Plastic shrinkage during processing is a common issue in injection molding, extrusion, or thermal forming. When plastic changes from a molten to a solid state, the volume decreases, leading to warpage and deformation. This affects dimensional accuracy and reduces both product quality and aesthetics. For many years, additives have been researched and applied to overcome this issue, providing effective and sustainable solutions for the plastics industry.
CAUSES OF PLASTIC SHRINKAGE DURING PROCESSING
The main causes of shrinkage come from both material properties and processing conditions. The volume of semi-crystalline plastics such as PP, PA, and POM changes significantly during crystallization, resulting in higher shrinkage compared to amorphous plastics. In addition, uneven mold temperature also causes non-uniform shrinkage, leading to warpage or cracking. When mold filling and injection pressure are not optimized, the plastic cannot compensate for volume loss, causing voids and deformation. Moreover, each plastic type has its own shrinkage rate, ranging from 0.2% to 2.5%. Manufacturers must therefore calculate shrinkage compensation when designing molds.
Shrinkage rates of common plastics
Different plastics have different shrinkage levels, which greatly affect material selection. ABS has a shrinkage rate of 0.4 – 0.7%, relatively stable and suitable for precision parts. PP has a higher rate of 1.0 – 2.5%, so additives or reinforcements are often required to reduce shrinkage. PA66 ranges from 1.0 – 2.0%, still requiring careful control of molding conditions. POM often shows the highest shrinkage, 1.5 – 2.5%, making it challenging for technical parts production. Meanwhile, PMMA has a low shrinkage rate of 0.2 – 0.6%, ideal for transparent products or parts requiring fine surfaces.
SOLUTIONS FROM ANTI-SHRINKAGE ADDITIVES
Reinforcing Fillers
Reinforcing fillers such as glass fiber, talc, CaCO₃, or mica help reduce shrinkage by increasing volumetric stability. Inorganic particles are dispersed in the polymer matrix, preventing chains from shrinking excessively when cooling. Commonly applied in PP, PA, and PBT for electronic housings, automotive parts, and household products. For example, adding 20% talc to PP can reduce shrinkage from 1.5% to below 0.5%, keeping products in better shape.
Explore authentic Talc products officially distributed by Vichem:
Nucleating Agents
Nucleating agents control the crystallization process, ensuring uniform and stable crystal formation. Additives such as sorbitol, sodium benzoate, or phosphate salts are commonly used in PP. They increase nucleation density, allowing polymers to crystallize faster and more evenly, reducing warpage and deformation. As a result, PP molded products, bottles, or thin packaging achieve high accuracy and smooth surfaces.
Processing Aids
This group of additives improves the flowability of plastics inside molds and reduces friction during injection molding. Common examples include silicone masterbatch, ester waxes, and fluoropolymer aids. With their use, melt flow becomes more stable, minimizing shrinkage or distortion at edges and corners. Processing aids are widely applied in PVC, PE, and LDPE for pipes, sheets, and films. They also facilitate mold release, extend mold life, and save energy.
Explore authentic processing aids officially distributed by Vichem:
Dimensional Stabilizers
Dimensional stabilizers such as PPO or blend modifiers form stable network structures within the plastic matrix. They help products retain their shape after cooling, reducing warpage or long-term deformation. These additives are used in high-performance engineering plastics such as PBT and PC/ABS for electronics, precision parts, and industrial equipment. As a result, products maintain long-term reliability and meet strict technical standards.
PRACTICAL APPLICATIONS OF ANTI-SHRINKAGE ADDITIVES
Anti-shrinkage additives are widely applied across many plastic industries. In the automotive sector, they ensure dimensional accuracy for housings, dashboards, and technical parts. In electronics, they maintain dimensional stability, reducing warpage risks that affect assembly. Packaging requires smooth, uniform, and aesthetic surfaces, which benefit greatly from these additives.
For transparent plastics such as PMMA or PC, combining nucleating agents improves clarity and dimensional stability. In practice, additives not only reduce rework costs but also improve productivity and product quality, creating competitive advantages for manufacturers.
VICHEM – AUTHORIZED DISTRIBUTOR OF CERTIFIED CHEMICAL ADDITIVES IN VIETNAM
Vichem is an authorized distributor of chemical additives, providing full documentation in compliance with Vietnamese regulations. We not only deliver high-quality products but also offer world-class after-sales services. Our services include:
- Technical consulting: Supporting customers in selecting suitable products for their applications.
- Color matching tests: Conducted by our expert team to ensure accurate results for product design.
- Application support: Assisting customers in integrating additives into production lines for optimal performance.
For more details about our products, please contact us via the following channels:
📞 Hotline: 08 1790 1790
📧 Email: contact@vichem.vn
🔎 LinkedIn: Vichem JSC
🌐 Website: www.vichem.vn
📌 Facebook: Vichem JSC
