Controlled drug release carriers based on PCL/PEO/PCL block copolymers

In order to create a new drug delivery system, the ibuprofen-loaded triblock copolymer PCL/PEO/PCL (PCEC) microspheres with a low PEO content (<2?wt%) were prepared by oil in water (o/w) solvent evaporation technique. The influence of PEO content, molecular weight of a polymer matrix and drug loading on the ibuprofen release profiles were evaluated. The interactions between polymer matrix and ibuprofen were detected by FTIR analysis. The presence of hydrophilic PEO segment in PCL chains caused the decrease in particle size, which further had a great impact on the drug release kinetics, i.e., initially faster release and significantly higher quantity of released drug compared to neat PCL. Ibuprofen release behavior from polymer matrix was governed by a diffusion process. In vitro cytotoxicity tests revealed that empty PCL and PCEC microspheres were not toxic at low concentrations, while ibuprofen-loaded microspheres exhibited cytotoxicity correlated with amounts of incorporated drug.     

Preparation of ibuprofen‐loaded HDPE tubular devices for application as urinary catheters

In this study, high‐density polyethylene tubes with the incorporation of ibuprofen (IBP) were investigated with a view to their application as urinary catheters. The melt extrusion process was used to prepare the urinary catheters, and the influence of the manufacturing parameters on the material properties was evaluated. Samples prepared at lower temperature resulted in a more homogeneous material with a smoother surface, lower crystallinity, and better mechanical properties. The drug release was faster in the first 4 days, due to the accumulation of the drug on the outer surface of tubes. The concentration of IBP released was similar to the drug content in commercially available topic formulations (5%). Furthermore, after 2 days of immersion, the release achieved the concentration known to inhibit bacterial growth (6 mg/mL). These characteristics indicate that this material has good potential for application in urinary catheters. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45661.     

Preparation and Properties of ZnAl Layered Double Hydroxide/Polycaprolactone Nanocomposites for Use in Drug Delivery

ZnAl-layered double hydroxides (ZnAl-LDH)/polycaprolactone (PCL) nanocomposites were prepared by solution intercalation method. It is shown that lamellar ZnAl-LDH is randomly distributed in the PCL matrix with diameter of 60 nm. The addition of ZnAl-LDH decreases thermal decomposition temperature of composites, but improves the elastic modulus and tensile strength. The weight loss and release amount of diclofenac of ZnAl-LDH/PCL composites are higher than that of neat PCL. The drug release kinetics for nanocomposites and neat PCL could be described by first-order kinetic and Ritger-Peppas kinetic model.     

High temperature bending properties and failure mechanism of 3D needled C/SiC composites up to 2000 ℃

Three-dimensional (3D) needled C/SiC composites were prepared and subjected to three-point bending tests from room temperature (RT) to 2000 ℃ under vacuum. The results show that the flexural strength and modulus increase in the range of RT to 800 °C due to the release of thermal residual stress (TRS). At 800–1700 °C, the modulus further increases for the further release of TRS, while the destruction of the pyrolytic carbon (PyC) coating reduces the flexural strength. Up to 2000 ℃, the thermal mismatch stress in the composites cause fiber slippage and matrix crack deflection to be zigzag, which increase the fracture strength. The change of components properties mediated by high temperature and the release of TRS play a leading role in the flexural strength and fracture mode. The results provide important support for the mechanical behavior of 3D needled C/SiC composites at ultra-high temperature.     

Effects of the processing temperature on the nanostructure and mechanical properties of PCTG‐based nanocomposites

The influence of the processing temperature on both the dispersion level and the mechanical properties of the amorphous copolyester (PCTG)/organoclay (Cloisite® 20A) nanocomposite (NC) is studied in this article. At high processing temperatures, no change in the chemical nature of the matrix was observed, but its molecular weight decreased. Widely dispersed structures were observed by wide angle X‐ray diffraction (WAXD) and transmission electron microscopy whatever the processing temperature might be. Dispersion was greatest for the samples processed at 200°C due to the highest viscosity of these samples and decreased at higher processing temperatures (T_p). These different dispersion levels led to a large modulus increase (71%) after processing at 200°C and to lower ones (about 50%) after processing at 230 and 260°C. The ductility of the NCs decreased at lower processing temperatures. The decrease was attributed to the greater stiffness of the matrix, and was not significant enough to modify the ductile nature of the NCs, which showed clear yield points even at the lowest processing temperature (200°C). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

TPU/PCL/nanomagnetite ternary shape memory composites: studies on their thermal, dynamic-mechanical, rheological and electrical properties

Shape memory polymer composites based on a blend of thermoplastic polyurethane (TPU) segmented block copolymer and poly(ε-caprolactone) (PCL) with weight ratio of 70/30 and various nanomagnetite contents (0–5 wt%) were prepared by melt blending of TPU and PCL, together with a masterbatch of TPU/nanomagnetite. The samples were compounded for 10 min at 200 °C using an internal mixer. Synthesized nanomagnetite powder was introduced to the masterbatch via a solution mixing method using a high-intensity ultrasonic horn. Subsequently, thermal, mechanical, rheological and electrical properties of the TPU/PCL/nanomagnetite shape memory composites were investigated through various tests. The degree of crystallization of the PCL component in the composite structure was inspected by differential scanning calorimetry (DSC) and X-ray diffraction measurements. The results revealed that the percentage of crystallinity and the melting temperature of the PCL component changed in the presence of magnetite nanoparticles, which was related to the nanoparticles acting as nucleants. Observing a single glass transition temperature (T _g) in DSC thermograms of the samples was indicative of good compatibility of the TPU and PCL components in the composite structure. This was also confirmed by dynamic-mechanical analysis in which the loss modulus curves showed a single glass transition temperature. Moreover, the loss modulus peak at glass transition was lowered and broadened by addition of nanomagnetite, by which it was assumed that introducing nanoparticles into the system changed the mechanism of glass transition due to particle–matrix interactions. The dynamic rheological and electrical resistivity experiments verified the existence of a low percolation threshold at about 2 wt% nanomagnetite. The state of nanomagnetite dispersion in the masterbatch and the microstructure of the ternary composites were characterized by scanning electron microscopy. Finally, adding nanomagnetite led to weakening of shape recovery of the polymer blend, with shape recovery dropping to 70 % at 5 % of nanomagnetite.     

Fabrication and properties of carbon nanotube/styrene–ethylene–butylene–styrene composites via a sequential process of (electrostatic adsorption aided dispersion)‐plus‐(melt mixing)

Carbon nanotube (CNT)/styrene–ethylene–butylene–styrene (SEBS) composites were prepared via a sequential process of (electrostatic adsorption assisted dispersion)‐plus‐(melt mixing). It was found that CNTs were uniformly embedded in SEBS matrix and a low percolation threshold was achieved at the CNT concentration of 0.186 vol %. According to thermal gravimetric analysis, the temperatures of 20% and 50% weight loss were improved from 316°C and 352°C of pure SEBS to 439°C and 463°C of the 3 wt % CNT/SEBS composites, respectively. Meanwhile, the tensile strength and elastic modulus were improved by about 75% and 181.2% from 24 and 1.6 MPa of pure SEBS to 42 and 4.5 MPa of the 3 wt % CNT/SEBS composite based on the tensile tests, respectively. Importantly, this simple and low‐cost method shows the potential for the preparation of CNT/polymer composite materials with enhanced electrical, mechanical properties, and thermal stability for industrial applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40227.     

Mechanical,thermal, electrical,and interfacial properties of high‐performance bisphthalonitrile/polyarylene ether nitrile/glass fiber composite laminates

Bisphthalonitrile (BAPh)/polyarylene ether nitrile end‐capped with hydroxyl groups (PEN‐OH) composite laminates reinforced with glass fiber (GF) have been fabricated in this article. The curing behaviors of BAPh/PEN‐OH prepolymers have been characterized by differential scanning calorimetry and dynamic rheological analysis. The results indicate that with the introduction of PEN‐OH the curing temperature of BAPh has decreased to 229.6–234.8°C and BAPh/PEN‐OH prepolymers exhibit large processing windows with relatively low melt viscosity. The BAPh/PEN‐OH/GF composite laminates exhibit tensile strength (272.4–456.5 MPa) and modulus (4.9–10.0 GPa), flexural strength (507.1–560.9 MPa), and flexural modulus (24.0–30.4 GPa) with high thermal (stable up to 538.3°C) and thermal stabilities (stable up to 475.5°C). The dielectric properties of BAPh/PEN‐OH/GF composite laminates have also been investigated, which had little dependence on the frequency. Meanwhile, scanning electron microscopy results show that the BAPh/PEN‐OH/GF composite laminates display excellent interfacial adhesions between the matrix and GFs. Herein, the BAPh/PEN‐OH matrix can be a good matrix for high‐performance polymeric materials and the advanced BAPh/PEN‐OH/GF composite laminates can be used under high temperature environment. POLYM. COMPOS., 34:2160–2168, 2013. © 2013 Society of Plastics Engineers     

Properties of polyamide‐zirconia nanocomposites prepared from sol‐gel technique

Transparent nanocomposites were prepared by producing zirconia network in glassy polyamide matrix using sol‐gel technique. Different amounts of tetrapropyl zirconate (TPZ) were added in polymer solution using anhydrous dimethylformamide as solvent. TPZ was hydrolyzed and condensed in situ in the matrix for the generation of inorganic networks using diethylamine. Thin and transparent films containing different proportions of zirconia were obtained by evaporating the solvent. Mechanical, dynamic mechanical thermal and morphological analyses of these films were carried out. An increase in tensile modulus was observed with the films containing zirconia contents up to 15 wt%, but the elongation at rupture was found to decrease sharply on further addition of zirconia. Toughness of the hybrid materials decreased with increased amount of zirconia. Dynamic mechanical thermal analysis (DMTA) performed on the samples indicates an increase in the glass transition temperature; 102°C with pure polyamide to 132°C with polyamide containing 15 wt% zirconia contents. The storage modulus was also found to increase with increase in zirconia proportion in the matrix. The decrease in the storage modulus of the hybrids with rise in temperature was observed to be much smaller as compared with that of pure polymer. Thermal decomposition temperatures of the hybrids were found in the range of 450–500°C. The weights of the residues left at 700°C were nearly proportional to the zirconia contents in the original hybrids. The morphological studies suggest a uniform dispersion of zirconia domains in the matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

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 Organomodified Ni-Al Layered Double Hydroxide (OLDH) on the Properties of Polypropylene (PP)/LDH Nanocomposites

This work addresses the effect of organomodified layer double hydroxide (OLDH) on the properties of PP/LDH nanocomposites prepared by melt intercalation method using a single screw extruder with maleic anhydride grafted polypropylene (PP-g-MA) as a compatibilizer. For this, Ni-Al LDH was first prepared by the co-precipitation method at constant pH using their nitrate salts. The above synthesized pristine LDH was organically modified using sodium dodecyl sulphate (SDS) by the regeneration method. The structural and thermal properties of LDH and PP nanocomposites were performed by X-ray diffraction (XRD), FTIR spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The influence of LDH loading on the mechanical and thermal properties of the nanocomposite was also investigated. The XRD results confirmed the formation of exfoliated PP/LDH nanocomposites. PP/LDH nanocomposites exhibited enhanced thermal stability relative to the pure PP. When 10% weight loss was selected as a point of comparison, the decomposition temperature of PP/LDH (5 wt%) nanocomposite was 15.3°C higher than that of pure PP. The DSC result indicated an increase in crystallization and melting temperature of the PP/LDH nanocomposites compared to pure PP. Overall, the mechanical properties of the PP/LDH nanocomposites increased with an increase in the LDH content. The maximum improvement of tensile strength, Young's modulus, flexural strength, and flexural modulus for the PP/LDH nanocomposite was found to be 11, 22.5, 28, and 22%, respectively, over neat PP. For comparison purposes, a nanocomposite with 5 wt% modified bentonite (PP/B5) was also prepared under the same operating condition and there was no significant improvement in mechanical properties (tensile strength and modulus).     

Nonisothermal crystallization kinetics and thermomechanical properties of multiwalled carbon nanotube‐reinforced poly(ε‐caprolactone) composites

BACKGROUND: The technological development of poly(ε‐caprolactone) (PCL) is limited by its short useful lifespan, low modulus and high crystallinity. There are a few papers dealing with the crystallization behavior of carbon nanotube‐reinforced PCL composites. However, little work has been done on the crystallization kinetics of melt‐compounded PCL/multiwalled carbon nanotube (MWNT) nanocomposites. In this study, PCL/MWNT nanocomposites were successfully prepared by a simple melt‐compounding method, and their morphology and mechanical properties as well as their crystallization kinetics were studied. RESULTS: The MWNTs were observed to be homogeneously dispersed throughout the PCL matrix. The incorporation of a very small quantity of MWNTs significantly improved the storage modulus and loss modulus of the PCL/MWNT nanocomposites. The nonisothermal crystallization behavior of the PCL/MWNT nanocomposites exhibits strong dependencies of the degree of crystallinity (X_c), peak crystallization temperature (T_p), half‐time of crystallization (t_1/2) and Avrami exponent (n) on the MWNT content and cooling rate. The MWNTs in the PCL/MWNT nanocomposites exhibit a higher nucleation activity. The crystallization activation energy (E_a) calculated with the Kissinger model is higher when a small amount of MWNTs is added, then gradually decreases; all the E_a values are higher than that of pure PCL. CONCLUSION: This paper reports for the first time the preparation of high‐performance biopolymer PCL/MWNT nanocomposites prepared by a simple melt‐compounding method. The results show that the PCL/MWNT nanocomposites can broaden the applications of PCL. Copyright © 2008 Society of Chemical Industry     

Effect of Thermal History on Structural Changes in Melt‐Intercalated Poly(ε‐caprolactone)/Organoclay Nanocomposites Investigated by Dynamic Viscoelastic Relaxation Measurements

Poly(ε‐caprolactone) (PCL) nanocomposites were prepared using two different types of organically modified nanosilicates by melt intercalation with an internal mixer. Dynamic mechanical analysis revealed possible structural changes in the nanocomposites even during the small deformation occurring during shear oscillatory measurements, as evidenced by a V‐shaped modulus change in the plot of the dynamic storage modulus as a function of stepwise increased temperature. X‐ray diffraction patterns were recorded at different simulated temperatures during the various stages of dynamic measurements. The X‐ray data indicate that the structural changes can be ascribed to a further intercalation of the PCL matrix chains into the silicate layers. This further intercalation is a consequence of the heat treatment during the dynamic mechanical measurements. Furthermore, there is a considerable vertical shift in addition to the horizontal shift in the higher temperature regime, which allows the mapping of a master curve through the application of the time‐temperature superposition principle to the dynamic storage and the loss modulus data obtained at various isothermal temperatures. The present study is also concerned with the relative molecular mobility of both PCL nanocomposites in the given experimental conditions considering the Williams‐Landel‐Ferry (WLF) equation and the Arrhenius relationship between the horizontal shift factor and the activation energy of flow. Moreover, the extent of the vertical shift as a function of temperature made it possible to determine the apparent activation energy of the further intercalation of PCL into the silicate layers. This intercalation is caused by the additional exposure to heat during the dynamic mechanical measurements after mixing, which led to a comparison of the relative diffusivity of the PCL matrix in the two nanocomposites.

Dynamic shear storage moduli G′ of PCLOC25A and PCLOC30B as a function of temperature with increase increments of 20 °C from 60 to 260 °C. The G′ data were obtained from isothermal frequency sweep G′(ω) data at ω = 1 rad · s^?1 at the corresponding temperatures.     

Mechanically reinforced biodegradable nanocomposites. A facile synthesis based on PEGylated silica nanoparticles

Biodegradable nanocomposites consisting of poly(?-caprolactone) (PCL) reinforced by PEGylated silica (polyethylene-glycol/SiO₂) nanoparticles were prepared by a melt-extrusion process. The PEGylated silica nanoparticles were prepared in a facile, one-pot synthesis process. Transmission electron microscopy (TEM) observations of the PEGylated silica nanoparticles inside the PCL matrix indicated that a homogeneous dispersion had been achieved. As a result, the storage modulus (E′) in the rubbery plateau increased significantly with the filler contents at all temperatures studied, at values approximately 45% higher than the neat PCL, at a loading level of only 4 wt.%. In comparison, in the absence of polyethylene-glycol (PEG) the silica nanoparticles formed aggregates inside the PCL matrix, and the reinforcement was negligible. The results from X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR) analyses identified the location of the PEG at the PCL/silica interface.     

BCE/BMI/Nano-SiO_2复合材料的性能研究

采用熔融共混法制备了氰酸(酯BCE/)双马来酰亚胺预聚(体BMI)/纳米二氧化(硅nano-SiO2)复合材料,研究了nano-SiO2用量对复合材料耐热性能、静态力学性能和动态力学性能的影响,并利用扫描电镜分析了nano-SiO2在聚合物基体中的分散情况。结果表明:随着nano-SiO2用量的增加,BCE/BMI/nano-SiO2复合材料的冲击强度和弯曲强度均是先升后降,冲击强度、弯曲强度和储能模量均在nano-SiO2含量为2%时达到最大值;nano-SiO2的加入可以提高复合材料的耐热性,但随其用量的增加,nano-SiO2在基体中的分散性逐渐变差。     

Nanocomposites of PBAT and cellulose nanocrystals modified by in situ polymerization and melt extrusion

Cellulose nanocrystals (CNC) were successfully grafted with a low molecular weight poly(butylene glutarate) through an in situ polymerization procedure. The grafting treatment decreased the CNC hydrophilic character and increased the onset of their thermal degradation by approximately 20°C, thus increasing the possibilities of CNC application. Composites of grafted and nongrafted CNC with a poly(butylene‐adipate‐co‐terephthalate) (PBAT) matrix were prepared by melt extrusion. The CNC addition led to an increase of 50% of the tensile elastic modulus of the PBAT. In addition, dynamic mechanical thermal analysis showed that the composite with CNC retained its high modulus even at temperatures far above the glass transition temperature of PBAT. At 60°C the storage modulus of the composite with CNC was approximately 200% higher than that of the pure PBAT. Thus, in this work, nanocomposites of improved properties were obtained through a combination of in situ polymerization and melt extrusion. POLYM. ENG. SCI., 56:1339–1348, 2016. © 2016 Society of Plastics Engineers     

Preparation of high-modulus poly(ethylene terephthalate) fibers by vibrating hot drawing

A novel drawing method, vibrating hot drawing, was successfully applied to poly(ethylene terephthalate) fiber, which has a normal molecular weight (IV = 0.7 dL/g) and was prepared by melt spinning. The process was divided into three steps, with differing conditions in drawing temperature, applied tension, vibrating frequency, and amplitude. The drawing temperature and vibration frequency were decided by considering the α_a dispersion of the polymer. In spite of a low draw ratio (7.7) and a low crystallinity (0.55), the birefringence and dynamic storage modulus at room temperature of the 3rd-step fiber reached 0.260 and 36 GPa, respectively. The modulus remains at a high level at elevated temperatures, for example, 29 GPa at 100°C and 17 GPa at 200°C. Further, it was found from temperature and intensity of the α_a dispersion peak that the movements of amorphous chains are strongly inhibited. © 1996 John Wiley & Sons, Inc.     

Preparation of Poly(Vinyl Alcohol) Nanocomposite Films Reinforced with Poly(Amide–Imide)/CuO Having N-trimellitylimido-L-valine Linkages for the Improvement of Mechanical and Thermal Properties

In this investigation, nanocomposite films were fabricated by dispersion of poly(amide–imide)/CuO nanocomposites as nanofiller in the poly(vinyl alcohol) matrix via an ultrasonic process. The nanofiller was prepared and mixed with PVA matrix. After dispersion of nanofiller into the poly(vinyl alcohol), the mechanical properties of the nanocomposites were improved. For example, the addition of 6 wt% nanofiller into the poly(vinyl alcohol) matrix enhanced the tensile modulus by 39%. The residual weight at 800°C was 7% for pure poly(vinyl alcohol) while the nanocomposites illustrated 12–19% residue at this temperature.     

In situ composites from blends of polycarbonate and a thermotropic liquid‐crystalline polymer: The influence of the processing temperature on the rheology,morphology, and mechanical properties of injection‐molded microcomposites

This work was aimed at understanding how the injection‐molding temperature affected the final mechanical properties of in situ composite materials based on polycarbonate (PC) reinforced with a liquid‐crystalline polymer (LCP). To that end, the LCP was a copolyester, called Vectra A950 (VA), made of 73 mol % 4‐hydroxybenzoic acid and 27 mol % 6‐hydroxy‐2 naphthoic acid. The injection‐molded PC/VA composites were produced with loadings of 5, 10, and 20 wt % VA at three different processing barrel temperatures (280, 290, and 300°C). When the composite was processed at barrel temperatures of 280 and 290°C, VA provided reinforcement to PC. The resulting injection‐molded structure had a distinct skin–core morphology with unoriented VA in the core. At these barrel temperatures, the viscosity of VA was lower than that of PC. However, when they were processed at 300°C, the VA domains were dispersed mainly in spherical droplets in the PC/VA composites and thus were unable to reinforce the material. The rheological measurements showed that now the viscosity of VA was higher than that of PC at 300°C. This structure development during the injection molding of these composites was manifested in the mechanical properties. The tensile modulus and tensile strength of the PC/VA composites were dependent on the processing temperature and on the VA concentrations. The modulus was maximum in the PC/VA blend with 20 wt % VA processed at 290°C. The Izod impact strength of the composites tended to markedly decrease with increasing VA content. The magnitude of the loss modulus decreased with increasing VA content at a given processing temperature. This was attributed to the anisotropic reinforcement of VA. Similarly, as the VA content increased, the modulus and thus the reinforcing effect were improved comparatively with the processing temperature increasing from 280 to 290°C; this, however, dropped in the case of composites processed at 300°C, at which the modulus anisotropy was reduced. Dynamic oscillatory shear measurements revealed that the viscoelastic properties, that is, the shear storage modulus and shear loss modulus, improved with decreasing processing temperatures and increasing VA contents in the composites. Also, the viscoelastic melt behavior (shear storage modulus and shear loss modulus) indicated that the addition of VA changed the distribution of the longer relaxation times of PC in the PC/VA composites. Thus, the injection‐molding processing temperature played a vital role in optimizing the morphology‐dependent mechanical properties of the polymer/LCP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical and Thermal Properties of Poly(phthalazinone biphenyl ether sulfone)/PEEK Blends

A series of blends with various compositions are prepared by melt extrusion on the basis of novel copoly(phthalazinone biphenyl ether sulfone) (PPBES) and poly(ether ether ketone) (PEEK). The melt flowability, mechanical and thermal properties of the blends are studied. The results show that the incorporated PEEK has a large influence on the melt viscosity and thermal stability of blends. The tensile strength of the blends remains at about 90 MPa at room temperature; PPBES improves the mechanical properties of PEEK at 150°C. The flexural strength and modulus of the PPBES/PEEK blends also increase with the addition of PEEK.