Investigation of the mechanical and dispersible properties of wood pulp/Danufil wetlaid nonwovens with/without hydroentanglement

A new wiping product prepared by wetlaid/spunlace (wetlace) method possess dispersibility and fully degradability. To obtain the excellent products, the present research first investigates the apparent microstructures, mechanical properties and dispersibility of wood pulp/Danufil wetlaid nonwovens with/without hydroentanglement. The results suggest that fibers are stacked and some of the fiber cohesions occurred on the surface of wetlaid nonwoven. After hydroentanglement, a 3D entanglement skeleton formed by Danufil fibers is found to determine the mechanical and dispersion properties of nonwovens, while wood pulp ensures the dispersion properties and is attributed as the main component of the nonwovens. The breaking extension and tearing strength of nonwovens have been improved significantly and the material with decreasing dispersibility becomes soft. Meanwhile, the dispersion of wetlaid and wetlace nonwovens over time both show linear fitting trend. The increase in content and length-to-diameter (L/D) ratio of Danufil fiber results in the increase in tensile and tearing strength, and the decrease in bending rigidity and dispersion performances of materials. Moreover, the wetlaid nonwovens developed in this study may become promising candidate for the disposable sanitary products.     

Tensile strength properties of particle boards at different temperatures and moisture contents

The equilibrium tensile properties of urea-formaldehyde (UF)- and phenol-formaldehyde (PF)-bonded particle boards have been studied at moisture contents between 1 and 33% and at temperatures between ?15°C and +45°C. These conditions may occur e.g. during exterior use of the boards. The tensile strength and the modulus of elasticity decrease slightly while the strain at rupture increases slightly between 1% and 7% moisture content. These effects are similar for UF- and PF-bonded boards. Above 7% moisture content the tensile strength and the modulus of elasticity decrease markedly while the stretch at rupture increases with increasing moisture content. These changes are more pronounced for UF-bonded boards. The bending stiffness is less affected than the modulus of elasticity since the board thickness increases with increasing moisture content. The tensile properties are not significantly affected by the temperature at low moisture contents, but at high moisture contents the combined effects are more pronounced. The effect of moisture is generally stronger than that of temperature, in the range studied.     

湿法水刺可分散材料的结构与性能及其发展趋势

针对现有一次性湿纸巾使用后不可降解,且丢入抽水马桶易堵塞城市管道等难题,从制备工艺、纤维构成、材料属性与用途等角度阐述新型可分散可降解湿法成网水力缠结湿纸巾基材,同时比较分析该材料结构特征及其使用性能（湿强,分散和手感）。结果表明：材料由长短纤维缠绕抱合构成,具有非织造材料与纸二者属性,长纤维（短切再生纤维素纤维）缠绕抱合作为纤维增强影响着材料的湿强和分散性,材料手感与梳理水刺材料接近。最后对该材料发展趋势,从短切纤维优化、辅助增强体应用与设备工艺改进等角度进行系统阐述。     

On the tribological properties of extremely different wood materials

Three different woods (lignum vitae; black fiber palm; spruce) were investigated regarding their friction and wear properties under abrasion and sliding. For the abrasive wear against silicon carbide paper, the palm wood gave the lowest removal of material, especially under an orientation of the black fibers normal to the contact region (on R–T-plane in R-direction). At the same time, this material had the highest anisotropy. Slightly less abrasion resistant was lignum vitae, whereas spruce was most easily abraded. This can be considered as an indication that spruce can easily be machined. Under sliding conditions against smooth steel, a similar tendency, but at much lower wear rates compared to abrasion, was found. The relatively high coefficient of friction under dry sliding allows the use of these woods as friction materials, for example in brakes. Additional lubrication of the two best woods, lignum vitae and black fiber palm, by soaked sunflower oil brought the coefficient of friction to a much lower level, so that the use of these woods as bearing materials in various applications is promising.

     

含水率对木质材料切削力影响的研究

采用硬质合金锯齿刀具分别对三种实木(杉木、樟子松、水曲柳)和两种人造板(中密度纤维板、刨花板)进行闭式切削实验,研究不同含水率对木质材料切削力的影响。实验结果表明:含水率对木质材料切削力的影响显著。随着含水率的增加,杉木的主切削力和法向力都呈减小趋势,而樟子松和水曲柳的主切削力皆为先增大后减小,当接近纤维饱和点含水率时主切削力达到最大。对人造板,在5%～18%含水率范围内,随着含水率的增加,主切削力和法向力都不断增大。     

Storage experiments with barley at different moisture contents

Storage experiments were conducted in specially constructed silos each containing 10 kg barley at different moisture contents under controlled conditions at 20°C. Barley at 12 and 14 % moisture stored satisfactorily without mould development during an experimental period of 30 weeks. At increasing moisture contents a good correlation was found between increases in mould growth, CO₂ production and contents of reducing sugars, and decreases in non-reducing sugars and in germinative capacity. At the higher moisture contents, temperature rise took place and the feeding quality to rats was impaired Among the storage moulds Aspergillus was the predominating genus at moisture contents up to about 18%, while Penicillium spp. were prevalent at higher moisture contents. At the highest moisture content(26%) Fusarium spp. also developed vigorously. After storage, the barley was steeped and sprouted in micromalting equipment; Fusarium and Aspergillus developed more vigorously than in the barley, particularly in green malt produced from barley with a high moisture content.     

不同水分含量巴西大豆储存期间的品质变化

为科学判定我国进口巴西大豆在储存期间的品质变化,采用模拟储存试验的方式,对不同水分含量巴西大豆在储存过程中粗脂肪、脂肪酸值和脂肪酸相对含量的变化进行监测。结果表明,巴西大豆在储存6周后,营养指标会出现不同程度的变化,储存28周时粗脂肪含量下降0.52~1.76个百分点,脂肪酸值(KOH)升高3.38~105.48 mg/100 g,亚油酸和亚麻酸的相对含量均呈现不同程度的下降。超过安全水分值(12%)越高,大豆品质下降越明显。低于安全水分值的大豆在储存18周后,品质开始发生较明显变化。因此,认为低水分含量(≤12%)大豆最佳储存期在18周内,高水分含量(>12%)大豆最佳储存期在6周内。通过试验不仅能够准确判定巴西大豆储存过程中的品质随时间的变化,也可以指导国家和地方大豆储备库对大豆的管理,保证大豆安全储存。     

Investigation on permeability and moisture management properties of different denim fabrics after repeated laundering

The physiological comfort determined by air permeability and moisture management properties of fabrics is influenced by various constructional parameters of the fabric which give woven fabric a porous structure. Evaporation of sweat during wear has the potential to cool the body besides restricting the additional weight of sweat being absorbed by the fabric. In this study, comfort characteristics of denim fabrics with different weft yarn of cotton, polyester and core spun Lycra have been discussed. Effect of enzyme washing and repeated laundering on air permeability, moisture management and drying rate has also been discussed. It was observed that air permeability and water vapour permeability of unwashed denim fabrics with cotton weft yarn are significantly higher than the fabric with polyester and Lycra cotton weft yarns. The wetting time is higher for cotton and Lycra cotton yarn fabrics. One-way transport index is highest for Lycra cotton weft fabrics and lowest for fabrics with polyester weft. Fabrics with polyester weft yarns show highest spreading rate, spreading radius and drying rate due to better wicking and hydrophobic nature of polyester fibres.     

Physicochemical, mechanical and thermal properties of brown rice grain with various moisture contents

The effects of moisture content on the mechanical and thermal properties of either a short‐grain variety (Akitakomachi) or two long‐grain varieties (Delta and L201) of brown rice were studied. Total starch contents of the three varieties were comparable, but the amylose content of L201 was significantly higher than that of the other two varieties. The maximum compressive strength of brown rice grain was much higher than the maximum tensile strength. L201 showed the highest maximum compressive and tensile strengths. The phase transition temperatures (glass transition temperature T_g and melting temperature T_m) were examined by differential scanning calorimetry. The T_g and T_m for L201 were higher than those for Delta and Akitakomachi. The maximum compressive strength, maximum tensile strength, T_g and T_m for the three varieties of brown rice grains decreased with increasing moisture content. The T_g of individual brown rice kernels decreased from 53 to 22 °C as moisture content increased from 12 to 25% wet basis. A statistical model was calculated by using linear regression to describe the change in T_g in terms of moisture content.     

Moisture-dependent orthotropic elasticity and strength properties of Chinese fir wood

Elastic and strength properties are very important material characteristics in mechanical modelling. Due to the anisotropic and hygroscopic nature of wood, a characterization of wood mechanical behavior will require knowledge of its moisture-dependent properties in relation to the three principal axes of anisotropy. The influence of moisture content (MC) on the elastic and strength anisotropy of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook) wood was examined in the present study. Selected parameters, including the anisotropic Young’s moduli, shear moduli, Poisson’s ratios, yield and ultimate stress values in the longitudinal, radial and tangential directions, were determined in compression and tension tests at different moisture conditions. The results indicated that a distinct moisture dependency is exhibited for the elastic and strength behavior of Chinese fir wood. With the exception of some Poisson’s ratios, all investigated elastic and strength parameters were shown to decrease with increasing MC, whereby individual moduli and strength values were affected by the MC to different degrees. The two- and three-dimensional representation of the compliance matrix and the two-dimensional visualization of a yield surface give a valuable overview on the moisture-dependent elastic and strength anisotropy of Chinese fir wood.     

Lifetime,residual strength,and quality of wood and other viscoelastic building materials

A theoretical analysis of the influence of wood quality on dead load lifetime is made on the basis of the authors DVM concept of building materials (Damaged Viscoelastic Material). It is shown that low quality structural wood and high quality clear wood lives longer than normal clear wood when loaded to the same fraction of respective strengths. At middle range qualities lifetime is practically not influenced by quality. Also considered is residual strength of wood during its lifetime experience. The results presented are valid in principle for a number of building materials applying to the DVM concept.     

Experimental determination of thermal conductivity of apple and potato at different moisture contents

Thermal conductivity of apple and potato samples was measured by means of a specifically designed apparatus based on Fitch's method. The thermal conductivity was determined at various moisture contents at the sample mean temperature of 30 °C. As expected the conductivity decreases with the decrease in moisture content. Thermal conductivity data were correlated with moisture content using a straight line.     

不同水分大米储藏品质变化规律研究

在实验室人工模拟条件下控制大米的储藏温度和水分,对储藏大米进行了为期13个月的试验研究。在研究期间对影响大米质量的感官指标、脂肪酸值等数据进行定期检测。结果表明：高水分大米经高温条件下储藏,当脂肪酸值达25mgKOH／100g时是大米的安全储藏期限;较低水分的大米常温或准低温下储藏,其安全期限以感官指标来判定。提出了不同含水量的大米在不同温度下的安全储藏期限。     

Fermentation of texturized vegetable proteins extruded at different moisture contents: effect on physicochemical,structural, and microbial properties

Food Science and Biotechnology - To investigate the effect of fermentation on texturized vegetable protein (TVP), TVPs extruded at 40 and 50% feed moisture contents (MC) were fermented using...     

Rheological properties and microstructure of Cheddar cheese made with different fat contents

Reduced- and low-fat cheeses are desired based on composition but often fall short on overall quality. One of the major problems with fat reduction in cheese is the development of a firm texture that does not break down during mastication, unlike that observed in full-fat cheeses. The objective of this investigation was to determine how the amount of fat affects the structure of Cheddar cheese from initial formation (2 wk) through 24 wk of aging. Cheeses were made with target fat contents of 3 to 33% (wt/wt) and moisture to protein ratios of 1.5:1. This allowed for comparisons based on relative amounts of fat and protein gel phases. Cheese microstructure was determined by confocal scanning laser microscopy combined with quantitative image analysis. Rheological analysis was used to determine changes in mechanical properties. Increasing fat content caused an increase in size of fat globules and a higher percentage of nonspherical globules. However, no changes in fat globules were observed with aging. Cheese rigidity (storage modulus) increased with fat content at 10°C, but differences attributable to fat were not apparent at 25°C. This was attributable to the storage modulus of fat approaching that of the protein gel; therefore, the amount of fat or gel phase did not have an effect on the cheese storage modulus. The rigidity of cheese decreased with storage and, because changes in the fat phase were not detected, it appeared to be attributable to changes in the gel network. It appeared that the diminished textural quality in low-fat Cheddar cheese is attributed to changes in the breakdown pattern during chewing, as altered by fat disrupting the cheese network.     

不同成型工艺棕叶纤维/PHBV复合材料的力学性能

研究了精细化棕叶散纤维/PHBV热压复合、棕叶纤维针刺非织造布/PHBV热压复合、棕叶纤维粉末/PHBV共混复合材料的力学性能。以拉伸强度、冲击强度、弹性模量、断裂伸长率为指标探讨了PHBV质量分数、热压压强的影响,并通过SEM观测了复合材料的拉伸断面形貌。结果表明:当PHBV质量分数相同时,棕叶纤维针刺非织造布/PHBV热压复合材料的力学性能最佳,且PHBV质量分数的最优值为35%;当热压压强为13.5 MPa时,热压复合材料可获得最佳的拉伸与冲击性能;棕叶纤维针刺非织造布/PHBV热压复合材料的拉伸断面光滑,少有纤维从基质中拉出;棕叶纤维粉末/PHBV共混复合材料的拉伸断面中存在一定的团聚现象,导致PHBV的包裹性变差,结合力降低。     

Fat oxidation in freeze-dried grouper during storage at different temperatures and moisture contents

The effects of moisture content levels and storage temperature on the lipid oxidation in freeze-dried grouper were studied. Three trends were observed in the changes of PV (peroxide value) depending on the moisture content and storage temperature. An exponential rise of PV was observed (p < 0.05) at lower temperatures (−20 °C and 5 °C for samples at moisture 5 g/100 g; and −20 °C for samples at moisture 20 g/100 g). At temperatures 25 °C for samples at moisture 5 g /100 g, and 5 and 25 °C for samples at 20 g moisture/100 g peaks of PV were observed (p < 0.05). At higher temperatures (40 °C for both moisture content levels) an exponential decay instead of increase were observed (p < 0.05). Moisture content levels had no significant effect (p > 0.05) on PV stored at temperature of −40 °C. The monolayer moisture for freeze-dried grouper was estimated as 6.2 g/100 g dry solids using BET-isotherm. Differential scanning calorimetry (DSC and modulated DSC) thermogram line showed two shifts (i.e. glass transition) and two endothermic peaks, one for melting of oil and another for decomposition. The validity of the water activity and glass transition concepts were evaluated. It is concluded that glass transition concept may be used to explain the process more adequately.