| Abstract | U ovom radu ispitivana su toplinska svojstva i toplinska stabilnost polimera: EPDM, PE-HD, PP, PVC, PVAc, PS, PPE, EVA, SAN, ABS-a te Dobeckan poliesterske smole. Polimeri su bili podijeljeni u tri grupe: s obzirom na oblik makromolekule (EPDM, PE-HD i Dobeckan), s obzirom na supstituent vodika (PE-HD, PP, PVC, PVAc i PS) te na kopolimere (PPE, EVA, SAN i ABS). Toplinska svojstva određena su diferencijalnom pretražnom kalorimetrijom (DSC). Toplinska stabilnost polimera određena je primjenom termogravimetrijske analize (TGA). Rezultati analize prve grupe polimera pokazali su kako su EPDM i PE-HD kristalasti, a Dobeckan amorfan polimer. Staklište polimera raste sa stupnjem umreženja polimera, a brzina kristalizacije ovisi o temperaturi kristalizacije. Dobeckan i EPDM razgrađuju se u dva stupnja u odnosu na PE-HD koji se razgrađuje u jednom stupnju. U skladu sa stupnjem kristalnosti i umreženja polimera toplinska stabilnost raste u nizu EPDM<Dobeckan<PE-HD. Kod druge grupe polimera dobiveni rezultati analize pokazali su da PP kristalizira brže od PE-HD-a zbog veće sklonosti grananju lanaca. PVC, PVAc i PS su amorfni te zbog veće veličine supstituenata vodika na glavnom lancu pokazuju veća staklišta. Veličina supstituenata vodika kod PP-a i PS-a ograničava rotacijsku slobodu lanca što povećava staklište, dok alifatski acetatni supstituent kod PVAc-a povećava rotacijsko gibanje i limitira pakiranje lanaca čime snižava staklište u odnosu na PS. Značajno odstupanje od literaturnih vrijednosti pokazuje PVC zbog mogućeg dodatka aditiva u komercijalnom proizvodu. PE-HD i PP toplinski su stabilniji zbog određenog udjela kristalne faze. PE-HD toplinski je najstabilniji u odnosu na ostale polimere zbog jakih primarnih veza, a reaktivne skupine ponavljajućih jedinica PVC-a čine ga toplinski najnestabilnijm u ovoj grupi polimera. Analiza grupe kopolimera pokazala je da su PPE i EVA kristalaste, a SAN i ABS amorfne građe. EVA zbog većih vrijednosti entalpija sadrži veću količinu kristalne faze u odnosu na PPE. Toplinska svojstva kopolimera između su toplinskih svojstava homopolimera od kojih su sastavljeni. Pojedini kopolimeri zbog prisutnih aditiva i punila pokazuju manje toplinske stabilnosti od njihovih homopolimernih konstituenata. |
| Abstract (english) | In this work, the thermal properties and thermal stability of EPDM, PE-HD, PP, PVC, PVAc, PS, PPE, EVA, SAN, ABS-a te Dobeckan polyester resin were investigated. The polymers were divided into three groups: according to the shape of the macromolecule (EPDM, PE and Dobeckan), according to the hydrogen substituent (PE-HD, PP, PVC, PVAc and PS) and the group of copolymers (PPE, EVA, SAN and ABS). Thermal properties were determined via differential scanning calorimetry (DSC). The thermal stability of the polymers was determined using thermogravimetric analysis (TGA). The results of analysis of the first group of polymers showed that EPDM and PE-HD are crystalline and Dobeckan is an amorphous polymer. The glass transition temperature increases with the degree of crosslinking of the polymer chains and the crystallization rate depends of the temperature of crystallization. In accordance with the degree of crystallinity and crosslinking, the thermal stability increases in the order EPDM<Dobeckan<PE-HD. In the second group of polymers, the results have showed that PP crystallizes faster than PE-HD due to greater tendency of chain branching. PVC, PVAc and PS are amorphous polymers and, due to a greater size of the hydrogen substituents on the main chain, show higher glass transition temperatures. The size of the substituents in PP and PS limit the rotational freedom of the chain and so increases glass transition temperature, while the aliphatic acetate supstituent in PVAc increases the rotational motion and limits the packaging of the chain, thus lowering the glass transition temperature in comparison to PS. Significant deviation from the literature values is shown by PVC, possibly because of the addition of additives in the commercial product. PE-HD and PP are more thermally stable due to a certain proportion of the crystalline phase. PE-HD is thermally the most stable due to strong primary bonds, and reactive groups of repeating units in PVC make it the most thermally unstable in this group of polymers. Analysis of the third group consisting of copolymers shows that PPE and EVA are crystalline, and SAN and ABS are amorphous. EVA contains a larger amount of crystal due to higher enthalpy values. The thermal properties of copolymers are between thermal properties of the homopolymers of which they are composed. Some copolymers, due to the additives and fillers present, show less thermal stability than their homopolymer constituents. |
