Utjecaj TiO2 na antibakterijska svojstva biorazgradljivih kompozita LDPE/rižine ljuskice

For many years, various synthetic polymers such as polystyrene (PS), polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) have been used as packaging materials for food and other products. In general, less than 5 % of all plastic materials are recycled, which resulted in many ecological problems. After the use, synthetic polymers take a long time to break down into basic components. That is why their disposal has had a negative impact on environmental pollution and climate change. In order to reduce the amount of synthetic plastic waste that is sent to landfills every day, as well as the dependence on petroleum products, there has been an increasing interest in the production of biodegradable and renewable materials over the past few years. Biodegradable materials are associated with the use of renewable raw materials. Low density polyethylene (LDPE) is one of the most commonly used synthetic polymer in the production of foils and other packaging materials. Rice husk (RH) is an inexpensive by-product of rice processing. It is separated from rice grain during the milling process. Biodegradable composites made from an LDPE polymeric matrix and reinforced with rice husks have the potential to completely replace synthetic packaging products. To ensure the quality and safety of the product, an antimicrobial agent should be added to these composites in order to inhibit the growth of bacteria and therefore preserve the product. The aim of this thesis was to determine whether TiO2, as an antimicrobial agent, has antibacterial properties. The tests included its reaction to Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis. Two types of experiments were carried out. The first one served to examine how different mass fractions of TiO2 (2, 3 and 5 wt %), in liquid and solid states, affect the inhibition of bacteria; as well as the effect of TiO2 added into the composite of LDPE and RH. TiO2 in liquid state showed no antibacterial properties, while in solid state it inhibited the growth of the investigated bacteria. According to the results, with the addition of higher content of TiO2 (0.5 %, 1.0 %, 1.5 % and 2.0 wt %) into LDPE/ RH 60/40 bio-composites, the number of bacterial culture cells decreases. In conclusion, TiO2 inhibits the growth of bacterial cultures of Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis.