Browsing by Author "Antwi-Boasiako, C."

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    Effect of Solvent Type on Tannin Extractability from Three Tetrapleura Tetraptera (Schum. & Thonn.) Taubert Positions for Wood Composite Adhesive Formulation
    (Journal of Emerging Trends in Engineering and Applied Sciences, 2012) Antwi-Boasiako, C.; Animapauh, S. O.
    Raw materials for adhesive production are conventionally from expensive petrochemicals, which affect synthetic resins relative to total costs of glued products. Phenol replacement with tannins (i.e., plant polyphenols) in Phenol-Formaldehyde resins is imperative since tannin adhesives are equally resistant to moisture and microbial degradation. Tannin was extracted from Tetrapleura tetraptera (i.e., bark, leaf and fruit) using distilled water and 1% NaOH through Soxhlet extraction. Tannin presence, Extract yield and polyphenol/tannin content (i.e., Stiasny numbers) were respectively determined from qualitative and quantitative analyses. The solvent type and plant part influenced the yield and tannin content. All the three parts, especially the bark, contained tannin. Extract yield was greater in 1% NaOH (39.54% [from leaf] to 77.05% [from fruit]) than in distilled water (12.96% [from fruit] to 18.16% [from leaf]). Conversely, Stiansy numbers for tannin, at all plant parts, were greater for the water-soluble extracts (i.e., 67.50, 68.96 and 87.50% from the leaf, fruit and bark respectively) than in 1% NaOH (i.e., 33.72, 21.94 and 37.42% correspondingly). The large extract yields (i.e., 39.54 - 77.05% for 1% NaOH) and high Stiasny numbers particularly for the water-soluble extracts (e.g. 87.50% for the bark) demonstrate the potential of T. tetraptera extracts as agents for tanning and adhesive formulation for leather, wood and related industries.
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    The effect of stake dimension on the field performance of two hardwoods with different durability classes
    (International Biodeterioration & Biodegradation, 2010-04-22) Antwi-Boasiako, C.; Allotey, A.
    Timber diversity is associated with virtually all types of wood structures for various end-uses including bridges and railway-sleepers. Some timbers resist bio-degradation and are termed naturally durable. Wood durability is influenced by numerous extrinsic and intrinsic factors; however, knowledge is scant about the role stake dimension plays. Therefore, the field performance of replicates of four dimensions (500 50 25; 250 25 12.5; 125 12.5 6.25; and 62.5 6.25 3.13 mm) from two commercially important hardwoods (Milicia excelsa and Sterculia rhinopetala) of different durabilities (i.e., high and moderate, respectively) was investigated for 5 years using the graveyard method with non-durable Ceiba pentandra as a control. Durability parameters assessed were visual durability ratings, hardness, and mass losses. C. pentandra usually performed worst in all parameters. Generally, a steady increase exists in degradation from the thickest stakes (500 50 25 mm) to the thinnest (62.5 6.25 3.13 mm). Thus, the greater the stake dimension, the smaller its visual durability rating, mass and hardness losses (i.e. more durable). However, few discrepancies occurred, as the thinnest stakes were often buried deep in the soil, decreasing their chances of getting attacked. M. excelsa remained harder and more durable for stakes of all dimensions (especially the thickest) than those of S. rhinopetala. However, the thinnest M. excelsa stakes unexpectedly recorded mean mass loss of 4.9%, compared with 2.1% for S. rhinopetala. The study shows wood dimension significantly affects its durability, which would inform timber engineers about their wood dimension choices for appropriate end-uses.
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    Investigation of synergistic effects of extracts from Erythrophleum suaveolens, Azadirachta indica, and Chromolaena odorata on the durability of Antiaris toxicaria
    (International Biodeterioration & Biodegradation, 2010-01-29) Antwi-Boasiako, C.; Damoah, A.
    The service life of non-durable wood can be extended with inorganic preservatives, but several are harmful to the environment and non-target organisms. Recently, eco-friendly types from organic sources including plants have been used. The influence of bark extracts from Erythrophleum suaveolens and Azadirachta indica, and leaf extract from Chromolaena odorata, singly and in combinations (all at 1.5%) was investigated in field performance tests with non-durable Antiaris toxicaria wood. Treated and control stakes (500 50 25 mm) were exposed for 5 years. Data included extract retention, visual durability ratings, and mass and hardness losses. Retention was greatest for mixed E. suaveolens and C. odorata extract and least for single E. suaveolens extract. For durability parameters, non-treated stakes performed worse than treated ones. E. suaveolens bark-treated stakes were most durable; those treated with mixtures containing E. suaveolens also performed well, while stakes treated with other mixtures performed similarly to the controls, except for hardness. The mixed extracts exhibited various effects. For retention, synergism exists between E. suaveolens and C. odorata, there was antagonism between A. indica and C. odorata, while E. suaveolens extract reduced the retention of A. indica. Regarding durability, no synergism existed between effects of the mixed components. However, E. suaveolens bark extract enhanced A. indica, and C. odorata ingredients, while the effect of E. suaveolens extract was suppressed when it was mixed with the others. These extracts are potential alternatives for inorganic preservatives, especially E. suaveolens and its mixed extracts, as its effects enhanced the others.
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    Studies on some aspects of the biology of Cercospora Henningsii Allesch in relation to the Epidemiology of Brown Leap Spot Disease of Cassava (Manihot Esculenta Crantz.) and Tree Cassava (Manihot Glaziovii Muell.-Arg.)
    (1991) Antwi-Boasiako, C.
    Cercospora henningsii Allesch, causal agent of brown leaf spot of cassava (Manihot esculenta Crantz) and tree cassava (Manihot glaziovii Muell. -Arg.), produces two types of spores named as the macro-conidia and the micro-conidia. (As the names suggest, the former are bigger in size (20 - 120 x 5 - 7.5 μm) and the latter are smaller (8.75 - 17.5 x 3.75 - 7.5 μm). Isolates from each of the varieties of cassava and tree cassava could not be differentiated on the basis of the shapes of their spores. There was, however, a slight variation between the sizes of each type- of spore from the test plants as statistical analysis showed. The micro-conidia were observed to have been formed from the macro- conidia through budding and fragmentation. The frequency of occurrence of each type of spore depended on the time of the year (that is, the season) during which lesions were taken for studies. More micro-conidia were harvested from lesions of each test plant during the wet periods of the year. However, during the dry harmattan periods, fewer numbers of spores were harvested of which the macro—conidia were more frequent. Sporulation of the fungus is sensitive to disinfectants (for - example, mercuric chloride - alcohol solution which was used to sterilize the lesions reduced sporulation). The longer the lesions were exposed to the disinfectant, the fewer the number of spores harvested; macro-conidia were found to be more frequent after lesions have been kept in mercuric chloride - alcohol solution for long periods of time. The micro-conidia became more frequent as the incubation periods on lesions became longer. Successive crops of spores, more frequently the micro-conidia, could be harvested from lesions when they were washed and reincubated for successive periods of time. The lesions, therefore, have a high sporulating potential. Lesions sporulated from 40-100% relative humidity but sporulation was best at 95% and 100% humidity and poorest at 40% and 60% humidity. Latent period of germination for micro-conidia was 4-6 hours and 5-7 hours for the macro-conidia. Diverse forms of appressoria were formed at the apices of germ tubes of the micro-conidia whilst those of macro-conidia had fewer but simple Knob-like forms of appressoria. Germinated spores of each type could produce as many as three germ tubes. Long germ tubes were produced from germinated spores of each type and some of them were as long as 90Ojm when the spores were incubated at 100% humidity for 24 hours. Germination was better on host leaf surfaces than on glass surfaces. Branching of germ tubes could also be stimulated better on host leaf surfaces than on glass surfaces. Conidia germinated from 80-100% humidity. It was, however, best at 100% humidity and percentage germination was better for micro-conidia than for macro- conidia at this level of humidity. Germination of conidia of isolates from cassava and tree cassava was similar. Incubation period on cassava varieties during self-inoculation studies was shorter (12.6 days) whilst that on tree cassava was longer (22.6 days) when leaf-borne conidia of high spore density were used for inoculation through the contact method. Incubation periods were also shorter when abaxial or lower surfaces of red and white varieties of cassava were inoculated using inocula with higher densities. In much the same way, the number of inoculated spots which got infected depended Ofl the concentration of inocula, the variety of host plant and the leaf surface inoculated. More inoculated spots on the varieties of cassava got infected than on tree cassava. During cross-inoculation tests, inocula from cassava could infect tree cassava. Similarly, isolates from tree cassava could infect both varieties of cassava. Tree cassava is a possible source of inoculum for cassava.
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    Swelling characteristics of conventional and organic preservative-treated porous tropical utility hardwood [ceiba pentandra (l.) gaertn.]
    (Special Topics & Reviews in Porous Media — An International Journal, 2013) Antwi-Boasiako, C.; Boadu, Kwadwo Boakye
    Overexploitation of endangered timbers necessitates utilization of chemically treated nondurable species. Ceiba pentandra is porous, dimensionally stable in dry service conditions, and has regular export of treated products. Swelling characteristics of treated woods are hardly studied. This work provides a scientific bridge to this gap. Influence of Maneb/Lambda mixture and Erythrophleum suaveolens bark extract on the swelling of C. pentandra was investigated by water immersion for 24 h. Directional swelling was greatest tangentially (1.4–2.5 times greater than radial swelling) and least along longitudinal directions (90–360 times less than tangential surfaces) depending on solvent type. Untreated stakes soaked in the three solvents swelled more than treated stakes in water. Tangential swelling was greater for untreated stakes in E. suaveolens (9.20 § 0.02%) and Maneb/Lambda (9.32 § 0.02%) than in water (8.10 § 0.01%); the contrary occurred for longitudinal and radial swellings. Maneb/Lambda-treated stakes swelled more tangentially in water (7.36 § 0.13%) but less at radial directions (2.89 § 0.01%) than those treated with E. suaveolens (7.10 § 0.00% and 3.28 § 0.02%, respectively). Volumetric swelling was greater for untreated stakes in all solvents (12.66 § 0.60% in water/14.74 § 0.66% in Maneb/Lambda) than for Maneb/Lambda- and E. suaveolens-treated stakes in water (10.51 § 0.14% and 10.62 § 0.02% respectively). Thus, preservative-chemicals would protect nondurable timbers against biodeterioration with the added advantage of reducing moisture-absorption capacity of engineered products in service conditions.
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    Thermal conductivity, resistance and specific heat capacity of chemically-treated, widely-used timber for building-envelope
    (High Temperatures-High Pressures, 2018) Antwi-Boasiako, C.; Boadu, Boakye K.
    Wood has low thermal conductivity with high thermal resistance and specific heat capacity (SHC). Timber-designed building-envelopes have much resistance to solar radiation, which discomforts occupants. How chemicals alter thermal properties of preservative-treated non-durable woods for housing is inadequately studied. Two preservative-chemicals (Erythropleum suaveolens bark extract and inorganic Maneb/Lambda) influence on the SHC (determined by “method of mixtures”) and, thermal conductivity and resistance (using Lee’s Disc Apparatus) of Ceiba pentandra (a non-durable building timber) was investigated. Stakes treated with E. suaveolens and Maneb/Lambda recorded greater conductivity [(0.005 ±  0.001) × 10-³ and (0.006 ± 0.0006) × 10-³ W/m.K respectively] than C. pentandra control [(0.004 ± 0.0008) × 10-³ W/m.K]. Conductivity was greater in longitudinal surface than radial and tangential directions for all stakes. Thermal resistance of stakes rated as: control [(0.12 ± 0.0008) × 102 – (1.02 ± 0.02) × 102 m2K/W] > E. suaveolens [(0.1 ± 0.002) × 102 – (0.76 ± 0.02) × 102 m2K/W] > Maneb/Lambda [(0.1 ± 0.002) × 102 – (0.73 ± 0.02) × 102 m2K/W]. Maneb/Lambda-treated stakes obtained the greatest SHC [(6810.9 ±  12) × 106 ], then E. suaveolens-treated samples [(5242.1 ± 269.9) × 106 ] and untreated/control [(4014.2 ± 47.8) × 106 ]. Compared to other building materials (e.g., steel, aluminium and concrete), treated stakes have low thermal conductivity, with high thermal resistance and SHC, which is desired as an insulation material. Thus, while chemically-treated timber durability is improved, its insulating capacity to provide thermal comfort in buildings is assured.