Influence of selected storage temperatures on wood properties and its biological resistance after the use of methylxanthines

Abstract

Methylxanthine’s fungicidal properties were investigated, with attention to the temperature of treatment. Caffeine and theophylline treatments of beech and spruce woods were applied for three months in the temperature range of -20 to 40 °C, simulating potential weather conditions in the European region and temperatures specific for various wood applications (cellars, wine cellars, room indoor temperatures, interior trusses). Effects of the selected temperatures were considered without the influence of the other possible factors, which have been considered in previous studies (e.g. effects of temperature in combination with other factors such as UV radiation, humidity, and chemical or biological degradation). Then, the specimens were exposed to a mix of molds and fungi for three months under controlled laboratory conditions in order to analyze a possible subsequent biological attack. The results did not show any effect of temperature of the methylxanthine treatment within the studied range on the organismal activity. Caffeine exhibited a better protective potential than theophylline and was more effective for spruce than for beech. The results indicated the suitability of caffeine for protection of spruce and spruce-based materials in interior applications at a stable temperature without significant effects of UV and humidity.

Efficacy of Caffeine Treatment for Wood Protection—Influence of Wood and Fungi Species

“…One method is to use substances of natural origin that have been shown not to accumulate [4,5], and caffeine is also a very affordable alternative. Its biocidal effect has been explained in several works [6][7][8]. The insecticidal effect is explained by the inhibition of phosphodiesterase activity leading to an increase in intracellular cyclic adenosine monophosphate [9].…”

“…Lightly permeable types of pine and beech wood and the method of vacuum impregnation [7,11,12] were used in most cases, but efficiency on hard-to-permeate spruce wood was also verified using long-term dipping technology [13]. Caffeine was effective against the growth of wood-destroying white and brown rot fungi [6][7][8]10,12,14] and was also tested on wooden specimens for mould growth [15]. So far, a 2% caffeine solution was tested as an effective concentration, whereas tests using lower concentrations that would reduce the cost of the used protection [1,16] are lacking.…”

“…So far, a 2% caffeine solution was tested as an effective concentration, whereas tests using lower concentrations that would reduce the cost of the used protection [1,16] are lacking. The weakness of caffeine as a natural biocide for wood protection is its washability by water [13], in which, according to research works [8,17], it only forms weak bonds. The increase in the biocidal efficiency of caffeine was investigated using subsequent heat treatment [15] and the water washability was reduced using hydrophobic treatments [12,13].…”

“…The influence of the species of treated wood (beech and spruce) on the efficiency of caffeine has thus far been investigated in only one work [8]; otherwise, only one kind [7,[11][12][13]15] was always used. However, the specific species of treated wood may have an impact on the effectiveness of the protective substance [19][20][21].…”

“…However, the specific species of treated wood may have an impact on the effectiveness of the protective substance [19][20][21]. This concerns not only the quality of the impregnation [19,22], as a synergistically positive or negative effect is also possible in combination with the extractives contained in the wood, which cause its natural durability against bio-attack [8,20].…”