Poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/clay nanocomposites are prepared via simple melt blending method at PDLA loadings from 5 to 20 wt%. Formation of the stereocomplex crystals in the nanocomposites is confirmed by differential scanning calorimetry and wide-angle X-ray diffraction (WAXD). The internal structure of the nanocomposites has been established by using WAXD and transmission electron microscope analyses. The dispersion of clay in the PLLA/PDLA/clay nanocomposites can be improved as a result of increased intensity of shear during melt blending. The overall crystallization rates are faster in the PLLA/PDLA/clay nanocomposites than in PLLA/clay nanocomposite and increase with an increase in the PDLA loading up to 10 wt%; however, the crystallization mechanism and crystal structure of these nanocomposites remain unchanged despite the presence of PDLA. The storage modulus has been apparently improved in the PLLA/PDLA/clay nanocomposites with respect to PLLA/clay nanocomposite. Moreover, it is found that the hydrolytic degradation rates have been enhanced obviously in the PLLA/PDLA/clay nanocomposites than in PLLA/clay nanocomposite. POLYM. ENG. SCI., 54:914–924, 2014. © 2013 Society of Plastics Engineers

Biodegradable poly(ε-caprolactone) (PCL)/silica nanocomposites containing 1–9 wt% silica nanoparticles were prepared by melt compounding in this work. The rheology, mechanical properties, and biodegradation were investigated. PCL/silica nanocomposite shows a high percolation threshold, which is between 7 and 9 wt%. Once percolation network structure forms, the long-range motion of PCL chains is highly restrained. From the results of mechanical tests, the tensile strength, modulus, and yield strength of the nanocomposites are enhanced by the incorporation of silica nanoparticles. Moreover, it is interesting to find that the biodegradation rates have been enhanced obviously in the PCL/silica nanocomposites than in neat PCL, which may be of great use for the practical application of PCL. POLYM. COMPOS., 34:1620–1628, 2013. © 2013 Society of Plastics Engineers

Biodegradable poly(ε-caprolactone) (PCL)/silica nanocomposites at various silica loadings were prepared via direct melt compounding method in this work. Scanning electron microscopy observation indicated that when the silica content was < 3 wt%, the nanoparticles dispersed evenly in the PCL matrix and exhibited only aggregates with particle size of less than 100 nm. The results of nonisothermal melt crystallization showed that the crystallization peak temperature was higher in the nanocomposites than in neat PCL; moreover, the overall crystallization rate was faster in the nanocomposites than in neat PCL during isothermal melt crystallization. Both nonisothermal and isothermal melt crystallization studies suggested that the crystallization of PCL was enhanced by the presence of silica and influenced by the silica loading. The effect of silica on the crystallization behavior was twofold: the presence of silica may provide heterogeneous nucleation sites for the PCL crystallization while the aggregates of silica may restrict crystal growth of PCL. However, the crystal structure of PCL remained almost unchanged despite the presence of silica in the nanocomposites. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers

Biodegradable stereocomplex-type poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA)/multiwalled carbon nanotubes (MWCNTs) nanocomposites are prepared via simple melt blending method at PDLA loadings from 5 to 20 wt %. Formation of the stereocomplex crystals in the nanocomposites is confirmed by the phase transition in the differential scanning calorimetric profiles. Field emission scanning electron microscopy observation indicates that MWCNTs are nicely dispersed in the PLLA/PDLA/MWCNTs ternary blends with 20 wt % PDLA loading due to the increased shear stress in the melt-compounding with presence of PDLA. The overall crystallization rates are faster in the PLLA/PDLA/MWCNTs nanocomposites than in PLLA/MWCNTs nanocomposite; however, the crystallization mechanism and crystal structure of these nanocomposites remain unchanged despite the presence of PDLA. The storage modulus above glass transition temperature has been apparently improved in the PLLA/PDLA/MWCNTs nanocomposites with respect to PLLA/MWCNTs nanocomposite. It is interesting to find that the hydrolytic degradation rates have been enhanced obviously in the PLLA/PDLA/MWCNTs nanocomposites than in PLLA/MWCNTs nanocomposite, which may be of great use and importance for the wider practical application of PLLA/MWCNTs nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3919–3929, 2013

Nano-sized calcium carbonate (nano-CaCO₃)-supported nucleating agent for poly(L-lactide) (PLLA) was prepared by supporting calcium phenylphosphonate (PPCa) on nano-CaCO₃ surface. The thermal properties of phenylphosphonic acid (PPOA) and nano-CaCO₃-supported nucleating agent and its dispersion in PLLA matrix were investigated by differential scanning calorimetry and field emission scanning electron microscopy. The results indicated that the formation of nucleating agent supported on nano-CaCO₃ was attributed to the chemical reaction between nano-CaCO₃ and PPOA. The nano-CaCO₃-supported nucleating agents were dispersed evenly in the PLLA matrix even with 5 wt% loading. The supported nucleating agent was added to PLLA to examine its nucleating ability for PLLA. The results of the investigation showed that the nano-CaCO₃-supported nucleating agent exhibited higher nucleation ability compared to PPCa nucleating agent. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Poly(L-lactide) (PLLA) was prepared via melt blending and nucleated using three layered metal phosphonates, i.e. zinc phenylphosphonate (PPZn), calcium phenylphosphonate (PPCa) and barium phenylphosphonate (PPBa). The morphology, crystallization and enzymatic hydrolysis of PLLA nucleated using PPZn, PPCa and PPBa were investigated. The results of both wide-angle X-ray diffraction and transmission electron microscopy observations show that the layers of PPZn, PPCa or PPBa are barely exfoliated or intercalated by PLLA chains in the melt-blending process. PPZn, PPCa and PPBa serve as effective nucleating agents, accelerating both non-isothermal and isothermal crystallization and enzymatic hydrolysis of PLLA. An interesting aspect is that the nucleating ability of PLLA incorporating PPZn, PPCa and PPBa decreases in the order PPZn > PPCa > PPBa, whereas the enzymatic hydrolysis of PLLA incorporating PPZn, PPCa and PPBa decreases in the reverse order, which is due to the different dispersion and interfacial interactions of PPZn, PPCa and PPBa throughout the PLLA matrix. Copyright © 2010 Society of Chemical Industry

The performance and radiation-induced cross-linking of polycaprolactone (PCL) in the presence of vinyltrimethoxysilane (VTMS) have been investigated. Radiation-induced cross-linking of PCL in the presence of VTMS followed the Charlesby–Pinner equation, and VTMS promoted the radiation-induced cross-linking of PCL. As the concentration of VTMS increased, the gelation dose and the ratio of degradation to cross-linking (p₀/q₀) decreased and the efficiency of radiation-induced cross-linking increased. Differential scanning calorimetry analyses showed differences between the first and second scans. Glass-transition temperature (T_g) and mechanical properties of the polymers increased. Radiation-induced cross-linking of PCL in the presence of VTMS was found to retard hydrolytic degradation greatly. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Silica nanoparticles and poly(butylene succinate) (PBS) nanocomposites were prepared by a melt-blending process. The influence of silica nanoparticles on the nonisothermal crystallization behavior, crystal structure, and mechanical properties of the PBS/silica nanocomposites was investigated. The crystallization peak temperature of the PBS/silica nanocomposites was higher than that of neat PBS at various cooling rates. The half-time of crystallization decreased with increasing silica loading; this indicated the nucleating role of silica nanoparticles. The nonisothermal crystallization data were analyzed by the Ozawa, Avrami, and Mo methods. The validity of kinetics models on the nonisothermal crystallization process of the PBS/silica nanocomposites is discussed. The approach developed by Mo successfully described the nonisothermal crystallization process of the PBS and its nanocomposites. A study of the nucleation activity revealed that the silica nanoparticles had a good nucleation effect on PBS. The crystallization activation energy calculated by Kissinger's method increased with increasing silica content. The modulus and yield strength were enhanced with the addition of silica nanoparticles into the PBS matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A silane-grafting water-crosslinking approach was developed to crosslink poly(L-lactide) (PLLA) by grafting vinylalkoxysilane onto PLLA using dicumyl peroxide, followed by silane hydrolysis to form siloxane linkages between PLLA chains. The degree of silane grafting onto PLLA was qualitatively characterized using Fourier transform infrared spectroscopy and quantitatively determined using inductively coupled plasma mass spectrometry. Crosslinked PLLA films were obtained by curing of silane-grafted PLLA in hot water. Gel fractions were evaluated in order to calculate the crosslinking reaction kinetics and crosslinking density. Various techniques were used to investigate the effect of silane water-crosslinking on the thermomechanical properties, hydrolysis resistance and biodegradation of PLLA. In addition to an improvement in thermal stability and mechanical properties, hydrolysis resistance was significantly enhanced as a result of silane water-crosslinking of PLLA. Moreover, the biodegradation of silane water-crosslinked PLLA was retarded compared with neat PLLA. Copyright © 2010 Society of Chemical Industry

BACKGROUND: Poly(butylene adipate-co-terephthalate) (PBAT) has attracted wide interest as a biodegradable polymer. However, its use is restricted in certain applications due to its low melting point.

RESULTS: PBAT was treated using γ-radiation. The radiation features were analyzed using Soxhlet extraction, and the ratio of chain scission and crosslinking and gelation dose were determined using the classical Charlesby–Pinner equation. The results showed that PBAT is a radiation-crosslinkable polymer. The degree of crosslinking increased with increasing radiation dose; the relation between sol fraction and dose followed the Charlesby–Pinner equation. Differential scanning calorimetry analyses showed that the melting temperature (T_m) and the heat of fusion (ΔH_m) of PBAT exhibited almost no change in the first scan. The second scan, however, showed a decrease in T_m and ΔH_m. The glass transition temperature of irradiated PBAT increased with increasing radiation dose. The weight loss of control and irradiated PBAT resulting from thermal degradation was a one-step process. Moreover, the tensile strength and elongation at break decreased with an increase in radiation dose. However, the Young's modulus and stress at yield were not greatly affected by γ-radiation.

CONCLUSION: PBAT can be crosslinked using γ-radiation. The crosslinking efficiency is relatively low. The thermal and mechanical properties of PBAT are affected by γ-radiation. Copyright © 2009 Society of Chemical Industry