Performance of Citric Acid-Bonded Oriented Board from Modified Fibrovascular Bundle of Salacca (Salacca zalacca (Gaertn.) Voss) Frond

The fibrovascular bundle (FVB) in palm plants consists of fiber and vascular tissue. Geometrically, it is a long fiber that can be used as an oriented board raw material. This research aimed to examine the performance of citric acid-bonded orientation boards from modified FVB salacca frond under NaOH + Na2SO3 treatment and the bonding mechanism between the modified FVB frond and citric acid. The results showed that changes in the chemical composition of FVB have a positive effect on the contact angle and increase the cellulose crystallinity index. Furthermore, the mechanical properties of the oriented board showed that 1% NaOH + 0.2% Na2SO3 with 60 min immersion has a higher value compared to other treatments. The best dimension stability was on a board with the modified FVB of 1% NaOH + 0.2% Na2SO3 with 30 and 60 min immersion. The bonding mechanism evaluated by FTIR spectra also showed that there is a reaction between the hydroxyl group in the modified FVB and the carboxyl group in citric acid. This showed that the modified combination treatment of NaOH+Na2SO3 succeeded in increasing the mechanical properties and dimensional stability of the orientation board from the FVB salacca frond.

Análise da Vulnerabilidade Ambiental do Município de Inconfidentes - MG

A crescente ocupação de forma desordenada e desigual nos municípios brasileiros tem desencadeando desequilíbrios nos sistemas ambientais, gerando problemas de ordem funcional e estrutural no meio. Numa política que prima pela conservação e preservação ambiental, essa realidade demanda, cada vez mais, estudos prévios considerando as potencialidades e limitações dos sistemas naturais, como subsídios para o planejamento e gestão territorial. Nesse sentido, este artigo teve como objetivo realizar a análise e mapeamento da vulnerabilidade ambiental do Município de Inconfidentes – MG, segundo a metodologia estabelecida por Crepani et al. (2001). Os materiais e métodos abrangeram, além de atividades de campo, interpolação geoestatística, processamento digital de imagens e análise geoespacial, por meio de álgebra de mapas. Após mapeamento, foram definidos os graus de vulnerabilidade para as categorias geologia, geomorfologia, pedologia, clima, uso e ocupação da terra. O mapeamento de vulnerabilidade natural à perda de solo foi obtido a partir da média das variáveis geoambientais com seus respectivos pesos, via álgebra de mapas. Os resultados demonstraram que a maior parte do município, aproximadamente 66%, apresentam baixo grau de vulnerabilidade, com maior estabilidade ambiental e com predomínio do processo de pedogênese. Contudo, embora correspondendo a um percentual menor, as áreas com vulnerabilidade intermediária e com equilíbrio entre os processos de pedogênese e morfogênese demandam maior atenção do poder público e da sociedade, visando evitar a desestabilização destes meios e a instauração de processos degradacionais. Analysis of Environmental Vulnerability in the Municipality of Inconfidentes - MG A B S T R A C TThe increasing occupation in a disorderly and unequal way in Brazilian municipalities has triggered imbalances in environmental systems, generating functional and structural problems in the environment. In a policy that focuses on environmental conservation and preservation, this reality demands, more and more, previous studies considering the potentialities and limitations of natural systems, as subsidies for planning and territorial management. In this sense, this article aimed to perform the analysis and mapping of the environmental vulnerability of the Municipality of Inconfidentes - MG, according to the methodology established by Crepani et al. (2001). The materials and methods covered, in addition to field activities, geostatistical interpolation, digital image processing and geospatial analysis, through map algebra. After mapping, the degrees of vulnerability were defined for the categories geology, geomorphology, pedology, climate, land use and occupation. The mapping of natural Vulnerability was obtained from the mean of the geoenvironmental variables with their respective weights, via maps algebra. The results showed that the majority of the municipality, approximately 66%, has a low degree of vulnerability, with greater environmental stability and a predominance of the pedogenesis process. However, although corresponding to a smaller percentage, the areas with intermediate vulnerability and balance between pedogenesis and morphogenesis processes require greater attention from the public authorities and society, with a view to preventing the destabilisation of these resources and the introduction of degradational processes.Keywords: Map algebra, average interfluvial dimension, stability of natural systems, valley’s depth, geostatistical interpolation, morphogenesis-pedogenesis relationship

Copolymers and interpenetrating polymer networks of thermoreactive nitrogen-containing resins. Mini review

In a short review the effective methods of optimization of structure and properties of high-performance polymers obtained from thermoreactive nitrogen-containing resins such as benzoxazines, bismaleimides, cyanate esters have been analysed. High crosslinked density copolymer thermosets are synthesized through chemical interactions between reactive functional groups, which belong to the monomers/oligomers used. The different possible processes such as copolymerization or formation of interpenetrating polymer networks are discussed. The high-performance polymers and composites from thermoreactive nitrogen-containing resins are effectively used in aerospace industry and microelectronics as materials possessing high thermal and thermooxidative stability, radiation and chemical resistance, low water absorption, low dielectric loss, high dimension stability and high adhesion to different substrate. The performance characteristics of this kind of materials can be controlled by changing their composition, temperature-time curing schedule, using catalytic systems. Keywords: copolymers, IPNs, thermoreactive resins, benzoxazine, bismaleimide, cyanate ester resins.

Rigid polyurethane foams modified with borate and oxamide groups – Preparation and properties

In this work the results of the research on modification of rigid polyurethane foams properties by new polyols with borate and oxamide groups have been presented. Propylene glycols — the products of hydroxyalkylation of N,N′-bis(2-hydroxypropyl)oxamide bis(dihydrogenborate) by excess of propylene carbonate (PC) was used as a polyol component. The new polyols have been foamed using polymeric 4,4′-diphenylmethane diisocyanate, water and triethylamine. The modification of the foam structure by oxamide and borate groups guarantees their low water uptake, very good heat-insulating properties, good dimension stability and decreases their flammability, and does not worsen their mechanical properties and thermal stability.

Determination of Swelling and Dimensional Stability of Some Nigerian Timber Species

Aim: The absorption of moisture and dimensional distortion are the major shortcomings of wood utilization as building and furniture materials. This study was aimed at determining the moisture content, swelling ability and dimension stability of five selected timber species. Methods: The samples were collected with the help of the Forest Ranger from the Forestry Department of Enugu State, Nigeria, attached to the Nsukka timber market. The wood samples were evaluated for moisture content change, shrinkage or swelling (%) coefficient, amount of swelling and dimensional change. Results: The change in moisture content across the five species was in the order of Gmelina aborea < Milicia excels < Daniellia oliveri < Alstonia bonnie < Antiaris toxicaria. At 12hrs, Gmelina aborea recorded significantly (P < 0.05) the highest dimension change (46 ± 0.70%) in the radial dimension (direction) as compared to the other species except for Antiaris toxicaria. The swelling coefficient and the amount of swelling were observed to have a strong positive correlation with the dimensional change in the sampled wood. Conclusion: The lower swelling coefficient and the amount of swelling observed in Milicia excels among the five timber species, make it a more suitable species for industrial use.

The Influence of Residual Stresses on Dimension Stability during Thermal Mechanical Processes for High-Precision Components

This paper mainly investigated the revolution of residual stresses and dimension stability in high-precision components during thermal-mechanical processes. Especially, originate of residual stress and its influences on dimension stability, from each step of the design and manufacture processes to thermal-mechanical processes, as well as their complicated interactions were elucidated in detail. Finally, the recent progress of modern analytical and computational techniques were discussed to provide possibilities to quantitative predict and control residual stresses and dimensional stabilities in high-precision components.

Cell Positioning Culture Chip Based on Functional Micro Topological Substrate

There are two main categories of cell positioning culture chips:chemical modification of surfaces and physical structure methods. The chemical methods have the advantage of providing a strong binding force, but the instability of chemical materials limits its application. The physical methods have the advantage of good stability for cell positioning, while the nonspecificity of physical structure weakens the ability to regulate cells. Here, we propose a functional micro topological chip. The chip is composed of micro-platform and micro-post array with different adhesion characteristics. At the same time, the chip is prepared by a polymer material with good biocompatibility and high chemical stability; therefore, it has the advantages of strong cell constraint ability and good localization stability. The result of chip performance verification shows that the cell localization rate of the functional micro topological chip is up to 90%, and the chip structure and dimension stability are good. The study provides an important supporting tool for the research of stem cells and their differentiation that need long-term cell culture.

Thioetherimide-Modified Cyanate Ester Resin with Better Molding Performance for Glass Fiber Reinforced Composites

Cyanate ester (CE) resins with higher heat resistance, lower coefficients of thermal expansion (CTEs), and lower water absorption ratios are highly desired in printed circuit boards (PCBs). In this work, a CE was modified by copolymerization with a long-chain thioether bismaleimide (SBMI) to form a thioetherimide-modified CE (SBT). The results indicated that SBT had a wider processing window and better processing properties than a common bismaleimide-modified CE resin (MBMI). After molding with a glass fiber cloth, the composites (GSBT) exhibited moisture adsorption in the range of 1.4%–2.0%, high tensile strength in the range of 311–439 MPa, good mechanical retention of 70%–85% even at 200 °C, and good dimension stability, with coefficients of thermal expansion in the range of 17.3–18.6 (×10−6 m/°C). Such GSBT composites with superior properties would be good candidates for PCB applications.