Evaluation of mechanical and physical properties of industrial particleboard bonded with a corn flour–urea formaldehyde adhesive

The aim of this study was to determine the effect of corn flour content of urea formaldehyde (UF) resin on the panel properties of particleboard. Corn flour was added to UF resin to decrease the free formaldehyde content of particleboard panels. Some physical (thickness swelling and rheological characterization), mechanical (modulus of elasticity, modulus of rupture, internal bond strength and withdrawal of screws) properties and formaldehyde emission of particleboards were evaluated. The results showed that the introduction of small proportions of corn flour (7%, by weight) in UF resins contributes to the improvement of mechanical and physical properties of the boards and reduced their formaldehyde emissions. Hazardous petrochemical UF could be partially substituted in industrial applications by addition of corn flour. To our knowledge, this is the first study on this kind of wood adhesives.     

Studies on structure and properties of CNSL novolac resins prepared with succinic acid catalyst

Cashew nut shell liquid (CNSL) was used to prepare a glass fabric laminate. Two fast curing model resins were prepared using cardanol and formaldehyde in the presence of succinic acid catalyst. The resins possess ortho-ortho and ortho-para linkages. The curing kinetics of the resins showed that the resin prepared with mole ratio 0·8 possesses good curing characteristics. The IR spectra of cured resin showed responses for high ortho linkage. A CNSL high ortho novolac resin was prepared with mole ratio 0·8. The glass fabric laminates prepared with CNSL resin showed good mechanical properties and dimensional stability. It is suggested that the candidate laminate can be used as secondary load bearing structures or panels.     

Cure characteristics of alkali catalysed cashew nut shell liquid-formaldehyde resin

Cashew nut shell liquid (CNSL) is a naturally occurring chemical monomer consisting four alkyl substituted phenols. Its phenolic nature makes it suitable for polymerisation into resins by formaldehyde using sodium hydroxide (NaOH) as a catalyst and hexamethylenetetramine (HMTA) employed as a hardener. There is intense interest in understanding the cure characteristics and properties of CNSL-based resins. In this work the DSC technique has been applied to study the change in the glass transition temperature of the oven-cured resin with and without HMTA in order to monitor the extent of cure. The glass transition temperature was found to rise when the alkaline catalysed resin was subjected to higher curing temperatures regardless of the concentration of formaldehyde used. The mode of cure of the NaOH-catalysed CNSL-formaldehyde resin has been found to be more regular with HMTA hardener. FT-IR spectroscopy has been used to study the neat CNSL and polymerised CNSL-formaldehyde resin with and without HMTA. The use of the DSC and FT-IR techniques to elucidate the extent of cure of CNSL resins is a valuable step towards the production of commercially successful CNSL-natural fibre composites.     

Effect of γ-irradiation on the hydrolytic stability and thermo-oxidative behavior of bio/inorganic modified urea–formaldehyde resins

In order to minimize emission of formaldehyde from urea–formaldehyde resins (UF) and to improve their thermo-oxidative behavior, the effect of low γ-irradiation on hydrolytic and thermo-oxidative stability of nano-silica modified UF resin, modified UF resin with wood flour (Pinus silvestris L.) as natural filler and modified UF resin with mixture of SiO₂/WF fillers were investigated. The hydrolytic stability of modified UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF resins after acid hydrolysis. The studied modified UF resins have been irradiated (50 kGy) and effect of γ-irradiation was evaluated on the basis of percentage of liberated formaldehyde before and after irradiation. The minimum percentage (1.23%) of liberated formaldehyde and mass loss of a 25.35% were obtained in wood flour modified UF resin after γ-irradiation which indicate significant improvement in the hydrolytic stability compared to other modified UF resins. The effect of γ-irradiation was evaluated also on the basis of thermo-oxidative behavior of the same modified UF resins before and after irradiation. The thermo-oxidative behavior was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermo-gravimetry (DTG) and differential thermal analysis (DTA) supported by data from IR spectroscopy. After γ-irradiation, the shift of DTA peaks a higher temperature indicates that thermo-oxidative stability of modified UF/SiO₂/WF is increase.     

Correlation between sound absorption coefficients with physical and mechanical properties of insulation boards made from sugar cane bagasse

Physical and mechanical properties, as well as sound absorption coefficients, of insulating boards made of bagasse were studied here. Urea–formaldehyde (UF) and melamine–urea–formaldehyde (MUF) were used to produce homogeneous as well as three-layered insulating boards with three densities of 0.3, 0.4, and 0.5 g/cm³. The obtained results indicated that resin-type had no significant effect on physical or mechanical properties; however it affected sound absorption coefficients. Physical and mechanical properties were significantly influenced by the density, while sound absorption coefficients were affected by the board-type. High correlation was found between the physical and mechanical properties; however, considering the low correlation between the physical and mechanical properties with the SAC values, it may be concluded that SAC could not be an authentic criterion to predict physical and mechanical properties in particleboards made of sugar cane bagasse.     

The efficiency of tannin as a formaldehyde scavenger chemical in medium density fiberboard

The aim of this study was to determine the effect of tannin content of urea formaldehyde (UF) resin on the panel properties of medium density fiberboard (MDF). Tannin extracted from the bark of white oak (Quercus alba) was added to UF resin at different ratios (based on the resin) to decrease the free formaldehyde content of MDF panels in this study. It was determined that free formaldehyde values of MDF panels decreased when the ratio of tannin content in UF resin increased. However, the modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB) of these panels were a little lower, and the thickness swelling (TS) (24 h) and water absorption (WA) (24 h) values were a little higher compared to the control MDF panels.     

Properties of sisal-CNSL composites

Cashew nut shell liquid (CNSL) is a natural monomer blend that has been condensation poylmerized with formaldehyde in the presence of an alkaline catalyst to produce a thermosetting resin. Plain woven mats of mercerized sisal fibre have been impregnated with CNSL-formaldehyde resin to produce plain and corrugated laminated composites that have a mean tensile strength of 24.5 MPa and Young's modulus of 8.8 GPa. Bending tests have demonstrated that the corrugated composites have adequate strength for roofing applications. Dynamic mechanical thermal analysis has been used to assess the effect of simulated sunlight on composites as a function of time. After long irradiation times it has been deduced that the resin component of the composite undergoes further cross-linking whilst the reinforcing cellulosic sisal fibres suffer some degradation.     

Using almond (Prunus amygdalus L.) shell as a bio-waste resource in wood based composite

In this research, the suitability of almond shell as a bio-waste resource in wood based composite manufacturing was investigated. Particleboards containing different almond shell particle rations were made using urea–formaldehyde (UF) resin. Some chemical properties of almond shell (holocellulose, α cellulose, lignin and ash contents, alcohol–benzene solubility, 1% NaOH solubility, hot and cold water solubility), mechanical (modulus of rupture, modulus of elasticity and internal bond strength) and physical properties (thickness swelling and water absorption) of the particleboards were determined. The addition of almond shell particles greatly improved the water resistance of the panels. However, flexural properties and internal bond strength decreased with increasing almond shell particle content. The amount of almond shell particles at most should be 30% in the mixture to meet the standard required for mechanical properties. Conclusively, almond shell, an annual agricultural residue, could be utilized with mixture of wood particles in the particleboard manufacturing.     

PPENK增韧改性BMI树脂体系的制备与性能

采用溶液法制备了杂萘联苯聚芳醚腈酮(PPENK)/双马来酰亚胺树脂(BMI)共混体系。通过差示扫描量热法(DSC)对共混体系固化反应动力学进行了研究,固化活化能为85.8 kJ/m2。采用冲击和拉伸实验考察了PPENK含量对共混体系力学性能的影响,共混体系的冲击强度为1.83 kJ/m2～2.95 kJ/m2,拉伸强度为68 MPa～84 MPa,拉伸模量为1.14 GPa～1.53 GPa。通过对固化物断面的扫描电镜(SEM)分析了增韧机理,改性后的BMI树脂在断裂时发生了塑性变形。通过热重分析法(TGA)研究了体系的耐热性,共混体系在氮气气氛中5%热失重温度为420℃～426℃。     

MBS树脂相相对分子量变化对PVC/MBS力学性能的影响

通过调控分子量合成了系列树脂相相对分子量变化的MBS树脂.将其与PVC树脂进行熔融共混,并测试PVC/MBS合金的力学性能.测试结果表明,分子量转移剂TDDM用量越多,MBS树脂相的相对分子量越低,PVC/MBS合金熔体流动速率越高、加工流动性越好、冲击强度越高,但对拉伸强度影响不大.这对开发系列MBS树脂具有重要指导意义。     

环氧树脂低聚物原位增容PA66/TLCP共混物

用环氧树脂低聚物作界面增容剂,熔融挤出法制备了PA66/TLCP共混物。通过拉伸、弯曲等力学性能测试并结合热失重(TG)分析,结果表明:环氧树脂低聚物增容后的共混物力学性能、热稳定性均有显著提高。共混物断面SEM扫描结果表明,由于环氧树脂低聚物界面增容作用,分散相TLCP在基体PA66中的分散性提高并且相畴尺寸减小。加工流变学测试和红外光谱显示,环氧树脂低聚物与基体树脂PA66和分散相TLCP分子在熔融加工过程中原位发生化学反应,环氧树脂低聚物在共混物界面起到桥的作用。     

The potential for using walnut (Juglans regia L.) shell as a raw material for wood-based particleboard manufacturing

In this study, the suitability of walnut shell as a renewable agricultural residue for panel manufacturing was investigated. Particleboards containing different walnut shell particle ratios (0%, 10%, 20%, 30%, 40% and 100%) were made using urea–formaldehyde (UF) resin. Some chemical properties of walnut shell (holocellulose, α cellulose, lignin and ash contents, alcohol–benzene solubility, 1% NaOH solubility, hot and cold water solubility), mechanical (modulus of rupture, modulus of elasticity and internal bond strength) and physical properties (thickness swelling and water absorption) of the particleboard were determined. The addition of walnut shell particles greatly improved the water resistance of the panels. However, flexural properties and internal bond strength decreased with increasing walnut shell particle content. The results indicated that panels can be manufactured utilizing walnut shell particles up to 20% without falling below the minimum EN Standard requirements of mechanical properties for general purpose use. Conclusively, walnut shell, an annual residue, could be utilized with mixture of wood particles in the manufacture of particleboard used for outdoor environments due to lower thickness swelling and water absorption.     

The potential for using walnut (Juglans regia L.) shell as a raw material for wood-based particleboard manufacturing

In this study, the suitability of walnut shell as a renewable agricultural residue for panel manufacturing was investigated. Particleboards containing different walnut shell particle ratios (0%, 10%, 20%, 30%, 40% and 100%) were made using urea–formaldehyde (UF) resin. Some chemical properties of walnut shell (holocellulose, α cellulose, lignin and ash contents, alcohol–benzene solubility, 1% NaOH solubility, hot and cold water solubility), mechanical (modulus of rupture, modulus of elasticity and internal bond strength) and physical properties (thickness swelling and water absorption) of the particleboard were determined. The addition of walnut shell particles greatly improved the water resistance of the panels. However, flexural properties and internal bond strength decreased with increasing walnut shell particle content. The results indicated that panels can be manufactured utilizing walnut shell particles up to 20% without falling below the minimum EN Standard requirements of mechanical properties for general purpose use. Conclusively, walnut shell, an annual residue, could be utilized with mixture of wood particles in the manufacture of particleboard used for outdoor environments due to lower thickness swelling and water absorption.     

Poly(ether ether ketone) with pendent methyl groups as a toughening agent for amine cured DGEBA epoxy resin

A diglycidyl ether of bisphenol-A (DGEBA) epoxy resin was modified with poly(ether ether ketone) with pendent methyl groups (PEEKM). PEEKM was synthesised from methyl hydroquinone and 4,4′-difluorobenzophenone and characterised. Blends of epoxy resin and PEEKM were prepared by melt blending. The blends were transparent in the uncured state and gave single composition dependent T _g. The T _g-composition behaviour of the uncured blends has been studied using Gordon–Taylor, Kelley–Bueche and Fox equations. The scanning electron micrographs of extracted fracture surfaces revealed that reaction induced phase separation occurred in the blends. Cocontinuous morphology was obtained in blends containing 15 phr PEEKM. Two glass transition peaks corresponding to epoxy rich and thermoplastic rich phases were observed in the dynamic mechanical spectrum of the blends. The crosslink density of the blends calculated from dynamic mechanical analysis was less than that of unmodified epoxy resin. The tensile strength, flexural strength and modulus were comparable to that of the unmodified epoxy resin. It was found from fracture toughness measurements that PEEKM is an effective toughener for DDS cured epoxy resin. Fifteen phr PEEKM having cocontinuous morphology exhibited maximum increase in fracture toughness. The increase in fracture toughness was due to crack path deflection, crack pinning, crack bridging by dispersed PEEKM and local plastic deformation of the matrix. The exceptional increase in fracture toughness of 15 phr blend was attributed to the cocontinuous morphology of the blend. Finally it was observed that the thermal stability of epoxy resin was not affected by the addition of PEEKM.     

Studies on the blends of modified epoxy resin and carboxyl-terminated polybutadiene (CTPB)—II: thermal and mechanical characteristics

Blend samples were prepared by physical mixing of resole–epoxy blend with carboxyl-terminated polybutadiene (CTPB) liquid rubber ranging between 0 and 25 wt% in the interval of 5 wt%. Resoles were synthesized with phenol and various alkyl phenols. The blends were cured with 40 wt% polyamide. The structural changes during the curing were investigated by infra-red spectroscopic analysis. The presence of CTPB in resole-epoxy blends did not affected the values of cure times and ΔH whereas the gel time decreased up to 15 wt% addition of CTPB in the blends. The blend systems containing p-cresolic resole, epoxy and CTPB showed minimum gel time amongst all other blend samples. A clear-cut two-step mass loss in thermogravimetric (TG) trace of unmodified and CTPB-modified systems was observed. The mechanical properties of the blend samples were found to be affected by the CTPB addition. The plane strain fracture toughness (K _IC) values of CTPB-modified matrix resins were greater that that for the unmodified resole/epoxy blends. This was further verified by scanning electron microscopic (SEM) analysis.     

缩聚物/加聚物复合胶乳的制备科学Ⅱ.核壳结构聚氨酯-丙烯酸酯复合乳液的合成与表征

用合成的含羧基端羟基聚氨酯树脂，通过强外力乳化可形成稳定的水性聚氨酯乳液，与苯乙烯和丙烯酸丁酯等单体共聚，合成具有核壳结构的聚氨酯－丙烯酸酯接枝乳液，通过接枝乳液和共混乳液的性能差别对比，及DSC，FT－IR，粒径分析及力学性能测试分析表明，在聚氨酯－丙烯酸酯接枝乳液中，聚氨酯与丙烯酸酯发生部分交联形成稳定的核－壳结构，文中还对聚氨酯－丙烯酸酯接枝乳液的交联机理进行了研究。     

苯并噁嗪共混树脂及其玻璃纤维布增强复合材料的制备与性能

采用氨基保护和还原方法合成了对氨基苯炔丙基醚(APPE), 与苯酚和多聚甲醛通过Mannich缩合制备了含炔丙基的苯并噁嗪(P-APPE)。采用溶液共混的方法, 将P-APPE与苯酚/苯胺型苯并噁嗪(PAF)和含硅芳炔树脂(PSA)共混得到了改性苯并噁嗪树脂。用差示扫描量热法、动态热力学分析、热失重分析和宽频介电仪研究了该树脂体系的热性能和介电性能。研究结果表明: PSA加入到苯并噁嗪树脂中可提高共混树脂的热性能, 加入质量分数为14.3%的PSA可使共混树脂的 T _g从195℃提高至235℃, 其5%热失重温度从350℃提高至399℃; 共混树脂的介电损耗因子和介电常数随PSA加入量的增加而降低。玻璃纤维布增强的共混树脂复合材料的层间剪切强度和弯曲强度在加入质量分数为5.3%的PSA后下降超过50%。     

反应性聚碳酸酯/环氧树脂体系的反应活性与性能研究

采用DSC和TGA等方法研究了反应性聚碳酸酯/环氧树脂体系的固化特性，热性能和力学性能。结果表明，α-PC的加入，增加了体系的反应活性，固化体系的相容性也良好，形成一个均相网络结构。固化体系在350℃无任何分解，具有较好的耐热性，且体系的韧性也有所提高。     

氧化铝性能对环氧浇注的影响

氧化铝性能不仅影响环氧树脂酸酐体系的粘度、填料添加量,而且杂质还影响浇注件的表观及电气绝缘性能,以及对氧化铝环氧树脂中的分散性也有很大的影响。为了改善氧化铝的物化性能以对改善环氧浇注工艺和提高浇注制件质量,本文中从粒度及粒度分布、晶体结构、微观形貌、杂质含量等方面,对比分析了电工用氧化铝填料的各项物化指标对环氧树脂浇注性能及浇注件机电性能的影响,得出合适的粒度和粒度分布、提高α相转化率、改善微观形貌、提高纯度等是提高环氧浇注用填料氧化铝性能的途径。     

Mechanical and thermal properties of compatibilized composites of polyethylene and esterified lignin

Lignin have been esterified using phthalic anhydride and then blended with (up to 40 wt.%) low density polyethylene (LDPE). Maleic anhydride grafted LDPE has been added as compatibilizer. The mechanical and thermal properties of the blends were measured according to ASTM standards and compared with those of neat LDPE. The results reveal that addition of compatibilizer improved the mechanical properties significantly approaching values close to those of neat LDPE. The scanning electron micrographs of the blend specimens also support the above observations. Thermogravimetric analysis showed greater thermal stability for the compatibilized blends. The char content has been found to increase with increasing filler (lignin phthalate) content. DSC analysis revealed that the crystallinity values of the blends slightly increase by the addition of filler (lignin phthalate).