Fast vs. slow-reacting non-modified tannin extracts for exterior particleboard adhesives

Non-fortified, non-modified tannin extracts, rather than chemically-modified tannin adhesives intermediates, can be used as effectively to produce excellent exterior grade particleoboard at fast pressing times of industrial singnificance, with considerable advantages in both handling and cost. This can be achieved by simple pH-controlled reactivity adjustments of the tannin extract in the glue mix. This new concept is shown to be applicable to all types of polyflavanoid tannin extracts: Pine, mimosa, pecan, quebracho, and gambier tannin extracts are compared as regards their performance and capabilities. The new concept applied to the faster-reacting tannins, such as pine tannin and pecan tannin extracts, is shown to produce fast hot-pressing rates and excellent high moisture content tolerances which are undreamed of for the slower-reacting tannins, modified or non-modified, which are traditionally associated with thermosetting wood adhesives. Industrially used techniques to control well viscosity and pot-life of the glue-mixes of accelerated tannin adhesives are also presented.     

Effect of tannin on increasing UF adhesive performance at high temperature investigated by TMA and TGA analysis

Tannins have been largely studied as wood additives and wood adhesives. In a perspective of a desirably increased utilization of natural raw material in the wood timber industries, this study provides further and specific information on the use of condensed tannins to improve the heat resistance of urea–formaldehyde (UF) resins. The results obtained by thermomechanical and thermogravimetric analyses show that high percentage (33 and 50 %) of quebracho tannin in UF-tannin blend dramatically improves the overall UF thermal resistance, but 50 % of tannin decreases the maximum value of modulus of elasticity (MOE) of the bonded joint. The best balance between mechanical performance and decreased degradation at high temperature is obtained with 33 % of quebracho tannin. The MOE value of UF + 33 % of quebracho tannin at 260 °C is seven times greater than MOE of UF control. Thermograms show that quebracho tannin has a beneficial effect on increasing the resistance of glue-mix to degradation induced by temperature. When the content of tannin in the glue-mix is increased up to 50 %, the resin degrades completely at about 670 °C, i.e. more than 50 °C higher than neat UF resin. This improvement is related mainly to the resorcinol-type ring structure of tannin and the alkaline pH of UF + quebracho tannin glue mix that confer a higher resistance against joint degradation to UF even at elevated temperatures.     

Deactivation of tannin in high tannin milo by treatment with urea

Experiments were conducted to determine the effectiveness of urea in deactivating tannin in high tannin milo. High tannin milo (Pioneer B 815, 3.4 +/- .3% tannin) was reconstituted with aqueous urea solutions to give combinations of 26, 30, and 34% moisture with 2, 3, and 4% urea (percentage of urea per dry weight of milo). All treatments were maintained at 25 degrees C and were effective in deactivating tannin with no differences among moisture or urea content. The average rate of tannin deactivation was 68 +/- 2% d-1. Temperature affected rate of tannin deactivation in milo reconstituted to 30% moisture and 3% urea when stored at 25 or 60 degrees C. Rate of tannin deactivation was 44 +/- 5 and 89 +/- 18% d-1 at 25 and 60 degrees C, respectively. Tannin in high tannin milo can be deactivated rapidly and completely by reconstitution with aqueous urea. These studies demonstrate that tannin is deactivated completely under conditions where urea is an effective preservative of high moisture milo.     

Steps to make the natural adhesive of Acacia mimosa tannin resistant to boiling water using Tinnevelly senna for particleboard production

Adding a small amount of Tinnevelly senna seed flour to the natural adhesive of condensed tannin from acacia mimosa type decreases the thickness swelling and water absorption in particleboards significantly. Likewise, internal bond, modulus of rupture and modulus of elasticity increase. FTIR did not show any change in the adhesive structure. DSC and TGA showed a link between the additive of Tinnevelly senna and natural adhesive of acacia mimosa tannin, which obviously brings about the resistance to boiling water in particleboard manufacturing when using this adhesive mix.     

刨花板制造包装材料的研究

以松木刨花和麦秸为原料制造松木竹贴面刨花板以及麦秸刨花板,并探讨其作为包装材料的可行性。对板材的部分物理力学性能进行测试后得出如下结论:除24h吸水厚度膨胀率外,竹表面增强松木刨花板的力学性能达到了国标要求;竹表面增强松木刨花板与麦秸刨花板改进工艺后有望成为新型包装材料。     

采用TMA技术研究山羊绒纱线的热学性能

采用热机械分析技术(TMA)研究了山羊绒单纱在4种不同恒定拉伸应力及压缩应力(6 MPa)下,单纱形变与温度的关系.研究表明,在很小的拉伸应力(0.01 MPa)及压缩应力(6 MPa)下,山羊绒单纱在219℃收缩,而在230℃突变伸长,此收缩起源于山羊绒纤维中α-螺旋结晶的熔融,突变伸长起源于山羊绒纤维的"粘流",即山羊绒纤维结晶熔融后发生"粘流";而在较高的拉伸应力条件(200 MPa)下,山羊绒单纱在190℃就发生突变伸长,即山羊绒纤维的"粘流"温度低于结晶熔融温度.     

葡萄酒活性干酵母的研究 Ⅰ.葡萄酒活性干酵母的生产和应用

以2株葡萄酒酵母1450(Saccharomyces cerevisiae)和Am_(-1)(saccharomyces bayanus)为试验菌株,进行了活性干酵母的培养和干燥等工艺条件的研究。对活性干酵母在酿酒中的应用技术也进行了研究。试验结果表明,活性干酵母的制备工艺是可行的。活性干酵母1450和Am_(-1)适用于酿制干型葡萄酒和其它果酒。与野生酵母的自然发酵结果相比,干酵母发酵平稳彻底,发酵时间较短,发酵结束时,干酵母的沉淀较好,原酒含残糖量和挥发酸量低,酿制的酒质量和风味较好。     

Aroma release of a model wine solution as influenced by the presence of non-volatile components. Effect of commercial tannin extracts, polysaccharides and artificial saliva

The effect of commercial tannin extracts, extracted either from grape seeds or grape skins, a natural wine polysaccharide extract, pectin and arabinogalactan on the headspace release of selected aroma compounds from a “model wine” solution was investigated. Changes in the volatility of the aroma compounds were studied using headspace solid-phase microextraction combined with GC/FID. The performance of four commercially available fibre coatings was checked and the 50/30 ??m DVB/CAR/PDMS one was proved to be the most effective. A short sampling time (1 min) was used to determine the “true” headspace concentration at equilibrium between the headspace and the sample. In general, the volatility of the studied aroma compounds appeared to be correlated to increasing tannin levels as well as to their origin. The volatility of esters was generally increased upon tannin addition at low concentrations, while at higher addition levels the two extracts exhibited dissimilar behaviour attributed to their different composition. Both arabinogalactan and pectin addition at low concentrations increased the volatility of the studied aroma compounds, while at higher concentrations pectin exhibited a different behaviour by salting out hydrophobic compounds in the vapour phase. In addition, grape skin and seed tannin extracts in admixture with polysaccharides either prevented the macromolecular chains to associate with volatile molecules or led to additional flavour retention depending on the aroma compound and the addition level. Saliva addition enhanced the volatility of the most hydrophobic compounds whereas the hydrophilic compounds were retained into the matrix.     

单宁法提取生姜蛋白酶

用丙酮和鲜姜汁制取丙酮粉,得率为8.6%。以丙酮粉为酶源,用单宁沉淀法提取生姜蛋白酶的最适条件:pH为6.0,浸提时间为35min,单宁浓度为0.12%,得率为1.1%。在一定浓度范围内,单宁与生姜蛋白酶结合不会变性失活。     

Structure and performance of commercial kappa-2 carrageenan extracts: I. Structure analysis

Extracts of two Chilean carrageenophyte red seaweeds, Sarcothalia crispata and Gigartina skottsbergii, were prepared by each of two industrial processes: a mild alkaline extraction with aqueous sodium hydroxide and a more vigorous aqueous alkaline extraction with lime. The resulting extracts, recovered by precipitation with isopropyl alcohol, were separated into gelling and non-gelling fractions by leaching with 2.5% KCl. These processes were also applied to Chondrus crispus and to separated gametophyte and sporophyte samples of the Chilean seaweeds for comparative purposes. The carrageenan compositions of these extracts and fractions were determined using both chemical and spectroscopic techniques. In addition, a set of decision rules is proposed and applied to convert data from glycosyl linkage analysis to carrageenan composition. The gametophyte extracts contained mixtures/hybrids of kappa and iota carrageenans (and also mu and nu carrageenans, depending on the extraction conditions used). The tetrasporophyte extracts contained lambda carrageenan (and also theta carrageenan, depending on the extraction conditions used). Extractive fractionation of mixed life phase samples using 2.5% KCl yielded insoluble, ‘gelling’ carrageenans quite similar to those from a gametophyte extract of the same species, but the soluble, non-gelling fractions were not the same as the corresponding sporophyte extracts.     

Dimensional stabilisation and strength of particleboard by chemical modification with propionic anhydride

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Dimensionsstabilit?t und Festigkeit von Spanplatten nach Modifikation der Chips mit Propionanhydrid