Mechanical characterization of industrial particleboard panels glued with cornstarch–mimosa tannin–urea formaldehyde resins

The aim of this work was to validate the utility and performance of optimal laboratory cornstarch–mimosa tannin-based resins in the industrial particleboard production. In this way, the cornstarch and mimosa tannin was introduced in the classic adhesive formulation in order to supply a part of urea-formaldehyde (UF). Our results show that industrial particleboard panels (8.2?m?×?1.85?m?×?19?mm) bonded with optimal cornstarch–mimosa tannin–UF (10:4:86; mass ratio) resins exhibited comparable mechanical properties to those of boards bonded with commercial UF resins and largely satisfied the exigencies of European norms EN 312. The formaldehyde emission levels obtained from panels bonded with cornstarch–mimosa tannin–UF were lower to those obtained from panels bonded with control UF. Finally, the addition of cornstarch and mimosa tannin improves markedly the water resistance of UF resins.     

Soy-based,tannin-modified plywood adhesives

In this research, two different types of commercial tannins, namely a hydrolysable tannin (chestnut) and a condensed flavonoid tannin (mimosa), were used to prepare two types of soy-based (soy flour (SF) and soy protein isolate) adhesives for making plywood. Thermogravimetric properties (TGA) and its derivative as function of temperature (DTG) of different soy-based adhesive were measured in the range 40°C–300°C. Thermomechanical analysis (TMA) from 25°C to 250°C was done for the different resin formulations. Duplicate three-ply laboratory plywood panels were prepared by adding 300 g/m² of the adhesives’ total resin solid content composed of SF or isolated soy protein (ISP), urea, chestnut, and mimosa tannin extracts with hexamine as hardener. Based on the results obtained, tannins can improve SF adhesion properties. The TMA showed that chestnut tannin extract appeared to react well with SF, while mimosa tannin extract appeared to react well with ISP. Matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry also showed that among other reactions, the soy protein amino acids reacted with the tannins. Furthermore, delamination and shear strength test results showed the good water resistance of plywood bonded with soy-based tannin modified adhesive.     

Fabrication and mechanical analysis of mimosa tannin and commercial flax fibers biocomposites

Composites were prepared by impregnating commercial nonwoven and unidirectional flax fibers mats, with a mimosa tannin/hexamine resin without addition of NaOH as it was described in previous papers and with improved results. The influence of various parameters was observed: the curing cycle including temperature, time, pressure, the moisture content, and the number of fiber mats the composites were made of. A new two-step method was investigated: full drying of the pre-impregnated mats for storage first and then rehydratation just before pressing. The composites obtained gave good modulus of elasticity and tensile strength in traction as well as a good resistance to water swelling for composites prepared with 50% matrix resin/50% natural fibers. Best results appear to be obtained using a slow curing at low temperature (130?°C for 35?min) with moisture content of 20% on dry material.     

Low Formaldehyde Emitting Biobased Wood Adhesives Manufactured from Mixtures of Tannin and Glyoxylated Lignin

Abstract

Kraft (LN-T-CO₂-2) and wheat straw (CIMV) glyoxalated lignin mixed with mimosa tannin and hexamine as a hardener were used as wood adhesive resins in particleboard fabrication. The adhesive systems proportion used were 40/60 and 50/50 w/w for lignin and tannin, respectively. The gel time test was determined by knowing the polymerization time between the different mixes under the controlled conditions. The results showed a slower polymerization with the kraft lignin/mimosa tannin blending than with the wheat straw lignin/mimosa tannin one. Thermomechanical analyses (TMA) tests were carried out as an indication of the final strength of the adhesive systems revealed by the elasticity modulus (MOE). The MOE results have demonstrated the best mechanical resistance values in 40/60 lignin/mimosa tannin proportion with respectively 3.422 and 3.347 (MPa), for CIMV and LN-T-CO₂-2, and 2.122 (MPa) for 50/50 proportion. Particleboards were prepared and the internal bond (IB) tests were carried out according to the European Standard EN 312. The IB tests confirmed the TMA results. The higher mechanical results of the IB were .43 and 0.53 (MPa), for CIMV and LN-T-CO₂-2 lignin in a 40/60 lignin/mimosa tannin proportion. They were classified as interior panel P2 in according with the standard request EN-312. Free-formaldehyde was determined through the flask method EN 717-3. Particleboards prepared with these natural adhesive resins registered emissions at least 87 and 75% lower than the commercial UF and MUF dhesive resins. The panels were classified as E0.     

Influence of processing conditions and material compositions on the performance of formaldehyde‐free wood‐based composites

This study examined the differences between formaldehyde‐free wood composite panels made with maleated polyethylene (MAPE) and maleated polypropylene (MAPP) binding agents. Specifically, the study investigated the contrasts of (a) base resin type, PE vs. PP, (b) molecular weight/maleic anhydride content in MAPP binding agents, and (c) the manufacturing methods (reactive extrusion vs. hot press) on the physicomechanical properties of the composites. FTIR and XPS analyses of unmodified and modified wood particles after reactive extrusion with maleated polyolefins provided evidence of chemical bonding between the hydroxyl groups of wood particles and maleated polyolefins. Although extruding the particles before panel pressing gave better internal bond (IB) strength, superior bending properties were obtained through compression molding alone. MAPP‐based panels outperformed MAPE‐based panels in stiffness. Conversely, MAPE increased the IB strength of the panels compared with MAPP. Polymer base resin had no effect on modulus of rupture or screw holding capacity. Differences between the two maleated polypropylene compounds were not significant for any of the mechanical properties tested. Formaldehyde‐free wood composites manufactured in this study often outperformed standard requirements for conventional particleboard, regardless of material composition or manufacturing method used. POLYM. COMPOS., 27:599–607, 2006. © 2006 Society of Plastics Engineers     

Phthalonitrile-glass fabric composites

Phthalonitrile polymers, under development at the Naval Research Laboratory, offer promise as high temperature, high performance composite matrix materials. A fully cured resin shows outstanding thermal stability with no evidence of a glass transition temperature or T_g up to 450°C, good mechanical properties, and is easily processed into void-free components. Phthalonitrile/glass fabric composite panels have been successfully fabricated by conventional consolidation of prepregged glass and by a more recently developed simplified process, resin infusion molding. Both processes can be used to produce panels with comparable mechanical properties. More important, flammability performance of these composites, evaluated in terms of specific optical density, combustion gases, heat release, and ignitability, excels over other state-of-the-art polymer/glass composites. This finding is significant given that overcoming flammability obstacles has been the main limiting factor for use of composites in marine applications.     

Reduction of formaldehyde emission from plywood

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with tannin-based resins were lower than those obtained from panels bonded with control PF and MF. Although there are no actual reaction at all between PF, MF, and tannin, addition of tannin significantly improves the water resistance of PF and MF resins. This is a novel finding that manifests the possibility of replacing a convention PF and MF resins by tannin. Modified adhesive is one of the goals in the plywood production without changing any of their production conditions with improvement to their overall properties.     

Shear Refinement of Formaldehyde-Free Corn Starch and Mimosa Tannin (Acacia mearnsii) Wood Adhesives

The aim of this work was to reduce the viscosity of formaldehyde-free corn starch–mimosa tannin wood adhesives, without adversely affecting the mechanical properties of the product. The reduction of viscosity was achieved using shear refinement. The study focused on the physical phenomena before cross-linking of the wood adhesive. The physical (rheological characterization) and mechanical (bond strength) properties of formaldehyde-free corn starch and mimosa tannin wood adhesives were measured. The results showed that the shear refinement (290 rpm and 5 min, optimal conditions) reduced the viscosity of the corn starch–mimosa tannin wood adhesives (from 100 000 to 458 Pa s) with the advantage of being stable over time. Mechanical tests showed that the shear refinement did not influence the mechanical properties of corn starch–mimosa tannin wood adhesives.     

A novel fiber–veneer-laminated composite based on tannin resin

Natural nonwoven fiber was impregnated with a tannin resin and laminated with wood veneer for preparation of laminated composites. The tannin resin used showed a good compatibility with the natural fiber, and was easy to assemble with the wood veneers. The tannin resin penetration into the wood veneer was observed by light microscopy. The laminated composite shows very good mechanical properties and water resistance. Shear force–displacement testing demonstrates that the laminated composite had a ductile behavior under wet testing conditions. The laminated composite was prepared using 100% natural biorenewable raw materials and had good properties compared to conventional plywood bonded with synthetic resin.     

Thermal and mechanical properties of woodflour/tannin adhesive composites

Composite materials formulated with a natural polyphenolic matrix (commercial tannin adhesive made from quebracho tannin extract), pine woodflour as reinforcing material, and hexamethylenetetramine as hardener were prepared and tested. Scanning electron microscopy of fractured samples was used to analyze the efficiency of the wetting and adhesion of the filler to the surrounding matrix. Thermogravimetric analysis was used in the thermal characterization of the woodflour and the tannin extract. Flexural, compression, and dynamic‐mechanical tests were performed on composites to study the relationship of the filler content and particle size with the composite final properties. Moreover, the influence of the moisture content on the physical and mechanical properties of the different composites was analyzed. Results indicated that the mechanical properties were severely affected by the absorbed moisture. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3074–3082, 2004     

Bond Formation By Wood Surface Reactions Part Iv Analysis of Furfuryl Alcohol,Tannin and Maleic Acid Bridging Agents

Abstract

Solid wood panels (Acer saccharum Marsh.) were bonded with various bridging materials following nitric acid activation. These chemical bridging materials included tannin, furfuryl alcohol and mixtures of the two with and without maleic acid. High shear strengths were achieved with a tannin-furfuryl alcohol-maleic acid mixture (T-F-M) with or without the nitric acid activation.

The curing reactions of the bridging material were examined with differential scanning calorimetry (DSC). Furfuryl alcohol was found to be the most reactive component of the T-F-M. Results from both the bonding work and the DSC analysis showed little effect of open assembly time or pot-life. The furfuryl alcohol appeared to be nitrated by the nitric acid catalyst. The nitrated material apparently degraded at high temperature (180 C) in a violent reaction detected by DSC. While these reactions were not observed with the panels the possibility of violent reactions during pressing must be considered.     

风电叶片用真空灌注型环氧树脂及其复合材料性能研究

本文针对两种自制的风电叶片用真空灌注型环氧树脂体系EP-1和EP-2,研究了树脂的工艺性和力学性能,并选取单轴向和三轴向玻璃纤维织物,采用真空灌注工艺制备了复合材料层板,考察了复合材料在室温和高低温下的力学性能。结果表明,EP-2体系浸润性、流动性和韧性更好,但强度、模量和耐热温度略低;常温及-45℃下两种树脂基复合材料的力学性能相近,纤维/树脂界面粘结较强;50℃环境下,复合材料的压缩强度降低,受玻璃化转变温度偏低的影响,EP-2复合材料压缩性能降低更为明显;两种环氧树脂的工艺性和力学性能优异,与纤维匹配性好,满足风电叶片对树脂的性能要求。     

Studies on synthesis,characterization, and metal adsorption of mimosa and valonia tannin resins

A few thermosetting wood adhesive tannin resin system from formaldehyde reaction with both condensed and hydrolysable tannin has been developed. Polymerization of formaldehyde with mimosa tannin and valonia tannin was carried out at optimal conditions obtained from literature to establish the adhesive resin formulation. Formed reaction products were characterized by FTIR spectroscopy. The possible adsorption mechanisms for the adsorption of various metal ions onto tannin‐formaldehyde resins were proposed. Also, thermal analysis were studied and discussed by differential scanning calorimetry and thermogravimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 786–797, 2006     

Preparation of SiC/C composite sheet from polycarbosilane/carbon-based resin mixture

SiC/C composites were prepared from a mixture of polycarbosilane and phenolic resin with weight ratio of 2/1 and 1/1 using PVB as a binder. The two types of green bodies which were formed by mould pressing method were treated in the temperature range from 1,000‡C to 1,500‡C under nitrogen. X-ray diffraction patterns, density, flexural strength and fracture surfaces of the composite were examined. The flexural strength of the composites at room temperature increased with heattreatment temperature and showed a maximum value of 175 MPa at 1,300‡C. When the composite was heat treated at 1,400‡C, the flexural strength decreased rapidly due to the crystallization of SiC. The SiC/C composites showed good oxidation resistance up to 830‡C. The effective mixing ratio of PCS/phenolic resin to obtain improved mechanical property was 2/1.     

高强高模聚乙烯纤维植物纤维纸基复合材料制备及性能

以高强高模聚乙烯（UHMWPE）短纤维和针叶木浆为原料，通过湿法成型技术结合树脂浸渍热压方法制备了UHMWPE纤维纸基复合材料，研究了原纸制备工艺和浸渍热压工艺对UHMWPE纤维纸基复合材料性能的影响。结果表明，当UHMWPE纤维与针叶木浆质量比为7∶3、针叶木浆打浆度为58°SR、酚醛树脂水溶液质量分数为10%、上胶量为44%、热压工艺为15 min、10 MPa、130℃时，制得的UHMWPE纤维纸基复合材料性能较好。当原纸经过浸渍热压后，所制备的UHMWPE纤维纸基复合材料抗张指数为59.11 N·m/g，与原纸相比抗张指数提高了6.9倍，表面变得更光滑，同时具有较低的介电常数（约1.97）、介质损耗因数（0.45×10–2）和较好的热稳定性。     

真空辅助树脂灌注配套基体树脂的制备及性能

针对真空辅助成型技术(VARI)对基体树脂的特殊要求,结合航空材料对性能的高要求,研制了BA9912中温固化环氧树脂体系。采用VARI工艺制备了G0827/BA9912复合材料,测试了BA9912树脂浇注料及其复合材料的力学性能和耐热性能,并与国内外同类树脂进行了适当的比较分析。分析测试结果表明,BA9912树脂具有良好的力学性能、耐热性能和工艺性能,能够满足VARI成型工艺要求,适合在航空航天领域中应用。     

沥青树脂复合材料的摩擦磨损性能研究

利用树脂基复合材料制造的各种减摩耐磨零件,在机械工程中作为金属材料的替代产品或换代产品,获得了越来越多的应用。文中对通过在沥青树脂中添加聚四氟乙烯（PTFE）、二硫化钨（WS2）、石墨（GP）等固体润滑剂的复合物摩擦磨损性能进行了讨论。分别添加了一定比例的PTFE、WS2、GP的沥青树脂复合材料的磨损率是0．02～0．25×10^-7cm^3N^-1m^-1。其中加入40wt％GP的沥青树脂复合物的磨损率最低,为0．02×10^-7cm^3N^-1m^-1。这些复合材料的摩擦系数肛比纯沥青树脂下降了0．014-0．180。     

Mechanical properties of wood plastic composite panels made from waste fiberboard and particleboard

The possibility of producing wood‐plastic panels using a melt blend/hot press method was studied in this research. The studied panels were compared with conventional medium density fiberboard (MDF) and particleboard (PB) panels. Wood‐plastic panels were made from high density polyethylene (as resin) and MDF waste and PB waste (as natural fiber) at 60, 70, and 80% by weight fiber loadings. Nominal density and dimensions of the panels were 1 g/cm³ and 35 × 35 × 1 cm³, respectively. Mechanical properties of the panels including flexural modulus, flexural strength, screw and nail withdrawal resistances, and impact strength were studied. Results indicated that the mechanical properties of the composites were strongly affected by the proportion of the wood flour and polymer. Maximum values of flexural modulus of wood plastic panels were reached at 70% fiber content. Flexural strength, screw and nail withdrawal resistance, and impact strength of wood plastic composites declined with the increase in fiber content from 60 to 80%. This was attributed to the lack of compatibility between the phases. The produced panels outperformed conventional PB panels regarding their mechanical properties, which were acceptable when compared with MDF panels as well. The best feature in the produced panels was their screw withdrawal resistance, which is extremely important for screw joints in cabinet making. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Industrial scale evaluation of cationic tannin as a binder for hardboard

Hardboards (HBs) (wet-process high-density fibreboards) were made in an industrial trial using a binder system consisting of cationic mimosa tannin and laccase or just cationic tannin without any thermosetting adhesive. The boards displayed superior mechanical strength compared to reference boards made with phenol–formaldehyde, easily exceeding the European standards for general-purpose HBs. The thickness swell of most of the boards was slightly greater than the standards would allow, so some optimisation is required in this area. The improved board properties appear to be mainly associated with ionic interactions involving quaternary amino groups in cationic tannin and negatively charged wood fibres rather than to cross-linking of fibres via laccase-assisted formation and coupling of radicals in tannin and fibre lignin.     

Acid- and alkali-catalyzed tannin-based rigid foams

Acid- and alkali-catalyzed polyflavonoid tannin-based rigid foams were prepared. These foams have comparable physical and mechanical properties to the synthetic phenolic rigid foam used as a comparative standard. The fluid polymer phase was based on a mimosa tannin-formaldehyde resin with a minor addition of a fortifier resin. Expansion of the fluid phase was brought about by a physical blowing agent, whereas dimensional stabilization was achieved through cross-linking at the desired density. In the case of the acid-catalyzed foam, a heat-generating agent in the form of furfuryl alcohol was employed. The polymer composition of tannin–formaldehyde/urea–formaldehyde systems as a function of pH was predicted from the respective gel times and rate constants, i.e., above pH 7, the copolymer proportion will tend to 100% and, that at pH 3.4, the polymer blend proportion will tend to a maximum. © 1994 John Wiley & Sons, Inc.