Structuring of composite materials based on poly(lactide) and carbon nanotubes

U ovom radu, izvršena je sinteza i karakterizacija bionanokompozitnih materijala na osnovu poli(laktida) i višeslojnih ugljeničnih nanocevi. Ispitivan je uticaj različitih tehnika funkcionalizacije nanocevi, kao i izbor uslova sinteze i odnosa polaznih komponenti sistema, na svojstva dobijenih kompozitnih materijala na osnovu poli(L-laktida). Radi postizanja uniformne raspodele nanopunila u kompozitima, višeslojne ugljenične nanocevi su modifikovane hemijskom i radijacionom funkcionalizacijom. Izvršena je karakterizacija ugljeničnih nanocevi, sa ciljem utvrđivanja uspešnosti primenjenih tehnika modifikacije na njihova svojstva i stepen funkcionalizacije. Metodom in situ polimerizacije L-laktida sa površina modifikovanih nanocevi, pripremljene su serije uzoraka kompozitnih materijala sa različitim sadrţajem funkcionalizovanih nanocevi. Detaljno je ispitan uticaj funkcionalizovanih nanocevi na toplotna, kristalna, morfološka, mehanička i električna svojstva sintetisanih kompozitnih materijala. Postignuta homogena disperzija nanocevi unutar biorazgradive, biokompatibilne matrice polimera koji se dobija iz obnovljivih sirovina, uticala je na poboljšanje svojstava, kao i na uspostavljanje novih funkcionalnosti dobijenih materijala. Značajno poboljšanje toplotnih i mehaničkih svojstva sintetisanih materijala, zajedno sa postignutom električnom provodljivošću, omogućava proširenje oblasti primene kompozita na osnovu poli(laktida) i ugljeničnih nanocevi.In this thesis, bionanocomposites based on poly(lactide) and multi-walled carbon nanotubes were synthesized and characterised. Poly(L-lactide) was used as a matrix for the composite synthesis; the influence of nanofillers content, the methods of their functionalization, as well as the synthesis parameters, on the properties of obtained materials were investigated. In order to achieve a uniform dispersion of nanofillers in composite materials, multi-walled carbon nanotubes were modified using chemical and radiation functionalization. Characterization of carbon nanotubes was performed in order to determine the influence of applied modification techniques on their properties and degree of functionalization. A series of composite materials with different content of modified nanotubes were prepared by in situ polymerization of L-lactide from the surface of functionalized nanotubes. The influence of functionalized nanotubes on the thermal, crystal, morphological, mechanical and electrical properties of synthesized composites was investigated in detail. The homogeneous dispersion of carbon nanotubes within the biodegradable, biocompatible, biobased polymer matrix, has influenced the improvement of the properties, as well as the acquiring of new functionalities of synthesized materials. The significant improvement of thermal and mechanical properties of composites, and the achievement of its electrical conductivity, allow the field of application of composites based on poly(lactide) and carbon nanotubes to be expanded

Characterization of electrospun poly(lactide) composites containing multiwalled carbon nanotubes

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors would like to thank the Ministry of Education, Science and Technological Development, Republic of Serbia, for funding projects III45022 and 172056 and European Cooperation in Science and Technology (COST) action CA15107.The main aim of this work was to obtain conductive polymer-based materials by incorporation of different amounts of multiwalled carbon nanotubes (MWCNTs) into poly(lactide)(PLA) using the electrospinning technique. Fiber-based nonwovens with 0.2, 0.5, 1, and 3 wt% of MWCNTs were characterized regarding conductivity, morphology, thermal, and mechanical properties. It was confirmed that an increase of the MWCNTs content does not influence the increase of the material conductivity, since the conductivity was 170 ohm sq−1 for all composites. Scanning electron microscopy and transmission electron microscopy analyses revealed that smooth and beadless fibers were obtained, but also average diameters of composite nanofibers decreased with the increase of the MWCNTs content. Differential scanning calorimetry analysis showed that the presence of MWCNTs in the PLA matrix had a significant influence on the crystallization behavior of PLA nanofibers, because the decrease in crystallization temperature (Tc) was detected. Also, the incorporation of MWCNTs into PLA fibers affected the melting process, enabling the generation of α′ form, while had no influence on ordered α crystal. The enthalpy of composite degradation decreased, because MWCNTs are well-known for good heat conductivity, and with that the second step of degradation slowed down, as it was confirmed by thermogravimetric analysis. The addition of MWCNTs improved mechanical properties of composite fibers and caused the increase of both elasticity and tensile strengths of nanofibers.Ministry of Education, Science and Technological Development, Republic of Serbia III45022 and 172056; COST CA15107; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Evaluation of antioxidant and cytotoxic properties of phenolic N-acylhydrazones: Structure-activity relationship

Cancer is still a relentless public health issue. Particularly, colorectal cancer is the third most prevalent cancer in men and the second in women. Moreover, cancer development and growth are associated with various cell disorders, such as oxidative stress and inflammation. The quest for efficient therapeutics is a challenging task, especially when it comes to achieving both cytotoxicity and selectivity. Herein, five series of phenolic N-acylhydrazones were synthesized and evaluated for their antioxidant potency, as well as their influence on HCT-116 and MRC-5 cells viability. Among 40 examined analogues, 20 of them expressed antioxidant activity against the DPPH radical. Furthermore, density functional theory was employed to estimate the antioxidant potency of the selected analogues from the thermodynamical aspect, as well as the preferable free-radical scavenging pathway. Cytotoxicity assay exposed enhanced selectivity of a number of analogues toward cancer cells. The structure-activity analysis revealed the impact of the type and position of the functional groups on both cell viability and selectivity toward cancer cells

The influence of different plasticizers on the mechanical properties of active edible bilayer films

In addition to potentially resolving environmental issues that come from plastic and food waste, active biodegradable packaging is being developed to increase the shelf life, quality, and safety of packaged food. In order to overcome the drawbacks of monolayer hydrocolloidbased coating, such as poor mechanical and barrier properties, the design of bilayer hydrocolloidbased coating has been structured using pullulan and gelatin. Sugar alcohols are widely used for the plasticizing of biopolymer-based films. The aim of this work is to investigate the influence of different sugar alcohols – xylitol, mannitol, and glycerol on the mechanical properties of pullulan/gelatin bilayer films. Among investigated plasticizers, glycerol has demonstrated the best plasticizing effect, giving a bilayer film with the value of elongation at break which is 66.5 and 88.4% greater than the same values for the bilayer films prepared using xylitol and mannitol. The formulation with glycerol has been applied for the preparation of active edible coating using the mixture of two hydrolats – lemongrass and curry plant. Obtained coatings have shown great potential for the improvement of packaged cheese shelf-life.Publishe

FABRICATION OF TEMPERATURE AND pH SENSITIVE BIOPOLYMER/CLAY BIOCOMPOSITE AS DRUG CARRIER FOR RANITIDINE – HCl

The scientific studies on drug delivery systems that transport drugs to the targeted tissues, at a certain rate and desired time intervals, have gained popularity. The main goal of the drug delivery and release systems is to maintain the drug level in the blood plasma by balancing the amount of active ingredient. In this study, pH and temperature sensitive drug carriers were prepared using chitosan as a biopolymer and clay as a natural material. The characterization of the prepared materials was performed for structural analysis by FT-IR and for morphological analysis by SEM instruments. The swelling properties of the prepared materials were investigated. In this work, Ranitidine-HCl was used as a model drug. The prepared drug carriers were first loaded with Ranitidine-HCl and release properties of the materials were investigated at two different temperatures (25oC, 37oC) and various pH medium. The data obtained from the experiments indicated that the maximum release of Ranitidine–HCl from the prepared sample was observed at pH=7,6 buffer solution at both temperatures by comparing buffer solutions. It has been shown that the materials prepared in this study are suitable carriers for the Ranitidine-HCl drug active ingredient

The assessment of gamma irradiation ageing of elastomeric materials filled with recycled rubber powder

V International Conference on Radiation in Various Fields of Research : RAD 2017 : book of abstracts; June 12-16, 2017; Budva, Montenegr

Influence of different functionalization methods of multi-walled carbon nanotubes on the properties of poly(L-lactide) based nanocomposites

This paper presents influence of the type of carbon nanotube functionalization on properties of poly(L-lactide) (PLLA) based nanocomposite materials. For this purpose surface modifications of multi-walled carbon nanotubes (MWCNTs) were performed by chemical and irradiation techniques, while thermo gravimetric analysis, UV-Visible and Fourier-transform infrared (FT-IR) spectroscopies confirmed successful covalent functionalization. Series of PLLA bionanocom-posites with different contents of functionalized MWCNTs (0.7; 1.6; 2.1 wt%), were synthesized via ring-opening solution polymerisation of L-lactide. FT-IR analysis confirmed that grafting of L-lactide, under controlled condition, is possible to perform starting from the surface of functionalized MWCNTs. From differential scanning calorimetry results it was concluded that even low contents of chemically and irradiation functionalized MWCNTs had a significant effect on thermal properties of the prepared nanocomposites, raising the values of melting and glass transition temperatures. Thermogravimetric analysis (TGA) has shown that the degradation onset temperature for composites with chemically functionalized MWCNTs, was much higher than that for the neat poly(L-lactide) sample and composites with irradiation functionalized MWCNTs. Morphology studies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that poly(L-lactide) covered surfaces and separated functionalized MWCNTs. Good dispersion of carbon nanotubes in polymer matrix enabled conductivity of synthesized materials, as determined by conductivity tests

The influence of network precursor ratio on the crosslinking and radiation resistance of hybrid elastomeric materials

Materials selected in nuclear processing plants are required to have radiation, thermal and chemical resistance. From experiments on different elastomeric seals materials it was assessed that after a high energy gamma treatment tremendous degradation of properties and compression set exist. Two common network precursors that are used in nuclear power plants are based on ethylene propylene diene rubber (EPDM) and chlorosulfonated polyethylene (CSM). Elastomeric materials based on CSM have good resistance to temperature extremes and chemicals but poor compression set and poor fuel resistance, which is limitation for its sealing application. Blending with other rubbers can improve these properties. Polar CSM rubber can interact with their active functional groups (-SO2Cl) via substitution or condensation reactions. Hydrocarbon origin of EPDM completely saturated chains (without none double bond that imparts an excellent resistance to ozone, weathering, heat, oxidation and polar fluids) are able to absorb more energy without cracking polymeric chain (thus it is classified as radiation-resistant). EPDM rubbers are used in radiation areas for wire coating materials and electrical cables, due to their good resistance to environmental effects. This work aims to the study the influence of network precursor ratio on crosslinking behaviour and radiation resistance of hybrid materials based on CSM/EPDM and high abrasion carbon black particles (iodine adsorption value 82 g/kg). Rubber compounds were prepared using two-roll mill at 40 oC to obtain sheets, which were pressed at 160 oC during 20 minutes at pressure of 16 MPa. Optimal crosslinking time was determined by moving die rheometer (type MDR2000). It was assessed that the optimum curing time of obtained materials increases with increasing content of CSM. The radiation of prepared hybrid materials was carried out using 60Co gamma source with the dose rate 10 kGyh-1 and different total absorbed dose (100, 200 and 400 kGy) at ambient temperature. For blends of two rubbers with dissimilar polarity, distribution of crosslink point can be non-equal through phases. Mechanicals properties and swelling properties were estimated for nonradiated and radiated samples. It was assessed that during radiation process, tensile strength, modulus and hardness and of prepared materials increased, but elongation at break decreased up to dose of 200kGy.VII International Conference on Radiation in Various Fields of Research : RAD 2019 : book of abstracts; June 10-14, 2019; Herceg Novi, Montenegr

Characterization of films based on cellulose acetate/poly(caprolactone diol) intended for active packaging prepared by green chemistry principles

Biodegradable active packaging films based on a cellulose acetate and poly(caprolactone diol) blend with incorporated lemongrass oil were developed. Films were prepared using a novel bio-based plasticizer, glycerol tritartarate, synthesized using the principles of green chemistry. The influence of the plasticizer, as well as the essential oil amount, on the structural, surface, mechanical, and thermal properties of the blend was investigated. The plasticizer was shown to work as a compatibilizer for two polymers, according to the results of scanning electron microscopy and surface energy analysis. Blends with a greater amount of plasticizer possessed better mechanical properties but showed worse resistance to water. The antimicrobial property of the blend with lemongrass oil was found to be superior to that of the blend without essential oil. The incorporation of lemongrass oil into the polymer blend resulted in one more step longer thermal degradation process. The optimal film properties, biodegradability, cost-effective preparation method, and additional functions made these films suitable for the production of packaging for grapefruit.This peer-reviewed accepted version of the article will be available in open access on 15 July 2023. The published article available at the publisher [https://pubs.acs.org/doi/10.1021/acssuschemeng.2c02009