Objective This study aimed to investigate the effects of impregnation with mildly acidic zinc chloride solution on the dimensional stability of heat-treated materials as well as the treatment energy consumption.

Method Mongolian scots pine specimens were impregnated with a 5% zinc chloride solution and subjected to high-temperature heat treatment at different temperatures. Subsequently, we assessed the dimensional stability and moisture absorption of these treated Mongolian scots pine samples by examining their dimensional and mass changes after moisture absorption. To deepen our understanding, we complemented this with infrared spectroscopy, X-ray diffraction analysis, and energy consumption assessments. These analyses aimed to clarify both the mechanism and the energy requirements associated with impregnation and heat treatment concerning the specimens’ dimensional stability.

Result The performance enhancement effect of the zinc chloride impregnation-heat treatment group was more pronounced than that of the heat treatment group. As the heat treatment temperature increased, the hygroscopicity of sample decreased, and the dimensional stability improved. The volumetric swelling ratios of the heat treatment group and the zinc chloride impregnation-heat treatment group decreased from 3.5% and 3.4% to 2.6% and 2.1%, respectively. Infrared absorption spectra of the treated materials under both methods did not exhibit new functional group characteristic peaks; however, the hydroxyl content decreased significantly with increasing temperature. The relative crystallinity of the treated material increased in both the heat treatment group and the impregnation-heat treatment group, rising from 36.05% and 38.77% to 48.51% and 53.04%, respectively. Notably, the treatment effect achieved by the zinc chloride impregnation-heat treatment group at 160 ℃ was superior to that achieved solely by 180 ℃ heat treatment. Moreover, due to the lower treatment temperature of the former, energy consumption during the process could be reduced, potentially saving up to about 10% within the studied temperature range.

Conclusion Compared with heat treatment modification alone for Mongolian scots pine, the combined modification of zinc chloride impregnation-heat treatment can achieve the similar effect of dimensional stability improvement by adopting lower heat treatment temperatures, which contributes to energy saving and emission reduction of heat treatment process. However, further in-depth study is required to assess its impact on mechanical properties.