Surface evolution of polycarbonate/polyethylene terephthalate blends induced by thermal treatments (original) (raw)
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Journal of Polymer Science Part A: Polymer Chemistry, 1993
The chemical reactions occurring in the thermal treatment of bisphenol-A polycarbonate (PC) and poly(methyl methacrylate) (PMMA) blends have been investigated by nuclear magnetic resonance (NMR), mass spectrometry (MS), size exclusion chromatography (SEC), and thermogravimetry (TG). Our results suggest that in the melt-mixing of PC/PMMA blends, at 230ЊC, no exchange reactions occur and that only the depolymerization reaction of PMMA has been observed. In the presence of an esterexchange catalyst (SnOBu 2), an exchange reaction was found to occur at 230ЊC, but no trace of PC/PMMA graft copolymer has been observed. Instead, an exchange reaction between the monomer methyl methacrylate (MMA), generated in the unzipping of PMMA chains, and the carbonate groups of PC has been suggested. This is due to the diffusion of MMA at the interface or even into the PC domains, where it can react with PC producing low molar mass PC oligomers bearing methacrylate and methyl carbonate chain ends and leaving the undecomposed PMMA chains unaffected. The TG curves of PC/PMMA blends prepared by mechanical mixing and by casting from THF show two separated degradation steps corresponding to that of homopolymers. This behavior is different from that of a transparent film of PC/PMMA blend, obtained by solvent casting from DCB/CHCl 3 , which shows a single degradation step indicating that the degradation rate of PC is increased by the presence of PMMA in the blend. The thermal degradation products obtained by DPMS of this blend consist of methyl methacrylate (MMA), cyclic carbonates arising from the degradation of PMMA and PC, respectively, and a series of open chain bisphenol-A carbonate oligomers with methacrylate and methyl carbonate terminal groups. The presence of the latter compounds suggests a thermally activated exchange reaction occurring above 300ЊC between MMA and PC. The presence of bisphenol-A carbonate oligomers bearing methyl ether end groups, generated by a thermally activated decarboxylation of the methyl carbonate end groups of PC, has also been observed among the pyrolysis products.
Journal of Applied Polymer Science, 1985
In this work the reactions taking place during melt mixing of bisphenol-A polycarbonate (PC) with poly(ethy1ene terephthalate) (PET) were studied by selective degradation of PC sequences, solubility tests, and IR spectroscopy. It was found that exchange reactions between PC and PET took place, contrary to what has been previously suggested by other authors. Kinetic constants were evaluated from intrinsic viscosity measurements of PET blocks. The reaction rate was slow when only the Sb catalyst (residues of the PET polymerization) were present, but it was significantly accelerated by the addition of Ti(OBu1,. In the presence of the latter catalyst, other side reactions, leading to discoloration and gas evolution, took place.
1993
This study shows that is possible to determine the composition and microstructure of the copolyester formed in the melt-mixing process of poly(ethy1ene truxillate) a) (PETx) and poly-(ethylene terephthalate) (PET), by applying a novel method of statistical modeling of mass spectra of copolymers. The peak intensities of molecular ions appearing in the fast atom bombardment mass spectrum of the melt-mixed equimolar mixture of PETx and PET were found to reflect the relative amounts of oligomers present in the sample and to be directly related to the microstructure of the copolymer formed. The statistical analysis of copolymers allows one to generate a number of different theoretical mass spectra that can be fitted with the experimental mass spectrum data, thus determining the most likely copolymer composition.
Polymer, 2005
Poly(ethylene terephthalate) (PET) (IV:0.15 dL/g) oligomer was obtained by depolymerisation of high molecular weight PET. Polycarbonate (PC) oligomer (IV: 0.15 dL/g) was synthesized by standard melt polymerization procedure using bisphenol A and diphenyl carbonate in the presence of a basic catalyst. Blends of varying compositions were prepared by melt blending the chemically distinct PET and PC oligomers. The copolymer, poly(ethylene terephthalate-co-bisphenol A carbonate) was synthesized by simultaneous solid state polymerization and ester-carbonate interchange reaction between the oligomers of PET and PC. The reaction was carried out under reduced pressure at temperatures below the melting temperature of the blend samples. DSC and WAXS techniques characterized the structure and morphology of the blends, while 1 NMR spectroscopy was used to monitor the progress of interchange reactions between the oligomers. The studies have indicated the amorphisation of the PET and PC crystalline phases in solid state with the progress of solid-state polymerization and interchange reaction.
Journal of Applied Polymer Science, 2011
We investigated the reactive melt blending of poly(ethylene terephthalate) (PET) and poly(trimethylene terephthalate) (PTT) in terms of the thermal properties and structural features of the resultant materials. Our main objectives were (1) to investigate the effects of the processing conditions on the nonisothermal melt crystallization and subsequent melting behavior of the blends and (2) to assess the effects of the blending time on the structural characteristics of the transreaction products with a fixed composition. The melting parameters (e.g., the melting temperature, melting enthalpy, and crystallization temperature) decreased with the mixing time; the crystallization behavior was strongly affected by the composition and blending time. Moreover, a significant role was played by the final temperature of the heating treatment; this meant that interchange reactions occurred during blending and continued during thermal analysis. The wide-angle X-ray diffraction patterns obtained under moderate blending conditions showed the presence of crystalline peaks of PET and PTT; however, the profiles became flatter after blending. This effect was more and more evident as the mixing time increased. Transesterification reactions between the polyesters due to longer blending times with an intermediate composition led to a new copolymer material characterized by its own diffraction profile and a reduced melting temperature. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 698-705, 2011
Analytical Chemistry, 2004
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to quantitatively correlate to the surface chemical composition determined from XPS in poly-(styrene-cop -hexafluorohydroxyisopropyl-r-methyl styrene)/poly(4-vinyl pyridine) (PS(OH)/PVPy) blends or complexes when the p-(hexafluoro-2-hydroxyisopropyl)r-methylstyrene (HFMS) contents in PS(OH) copolymers were gradually increased. It was found that different mixing thermodynamics, such as immiscibility, miscibility, and complexation, have little effect on the quantitative analysis of PS(OH) copolymers in the blends or complexes using TOF-SIMS. In the positive spectra, either the normalized intensities or relative peak intensities can be used to quantitatively analyze the surface HFMS, PS(OH), or PVPy concentration when peaks at m/z) 257, 271, 285, and 373 are used for HFMS, peaks at m/z) 91, 103, 105, 115 for styrene, and peaks at m/z) 132, 195, 209 for PVPy. In the negative spectra, the normalized intensities of peaks characteristic of PVPy seem to be not affected by hydrogen bonding formation and can be used in quantitative analysis, whereas peaks characteristic of HFMS, such as a peak at m/z) 283, cannot be used in quantitative analysis due to enhancement of its secondary ion yield resulting from hydrogen bond formation.
Polymer Engineering and Science, 2010
The macroscopic and microscopic melt-crystallization kinetics of poly(trimethylene terphthalate) (PTT)/polycarbonate (PC) blends have been measured by differential scanning calorimetry (DSC), and optical microscopy (OM). The results are analyzed in terms of the Avrami equation and the Hoffman–Lauritzen crystallization theory (HL model). Blending with PC did not change the crystallization mechanism of PTT, but reduced the crystallization rate compared with that of neat PTT at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature. The spherulitic morphology of PTT was influenced apparently by the crystallization temperature and by the addition of PC. X-ray diffraction shows no change in the unit cell dimension of PTT was observed after blending. Through the HL theory, the classical regime II→III transition was detected for the neat PTT and the blends. The nucleation parameter (Kg), the fold-surface free energy (σe), and the work of chain folding (q) were calculated. Blending with PC decreased all the aforementioned parameters compared with those of neat PTT. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Journal of Thermal Analysis and Calorimetry, 2007
The effects of processing time and concentration of cobalt acetylacetonate III complex in poly(ethylene terephthalate)/polycarbonate reactive blending were investigated. The blend was prepared in an internal mixer at 270°C, 60 rpm, at different processing times (5-20 min) and catalyst concentration (0.00625-0.075 mass%). The reaction product was evaluated by differential scanning calorimetry (DSC), thermogravimetry (TG) and wide angle X-rays scattering (WAXS).
Spectroscopic analysis of poly (ethylene naphthalate)poly (butylene terephthalate) blends
Journal of Applied …, 2007
The characteristics of poly(butylene terephthalate) (PBT), poly(ethylene naphthalate) (PEN), and blends with 30, 40, 50, 60, and 70 wt % PEN prepared by melt-blending were analyzed using Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, solid-state nuclear magnetic resonance (NMR), and Xray photoelectron spectroscopy. The spectroscopic analyses provide no direct evidence for the occurrence of transesterification reactions occurring during melt-processing of the blends under the conditions that were used. The improved mechanical properties of the PBT/PEN blends are attributed to physical interactions occurring over a large interfacial area. X-ray diffraction and high-resolution solid-state carbon-13 (13 C) NMR confirmed the formation of the a-PEN phase after annealing samples at 2008C for 19 h.
Polymer Degradation and Stability, 2014
A thermal degradation model was developed for blends of Poly(ethylene terephthalate) (PET)/Poly(methyl methacrylate) (PMMA) subjected to non-isothermal (dynamic) thermogravimetry at four heating rates (5, 10, 15 and 20 C/min). The model developed enabled the assessment of pre-exponential factor (A) and apparent activation energy (E a) for each polymer individually in the blend after developing a mathematical expression based on an integral solution, which was related to both polymer fractions and their blending characteristics in the form of kinetic parameters. The unique approach presented in this study showed that the apparent activation energy of PET (E a1) in the blend (240e270 kJ/mol) is always higher than PMMA's apparent activation energy (E a2 , 140e170 kJ/mol), which is attributed to the degradation mechanism of the blend and the latter being of a lower melting point hence degrading faster. It was also observed that the activation energy of both polymers increased with PET composition and decreased with higher heating rates, which can be attributed to PET acting as an inhibitor to PMMA in the blends.