Influence of polycaprolactone/polyglycolide blended electrospun fibers on the morphology and mechanical properties of polycaprolactone

Polycaprolactone (PCL) and polyglycolide (PGA) are two biopolymers that have been used as in situ biomedical devices for various applications. The obstacle of creating a composite that captures the benefit of PCL's long degradation time, while acquiring the strength from PGA is overcoming the lack of surface adhesion between the two biopolymers for stress transfer to occur. This study investigates the use of miscible PCL‐PGA blended fibers, created by electrospinning, to increase the interfacial bonding of fibers to the PCL matrix of the polymer–polymer composite. The use of the blended fibers will thereby create the ability of load transfer from the long‐term PCL matrix to the stronger PCL‐PGA fiber reinforcement. The incorporation of the PCL‐PGA fibers was able to increase the tensile yield strength and Young's modulus over that of the bulk PCL, while decreasing the percent elongation at break. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40224.     

Fibro‐porous poliglecaprone/polycaprolactone conduits: synergistic effect of composition and in vitro degradation on mechanical properties

Blends of poliglecaprone (PGC) and polycaprolactone (PCL) of varying compositions were electrospun into tubular conduits and their mechanical, morphological, thermal and in vitro degradation properties were evaluated under simulated physiological conditions. Generally, mechanical strength, modulus and hydrophilic nature were enhanced by the addition of PGC to PCL. An in vitro degradation study in phosphate‐buffered saline (pH 7.3) was carried out for up to 1 month to understand the hydrolytic degradation effect on the mechanical properties in both the longitudinal and circumferential directions. Pure PCL and 4:1 PCL/PGC blend scaffolds exhibited considerable elastic stiffening after a 1 month in vitro degradation. Fourier transform infrared spectroscopic and DSC techniques were used to understand the degradation behavior and the changes in structure and crystallinity of the polymeric blends. A 3:1 PCL/PGC blend was concluded to be a judicious blend composition for tubular grafts based on overall results on the mechanical properties and performance after a 1 month in vitro degradation study. © 2014 Society of Chemical Industry     

Effect of coupling agents on the degradation of polypropylene/fly ash composites

Composites containing 50% wt fly ash (sourced from the UK and South Africa) in polypropylene homopolymer (manufacturer stabilized for general purpose use) have been prepared by using batch and continuous methods. The effect of the following coupling agents were investigated on the photo‐ and thermal‐decomposition of the composite materials: Lubrizol Solplus C800 (an unsaturated carboxylic acid), γ‐methacryloxypropyl trimethoxy silane (γ‐MPS), 1,3‐phenylene dimaleimide (BMI), and maleic anhydride‐grafted‐polypropylene (m‐PP). High melt, thermal‐, and photo‐stability was favored when the matrix was coupled to the filler surface by monomeric coupling agents that were expected to adsorb in a close packed layer on the fly ash surface. Further improvements were observed in cases where the coupling agent could also self‐polymerize. m‐PP did not lead to increased stability due to its low adsorption density on the fly ash surface. The relatively high water/acid soluble transition metal ion content of the UK sourced fly ash did not appear to affect stability under the test conditions employed in this study. The South African sourced fly ash had a higher level of quartz and mullite together with a high level of group 1 and 2 metals. The latter in particular may have led to debonding of the coupled interfacial region from the filler surface and possible adsorption of stabilizers on the pristine surface. This resulted in the South African fly ash generally possessing poorer resistance to oxidation than the UK fly ash. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39974.     

Preparation and properties of multiwalled carbon nanotube/polycaprolactone nanocomposites

Multiwalled carbon nanotube/polycaprolactone nanocomposites (MWNT/PCL) were prepared by in situ polymerization, whereby as‐received MWNTs (P‐MWNTs) and purified MWNTs (A‐MWNTs) were used as reinforcing materials. The A‐MWNTs were purified by nitric acid treatment, which introduced the carboxyl groups (COOH) on the MWNT. The micrographs of the fractured surfaces of the nanocomposites showed that the A‐MWNTs in A‐MWNT/PCL were better dispersed than P‐MWNTs in PCL matrix (P‐MWNT/PCL). Percolation thresholds of the P‐MWNT/PCL and A‐MWNT/PCL, which were studied by rheological properties, were found at ～2 wt % of the MWNT. The conductivity of the P‐MWNT/PCL was between 10^?1 and 10^?2 S/cm by loading of 2 wt % of MWNT although that of the A‐MWNT/PCL reached ～10^?2 S/cm by loading of 7 wt % of MWNT. The conductivity of the P‐MWNT/PCL was higher than that of the A‐MWNT/PCL at the entire range of the studied MWNT loading, which might be due to the destruction of π‐network of the MWNT by acid treatment, although the A‐MWNT/PCL was better dispersed than the P‐MWNT/PCL. The amount of the MWNT at which the conductivity of the nanocomposite started to increase was strongly correlated with the percolation threshold. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1957–1963, 2007     

Magnetic composite scaffolds of polycaprolactone/nFeHA,for bone-tissue engineering

Magnetic composite scaffolds of polycaprolactone/Fe doped nanohydroxyapatite (PCL/nFeHA) with different composition ratios have been fabricated lyophilization for the purpose of bone-tissue engineering. Magnetic measurements reveal some interaction between the Fe particles that decreases steadily as the nFeHA is diluted in the polymer. All the scaffolds were characterized before and after in vitro degradation for over 28 weeks. The nFeHA nanoparticles decreased the initiation rate of hydrolytic degradation. After 16 weeks degradation, thermograms of the first heating revealed two melting peaks, which could be attributed to the presence of crystals of two different sizes. GPC results indicated that Mw and Mn were unaffected by the degradation with no cleavage of the macromolecular chains.     

Photo-oxidative degradation of polypropylene/montmorillonite nanocomposites

The photo-oxidative behavior of the polypropylene (PP)/montmorillonite (MMT) nanocomposites and microcomposites has been investigated upon ultraviolet exposure using the technique of infrared spectroscopy. The rate of photo-oxidative degradation of PP/MMT nanocomposites is much faster than that of pure PP. The influence of pristine MMT, alkylammonium and compatibilizer were investigated, respectively. All these components can catalyze the photo-oxidation of PP matrix, in which the influence of compatibilizer and pristine MMT is primary. Moreover, the dispersion state of the clay particles in the polymer matrices has a little influence on the photo-oxidative degradation of polymer matrix. Consequently, an integrated catalysis mechanism of the photo-oxidative degradation of PP clay nanocomposite is proposed. It would provide benefit direction for the preparation and usage of polymer layered silicate nanocomposites (PLSN).     

Preparation and characterizations of polycaprolactone/green coconut fiber composites

The mechanical, thermal, and morphological properties of polycaprolactone (PCL) and green coconut fiber (GCF) composites were evaluated. Blends containing acrylic acid‐grafted PCL (PCL‐g‐AA/GCF) exhibited noticeably better mechanical properties due to better compatibility between the two components. The dispersion of GCF in the PCL‐g‐AA matrix was significantly more homogeneous due to the creation of branched and cross‐linked macromolecules via reactions between carboxyl groups in PCL‐g‐AA and hydroxyl groups in GCF. The tensile strength of the PCL‐g‐AA/GCF composites at break was considerably greater than that of PCL/GCF composites. In addition, the PCL‐g‐AA/GCF blend was more easily processed due to lower melt viscosity. Biodegradation tests were performed with each composite in an Acinetobacter baumannii BCRC 15556 environment. The mass of both composites was reduced by the GCF content within 4 weeks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Biodegradable nanocomposites based on starch/polycaprolactone/compatibilizer ternary blends reinforced with natural and organo‐modified montmorillonite

In this article, biodegradable polymer/clay nanocomposites were prepared. The matrices used were based on blends of Polycaprolactone (PCL) and Anhydride‐Functional Polycaprolactone (PCL‐gMA) with Thermoplastic Starch (TPS). Nanocomposites films based on PCL/TPS and PCL/PCL‐g‐MA/TPS blends reinforced with 1 and 3 wt % of natural montmorillonite and two organo‐modified ones were prepared by melt intercalation followed by compression molding. The study was designed focusing on packaging applications. Grafting maleic anhydride onto PCL was efficient to improve PCL/TPS compatibility but did not modify matrix/nanoclay interaction. Matrix compatibilization and nanoclays increased the Youn?s modulus and slightly decreased the maximum stress of the TPS/PCL matrix. Nanoclay functionalization improved nanoclay dispersion in the blends but it was not reflected in mechanical properties improvements. The water adsorption of the compatibilized matrix was reduced after clay incorporation. A slight decrease in the biodegradation rate was observed with the addition of nanoclay. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44163.     

Effect of convergent–divergent flow on thermal and crystallization properties of PP/MWCNTs nanocomposites

A melt‐mixing process based on convergent–divergent flow has been used to prepare PP/MWCNT composites with a self‐built convergent–divergent die (C‐D die) composed of different numbers of convergent plates. Dynamic extensional deformation was generated in the C‐D die, which improved the mixing effect and mixing efficiency of the composites during extrusion. The C‐D die acted as a mixer for composites when mounted onto a capillary rheometer. The residence time of PP/MWCNTs melt in the extensional flow field is adjusted by changing the numbers of convergent plates and the velocity of the ram. The intensity of extensional flow field is controlled by the structure of the convergent plate and the ram velocity. Influences of convergent–divergent flow on PP/MWCNTs composites were characterized in terms of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). TEM results showed that MWCNTs disperse more homogeneously with the increase of convergent plates. DSC showed that the crystallinity of PP/MWCNTs composites increased and the crystallization temperature shifted to higher temperature with the increase of the numbers of the convergent plates. TGA showed that the thermal stability of composites improved remarkably. The decomposition temperature increases from 381 to 408.2°C when the numbers of convergent plates increased from 2 to 8. In addition, the increase of ram velocity also has the same influences on the dispersion of MWCNTs in the resin and the properties of PP/MWCNTs nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42330.     

Effect of nanosilver on the photodegradation of poly(lactic acid)

The poly(lactic acid), PLA, mixed with nanosilver in solution easily forms nanocomposite in solid state (after solvent evaporation), which was proved by UV–Vis spectroscopy. This work focuses on photodegradation occurring in PLA films doped with nanosilver. The changes in chemical structure of photodegraded PLA has been determined using FTIR spectroscopy. Differential scanning calorimetry of UV‐irradiated PLA samples provided information on polymer glass transition and crystallization/melting processes. It was found that PLA alone is more sensitive to photodegradation than PLA/silver nanocomposites. The mechanism of nanocomposite photodegradation and effect of nanosilver was discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40144.     

The fabrication of flexible and oxygen barrier cellulose nanofiber/polylactic acid nanocomposites using cosolvent system

The main disadvantages of polylactic acid (PLA) for food packaging applications are its brittleness and poor gas barrier properties. The purpose of this study is to evaluate the potential usability of triethyl citrate (TEC) and cellulose nanofiber (CNF) in PLA to obtain bio-based films with optimal properties. The incorporation of CNF as reinforcement fillers in polymer matrix has long been debated due to its difficulties to disperse uniformly in hydrophobic polymer matrix attribute to their hydrophobic nature. In order to overcome this problem, different feeding method for CNF into the mixer was studied, and CNF/PLA nanocomposites were characterized. It was found that CNF was successfully dispersed in the PLA matrix through the TEC-CNF suspension, which greatly improved tensile strength and flexibility of the CNF/PLA nanocomposites. The oxygen barrier property was enhanced up to 47.3% (16.99 cc·mm/m²·day·atm) with the increase loading of 0.25, 0.50, and 1 wt% of CNF. Moreover, the dynamic mechanical analysis showed that the low tan delta peak of CNF/PLA nanocomposites (48.25°C) was shifted to high peak (52.99°C) due to incorporation of TEC; indicates an improved of thermal stability of the composites. Overall, the t-CNF/PLA nanocomposites show a great feasibility for various eco-friendly flexible packaging applications.     

Morphology and thermal degradation studies of melt‐mixed PLA/PHBV biodegradable polymer blend nanocomposites with TiO2 as filler

The morphology and thermal stability of melt‐mixed poly(lactic acid) (PLA)/poly(hydroxybutyrate‐co‐valerate) (PHBV) blends and nanocomposites with small amounts of TiO₂ nanoparticles were investigated. PLA/PHBV at 50/50 w/w formed a co‐continuous structure, and most of the TiO₂ nanoparticles were well dispersed in the PLA phase and on the interface between PLA and PHBV, with a small number of large agglomerates in the PHBV phase. Thermogravimetric analysis (TGA) and TGA–Fourier‐transform infrared spectroscopy was used to study the thermal stability and degradation behavior of the two polymers, their blends, and nanocomposites. The thermal stability of PHBV was improved through blending with PLA, whereas that of the PLA was reduced through blending with PHBV, and the presence of TiO₂ nanoparticles seemingly improved the thermal stability of both polymers in the blend. However, the degradation kinetics results revealed that the nanoparticles could catalyze the degradation process and/or retard the volatilization of the degradation products, depending on their localization and their interaction with the polymer in question. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42138.     

Spinnability of chitosan butyrate/cellulose acetate for obtaining a blend fiber

The production of chitosan fibers has remained of interest over the last decade. However, the copolymer structure of partially deacetylated chitosan generally lowers the dry/wet strength properties of chitosan fibers. There are numerous methods available for improving the mechanical properties of chitosan fibers, that is, the strain and stress to failure. In this work, the blending of chitosan with cellulose acetate is described. The chitosan is in the form of the butyrate ester, which, like cellulose acetate, is easily transesterified to regenerate the polysaccharide. The fibers obtained from codissolving cellulose acetate with chitosan butyrate are described. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Investigation of the thermostability of poly(ethylene terephthalate)–hemp fiber composites: Extending natural fiber reinforcements to high‐melting thermoplastics

The thermal stability of poly(ethylene terephthalate) reinforced with 1, 5, 10, 15, and 20% hemp fibers was investigated with the aim of extending the applications of biocomposites to high‐melting thermoplastics. The material was injection‐molded following compounding with a torque‐based Rheomix at 240, 250, and 260°C. A combination of thermogravimetric methods at 5, 10, and 20°C/min, Liu and Yu's collecting temperature method, and Friedman's kinetic method were used for testing and analysis. A significant thermostability for all formulations was observed below 300°C; this demonstrated their potential for successful melt processing. Moreover, two degradation steps were observed in the temperature ranges 313–390 and 390–490°C. The associated apparent activation energies within the temperature ranges were determined as 150–262 and 182–242 kJ/mol, respectively. We found that the thermostability was significantly affected by the heating rates; however, the effect of the temperature of the mixing chamber was negligible. These findings suggest that the successful melt processing of high‐melting thermoplastics reinforced with natural fibers is possible with limited fiber thermodegradation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42500.     

Studies on thermal degradation and flame retardant behavior of the sisal fiber reinforced unsaturated polyester toughened epoxy nanocomposites

Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant, and morphological behavior of the UP toughened epoxy (Epoxy/UP) were systematically studied. The chemical structures of Epoxy, UP, and Epoxy/UP systems were characterized using Proton Nuclear magnetic resonance (¹HNMR) and Fourier transform infrared (FTIR) spectra. The homogeneous dispersion of nanoclay within the polymer matrix was analyzed using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis. Incorporation of sisal fibers and C30B nanoclays within Epoxy/UP system resulted in an increase in the mechanical, thermal, and flame retardance properties. Thermogravimetric analysis (TGA) has been employed to evaluate the thermal degradation kinetic parameters of the composites using Kissinger and Flynn‐Wall‐Ozawa methods. Cone calorimeter, UL‐94, and LOI tests revealed a reduction in the burning rate of the matrix with the addition of fibers and nanoclays. The results showed that the treated fiber reinforced nanocomposites had higher thermal stability and better flame retardant properties than the treated fiber reinforced composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42068.     

Preparation and degradation of PLA/chitosan composite materials

As scaffold material, poly(lactic acid) (PLA) has several obvious weaknesses, such as fast biodegradation, acidic degradation product, and hydrophobicity. To solve these problems, a series of PLA/chitosan composite materials was prepared in this study. SEC observation, porosity tests and contact angle measurements showed that the materials were hydrophilic and had appropriate porosity and structure, which were favorable to the cell growth. Degrading tests in vitro indicated that the degrading speeds of the materials were slower than that of PLA, and the materials could keep adjacently litmusless, certain shape and mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 274–277, 2004     

Effect of zinc oxide nanoparticles on the in vitro degradation of electrospun polycaprolactone membranes in simulated body fluid

Even though the biodegradability of polycaprolactone (PCL) is well established, few studies have carried out on the effect of nanofillers on the in vitro degradability of electrospun PCL membranes. Thus, the authors incorporated common nanofiller zinc oxide (ZnO) nanoparticles in electrospun PCL membranes. From the study of morphological schanges as well as the changes in crystallinity, it is clear that the ZnO nanoparticles accelerated the degradation of PCL. The FTIR results ascertain that the hydrolysis of the PCL nanofibers generates free hydroxyl and carbonyl groups in the bulk of the polymer. The tensile property of the PCL/ZnO nanocomposite membranes decreased with an increase in filler loading during degradation.     

Studies on the thermal stability and degradation kinetics of Pd/PC nanocomposites

Effect of heating rate, Pd content, and synthesis method on the thermal stability of the ex situ and in situ Palladium/polycarbonate (Pd/PC) nanocomposites was investigated. TEM images revealed discrete Pd nanoclusters of about 5 and 15 nm sizes for 1 and 2 vol % ex situ nanocomposites, respectively. However, agglomerated Pd nanoclusters were noticed in the in situ samples, irrespective of the Pd content. The ex situ Pd/PC nanocomposites showed high onset temperature (Ti) for thermal degradation of PC than the in situ and pure PC samples. Pd content and heating rates were found to have a positive influence on the Ti and Tm (temperature at the maximum degradation rate occurs) of the Pd/PC nanocomposites. Thermal degradation of the PC was found to follow the first‐order kinetics in the Pd/PC nanocomposites. The activation energies associated with the degradation were determined by using the Kissinger method. These activation energies are used to construct the Master decomposition curve (MDC) and weight–time–temperature (α–t–T) plots that describe the time‐temperature dependence of the PC pyrolysis in the Pd/PC nanocomposites. These constructed α–t–T plots were validated with the data from isothermal measurements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of glassy carbon addition and photodegradation on the biodegradation in aqueous medium of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/glassy carbon green composites

The use of biodegradable polymers is an interesting way to reduce the polymeric waste accumulation in the environment. However, the addition of fillers to biodegradable polymer matrices may decrease their biodegradability. Glassy carbon (GC) is a promising carbon material that can be employed as a filler in the production of antistatic packaging utilized to protect electronic components. The use of a biodegradable polymeric matrix such as poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) can be an excellent alternative for the preparation of green composites to be used in these packages. This work aims to evaluate the effect of the GC addition and the GC particle size on the biodegradability of the PHBV matrix, as well as to study the result of the employment of a previous photodegradation treatment on the biodegradation in aqueous medium of PHBV/GC composites. Scanning electron microscopy, residual weight measurement (%) and surface roughness showed that GC does not interfere negatively with PHBV biodegradability. Differential scanning calorimetry analysis and residual weight measurement permitted to suggest that the increase in the crystallinity degree of PHBV and PHBV/GC samples occasioned by the ultraviolet radiation hindered the water and enzyme access to the bulk of the materials, decreasing the biodegradability.     

Effect of biological degradation by termites on the flexural properties of pinewood residue/recycled high‐density polyethylene composites

Wood–plastic composites (WPCs) are considered to be highly durable materials and immune to any type of biological attack. However, when one of these composites is exposed to accelerated weathering, its surface is affected by the appearance of cracks, which constitute an ideal access route for biotic agents. Although the destruction of wood caused by termites is recognized worldwide, information on their effects on WPC‐based products is scarce. Thus, in this study, we aimed to examine the effects of termite attacks on weathered and nonweathered pinewood residue/recycled high‐density polyethylene composites. In this study, WPCs with 40 wt % wood were prepared. Test samples obtained by compression molding and profile extrusion were subjected to weathering cycles for 1000 and 2000 h with a UV‐type accelerated tester equipped with UVA‐340 fluorescent lamps. Afterward, specimens were exposed to the attack of higher termites (Nasutitermes nigriceps) native to the Yucatan Peninsula. Subsequently, flexural mechanical essays, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analyses were performed. FTIR spectroscopy and DSC showed that the surfaces of the compression‐molded specimens were degraded to a higher extent because of the accelerated weathering. The microscopy results revealed that severe damage was caused by the termites on the surface of the compression‐molded samples. Statistical analysis of the mechanical test results showed that biotic attack produced significant changes in the samples previously exposed to accelerated weathering. The results show that the processing method directly affected the sample performance because of differences in the surface composition. The profile‐extruded composites seemed to better resist termite attack. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013