1. Microplastic pollution in vulnerable karst environments : case study from the Slovenian classical karst regionLara Valentić, Peter Kozel, Tanja Pipan, 2022, izvirni znanstveni članek Opis: Since the start of mass production of plastic materials more than a century ago, the problem of accumulating plastic waste in the environment has reached epic proportions. Recently, the problem of smaller plastic particles (microplastic, MP) in the environment has become a widely studied topic, but the amount and types of MP in karst environments are still poorly known. Thus, the objective of this study was to collect and analyse samples from various karst habitats and to try and determine the scope of pollution in karst springs that are in part used as sources for drinking water. Of the potential pollution sources, we sampled rainwater, two discharges from wastewater treatment plants, and a leachate from a landfill. We conducted polymer analyses of potential MP particles using FTIR-ATR. The results showed that eight samples from the Postojna region (Postojna–Planina Cave System, rainfall sample and surface streams) contain up to 444 MP particles per m3. However, 32 samples taken from the Škocjan–Kačna–Jama 1 v Kanjaducah Cave System contain up to 60,000 MP particles per m3, with the bulk of particles found in the sediment samples from Škocjan Caves – Kačna Cave System. Samples from Postojna region contained mostly PET, PU and PA polymers, with a minor inclusion of polymers of plastic sponge used for cleaning. Samples from Škocjan region contained mostly PP, PET and PE polymers, with some of PA and PU polymers. Sediment samples contained much less MP particles compared to water samples, which indicates fast transport through karst aquifer.
Ključne besede: caves, fibres, microplastic contamination, karst (geology), groundwater, pollution, plastics, aquifers, Postojna (Slovenia), Škocjan (Slovenia)
Objavljeno v DKUM: 12.07.2024; Ogledov: 122; Prenosov: 13
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2. Comparative study of hydrothermal decomposition of virgin and recycled polypropyleneMihael Irgolič, Maja Čolnik, Petra Kotnik, Lidija Čuček, Mojca Škerget, 2023, izvirni znanstveni članek Opis: Plastics are widely used due to their versatile properties and numerous applications. However, the proper management of plastic waste is a major challenge, even though it is recyclable. The process of repeated recycling can cause the quality of the material to decrease as unwanted contaminants and pollutants increase. This can affect the chemical recycling of plastics at the end of their life and the recovery of secondary products that can be used in other applications. In this study, the chemical degradation of virgin polypropylene (vPP) and recycled polypropylene (rPP) was investigated in supercritical water at a temperature of 450 °C and a reaction time of 15 to 240 min. The oil phase was the primary decomposition product and was obtained in high yield, which reached a maximum after 30 min of reaction time and was 96.9 % for vPP and 94.5 % for rPP. The results of our study show that there are some differences in the product composition depending on which material (vPP or rPP) is chemically recycled.
Ključne besede: virgin polypropylene, plastics, chemical degradation, chemical recycled
Objavljeno v DKUM: 18.04.2024; Ogledov: 235; Prenosov: 6
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3. Chemical recycling of polyolefins waste materials using supercritical waterMaja Čolnik, Petra Kotnik, Željko Knez, Mojca Škerget, 2022, izvirni znanstveni članek Opis: In the following work, the hydrothermal degradation of polypropylene waste (PP) using supercritical water (SCW) has been studied. The procedure was carried out in a high-pressure, high-temperature batch reactor at 425 °C and 450 °C from 15 to 240 min. The results show a high yield of the oil (up to 95%) and gas (up to 20%) phases. The gained oil phase was composed of alkanes, alkenes, cycloalkanes, aromatic hydrocarbons, and alcohols. Alkanes and alcohols predominated at 425 °C and shorter reaction times, while the content of aromatic hydrocarbons sharply increased at higher temperatures and times. The higher heating values (HHVs) of oil phases were in the range of liquid fuel (diesel, gasoline, crude and fuel oil), and they were between 48 and 42 MJ/kg. The gas phase contained light hydrocarbons (C1–C6), where propane was the most represented component. The results for PP degradation obtained in the present work were compared to the results of SCW degradation of colored PE waste, and the potential degradation mechanism of polyolefins waste in SCW is proposed. The results allowed to conclude that SCW processing technology represents a promising and eco-friendly tool for the liquefaction of polyolefin (PE and PP) waste into oil with a high conversion rate.
Ključne besede: polypropylene, polyolefins, supercritical water, plastics waste, chemical recycling
Objavljeno v DKUM: 18.09.2023; Ogledov: 555; Prenosov: 33
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4. The influence of thermoplastic elastomers on morphological and mechanical properties of PP/talc compositesMatjaž Denac, Vojko Musil, 1999, izvirni znanstveni članek Opis: Recent investigations have shown that modification of polymer matrix with filler and elastomers significantly affects composite's mechanical properties. Isotactic PP modified with either untreated or treated talc and either SEBS or SEBS-gMA were used in these investigations. Samples were prepared by melt-mixing in a Brabender kneading chamber and were compression molded into plates on a laboratory press. The composites were characterised by measuring mechanical properties (Young's modulus, yield stress, notched impact strength) and by defining morphology. Binary sistems PP/talc and PP/elastomer containing up to 16 vol.% of talc and up to 10 vol.% of elastomer, as well as ternary PP/talc/elastomer composites with 12 vol.% talc were investigated. Ternary composite's yield stress was also calculated by semiempirical equations. We have found out, that the use of treated modifiers (talc or elastomer) improves adhesion with matrix, which reflects on mechanical properties as better stress transfer.
Ključne besede: organic chemistry, polymers, thermoplastics, composites, characterization, chemistry, plastics, elastomers, morphology, mechanical properties
Objavljeno v DKUM: 10.07.2015; Ogledov: 2549; Prenosov: 91
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5. Intelligent support to specific design aspectsUrška Sancin, Jasmin Kaljun, Bojan Dolšak, 2008, izvirni znanstveni članek Opis: Due to increased rivalry on the market, some specific design aspects like the use of modern plastics materials, ergonomics and aesthetics are becoming more important and are not kept in the background any more in correlation with functionality and economic aspect of the product. Design engineer faces many dilemmas while designing new products as a single person is not able to possess a wide spectrum of knowledge needed for optimal design solutions. At this point designer have to rely on his or her experience and on the knowledge of the expert team involved in the project. The fundamental purpose of the research presented in this paper is to make the product development process less experience dependent. The main goal of thematically oriented research is to develop intelligent advisory system with integrated modules forsome specific design aspects.
Ključne besede: product development, ergonomics, aesthetics, plastics, knowledge based engineering, intelligent systems
Objavljeno v DKUM: 31.05.2012; Ogledov: 1955; Prenosov: 35
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