Efekti nekih predtretmana na hemijski sastav juvenilnog i zrelog drveta poljskog jasena (Fraxinus angustifolia Vahl. ssp. Pannonica Soó & Simon) i mogućnosti primene tako modifikovanog drveta

Abstract

U oviru ove doktorske disertacije istražena je varijabilnost anatomskog i hemijskog sastava u zavisnosti od starosti i položaja na stablu, i uticaj hemijskih predtretmana na hemijski sastav juvenilnog (10 godina) i zrelog (72 godine) drveta poljskog jasena (Fraxinus angustifolia Vahl. ssp. Pannonica Soó & Simon) sa područja Morovića. U cilju ispitivanja dejstva predtretmana juvenilno i zrelo drvo poljskog jasena tretirano je 1 h na temperaturi od 100 oC vodom, i pri dodatku rastvora 0,06 g/g sirćetne kiseline i 0,03 g/g natrijum karbonata. Za anatomsku karakterizaciju primenjene su svetlosna i elektronska mikroskopija (SEM). TAPPI i ASTM metodama određen je sadržaj celuloze, Klasonovog i kiselorastvornog lignina, mineralnih materija i ekstraktivnih jedinjenja rastvorljivih u vreloj vodi i u smeši organskih rastvarača (toluol/etanol). Za utvrđivanje sadržaja glukoze, ksiloze i manoze u uzorcima drveta i ekstraktima iz tretmana primenjena je visoko efikasna tečna hromatografija (HPLC), a za analizu funkcionalnih grupa primenjena je infracrvena spektroskopija (FTIR). Elementarna analiza karakterističnih detalja uočenih u tkivu poljskog jasena obavljena je primenom SEM-EDS sistema. Primenom standardnih EN SRPS i DIN, kao i naučnih metoda ispitan je uticaj tretmana na sadržaj ravnotežne vlage, adhezivna svojstva, upijanje vode, zapreminsko bubrenje i toplotnu moć drveta poljskog jasena. U cilju istraživanja mogućnosti primene tretmanom modifikovanog drveta izrađene su eksperimentalne jednoslojne ploče iverice. EN SRPS standardi su primenjeni za ispitivanje fizičkih i mehaničkih svojstava izrađenih ploča. Ustanovljeno je da postoji varijabilnost dimenzija elemenata anatomske građe i hemijskog sastava poljskog jasena u zavisnosti od starosti i položaja na stablu. Svi tretmani su doveli do promena u hemijskom sastavu drveta, i to u većoj meri kod juvenilnog drveta. Tretman vodom izazvao najmanje promene, a tretman natrijum karbonatom najveće. U tretiranom drvetu poljskog jasena smanjen je sadržaj mineralnih materija za 16 - 80 %, ekstraktivnih materija rastvorljivih u vreloj vodi za 76 - 85 %, a sadržaj ekstraktivnih materija rastvorljivih u smeši toluol/etanol za 58 – 78 %. Sadržaj celuloze tretiranog drveta povećan je 3.6 - 8 %, a sadržaj lignina nije značajno promenjen. Sadržaja ksiloze povećan je posle tretmana vodom za oko 3.5 % kod zrelog i 9 % kod juvenilnog drveta, a smanjen posle ostalih tretmana. Tretman vodom i sirćetnom kiselinom doveli su do smanjenja, a tretman natrijum karbonatom do povećanja sadržaja ravnotežne vlage tretiranih uzoraka (90 %, 20 oC). Svi tretmani doveli su do intenzivnijeg upijanja vode i poboljšanja dimenzionalne stabilnosti za 14 - 24.6 %. Adhezivna svojstva značajno su poboljšana posle tretmana natrijum karbonatom. Ploče izrađene od tretiranog iverja imale su niže vrednosti sadržaja ravnotežne vlage u odnosu na kontrolne ploče (32, 65 i 90 %, 20 oC), uz pad mehaničkih svojstava. Dimenzionalna stabilnost ploča od iverja tretiranog vodom poboljšana je za 6.4 %, uz povećanje modula elastičnisti pri savijanju za 35 %. Savojna čvrstoća ovih ploča neznatno je povećena, a čvrstoća na zatezanje upravno na površinu višestruko smanjena.

The scope of this doctoral dissertation included the research on chemical and anatomical variability affected by the age and the position in the tree trunk, as well as the influence of the chemical pre-treatments on the chemical composition of juvenile and mature wood of Narrow-leaved ash (Fraxinus angustifolia Vahl. ssp. Pannonica Soó & Simon) sampled from the Morovic area. In order to evaluate the pre-treatment effects, both juvenile and mature ash wood samples were treated with distilled water and with the solutions of acetic acid (0,06 g/g) and sodium hydroxide (0,03 g/g), during 1 h on the temperature 100 oC. The light and the scanning electronmicroscopy (SEM) were applied for the anatomical characterization of ash wood. The TAPPI and ASTM methods were used to determine the contents of cellulose, Klason and acid soluble lignin, mineral substances and the extractive compounds soluble in hot water and in the mixture of organic solvents (toluene/ethanol).The contents of glucose, xylose and mannose were determined with the application of high-performance liquid chromatography (HPLC), while the Fourier transform infrared spectroscopy (FTIR) was used to analyze functional groups. SEM-EDS system was applied for the elements analysis of characteristic details observed in the wood tissue of Narrow-leaved ash. The EN SRPS and DIN standard methods and the scientific methods were used to evaluate the effects of the treatments on the equilibrium moisture content, adhesive properties, water uptake, volumetric swelling and heating value of ash wood. The single layer laboratory scaled particleboards were produced in order to evaluate the application possibilities of the ash wood modified with selected pretreatments. EN SRPS standard methods were used to test the physical and mechanical properties of produced boards. It was found that the age and the position inside the trunk affect the dimensions variability of the anatomical elements and the chemical composition of Narrow-leaved ash. All the applied treatments had caused the changes in the chemical composition of wood. The juvenile wood experienced the more intensive changes than the mature wood. The water treatment had caused the least intense changes, while the highest changes in wood were characteristic for the sodium hydroxide treatment. As a result of the treatments, the mineral content in ash wood decreased for 16 - 80 %, the extractives soluble in water decreased for 76 - 85 % and the extractives soluble in the toluene/ethanol mixture decreased for 58 – 78 %. The cellulose content in ash wood increased for 3.6 - 8 % after the treatments, while the lignin content has not been significantly changed. Xylose content increased after the water treatment for about 3.5 % in mature wood and 9 % in juvenile wood, but have decreased after the other treatments. The equilibrium moisture content (90 %, 20 oC) have been decreased after the treatments with water and acetic acid, but have increased after the sodium hydroxide treatment. All the treatments have brought to more intensive water uptake, but have also improved the dimensional stability for 14 - 24.6 %. Adhesion properties have significantly increased after the sodium hydroxide treatment. Particleboard samples made with treated wood had lower values of equilibrium moisture content in regard to the control samples (32, 65 i 90 %, 20 oC), but also the lower mechanical properties. Dimensional stability of the samples made with water treated particles was improved for 6.4 % followed with the increase in the module of elasticity for 35 %. The bending strength of the same samples increased negligible, but the internal bond experienced multifold decrease.