Enhancing the impact resistance of PET copolyesters by rubber toughening
Publicerad
Författare
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Glassy thermoplastic polymers are prone to brittle fractures. To enhance their
mechanical properties and, consequently, their durability, it is imperative to focus
on toughness, specifically impact resistance, which determines the material’s mechanical
failure limit. This thesis focuses on improving the impact resistance of
PET copolyesters through rubber toughening. It delves into the impact and tensile
properties of PET copolyesters (PET1, PET2, and PET3), aiming to unravel the
structure-property relationship. The study involved the preparation of tensile and
impact specimens via melt extrusion and injection molding. A DSC analysis confirmed
the nature of these copolyesters, revealing PET3 as semi-crystalline, distinct
from the amorphous PET1 and PET2. Impact tests indicated that PET2 achieved
an improvement of impact properties at 15 wt.% rubber concentration, while PET1
accomplished this at 20 wt.%. Tensile tests yielded similar results for PET1 and
PET2 but showed reduced deformability as the impact modifier concentration increased
from 15 wt.% to 20 wt.%. In its unmodified state, PET3 exhibited remarkable
plastic deformability, which decreased with an increase in rubber concentration.
PET3’s impact properties showed no enhancement with increased modifier concentration.
Morphological analysis of modified PET copolyesters revealed increasing
amounts of cavitation in PET1 and PET2 as the concentration increased from 15
wt.% to 20 wt.%, whereas PET3 exhibited cleavage brittle fractures regardless the
modifier concentration. The presence of cavitation indicates that shear yielding is
the dominant deformation mechanism.
Beskrivning
Ämne/nyckelord
brittle, durability, impact resistance, rubber toughening, melt extrusion, deformability, shear yielding, amorphous