PET/PC blends: Effect of chain extender and impact strength modifier on their structure and properties

Abstract

Methylene diphenyl diisocyanate (MDI) affects the morphology, rheological, mechanical, and relaxation properties, as well as tendency to crystallize of PET in PET/PC/(PP/EPDM) ternary blends produced by the reactive extrusion. Irrespective of the blend phase structure, the introduction of MDI increases the melt viscosity (MFI dropped), resulting from an increase in the molecular weight of the polymer chains; the PET crystallinity was also reduced. MDI favors compatibility of PET with PC in PET/PC/(PP/EPDM) blends. This is explained by intensified interphase interactions on the level of segments of macromolecules as well as monomer units. The presence of MDI causes a substantial rise in the dynamic shear modulus within the high-elastic region of PET (for temperature range between T g,PET and that of PET cold crystallization); the processes of PET cold crystallization and melt crystallization become retarded; the glass-transition temperatures for PET and PC become closer to each other. MDI affects insignificantly the blend morphology or the character of interactions between the disperse PP/EPDM blend and PET/PC as a matrix. PP/EPDM reduces the intensity of interphase interactions in a PET/PC/(PP/ EPDM), but a rise in the degree of material heterogeneity. MDI does not change the mechanism of impact breakdown in the ternary blends mentioned above. Increased impact strength of MDI-modified materials can be explained by higher cohesive strength and resistance to shear flow at impact loading.

Effect of Nanodisperse Carbon Fillers and Isocyanate Chain Extender on Structure and Properties of Poly(ethylene terephthalate)

“…There is a noticeable difference in the effects of CE alone and its combination with CNM. Thus, the addition of CE leads to the increase of intrinsic viscosity and noticeable reduction of MFI values, which results from increased molecular weight of PET [4,15]. M n 's growth (MFI reduction) of PET containing CNM is not very substantial.…”

“…The dynamic mechanical (relaxation) properties of the materials were found by analyzing temperature dependences of the mechanical loss tangent (tan δ) and dynamic shear modulus (G ) of the samples. The tests were performed using a reverse torsion pendulum (designed at MPRI NAS of Belarus) [3,15]; the frequency was 1 Hz. The temperature measurement accuracy was 0.1 • C, tan δ, ±3%; G , ±1%.…”

“…Several researchers have reported [4,9,14,15] that compounds containing isocyanate groups can be excellent CE for heterochain polyesters and their blends. However, together with the increase of PET molecular weight, partial crosslinking of macromolecules which slows down polymer crystallization is observed [15]. As a result, at first, the efficiency of molten PET processing drops because more time is required for crystallization of formed product that ensures its shape stability.…”

“…It is well known, on the other hand, that crystallization kinetics of thermoplastics, including PET, can be controlled by small quantities of nanofillers such as nanoclays and/or carbon nanomaterials (CNMs) [15,16] added to compositions. It is of interest, therefore, to understand the joint influence of CE and CNM on structural transformations in PET, the set of technological relaxation, and physicomechanical characteristics of the obtained materials.…”

Effect of Weathering and Accelerated Photoaging on PET/PC (80/20 wt/wt%) Melt Extruded Blend

“…Aiming to combine their qualities, blends have been widely studied. Pesetskii et al 1 investigated the effect of an chain extenders and impact modifier on a PET/PC blend. They mentioned the effect of the chain extenders on the morphology, and the increase in the impact strength.…”