Thermal and dynamic mechanical properties of binary blends of bacterial copolyester poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) with poly(2-hydroxyethylmethacrylate) (PHEMA) (original) (raw)
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Macromolecular Symposia, 2019
The aim of this study is to investigate the influence of vinyl acetate (VA) content on the thermal and rheological properties of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/poly(ethylene-co-vinyl acetate) (EVA) blends. Binary blends of PHBV and EVA containing 65 wt% (EVA65) and 90 wt% (EVA90) VA were prepared by torque rheometry and their thermal properties were studied by differential scanning calorimetry (DSC). Rheograms of PHBV/EVA65 containing up to 40 wt% EVA showed that the torque values decrease as a function of mixing time due to the thermo-mechanical degradation, which preferentially for PHBV is chain scission. The increase in the EVA65 concentration results in torque stability probably due to the balance between chain scission of the PHBV and chain branching of the EVA65. For PHBV/EVA90 blends, the torque values are stable indicating that the presence of EVA90 decreases the degradation process of the PHBV and hence increases the thermal stability of blends. DSC curves showed that the PHBV cold crystallization temperature (T cc) increased and cold crystallization (ΔH cc) and melting enthalpies (ΔH m) decreased with the increase in the EVA content, independently of VA content and blend morphology. DSC curves of PHBV/EVA65 showed two glass transition temperatures and clear phase separations, in all studied formulations, typical of immiscible systems. In contrast to it, PHBV/EVA90 blends showed a single glass transition, suggesting total miscibility. Both findings were corroborated by scanning electron microscopy (SEM) analysis.
Crystallization and thermal behaviour of poly (d(−) 3-hydroxybutyrate)/poly(epichlorohydrin) blends
Polymer, 1993
The influence of molecular structure and characteristics of an uncrystallized rubbery second component (ethylene-propylene rubber (EPR) and poly(vinyl acetate) (PVAc)) on the melt miscibility, phase structure, morphology, thermal and crystallization behaviour of blends based on poly(D(-)-3-hydroxybutyrate) (PHB) has been investigated by differential scanning calorimetry and optical microscopy. PHB and EPR are immiscible in the melt, whereas PHB and PVAc are compatible. Consequently PHB-PVAc blends show a single glass transition and a drastic depression of equilibrium melting temperature of PHB. Conflicting results are obtained when the Flory-Huggins and Kwei-Frisch equations are used to describe and analyse this melting-point depression. In PHB-EPR blends no change in the radial growth rate G of PHB spherulites occurs with increasing EPR content. The PHB spherulites grow in the presence of a PHB melt containing EPR domains as the dispersed phase. During growth the EPR particles are first ejected and then occluded in intraspherulitic regions. In the case of PHB-PVAc blends, at a given To, G decreases with increasing PVAc content. PHB spherulites grow in equilibrium with a one-phase melt. The phase structure in the solid state is characterized by the presence of a homogeneous amorphous phase situated mainly in interlamellar regions of crystalline PHB and consisting of PVAc molecules and uncrystallized PHB chains.
Miscibility and Crystallization of Poly(β-hydroxybutyrate) and Poly(p-vinylphenol) Blends
Macromolecules
The miscibility and crystallization behavior of poly(-hydroxybutyrate) (PHB) and poly(pvinylphenol) (PVPh) blends were studied by differential scanning calorimetry and optical microscopy (OM). The blends exhibit a single composition-dependent glass transition temperature, characteristic of miscible systems. A depression of the equilibrium melting temperature of PHB is observed. The interaction parameter values obtained from analysis of the melting point depression are of large negative values, which suggests that PHB and PVPh blends are thermodynamically miscible in the melt. Isothermal crystallization kinetics in the miscible blend system PHB/PVPh was examined by OM. The presence of the amorphous PVPh component results in a reduction in the rate of spherulite growth of PHB. The spherulite growth rate is analyzed using the Lauritzen-Hoffman model. The isothermally crystallized blends of PHB/PVPh were examined by wide-angle X-ray diffraction and small-angle X-ray scattering (SAXS). The long period obtained from SAXS increases with the increase in PVPh component, which implies that the amorphous PVPh is squeezed into the interlamallar region of PHB.
Thermochimica Acta, 2006
With the objective of developing new biodegradable materials, the miscibility and the crystallinity of blends of poly(3-hydroxybutyrate), P(3HB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-co-3HV), have been studied. P(3HB) (300 kg mol −1 )/P(3HB-co-3HV)-10% 3HV (340 kg mol −1 ) blends were prepared by casting in a wide range of proportions, and characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The experimental values for the glass transition temperatures (T g ) are in good agreement with the values provided by the Fox equation, showing that the blends are miscible. It was observed that the T g and the melting temperature (T m ) decreases with the increase in the P(3HB-co-3HV)-10% 3HV content, while the crystallization temperature (T c ) increases. FT-IR analyses confirmed the decrease on the crystallinity of P(3HB)/P(3HB-co-3HV)-10% 3HV blends with higher copolymer contents. Bands related to the crystallinity were changed, due to the copolymer content that produced miscible and less crystalline blends.
Polymer Testing, 2013
The paper aims to study blend properties of biodegradable polymers of poly(3hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) prepared by melt mixing. Blend compositions based on PHBV/PLA were investigated according to the following weight ratios, i.e. 100/0, 75/25, 50/50, 25/75 and 0/100 wt%. The study showed through scanning electron microscopy (SEM) that blends of PHBV/PLA are not miscible. This is consistent with differential scanning calorimetry (DSC) data which indicate the presence of two distinct glass transition temperatures (T g ) and melting temperatures (T m ), attributed to the neat polymers, over all the range of blend compositions. Water and oxygen barrier properties of PHBV/PLA blends are significantly improved with increasing the PHBV content in the blend. Further, morphological analyzes indicated that increasing the PHBV content in the polymer blends results in increasing the PLA crystallinity due to the finely dispersed PHBV crystals acting as a filler and a nucleating agent for PLA. On the other hand, the addition of PLA to the blend results in a very impressive increase in the complex viscosity of PHBV. Moreover, the rheological data showed that, excluding the specific behavior of the neat polymers at low frequencies, i.e. less than 0.1 Hz, the complex viscosity of PHBV/PLA blends fits the mixing law well.
Phase behavior of PCBM blends with different conjugated polymers
Physical Chemistry Chemical Physics, 2011
In this work the phase behavior of [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) blends with different poly(phenylene vinylene) (PPV) samples is investigated by means of standard and modulated temperature differential scanning calorimetry (DSC and MTDSC) and rapid heat-cool calorimetry (RHC). The PPV conjugated polymers include poly(2-methoxy-5-(3 0 ,7 0dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV), High T g -PPV which is a copolymer, and poly((2-methoxy-5-phenethoxy)-1,4-phenylene vinylene) (MPE-PPV). Comparisons of these PPV:PCBM blends with regioregular poly(3-hexyl thiophene) (P3HT):PCBM blends are made to see the different component miscibilities among different blends. The occurrence of liquid-liquid phase separation in the molten state of MDMO-PPV:PCBM and High T g -PPV:PCBM blends is indicated by the coexistence of double glass transitions for blends with a PCBM weight fraction of around 80 wt%. This is in contrast to the P3HT:PCBM blends where no phase separation is observed. Due to its high cooling rate (about 2000 K min À1 ), RHC proves to be a useful tool to investigate the phase separation in PPV:PCBM blends through the glass transition of these crystallizable blends. P3HT is found to have much higher thermal stability than the PPV samples.
Macromolecules, 2005
ABSTRACT The present study is aimed at investigating structure, dispersibility, and crystallinity of poly(3-hydroxybutyrate) (PHB) and poly(l-lactic acid) (PLLA) blends by using FT-IR microspectroscopy and differential scanning calorimetry (DSC). Four kinds of PHB/PLLA blends with a PLLA content of 20, 40, 60, and 80 wt % were prepared from chloroform solutions. Micro-IR spectra obtained at different positions of a PHB film are all very similar to each other, suggesting that there is no discernible segregated amorphous and crystalline parts on the PHB film at the resolution scale of micro-IR spectroscopy. On the other hand, the micro-IR spectra of two different positions of a PLLA film, where spherulite structures are observed and they are not observed, are significantly different from each other. PHB and PLLA have characteristic IR marker bands for their crystalline and amorphous components. Therefore, it is possible to explore the structure of each component in the PHB/PLLA blends by using micro-IR spectroscopy. The IR spectra of a position of blends except for the 20/80 blend are similar to that of pure PHB. On the other hand, the IR spectra of another position of the blend consist of the overlap of those of pure PHB and PLLA. For the 20/80 blend, it is difficult to find a position whose spectrum is similar to that of pure PHB. However, a crystalline peak due to the CO stretching band is observed at 1718 cm-1. This means that PHB crystallizes as very small spherulites or immature spherulites under such blend ratio. DSC curves of the blend show that the heat of crystallization of PHB varies with the blending ratio of PHB and PLLA. The recrystallization peak is detected for PLLA and the 20/80 blend respectively at 106.5 and 88.2 °C. The lowering of recrystallization temperature for the 20/80 blend compared with that of pure PLLA suggests that PHB forms small finely dispersed crystals that may act as nucleation sites of PLLA. The results for the PHB/PLLA blends obtained from IR microspectroscopy indicate that PHB crystallizes in any blends. However, crystalline structures of PHB in the 80/20, 60/40, and 40/60 blends are different from those of the 20/80 blend.
e-Polymers, 2011
A series of ethylene vinyl acetate random copolymer EVA, with vinyl acetate (VA) varied from 9 to 91m%, was investigated by differential scanning calorimetry DSC and polarized optical microscopy. Biodegradable polymer blends of polyhydroxybutyrate PHB and EVA, having VA in EVA in range from 40m% till 91m%, were prepared by film casting from a chloroform solution. The miscibility and crystallization behavior of these blends were investigated. The isothermal crystallization behaviors of PHB and PHB/EVA blends are discussed in terms of the half time of crystallization t 1/2 . Experimental results indicated that blends of PHB/ EVA91 are completely miscible blend in the entire (0 to 100 m%) compositional ranges. Blends PHB/ EVA, for VA varied from 40 till 70 m% are immiscible as evidenced by the existence of unchanged composition independent glass transition temperatures (T g ), crystallization and melting behavior. The isothermal crystallization of PHB blends was investigated from room temperature till 130 °C. 80 °C was found to be the best temperature for comparison of different blends. At 80 °C t 1/2 strongly depends on the content of VA in PHB/EVA blend, mainly due to differences in miscibility as well as due to differences in segmental mobility as identified by differences in glass transition temperature. Since both components in PHB/EVA80, pure PHB and pure EVA80, have glass transition temperatures close to 0 °C, it is difficult to decide its miscibility from T g . However from the strong dependence of the value of crystallization half time t 1/2 of PHB/EVA80 on blend composition, it was possible to reasonably infer that PHB/EVA80 is partially miscible.
European Polymer Journal, 2006
Intermolecular hydrogen bonds, miscibility, crystallization and thermal stability of the blends of biodegradable poly(3hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-3HHx)] with 4,4-dihydroxydiphenylpropane (DOH 2 ) were investigated by FTIR, 13 C solid state NMR, DSC, WAXD and TGA. Intermolecular hydrogen bonds were found in both blend systems, which resulted from the carbonyl groups in the amorphous phase of both polyesters and the hydroxyl groups of DOH 2 . The intermolecular interaction between P(3HB-3HHx) and DOH 2 is weaker than that between PHB and DOH 2 owing to the steric hindrance of longer 3HHx side chains. Because of the eVect of the hydrogen bonds, the chain mobility of both PHB and P(3HB-3HHx) components was limited after blending with DOH 2 molecules. Single glass transition temperature depending on the composition was observed in all blends, indicating that those blends were miscible in the melt. The addition of DOH 2 suppressed the crystallization of PHB and P(3HB-3HHx) components. Moreover, the crystallinity of PHB and P(3HB-3HHx) components also decreased with increasing DOH 2 content in the blends. However, the crystal structures of the crystallizable components were not aVected. The existence of DOH 2 favors to thermal decomposition of PHB and P(3HB-3HHx) components, resulting in the decrease in thermal decomposition temperature.