Isocyanate Resin Research Articles

Study of Coupling Agent on Properties of Wheat Straw/pp Composite

With malefic anhydride chose as coupling agent, Wheat straw and recycled Polypropylene (PP) was used as the main row material and compounded by isocyanate resin though the hot press technics. The effects of coupling agent on mechanical property of wheat straw/PP composite were studied by orthogonal experiments. The results showed that, if only coupling agent was used, it may have effects on composite, but the properties of composite were poor. If both of MDI and coupling agent were used, it would decrease the effects of MDI resin.

SYNTHESIS AND PROPERTIES OF WATERBORNE POLYURETHANES MODIFIED BY EPOXY RESIN

A series of anionic waterborne polyurethane emulsion modified by epoxy resin were successfully prepared by the reaction of polycaprolactone diols(CAPA),isophorone isocyanate(IPDI),hexamethylene-1,6-diisocyanate(HDI) and epoxy resin(E-44) as crosslinker.Solidified films of the waterborne polyurethane were prepared by casting emulsions on Teflon surfaces.Fourier transform infared spectrometer(FTIR) and thermogravimetry analysis(TGA) were used to characterize the structure of the polyurethane.The mechanical properties and water contact angle of the cast films were also measured.The surface roughness and surface morphology of the films of waterborne polyurethanes were observed by atomic force microscopy(AFM).The particle size and distribution of the resultant polymer emulsions was tested by the dynamic laser light scattering(DLLS).FTIR indicates that epoxy group and hydroxyl group of E-44 both reacted with the polyurethane prepolymer.TGA indicates that the crosslink of E44 with polyurethane increased thermal stability of the modified polyurethanes.It was found that the tensile strength of films of modified polyurethane increased and the elongation at break decreased with increasing E-44 content,the water contact angle increases with increasing w(E-44),the smoothness of solidified films of waterborne polyurethane decrease when modified by E-44,resulting in water repellence functions.DLLS showed that the particle size of emulsion increased with increasing w(E-44).In order to obtain stable polyurethane emulsions and solidified films of waterborne polyurethanes with improved mechanical properties,the proper w(E-44) is 10%.

Polyurea based aerogel for a high performance thermal insulation material

Less fragile lightweight nanostructured polyurea based organic aerogels were prepared via a simple sol–gel processing and supercritical drying method. The uniform polyurea wet gels were first prepared at room temperature and atmospheric pressure by reacting different isocyanates with polyamines using a tertiary amine (triethylamine) catalyst. Gelation kinetics, uniformity of wet gel, and properties of aerogel products were significantly affected by both target density (i.e., solid content) and equivalent weight (EW) ratio of the isocyanate resin and polyamine hardener. A supercritical carbon dioxide (CO2) drying method was used to extract solvent from wet polyurea gels to afford nanoporous aerogels. The thermal conductivity values of polyurea based aerogel were measured at pressures from ambient to 0.075 torr and at temperatures from room temperature to −120 °C under a pressure of 8 torr. The polyurea based aerogel samples demonstrated high porosities, low thermal conductivity values, hydrophobicity properties, relatively high thermal decomposition temperature (~270 °C) and low degassing property and were less dusty than silica aerogels. We found that the low thermal conductivities of polyurea based aerogels were associated with their small pore sizes. These polyurea based aerogels are very promising candidates for cryogenic insulation applications and as a thermal insulation component of spacesuits.

Parallel Synthesis of Trisubstituted Formamidines: A Facile and Versatile Procedure

A focused library of formamidines having several diversity points has been prepared. The use of isocyanate resin as scavenger may offer several practical advantages over conventional procedures, such as the ease of workup and availability. The technique described herein was performed in a parallel synthesis format. The whole protocol has potential use in high throughput synthesis for the preparation and purification of libraries of unsymmetrical formamidines containing sets of different aliphatic substituents.

Durability of isocyanate resin adhesives for wood V: changes of color and chemical structure in photodegradation

The effect of ultraviolet (UV) light irradiation on the color and chemical structure of water-cured polymeric diphenylmethane diisocyanate (PMDI) was investigated using a UV long-life fade meter. Control treatment was performed without UV light irradiation using a thermohygrostat for comparison. Two kinds of resin were used in this study: that to which only water had been added, and resin to which a small amount of polyol and water had been added. In addition, lauan (Shorea spp.) wood was used as a reference. The photodegradation of the resins over a period of up to 300 h was observed using a colorimeter and Fourier transform infrared (FT-IR) spectroscopy. When the resins were treated with UV light, the color difference (ΔE * ab) of the resins increased signifi cantly in a short time, and then reached a near-constant value. For lightness, L * decreased rapidly for a few hours and then decreased gradually. The color darkened compared with that of the wood used. When treatment was performed without UV light irradiation, ΔE * ab and ΔL * of the resins showed negligible change. Based on the results of FT-IR analysis, severe degradation such as cleavage of the main chemical bond was hardly observed under UV light irradiation irrespective of the type of resin.

Solution-Phase Parallel Synthesis of Carbamates as γ-Secretase Inhibitors

A novel methodology for parallel liquid-phase synthesis of carbamates suitable for the preparation of sterically hindered molecules is disclosed. The alcohols are converted to 4-nitrophenylcarbonates, followed by the reaction with amines. Side product 4-nitrophenol and the unreacted excess amines are scavenged by appropriately chosen cleanup resins, selected among Amberlyst A26 (hydroxide form) and macroporous sulfonic acid (MP-TsOH) or polystyrene isocyanate (PS-NCO) and polystyrene benzaldehyde (PS-PhCHO) resins. As a part of a medicinal chemistry program directed toward finding gamma-secretase inhibitors as prospective drug candidates for Alzheimer's disease, a 6 x 24 library of carbamates was prepared. Out of 144 library members, 133 had a purity for the targeted compound of 80% or better. The prepared compounds were assessed in the gamma-secretase inhibition assay and demonstrated activity with IC 50 values in the range from 1 microM to 5 nM, with the activity of 7 compounds being better than 10 nM.

Fire-retardant-treated low-formaldehyde-emission particleboard made from recycled wood-waste

The objective of this study was to manufacture fire-retardant-treated low-formaldehyde-emission particleboard from recycled wood-waste particles using polymeric 4,4′-methylenediphenyl isocyanate (PMDI) and phenol-formaldehyde (PF) resins. The influence of the PMDI/PF ratio (ratio of particles sprayed with PMDI to particles sprayed with PF, w/w) after fire retardant treatment on formaldehyde emissions, mechanical properties, and surface fire resistant performance of the manufactured particleboard was investigated. The experimental results showed that the formaldehyde emissions linearly decreased with an increasing PMDI/PF ratio. Moreover, the bending strength, internal bond strength, and screw holding strength increased with an increasing PMDI/PF ratio. The thickness swelling of the particleboard was improved by using an increasing PMDI/PF ratio. Furthermore, the fire-retardant-treated low-formaldehyde-emission particleboards fabricated in our study could pass the third grade standard of surface fire resistant performance as specified by CNS 6532.

Experimental Particleboard Made from Wood-Bark Mixtures and Bonded with EMDI Resin

AbstractExperimental one layer experimental particleboards were made with various wood: bark mixtures, using EMDI isocyanate resin. The results showed that particleboards made from 75:25 wood: bark mixture conformed to the more stringent requirements of class M-3, while boards made from 50:50 wood: bark mixture were in accordance with the ANSI standard particleboards of class M-2.

Properties of low-formaldehyde-emission particleboard made from recycled wood-waste chips sprayed with PMDI/PF resin

The objective of this study was to manufacture low-formaldehyde-emission particleboard from recycled wood-waste chips using polymeric 4,4′-methylenediphenyl isocyanate (PMDI) and phenol-formaldehyde (PF) resins for use in indoor environments. The influence of PMDI/PF ratios in particles on the formaldehyde emission and its mechanical properties were investigated. The experimental results showed that the formaldehyde emission released decreased linearly with increasing PMDI/PF particle ratio. The relationship could be represented by a linear regression formula. Formaldehyde emission was below 0.3mg/L when the weight percentage of PMDI/particles was up to 70%. The formaldehyde emission from melamine-formaldehyde (MF) resin-impregnated paper-overlaid particleboard was 17% lower than that for particleboard. Moreover, the bending strength, internal bonding strength and screw holding strength increased with increasing PMDI/PF particle ratio. However, the percentage thickness swelling of the particleboard decreased with increasing PMDI/PF particle ratio. In addition, there were significant positive relationships between the ultrasonic velocity and the bending strength, internal bonding strength and screw holding strength of the particleboard, which allowed evaluation of the properties of the particleboard using ultrasonic velocity.

Cure chemistry of wood/polymeric isocyanate (PMDI) bonds: Effect of wood species

The wood-species dependent performance of polymeric isocyanate resin (PMDI) was investigated by fracture analysis and solid-state NMR. The fracture performance of two different woods (yellow-poplar and southern yellow pine) bonded with PMDI was evaluated using mode-I cleavage. The fracture toughness of pine samples was significantly greater than the corresponding yellow-poplar samples. Separately, the cure chemistry of wood/PMDI bondlines was investigated by solid-state NMR with nitrogen-labeled (N 15) resin, and by employing spectral decomposition of the complex resonance arising from protonated nuclei. A small but statistically significant species effect was found in both the cure chemistry and in the proton rotating-frame relaxation for samples cured at lower temperatures. These differences were not found at higher cure temperatures. This suggested that a species effect might arise in the core of commercial wood-based composite panels, where lower cure temperatures are found. Wood acetylation altered the wood-PMDI cure chemistry by reducing the relative signal intensity in the urethane spectral region by 35%. However acetylated wood specimens still exhibited significant N 15 signal in the urethane spectral region. Since little or no urethane was expected from acetylated samples, an unequivocal urethane detection remains elusive, and if it is detected its occurrence was grossly overestimated by the spectral decomposition employed in this work.

Durable adhesives for large laminated timber

Large laminated timber (LT) made of hardwood is widely used as the main constitutional element of goods such as furniture, pianos and doors. A high durability of LT is essential to these products. This study focused on finding as to what adhesives were acceptable as highly durable adhesives for LT. Twelve different adhesives such as resorcinol-formaldehyde resin, aqueous emulsion-type isocyanate resin, poly(vinyl acetate) emulsion, epoxy resin, etc. were used. The durability of LT, i.e., the percentage of delamination length of LT under tests such as humidity and temperature cycling tests, and outdoor tests, was discussed in relation to the adhesive shear strength of a lap joint (LJ). The results showed that the percentage of delamination length under both low −20°C for 16 h and high-temperature 50°C for 8 h cycling tests (temperature-resistance) on LT indicated a strong trend with the adhesive shear strength of the LJ exposed to dry air at 100°C for 24 h. In addition, the percentage of delamination length under outdoor exposure test for three months (outdoor-resistance) of the LT showed a trend with the adhesive shear strength of the LJ exposed to dry air at 100°C for 24 h, as well as with the adhesive shear strength of the LJ immersed in water at 60°C for 3 h. These trends pointed out that the thermal stability of the adhesive from −20°C for 16 h up to 50°C for 8 h was an important parameter in order to improve adhesive durability for the LT.

Bonding behaviour of chemically modified wood particles for board production

The objective of this paper was to evaluate the bonding behaviour of chemically modified wood particles towards an isocyanate resin system, as determined from internal bond strength of the board, and to determine which resin system, isocyanate or formaldehyde is suitable for use in boards made from modified raw material. It was found that chemical modification of wood chips and strands did not significantly affect the bonding efficiency of isocyanate resin, but the bonding efficiency of formaldehyde resins was strongly influenced. This behaviour can be a consequence of the usage of a less pH dependent resin that is fully cured during hot pressing in combination with the high mobility of the resin which causes penetration to considerable depth into compressed particles repairing weak zones, which are created during the modification process as chips are exposed to elevated temperatures, by sticking them together. It is suggested therefore, that the isocyanate resin system is more suitable for use in boards made from modified raw material than the formaldehyde resin system.

Rapid access to reactive polymer-supported isocyanates

Isocyanate resins are used in polymer assisted solution-phase synthesis, however, their use is limited by their high cost and often unfavourable reaction profiles. Here a route to prepare efficient supported isocyanate resins from aminomethyl resin and inexpensive diisocyanates is reported and compared to commercially available isocyanate resins.

Veneer strand flanged I-beam with MDF or particleboard as web material II: effect of resin type, application rate, strand dimension, and pressing time on the basic properties

Optimization of the manufacturing conditions of the veneer strand flanged I-beam invented in the previous study was investigated using different combinations of strand dimensions, resin types between web and flange, different pressing times, and different wood–resin moisture contents under conventional hot pressing conditions. The main results revealed that the strand dimensions have no effect on the bending properties of the flange part and the dimensional stability of the I-beam. Increasing the resin application rate between strands was found to improve the dimensional stability of the I-beams. The use of isocyanate (MDI) resin between web and flange significantly improved the bond strength between web and flange, the modulus of rupture of the I-beam, and the modulus of rupture of the flange part. Dimensional stability was also improved. Shortening the pressing time from 20 to 12 min was found to be feasible. Using low wood-resin moisture content was found to interfere with the curing of the phenol–formaldehyde (PF) resin at the flange part resulting in poor quality beams. Of the three moisture content levels tested, 12% was found to be the optimal level for producing I-beams with balanced mechanical properties and dimensional stability.

Analysis of the effects of density profile on the bending properties of particleboard using finite element method (FEM)

The bending properties of particleboards with various density profiles were analyzed by calculating their modulus of elasticity (MOE) using two-dimensional finite element method (FEM). The calculation was based on the fundamental properties of homo-profile particleboards (board with flat density profile) produced from lauan (Shorea spp.) particles and an isocyanate resin. The results are summarized as follows: 1. The calculated MOE fit very well with the experimental values, with a deviation of below 5%. 2. Increment in peak density (PD) results in a proportional increase in MOE, while core density (CD) determines the optimum slope gradient between the peak and core regions. 3. The counteractive effect arising from increment in PD and simultaneous reduction in peak width resulted in merely 9% improvement in MOE, when PD was increased from 1.0 to 1.5 g/cm 3 . 4. Increment in peak distance (Pdi) results in a proportional reduction in MOE. When Pdi was doubled from 1 mm to 2 mm, MOE was reduced by about 11%. 5. In idealized density profile models, when peak and core densities remain unchanged, the maximum peak area does not necessarily result in the highest MOE. 6. Multiple regression analysis shows that the overall MOE of particleboard depends basically on the board mean density (MD), PD and Pdi.

Application of Isocyanate Resin Adhesives for Wood-based Panels

Application of Isocyanate Resin Adhesives for Wood-based Panels

One layer experimental particleboard from coconut chips - ( Cocos nucifera L.)

This article validates the technical feasibility of making one layer experimental particleboard from coconut chips bonded with EMDI isocyanate resin. The European Standards for particleboards used in interior fitments (EN 312; P2 and P3 boards) were satisfied at dosing rates of 4% EMDI. The P4 load bearing board used in dry conditions, however, required a higher dosage rate of 6% EMDI with 1% wax. When the data was evaluated using the ANSI A208.1‐1998 standards for particleboards, it was found that the modulus of rupture and internal bond were easily satisfied with an application of 6% EMDI, however, a higher dosing rate of 8% EMDI resin and 0.5% wax was needed mainly to satisfy the thickness swell criteria. Although these high resin application rates for particleboards made with coconut chips may not be economically practical for some uses, this valuable resource does show some promise for P2 and P3 boards. It is suggested that a combination of coconut chips with industrial wood chips may be explored in order to improve the thickness swelling properties of the particleboards. Einschichtige Laborplatten aus Cocosnus-Chips

Durability of isocyanate resin adhesives for wood III: degradation under constant dry heating

Durability of isocyanate resin adhesives for wood III: degradation under constant dry heating

Durability of isocyanate resin adhesives for wood IV: degradation under constant steam heating

The durability of isocyanate resins consisting of emulsion-type polymeric diphenylmethane diisocyanate (EMDI) was investigated under constant steam heating. Two kinds of resin, water only-added resin and polyol/water-added resin, were used in this study. The degradation of the resins under steam heating was observed using Fourier transform infrared spectroscopy (FT-IR), weight changes, and thermogravimetric analysis (TGA). FT-IR analysis showed that the degradation reaction of the resins scarcely proceeded for a few hours and then increased significantly. The weights of the resins decreased linearly during steam heating. The thermal stability of steam-treated resins was made clear by TGA. The bond strength reductions of the specimens bonded with the resins were also observed. The best fitting regression function for the behavior of bond strength reduction was determined statistically. The apparent activation energy of each resin was calculated from the regression function, for the half-life period. Considering the calculated values, the adhesion durability of using polyol-added resin was superior to that of using water only-added resin. It was clarified that the durability of the isocyanate resins under steam heating was markedly inferior to that under dry heating.

Isocyanate Resins for Particleboard: PMDI vs EMDI

The purpose of this paper was to determine which of the isocyanate resins, PMDI or EMDI, was better for use in particleboard manufacture. It was found that particleboards bonded with EMDI exhibited superior mechanical properties than those bonded with PMDI. This was particularly noticeable when the resins were applied at a rate of 2%. At this low dosage EMDI satisfied EN 312 criteria for boards in interior fitments while 4% was needed to meet the requirements for load bearing panels in humid conditions.