How to Produce Lighter Weight PVC Soles?

To produce lighter PVC soles, we can start from three aspects: material formula, production process and structural design. The following are specific methods and precautions:

I. Material formula optimization

1. Adding foaming agent

Chemical foaming agent: such as AC foaming agent (azodicarbonamide), decomposes at processing temperature to produce gas and form a microporous structure. The amount of foaming agent (usually 0.5%-2%) and processing temperature (160-200℃) need to be adjusted to control the pore size and uniformity.

Physical foaming agent: such as supercritical CO₂injection, which is environmentally friendly and has finer pores, but has higher requirements for equipment.

2. Lightweight filler replacement

Replacing traditional calcium carbonate (density 2.7 g/cm³) with hollow glass microspheres (density 0.1-0.6 g/cm³) or nano-kaolin can reduce weight by 20-30%. Pay attention to the filling amount (10-30%) to avoid affecting strength.

3. High-efficiency plasticizer

Select dioctyl phthalate (DOP) or environmentally friendly plasticizers (such as citrate esters) and reduce the dosage (usually 30-50 phr) to reduce density while maintaining flexibility.

2. Production process improvement

1. Foaming process control

Molding foaming: adjust the molding pressure (5-15 MPa) and cooling rate to ensure uniform pores.

Extrusion microfoaming: achieve continuous foaming through screw design (such as lengthening the L/D ratio) and temperature zoning control.

2. Blending modification

Add EVA (5-15%) or TPU (3-10%) to improve elasticity and reduce PVC dosage while maintaining performance. Compatibility needs to be tested (such as torque rheometer).

3. Structural design innovation

1. Bionic structure

Design honeycomb or grid soles, and achieve local weight reduction through mold carving (weight reduction can reach 15-25%).

3D printing technology customizes hollow structures, but the cost is high.

2. Layered design

The sole is divided into inner and outer layers: the outer layer is dense and wear-resistant, and the inner layer is foamed and lightweight, taking into account functionality and weight reduction.

4. Notes

1. Performance test: It is necessary to test the wear resistance (such as Taber test), tear strength (ASTM D624) and resilience after weight reduction.

2. Cost control: Lightweight materials (such as hollow microspheres) are expensive and need to balance economic efficiency.

3. Environmental compliance: Choose non-toxic foaming agents (such as ammonia-free formulas) and plasticizers that meet RoHS standards.

5. Recommended solution

Low-cost solution: AC foaming agent (1%) + partial replacement of calcium carbonate with hollow microspheres (15%) + compression foaming process.

High-performance solution: supercritical CO₂ foaming + TPU blending (10%) + honeycomb structure mold design.

It is recommended to conduct a small trial first, and gradually optimize the formula and process parameters to ensure weight reduction while meeting the functional requirements of the sole.

INPVC offers one-stop solution for your manufacture. If you have needs want to make improvements on your product, consult us right now!