Effect of softening treatments on the properties of high-density cylindrical luffa as potential mattress cushioning material

Cylindrical luffa has potential to be a lightweight mattress cushioning material with good air permeability, dryness and comfort. However, it is extremely firm and requires suitable softening treatment prior to use. In this work, the effects of three alkali-based softening treatments on the chemical composition, microstructure, physical and mechanical properties, and water absorption and desorption properties of high-density (HD) luffa fiber bundles were investigated. The softening treatment with 5% NaOH/5% H2O2 significantly lowered the compressive strength and plateau stress of HD cylindrical luffa by 77% and 73%, respectively. Moreover, large amounts of lignin, hemicellulose and amorphous cellulose were removed from HD luffa fibers after the treatment, resulting in loosening of the HD luffa fiber cells and fiber bundles. Although the softening treatment with 10% NaOH/20% CH3COOH only slightly reduced the compressive strength and plateau stress of HD cylindrical luffa, it significantly improved the flexibility of HD luffa fiber bundles. After being separately treated by 5% NaOH/5% H2O2, 10% NaOH/20% CH3COOH, and 18% NaOH/1.6% CO(NH2)(2), the water desorption ratios of HD luffa after 12 h were all increased and reached 94%, 90% and 93%, respectively. The results indicated that the softening treatment with 10% NaOH/20% CH3COOH was a suitable method for obtaining softer and durable HD cylindrical luffa as potential mattress cushioning material. Graphic abstract The schematic diagram of three softening treatments. (a) Hierarchical structures of the luffa cylinders, (b) and (c) changes in the microfibril structure before and after HD luffa cylinders were treated by Methods 1, 2, and 3. [GRAPHICS] .