Today's KNOWLEDGE Share
π¬ PVC Compounding: Why PVC Absorbs Plasticizers Unevenly
One of the most misunderstood behaviours in flexible PVC is the uneven absorption of plasticizers. Although PVC particles may look uniform, their internal structure is far from identical. Differences in porosity, particle morphology and microvoid distribution affect how quickly and how completely plasticizers diffuse into the polymer. As a result, two particles from the same batch can behave very differently under the same conditions.
Temperature and mixing energy also play critical roles. If the dry blend heats unevenly, some particles begin absorbing plasticizer faster than others, creating regions with different gelation rates. This affects fusion, torque, melt strength and surface appearance. Even stabilizers, fillers and pigments can influence absorption by blocking diffusion pathways or altering the local polarity inside the mixture.
Converters notice this behaviour as variations in plastisol viscosity, calendering window, wire coating smoothness or the flexibility of the final product. The challenge is that uneven plasticizer uptake often originates long before extrusion begins, inside the dry blend itself.
In your view, which factor drives the biggest variation in plasticizer absorption: particle morphology, mixing temperature or the presence of fillers?
source : Orbimind AB
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