Currently, wood particle boards made of crushed shavings are widely used in the production of cabinet furniture, despite their shortcomings. The volume of particle board production in Russia is constantly growing. The main disadvantages of the boards include their toxicity associated with the release of gas (formaldehyde) harmful to humans above the permissible level (PL = 0.01 mg/m3 of air), low strength properties (especially bending strength) and limited areas of application of the boards. If we trace the dynamics of the technical requirements for these properties of boards according to the standards, then the question arises - what is the reason for the decrease in the requirements for the strength of boards in bending and, in this regard, the limitation of the application areas of particle board? A regular decrease in the requirements in the newly introduced State Standards has been constantly occurring since 1977, but this is especially noticeable in the current 10632-2014 State Standard. This article focuses on the possible objective and subjective reasons for the low requirements of the current standard for the strength of wood particle board.
By production of glued and plate wood-base materials with use of carboamidoformaldehyde pitches (KFS) the main lack of technology of which is toxicity of these materials to the person. Toxicity is caused by allocation from these materials of gas, harmful to the person, - formaldehyde which is cancerogenic substance. Wood-shaving plates from needle (DSTP) and large-size shaving (OSB), fiber boards (DVP) including the Intermediate-density fiberboard (MDF), and also plywood of general purpose and different types of special plywood (decorative, bakelized, etc.), first of all, belong to such materials. The Russian Ministry of Health has established very strict requirements on release of formaldehyde in air both in premises, and in free air the admissible level of which makes (DU) only 0,01 mg/m3 of air when testing materials by chamber method. The plate materials released now can exceed DU of 17 times stated above. Especially it concerns DSTP. Despite attempts of institute Vniidrev through appeals to relevant authorities of the Ministry of Health to increase such admissible level in our country, generally for plate materials, were not crowned with success yet and this level in real time remains in force. It is possible to use such plates in premises only at very small saturation them room void volume (the saturation is defined as the relation of surface area of plates indoors to room void volume). So, by our researches for example it is proved that the written dvukhtumbovy table made of DSTP of class of release of formaldehyde E2 can be established in living room of 20 sq.m only one and no more. Only in this case, at small saturation room void volume plates, the release of formaldehyde in air of the room will meet requirements of domestic DU. In premises the case furniture is in reality with much bigger saturation that leads to room gas contamination formaldehyde. In too time abroad formaldehyde size DU in air much more also makes 0,124 mg/m3 of air. In this regard the purpose of our work consisted in the analysis of DU of formaldehyde in air of foreign researches.
Since the glue is not an ideal liquid for which the laws of its expiration are generally known, the purpose of our work was to determine the duration and speed of the resin outflow from the container, depending on 2 factors - the height of the container with the resin above the surface on which the resin is applied, and the conditional viscosity of the resin within its working value. As a result of the conducted research, it was found that it is possible to dose the glue in the glued beam technology, when using low-viscosity resins, by lifting the container with the resin (glue) above the level of the surface on which it is applied. Moreover, for low viscosity fluids with a viscosity up to 80 °C (on the examples of water and resin low viscosity) observed increase in flow rate from the container increasing the height of the rise of liquids over the surface to which it is applied. As the resin viscosity increases from 80 to 131s the absolute value of the resin flow rate from the container decreases.
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