Mehanizam popuštanja i mehanička svojstva polimera

undergraduate thesis

• Title (english): Mechanisms of failure and mechanical properties of polymers
• Author: Tomislav Blagec
• Mentor: Sanja Lučić Blagojević (mentor)
• Committee member: Sanja Lučić Blagojević (predsjednik povjerenstva)
• Committee member: Mirela Leskovac (član povjerenstva)
• Committee member: Domagoj Vrsaljko (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2021-09-22, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

Mehanička svojstva polimera, koja ovise o njihovoj molekularnoj strukturi potrebno je poznavati tijekom upotrebe polimera. U ovom radu ispitivana su mehanička svojstva polietilena visoke gustoće (PE-HD), polipropilena (PP), polivinil klorida (PVC), polivinil acetata (PVAc), polistirena (PS), poli(propilen-co-etilena), (PPE), poli(etilen-co-vinil acetata), (EVA), poli(stiren-co-akrilonitrila), (SAN), poli (akrilonitrilL-co-butadien-co-stirena), (ABS) i etilen propilen dien polimera (EPDM) i povezana su s njihovom strukturom. Rastezna svojstva ispitana su testom jednoosnog naprezanja, a relaksacijska svojstva testom relaksacije naprezanja. Testovi su provedeni na univerzalnoj mehaničkoj kidalici, a uzorci za ispitivanja pripremljeni su na hidrauličkoj preši. Mehanička svojstva ovise o nekoliko čimbenika strukture polimera. Značajno ovise o izgledu tj. obliku makromolekule. Makromolekule mogu biti linearne, granate ili umrežene što ovisi o prostornom razmještaju i vrsti atoma. Tako PE-HD ima linearnu strukturu dok EPDM ima umreženu strukturu. U linearnoj strukturi PE-HD prevladavaju kristalne faze te iako je u viskoelastičnom stanju, ima veliko prekidno naprezanje i veliko naprezanje u točki popuštanja. EPDM ima nizak stupanj umreženja zbog kojeg ima veliko prekidno istezanje i malo prekidno naprezanje. Ovisno o vrsti supstituenta koji je vezan na glavni lanac u ponavljanoj jedinici također značajno ovise mehanička svojstva. Primjerice PS je krut materijal zbog nemogućnosti rotacijske slobode koju uzrokuje veliki benzenski supstituent u ponavljanoj jedinici PS-a dok primjerice u PVC-u kloridni supstituent povećava temperaturu staklišta zbog dipol – dipol veze između ugljika i klora jer za takvu vezu su potrebne jače intermolekulske sile, te se stoga mijenjaju mehanička svojstva. Kopolimerizacijom se isto tako značajno mijenjaju mehanička svojstva. Primjerice SAN je dobiven kopolimerizacijom stirena i akrilonitrila. Akrilonitril povećava naprezanje u materijalu što rezultira velikim modulom elastičnosti i velikim naprezanjem u točki loma.

Abstract (english)

The mechanical properties of polymers, which depend on their molecular structure need to be known during the use of polymers. In this thesis the mechanical properties of high-density polyethylene (PE-HD), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl acetate (PVAc), polystyrene (PS), poly (propylene-co-ethylene), (PPE), poly (ethylene-co-vinyl acetate), (EVA), poly (styrene-co-acrylonitrile), (SAN), poly (acrylonitrile-co-butadiene-co-styrene), (ABS) and ethylene propylene diene polymers (EPDM) were investigated and related to their structure. Tensile properties were tested with a uniaxial stress test and relaxation properties with a relaxation test. The tests were performed on a universal mechanical testing machine and the test samples were prepared on a hydraulic press. The mechanical properties depend on several factors of the polymer structure. They significantly depend on the shape of the macromolecule. Macromolecules can be linear, branched or crosslinked depending on the spatial arrangement and type of atoms. The PE-HD has a linear structure while EPDM has a crosslinked structure. The linear structure of PE-HD is dominated by crystalline phases and although it is in a viscoelastic state, it has a large stress at break and a large stress at the yield point . EPDM has a low degree of crosslinking due to which it has high elongation and low tensile stress. The mechanical properties also depend significantly on the type of substituent attached to the main chain in the repeating unit. For example, PS is a stiff material due to the impossibility of rotational freedom caused by a large benzene substituent in the repeated unit of PS while for example in PVC chloride substituent increases the glass temperature due to dipole - dipole bond between carbon and chlorine and thus change mechanical properties. Copolymerization also significantly changes the mechanical properties. For example, SAN was obtained by copolymerizing styrene and acrylonitrile. Acrylonitrile increases the stress in the material resulting in a large modulus of elasticity and a large stress at the breaking point.

• Keywords: mehanička svojstva; PE-HD; PP; PVC; PVAc; PS; PPE; EVA; SAN; ABS; EPDM
• Keywords (english): mechanical properties; PE-HD; PP; PVC; PVAc; PS; PPE; EVA; SAN; ABS; EPDM
• Language: croatian
• URN:NBN: urn:nbn:hr:149:712898
• Study programme: Title: Chemical Engineering - Undergraduate study; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka kemijskog inženjerstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-03-23 12:04:49