Abstract
Enzymatic hydrolysis residues (EHR) from corn stalk are industrial waste from the cellulosic ethanol industry. Lignin was separated as a bio-based polyol from EHR replacing partial petroleum-based polyether polyol to prepare bio-based polyurethane (BPU) foams without any other biomass pretreatment. Single factor experiment and response surface methodology (RSM) were employed to optimize separation conditions and reveal the significant influence of the interaction of conditions on the yield of separated lignin (SL). The effect of SL content (2.5, 5.0, 7.5, 10 and 15%) on the foams morphology and mechanical properties was assessed. Scanning electron microscopy (SEM) results implied that the cell shape was considerably affected by the large SL content, which contributed to an irregular, inhomogeneous, and thick cell wall. An astonishing 9.56 times increase in the compressive modulus and exponential 97.93 times boost in the compressive strength of BPU foams were attributed to the content of 15% SL without any further surface chemical modification. This present paper reports a green, potential and promising method for complete utilization of lignin from EHR in consideration of their abundant supply to greatly enhance the mechanical properties of BPU foams.
Highlights
Polyurethanes (PU) are a versatile class of polymeric materials exhibiting a broad range of applications such as furniture, automotive seating, thermal insulators, packaging and medical devices in form of foams, adhesives, elastomers and many others
Batch experiments were carried out in order to assess the effects of NaOH concentration, liquid–solid ratio, temperature and where MNCO is the number of isocyanate groups in one gram of isocyanate, WNCO is the weight of isocyanate (g), MOH is the number of hydroxyl groups contained in one gram of polyols, WOH is the weight of polyols (g), MAd is the number of hydroxyl groups in one gram of additives, WAd is the weight of additives (g) and WH2O is the weight of water
This paper reports a low-cost, green and relatively simple synthesis of bio-based polyurethane foams employing separated lignin without any further surface chemical modi cation
Summary
Polyurethanes (PU) are a versatile class of polymeric materials exhibiting a broad range of applications such as furniture, automotive seating, thermal insulators, packaging and medical devices in form of foams, adhesives, elastomers and many others. PU foams are synthesized by a polyaddition reaction between polyols and isocyanates in addition to other additives such as surfactants and catalysts used to balance the reaction in the forming process.[1] most of these reagents of PU foams are derived from petroleum, increasing the fossil-fuel source dependence and environmental problems due to its status as a limited resource.[2] biodegradable and renewable bio-based raw materials are receiving increasing attention and popularity. The bio-based polyols have been investigated for the production of sustainable and eco-friendly PU foams, such as lignin,[3] castor oil,[4,5] cellulose,[6] etc.
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