.

• Calcium carbonate represents 75%.

Adding stabilizers and other ingredients changes both percentages.

When comparing supplier recipes, ask whether the figures refer to resin-based phr, total compound weight percentage, or kilograms per batch.

An Illustrative SPC Flooring Raw Material Formula

Published SPC recipes vary. For example, Repolyfine provides a reference formulation using a 1:3 PVC-to-calcium-carbonate mass ratio, alongside stabilizers and processing additives. This is one formulation approach, not a universal specification.

The following example demonstrates formulation accounting and batch conversion.

It is an illustrative calculation, not a validated production recipe or an additive dosage recommendation. Actual quantities must be developed with the material suppliers and checked on the intended production line.

This example assumes that any lubrication already supplied by the stabilizer package has been considered before defining the separately added lubricant quantity.

Commercial additive packages differ in composition. Replacing one product with another at the same weight may change processing behavior substantially.

Why a Formula Table Is Only the Starting Point

A usable production specification also identifies:

• The exact supplier and grade of each ingredient.

• Permitted raw material variation.

• Weighing tolerances and mixing sequence.

• Extrusion and downstream processing conditions.

• Finished-product acceptance criteria.

Without these details, two factories can use the same nominal ratios and obtain different results.

PVC Resin: Selecting the Polymer Matrix

PVC provides the matrix that binds the mineral-rich core together.

For purchasing, a resin designation alone is insufficient. Request the technical data sheet and agree on the properties that must remain consistent between deliveries.

What Should Buyers Check?

A resin evaluation should cover its K-value or viscosity specification, bulk density, particle characteristics, volatile content and contamination controls.

The practical question is whether the selected grade produces repeatable fusion and acceptable mechanical performance at the intended output.

Compare candidate resins under controlled conditions. Changing the resin, filler and lubricant simultaneously makes it difficult to identify which change caused an improvement or defect.

Calcium Carbonate: More Than a Low-Cost Filler

Calcium carbonate is a major component of the SPC core, so filler consistency deserves close attention.

Mineral suppliers distinguish between grades for different vinyl flooring systems. Omya, for example, identifies fine and treated calcium carbonate grades for rigid LVT applications with high filler loading. 

Particle Size and Surface Treatment

Do not purchase calcium carbonate on a mesh description alone.

Ask suppliers for:

• Median particle size, such as D50.

• Coarse-particle information, such as D97.

• Moisture specification and test method.

• Purity and impurity information.

• Surface-treatment type and consistency.

• Batch-specific certificates of analysis.

These details create a more useful purchasing specification than “fine calcium powder.”

Is a Higher Calcium Carbonate Ratio Better?

A higher mineral loading may lower compound cost per kilogram, but that is only one part of the decision.

Evaluate the proposed change against click-lock strength, impact performance, achievable output, scrap and finished core density. Reject a cost reduction that prevents the product from meeting its intended specification.

The best ratio is the one that delivers the required flooring consistently at an acceptable cost.

Heat Stabilizers: Protecting PVC During Processing

PVC requires heat stabilization during processing. Stabilizer selection depends on the processing method and the finished-product requirements.

Baerlocher also explains that stabilizer one-packs can combine stabilization, lubrication and other additive functions. Consequently, the weight of a commercial package does not represent its active stabilizer content alone.

Calcium-Zinc Stabilizer Packages

When evaluating a calcium-zinc package, ask the supplier to confirm:

• Its intended application and recommended dosage basis.

• Whether it includes lubricants or other functional ingredients.

• Its compatibility with the selected resin and filler.

• The evidence supporting its processing performance.

Test the package during a sustained production run. Initial sheet appearance alone does not establish whether the system will remain stable over time.

Avoid Double-Counting Additives

If a one-pack already contains lubrication, adding the full lubricant quantity from an unrelated recipe can upset the balance.

Build the complete formulation around the selected package.

Lubricants: Balancing Melt Flow and Metal Release

Internal lubricants primarily reduce friction within the PVC melt. External lubricants primarily reduce adhesion between PVC and metal surfaces. Some products provide both effects, so the distinction is not absolute.

Internal Lubrication

Internal lubrication helps adjust melt viscosity and flow behavior.

Evaluate it together with processing aid selection and the extrusion conditions. A lower motor load, by itself, does not establish that the board has developed adequate properties.

External Lubrication

External lubrication supports release from processing surfaces. Paraffin and polyethylene waxes are examples of materials used for this purpose.

Excessive dosage can create surface-related problems. Keep a record of all lubricant contributions, including those from the stabilizer package, rather than monitoring only separately added wax.

Processing Aids and Impact Modifiers

Processing aids and impact modifiers perform different functions, even when a particular product influences more than one property.

Acrylic Processing Aids

Acrylic processing aids can support fusion and melt strength in filled PVC systems.

Impact Modifiers

Impact modifiers help improve toughness. For flooring, evaluation should include the machined tongue-and-groove assembly, where thin sections must withstand handling and installation.

A processing aid and an impact modifier should not be assumed interchangeable.

Does SPC Flooring Need Plasticizers or Foaming Agents?

Conventional solid SPC cores are generally formulated as rigid, unfoamed PVC-mineral composites. They do not use the substantial plasticizer loading associated with flexible vinyl flooring.

The word “plasticization” in an extrusion discussion may refer to PVC fusion under heat and shear. It does not necessarily mean a plasticizer is being added.

Likewise, a recipe for a foamed PVC or WPC flooring core should not be copied directly into conventional solid SPC production. Confirm the intended core structure before comparing formulations.

Can Recycled Material Be Used in an SPC Formula?

Recycled content requires its own material specification and trial program.

Clean, traceable production scrap offers a different level of control from mixed material with unknown composition.

Account for What Regrind Already Contains

SPC regrind already contains resin, mineral filler and additives. It must therefore be included in the formulation mass balance.

For example, consider 50 kg of regrind known to contain:

These are illustrative values. Actual regrind composition must be established.

Adding regrind on top of an unchanged recipe alters the effective composition. It also introduces material with a previous processing history.

Match the Formula to the Production Line

A recipe should be qualified on the equipment that will manufacture the product.

During trials, record screw speed, motor load, melt pressure, measured melt temperature where available, output and sheet quality. Record downstream settings as well, because calendering and cooling affect the final board.

Mixing and Feeding

Create a written mixing procedure with controlled ingredient order, batch size, mixing conditions and discharge criteria.

Verify scale accuracy, particularly for low-dose additives. A weighing error in a small ingredient can be significant even when the total batch weight appears correct.

Extruder Selection

When purchasing equipment, specify the intended material system as part of the performance discussion.

Ask for output and quality to be demonstrated using a representative formula and product thickness.

For more on equipment selection, read our SPC Flooring Extruder Guide: Parallel Twin Screw vs Conical Twin Screw.

Troubleshooting SPC Core Quality

Use the following table to organize an investigation. These are checks to perform, not single-cause diagnoses.

Change one controlled variable at a time where practical. Retain samples and record the result against a baseline.

How to Calculate SPC Raw Material Cost

Start with compound cost:

Compound cost per kg = Sum of each ingredient’s weight fraction × its delivered price per kg

Then convert to the unit used to sell flooring.

Calculate Core Weight per Square Meter

For a solid core:

Core weight, kg/m² = Core density, kg/m³ × Core thickness, m

For an illustrative 4 mm core with a measured density of 2,000 kg/m³:

2,000 × 0.004 = 8 kg/m²

If the hypothetical compound cost is $0.40/kg:

8 × $0.40 = $3.20/m²

This is the theoretical core material cost only. It excludes other layers, conversion costs and losses. The figures are calculation assumptions, not current market quotations.

Compare Cost per Saleable Square Meter

A formula with a lower cost per kilogram can still be more expensive if it increases core weight, rejects or downtime.

For production comparisons, use:

Net core material cost per saleable m² = Net core material cost consumed during the period ÷ Accepted flooring area produced

Account for recovered scrap consistently so that it is not charged twice.

How to Validate a New SPC Flooring Formula

Agree on acceptance criteria before starting trials.

Step 1: Define the Finished Product

Specify core thickness, plank dimensions, click profile, layer construction and intended market requirements.

Step 2: Establish a Baseline

Use traceable raw materials and a documented formula. Record both settings and measured performance.

Step 3: Run Controlled Comparisons

Evaluate a limited number of changes with clear objectives, such as reducing edge chipping or improving output consistency.

Step 4: Test Finished Planks

Include dimensions, thermal dimensional behavior, impact performance, click-joint performance and layer adhesion where applicable.

Core formulation alone does not establish the performance of the finished flooring system.

Step 5: Confirm Repeatability

Repeat the successful formulation across additional batches and a sustained run before approving it for routine production.

Frequently Asked Questions

What Is the Main Raw Material in SPC Flooring?

The core contains primarily calcium carbonate and PVC resin, supported by stabilizers and processing additives. Calcium carbonate is often the largest ingredient by weight.

What Is the Correct PVC-to-Calcium-Carbonate Ratio?

There is no universal ratio. A 1:3 mass ratio appears in published reference recipes, but the appropriate balance depends on the materials, equipment and finished-product requirements.

Does 300 PHR Calcium Carbonate Mean 75% of the Compound?

Only in a simplified blend containing 100 parts PVC and 300 parts calcium carbonate with no other ingredients. Once additives are included, the calcium carbonate percentage is lower.

Can Two Calcium-Zinc Stabilizers Be Used at the Same Dosage?

Not automatically. Their active composition and included lubrication may differ. Follow the grade-specific guidance and validate the replacement.

Can More Filler Reduce SPC Flooring Production Cost?

It may reduce compound cost per kilogram. Confirm the effect on density, saleable output and product quality before concluding that it reduces cost per square meter.

Can One Formula Work on Every SPC Extruder?

A formulation requires qualification on the intended line. Equipment configuration and operating conditions influence its processing behavior.

Discuss Your SPC Flooring Project with Kingshine

Raw materials and equipment should be evaluated together when planning an SPC flooring factory or upgrading an existing line.

Explore Kingshine’s SPC Flooring Production Line Solution and prepare the following details for your inquiry:

• Target flooring dimensions and core thickness.

• Required output in kg/h or m²/day.

• Available PVC and calcium carbonate grades.

• Planned use of recycled material.

• Target quality requirements.

• Existing formulation or production problems, if applicable.