PVAC solution viscosity

Polyvinyl alcohols (PVAl) are manufactured by saponification of vinyl acetate polymers (PVAc). Properties of PVC using PVAl as a protective colloid are influenced by the solution viscosity of the PVAl, i.e. the degree of polymerization of the PVAc and the degree of saponification. Polyvinyl alcohols of 75-90% hydrolysis are primary suspension agents for S-PVC, whereas polyvinyl alcohols of 25-40% hydrolysis are secondary suspension agents, which control the agglomeration of the primary particles. Partially hydrolyzed PVAc can be block or random polymers. 

FIGURE 3.6 Effect of molecular weight on the viscosity of PVAC solutions. PVAC polymers (Cairn) (Table 7.1) were dissolved in cyclohexanone to form 40% solutions (by weight). These were dyed to aid visibility. The test tubes were tipped over and photographed after 2seconds. The low-molecular-weight polymer solutions flowed faster (a) S2. (b) SI. (c) S27. 

PVAc may be produced by the polymerization of vinyl acetate (Equation 6.47). The viscosity of the solution continues to increase until the reaction is complete. Dilute polymer solutions are used to prevent the onset of autoacceleration because of the gel effect. 

Graessley and co-workers have studied the rheological properties of solutions of branched PVAc in diethyl phthalate (178, 188), using polymer concentrations of 0.17, 0.225, and 0.35 g ml-1. At the lowest concentration, the low shear-rate viscosity was simply related to [17], so that it was lower for branched polymers the equation ... 

Using an earlier version of the dynamic model given in Section IV,6, Kiparissides et al (1980b) illustrated the use of such an extended Kalman Filter to infer JV(f), VJit), AJit), and X(f) from measurements taken only on conversion [X(f)J using UV turbidity spectra. Jo and Bankoff (197Q used these filters to track some of the moments of the MWD of PVAc in a solution polymerization process using measurements made on refractive index and viscosity. 

PVA Erkol is produced by polymerisation of vinylacetate to polyvinylacetate PVAC, followed by the hydrolysis of PVAC in PVA. The degree of polymerisation determines the molecular weight and viscosity of PVA Erkol in solution. The degree of hydrolysis (saponification) signifies the extent of conversion of the PVAC to PVA. Partially hydrolysed PVA has a Tg of 58 °C and a Tm of 180 °C. Totally hydrolysed PVA has a Tg of 85 °C and a Tm of 230 °C. PVA can be used in the production of paper, clothes, glues, paints, pharmaceutical products, building materials, ceramics, etc. (Erkol, undated). 

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