An Eco-Friendly Wood Adhesive from Alfalfa Leaf Protein

According to the preparation method commonly used for soy proteinαbased adhesives,alfalfa leaf protein was used as the raw material to prepare alfalfa leaf protein-based wood adhesive.Differential scanning calorimetry analyzer(DSC),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTαIR)were used to characterize properties of the alfalfa leaf protein-based adhesive in this paper.The results revealed the following:(1)Chemical compositions and chemical structures of the alfalfa leaf protein were basically identical with those of the soy protein,both belonging to spherical proteins with the basis and potential for protein adhesives preparation,and spatial cross-linked network structures would be easily formed.(2)Alfalfa leaf protein and soy protein adhesives had the similar curing behaviors,curing temperature of alfalfa leaf protein-based adhesive was relaαtively lower,and the heating rate had minor influence on curing temperature of alfalfa leaf protein-based adhesive.At different heating rates,change tendencies of curing reaction degrees of both the two adhesives were not totally the same.(3)Activation energy and reaction frequency factor of the alfalfa leaf protein-based adhesive were higher than those of soy protein-based adhesive,indicating that the curing reaction of the alfalfa leaf protein adhesive was more difficult than soy protein-based adhesive,thus the dry shear strength and water resistance of alfalfa protein-based adhesive were lower than those of soy protein-based adhesive.Dynamics models of curing reactions of alfalfa leaf protein-based adhesive and soy protein-based adhesive are dα=dt/1.06×10^(13)e^(-97370/RT)(1-α)^(0.938) and dα/dt=1.09×10^(11)e^(-84260/RT) 1-α)^(0.928) respectively.The results of this study will expand the selection of raw materials for protein-based wood adhesives.

Improvement of the Compressive Strength of Carbon Fiber/Epoxy Composites via Microwave Curing

Microwave processing was used to cure the carbon fiber/epoxy composites and designed for improving the compressive strength of the materials. By controlling the power of microwave heating, vacuum bagged laminates were fabricated under one atmosphere pressure without arcing. The physical and mechanical properties of composites produced through vacuum bagging using microwave and thermal curing were compared and the multistep （2-step or 3-step） microwave curing process for improved compressive properties was established. The results indicated that microwave cured samples had somewhat differentiated molecular structure and showed slightly higher glass transition temperature. The 2-step process was found to be more conducive to the enhancement of the compressive strength than the 3-step process. A 39% cure cycle time reduction and a 22% compressive strength increment were achieved for the composites manufactured with microwave radiation. The improvement in specific compressive strength was attributed to better interracial bonding between resin matrix and the fibers, which was also demonstrated via scanning electron microscopy analysis.

Preparation and properties of T-ZnO_(w) enhanced BCP scaffolds with double-layer structure by digital light processing

Bone scaffolds require both good bioactivity and mechanical properties to keep shape and promote bone repair.In this work,T-ZnO_(w) enhanced biphasic calcium phosphate(BCP)scaffolds with triply periodic minimal surface(TPMS)-based double-layer porous structure were fabricated by digital light processing(DLP)with high precision.Property of suspension was first discussed to obtain better printing quality.After sintering,T-ZnO_(w) reacts with b-tricalcium phosphate(β-TCP)to form Ca_(19)Zn_(2)(PO_(4))14,and inhibits the phase transition toα-TCP.With the content of T-ZnO_(w) increasing from 0 to 2 wt%,the flexural strength increases from 40.9 to 68.5 MPa because the four-needle whiskers can disperse stress,and have the effect of pulling out as well as fracture toughening.However,excessive whiskers will reduce the cure depth,and cause more printing defects,thus reducing the mechanical strength.Besides,T-ZnO_(w) accelerates the deposition of apatite,and the sample with 2 wt%T-ZnO_(w) shows the fastest mineralization rate.The good biocompatibility has been proved by cell proliferation test.Results confirmed that doping T-ZnO_(w) can improve the mechanical strength of BCP scaffolds,and keep good biological property,which provides a new strategy for better bone repair.