Title Toplinska svojstva polimera Title (english) Thermal properties of polymers Author Marta Hac Mentor Sanja Lučić Blagojević (mentor)Committee member Sanja Lučić Blagojević (predsjednik povjerenstva)Committee member Zrinka Buhin Šturlić (član povjerenstva)Committee member Domagoj Vrsaljko (član povjerenstva)Granter University of Zagreb Defense date and country 2015-09-11, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Polimeri se ubrajaju u najvažnije tehničke materijale današnjice te služe kao zamjena
za uobičajene materijale. Svaki polimer ima karakterističnu strukturu te zbog toga i različita
svojstva koja utječu na njihovu primjenu. U ovom radu ispitivana su toplinska svojstva i
toplinska stabilnost polistirena (PS), polistirena velike udarne žilavosti (HIPS), polietilena
niske gustoće (PE-LD), polietilena visoke gustoće (PE-HD), polikaprolaktona (PCL),
polilaktida (PLA) i poliuretana (PUR). Primjenom diferencijalne pretražne kalorimetrije
(DSC) određena su toplinska svojstva polimera na temelju karakterističnih vrijednosti
prijelaznih temperatura i entalpija, prikazanih na DSC termogramima. Toplinska stabilnost
određena je termogravimetrijskom analizom (TGA).
DSC analiza pokazala je kako amorfni polimeri, PS i HIPS imaju visoka staklišta zbog
benzenskih prstenova koji ukrućuju njihovu strukturu i onemogućavaju rotacije segmenata
makromolekula. Suprotnost polistirenima su PE-LD i PE-HD koji imaju vrlo nisku vrijednost
staklišta što ukazuje na veću mogućnost rotacija segmenata makromolekula uslijed njihove
jednostavne strukture. Zbog manje granatosti lanca, PE-HD brže i više kristalizira te
posjeduje uređenije kristalne forme od PE-LD-a. PLA i PCL, biorazgradivi su i kristalasti
polimeri potpuno različitih staklišta, kristalizacije i taljenja. PLA ima više staklište i sporiju
kristalizaciju zbog metilnih skupina u njegovom glavnom lancu koje ograničavaju rotaciju
segmenata makromolekula i ometaju kristalizaciju. Toplinska svojstva PUR-a ovise o
njegovoj strukturi, odnosno udjelu tvrdih i mekih segmenata. Rezultati su pokazali kako PUR
i PLA imaju slične karakteristične prijelaze, međutim, staklište, temperature kristalizacije i
taljenja PLA su na znatno višim temperaturama u odnosu na PUR što je posljedica krutosti
makromolekula PLA.
Rezultati toplinske stabilnosti pokazali su kako najbolju toplinsku stabilnost ima PEHD,
dok nešto manju stabilnost od njega ima PE-LD upravo zbog granatije strukture koja
ograničava formiranje kristalnih formi s jakim sekundarnim vezama. Najmanju toplinsku
stabilnost od svih ispitivanih polimera u ovom radu ima PLA.
Abstract (english) Today polymers are one of the most important technical materials and serve as a
substitute for the usual materials (wood and metal). Each polymer has characteristic structure
and therefore different properties which affects their use. In this work thermal properties and
thermal stability of polystyrene (PS), high-impact polystyrene (HIPS), low-density
polyethylene (PE-LD), high-density polyethylene (PE-HD), polycaprolactone (PCL),
polylactide (PLA) and polyurethane (PUR) were investigated. Characteristic value of
transition temperatures and enthalpies were determined using differential scanning
calorimetry (DSC). Thermal stability was determined with thermogravimetric analysis (TGA).
The DSC analysis showed that amorphous polymers, PS and HIPS have high glass
transition temperatures due to the benzene rings which stiffen their structure and prevent
rotations of macromolecules segments. Opposite of the polystyrenes are PE-LD and PE-HD,
which have a very low glass transition temperature due to the higher rotation of
macromolecules segments as a consequence of their simple structure. PE-HD crystallize
more, crystallization is faster and more arranged crystals are form due to less branching than
in PE-LD. PLA and PCL are biodegradable and crystalline polymers, but they crystallize
differently and have completely different glass transition temperatures. Crystallization of PLA
is slower and it has higher glass transition temperature due to methyl groups in its main chain
which limits the rotation of macromolecules segments and hinder the crystallization. Thermal
properties of PUR depend on its structure, i.e. proportion of hard and soft segments. Results
showed that PUR and PLA have similar characteristic transitions, but glass transition, as well
as crystallization and melting temperatures of PLA are at significantly higher temperatures,
compared to PUR, as a consequence of macromolecules stiffness.
The results of thermal stability showed that the most stabile is PE-HD, while PE-LD is
a little less stable, due to more branched structure, which limits the formation of crystalline
forms with strong secondary bonds. The lowest thermal stability of all tested polymers in this
work has PLA.
Keywords
polistiren (PS)
polistiren velike udarne žilavosti (HIPS)
polietilen niske gustoće (PE-LD)
polietilen visoke gustoće (PE-HD)
polikaprolakton (PCL)
polilaktid (PLA)
poliuretan (PUR)
toplinska stabilnost polimera
struktura polimera
Keywords (english)
polystyrene (PS)
high- impact polystyrene (HIPS)
low-density polyethylene (PE-LD)
high-density polyethylene (PE-HD)
polylactide (PLA)
polycaprolactone (PCL)
polyurethane (PUR)
thermal properties of polymers
thermal stability of polymers
structure of polymers
Language croatian URN:NBN urn:nbn:hr:149:427099 Study programme Title: Chemical Engineering - Undergraduate study Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2016-11-21 14:12:22
