Enhancing bamboo scrimber mechanical properties and mildew resistance through gamma irradiation crosslinking modification

Bamboo scrimber is a dense and strong bamboo-based composite. As a fatal defect of bamboo-based composites, mildew seriously affects their performance and lifespan. Gamma irradiation is an efficient, safe, and environmentally friendly method to crosslink polymers and improve their strength. However, high irradiation doses lead to the decomposition of polymers in bamboo. In addition, moisture within natural bamboo promotes the excitation and reaction of free radicals. Therefore, balancing the irradiation dose with the bamboo moisture is crucial. In this study, the internal components of bamboo were self-crosslinked by controlling the gamma irradiation dose and the moisture content (MC) of bamboo bundles. The results indicated that the 100KGy-MC80 % bamboo scrimber exhibited the best overall performance. The cellulose and lignin were crosslinked by esterification reaction at low doses (<= 100KGy), therefore, the modulus of rupture (MOR), the modulus of elasticity (MOE), the compressive strength parallel to grain (CSPG), and the dimensional stability of bamboo scrimber were effectively improved. When the gamma irradiation dose reached 150KGy, the cellulose and hemicellulose decomposed, which reduced free hydroxyl groups, as a result, the MOR, the MOE, and the CSPG decreased while the dimensional stability kept growing. The internal moisture of bamboo promotes the excitation and reaction of free radicals, amplifying the effect of irradiation. The mildew resistance was improved by the reason of the decomposition of hemicellulose and starch, which limit the moisture and nutrient conditions required by mildew.