Polyvinyl Chloride (PVC) is one of the most widely used thermoplastic polymers which is often used e.g. in building industry. PVC is highly resistant to other chemical products and can be easily mixed with many additives in order to adjust its properties. PVC is produced with different degrees of polymerisation. One differs between rigid PVC and flexible PVC.
There are several processes for producing PVC, one of which is suspension polymerization. In this process, a vinyl chloride monomer is dispersed in water by vigorous agitation. The addition of suspension stabilizing agents lowers the coalescence of the forming vinyl chloride droplets and adjusts the particle sizes of the monomer droplets as well as the particle sizes and porosity of the PVC after polymerization.
HPMC - Hydroxypropyl Methyl Cellulose (ARBOCEL® CE) is beside Polyvinylalcohol (PVA) one of the most commonly used suspension agents.
ARBOCEL® CE helps to control particle sizes, allows uniform particle size distribution and influences the porosity. The porosity of the polymer particles is strongly linked to the property to adsorb additives like e.g. plasticizers or stabilizers which finally lead to the demanded properties of the polymer during processing and for the final product.
PVC particles produced by this method show particle sizes of 50 to 300 μ m. The grains have a smooth surface and irregular shape. They show a porous interior, with primary particles of 1 - 3 μ m in size. The exterior is covered by a skin or membrane of 0.5 -1.0 μ m thickness and consists mostly of PVC. This peculiar and complex morphology is due to the insolubility of PVC in its own monomer.
Ultra low viscous ARBOCEL® CE is the most suitable product for PVC manufacturing processes. Methoxy and hydroxypropyl substitution levels and the viscosity determine the performance characteristics as a PVC suspending agent. Besides this, the particle size of the HPMC powders are specially designed to dissolve perfectly for a smooth production.
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