Abstract
Polyurethane (PU) foam adhesives were prepared from castor oil as a polyol with isocyanate poly(4,4’-methylene diphenyl isocyanate) (PMDI) using a solvent-free process. The NCO/OH molar ratio used for the preparation of PU foams was 1.5. Water, organosiloxane and dibutyltin dilaurate were used as the blowing agent, surfactant and catalyst, respectively. The ratio of blowing agent and catalyst were adjusted to optimize the properties. The results show that PU foam prepared with 4 wt % of castor oil catalyst and blowing agent has minimal water absorption and maximal volume expansion in the PU foams. FT-IR analysis shows that a urethane bond was formed by the hydroxyl group of castor oil and the –NCO group of isocyanate PMDI. More blowing agent and catalyst could improve the volume expansion ratio and reduce water retention of PU foams. It was found that Moso bamboo charcoal (Phyllostachys pubescens) and China fir wood particle (Cunninghamia lanceolate) composites with setting densities of 500 and 600 kg/m3 can be prepared from optimized castor oil-based PU foam adhesive at 100 °C for 5 min under a pressure of 1.5 MPa. Increasing the amount of bamboo charcoal decreases the equilibrium moisture content, water absorption and internal bonding strength of the composite. Notably, bamboo charcoal composite exhibits excellent dimensional stability. The optimized density and bamboo charcoal percentages of the composite were 500 kg/m3 and 50–100%, respectively. The castor oil-based PU composites containing bamboo charcoal fulfilled the CNS 2215 standards for particleboard. This dimensionally stable, low-density bamboo charcoal composite has high potential to replace current indoor building materials.
Highlights
Biomass is an abundant renewable resource that differs from dwindling petroleum-based materials because the main components are hydrocarbons, which can be converted to industrial raw materials
Hejna et al (2017; 2008) used crude glycerol and castor oil-based polyol to produce rigid PU foams [17,18]. These results show castor oil can be used for PU adhesive studies
Charcoal and wood together and reduce the density of the composite. These results indicate that castor oil-based PU resin could produce low-density composites in this formulation
Summary
Biomass is an abundant renewable resource that differs from dwindling petroleum-based materials because the main components are hydrocarbons, which can be converted to industrial raw materials. A primary goal is to produce biologically-based chemicals directly from biomass, and a bio-refinery is a facility that uses biomass raw materials for bio-based products [1]. Biomass has great potential to help shift consumption towards sustainability in chemicals [2], fuels [3] and other materials [4]. Liquid biomass, such as plant oil, is an excellent candidate to efficiently produce bio-based chemicals, and plant oils have been used as a commercial source of biomass-derived polyols for polyurethane (PU) [5].
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