Polycarbonate/polyalkylene terephthalate blends: Interphase interactions and impact strength

Abstract

Blends of polycarbonate (PC) and poly(alkylene terephthalate) (PAT) such as poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) were investigated. It was learned that processes of phase separation in blends consisting of PC and PAT can cause variations in properties of both the amorphous and crystalline phases. In PC/PBT blends the DSC technique did not detect crystalline portion of PBT with its concentrations up to 20 wt %. For PBT ϭ 40 wt %, it forms a continuous phase, and blend's crystallinity is close to the additive values. The glass transition temperature (T g ) shifts to the lower temperature region. The relaxation spectrometry revealed strong adhesion between phases in the blends over the temperature range from the completion of ␤-transition to T gPAT . This interaction becomes weaker between T gPAT and T gPC . Temperature-dependent variations in the molecular mobility and interphases interactions in the blends affect their impact strength. Over the temperature range where interphases interactions occur and the two components are in the glassy state, the blend is not impact resistant. Over the temperature range between T gPAT and T gPC the blends become impact-resistant materials. This is because energy of crack propagation in the PAT amorphous phase-being in a high-elastic state-dissipates. It is postulated that the effect of improving the impact strength of PC/PAT blends, which was found for temperatures between the glass transition temperatures of the mixed components, is also valid for other binary blends.

Structural features and relaxation properties of PET/PC blends containing impact strength modifier and chain extender

“…As this factor much depends on both the melt viscosity and on adhesion strength interaction between the phases in blends of thermodynamically incompatible or partly compatible polymers, it can be assumed that incorporated MDI causes an intensification of interphase adhesion in PET/PC blends along with an enhancement in compatibility of the components. [2]. In the blends studied, the effect of PP/EPDM is evidently reduced to increasing the degree of heterogeneity of the blend in general and of PC phase in particular.…”

“…The analysis of temperature dependences of mechanical loss tangent (tanδ) and dynamic shear modulus (G′) of the samples gave information on the dynamic-mechanical (relaxation) properties of the materials. The tests were run as in other works [2,20], using the reverse torsion pendulum of design developed at MPRI NAS, Belarus. The test frequency was 1 Hz.…”

“…The blends of polycarbonate (PC) with poly(alkylene terephthalates), particularly poly(ethylene terephthalate) (PET), have been the subject of much attention from researchers as well as scientific schools [1][2][3][4]. This can mainly be explained by growing possibilities for developing PET/PC-based engineering materials; their properties are far more advantageous than those of the two homopolymers.…”

“…One of the disadvantages of PET/PC binary blends is their low impact strength measured on notched samples [2]. PET/PC blend materials show relatively high values of impact strength only at temperatures between the component glass transition temperatures (T g PET and T g PC ) [2].…”

“…PET/PC blend materials show relatively high values of impact strength only at temperatures between the component glass transition temperatures (T g PET and T g PC ) [2]. For practical applications, therefore, such PET/PC blends are most suitable that contain special additives, i.e.…”