PCL Blends Research Articles

Oxidation of polycaprolactone to induce compatibility with other degradable polyesters

Chemical modification of poly(ɛ-caprolactone) PCL by oxidation with potassium permanganate in solution was investigated. According to the data obtained from Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance 1H NMR, after the oxidation reactions the PCL chains exhibited new functional groups (vinyl and hydroxyl) and possible intermolecular recombination, producing an oxidized-polycaprolactone (PCL-OX). Solution viscometry indicated that degradation also occurred during the oxidation reactions (∼30% drop in viscosity average molecular weight was detected). Differential scanning calorimetry (DSC) also indicated that PCL was chemically modified and degraded. The successive self-nucleation/annealing (SSA) treatment confirmed that a reduction (or interruption) in linear crystallizable sequences occurred. The immiscibility of blends of PCL with other degradable polyesters, such as poly( p-dioxanone) PPDX (PCL/PPDX 90:10 w/w), was shown by the invariability of the relevant thermal transitions as determined by DSC and FT-IR and NMR analysis. However, the blend prepared with oxidized PCL (PCL-OX/PPDX, in the same composition range) did not display signs of thermodynamic miscibility but showed an interesting thermal behaviour demonstrated by changes in the crystallization temperatures of both phases, and by the melting behaviour of the PCL-OX in the blend. These results together with spectroscopic analysis show that the oxidation of PCL induces physical interactions and/or compatibilisation among the phases of this blend.

Miscibility, melting and crystallization of poly(ε-caprolactone) and poly (vinyl formal) blend

Solution cast blends of poly(e-caprolactone) [PCL] and poly(vinyl formal) [PVF] from dichloromethane was investigated for miscibility by Differential Scanning Calorimetry [DSC], Fourier Transform Infrared Spectroscopy [FTIR] and optical microscopy. Melting (Tm) and crystallization (Tc) temperatures were for the PCL fraction while the glass transition temperature (Tg) was for PVF fraction in the blends. Blends with 20 wt% and less PCL showed a depression in Tm and Tc. Depression in Tc indicated that during the non-isothermal crystallization process, the presence of PVF decreased the PCL segments migrating to the crystallite-melt interface thus reducing the nucleation rate, growth rate and the thickness of the lamella resulting in a depressed Tm. Crystallinity (Xc) decreased gradually with decreasing content of PCL in the blend and was due to the dilution of PCL by PVF. A depressed Tg was observed for 10 wt% PCL blend and remained the same for all other blend compositions. These observations suggested that this blend system has very low degree of miscibility. The degree of miscibility increased at low polyester concentration. FTIR spectra of the blends with low polyester concentrations showed changes in the C=O, O-H and C-O-C regions in the blended PVF and PCL spectra. Optical microscopy showed phase separation in the melt and in the PCL spherulites.

Otrzymywanie, struktura oraz własciwosci uzytkowe nanokompozytow z warstwowych glinokrzemianów i poli(epsilon-kaprolaktonu)

The article is a review of literature concerning the results of past investigations of nanocomposites consisted of poly(e-caprolactone) (PCL) matrix and montmorillonite (MMT) as a filler. The structure (Fig. 1), properties and possibilities of MMT modifications with various amphiphilic compounds were presented. As well the selected PCL properties, especially its biodegradability and compatibility with many other polymers were discussed. Two main methods of preparation of PCL/MMT composites were characterized namely melt blending and in-situ way via polymerization of e-caprolactone in the presence of organophilized MMT (Fig. 2). The selected mechanical properties of micro- and nanocomposites of PCL with different filler contents (Table 1, Fig. 3) as well as of composites with polymer matrix consisted of PCL blend with another polymers (PVC, PP, PE or SAN, Table 2) were discussed. Barrier properties and thermal stability of the composites discussed were also characterized.

Comparison of the biodegradation of poly( ε-caprolactone), cellulose acetate and their blends by the Sturm test and selected cultured fungi

In this work, we compared the biodegradation of poly( ε-caprolactone) (PCL), cellulose acetate (CA) and their blends using an aerobic biodegradation technique known as the Sturm test, and by their carbon dioxide (CO 2) production and susceptibility to attack by a mixture of fungal strains in solid and liquid media in which samples of each blend were the only source of carbon. The extent of biodegradation was assessed by the loss of mass. The polymers were also characterized by thermal analysis using differential scanning calorimetry (DSC). The 40PCL/60CA blend showed faster biodegradation than the other blends because of its higher CO 2 production in aerobic medium (Sturm test). PCL was more susceptible to attack by a mixture of fungi on solid medium than was CA but showed a lower loss of mass (8.4%) than the latter polymer; the 60PCL/40CA blend showed the greatest loss of mass during the period of evaluation. In contrast, in liquid medium, PCL showed a greater loss of mass. Blends of PCL with CA reduced the melting temperature ( T m) of PCL and increased the T m of CA, indicating immiscibilty of the polymers. The blends were also less crystalline, which favoured their biodegradation.

Characterization of biodegradable polymers by inverse gas chromatography. II. Blends of amylopectin and poly(ε‐caprolactone)

AbstractAmylopectin (AP), a potato‐starch‐based polymer with a molecular weight of 6,000,000 g/mol, was blended with poly(ε‐caprolactone) (PCL) and characterized with inverse gas chromatography (IGC), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). Five different compositions of AP–PCL blends ranging from 0 to 100% AP were studied over a wide range of temperatures (80–260°C). Nineteen solutes (solvents) were injected onto five chromatographic columns containing the AP–PCL blends. These solutes probed the dispersive, dipole–dipole, and hydrogen‐bonding interactions, acid–base characteristics, wettability, and water uptake of the AP–PCL blends. Retention diagrams of these solutes in a temperature range of 80–260°C revealed two zones: crystalline and amorphous. The glass‐transition temperature (Tg) and melting temperature (Tm) of the blends were measured with these zones. The two zones were used to calculate the degree of crystallinity of pure AP and its blends below Tm, which ranged from 85% at 104°C to 0% at Tm. IGC complemented the DSC method for obtaining the Tg and Tm values of the pure AP and AP–PCL blends. These values were unexpectedly elevated for the blends over that of pure AP and ranged from 105 to 152°C for Tg and from 166 to 210°C for Tm. The Tm values agreed well with the XRD analysis data. This elevation in the Tg and Tm values may have been due to the change in the heat capacity at Tg and the dependence of Tg on various variables, including the molecular weight and the blend composition. Polymer blend/solvent interaction parameters were measured with a variety of solutes over a wide range of temperatures and determined the solubility of the blends in the solutes. We were also able to determine the blend compatibility over a wide range of temperatures and weight fractions. The polymer–polymer interaction coefficient and interaction energy parameter agreed well on the partial miscibility of the two polymers. The dispersive component of the surface energy of the AP–PCL blends was measured with alkanes and ranged from 16.09 mJ/m2 for pure AP to 38.26 mJ/m2 when AP was mixed with PCL in a 50/50% ratio. This revealed an increase in the surface energy of AP when PCL was added. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3076–3089, 2006

Poly( ε-caprolactone) + unsaturated isophtalic polyester blends: Thermal properties and morphology

Miscibility of blends composed by a linear unsaturated polyester (LUP) with poly( ε-caprolactone) (PCL) of different molecular weights ( M w = 50 × 10 3, 18 × 10 3 and 2 × 10 3) has been studied. The blends were subjected to different thermal treatments and have been studied by FT-IR spectroscopy, differential scanning calorimetry (DSC) and scanning electronic microscopy (ESEM). FT-IR results allow proving the miscibility of the blends at temperatures above the melting temperature of neat PCL. DSC measurements confirm the existence of a crystalline phase corresponding to neat PCL. The crystallization of PCL is observed in a wide range of blends composition, being detected in all the blend compositions when the crystallization time increases. Thermograms show clearly the glass transition temperatures of samples that have been rapidly quenched from the melt. However, the change in the heat flow corresponding to the glass transition temperatures is difficult to detect in samples with high PCL crystallization degree. The analysis of the results indicates that the morphology of the amorphous phase is heterogeneous for LUP + PCL blends and changes depending on the thermal treatment. The ESEM measurements, confirm the heterogeneity of the amorphous phase. The decrease of the molecular weight of the PCL favours the miscibility of the blends.

Characterization of Tissue-Engineered Scaffolds Microfabricated with PAM

PAM (pressure-activated microsyringe) is a new microfabrication technique that allows the fabrication of two- and three-dimensional scaffolds with a well-defined geometry using polymers soluble in volatile solvents. In this study, polymeric scaffolds were realized with four different polymers--PCL, PLLA, PLGA, and a blend of PCL and PLLA--and with three different geometries-square grids, hexagonal grids, and octagonal grids. The scaffolds were characterized in terms of porosity, hydrophilicity, cell adhesion, and their mechanical properties. An analysis of the measured data shows that the physical and mechanical properties of the scaffold depend on its geometry and line width, both of which are easily modulated using PAM.

Thermal and mechanical behavior of injection molded Poly(3-hydroxybutyrate)/Poly(epsilon-caprolactone) blends

Aiming the development of high-performance biodegradable polymer materials, the properties and the processing behavior of poly(3-hydroxybutyrate), P(3HB), and their blends with poly(epsilon-caprolactone), PCL, have been investigated. The P(3HB) sample, obtained from sugarcane, had a molecular weight of 3.0 x 10(5) g.mol¹, a crystallinity degree of 60%, a glass transition temperature (Tg), at - 0.8 °C, and a melting temperature at 171 °C. The molecular weight of PCL was 0.8 x 10(5) g.mol-1. Specimens of 70/30 wt. (%) P(3HB)/PCL blends obtained by injection molding showed tensile strength of 21.9 (± 0.4) MPa, modulus of 2.2 (± 0.3) GPa, and a relatively high elongation at break, 87 (± 20)%. DSC analyses of this blend showed two Tg´s, at - 10.6 °C for the P(3HB) matrix, and at - 62.9 °C for the PCL domains. The significant decrease on the Tg of P(3HB) evidences a partial miscibility of PCL in P(3HB). According to the Fox equation, the new Tg corresponds to a 92/8 wt. (%) P(3HB)/PCL composition.

Diphtheria toxoid loaded poly-(ε-caprolactone) nanoparticles as mucosal vaccine delivery systems

Poly-(ε-caprolactone) (PCL), a poly(lactide-co-glycolide) (PLGA)-PCL blend and co-polymer nanoparticles encapsulating diphtheria toxoid (DT) were investigated for their potential as a mucosal vaccine delivery system. The nanoparticles, prepared using a water-in-oil-in-water (w/o/w) double emulsion solvent evaporation method, demonstrated release profiles which were dependent on the properties of the polymers. An in vitro experiment using Caco-2 cells showed significantly higher uptake of PCL nanoparticles in comparison to polymeric PLGA, the PLGA–PCL blend and co-polymer nanoparticles. The highest uptake mediated by the most hydrophobic nanoparticles using Caco-2 cells was mirrored in the in vivo studies following nasal administration. PCL nanoparticles induced DT serum specific IgG antibody responses significantly higher than PLGA. A significant positive correlation between hydrophobicity of the nanoparticles and the immune response was observed following intramuscular administration. The positive correlation between hydrophobicity of the nanoparticles and serum DT specific IgG antibody response was also observed after intranasal administration of the nanoparticles. The cytokine assays showed that the serum IgG antibody response induced is different according to the route of administration, indicated by the differential levels of IL-6 and IFN-γ. The nanoparticles eliciting the highest IgG antibody response did not necessarily elicit the highest levels of the cytokines IL-6 and IFN-γ.

Effect of Additive on Fracture Properties of PLA/PCL Polymer Blend

LTI was added to blends of PLA and PCL to improve the immiscibility of the two different kinds of biodegradable polymers. Fracture properties of PLA/PCL and PLA/PCL +LTI were evaluated and compared to assess the effect of LTI additive on the fracture behavior. Both the J-integral at initiation, Jin, and the total fracture energy, Jf, were improved effectively due to LTI addition. Fracture surfaces were also examined using SEM to characterize fracture mechanism. It was confirmed that the size of PCL spherulites became smaller by adding LTI, and therefore void formation was inhibited, resulting in the improvement of the fracture properties.

ＰＬＡ／ＰＣＬポリマーブレンドの相構造制御と破壊特性

Phase morphology of blends of biodegradable polymers, PLA and PCL, was controlled by introducing an additive, LTI, to improve the mechanical properties of the mixture. Fracture properties such as the J-integral at initiation Jin, and the total fracture energy Jf, of PLA/PCL blends with different LTI contents were evaluated, and were compared to assess the effect of LTI content on these properties. Both Jin and Jf values were dramatically improved by LTI addition. Fracture surfaces were also examined using SEM to characterize the effect of LTI addition on the fracture mechanism. It was confirmed that the size of PCL spherulites became smaller due to the activation of LTI as a surface-active agent. As a result, void formation was inhibited, and plastic deformation to be larger, resulting the improvement of fracture properties.

Studying the miscibility and thermal behavior of polybenzoxazine/poly(ε-caprolactone) blends using DSC, DMA, and solid state 13C NMR spectroscopy

Polymer blends of polybenzoxazine (PBZ) and poly(ε-caprolactone) (PCL) were prepared by solution blending of PCL and benzoxazine monomer (B-m), followed by thermal curing of B-m. The miscibility and thermal behavior of these PBZ/PCL blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), and solid state 13C nuclear magnetic resonance (NMR) spectroscopy. The FTIR spectra indicated that hydrogen bonding interactions occur between the carbonyl groups of PCL and the hydroxyl groups of PBZ upon curing. The DSC results revealed that this PBZ/PCL blend system has a single glass transition temperature over the entire range of compositions that we investigated. The DMA results indicated that the values of Tg of the PBZ/PCL blends were higher than those of the pure polymers. In addition, at higher PCL concentrations we observed two glass transitions for the PBZ/PCL blends: One, for the PCL component, occurred in the low-temperature region and the other, for the PBZ component, in the high-temperature region; this finding indicates that PCL and PBZ are partially miscible in the amorphous phase. The most pronounced effect of the addition of PCL was to broaden the glass transition region, judging from the E″ peaks and the decrease in the value of the loss tangent (tanδ) in the transition region upon increasing the PCL content. We have also studied the 1H spin-lattice relaxation times in the laboratory frame, T1H, and in the rotating frame, T1ρH, as a function of the blend composition. The T1H results are in good agreement with those from the DSC analysis; i.e. the blends are completely homogeneous on the scale of 40–70nm. The values of T1ρH indicate that the PCL present in the blends exists in both crystalline and amorphous phases; the mobility difference between these PCL phases is clearly visible from the T1ρH data. In addition, the amorphous phase of PCL is not miscible with PBZ; i.e. it is larger than 2–4nm.

Effect of Vitamin E TPGS on immune response to nasally delivered diphtheria toxoid loaded poly(caprolactone) microparticles

The nasal mucosa has many advantages as a potential site for drug and vaccine delivery. The present study has sought to exploit this route of delivery using microparticles composed of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) as a matrix material blended with poly(caprolactone) for nasal immunisation with diphtheria toxoid. Particles were prepared by a double emulsion method, followed by spray drying and the effect of TPGS on size, zeta potential, loading and release of antigen was assessed. Particles composed of TPGS–PCL blends were spherical, smooth and monodisperse, displaying increasing yields after spray drying with increasing concentrations of TPGS. The immune response to diphtheria toxoid loaded PCL-TPGS microspheres after nasal administration was shown to be higher than that achieved using PCL microspheres alone. We conclude that TPGS shows significant potential as a novel adjuvant either alone or in combination with an appropriate delivery system.

Miscibility Behavior and Interaction Mechanism of Polymer Electrolytes Comprising LiClO4 and MPEG-block-PCL Copolymers

We have used DSC, FTIR spectroscopy, and ac impedance techniques to investigate in detail the miscibility behavior, interaction mechanism, and ionic conductivity of polymer electrolytes composed of lithium perchlorate (LiClO4) and monomethoxypoly(ethylene glycol)-block-poly(e-caprolactone) (MPEG−PCL) diblock copolymer. The existence of the PCL phase in the MPEG−PCL block copolymer tends to retard the crystallinity of MPEG and results in a higher ionic conductivity for the LiClO4/MPEG−PCL based polymer electrolyte. DSC analyses indicate that the phase separation occurs for some compositions of the LiClO4/MPEG−PCL blends. In addition, FTIR spectroscopy studies reveal the complicated interactions that occur within the LiClO4/MPEG−PCL blend system upon varying the LiClO4 content and increasing the temperature. For the LiClO4/MPEG−PCL blend system, the relative intensity of the “complexed” carbonyl stretching band of the PCL block tends to increase when either the LiClO4 concentration or the length of the PCL ...

Mechanical Behavior and Biodegradation of Poly(ε-caprolactone)/Starch Blends with and without Expansor

The use of biodegradable polymers has provided an alternative to the problem of polymer-based products discarded in the environment. Poly(e-caprolactone) (PCL) is a biodegradable polymer that has been used industrially, but it is very expensive. Starch is a potentially useful material for biodegradable plastics because of its natural abundance and low cost. The aim of this work was to examine the effect of adding azodicarbonomide (ADC) as an expansor to blends of PCL with corn starch. Different proportions, of ADC (0.1%, 0.2% and 0.3%, w/w) were added to pure PCL and to PCL/starch (50/50) blends and their properties were studied. Biodegradable blends of PCL with starch had a higher density than PCL alone and the addition of ADC reduced the density of the materials. The incorporation of starch increased the water absorption and ADC did not significantly alter this property. The incorporation of starch into PCL reduced the tensile strength and the elongation at break; ADC enhanced these reductions and also decreased the Young’s modulus of PCL. SEM showed that blends prepared with starch were immiscible, had a homogeneous dispersion of starch, and poor interfacial adhesion. The addition of ADC resulted in cells in the interior of the polymers. The 50/50 PCL/starch blends biodegraded faster than PCL, and ADC had no significant influence on the biodegradation of the blends but inhibited the biodegradation of PCL.

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Poly(3-hydroxybutyrate) (PHB) is a thermoplastic polyester with a great potential owing to its biodegradability, bioreabsorbation and biological synthesis from a renewable source. Despite these characteristics, the applications of this polymer are very restricted due to its poor mechanical properties and thermal instability at temperatures above its melting point (around 175 °C). Among the possibilities of improvement of these materials, the development of blends is a relatively fast and inexpensive option. Poly(e-caprolactone) (PCL) is a semi-crystalline polymer that may be used as a biomaterial. It presents good mechanical properties, a low melting point (around 55 °C), and could be a good option to develop PHB blends, maintaining the biodegradability and bioreabsorption properties. The objective of the present work was to obtain blends of PHB and PCL by melting mixture in an internal mixer. The compositions varied from 0 to 30 wt% of PCL. DSC, DMA, and SEM were used to characterize the blends. The blends were found to be imiscible with no indication of interaction either the amorphous or crystalline state. The morphology shows PHB as the matrix and PCL as the dispersed phase.

An Unusual, Completely Miscible, Ternary Hydrogen-Bonded Polymer Blend of Phenoxy, Phenolic, and PCL

We have investigated the miscibility and hydrogen-bonding behavior of ternary blends of phenoxy, phenolic, and poly(e-caprolactone) (PCL) by using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. On the basis of DSC analyses, we observed a rare totally miscible ternary hydrogen-bonded polymer blend in the amorphous phase: all compositions of this ternary blend display a single glass transition temperature. In addition, these single glass transition temperatures can be predicted well by extending the Kwei equation from the binary polymer blend to this ternary polymer blend. The infrared spectra indicate that the intermolecular hydrogen bonding of each pair of binary components still exists in the ternary polymer blend. We used the ternary totally miscible blend to determine the interassociation equilibrium constant between the hydroxyl groups of phenolic and the hydroxyl groups of phenoxy indirectly from the fraction of hydrogen-bonded carbonyl groups of PCL. Quantitati...

Ternary Thermosetting Blends of Epoxy Resin, Poly(ethylene oxide) and Poly(ε‐caprolactone)

AbstractSummary: The ternary thermosetting blends composed of epoxy resin, poly(ethylene oxide) (PEO) and poly(ε‐caprolactone) (PCL) were prepared via in situ polymerization of epoxy monomers in the presence of the two crystalline polymers, PEO and PCL. DSC results showed that the binary blends of epoxy with PEO (and/or PCL) are fully miscible in the entire composition in the amorphous state. FTIR indicates that there were interchain specific interactions between the crosslinked epoxy and the linear polymers in the binary blends and the hydrogen bonding interactions between epoxy and PCL are much weaker than those between epoxy and PEO. The difference in the strength of interchain specific interactions gives rise to the competitive hydrogen bonding interactions in the ternary blends of epoxy, PEO and PCL, which were evidenced by the results of FTIR. The results of optical microscopy and DSC showed that in the ternary blends PCL component separated out with inclusion of PEO. The formation of the specific phase structures is ascribed to the competitive interchain specific interactions among the crosslinked epoxy, PEO and PCL.Phase boundary diagram of epoxy, PEO and PCL ternary blends.imagePhase boundary diagram of epoxy, PEO and PCL ternary blends.

Synthesis of Starch‐g‐Poly(glycidyl methacrylate) and Its Blending with Poly(ϵ‐caprolactone) and Nylon 610

AbstractDifferent amounts of glycidyl methacrylate (GMA) were grafted onto corn starch dispersed in water or dimethyl sulfoxide (DMSO) to yield starch‐graft‐poly(glycidyl methacrylate) (ST‐g‐PGMA). ST‐g‐PGMAW, obtained by grafting PGMA onto corn starch that was dispersed in water, showed a higher PGMA grafting content and a lower content of the homopolymerized PGMA than ST‐g‐PGMAD, which was prepared in DMSO. The modified starches were blended with poly(ϵ‐caprolactone) (PCL) and nylon 610, respectively, and the tensile properties of the blends were measured by UTM. Mechanical properties of the biodegradable ST‐g‐PGMA/PCL blends were dependent on the PGMAD content grafted on starch. Without dramatic loss of the tensile properties of PCL, ST‐g‐PGMAW was melt blended with PCL. Meanwhile, an increase in the tensile modulus was observed in the ST‐g‐PGMAW/nylon 610 blend. When nylon 610 was reacted with ST‐g‐PGMAW in DMSO in the presence of triethylamine, the tensile modulus and strength were much higher than those of the pure nylon 610, and phase‐separated domains of starch were not observed microscopically.

Elaboration and Characterization of Starch/ Poly(caprolactone) Blends

AbstractA starch‐based biodegradable material was prepared in two steps. Firstly, starch was chemically modified by using formic acid at 20°C to obtained degrees of substitution of about 1.2. The level of destructuration was also assessed using dynamic rheological measurements. Native starch or starch ester were then mixed with poly(caprolactone) and different polyester oligomers were added as compatibilisers and plasticizing agents. PCL oligomers were found to be the most efficient ones. A significant improvement of the elongation at break of starch formate/PCL/oligo PCL blends was achieved.