Fundamentals of bamboo scrimber hot pressing: Mat compaction and heat transfer process

Abstract

To improve the fundamental understanding of the bamboo scrimber (BS) pressing process, this study examines the current lab and industrial pressing methods, mat compaction behaviour and heat transfer compared to typical wood composites. Mat pressure and compaction ratio follow a polynomial relationship, which indicates only 10% of mat pressure required for hot pressing compared to traditional cold pressing. Typical hot pressing of BS consists of four stages: 1) fast closing to maximum pressure, 2) creep at maximum pressure, 3) stress relaxation at target thickness, and 4) degassing and press opening. Mat pressure and its holding time are critical for manipulating vertical density profile in bamboo scrimber through the mechanisms of thermal softening and viscoelastic creep. The core temperature and gas pressure in densely-packed BS are governed predominantly by heat conduction, similar to plywood rather than oriented strand board. This study provides the fundamental insights which can lead to optimization of the highly complex, energy intensive and lengthy pressing process of bamboo scrimber composites.