TPU And PVC Blending Modification (Part II)

Extensive experimental data shows that PVC/TPU blends exhibit excellent oil resistance, with volume and weight changes (△V and △W) generally below 0.5%. However, these blends tend to have lower solvent resistance, and this drawback increases as the TPU content rises. This is closely related to the fact that TPU itself has good oil resistance but poor resistance to solvents, especially aromatic hydrocarbon solvents. Overall, TPU/PVC blends show a synergy in mechanical properties and chemical resistance. For instance, a TPU/PVC mass ratio of 90/10 delivers the best comprehensive mechanical performance, while a ratio of 30/70 also achieves good results.

Different TPU/PVC ratios also impact the shape memory properties of the blend. At a mass ratio of 80/20, the blend demonstrates reduced hysteresis under cyclic tension compared to pure PVC. However, when the mass ratio is 60/40, the permanent deformation of the blend becomes greater than that of PVC.

PVC significantly enhances the flame retardancy of TPU. For example, when blending plasticized PVC (containing 40 parts DOP plasticizer) with TPU at a 50/50 ratio, the blend still achieves an LOI (Limiting Oxygen Index) value above 21% (with the plasticized PVC alone having an LOI of 25%). Other studies indicate that when the PVC content exceeds 60%, the flame retardant properties of the blend improve substantially—likely because melt blending delays carbonization of TPU.

However, not all TPUs can be mechanically blended with PVC. Due to PVC’s thermal limitations, only soft TPUs are suitable for blending. Harder TPUs with Shore A hardness above 80 typically require processing temperatures around 200°C, making them incompatible for mechanical blending with PVC.

Adding a third polymer component also affects TPU/PVC blend properties. For instance, introducing up to 20% chlorinated polyethylene (CPE) into the blend increases tear strength. A ternary CPE/PVC/TPU blend with 20% CPE and PVC (by total mass) achieves a tear strength of 90 kN/m, compared to just 80 kN/m for TPU alone. Within a moderate CPE/PVC content (under 30%), the ternary blend maintains TPU’s rebound elasticity and oil resistance. CPE/PVC also reduces temperature sensitivity, improving processability while lowering overall material costs by about 15%.

CPE can also suppress TPU thermal degradation, improving heat stability. Although adding CPE slightly reduces mechanical strength, it enhances processability and helps retain TPU’s excellent low-temperature flexibility.

When blended with recycled TPU, CPE also acts as a compatibilizer, strengthening the interfacial transition layer between TPU and PVC. This effect improves the blend’s tensile strength and elongation at break. Additionally, TPU/CPE/HPVC alloys prepared by melt blending show better processability and retain TPU’s cold resistance, although higher CPE/HPVC content can reduce tensile strength.

Moreover, blending TPU, PVC, and copolyester (COP) creates melt-processable rubber with rubber-like properties. This material benefits from TPU’s toughness, PVC’s cost-effectiveness, and COP’s outstanding low-temperature performance, making it highly versatile for applications requiring flexibility, durability, and low cost.

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