Thermal Degradation of Poly(Dimethyl Itaconate)

This article investigates the thermal degradation behaviour of poly(dimethyl itaconate), performed by TG and other degradation procedures, in order to establish the kinetics of the reaction and the probable mechanism of thermal degradation. From TG curves and from GC-MS observations, the occurrence of a dezipping reaction, producing predominantly monomer, was observed, preceded by carbon-carbon bond scissions in the lateral substituents. The results are compared with those known from the literature for the structurally similar poly(methyl methacrylate)

The thermal degradation of some polymeric di-alkyl esters of itaconic acid

One group of polymers that may help relieve the dependence on crude oil is based on itaconic acid, the biotechnological production of which has become feasible. Itaconic acid and its derivatives can easily be incorporated into polymers and may serve as a substitute for petrochemically derived acrylate or methacrylate monomers. The applications of polymers based on itaconic di-esters depend largely on their thermal stability. The thermal stability of poly(di-itaconates) is dependent, not only on the general structure of the monomer repeating unit, but also on the structure of the ester substituent. Depolymerization, initiated by b-scission or random main chain scission, is the dominant thermolysis mechanism in most cases. The depolymerization of poly-(di-itaconates) may be accompanied by de-esterification, elimination, cross-linking, random main or side chain scission and carbonization. Comparison of the thermal degradation mechanism of polymeric di-esters of itaconic acid to that of corresponding poly(methacrylates) confirms the viability of substituting poly(methacrylates) by poly(di-itaconates). [Projekat Ministarstva nauke Republike Srbije, br. 172062

The role of higher education in developing an innovation spirit

8. Конференција академија подунавске региј

Investigation of the toxicity of mercury, copper, zinc and trinitroresorcinol on Lebistes retjculatus. method of survival

Pri oceni toksičnog uticaja žive, bakra. cinka i trinitrorezorcina na Lebistes reticulatus određivani su srednje vreme preživljavanja (ET50), krive toksičnosti i srednje letalne koncentracije (LC50 odnosno TLm). U toku ekspozicije od 120 sati krive toksičnosti žive i bakra u log-log sistemu imaju pravolinijski oblik. Na krivama toksičnosti cinka i trinitrorezorcina jasno se uočavaju prelomne tačke. Za razliku od trinitrorezorcina, kod koga se kriva toksičnosti asimptotski približava vremenskoj osi, kod cinka je ovaj deo krivolinijski što ukazuje da prelomna tačka ne označava koncentraciju praga. Rezultati ovih ispitivanja idu u prilog tvrdnji drugih autora da se početni LC50 teških metala ispoljava samo u sredinama sa dovoljno velikim alkalitetom i dovoljnom količinom kationa koji deluju antagonistički. Pri ekspoziciji od 96 sati, nađene srednje letalne koncentraciie žive, bakra i cinka iznose 0,041, 0,022, i 0,63 mg/l. Hernijske karakte¬ristike upotrebljenog diluenta bile su: pH = 7,2; m-alkalitet = 45 mval; ukupna tvrdoća = 34,2 mg/l CaCO3. Ovim ispitivanjem utvrđeno je da trinitrorezorcin nema hronično toksično djelovanje. Početni LC50 koji se ispoljava u toku 24 sata iznosi. 51,3 mg/l sa granicama poverenja 47,3 i 55,7 mg/l.To evaluate the toxic effect of mercury, copper, zinc and trinitroresorcinol the medium survival time (ET50), toxicity curves and· medium lethal con· centrations were determined. During the exposure of 120 hours the toxicity curves for mercury and copper in the log-log system have a rectilinear shape. The zinc and trinitroresorcinol toxicity curves clearly show points of inflection. Unlike the toxicity curve for trinitroresorcinol which asyrnptotically approaches the time axis, in case of zinc this part is curved showing that point of inflection does not mark a threshold concentration. The results of this investigation are in favour or the assertion of other authors that the initial LC50 of heavy metals produces effect only in alkaline environments with a sufficient amount of cations which act antagonistically. During the exposure of 96 hours, the obtained medium lethal concentrations of mercury, copper and zinc were 0.041, 0.022 and 0.63 mg/l respectively. Chemical properties of the diluent were: pH = 7.2, m-alkalinity = 0.45 mval and the total hardness = 34.2mg/l CaC03. It was found that trinitroresorcinol does not produce a chronic toxic effect. The initial LC50 during the exposure of 24 hours was 51.3 mg/l with confidence limits of 47.3 and 55.7 mg/I

Simplification of the synthesis of the reversible addition–fragmentation chain transfer agent 2-(2-cyanopropyl)-dithiobenzoate

The general literature procedure for the preparation of the reversible addition–fragmentation chain transfer (RAFT) agent 2-(2-cyanopropyl)-dithiobenzoate (CPDB) was modified by omitting the recrystallisation of the intermediate di(thiobenzoyl)disulphide. The yield of the CPDB in the simplified synthesis was increased four times compared to the standard one. The behaviour of the CPDB obtained by the modified procedure and by the standard one in the polymerisation of methyl methacrylate was investigated. The CPDB synthesized by the simplified procedure showed itself to be a good RAFT agent, giving excellent control over the polymerisation of methyl methacrylate and it behaved in the same manner as the CPDB prepared by the literature method. The obtained poly(methyl methacrylate) had a narrow molecular weight distibution (PD = 1.1)

Uvod u verifikaciju instrumenta GOHAI za merenje oralnozdravstvenog kvaliteta života osoba sa zubnim nadoknadama primenom preliminarne srpske verzije - pilot studija

Background/Aim. Quality of life related to health should be seen as a multidimensional concept that, in addition to the physical symptoms associated with a disease and treatment, should include physical, psychological and social functioning of a person. The primary objective of this study was to use the Serbian preliminary version of the Geriatric Oral Health Assessment Index (GOHAI) questionnaire in order to examine the consistency, reliability and stability, as well as an introduction to the verification tool. Methods. The GOHAI questionnaire with 6-level Likert scale, translated into Serbian, including the relevant oral health characteristics (oral hygiene, required dentures, number of teeth extracted), was filled by five specialists in prosthodontics for 30 randomly selected respondents, before and after the dental prosthetic treatment. Subsequently, in order to measure the reliability of the questionnaire, 27 patients were reinterviewed. Results. The value of Cronbach's Alpha Coefficient (Crα) before the treatment was 0.878, and after the treatment it was 0.788 confirming the internal consistency and stability of the questionnaire. The validity of discriminatory properties of the GOHAI was confirmed by the Spearman's correlation coefficient (r), which was highly significantly associated with oral health characteristics, confirming the high reliability of the measurement. The results of test-retest analysis measured by the individual Pearson's correlation coefficient (r) were in the range of 0.34-0.97, and for the total score r was 0.927, while the Kappa coefficient was 0.63. The correlation analysis of the GOHAI score before the treatment showed that for 10 questions there was a statistically significant correlation of the score with the answers to the questions, and for 6 questions Spearman's r was ≥ 0.7. After the treatment a highly significant correlation of the GOHAI was shown with the answers to 10 questions, while for 5 questions the Spearman's r was > 0.6. The GOHAI average score before the treatment was 19.44 ± 11.12, and after the treatment 2.77 ± 3.83, where the lower value indicates better quality of life. Conclusion. The results of this pilot study confirm internal consistency and stability of the Serbian preliminary version of the GOHAI questionnaire and the causal relation between the quality of life and the characteristics of oral health of the patients with dentures. Accordingly, instrument verification is recommended.Uvod/Cilj. Kvalitet života u vezi sa zdravljem treba posmatrati kao multidimenzioni koncept koji, pored fizičkih simptoma vezanih za bolest i lečenje, treba da obuhvati i fizičko, psihičko i društveno funkcionisanje osobe. Primarni cilj studije bio je da se korišćenjem preliminarne srpske verzije upitnika Geriatric Oral Health Assessment Index (GOHAI) ispita konzistentnost, pouzdanost i stabilnost, kao uvod u verifikaciju instrumenta. Metode. GOHAI upitnik sa 6- stepenom Likertovom skalom, preveden na srpski jezik, koji je uključivao i oralnozdravstvene karakteristike (oralna higijena, potrebne zubne nadoknade, broj izvađenih zuba), popunjavan je od strane petoro specijalista stomatološke protetike za 30 slučajno izabranih ispitanika, pre i posle stomatoprotetskog lečenja. Naknadno, radi merenja pouzdanosti upitnika, ponovo je intervjuisano 27 ispitanika. Rezultati. Vrednost Cronbach's Alpha Coefficient (Crα pre lečenja bila je 0,878, a posle lečenja 0,788, čime su potvrđene interna konzistentnost i stabilnost upitnika. Valjanost diskriminatornog svojstva GOHAI potvrđena je vrednostima Spearmanovog koeficijenta korelacije (r), koji je značajan kada su u pitanju oralnozdravstvene karakteristike, čime je potvrđena valjanost merenja. Rezultati test-retest analize merene pojedinačnim Pearsonovim koeficijentom korelacije (r) bili su u rasponu 0,34-0,97, a za ukupan skor r je bio 0,927, dok je Kappa koeficijent bio 0,63. Korelaciona analiza GOHAI pre lečenja ukazala je da je za 10 pitanja postojala značajna povezanost skora sa odgovorima na pitanja, a za 6 Spearmanov r bio je ≥ 0,7. Posle lečenja utvrđena je značajna veza GOHAI sa odgovorima na 10 pitanja, a za 5 Spearmanov r bio je > 0.6. Prosek GOHAI skora pre lečenja bio je 19,44 ± 11,12, a posle lečenja 2,77 ± 3,83, gde manja vrednost ukazuje na bolji kvalitet života. Zaključak. Rezultati ovog pilot istraživanja potvrdili su internu konzistentnost i stabilnost preliminarne srpske verzije GOHAI upitnika, kao i kauzalnu vezu kvaliteta života sa karakteristikama oralnog zdravlja ispitanika sa zubnim nadoknadama, te se može preporučiti sprovođenje verifikacije instrumenta

The thermo-oxidative degradation of poly(2-chloroethyl methacrylate) in the presence of antioxidants

U radu je ispitana oksidativna termijska degradacija poli(2-hloretil metakrilata) (PCEMA) u prisustvu komercijalnih antioksidanata amino tipa CHIMASSORB 119 (CH 119) i CHIMASSORB 944 (CH 944) i smeše antioksidanata, IRGANOX 1010, fenolnog derivata, i IRGAPHOS 168, fosfita (maseni udeli 1:1). Ispitivanja su izvedena termogravimetrijskom (TG) metodom, a na osnovu karakterističnih temperatura 10% gubitka mase, oblika diferencijalnih TG (DTG) krivih i srednjih vrednosti energije aktivacije termijske degradacije, ispitivan je uticaj pojedinih antioksidanata.The oxidative thermal degradation of poly(2-chloroethyl methacrylate) (PCEMA) was studied in the presence of the following commercial antioxidants: CHIMASSORB 119 (CH 119) and CHIMASSORB 944 (CH 944), both based on amines, and a mixture of IRGANOX 1010, a phenol derivative, and IRGAPHOS 168, a phosphite (mass ratio 1:1), by the thermogravimetric (TG) method. On the basis of the obtained results, the characteristic temperatures of 10% mass loss, Tio%, the shape of the differential TG (DTG) curves and mean values of the thermal degradation activation energy, Ea, it was concluded that the commercial photostabilisers CH 119 and CH 944 could not successfully stabilize the thermal degradation of PCEMA, while in the case of the presence of the antioxidant mixture IRGANOX 1010 and IRGAPHOS 168 (1:1) slight stabilizing effects were observed

THERMAL CONDUCTANCE OF HELICALLY COILED CARBON NANOTUBES

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon- based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials.In this paper we present the results of thermal conductance s of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of s of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon- based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials.In this paper we present the results of thermal conductance s of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of s of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model

Supplementary data for article : Panic, V. V.; Seslija, S. I.; Popovic, I. G.; Spasojevic, V. D.; Popovic, A. R.; Nikolic, V. B.; Spasojevic, P. M. Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid. Biomacromolecules 2017, 18 (12), 3881–3891. https://doi.org/10.1021/acs.biomac.7b00840

Supporting information for: [https://doi.org/10.1021/acs.biomac.7b00840]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2568]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3058