Optimization of hot-pressing process for cotton-stalk-based artificial boards

To enhance the board strength of cotton stalk-based composite boards and optimize the hot-pressing process, this study fabricated artificial boards using crushed and sieved cotton stalk xylem and modified urea-formaldehyde resin as the primary raw materials. The effects of seven key factors—particle size, adhesive dosage, solid content of the resin, hot-pressing temperature, hot-pressing pressure, pre-pressing time, and hot-pressing duration—on the mechanical properties of the composite boards were investigated. The significance of these factors and the optimal process parameters were systematically determined.

In this study, the internal bonding strength (IB) of the composite boards was selected as the experimental indicator. A Plackett-Burman (PB) experimental design was employed to screen significant factors affecting IB. Based on the PB results, a steepest ascent experiment was conducted to determine the optimal parameter ranges for the identified significant factors. Subsequently, a three-factor, three-level Box-Behnken design (BBD) was implemented to construct a quadratic polynomial regression model. Analysis of variance (ANOVA) and response surface methodology (RSM) were applied to analyze the interactions and significance between key process parameters. Finally, the optimized process parameters were derived and validated through experimental verification.

1）The factors significantly affecting the internal bonding strength (IB) of the composite boards were ranked in the following order of significance: adhesive dosage, hot-pressing temperature, and hot-pressing pressure; 2) The optimal process parameters derived from Design-Expert V13.0 software optimization were as follows: particle size (0-1 mm), adhesive dosage (13%), solid content of the resin (45%), hot-pressing temperature (150 ℃), hot-pressing pressure (8.8 MPa), pre-pressing time (2.5 h), and hot-pressing duration (9 min). Under these conditions, the cotton stalk-based composite board exhibited an internal bonding strength (IB) of 0.64 MPa, closely aligning with the model-predicted theoretical value of 0.65 MPa, with a minimal deviation of 1.54% between experimental and theoretical results.

The response surface model demonstrated high accuracy and reliability. These findings provide valuable insights for optimizing the manufacturing process of cotton stalk-based composite boards, particularly in refining hot-pressing parameters and resin application strategies.