Peanut meal as plywood adhesives: preparation and characterization

Bio-based adhesives have attracted much attention due to its renewable and environment-friendly properties. This study describes a route for the preparation of a new bio-based adhesive from peanut meal. For this purpose, different types of raw materials (hot-pressed peanut meal and cold-pressed peanut meal) were compared. Moreover, the crushing methods and modification agents were investigated in great details. Furthermore, response surface methodology was applied to optimize the preparation conditions of peanut meal adhesive. The apparent viscosity and the Fourier transform infrared spectroscopy (FITR) of peanut meal adhesives were also evaluated to confirm the validity of the optimal preparation conditions. These results showed that hot-pressed peanut meal is a good candidate for adhesive materials and the addition of sodium dodecyl sulfate (SDS) improves the adhesive bonding strength. In addition, the regression model for the peanut meal adhesive preparation revealed statistical significance. Modification time and material liquid ratio had a significant effect on wet strength while the variables of modification temperature and the addition amount of modifier were insignificant. The optimal preparation conditions were determined as follows: modification temperature of 60?°C, modification time of 3?h, ratio of material to liquid of 1:3 and the addition amount of modifier of 3.2%. The average value of the adhesive bonding strength of 1.05?±?0.07?MPa was obtained, which is close to the predicted value. Under these conditions, the best wet strength and adhesive performance were achieved for the plywood.     

Plant Polyphenol-Inspired Crosslinking Strategy toward High Bonding Strength and Mildew Resistance for Soy Protein Adhesives

Soybean protein adhesives are environmentally friendly biomass-based aldehyde-free adhesives that have good economic value for the wood industry; however, it remains challenging to produce soybean protein adhesives with excellent water resistance, toughness, and mildew resistance through a simple modification method. In this work, inspired by plant polyphenols, a novel crosslinked soybean meal adhesive (SMPT) is obtained using a facile economic method. Polyamidoamine-epichlorohydrin (PAE) and tannic acid (TA) are combined with a soybean meal matrix to form a tough co-crosslinked network through strong intermolecular forces (covalent bonds, ionic bonds, and hydrogen bonds) in adhesive system. The results show that the wet bonding strength of SMPT adhesives for plywood is 134.1% higher than the unmodified soybean meal adhesive. The adhesion properties met the standard requirements for interior-use plywood. And the compact cross-linking network structure is accelerated the greater energy dissipation, which improves the toughness of adhesive. Moreover, cationic azetidinium groups in PAE and phenol hydroxyl groups in TA synergistically not only exhibit the good antibacterial activities but also improve mildew resistance for SMPT adhesives. This facile strategy provides an economic sustainable method to prepare high-performance environmentally friendly wood adhesives.     

Rubber solution adhesives for wood-to-wood bonding

Rubber solutions were prepared and used for bonding wood pieces. The effect of the variation of chlorinated natural rubber (CNR) and phenolformaldehyde (PF) resin in the adhesive solutions on lap shear strength was determined. Natural rubber and neoprene-based adhesive solutions were compared for their lap shear strength. The storage stability of the adhesive prepared was determined. The change in lap shear strength before and after being placed in cold water, hot water, acid, and alkali was tested. The bonding character of these adhesives was compared with different commercially available solution adhesives. The room-temperature aging resistance of wood joints was also determined. In all the studies, the adhesive prepared in the laboratory was found to be superior compared to the commercial adhesives. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1185–1189, 1998     

One-year bonding performance of one-bottle etch-and-rinse adhesives to dentin at different moisture conditions

Abstract

This study aimed to investigate the one-year bond strengths to dentin of one-bottle etch-and-rinse adhesive systems applied under different moisture conditions. Class V cavities were prepared in bovine incisors and randomly allocated (n?=?8) according to the type of adhesive system used – SB (Adper? Single Bond 2); PB (Prime & Bond 2.1); and XPB (XP Bond) – and the moisture condition kept in the cavity – moist, over-wet, and over-dry. Filtek? Z250 was used for teeth restoration. Specimens for microtensile bond strength (µTBS) test were obtained and stored in water for 24?h or 1?year, and submitted to mechanical testing. Data were analyzed using t-tests, ANOVA and the Holm–Sidak post hoc test (α?=?0.05). Weibull analysis was used to verify the reliability of specimens. The type of adhesive and the moisture condition of the substrate affected the µTBS. At 24?h, SB performed better under the moist and over-wet conditions. At 1?year, SB, PB, and XPB showed the greatest percentage reduction at the moist (～38%), over-wet (100%), and over-dry (100%) conditions, respectively. The reliability of adhesives was affected by the variable factors tested. In conclusion, the solvent composition of adhesives and the moisture condition of the substrate play an important role in the bond strength and bonding stability of resin-based restorations, as well as on the reliability of the adhesive interfaces over time.     

Bond durability of contemporary universal adhesives: effect of dentin treatments and aging

The aim of this in vitro investigation was to evaluate the effects of different dentin treatments on µTBS values of three different universal adhesives. Sixty extracted bovine incisors were used. The teeth were horizontally sectioned from the enamel-cement junction and embedded in an acrylic resin. Enamel was removed with 180-grit SiC paper to expose dentin. The exposed dentin surfaces were further polished with 600-grit SiC paper to provide a standardized smear layer. Teeth were randomly divided into three groups, according to the universal adhesives: All-Bond Universal, Single Bond Universal, and G-Bond Plus. Each group was then assigned into four subgroups, according to the dentin treatments: etch-and-rinse mode (ER), ER + 2% chlorhexidine (CHX), ER + %2.5 genipin (GE), and self-etch mode (SE). Samples were longitudinally sectioned across the bonded-interfaces to obtain resin-dentin beams. Beams were prepared from the same teeth were randomly and equally divided into two groups: immediate µTBS testing and µTBS testing after 6-month. The failure loads were recorded in MPa, and failure modes were evaluated at 30× magnification. The data were analyzed using a two-way ANOVA, to determine the effects of dentin treatment and storage time, and the interaction of these two factors on the µTBS of universal adhesives. Dentin treatments were showed significant differences (p?<?0.05). ER mode exhibited higher µTBS than SE mode. However, universal adhesives were more durable in the SE mode than ER mode. Also, chlorhexidine treatment significantly improved adhesive performance of all universal adhesives, while no significant improvement was detected with genipin treatment.     

Protein concentrate and adhesives from meat and bone meal

Defatted meat and bone meal (MBM) was prepared by the removal of extractable fat with isopropyl alcohol. Proteins in the defatted MBM were extracted with 0–4% NaCl concentrations with 0.05% CaCl₂ or 0.05% MgCl₂ at pH 5.5–6.6 for 1 h at 50°C and precipitated at pH 4.0–4.5. By using the salt extraction procedure, MBM protein concentrate (MBMPC) (32 g) was obtained from defatted MBM (100 g). Recovery of protein was dependent on the extraction temperature employed; recovery values ranged from 33.2 to 51.4%. At 4% NaCl concentration, MgCl₂ increased protein solubility by 30%, compared to the control. The adhesiveness of MBMPC at various pH values ranging from 5.0 to 9.0 was investigated. At pH 6.0–8.0, adhesiveness of MBMPC showed the highest value (78.2 kg). The adhesiveness increased linearly as the MBMPC concentration increased up to 20% with respect to temperature for MBMPC adhesiveness, the greatest adhesiveness was in the range of 70 to 90°C. Improved adhesiveness and water resistance were observed with 0.05% glutaraldehyde treatment.     

Effect of different application techniques on microshear bond strength of self-etch adhesives to dentin

Objectives: To investigate the effect of different self-etch adhesive systems application techniques: active or passive in a single or double layer on adhesive–dentin microshear bond strength.

Methods: Occlusal surfaces of 48 extracted human molars were ground to expose flat superficial dentin surfaces. Specimens were randomly divided into two main groups according to the tested self-etch adhesive system either: One-step self-etch (Adper^TM easy-one) or two-step self-etch (Adper^TM SE Plus). Each adhesive system was applied on the prepared dentin surfaces followed one of these techniques: (1) Passive application of a single layer, (2) Active application of single layer, (3) Passive application of double adhesive layer (with light curing in between), and (4) Active application of double adhesive layers. Resin composite was packed inside micro-tubes fixed on the bonded dentin surfaces and light cured for 40 s. All specimens were stored in artificial saliva either for 24 h or 3 months before testing. Microshear bond strength test was employed using a universal testing machine at a crosshead speed of 0.5 mm/min.

Results: Adper^TM SE Plus showed higher significant microshear bond strength in compared with Adper^TM easy-one. For both adhesive systems active application showed higher significant microshear bond strength to dentin than passive application. Double application of adhesive systems showed lower microshear bond strength than single application.

Conclusion: Active application of self-etch adhesives could improve the dentin microshear bond strength. Double application with curing in between the layers did not improve the bond strength to the tested adhesive.     

Studies on wood-to-wood bonding adhesives based on natural rubber latex

Natural rubber latex-based adhesives were prepared for wood-to-wood bonding. The effects of prevulcanization, and varying amounts of ammonium caseinate, carboxymethyl cellulose, cooked starch, and phenol formaldehyde resin on adhesion were studied. The water resistance of the bonds was tested in cold and hot water and was found to be superior compared with commercial latex-based adhesives.     

Prime-and-rinse approach for improving the enamel micro-tensile bond strengths of self-etch adhesives

The study investigated the effects of prime-and-rinse approach using 15% MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer on the enamel micro-tensile bond strengths (MTBS) of (ultra-) mild self-etch adhesives, enamel surfaces and enamel-resin interfaces. The buccal enamel surfaces of 69 human third molars were polished and randomly assigned to three groups: Group A (control, self-etch approach): Polished enamel surfaces were not further pre-treated. The enamel surfaces were acid-etched (Group B, (selective) enamel etching) or primed with 15% MDP-containing primer (Group C, prime-and-rinse approach) for 15?s and thoroughly water-sprayed. The enamel surfaces were applied with self-etch adhesives and placed with composite resins (Adper Easy One?+?Filtek Z350 (3?M ESPE); Clearfil S3 Bond?+?Clearfil Majesty (Kuraray-Noritake Co.); G Bond?+?Gradia Direct (GC); iBond?+?Charisma (Heraeus-Kulzer)), respectively. The specimens were prepared for MTBS test and scanning/transmission electron microscopy observations. Compared with group A, groups B and C produced significantly higher enamel MTBS (p?<?.01), regardless of the adhesives used. Groups B and C possessed similar enamel MTBS (p?>?.05). The SEM findings showed that smear layer remained on the polished enamel surface was completely removed by acid etching and almost completely removed by prime-and-rinse approach. The TEM microphotographs reveal that smear layer was detectable at the resin-enamel interface in group A, not in groups B and C. The novel prime-and-rinse approach using MDP-containing primer before the application of (ultra-) mild self-etch adhesives could greatly increase the enamel MTBS. That might be an alternative to selective enamel etching.     

Initial evaluation of novel polyamide-imides and their copolymers as adhesives

—An adhesive screening study was performed at NASA Langley Research Center on two linear aromatic polyamide-imide (PAI) homopolymers and two linear aromatic PAI copolymers. The homopolymers were made with either of two amide diamines, 3,3'- or 4,4'-diaminobenzanilide (DABA), and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA). The two copolymers studied were prepared with a combination of 3,3'-DABP and amide diamines. These aromatic PAIs possess high thermal stability because of intermolecular hydrogen bonding and chain stiffness. Lap shear strength (LSS) tests, conducted at room temperature, 177, 204 and 232°C, were the primary criterion for evaluation of the polymers as adhesives. Included in the study were measurements of the glass transition temperature made on fractured specimens for each bonding condition and a visual determination of the type of bond failure for specimens at each test temperature. Of the four adhesive candidates investigated, the best LSS values were obtained with the PAI copolymer identified as LARC-TPI(25% 3,3'-DABA). However, the LSS values were higher for the LARC-TPI polyimide with which the adhesive strengths were compared. The combination of a high molecular weight and the increased interchain electronic interaction associated with the amide group appears to contribute to the poor flow properties observed.     

Preparation and characterization of one-component polyurethane powder adhesives by the solution polymerization technology

A new technology integrating the synthesis and granulation was adopted to prepare the one-component polyurethane powder adhesives (PPAs) by the solution polymerization. The influence of R_total, neutralization, and types of dispersion solution on the properties of PPAs was investigated. It was found that the initial melting temperature increased and storage stability decreased with increasing R_total. The neutralization reaction between the carboxylic group and amino group made the reduction of the sizing temperature and the increase of the T-peel adhesion strength. The granulation behaviors of the polyurethane (PU) prepolymer under different dispersion solutions showed that the PU prepolymer can be effectively blocked by the 20–30 wt % NaHSO₃ or n-butyl alcohol. Furthermore, the blocked polymers formed small particles with the ideal sizing temperature and peel strength. The excellent adhesive property and thermal stability of PPAs could meet the requirements of the industrial gluing in the fields of packaging, lining, and footwear. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47898.     

Asphaltenes as a tackifier for hot-melt adhesives based on the styrene-isoprene-styrene block copolymer

The use of heavy crude oil asphaltenes and resins (termed asphaltenes) as the components of hot-melt adhesives based on the styrene-isoprene triblock copolymer was considered. The rheological, thermophysical, strength, and adhesive characteristics of the mixtures containing from 10 to 40 wt% of asphaltenes were studied. The addition of 10 to 20 wt% of asphaltenes enhanced the strength and adhesive properties of the mixtures and only slightly changed their rheology. The higher concentrations of asphaltenes reduced the viscosity of the mixtures but did not lead to improved characteristics of the adhesives. The ambiguous effect of asphaltenes is probably due to their uneven distribution between the microphases of the block copolymer as well as their ability to act both plasticizers and reinforcing particles depending on temperature. A comparison of asphaltenes and conventional tackifiers based on hydrocarbon resins revealed their comparable effect on the properties of the block copolymer.     

Efficacy of different surface treatments and universal adhesives on the microtensile bond strength of bulk-fill composite repair

Abstract

The purpose of this in vitro study was to evaluate the influence of different surface treatments and aging on the microtensile bond strength (μTBS) of bulk-fill composite resins. Bulk-fill composites (Filtek One; 3M ESPE) randomly received five different surface treatments: (1) no treatment, control, (2) 37% phosphoric acid etching (PA), (3) 9% hydrofluoric acid etching (HF), (4) air-borne particle abrasion with 50-μm alumina particles (Al₂O₃), (5) tribochemical silica coating (CoJet). Following, the specimens were divided into three subgroups according to universal adhesive applied: Clearfil Universal Bond (CU; Kuraray), Prime&Bond Universal (PBU; Dentsply Sirona), or Single Bond Universal (SBU; 3M ESPE). A nanofill composite (Filtek Ultimate; 3M ESPE) was employed as a repair. Bonded specimens were stored in water for 24?h at 37?°C or thermal aged, then subjected to the μTBS test. Additionally, specimens were analyzed with a contact profilometer and were evaluated with scanning electron microscopy. Control and PA treatments were showed the lowest µTBS (p?<?0.05), and there was no significant difference between these two groups (p?>?0.05). Al₂O₃ and CoJet treatments generally exhibited a similar influence on µTBS values. In addition, a correlation was found between surface roughness and bond strength (r?=?0.831). CoJet resulted in significantly higher repair µTBS values when compared to the other surface treatments. In addition, the use of silane-containing universal adhesive was increased the cohesive failure rate and maintained the repair µTBS values after thermocycling.     

Shear strength and water resistance of modified soy protein adhesives

Soy protein polymers recently have been considered as alternatives to petroleum polymers to ease environmental pollution. The use of soy proteins as adhesives for plywood has been limited because of their low water resistance. The objective of this research was to test the water resistance of adhesives containing modified soy proteins in walnut, maple, poplar, and pine plywood applications. Gluing strength and water resistance of wood were tested by using two ASTM standard methods. Glues with modified soy proteins had stronger bond strength than those containing unmodified soy proteins. Plywood made with glue containing urea-modified proteins had higher water resistance than those bonded with glues containing alkali-modified and heat-treated proteins. After three 48-h cycles of water-soaking, followed by 48 h of air-drying, no delamination was observed for either walnut or pine specimens glued with the urea-modified soy protein adhesives. Gluing strength for wood species with smooth and oriented surface structure was lower than for those with rough, randomly oriented, surface structures. Wood species with greater expansion of dimensions during water-soaking had a higher delamination rate than those showing less expansion.     

Soy flour dispersibility and performance as wood adhesive

Soy flour adhesives using polyamidoamine-epichlorohydrin (PAE) resin as the curing agent are being used commercially to make bonded wood products. The original studies on the soy-PAE adhesives used purified soy protein isolate, but the much lower cost soy flour is now used commercially. We examined the performance of commercially available soy flours that have their proteins either mainly in their native (90 protein dispersibility index (PDI)) or denatured (70 and 20 PDI) states. We expected that the more native state soy proteins with their better dispersibility would provide better adhesion to wood surfaces and enhanced reaction with PAE resin. Small-scale wood bonding tests showed that neither of these effects was observed without and with a low level of PAE. In these tests, the solids content of the soy formulations had a large influence on adhesive viscosity but little influence on bond strength. Additionally, little difference was observed in any of the adhesive or viscosity properties between the soy flours having either a 0.152 or 0.075?mm (100 or 200 mesh) particle size.     

Effects of phosphorus-containing additives on soy and cottonseed protein as wood adhesives

Soy and cottonseed proteins appear promising as sustainable and environment-friendly wood adhesives. Because of their higher cost relative to formaldehyde-based adhesives, improvement in the adhesive performance of proteins is needed. In this work, we evaluated the adhesive properties of soy and cottonseed protein formulations that included phosphorus-containing acids and esters. For cottonseed protein isolate, most of these additives improved dry adhesive strength, with methylphosphonic acid, phosphorous acid, and phosphoric acid increasing the dry strength by 47, 44, and 42%, respectively, at their optimal concentrations. For soy protein isolate, these additives did not show significant benefits. The phosphorus-containing additives also improved the hot water resistance of the cottonseed protein formulations but showed either no effect or a negative effect for the of soy protein formulations. Thus, the combination of cottonseed protein with phosphorus additives appears to be attractive as wood adhesives.     

水性聚氨酯压敏胶的合成及其性能表征

以异佛尔酮二异氰酸酯(IPDI)、聚醚多元醇(N220、N210)、二羟甲基丙酸(DMPA)和三羟甲基丙烷(TMP)为主要原料制得了环保交联型水性聚氨酯(WPU)压敏胶,讨论了n(-NCO)/n(-OH)比值、交联剂用量以及聚醚相对分子质量大小对该压敏胶性能的影响。研究结果表明,由N220合成的WPU压敏胶的初粘力优于由N210合成的WPU压敏胶;随着n(-NCO)/n(聚醚中-OH)比值的减小,压敏胶的初粘力提高,持粘力呈先降后增再降的趋势;适度的交联可以提高压敏胶的粘接强度;当n(-NCO)∶n(聚醚中-OH)为2.5∶1、n(TMP中-OH)∶n(聚醚中-OH)为1∶3.0时,压敏胶的综合性能优异,初粘力达到13号钢球,持粘力达到23.1h,180°剥离强度达到20.14N/(20mm)。     

Study of glycidyl ether as a new kind of modifier for urea‐formaldehyde wood adhesives

In this work, the multiepoxy functional glycidyl ether (GE) modified urea‐formaldehyde (UF) resins were synthesized via a traditional alkaline‐acid process under low formaldehyde/urea (F/U) molar ratio. The synthesized resins were characterized by ¹³C magnetic resonance spectroscopy (¹³C‐NMR), indicating that GE can effectively react with UF resins via the ring‐opening reaction of epoxy groups. Moreover, the residual epoxy groups of GE could also participate in the curing reaction of UF resins, which was verified by Fourier transform infrared spectroscopy. The storage stability of GE‐modified UF resins and the thermal degradation behavior of the synthesized resins were evaluated by using optical microrheology and thermogravimetric analysis, respectively. Meanwhile, the synthesized resins were further employed to prepare the plywood with the veneers glued. For the modification on bonding strength and formaldehyde emission of the plywood, the influences of addition method, type, and amount of GE were systematically investigated. The performance of UF adhesives were remarkably improved by the modification of GE around 20–30% (weight percentage of total urea) in the acidic condensation stage during the resin synthesis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and application of some oligopolyamines as adhesives for road bitumens

By the amination of a fraction of n‐polychloroparaffins (C_13–19) with 1,2‐ethylenediamine in a basic medium, oligopolyamines were obtained. The obtained products were characterized with spectroscopic, titrimetric, and elemental analyses and tested as adhesives for road bitumens. The samples, containing over 7.0% bound nitrogen in a concentration of 1.0 mass % with respect to the bitumen mixtures, were characterized by maximum effectiveness, that is, 100% adhesion between the bitumen and the mineral fillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Jet cooking dramatically improves the wet strength of soy adhesives

The impact of jet cooking on shear strength of soy-and-water adhesives was investigated to understand the higher shear strength of commercial soy protein isolates compared to soy flours. Soy flour-based wood adhesives are appealing because of their bio-based content, low formaldehyde emission, and low cost, but their commercial application is limited by low wet cohesive strength. Previous researchers proposed that the process of jet cooking (steam injection with high turbulence followed by rapid cooling) was responsible for the high (~3 MPa) wet shear strength of adhesives made with commercially produced soy protein isolate, using the ASTM D 7998 test. In this work, we show that jet cooking did dramatically increase the wet strength of laboratory-produced, native-state soy protein isolate from 0.6 to 3 MPa, a strength similar to many commercial isolates. Jet cooking was far less effective at developing wet strength of soy flours, but greatly increased the viscosity of virtually all our soy materials. We hypothesize that the benefits of jet cooking are primarily a result of nonequilibrium protein aggregation states because subsequent wet autoclaving of jet cooked soy proteins dramatically decreased wet strength. The dramatic differences in adhesive properties between commercial soy protein isolates and soy flours suggests that the common practice of using results obtained with commercial isolates to predict the performance of soy flour adhesives is inappropriate.