Polyamide Epichlorohydrin Resin Research Articles

Development of High Strength, High Water Resistant, Low‐Formaldehyde Emission Urea‐Formaldehyde Adhesive and Its Effect on the Properties of Wood Composites

ABSTRACTUrea–formaldehyde (UF) resin adhesive is one of the most widely applied in wood composite materials. However, it suffers from issues related to low water resistance and elevated levels of formaldehyde emission. In this study, polyamide–epichlorohydrin resin (PAE) was used as a modifier and crosslinking agent to prepare modified UF resin adhesives with high strength and water resistance using low molar ratio UF resin. The interaction between PAE, UF, and wood surface and the effect of PAE on the chemical structure, thermal stability, bonding strength, water resistance, adhesive layer characteristics, and formaldehyde emission of UF adhesive were studied. Compared with the pure UF adhesive, after adding 5% PAE, the dry bonding strength reached 1.405 MPa, which was 20.70% higher than that of the pure UF adhesive. At the same time, the wet bonding strength reached 1.188 MPa, which was increased by 33.33%. In addition, the formaldehyde emission of the prepared plywood was less than 1.5 mg/L, which met the E1 standard. This work presents a novel approach to address the challenge of balancing water resistance and formaldehyde emissions in UF resin adhesives, expanding the industrial utilization of UF resin wood adhesives.

Enhancing Cross-Linking Network for Superior Wet Strength of Paper by Sustainable Hyperbranched Polyimines.

The paper industry has long been a crucial part of our lives, providing printing materials, tissue paper, and packaging products. However, the low wet strength of commercially available paper limits its application in packaging, particularly when it comes into contact with liquids. To address this issue, researchers have explored various strategies, including the use of wet strength agents. The most widely used agent, polyamide-epichlorohydrin resin (PAE), has limitations, such as poor dimensional stability and limited recyclability. Additionally, PAE can release harmful chlorinated organics. To overcome these challenges, we report a novel approach using a hyperbranched wet strength agent (referred to as "OA-PI") based on the cross-linking of oxidized amylopectin from waxy corn and polyamines through the Schiff base reaction. The hyperbranched structure of OA-PI provides multiple binding sites, enhancing the cross-linking strength of cellulosic paper under wet conditions. The paper treated with OA-PI exhibited exceptional wet strength, significantly higher than that of PAE-treated paper and paper with traditional starch-based additives. Moreover, the biomass-based OA-PI showed improved recyclability and reduced harm from chlorinated organic compounds. This study not only enhances the wet strength of paper but also opens sustainable avenues for the design of functional adhesives.

Increased recyclability of wet strengthened liquid packaging board, through synergetic effects of combining CMC and PAE – a case study in full scale

Abstract There is an ever-increasing demand for renewable, recyclable and biodegradable packaging solutions, from consumers, producers of goods, and producers of packaging materials. Closing the material loop and increasing recyclability of fiber-based package materials is one of the keys to move forward towards a more sustainable future. While the recyclability rates of fiber-based packaging are high, packaging boards with high wet-strength can pose problems due to problems with repulping. This manuscript investigated the possibilities to reduce the use of polyamide-epichlorohydrin resins (PAE) by supporting the process system with carboxy-methylated cellulose (CMC) through machine trials in mill scale production. The focus of the investigation was on the wet-strength of the board product and the repulpability value. The results given from the full-scale trial were positive, indicating a potential in using CMC while reducing the PAE addition. The results showed that wet tear strength and wet tensile strength of the board were maintained, while higher repulpability rates were given, encouraging better recyclability of the board material. This will be beneficial to the environment both with lower use of non-renewable chemicals and possibilities for higher degrees of recycling of the board products.

Paper packaging materials: modeling and optimization of hydrooleophobic composition

Introduction. A high level of barrier and protective properties, resistance to moisture penetration (water, steam) and air resistance are the main requirements for packaging paper for food products. Problem. Polyvinyl alcohol-based polymer coatings are widely used for packaging paper; however, such coatings tend to have poor water resistance due to the hydrophilic and water-soluble nature of polyvinyl alcohol. Polyamide-epichlorohydrin resins are used to provide mois­ture resistance of the paper, and glycerol is used for the elasticity of the coating. At the same time, the complex effect of these components in the mixture for surface treatment of paper on the quality of the products has not been sufficiently investigated. Methods. Compositions based on aqueous solutions of polyvinyl alcohol brand 7/18 of the highest grade, polyamideamineepichlorhydrin EKA WS 325 and glycerol brand PK-94 were used to obtain a moisture-resistant, waterproof and fat-proof packaging material. Polyacryla­mide in the amount of 0.25 wt. % was used as a func­tional additive, a viscosity regulator of the com­position, and water was used as a solvent. Model compositions with different ratios of the main components in accordance with the central com­posite rotatable plan of the experiment were app­lied to the tests according to the methods adopted in the pulp and paper industry. STAT-SENS software was used for mathematical processing of the experimental results. A multi-criteria opti­mization method was used to find the optimal range of parameters of the hydrooleophobic composition. Results. The 15 model compositions have been developed. The influencing factors were the content of the polyvinyl alcohol, polyami­deamineepichlorhydrin, glycerol. The quality indi­cators of the treated paper-base were selected as the response functions of mathematical models: oil permeability, air permeability, destructive force, moisture resistance, surface absorption. Conclusions. The developed composition is optimal and makes it possible not to exceed its consumption during application to fibrous mate­rial, in particular paper. The composition pene­trates the thickness of the paper to an optimal depth evenly over the entire surface of the paper, which makes it possible to provide the paper with uniform barrier properties, mechanical strength and wet-strength along the plane of the canvas. In addition, glycerol gives elasticity to the resulting coating and prevents it from cra­cking during repeated bending.

An analytical method to quantitatively determine the amount of polyamide epichlorohydrin (PAE) in paperboard and white water

Polyamide epichlorohydrin (PAE) is a permanent wet strength resin. When applied to paperboard, some amount of resin is retained in the sheet, and some is lost to the white water. An analytical method for quantifying the amount of PAE retained in the sheet and lost into the white water has been developed. This method hydrolyzes the PAE to adipic acid, which in turn is derivatized to diethyl adipate and quantified by pyrolysis gas chromatography–mass spectrometry (pyGCMS). In addition, the hydrolysis conditions of the PAE were studied by the Taguchi approach, and PAE material balances around the dry sheet and white water for 3 and 6 lb/ton PAE applications have been performed. The PAE resin recovery was 95.4% with 65.0% in the sheet for the 3 lb/ton PAE-charged paper-board, and the recovery was 96.7% with 36.1% in the sheet for the 6 lb/ton PAE-charged paperboard.

Highly Strong and Damage-Resistant Natural Rubber Membrane via Self-Assembly and Construction of Double Network.

Natural rubber latex (NRL) is commonly employed to manufacture medical protective appliances. However, the characteristics of weakness and fragility of NRL membranes limit their further application. To achieve excellent strength and damage-resistance of the rubber membrane, this work reported a facile core–shell structure construction strategy via self-assembly with modified sodium lignosulfonate (MSLS) and NRL to create a tough membrane. The double network can be formed after introducing polyamide epichlorohydrin resin (PAE) into the NRL membrane. Specifically, the first robust MSLS-PAE network can break in advance to dissipate applied energy, thereby achieving high fracture energy and tensile strength of ~111.51 kJ m−2 and ~37 MPa, respectively, which overtakes numerous soft materials. This work facilitates more studies on latex/lignin-based products with high performance and good stability for the functional application of biopolymer.

Study on adhesive properties of soybean meal-based adhesives modified by ultrasonic-chemical treatment

In order to enlarge the industrial applications of wood products made with soybean meal-based adhesive (SMA), ultrasonic and chemical treatment of soybean protein derived from soybean meal (SM) to improve the wet shear strength of the plywood panels bonded was carried out. Chemical modifiers zinc oxide (ZnO) and polyamide epichlorohydrin resin (PAE) were added to SM to enhance the effect of ultrasonic modification. The purpose was to optimize chemical and ultrasonic modification factors, in order to maximize the water resistance under optimal modification conditions. Results indicated that under the optimal conditions, the wet shear strength of an SMA reached as high as 1.21 MPa, which was higher than the China National Standard for interior use of plywood (≥0.70 MPa) of 72.86%, and was higher than by chemical modification alone by 19%. The adhesion mechanisms involved were analyzed using scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results obtained reflected the synergy between ultrasonic treatment and chemical modification, revealing that the sonication process opens the spherical structure of the protein, allowing a more thorough chemical modification.

Determination of 1-chloro-2,3-epoxypropane in order to assess the working environment

1-Chloro-2,3-epoxypropane, known as epichlorohydrin (ECH), is a colorless liquid used in the production of epoxy resins, synthetic glycerine, elastomers, glycidyl ethers, surfactants, polyamide-epichlorohydrin resins and others. Epichlorohydrin may cause cancer. The aim of this study was to develop a new method for determining concentrations of ECH in workplace air in the range of 1/10-2 values of the maximum admissible concentration (MAC). The paper presents a method for the determination of ECH in workplace air using a gas chromatograph coupled with a mass spectrometer (GC-MS). The developed method is based on the adsorption of ECH on an activated charcoal, extraction with acetone, and a chromatographic analysis of the resulting solution. The method developed makes it possible to determine ECH in the concentration range of 0.1-2 mg/m3, i.e., 1/10-2 values of MAC established in Poland. The limit of detection (LOD) is 0.24 μg/m3 and the limit of quantification (LOQ) is 0.71 μg/m3. The method is characterized by good precision and accuracy; it meets the requirements of the European standard PN-EN 482, and can be used by occupational hygiene laboratories to measure concentrations of ECH in workplace air, with a view to assessing workers' exposure to this substance. Med Pr. 2020;71(6):715-23.

Strengthening of polyacrylonitrile (PAN) fiber networks with polyamide epichlorohydrin (PAE) resin

Polyacrylonitrile (PAN) fibers are one of the most important synthetic fibers that are widely studied because of their excellent characteristics, such as good mechanical strength, chemical resistance, and good thermal stability. Polyamide epichlorohydrin resin (PAE) is a type of cross-linking strengthening resins, with abundant active groups. However, the strengthening mechanism of polyamide epichlorohydrin resin (PAE) in synthetic fiber sheet is not clear. Herein, to meet the feasibility of some synthetic fiber sheet application, PAE resin reinforced polyacrylonitrile (PAN) fiber networks (PAE/PAN hybrid networks) were successfully prepared. Fourier transform infrared spectroscopy-attenuated total reflection (FTIRATR) spectroscopic and X-ray photoelectron spectroscopy (XPS) were used to characterize the self-cross-linking process which the formation of tertiary amine group in PAE/PAN hybrid networks boosted by the self-crosslinking of PAE polymer. The hot-pressing conditions, like temperature, time, and pressure, were also optimized. By adding low amount (0.6 wt%) of PAE serving as cross linkers, the density, tensile index, tear index, and elongation were increased by 9.6, 21.0, 25.8, and 34.3%, respectively. This work suggests a promising PAN fiber enhancement strategy with outstanding mechanical properties by adding PAE resin used as excellent self-cross-linking material and may have great practical application prospects in some other synthetic fiber sheets.

High wet-strength, thermally stable and transparent TEMPO-oxidized cellulose nanofibril film via cross-linking with poly-amide epichlorohydrin resin

TEMPO-oxidized cellulose nanofibrils (TOCNs) films cross-linked with different dosages of polyamide epichlorohydrin resin (PAE) show a great water-resistance and thermal stability.

Dual Mechanism of Dry Strength Improvement of Cellulose Nanofibril Films by Polyamide-epichlorohydrin Resin Cross-Linking

The chemical and physical properties of cellulose nanofibril (CNF) films cross-linked with wet strength cross-linker polyamide-epichlorohydrin resin (PAE) were investigated. In addition to the expected wet strength improvement, a unique stress–strain behavior for dry cross-linked films was observed. This stress–strain behavior indicates that varying stress-bearing mechanisms arise from the formation of new bonds caused by cross-linking at different levels of cross-linker addition. Cross-linked films showed an approximate 150% increase in dry strength, when compared to non-cross-linked CNF films. The cross-linked films showed a transition of both surface and bulk properties from hydrophilic to hydrophobic. The water contact angle increased from 50° to 110°, while the water retention value decreased by approximately 25% for the cross-linked films. Moreover, water vapor permeability also showed a 2-fold decrease. Possible mechanisms for the changes in behavior are discussed in detail.

Modification of cotton to improve its dyeability. Part 3 – polyamide–epichlorohydrin resins and their ethylenediamine reaction products

The effect of pretreating cotton with a polyamide–epichlorohydrin resin and ethylenediamine is described. The treated substrate has enhanced substantivity for reactive dyes, which may be applied without electrolyte simply by setting the dyebath to pH 5 and raising the temperature to the boil. Dyed samples exhibit good brightness and very high wash fastness, but in many cases the light fastness is impaired.

Modification of cotton to improve its dyeability. Part 2 – pretreating cotton with a thiourea derivative of polyamide–epichlorohydrin resins

A new method of pretreating cotton to improve its dyeability, using an aqueous solution containing polyamide–epichlorohydrin (PAE) resin and thiourea is introduced. The effect of dyebath pH on the colour yield, fixation and build–up of Procion HE, H and MX (ICI) dyes on the pretreated cotton, together with the quality of the dyeings obtained when using the new method and mechanistic implications, are discussed.

Dyeing Properties of a Polyamide–Epichlorohydrin Resin

The dyeing behaviour of cured films prepared from a polyamide–epichlorohydrin resin (Hercosett) was examined in orderto obtain a better understanding of the dyeing beha viour of Hercosett–treated wool. The polymer films swell by 500–1000%. The swelling decreases with increasing dye content in the polymer and with increasing temperature. The diffusion of acid dyes into the polymer is extremely fast (D =10‐7 cm2/s), and can be accelerated by the addition of salt. The sorption of the dye is described in terms of a Langmuir isotherm, indicating that an ion–exchange mechanism is operative. The concentration of cationic groups in the polymer is very high (2. 4mo//kg) and does not depend on the curing conditions. The addition of salt reduces the exhaustion of the dyebath. Reactive dyes were found to be bound covalently to the resin. During industrial resin treatment it has been shown that the molecular weight distribution of the Hercosett in the resin bath changes markedly, molecular weight increasing with running time and the spread of values being much narrower. This may explain the variation in the dyeing behaviour of wool fibres that have been treated at different times in the same resin bath.

The chemistry of a polyamide–epichlorohydrin resin (hercosett 125) used to shrink‐resist wool

AbstractA polyamide–epichlorohydrin resin used to shrink‐resist wool [Hercosett 125 (Hercules Inc.)] was separated by ultrafiltration into fractions A, B, and C (in the approximate proportions 60, 40, and 2 by weight), which correspond to the three peaks in size exclusion chromatograms (SEC). Viscosity, spectra, and SEC results as well as results of experiments on the reaction of the parent polyamino–polyamide (PAA) with epichlorohydrin indicated that fraction A was high‐molecular‐weight crosslinked material whereas fraction B was essentially uncrosslinked. Fraction C was minor impurity, possibly a mixture containing a triazine, and it was also found in the PAA from which the original resin was prepared. High‐resolution proton NMR spectra of the Hercosett 125 indicated that chlorohydrin or epoxy groups were absent, and thus confirmed an earlier 13C‐NMR study that only azetidinium reactive groups were present. Two reactions are believed to occur in Hercosett 125 on storage: hydrolysis of azetidinium to dihydroxypropyl groups and hydrolysis of backbone amides. The small differences in the properties of wool treated with either A or B fractions, and those of wool treated with unfractionated Hercosett 125, were related to the extent of crosslinking before and after curing. As the extent of crosslinking increased, the amount of staining by an anionic dye decreased, and the shrink resistance improved slightly.

Gel permeation chromatography of a polyamide—epichlorohydrin resin and some other cationic polymers

The gel permeation chromatography of cationic polymers, a polyamide—epichlorohydrin resin (Hercosett 125), poly(2-vinylpyridine) and polyethyleneimine, was compared on a selection of silica gel columns with neutral and cationic surface modifications. The elution volumes of the polymer peaks were very dependent on the pH, ionic strength and the column, but were also influenced by the type of salts in the eluent and the polymer concentration. In some cases it was possible to elute the cationic polymer anywhere between the high-molecular-weight exclusion limit and the low-molecular-weight total permeation limit. The polymer peak in Hercosett 125 split into two under certain conditions. This appears to be related to the presence in Hercosett 125 of polymers of different structures. Universal calibration methods and viscosity measurements have been used to indicate conditions where interaction between the cationic polymers and the columns and/or solvent was minimal and these conditions have been used to estimate the molecular weight of Hercosett 125.