Sodium dodecyl sulfate improves the properties of bio-based wood adhesive derived from micronized starch: Microstructure and rheological behaviors

Preparation and characterization on the eco-friendly corn starch based adhesive of with salient water resistance, mildew resistance

Starch adhesive is a commonly used bonding glue that is sustainable, formaldehyde-free and biodegradable. However, there are obviously some problems related to its high viscosity, poor water and mildew resistance. Hence, exploring a starch-based adhesive with good properties that satisfies the requirements of wood processing presents the context of the current research. Thus, corn starch was used as raw material to form oxidized starch (OCS) via oxidation using sodium periodate, it was reacted with a synthesis polyurea compound that prepared from hexanediamine-urea (HU) obtained by deamination to yield a oxidized starch-hexanediamine-urea adhesive (denoted hereafter as OCSHU). The oxidation process was optimized in terms of oxidant concentration, reaction time and temperature. Furthermore, the impact of HU addition on the mechanical properties of the adhesive was explored. Results indicate adhesive exhibited outstanding shear strength, when 13 % of NaIO4 was used as an oxidant to treat starch at 55 °C for 24 h, and involved in a subsequent reaction with 40 % of HU. The dry shear strength, 24 h cold water strength, 3 h hot water strength and 3 h boiling water strength are 1.84, 1.50, 1.32, and 1.31 MPa. Meantime, OCSHU adhesive solution revealed good storage stability whereas cured resin exhibited mildew resistance. The developed adhesive is a simple and green biomass wood adhesive.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Effect of nano-TiO2 particle size on the bonding performance and film-forming properties of starch-based wood adhesives

The effect of nano-TiO₂ particle size on the properties of starch-based wood adhesives was studied in this work. Our findings indicate that a smaller size of nano-TiO₂ particles corresponds with a larger specific surface area and more hydroxyl sites on the particle surface that interact with latex molecules, forming a more compact network structure. Therefore, the bonding performance and water resistance of the adhesive were enhanced. In addition, rheology results showed that the adhesive behaves as a pseudoplastic fluid. Small-angle X-ray scattering and energy dispersive spectroscopy confirmed the good compatibility and dispersion of nano-TiO₂ in the adhesive films. Diffusing wave spectroscopy and scanning electron microscopy showed that smaller TiO₂ particles were more favorable for the formation of smoother and denser films. These results are of great significance for improving the structure and properties of starch-based wood adhesives and preparing high-performance environmentally friendly biobased adhesives.

Fabrication of bilayer emulsion by ultrasonic emulsification: Effects of chitosan on the interfacial stability of emulsion

In this study, the stable system of bilayer emulsion was fabricated by ultrasonic emulsification. The effect of chitosan (CS) addition (0.05 %-0.4 %, w/v) at pH 5.0 on the stability of rice bran protein hydrolysate-ferulic acid (RBPH-FA) monolayer emulsion was investigated. It was found that the addition of CS (0.3 %) could form a stable bilayer emulsion. The droplet size was 3.38 μm and the absolute ζ-potential value was 31.52 mV. The bilayer emulsion had better storage stability, oxidation stability and environmental stabilities than the monolayer emulsion. The results of in vitro simulations revealed the bilayer emulsion was able to deliver the β-carotene to the small intestine digestive stage stably and the bioaccessibility was increased from 22.34 % to 61.36 % compared with the monolayer emulsion. The research confirmed that the bilayer emulsion prepared by ultrasonic emulsification can be used for the delivery of hydrophobic functional component β-carotene.

Preparation and Characterization of Polyvinylalcohol/Polysulfone Composite Membranes for Enhanced CO2/N2 Separation

The unique properties of polyvinyl alcohol (PVA) and polysulfone (PSf), such as good membrane-forming ability and adjustable structure, provide a great opportunity for CO₂-separation membrane development. This work focuses on the fabrication of PVA/PSf composite membranes for CO₂/N₂ separations. The membranes prepared by coating a 7.5 wt% PVA on top of PSf substrate showed a relatively thin selective layer of 1.7 µm with an enhanced CO₂/N₂ selectivity of 78, which is a ca. 200% increase compared to the pure PSf membranes. The CO₂/N₂ selectivity decreases at a rapid rate with the increase of feed pressure from 1.8 to 5 bar, while the CO₂ permeance shows a slight reduction, which is caused by the weakening of coupling transportation between water and CO₂ molecules, as well as membrane compaction at higher pressures. Increasing operating temperature from 22 °C to 50 °C leads to a slight decrease in CO₂ permeance, but a significant reduction in the CO₂/N₂ selectivity from 78 to 27.1. Moreover, the mass transfer coefficient of gas molecules is expected to increase at a higher velocity, which leads to the increase of CO₂ permeance at higher feed flow rates. It was concluded that the CO₂ separation performance of the prepared membranes was significantly dependent on the membrane operating parameters, and process design and optimization are crucial to bringing CO₂-separation membranes for industrial applications in post-combustion carbon capture.

Modified Starch-Based Adhesives: A Review

Consumer trends towards environmentally friendly products are driving plastics industries to investigate more benign alternatives to petroleum-based polymers. In the case of adhesives, one possibility to achieve sustainable production is to use non-toxic, low-cost starches as biodegradable raw materials for adhesive production. While native starch contains only hydroxyl groups and has limited scope, chemically modified starch shows superior water resistance properties for adhesive applications. Esterified starches, starches with ester substituents, can be feasibly produced and utilized to prepare bio-based adhesives with improved water resistance. Syntheses of esterified starch materials can involve esterification, transesterification, alkylation, acetylation, succinylation, or enzymatic reactions. The main focus of this review is on the production of esterified starches and their utilization in adhesive applications (for paper, plywood, wood composites, fiberboard, and particleboard). The latter part of this review discusses other processes (etherification, crosslinking, grafting, oxidation, or utilizing biobased coupling agents) to prepare modified starches that can be further applied in adhesive production. Further discussion on the characteristics of modified starch materials and required processing methods for adhesive production is also included.

Development of Starch-Based Materials Using Current Modification Techniques and Their Applications: A Review

Starch is one of the most common biodegradable polymers found in nature, and it is widely utilized in the food and beverage, bioplastic industry, paper industry, textile, and biofuel industries. Starch has received significant attention due to its environmental benignity, easy fabrication, relative abundance, non-toxicity, and biodegradability. However, native starch cannot be directly used due to its poor thermo-mechanical properties and higher water absorptivity. Therefore, native starch needs to be modified before its use. Major starch modification techniques include genetic, enzymatic, physical, and chemical. Among those, chemical modification techniques are widely employed in industries. This review presents comprehensive coverage of chemical starch modification techniques and genetic, enzymatic, and physical methods developed over the past few years. In addition, the current applications of chemically modified starch in the fields of packaging, adhesives, pharmaceuticals, agriculture, superabsorbent and wastewater treatment have also been discussed.

Functional nanoparticle reinforced starch-based adhesive emulsion: Toward robust stability and high bonding performance

Sustainable bio-based adhesive is a promising substitute for petroleum-based adhesives to alleviate serious environmental and health problems. In this work, a nanoengineered starch-based adhesive was fabricated by grafting vinyl acetate (VAc) onto starch molecule and subsequently incorporating the functional nanoparticle [TiO₂-coupling-poly(butyl acrylate, BA), TKB] to overcome the drawbacks present in conventional nanocomposite adhesive. Results showed that the presence of BA altered the surface property of TKB, leading to improved dispersion. In the adhesive with 4% (mass ratio to starch) TKB, TKB aggregates played the role as a sliding bridge, which significantly promoted the storage stability and shear strength in both dry and wet states. Additionally, the latex film with 4% TKB exhibited high compatibility and water resistance due to the promoted hydrophobicity. This study provides a fundamental insight into the improvement of functional nanoparticles on the performance of starch-based adhesive, suggesting a novel strategy for designing high-performance bio-adhesive.

Evaluation and analysis of volatile organic compounds and formaldehyde emission of building products in accordance with legal standards: A statistical experimental study

Building materials have been developed mainly for thermal performance, strength, low energy consumption, and aesthetics. Consequently, large amounts of chemicals have been added to building products, resulting in the release of abundant pollutants that adversely affect human health. In particular, pollutants from the materials used to build modern dwellings can cause sick house syndrome, which leads to health resilience problems and diseases. In this study, more than 100 investigations were conducted annually from 2004 to 2017 by using the 20 L small chamber method to analyze the contents of formaldehyde (HCHO) and total volatile organic compounds (TVOC) released from 2780 building products in total. High emissions were released by some building components with raw materials containing hazardous chemicals. However, since the 2004 enactment of a legal standard for the regulation of emissions of harmful substances in building products, the pollutant emissions have tended to decrease over the years. As a result of the experiment, all 2780 building materials met the legal standard on average. Therefore, legal restrictions on the release of hazardous materials from building products have achieved reductions in pollutant emissions.

High-performance water-borne fluorescent acrylic-based adhesive: synthesis and application

Water-borne adhesives have immense importance in cellulose-based materials, where their durability, handling, and strength remain to be a major concern. The present work demonstrates the development of three water-borne adhesives, namely, poly(1-vinyl-2-pyrrolidone-co-acrylic acid), poly(acrylonitrile-co-acrylic acid), and poly(1-vinyl-2-pyrrolidone-co-acrylonitrile-co-acrylic acid) applicable for cellulose-based materials. These acrylic-acid based adhesives were characterized by Fourier-transform infra-red spectroscopy, thermogravimetric analysis, X-ray diffraction, gel permeation chromatography, and universal testing machine. The synthesized polymer adhesives can be stored in the powder form for a longer period, thus utilizing less space. In order to use as adhesives, suitable formulations can be prepared in water. The adhesives show thermal stability up to 300 °C. Our studies show that poly(1-vinyl-2-pyrrolidone-co-acrylonitrile-co-acrylic acid) showed higher lap shear strength (ASTM D-906) than commercially available adhesives. In addition, these adhesives, being fluorescent in nature, can be detected under UV light and thus are applicable for the detection of fractured joints of any specimen. This property also helps in anti-counterfeiting applications, thus adding further to their utility.

Synthesis and application of a water-borne fluorescent acrylic adhesive, which can be stored as a powder for long-term use.