Investigations of gluing quality of laminated window profiles

Nedostatak kvalitetnoga tehničkog drva kao sirovine za drvnu industriju evidentan je i poznat ne samo na našim, nego i na širim prostorima Evrope i Amerike. U želji da se poveća stupanj iskorištenja drva (kako kvalitativno tako i kvantitativno), razvile su se razne tehnike i tehnologije lijepljenja drva. Lijepljene drvne poluproizvode prepoznajemo na tržištu pod nazivom "engineering wood" i u grubljoj ih klasifikaciji možemo smatrati kompozitnim materijalom. Takav su proizvod i lamelirani elementi za proizvodnju građevne stolarije, a proizvode se dužinskim i debljinskim lijepljenjem drva i mogu uspješno zamijeniti elemente od masivnog drva. Lamelirani elementi imaju i neke prednosti pred elementima od masivnog drva. To su smanjenje deformacija i racionalnija uporaba drva. Za proizvodnju građevne stolarije najčešće se rabe lamelirani elementi izrađeni od tri lamele. Ocjenjivanje kvalitete lameliranog elementa uglavnom se svodi na vizualnu kontrolu, a kvaliteta lijepljenja procjenjuje se certifikatom za kvalitetu ljepila, što nipošto nije dovoljno jer na kvalitetu lijepljenjem dobivenog spoja utječu, osim ljepila i drugi parametri procesa lijepljenja. Za ocjenu kvalitete lijepljenja lameliranih elemenata potrebno je provoditi temeljita ispitivanja čvrstoća lijepljenih spojeva, i to kontinuirano, radi potvrde pravilnog izbora ljepila i režima lijepljenja. Na taj je način opravdana zamjena masivnog drva lameliranim elementima i osigurano jamstvo kvalitete.The issue of lack of high-quality wood as raw material for the timber industry is evident and well known not only in this country but throughout Europe and America. In order to increase the utilisation level of timber as a raw material (both in terms of quantity and quality) and in order to enhance physical and mechanical features of the products’ constructive elements, different techniques and technologies of wood processing have been developed. On the markets these products are known as “engineering wood” and they can be roughly classified as composite materials. Laminated elements belong to the products that substitute massive wood by ways of extension, widening and hardening of wood elements. In this way, reduction of deformation caused by humidity changes in wood such as twisting, winding and bowing can be reached or brought to tolerable levels. Laminated elements made of three laminates are commonly used for production of construction wood. Quality evaluation of laminated elements is usually carried out by visual control and the gluing quality is estimated based on the glue quality certificate. For assessing the gluing quality of laminated elements, the investigation of the strength of glued joints should be conducted on a regular or periodical basis, in order to have the confirmation of the right choice of glue and control of the production regime. In this manner justification and guarantee can be provided for the substitution of massive wood by laminated elements