Improving the Thermo-Oxidative Stability of Polybutylene Terephthalate

Lupezheva, A. O.; Mashukov, N. I.; Борукаев, Т. А.

doi:10.1177/0307174x0202901019

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“…The rheograms of melts of pure PP, PBT, and the blends at 250°C obtained by melting granulate undergoing both one and two extrusions were almost identical, which indicates the insignificant role of degradation processes here. These results are comparable to the experimental data published in [14] and [16]. The statistical mean results of studying the rheological properties of melts of PP, PBT, and blends at 250°C are shown in Fig.…”

Section: Extruder Zonessupporting

confidence: 90%

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Study of the rheological properties of melts of polypropylene and poly(butylene terephthalate) blends

et al. 2006

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The viscosity properties of melts of fibre-forming polypropylene (PP) and poly(butylene terephthalate) blends were investigated in the entire range of ratios at different stresses and shear rate gradients at 230-250°C. It was shown that melts of fibre-forming PP and PBT blends are weakly crosslinked systems. The effect of the mass ratio of PP and PBT on the apparent activation energy of viscous flow of melts of the blends was investigated at different shear stresses and shear rate gradients. It was hypothesized that this blend can be assigned to the group of limitedly compatible systems. The probability of compatibility of the polymers in the melt appears when up to 20% PBT is incorporated in the PP. The blends are not compatible for the remaining ratios of polymers in the investigated system.We know that the performance properties of articles made of polymer blends are determined to a significant degree by the mutual dispersion of the components. The complete (thermodynamic) compatibility of film-and fibre-forming polymers in a melt is a somewhat rare exception. The possibility of spontaneous molecular mixing of different macromolecules (their mutual solubility) is due to both the enthalpic and the entropic aspects of the process of attaining the equilibrium state [1].The important amount of accumulated experimental and theoretical data indicates the validity of the statement that the relaxation (and consequently structural-mechanical) characteristics of polymers in the viscous-flow and solid states are somewhat close. This is due to the cooperativity of deformation processes on the supramolecular level [2, 3], which substantiates the approach to predicting the possibility of combining different linear polymers in the solid state based on the results of studying the temperature dependence of the viscosity of melts of polymer blends in the entire range of ratios of components (naturally, outside of the binodal phase boundary). It is evident that the compatibility (mutual solubility) of polymers both in the solid state and in melts is determined by the same thermodynamic factors as the mutual solubility of low-molecular-weight compounds, but their primary structure and the flexibility of linear macromolecules must be taken into consideration [3], since molecular mixing can only be realized on the segmental level.According to the FloryScott concept [4], the thermodynamic compatibility of polymers in the solid state can be predicted with some degree of probability by comparing the solubility parameters of the components of the blend: (δ s.1 δ s.1 ) = = Δδ ≤ 1.5 (cal⋅cm -3 ) 0.5 ≡ 3075 (J⋅m -3 ) 0.5 , where the solubility parameters δ p.i of the miscible polymers can be validly estimated with the Askadskii method [5]:, 1

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Section: Extruder Zonessupporting

confidence: 90%

“…This problem can be solved by two methods: by selecting the optimum stabilizing system [14][15][16] or by decreasing the processing temperature. Incorporation of thermal stabilizers alters the rheological properties of the system.…”

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confidence: 99%