Using kenaf pulping waste to mold packaging materials (below)

2 Results and Discussion

2.1 KL kenaf black liquor modified urea-formaldehyde adhesive shear strength

The hydroxymethylated KI black liquor is mixed with the self-made urea-formaldehyde glue in a weight ratio of 1:4, and the kilograms of kenaf-modified black urea-formaldehyde glue are prepared by mixing evenly. A small amount of curing agent is added during sizing. The test conditions are: the test piece is two pieces of glued joints, and the material is pine wood; the curing condition is set as 110° C. for 30 minutes. The test results are shown in Table 1.

When the shear strength reaches 8.20 MPa, the adhesive is not destroyed and the pine material has been destroyed. Therefore, the shear strength of the KI hemp straw black-modified urea-formaldehyde rubber is > 8.20 MPa. Can meet the use of particleboard packaging materials.

2.2 Research of the board making process

The process parameters of the molded particle board are mutually restricted and have different degrees of influence on the final performance of the board. The main influencing factors are the amount of glue, pressure, temperature, and curing time. For juniper core and shavings, the proportion of hemp core is also one of the important factors. In the test, orthogonal I was used under fixed pressure conditions. (3) Test method to examine the influence of the amount of glue, pressure, temperature and hemp ratio on the performance of the particle board. See Table 2 for each factor and level.

The static strength, puncture strength, and density of the manufactured particle board were measured and the results are shown in Table 4.

2.3 Effect of glue usage

The strength of the molded particleboard increases with the increase in the amount of glue used, and increases between 8% and 10%. The amount of glue increases from 10% to 12%. The increase in static bending strength and puncture strength is significant. reduce. Due to the limitation of experimental conditions, manual mixing is used. If mechanical mixing is used, the mixing uniformity is greatly improved, and the bonding effect can be improved. Therefore, taking into account the mixing efficiency, product strength, and product cost, a 10% adhesive volume is the optimal amount for the test conditions.

2.4 Effect of Curing Time and Curing Temperature

The strength of the molded board generally comes from the strength of the shavings themselves and the bonding strength between the shavings. The appropriate high temperature is conducive to the softening of shavings, the promotion of the glueing of the intercellular lignin of the fiber and the binder, and the softening of the shavings also facilitates the compaction of the plate and the increase of the plate density. The test results at 145 °C illustrate this point. The softening of the shavings is also lower at lower temperatures, and the curing of the surface coatings is faster at higher temperatures. It is not conducive to the diffusion and gasification of the inner moisture, and it is easy to form a brittle-hard plate structure with a rough inner layer.

The longer hot-pressing time is conducive to the full curing of the glue layer and the glue between the glue layer and the shavings and the removal of moisture. Therefore, the strength and density of the board increase with time. Curing time directly affects production efficiency, shortening time is significant, but from the experimental results, the pressure is large, fast compaction, short time, but the surface density of the product is uneven, the surface density is high and the density of the inner layer is small; reduce the pressure, appropriate extension Hot pressing time can make the Z-shaped molded products uniform in density and tend to have a uniform strength. From the experimental results, the hot-pressing time of 25 min is the best choice under the experimental conditions.

2.5 Influence of the proportion of flax

The hemp core is the raw material waste of the hemp papermaking, and has certain compressibility. As the filler material is mixed with the shavings after certain proportions, the molded particleboard is controlled to control the amount, and the board weight can be properly reduced without affecting the physical properties of the particleboard. This is of great significance for reducing the weight of packages, reducing transportation costs and saving timber resources. However, the hemp core structure is loose and porous, and the adhesive force with the adhesive layer is low. Therefore, adding too much amount may cause the static bending strength and the puncture strength of the particle board to decrease. From the test data, the particle board weight decreased with the increase of hemp consumption from 30% to 50%, but the board strength also decreased. In the selection of the amount of glue 10%, curing time and temperature of 25 min, l45 °C, hot pressure under the conditions of 2 MPa, the impact of hemp proportion shown in Figure 1.

It can be seen from the figure that when the proportion of hemp core is low, the static bending strength of the particle board has little influence, but when the proportion of hemp core is increased to more than 30%, the static bending strength drops significantly with the increase of the hemp core usage. Should exceed 30%.

3 Conclusion

Through the analysis of the physical properties of the molded products obtained under the experimental conditions, combined with the particleboard-cow production efficiency and production cost, a better pressboard process conditions are obtained: the amount of plastic used lO%, the hot pressing temperature of 145°C, and the hot pressing time For 25 minutes, the ratio of hemp to shavings was 3:7 (weight ratio), and the hot pressing pressure was 2 MPa. The molded plate had good performance. After modification and performance determination of kenaf pulping black liquor, modified black liquor and self-made urea-formaldehyde rubber were formulated in a ratio of 1:4 to make black urea-formaldehyde rubber with good adhesive force, which can be used for molding particleboard Use adhesives.

Wang Xiaomin Huo Lijiang Wang Nan Xu Wei Department of Printing and Packaging Engineering, Dalian Institute of Light Industry

Source of Information "Journal of Zhuzhou Institute of Technology"