Crystallization Behavior Of Biodegradable Poly Research Articles

Crystallization behavior of biodegradable poly(L-lactic acid) (PLLA)/poly(butylene succinate) (PBS) blends based on in situ simultaneous wide-angle x-ray diffraction/small-angle x-ray scattering techniques and thermal analyses

Crystallization behavior of biodegradable poly(L-lactic acid) (PLLA)/poly(butylene succinate) (PBS) blends based on in situ simultaneous wide-angle x-ray diffraction/small-angle x-ray scattering techniques and thermal analyses

Crystallization behavior of biodegradable poly(ethylene adipate) modulated by a benign nucleating agent: Zinc phenylphosphonate

Zinc phenylphosphonate (PPZn), a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly(ethylene adipate) (PEA) to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA. Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly. Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn. In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly. It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA. The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.

The crystallization behavior of biodegradable poly(butylene succinate) in the presence of organically modified clay with a wide range of loadings

The crystallization behavior of poly(butylene succinate) (PBS) nanocomposites with a wide range of contents of clays was revealed. It was of interest to find that the crystallization rate of PBS was accelerated obviously at relatively low contents of clays; while a retarded crystallization kinetics and a decreased crystallinity of PBS were found in the nanocomposites with higher clay contents. Two interplaying effects existed in the nanocomposites, i.e., a suppression effect of clays on nucleation and a templating effect of clays on crystal growth, were clarified to contribute to this intriguing crystallization behavior.

Unusual crystallization behavior of biodegradable poly(ethylene adipate) based nanocomposites induced by graphene oxide

GO increases both the nucleation density and the growth rate of PEA spherulites in nanocomposites.

Effect of sepiolite on the crystallization behavior of biodegradable poly(lactic acid) as an efficient nucleating agent

To enhance the crystallization kinetics of poly(lactic acid) (PLA), fibrous sepiolite was explored for nucleating the crystallization of PLA. PLA/sepiolite nanocomposites were prepared via the melt‐extrusion method. The effect of sepiolite on the crystallization behavior, spherulite growth and crystal structure of PLA were investigated by means of differential scanning calorimetry (DSC), polarized optical microscope (POM), wide angle X‐ray diffraction (WAXD), Fourier transform infrared (FTIR), and scanning election microscope (SEM). On the basis of DSC and POM results, the overall crystallization kinetics of PLA/sepiolite nanocomposites were significantly enhanced leading to higher crystallinity and nucleation density, faster spherulite growth rate (G) and lower crystallization half‐time (t1/2) compared with the neat PLA. Under non‐isothermal conditions, the PLA blend comprising 1.0 wt% of sepiolite still revealed two crystallization peaks upon cooling at a rate of 35°C/min. Above phenomena strongly suggested that sepiolite was an effective nucleating agent for PLA. FTIR and WAXD analyses confirmed that the crystal structure of PLA matrix was the most common α‐form. SEM micrographics illustrated the fine three‐dimensional spherulite structures with the lath‐shape lamellae regularly arranged in radial directions. POLYM. ENG. SCI., 55:1104–1112, 2015. © 2014 Society of Plastics Engineers

Miscibility and crystallization behavior of biodegradable poly(butylene succinate-co-butylene carbonate) and tannic acid blends

Biodegradable poly(butylene succinate-co-butylene carbonate) (PBSC) and tannic acid (TA) blends were prepared via a solution and casting method in this work. Miscibility and crystallization behavior of PBSC/TA blends were investigated with various techniques. PBSC is miscible with TA as evidenced by both a single composition dependent glass transition temperature and the depression of equilibrium melting point of PBSC in the blends. Relative to neat PBSC, blending with TA does not modify the crystal structure of PBSC in the blends. The nonisothermal melt crystallization of PBSC was retarded by TA in the blends. Both the overall isothermal melt crystallization rates and spherulitic growth rates of PBSC/TA blends show the similar variation trends, which become slower with increasing crystallization temperature and the TA composition. The crystallization mechanism of PBSC does not change, regardless of crystallization temperature and the TA composition in the blends.

Nucleation effects of α-cyclodextrin inclusion complexes on the crystallization behavior of biodegradable poly(1,4-butylene adipate)

This study examined the polymorphic crystallization behavior of poly(1,4-butylene adipate) (PBA) with the addition of nucleation agents such as the α-cyclodextrin (α-CD) inclusion complex (IC) of PBA (PBAIC) and the IC of poly(e-caprolactone) (PCLIC). The formation of PBAIC and PCLIC was characterized by 1H NMR, Fourier-transform infrared (FT-IR) spectroscopy and wide-angle X-ray diffraction (WAXD). The differential scanning calorimetry (DSC) and WAXD results suggest that some of the PBA segments remained outside the α-CD cavities even after the formation of ICs with α-CD. WAXD investigation also confirmed that the ICs had a channel structure. The DSC and polarized optical microscopy (POM) results showed the ICs to exhibit nucleation effects on the crystallization and polymorphic behavior of the PBA. The cooling rate played a significant role in the polymorphic crystallization behavior of the pure PBA. Thus, when the cooling rate was decreased, the crystal structures changed from β to α-form and vice versa. The blending of a nucleating agent with the PBA led to higher crystallization temperatures, thus favoring the nucleation of the α-form crystal of PBA rather than pure PBA. The nucleating activity of the PCLIC during the crystallization of the PBA was higher than that of PBAIC.

Effect of Low Multi-Walled Carbon Nanotubes Loading on the Crystallization Behavior of Biodegradable Poly(Butylene Adipate)

The effect of low carboxyl-functionalized multi-walled carbon nanotubes (f-MWCNTs) loading on the crystallization behavior of biodegradable poly(butylene adipate) (PBA) was studied with various techniques in this work. For the nonisothermal melt crystallization, f-MWCNTs accelerate the crystallization process of PBA apparently due to the heterogeneous nucleation effect. The Ozawa method fails to describe the nonisothermal crystallization process of neat PBA and its nanocomposite. Isothermal melt crystallization kinetics of neat PBA and its nanocomposite was analyzed by the Avrami equation. The overall isothermal crystallization rate of neat PBA and its nanocomposite increases with increasing crystallization temperature. The addition of f-MWCNTs accelerates the isothermal crystallization of PBA as compared with that of neat PBA at a given crystallization temperature, indicative of the nucleating agent effect of f-MWCNTs; however, the crystallization mechanism does not change. The crystal structure of PBA remains unchanged in the PBA/f-MWCNTs nanocomposite despite the presence of f-MWCNTs.

Miscibility and crystallization behavior of biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/phenolic blends

AbstractPoly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/phenolic blends are new miscible crystalline/amorphous polymer blends prepared via solution casting method in this work, as evidenced by the single composition dependent glass transition temperature. The measured Tgs can be well fitted by the Kwei equation with a q value of 13.6 for the PHBV/phenolic blends, indicating that the interaction between the two components is strong. The negative polymer–polymer interaction parameter, obtained from the melting depression of PHBV using the Nishi‐Wang equation, indicating the thermal miscibility of PHBV and phenolic. The spherulitic morphology and crystal structure of PHBV/phenolic blends were studied with polar optical microscopy and wide angle X‐ray diffraction compared with those of neat PHBV. It is found that the growth rates of PHBV in the blends are lower than that in neat PHBV at a given crystallization temperature, and the crystal structure of PHBV is not modified by the presence of phenolic in the PHBV/phenolic blends, but the crystallinity decrease with the increasing of phenolic. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Crystallization behavior of biodegradable poly(L‐lactic acid) filled with a powerful nucleating agent: N,N′‐bis(benzoyl) suberic acid dihydrazide

AbstractN,N′‐Bis(benzoyl) suberic acid dihydrazide (NA) as nucleating agent for poly(L‐lactic acid) (PLLA) was synthesized from benzoyl hydrazine and suberoyl chloride, which was deprived from suberic acid via acylation. PLLA/NA samples were prepared by melt blending and a hot‐press forming process. The nonisothermal and isothermal crystallization, spherulite morphology, and melting behavior of PLLA/NA with different contents of NA were investigated with differential scanning calorimetry, depolarized‐light intensity measurement, scanning electron microscopy, polarized optical microscopy, and wide‐angle X‐ray diffraction. With the incorporation of NA, the crystallization peak became sharper and shifted to a higher temperature as the degree of supercooling decreased at a cooling rate of 1°C/min from the melt. Nonisothermal crystallization indicated that the presence of NA accelerated the overall PLLA crystallization. In isothermal crystallization from the melt, the presence of NA affected the isothermal crystalline behaviors of PLLA remarkably. The addition of NA led to a shorter crystallization time and a faster overall crystallization rate; this meant that there was a heterogeneous nucleation effect of NA on the crystallization of PLLA. With the addition of 0.8% NA, the crystallization half‐time of PLLA/NA decreased from 26.5 to 1.4 min at 115°C. The Avrami theory was used to describe the kinetics of isothermal crystallization of the PLLA/NA samples. Also, with the presence of NA, the spherulite number of PLLA increased, and the spherulite size decreased significantly. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Crystallization kinetics and morphology of biodegradable poly(butylene succinate‐co‐propylene succinate)s

AbstractThe crystallization behavior of biodegradable poly(butylene succinate) and copolyesters poly(butylene succinate‐co‐propylene succinate)s (PBSPS) was investigated by using 1H NMR, DSC and POM, respectively. Isothermal crystallization kinetics of the polyesters has been analyzed by the Avrami equation. The 2.2‐2.8 range of Avrami exponential n indicated that the crystallization mechanism was a heterogeneous nucleation with spherical growth geometry in the crystallization process of polyesters. Multiple melting peaks were observed during heating process after isothermal crystallization, and it could be explained by the melting and recrystallization model. PBSPS was identified to have the same crystal structure with that of PBS by using wide‐angle X‐ray diffraction (WAXD), suggesting that only BS unit crystallized while the PS unit was in an amorphous state. The crystal structure of polyesters was not affected by the crystallization temperatures, too. Besides the normal extinction crosses under the POM, the double‐banded extinction patterns with periodic distance along the radial direction were also observed in the spherulites of PBS and PBSPS. The morphology of spherulites strongly depended on the crystallization temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 420–428, 2007

Miscibility and Crystallization Behavior of Poly(butylene succinate) and Poly(vinylidene fluoride) Blends

Miscibility and crystallization behavior of biodegradable poly(butylene succinate) (PBSU) and poly(vinylidene fluoride) (PVDF) blends, where two components are crystallizable have been investigated by differential scanning calorimerty and optical microscopy. From cloud point observation of the blends they are found to have lower critical solution temperature behavior. Spherulites of PVDF grew linearly with crystallization time and the growth rate decreased with increase in PBSU content. The interaction parameter χ12, obtained from melting point depression of PVDF gave the value of −0.139. However, the crystallization and melting behavior of low-Tm component PBSU were quite different from that of high-Tm component PVDF: (i) the magnitude of the melting point depression of PBSU was changed strongly with cooling rate, (ii) for a given Tc, the melting point of PBSU increased with increase in PVDF content, in contrast to the decrease of the melting point in usual amorphous/crystalline blends, (iii) the spherulitic growth rate G of PBSU decreased very slightly with increase in PVDF content at a given Tc and the morphology of the PBSU were strongly dependent upon the crystallization condition. Microscopic observations and Avrami analysis of the crystallization of PBSU in the blends lead to the conclusion that all these unique crystallization behaviors of PBSU presented in this article are ascribed to the presence of PVDF crystals at the temperature where the crystallization of PBSU occurs.