Research Progress of Soybean Protein Adhesive:A Review

Traditional formaldehyde-based adhesives rely excessively on petrochemical resources,release toxic gases,and pollute the environment.Plant-derived soybean protein adhesives are eco-friendly materials that have the potential to replace the formaldehyde-based adhesives used to fabricate wood-based panels.However,the poor water resistance,high brittleness,and poor mildew resistance of soybean protein adhesives limit their industrial applications.This article reviews recent research progress in the modification of soybean protein adhesives for improving the bonding performance of adhesives used for wood-based panel fabrication.Modification methods were summarized in terms of water resistance,solid content,and mildew resistance.The modification mechanisms and remaining problems were also discussed.Finally,the current industrial applications and the future research direction of soybean protein adhesives are discussed.

New nonlinear stiffness actuator with predefined torque‒deflection profile

A nonlinear stiffness actuator(NSA)could achieve high torque/force resolution in low stiffness range and high bandwidth in high stiffness range,both of which are beneficial for physical interaction between a robot and the environment.Currently,most of NSAs are complex and hardly used for engineering.In this paper,oriented to engineering applications,a new simple NSA was proposed,mainly including leaf springs and especially designed cams,which could perform a predefined relationship between torque and deflection.The new NSA has a compact structure,and it is lightweight,both of which are also beneficial for its practical application.An analytical methodology that maps the predefined relationship between torque and deflection to the profile of the cam was developed.The optimal parameters of the structure were given by analyzing the weight of the NSA and the mechanic characteristic of the leaf spring.Though sliding friction force is inevitable because no rollers were used in the cam-based mechanism,the sliding displacement between the cam and the leaf spring is very small,and consumption of sliding friction force is very low.Simulations of different torque‒deflection profiles were carried out to verify the accuracy and applicability of performing predefined torque‒deflection profiles.Three kinds of prototype experiments,including verification experiment of the predefined torque‒deflection profile,torque tracking experiment,and position tracking experiment under different loads,were conducted.The results prove the accuracy of performing the predefined torque‒deflection profile,the tracking performance,and the interactive performance of the new NSA.

A Soy Protein-Based Composite Film with a Hierarchical Structure Inspired by Nacre

Soy protein-based composite film is a potential replacement for petroleum-based film with multipurpose applica-tions and cleaner production.It is difficult to improve both the tensile strength and toughness of a protein-based film without sacrificing its elongation.In this study,inspired by the hierarchical structure of nacre,a facile yet delicate strategy was developed to fabricate a novel bio-based film with excellent toughness and high strength.Triglycidylamine(TGA)crosslinked soy protein(SPI)as hard phase and thermoplastic polyurethane elastomer(TPU)as soft phase comprise an alternative lay-up hierarchical structure.The interface of these two phases is enhanced using triglycidylamine(TGA)surface-modified TPU(MTPU).The tensile strength of SPI/MTPU/TGA films increases by 392%to 7.78 MPa and their toughness increases by 391%to 8.50 MJ/m^(3) compared to soy protein/glycerol film.The proposed hierarchical structure can also be extended to other high-performance materials and polymers.