RHEOLOGICAL PROPERTIES OF POLYVINYLACETAL COLLOIDAL SYSTEMS
Keywords:
dynamic viscosity, shear stress, rotational viscometry, polyvinylacetal, polyvinyl butyral, polyvinyl ethylal, polyvinyl formal, rheological curve, thixotropic recoveryAbstract
This study investigates the dynamic viscosity and thixotropic recovery of polyvinylacetal colloidal systems.Rotational viscometry was employed to determine the dependence of dynamic viscosity (η) on polymer concentration and shear stress (τ). The rheological properties of the polymers examined exhibited a common pattern: viscosity increases with concentration as a result of intensified intermolecular interactions.Detailed analysis of flow curves for polyvinyl butyral solutions revealed pseudoplastic behavior at low shear stresses.With increasing shear stress, a transition to Newtonian flow was observed, where the dynamic viscosity reached a minimum and stabilized. This effect is attributed to the breakdown of macromolecular structural conglomerates, which form in the resting state through hydrogen bonding with water molecules in the dispersion medium.A key finding is the demonstrated ability of polyvinylacetal gels to rapidly restore their structure through thixotropic recovery. The degree of thixotropic recovery (α), calculated as the ratio of effective viscosities during reverse and forward measurement runs, increased substantially with polymer concentration, reaching 94.58%. This property ensures that, following mechanical disruption during application, the polymer layer quickly regains its structural integrity and adhesive performance, which is of practical significance.The obtained results confirm the high efficiency of polyvinylacetals as adhesives and highlight the prospects for further research aimed at optimizing their compositions, exploring the influence of external factors, and elucidating adhesion mechanisms at the molecular level. Such efforts may lead to the development of novel, more advanced materials for the textile industry.
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