Reološke in časovno odvisne mehanske lastnosti polimerno-lesnih kompozitov z visokim deležem lesne moke

Privšek, Petra (author), Slemenik Perše, Lidija (mentor)

Znano je, da so polimeri v sedanjem času eni izmed najbolj uporabljenih materialov, saj se njihova uporaba iz dneva v dan povečuje. Posledično izrazito narašča tudi količina polimernih odpadkov, ti pa zaradi počasnega razgrajevanja pogosto obremenjujejo okolje, zato je potrebno njihov negativni vpliv na okolje odpraviti ali zmanjšati. Ena izmed možnih rešitev je izdelava polimerno-lesnih kompozitov z visokim deležem lesne moke. Njihova uporaba se je v zadnjih letih povečala, saj imajo v primerjavi s čistimi polimeri nižjo ceno, nižjo specifično težo, nižjo toplotno prevodnost, višjo upogibno trdnost in so ekološko bolj sprejemljivi. Pri izdelavi kompozita lahko z uporabo recikliranega polimernega veziva še dodatno zmanjšamo negativen vpliv na okolje. Trenutno najbolj uporabljena vrsta recikliranja je mehansko recikliranje, pri katerem material mehansko zdrobimo, nato pa ga obdelamo z različnimi metodami obdelave. Najbolj pogosta metoda obdelave materiala je ekstrudiranje, pri kateri lahko pride do sprememb v reoloških, termičnih in časovno odvisnih lastnostih materiala. Cilj naloge je bil ugotoviti, kako delež lesne moke in recikliranje polimera vplivata na reološke, termične in časovno odvisne mehanske lastnosti polimerno-lesnih kompozitov. Za polimerno vezivo je bil izbran surovi in recikliran polipropilen. Reološke in časovno odvisne mehanske lastnosti so bile določene s pomočjo rotacijskega reometra, termične lastnosti pa z diferenčno dinamično kalorimetrijo (DSC). Rezultati so pokazali, da se reološke, termične in časovno odvisne mehanske lastnosti polimerno-lesnih kompozitov spreminjajo tako z naraščanjem deleža lesne moke kot z recikliranjem polipropilenskega veziva. Dodatek lesnih delcev polimerni matrici spremeni omenjene lastnosti, ker delci ovirajo gibanje polimernih verig. Na lastnosti kompozitov je vplival tudi proces recikliranja: Med procesom je namreč prišlo do poškodb polimerne matrice in s tem do razpada oziroma krajšanja polimernih verig, s čimer so se spremenile struktura in posledično lastnosti materiala.

• Language: Slovenian
• Keywords: Polimerno-lesni kompoziti, reološke lastnosti, časovno odvisne mehanske lastnosti, recikiranje, polipropilen.
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-124453
• COBISS.SI-ID: 48487171
• Publication date in RUL: 22.01.2021

Secondary language

• Language: English
• Title: Rheological and time-dependent mechanical properties of highly-filled wood polymer composites

Abstract

Polymers are one of the most commonly used materials and their consumption is still increasing every day. Consequently, the amount of polymer waste is also increasing, which has negative impact on the environment due to very slow disintegration process. Therefore, it is essential to reduce the environmental effect of polymers by various means. One of the possible ways is the use of highly filled wood-polymer composites. In addition to lower environmental impact, the use of these composites has increased in recent years also due to their lower price, lower specific weight, lower thermal conductivity and higher tensile strength in comparison to pure polymer materials. The environmental impact of the polymers can be further reduced by using recycled polymers as binder materials for the mentioned composites. Polymers are usually recycled by use of mechanical recycling, during which the material is first physically crushed, and then processed with different treatment methods. The most commonly used processing method is extrusion, during which the rheological, thermal and time-dependent mechanical properties of the material usually change. The aim of this thesis was to determine the effects of different concentration of wood particles and recycled polymer binder on rheological, thermal and time-dependent mechanical properties of wood-polymer composites. Raw and recycled polypropylene were chosen as the binder materials. The rheological and time-dependent mechanical properties were measured by Rotational Rheometer, while the thermal properties were determined with Differential Scanning Calorimetry (DSC). The results showed that both, the increasing concentration of wood particles and the recycling of the binder material, have significant effect on the rheological, thermal and time-dependent mechanical properties of highly filled wood-polymer composites. In the prepared composites the wood particles affect the mentioned properties by hindering the movement of polymer chains of polypropylene, while the recycling process results in shortening or disintegration of those chains and consequently changes the structure of the material.

• Keywords: Wood-polymer composites, rheological properties, time-dependent mechanical properties, recycling, polyproylene.