影响乙丙橡胶胶液洗涤脱钒效果的探讨

研究了以水为失活剂和洗液,来探讨影响乙丙橡胶（EPR）胶液洗涤效果的各种因素。结果表明,提高温度、增加混合程度、加入NaOH等方式,能提高EPR胶液洗涤效果,降低产品中的钒含量。     

An Engineer Asks: Is it Really More Important that Paint Stays Stuck on the Outside of an Aircraft than that Glue Stays Stuck on the Inside?

The purpose of this article is to draw attention to two problems encountered with modern aircraft: the difficulties in making adhesive and paint adhere to composite substrates and the lack of any after-the-fact inspection that can prove that there will not be any interfacial failures at some time during the service life. It is also observed that the response to paint peeling off is more rapid and thorough than to a discovery of separations between internal components that were once believed to have been bonded together. Because there is so much similarity between the processes of making paint and adhesive adhere, it is suggested that some of the efforts to improve adhesion of the paint might also help improve the processes for making adhesives stick. The article focuses on a series of anecdotes about problems and their resolutions, with the hope that the solutions might help others solve or avoid future such problems. It is pointed out that the cost of improving the adhesion of both paint and adhesive has always been insignificant in comparison with the sometimes enormous costs incurred as a result of fleet-wide occurrences of what were perceived to be bond “failures” but which should more properly be characterized as initially undetected nonbonds. A critical issue is the acknowledged absence of any nondestructive inspection capable of distinguishing between bonds that will “fail” in service and those that will not. Experience has shown that none of the apparent interfacial failures to date have occurred on grit-blasted surfaces. Equally, it must be conceded that not all of the bonded composite structures made using peel-ply surfaces can be expected to fail, even though those associated with released peel plies or prebond moisture probably will, because these conditions have been associated with so many of the past failures. The distinction between interfacial failures and impact damage to properly bonded structures is that the former can extend throughout the entire structure, whereas the broken fibers and interlaminar matrix failures associated with the latter will not extend far beyond the impact area. This is one reason why it is so important to use only surface preparations that ensure the absence of interfacial failures. It is also noted that there is no counterpart, for the bonding of composite structures, of the peel-type test that was so instrumental in solving the equivalent bonding problem that was widespread in bonded metal structures some 30 years ago. It is recommended that there should be, because the use of only shear-load tests has been found to be insufficient to ensure bond durability for both metallic and composite structures.     

The Effect of Moisture Content in Epoxy Film Adhesives on their Performance. III: Bulk Properties

Humidity absorbed by epoxy film adhesives during low temperature storage or exposure to atmosphere may result in reversible changes and irreversible modifications. Vacuum treatment may partially remedy the reversible changes. The consequences of vacuum drying are manifested in enhancement of both the peel and shear properties of bonded joints (Part I and Part II of this series of papers) and the thermal, physical and mechanical properties of the bulk adhesive, characterized in the present study.

Experimental results have shown that the bulk properties of structural epoxy based adhesives are highly correlated with the aging processes caused by water absorption in the prepolymerized adhesive. Applying the vacuum process is harmful to fresh unaged adhesive due to devolatization of low molecular species of the film adhesive.

The characterization of bulk properties for the purpose of following the aging and recovery processes is advantageous, since the bulk is independent of geometrical and interfacial effects which dominate in the case of property evaluation of the adhesive in a bonded joint.     

Effect of Maltodextrin Addition during Spray Drying of Tomato Pulp in Dehumidified Air: II. Powder Properties

This work investigates the effect of maltodextrin addition on the main powder properties during spray drying of tomato pulp in dehumidified air. A pilot-scale spray dryer was employed for the spray-drying process. The modification made to the original design consisted in connecting the spray dryer inlet air intake to an absorption air dryer. 21 DE, 12 DE, and 6 DE maltodextrins were used as drying agents. Tomato pulp was spray dried at inlet air temperatures of 130, 140, and 150°C and (tomato pulp solids)/(maltodextrin solids) ratios of 4.00, 1.00, and 0.25. The tomato powders were analyzed for rheological properties, moisture content, bulk density, solubility, hygroscopicity, and degree of caking. It was found that maltodextrin addition improved powder hygroscopicity, caking, and solubility, whereas it deteriorated slightly its moisture content and density. In addition, analysis of experimental data yielded correlations between powder properties and the above-mentioned variable operating conditions. Regression analysis was used to fit a full second-order polynomial, reduced second-order polynomials, and linear models to the data of each of the properties evaluated. F values for all reduced and linear models with an R ² ≥ 0.70 were calculated to determine if the models could be used in place of full second-order polynomials.     

Encapsulation Efficiency of Food Flavours and Oils during Spray Drying

Microencapsulation is a rapidly expanding technology which is a unique way to package materials in the form of micro- and nano-particles, and has been well developed and accepted within the pharmaceutical, chemical, food and many other industries. Spray drying is the most commonly used encapsulation technique for food products. A successful spray drying encapsulation relies on achieving high retention of the core materials especially volatiles and minimum amounts of the surface oil on the powder particles for both volatiles and non-volatiles during the process and storage. The properties of wall and core materials and the prepared emulsion along with the drying process conditions will influence the efficiency and retention of core compounds. This review highlights the new developments in spray drying microencapsulation of food oils and flavours with an emphasis on the encapsulation efficiency during the process and different factors which can affect the efficiency of spray drying encapsulation.     

Impact of Instant Controlled Pressure Drop Treatment on Moisture Adsorption Isotherm of Cork Granules

Some special thermal and mechanical treatments may completely modify the composition, and the structure of organic material changes its interaction with water. In the case of the instant controlled pressure drop (DIC) technique, the main modification, which is structure expansion and high porosity, allows the product to generally reduce moisture activity. In the special case of cork granules, the impact of DIC in terms of porosity is completely absent and expansion is linked to a tear effect obtained from only the large size granules. In order to characterize this type of treatment, we considered natural and DIC-treated cork granules and determined moisture adsorption isotherms at three different temperatures (25, 40, and 60°C) and different water activity levels ranging from 0.05 to 0.9 using the static gravimetric method. We used three samples of the same cork variety with 0.5–1 mm, 2–4 mm, and 4–6 mm as granule diameter. The adsorption isotherms of both natural untreated and DIC-treated cork whatever granules display a sigmoid form type II isotherm, with equilibrium moisture contents at constant water activity decreasing when temperature increases. The impact of DIC treatment depends of cork shape; the larger the shape, the lower the water activity for the same water content. Such a result is linked to the modification of structure. Thus, for the smallest shape, DIC implying only low thermal effect without any structure modification allows cork to lightly increase its water activity compared to the untreated samples. With higher shape cork granules, as DIC treatment induces a tear effect and some expansion, activity of water is lower for the same water content. For describing the experimental data of adsorption isotherms, we used GAB, BET, and Henderson models. We found the GAB to be the most suitable model with predicted values higher than those obtained using the BET model. We note that monolayer moisture content values increase in the case of big shape cork granules after having been treated by DIC.     

Modeling Shrinkage Response to Tensile Stresses in Wood Drying: I. Shrinkage-Moisture Interaction in Stress-Free Specimens

This article reports on the wood shrinkage during drying in relationship with the temperature and moisture content. All tests were performed perpendicular to the grain on small clear wood specimens of green Western hemlock while drying at 40, 60, and 80°C to 17, 11, and 5% final moisture contents. Overall, wood dimensional changes and moisture loss phenomena were successfully analyzed and interpolated. The shrinkage strain followed a nonlinear pattern with the moisture loss being the driving force and exhibited good correlation with the square value of moisture content in tangential, and linear moisture values could be used to describe shrinkage in radial direction. Both shrinkage intersection points and end of capillary water values increased with temperature; the distinction between the two values could not be made at all times. A nonlinear function containing two regression coefficients (α and β) was found to be a good interpolation of the moisture loss experimental data. Further analyses revealed that β is independent of both target moisture content and temperature, whereas α appears to be influenced by both variables. The correlation between shrinkage and moisture loss rate is intended to be used as a stress prediction tool.     

A Novel Method of Measuring Moisture Content Distribution in Timber During Drying Using CT Scanning and Image Processing Techniques

A new method for the nondestructive measurement of moisture content (MC) distribution in timber during drying was developed using X-ray computed tomography (CT) scanning and image processing techniques. The deformed cross section in the CT images due to shrinkage was corrected with the image registration, and the shrinkage was measured by digital image correlation analysis. The pixel-wise MC distributions during drying were measured and visualized successfully. The total timber MC estimated from the MC values of each pixel were strongly correlated with those measured by calculation without geometrical transformation of CT images. The coefficient of determination (R ²) and the standard error of prediction (SEP) were 0.99 and 0.18%, respectively, within the MC range of 19.2–47.3%. In addition, the measured shrinkage distribution during drying was in accordance with the diamonding deformation observed. The results suggest that CT scanning combined with image processing techniques is an effective tool for nondestructive assessment of MC distribution during drying.     

Testing New In-Kiln Meter for Monitoring Lumber Moisture Content during Drying

The objective of this study was to test a new in-kiln sensor for monitoring lumber moisture content during industrial drying. The theoretical foundation of the technology was already known, because it is based on electrical conductivity, but the mechanism of implementation was new and required validation. For this reason, the technology was compared with two other widely used methods for assessing lumber moisture content, namely, the oven-drying and electrical capacitance methods. The tests were performed in a 120-m³ industrial kiln operated by a sawmill in the eighth region of Chile, and the results showed that the average moisture content at the end of drying was satisfactorily determined by the new in-line sensor. As predicted by theory, the sensor was not able to accurately measure moisture content above 25%, but it was still able to provide the equivalent of a drying curve for monitoring of the drying process.     

The impact of drying and steaming processes on surface color changes of tension and normal beech wood

Abstract

Beech wood has a high frequency of defects such as red heartwood, reaction wood (tension wood). For the experimental measurements four logs without visible defects like red heartwood, which can noticeably affects the measurements' results were qualified. The drying medium temperature in the first phase of the process before the moisture content of the specimens fell below the FSP was maintained at 45?°C. Then, the temperature was gradually increased to the maximum value 65?°C. The results showed that different initial wood moisture content does not affect to final value of tension and normal wood. The colorimetric parameter L* was much higher for tension wood. After steaming, there were greater differences in the colorimetric parameters, respectively, a* and b*. After drying the difference of all colorimetric parameters between tension and normal wood was significantly less. The color changes were only noticed in the surface layers of specimens. Differences were small, and thus, the impact of the tension wood on the color changes was not confirmed. However, since the lightness of tension wood plays a key role for its visual detection, it may be adequate to only measure the lightness parameter (L*).