Potential for utilizing waste corrugated paper containers into wood composites using UF and PMDI resin systems

The objective of this study was to investigate the possibility of using waste paper recovered from old corrugated containers (OCC) as substitute for wood particles in the production of particleboards. Three proportions of wood chips: waste paper flakes (100:0, 70:30, 50:50) were used in the production of one-layer and the core of three-layer experimental particleboards. Various adhesive systems were applied as binders: a UF resin (E1 grade), a PMDI resin and three UF:PMDI combinations: (6:2, 5:3 and 4:4). The evaluation of the board’s mechanical and hygroscopic properties showed the following results: Replacing woods chips with waste OCC paper adversely affected the board’s properties. The participation of waste paper in the core layer resulted in decreased differentiation between surface and core density of the boards. Partial substitution of UF resin by PMDI in amounts of 2–4?% significantly improved the properties of boards containing 30 and 50?% waste paper. An increase in board density resulted in a corresponding improvement in mechanical properties. In terms of mechanical properties, three-layer UF boards containing 30?% and PMDI bonded boards containing 30 and 50?% waste paper in the core layer complied with the requirements of European Standard EN312 for board types P1, P2 and P4 for use in interior applications.     

Migration of melamine and formaldehyde from tableware made of melamine resin

Migration of melamine and formaldehyde into food-simulating solvents from cups made of melamine resin was studied under various conditions. Little migration of melamine was observed in any unused cups kept at 60 degrees C for 30 min, room temperature (26 degrees C) for 1 h or cooled at -20 degrees C for several days. Migration of both compounds was strongly affected by heating and acidity. The highest migration of melamine into 4% acetic acid used as a food-simulating solvent was 42.9 +/- 7.2 ppm when the migration test was repeated seven times at 95 degrees C for 30 min. In this time, the migration of formaldehyde was 14.2 +/- 0.6 ppm into the solvent. The molecular ratio of the migration amount of formaldehyde to melamine decreased according to the formula Y = 9.15X-0.813 over seven repetitions of the test, and was maintained at about 1.6 between the 10th and 20th repetitions. The inner surface of the cups became tarnished during the repetition of the test and their roughness increased from 1 micron before the test to 2.5-5 microns after 20 repetitions of the test. Migration of melamine from the cups being used at a cafeteria was 0.4 +/- 0.5 ppm, but that of formaldehyde was undetectable when the cups were kept at 60 degrees C for 30 min with 4% acetic acid.     

Effects of wood fiber content and coupling agent content on tensile properties of wood fiber polyethylene composites

This study investigated the effects of coupling agent content, wood fiber content and wood fiber type on the mechanical properties of wood fiber-reinforced polymer composites (WPC). This study adopted a response surface strategy of a 20 run optimal design for these three factors. The WPC modulus of elasticity was mainly influenced by wood fiber type and wood fiber content, and tensile stress at break depended on wood fiber type, wood fiber content and coupling agent content, whereas strain at break was significantly affected by wood fiber content and coupling agent content, but not significantly influenced by wood fiber type.     

三聚氰胺树脂硬挺整理常见问题分析及对策

阐述了织物在硬挺整理中会遇到的常见问题:整理时催化剂和渗透剂的选择、织物上游离甲醛超标、三聚氰胺树脂的稳定性和抗冻性、布面硬度和厚度、树脂花、白痕、霉点、色裂等.通过选择配套助剂和有效控制工艺可减少和克服这些常见问题.     

Evaluation of mass-transfer characteristics in alginate-membrane liquid-core capsules prepared using polyethylene glycol

An alginate-membrane liquid-core capsule prepared using polyethylene glycol as a thickener was produced and the intracapsular mass-transfer characteristics of glucose and proteins were investigated. The apparent effective diffusivity of glucose into the capsule was 7.9x10(-10) m(2)/s, which is larger than that into alginate beads (6.5x10(-10) m(2)/s) and in water (6.7x10(-10) m(2)/s). Moreover, an encapsulation of strawberry cells did not decrease the mass transfer performance of glucose, in contrast to the case of immobilization in alginate beads or capsules prepared using xanthan gum. On the other hand, the apparent effective diffusivities of proteins from the capsule were smaller than those in alginate beads. In addition, the apparent effective diffusivities from the capsule decreased with the increasing concentration and molecular weight of polyethylene glycol used as a thickener during capsule preparation.     

脲醛树脂胶浸注毛白杨木材工艺初步研究

对毛白杨木材浸注脲醛树脂胶工艺中的主要影响因素及相关工艺参数进行了初步研究。实验结果表明：（1）影响杨木浸胶量的由主到次因素为：开孔个数—浸胶时间—浸胶浓度;（2）在试验参数范围内开孔个数对增重率影响显著;（3）在试验参数范围内较优的工艺参数为浸胶浓度30%;浸胶时间2h;打孔个数8。     

Release of formaldehyde and melamine from tableware made of melamine-formaldehyde resin

The relationship between the concentrations of formaldehyde and melamine released into 4% acetic acid from dishes and bowls made of melamine-formaldehyde resin was determined. The average concentrations in the migration solution after the sample had been treated at 60, 80, and 95 degrees C for 30 min with 4% acetic acid were 0.0 +/- 0.1, 0.5 +/- 0.4 and 3.0 +/- 2.2 ppm, respectively for formaldehyde and 0.04 +/- 0.07, 0.21 +/- 0.20 and 1.19 +/- 1.18 ppm, respectively for melamine. The correlation between the concentrations of formaldehyde and melamine released at 95 degrees C was y=0.4858x-0.2728 (r=0.8860), where y is melamine concentration (ppm), x is formaldehyde concentration (ppm) and r is the correlation coefficient. The molar concentration ratios of formaldehyde to melamine (F/M ratio) were 15.4 +/- 11.6 at 80 degrees C and 14.9 +/- 10.1 at 95 degrees C. Hence the release of both migrants was affected by temperature but the F/M ratio was not affected. The release of both compounds was was increased on repetition of the migration test at 95 degrees C but their concentrations remained constant after the tenth and seventeenth repetitions of the treatment. During this period, the F/M ratio decreased according to the equation 1n y=-1.4344 1n x+3.7814 (r=-0.9984) for a sample before the tenth repetition of the treatment and remained between 1.7 and 1.9 after the twelfth repetition, where y is the F/M ratio and x is the number of repetitions of the treatment.     

Artificial weathering of wood surfaces modified by melamine formaldehyde resins

Spruce and poplar samples were treated with different melamine formaldehyde resins. A long term artificial weathering experiment was performed in order to clarify the resistance to weathering regarding wood colour and surface hardness. The increase in hardness due to melamine treatment was well preserved after simulated long term weathering. The treated samples also showed advantages compared to untreated reference samples regarding discolouration and crack formation. Low molar mass and low degree of methylolation of the melamine resin used was found to be favourable for a successful treatment.     

Swelling of polyvinyl alcohol, melamine and urethane treated southern pine wood

Anti-swelling properties of southern pine wood treated with polyvinyl alcohol (PVA) or melamine or urethane were evaluated by measuring the tangential swelling and water uptake using AWPA standards methods. The water-repellency efficiency (WRE) of melamine and PVA treated wafers exhibited values 80% superior to untreated wafers. This study confirms that waterborne solution containing 3% of melamine or 3% of PVA can be used to reduce the swelling of southern pine.     

The influence of curing conditions on properties of melamine modified wood

The curing conditions influence the material properties of wood modified with methylated melamine formaldehyde resin. To identify the most influential parameters, the process conditions were varied separately. The degree of conversion (differential scanning calorimetry; DSC), work in bending, nitrogen fixation, formaldehyde emission, formaldehyde content and content of free formaldehyde were measured to verify the influence of the curing conditions on the material properties. The temperature and duration positively influenced the curing of melamine resin as the DSC results and the nitrogen fixation indicate. However, the relative humidity (RH) had the greatest influence on the material properties: the formaldehyde properties and the work in bending differed most between dry and high RH processes with the latter producing material being less brittle and having lower formaldehyde emissions. It can be derived that DSC measurements, formaldehyde emission and -content are valuable methods to characterize the influence of curing conditions on the material properties. The formaldehyde content in combination with the emission revealed a different formaldehyde release factor for dry and high RH processes. In the future, the curing process conditions can be designed depending on the desired material properties: dry, high temperature processes will lead to more complete curing, whereas hot steam processes can be used for material with low formaldehyde emissions.     

壳聚糖/聚乙二醇共混膜性能研究

制备了不同配比的壳聚糖/聚乙二醇共混膜,利用差示扫描量热仪和动态热机械分析仪对共混膜的热性能进行了测试,结果表明:随着聚乙二醇含量的增多,共混膜的玻璃化转变峰越宽,膜的韧性提高,玻璃化转变温度、结晶度和刚度降低.     

Dynamic mechanical properties of decorative papers impregnated with melamine formaldehyde resin

Papers impregnated with melamine formaldehyde based resins are widely used in decorative surface finishing of engineered wood based panels for indoor and outdoor applications. For cost-effective production of high-quality impregnated papers it is of great importance to understand the complex interplay between manufacturing conditions and technological property profile. In the present study, three raw papers from different suppliers were impregnated with melamine formaldehyde resin in an industrial scale experiment to study the influence of some important manufacturing variables on the processability of impregnated papers. As numerical factors the resin loading, the final moisture content and the amount of curing catalyst were systematically varied according to a statistical central composite design. The model papers were analyzed for their rheological and thermal properties using the dynamic mechanical method developed by Golombek. As target values flow time, cure time, curing rate and flexibility were used to calculate quantitative models for the processability of the impregnated papers using response surface methodology. It is shown that the relevant rheological and thermal paper parameters are significantly influenced by the supplier of the raw paper as well as the manufacturing variables.     

木塑复合材料力学性能影响因素研究

采用木材刨花与LDPE、HDPE.和PP等热塑性高分子聚合物,经热压复合工艺制成木塑复合板材,研究了塑料基质种类、刨花用量与偶联剂种类对木塑复合材料力学性能的影响。结果表明:相较于LDPE和PP,由HDPE制成的木塑复合材料力学性能更佳;所使用的三种偶联剂,以硅烷偶联剂的效果最好;随着刨花用量的增加,木塑复合材料的抗弯曲性能逐步提高,但内结合强度逐渐下降。     

Rheological properties of ABS/wood composites

In this work, the rheological properties of acrylonitrile–butadiene–styrene (ABS)/wood composites were investigated using a capillary rheometer. The present composites with different ratios of ABS and wood were prepared by means of an internal bath mixer. The viscosity of the composites that were pseudo plastics in deformation manner increased with increasing amount of wood particles. In addition, the flow activation energy of the composites increased with increasing amount of wood particles.     

Colour in short-term thermo-mechanically densified veneer of various wood species

Effect of short-term thermo-mechanical (STTM) densification temperature and pressure on the surface colour of veneer of four wood species—alder (Alnus glutinosa Gaertn.), beech (Fagus sylvatica L.), birch (Betula verrucosa Ehrh.), and pine (Pinus sylvestris L.) as well as possible correlations among all determined colour parameters (L*, a*, b*, h, C* and ?E) were investigated. Veneer sheets were densified at temperatures of 100, 150 or 200 °C and pressures of 4, 8 or 12 MPa for 4 min. The results were compared with those of non-densified veneers. The colour change of the samples was evaluated by CIEL*a*b* and L*h*C* colour co-ordinate systems. The results indicated: the temperature and pressure of densification affected to a big extent the colour of the veneer samples, with the effect of densification temperature being more evident than that of pressure. After the densification process, the veneers darkened. Colour changes are most pronounced at the highest densification temperature of 200 °C and very small at the lower temperatures of 100 and 150 °C for all investigated wood species. The change in a* is more pronounced than the change in L* or b*. In general, alder and birch veneer samples are characterized by the highest values of total colour difference followed by pine and beech samples among the four species. The quadratic models can be used for the prediction of surface colour in the densification process. The results of this study indicate that it is possible to govern surface colouration of wood veneers during densification process on an industrial basis.