Mehanička svojstva i sadržaj slobodnog formaldehida ploča iverica izrađenih primjenom katalizatora na bazi amonijeva sulfata djelomično zamijenjenoga vinskom kiselinom

The use of resins, whose curing reaction takes place by high temperature and hardener addition, is inevitably involved in particleboard manufacturing process. In addition to commercial hardeners, such as ammonium sulphate, with the aim of optimizing the production process and reducing the production costs, a certain percentage of hardener can, among other things, be replaced with price affordable bio-based materials. Tartaric acid, that is its salts (tartrates), which are commercially produced for the needs of wine and food industries, are a part of the aforementioned group of products. Since tartaric acid is a relatively inexpensive, readily available, weak diprotic and aldaric acid, the question arises whether it can be used as a component of the hardener system for curing urea-formaldehyde resins that are commercially used in particleboard production. For that reason, in this paper, the influence of partial replacement of ammonium sulphate hardener with tartaric acid on the mechanical properties (bending strength, modulus of elasticity and internal bond) and free formaldehyde content of experimentally produced particleboards was examined. Boards thickness, density and moisture content were also determined. The test results suggest that tartaric acid has a beneficial effect on the above particleboard properties, but they also indicate that the extent of that effect is strongly dependent on panel press time.Proces proizvodnje ploča iverica neminovno podrazumijeva upotrebu smola čija se reakcija otvrdnjavanja ostvaruje uz pomoć povišene temperature i katalizatora. Uz komercijalne katalizatore poput amonijeva sulfata, radi optimizacije procesa i racionalizacije troškova proizvodnje ploča, katalizatore je u određenom postotku moguće zamijeniti, među ostalim, i cijenom prihvatljivim proizvodima na biobazi. U navedenu se skupinu proizvoda svrstava i vinska kiselina, točnije njezine soli (tartarati), komercijalno proizvedene za potrebe vinske i prehrambene industrije. S obzirom na to da je vinska kiselina relativno jeftina, lako dostupna, slaba diprotonska, aldarna kiselina, postavlja se pitanje potencijala njezine primjene u sustavima katalizatora za otvrdnjavanje ureaformaldehidne smole koja se upotrebljava u proizvodnji ploča iverica. Upravo je zato u ovom radu ispitano kako se zamjena dijela amonijeva sulfata tartaratnom kiselinom odražava na mehanička svojstva (savojnu čvrstoću, modul elastičnosti, vlačnu čvrstoću) i na koncentraciju slobodnog formaldehida eksperimentalno proizvedenih ploča iverica. Usto, u eksperimentu su određene debljina i gustoća ploča te sadržaj vode u njima. Rezultati ispitivanja upućuju na to da dodatak vinske kiseline povoljno utječe na navedena svojstva ploča, ali i na činjenicu kako taj učinak iznimno ovisi o vremenu prešanja ploča