TPU And PVC Blending Modification (Part I)

Thermoplastic polyurethane (TPU) can be effectively blended with many polymers, among which polyvinyl chloride (PVC) has been extensively studied. Blending TPU with PVC can significantly reduce production costs and improve TPU’s flame retardancy. While PVC’s biggest drawbacks are its poor heat stability and limited low-temperature elasticity, blending with TPU helps overcome these limitations, enabling complementary property enhancement between the two materials.

Benefits of Blending TPU with PVC

Blending PVC into TPU not only lowers costs but also provides multiple performance improvements:

• Adjusts the overall hardness of the blend.

• Enhances TPU’s processability and water resistance.

• Improves flame retardancy, heat resistance, and weather resistance.

• Reduces the coefficient of friction.

For instance, TPU/PVC synthetic leather benefits from TPU’s clean surface finish, resistance to acids, alkalis, and solvents, and its natural leather-like appearance, combined with PVC’s lower cost advantage.

Why TPU and PVC Are Compatible

TPU and PVC exhibit good compatibility due to their similar solubility parameters and polar nature. Both are polar polymers, and their molecular structures allow interactions:

• Polar chlorine atoms in PVC can form hydrogen bonds with the amino hydrogen atoms in TPU chains, enhancing blend compatibility.

• The degree of compatibility is also influenced by TPU’s molecular structure and the polymerization degree of PVC.

Effect of TPU Type on Blend Performance

Research shows that:

• Polyester-based TPU generally achieves better compatibility with PVC, often forming blends with a single glass transition temperature (Tg).

• Polyether-based TPU tends to be less compatible with PVC during melt blending, typically showing two Tg values.

Blends using polyester TPU outperform those with polyether TPU in terms of tensile strength and elongation at break. This difference is likely because ester bonds in polyester TPU interact more strongly with PVC compared to ether bonds.

Influence of TPU Hard/Soft Segment Ratio

The compatibility of TPU and PVC is also affected by the hard/soft segment ratio in TPU:

• Lower hard segment content in TPU improves blend compatibility.

• The type of soft segment also matters. For example, TPU containing polycaprolactone diol (PCL) as the soft segment at content levels of 40%, 60%, and 80% blends well with PVC, while a 20% content does not.

Additionally, high-polymerization-degree PVC (HPVC) blends less effectively with TPU than medium-polymerization PVC. Hydrogen-like bonding occurs between TPU’s amino groups (–NH–) and PVC’s chlorine atoms (–Cl), supporting compatibility.

Importantly, the best mechanical properties do not always occur in fully compatible blends. Blending at temperatures where TPU’s hard segments partially melt can yield partially compatible blends with superior mechanical strength.

Mechanical Properties at Different TPU/PVC Ratios

• Hardness: The hardness of plasticized PVC is similar to pure TPU; therefore, blending different TPU ratios does not significantly change hardness.

• Tensile Strength: At lower TPU content (with TPU as the dispersed phase), blends show higher tensile strength than pure TPU. As TPU content increases and it becomes the continuous phase, tensile strength tends to decrease slightly.

• Optimal Ratio: At a TPU/PVC ratio of 90/10, where TPU forms the continuous phase with limited PVC, the blend achieves the highest tensile strength among all tested ratios.

• Tear Strength: TPU inherently has good tear strength, and the tear strength of TPU/PVC blends generally falls between that of plasticized PVC and pure TPU.

Conclusion

Blending TPU with PVC is an effective and widely adopted modification method to reduce material costs and enhance flame retardancy while leveraging each material's complementary strengths. With careful selection of TPU type, soft segment composition, and optimal blending ratios, manufacturers can achieve TPU/PVC blends with balanced mechanical performance, processability, and cost efficiency.

NANJING HAISI is professional manufacturer of Plastic Extruder Machine, we supply Twin Screw Extruder, Single Screw Extruder, Plastic Recycling Extruder, Two Stage Extruder, Lab Scale Extruder, Mixing and Feeding Machine, Cooling and Pelletizing Machine, Crushing Machine and so on.