Apparent viscosities of Wiley milled white birch at various particulate sizes, suspension concentrations, and solvent and acid concentrations were measured as a function of temperature. Apparent viscosities decreased reversibly with increasing temperature below 150 °C in water in the absence of acid and/or solvent. At temperatures above 150 °C, or with added solvent or acid, the variation of the apparent viscosities with temperature became irreversible. The steady-state shear dependent behavior is well described by a Bingham model where the yield stress is a strong function of temperature and follows an Arrhenius-type behavior. The suspensions exhibited a negative plastic viscosity at low temperatures, but as the temperature increased, the plastic viscosity became less negative. This temperature dependent rheological behavior is qualitatively similar to that observed for concentrated fibrous suspensions of corn stover and synthetic fibers, indicating these changes are not unique to only birch suspensions and are associated with physical changes in the suspension properties with temperature. The irreversible viscosity changes with increase in temperature above 150 °C in water were anticipated due to partial hydrolysis of biomass in water. This was confirmed when biomass suspensions were sheared in a polar aprotic solvent ($\gamma$-valerolactone) and/or with the addition of sulfuric acid. Finally, the extent of irreversible change in the viscosities was correlated with the change in insoluble solids concentration for the various experiments under different conditions.

Wiley 研磨的白桦树在各种颗粒尺寸、悬浮液浓度以及溶剂和酸浓度下的表观粘度作为温度的函数进行测量。在没有酸和/或溶剂的情况下，表观粘度随着温度升高到 150 °C 以下而可逆地降低。在温度高于 150 °C 或添加溶剂或酸时，表观粘度随温度的变化变得不可逆。Bingham 模型很好地描述了稳态剪切相关行为，其中屈服应力是温度的强函数，并遵循 Arrhenius 型行为。悬浮液在低温下表现出负的塑性粘度，但随着温度的升高，塑性粘度变得不那么负。这种依赖于温度的流变行为与观察到的玉米秸秆和合成纤维的浓缩纤维悬浮液在性质上相似，表明这些变化不仅是桦木悬浮液独有的，而且与悬浮液特性随温度的物理变化有关。由于生物质在水中的部分水解，预计在水中温度超过 150°C 时会发生不可逆的粘度变化。当在极性非质子溶剂中剪切生物质悬浮液时证实了这一点（由于生物质在水中的部分水解，预计在水中温度超过 150°C 时会发生不可逆的粘度变化。当在极性非质子溶剂中剪切生物质悬浮液时证实了这一点（由于生物质在水中的部分水解，预计在水中温度超过 150°C 时会发生不可逆的粘度变化。当在极性非质子溶剂中剪切生物质悬浮液时证实了这一点（$\gamma$-戊内酯）和/或加入硫酸。最后，对于不同条件下的各种实验，粘度不可逆变化的程度与不溶性固体浓度的变化相关。