The morphology and degradation behavior of electrospun poly(3‐hydroxybutyrate)/Magnetite and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/Magnetite composites

Electrospinning of biodegradable poly(3‐hydroxybutyrate) (PHB)/magnetite and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/magnetite composites in 2,2,2‐trifluoroethanol (TFE) and chloroform are investigated to develop nonwoven nanofibrous structure. Ultrafine PHB/magnetite fibers are obtained and the resulting fiber diameters are in the range of 690–710 nm and 8.0–8.4 µm for the polymer dissolved in TFE and chloroform. The surface of PHB composites fiber fabricated in chloroform contains porous structures, which are not observed for the sample of PHB composites fiber dissolved in TFE. The fiber diameters for PHBV5/magnetite composites are in the range of 500–540 nm and 2.3–2.5 µm, depending on the use of TFE and chloroform. The average diameters of PHBV5/magnetite composite fibers are smaller than those of PHB/magnetite composites fiber. All electrospun PHB/magnetite and composite fibers are superparamagnetic. The degradation behaviors of PHB/magnetite and PHBV5/magnetite composite fibers were investigated using Caldimonas manganoxidans. For the fabricated composite fibers, it is found that the degradation rate increased with the increasing loading of magnetite nanoparticles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41070.     

Wood‐fiber‐reinforced poly(lactic acid) composites: Evaluation of the physicomechanical and morphological properties

This article presents the results of a study of the processing and physicomechanical properties of environmentally friendly wood‐fiber‐reinforced poly(lactic acid) composites that were produced with a microcompounding molding system. Wood‐fiber‐reinforced polypropylene composites were also processed under similar conditions and were compared to wood‐fiber‐reinforced poly(lactic acid) composites. The mechanical, thermomechanical, and morphological properties of these composites were studied. In terms of the mechanical properties, the wood‐fiber‐reinforced poly(lactic acid) composites were comparable to conventional polypropylene‐based thermoplastic composites. The mechanical properties of the wood‐fiber‐reinforced poly(lactic acid) composites were significantly higher than those of the virgin resin. The flexural modulus (8.9 GPa) of the wood‐fiber‐reinforced poly(lactic acid) composite (30 wt % fiber) was comparable to that of traditional (i.e., wood‐fiber‐reinforced polypropylene) composites (3.4 GPa). The incorporation of the wood fibers into poly(lactic acid) resulted in a considerable increase in the storage modulus (stiffness) of the resin. The addition of the maleated polypropylene coupling agent improved the mechanical properties of the composites. Microstructure studies using scanning electron microscopy indicated significant interfacial bonding between the matrix and the wood fibers. The specific performance evidenced by the wood‐fiber‐reinforced poly(lactic acid) composites may hint at potential applications in, for example, the automotive and packaging industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4856–4869, 2006     

Micromechanical analysis of long fiber‐reinforced composites with nanoparticle incorporation into the interphase region

The influence of the distribution type, Young's modulus, and volume fraction of the nanoparticles within the interphase region on the mechanical behavior of long fiber‐reinforced composites with epoxy resin matrix under transverse tensile loading is investigated in this article. An infinite material containing unidirectional long fiber and periodic distribution of elastic, spherical nanoparticles was modeled using a unit cell approach. A stiffness degradation technique has been used to simulate the damage and crack progress of the matrix subjected to mechanical loading. A series of computational experiments performed to study the influence of the nanoparticle indicate that the mechanical properties, nanoparticle‐fiber distance, and volume fraction of nanoparticle have a significant effect on both the stiffness and strength properties of these composite materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41573.     

Toward environment‐friendly composites of poly(ε‐caprolactone) reinforced with stereocomplex‐type poly(l‐lactide)/poly(d‐lactide)

In this work, stereocomplex‐poly(l ‐ and d ‐lactide) (sc‐PLA) was incorporated into poly(ε‐caprolactone) (PCL) to fabricate a novel biodegradable polymer composite. PCL/sc‐PLA composites were prepared by solution casting at sc‐PLA loadings of 5–30 wt %. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) demonstrated the formation of the stereocomplex in the blends. DSC and WAXD curves also indicated that the addition of sc‐PLA did not alter the crystal structure of PCL. Rheology and mechanical properties of neat PCL and the PCL/sc‐PLA composites were investigated in detail. Rheological measurements indicated that the composites exhibited evident solid‐like response in the low frequency region as the sc‐PLA loadings reached up to 20 wt %. Moreover, the long‐range motion of PCL chains was highly restrained. Dynamic mechanical analysis showed that the storage modulus (E′) of PCL in the composites was improved and the glass transition temperature values were hardly changed after the addition of sc‐PLA. Tensile tests showed that the Young's modulus, and yield strength of the composites were enhanced by the addition of sc‐PLA while the tensile strength and elongation at break were reduced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40208.     

Modification of poly(3‐hydroxybutyrate)‐co‐poly(3‐hydroxyvalerate) with natural rubber

Composites of poly(3‐hydroxybutyrate)‐co‐poly(3‐hydroxyvalerate) (PHBHV) with 6% of 3‐hydroxyvalerate (HV) and natural rubber (NR) were prepared by a solvent‐casting method. Different approaches were tested for the composite preparation. Both PHBHV and NR were dissolved in chloroform, followed by its evaporation, giving various layers. The mechanical properties and morphology of the obtained composites were evaluated by tensile tests and scanning electron microscopy (SEM), respectively. The obtained results demonstrated that the final composite has excellent mechanical properties when compared with PHBHV. SEM analysis unequivocally showed the excellent adhesion between the two polymeric layers. This new material was also tested as a drug delivering system using flurbiprofen as a model drug, and then the diffusion coefficients were determined. This article describes an easy method to produce a desirable composite from PHBHV and NR. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of starch predrying on the mechanical properties of starch/poly(ε‐caprolactone) composites

This study describes the effect of predrying sago starch, a tropical starch, on the resultant mechanical properties of starch/poly(ε‐caprolactone) composite materials. Sago starch was dried to less than a 1% moisture level in a vacuum oven and dispersed into a polycaprolactone matrix with an internal mixer at 90°C. The mechanical properties of the composite were studied according to methods of the Association for Standards, Testing, and Measurement, whereas the morphology was monitored with scanning electron microscopy. The properties were compared with a composite obtained with native starch containing 12% moisture. The results indicated that predrying the starch led to a lower property drop rate in the composite as the starch content increased. The elastic modulus, tensile strength, and elongation at break were higher than those obtained when starch was used without predrying. The morphology observed during scanning electron microscopy studies was used to explain the observed trends in the mechanical properties. In this way, a relatively simple and cost‐effective method was devised to increase the starch loading in the polycaprolactone matrix to obtain properties within the useful range of mechanical properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 877–884, 2003     

Poly(ε‐caprolactone) composites containing gentamicin‐loaded β‐tricalcium phosphate/gelatin microspheres as bone tissue supports

In this work, novel antibacterial composites were prepared by using poly(ε‐caprolactone) (PCL) as the main matrix material, and gentamicin‐loaded microspheres composed of β‐tricalcium phosphate (β‐TCP) and gelatin. The purpose is to use this biodegradable material as a support for bone tissue. This composite system is expected to enhance bone regeneration by the presence of β‐TCP and prevent a possible infection that might occur around the defected bone region by the release of gentamicin. The effects of the ratio of the β‐TCP/gelatin microspheres on the morphological, mechanical, and degradation properties of composite films as well as in vitro antibiotic release and antibacterial activities against Escherichia coli and Staphylococcus aureus were investigated. The results showed that the composites of PCL and β‐TCP/gelatin microspheres had antibacterial activities for both bacteria. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(ε‐caprolactone) composite scaffolds loaded with gentamicin‐containing β‐tricalcium phosphate/gelatin microspheres for bone tissue engineering applications

In this study, novel poly(ε‐caprolactone) (PCL) composite scaffolds were prepared for bone tissue engineering applications, where gentamicin‐loaded β‐tricalcium phosphate (β‐TCP)/gelatin microspheres were added to PCL. The effects of the amount of β‐TCP/gelatin microspheres added to the PCL scaffold on various properties, such as the gentamicin release rate, biodegradability, morphology, mechanical strength, and pore size distribution, were investigated. A higher amount of filler caused a reduction in the mechanical properties and an increase in the pore size and led to a faster release of gentamicin. Human osteosarcoma cells (Saos‐2) were seeded on the prepared composite scaffolds, and the viability of cells having alkaline phosphatase (ALP) activity was observed for all of the scaffolds after 3 weeks of incubation. Cell proliferation and differentiation enhanced the mechanical strength of the scaffolds. Promising results were obtained for the development of bone cells on the prepared biocompatible, biodegradable, and antimicrobial composite scaffolds. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40110.     

Anomalous impact strength for layered double hydroxide‐palmitate/poly(ε‐caprolactone) nanocomposites

Inherent physical properties and commercial availability makes poly(ε‐caprolactone) (PCL) very attractive as a potential substitute material for nondegradable polymers for commodity applications. However, a balance of toughness and stiffness is needed in order to transfer this potential into reality, particularly for short‐term packaging applications. In this context, layered double hydroxide modified with palmitic acid (LDH‐palmitate), was used as a nanoadditive to enhance the mechanical properties of PCL. Composites from PCL were prepared by melt‐blending with LDH‐palmitate loadings in the 1?10 wt % range. Scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction were used to study the structure and morphology of the composites. The results showed homogeneous dispersion of clay particles in composites, but the degree of stacking of clay platelets was related to the LDH‐palmitate loadings. Charpy impact test measurements revealed an anomalous toughness improvement in the case of composite containing 5 wt % LDH‐palmitate, attributed to a combination of microcavitation and changes in crystallite sizes in the composite. The addition of LDH‐palmitate improved the water vapor barrier permeation of neat PCL film. In summary, LDH‐palmitate was shown to have potential as a nanoadditive to obtain tougher LDH‐PCL composite with improved barrier property. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41109.     

On mechanical properties of sago starch/poly(ε‐caprolactone) composites

Four types of sago starch were incorporated into a poly(ε‐caprolactone) (PCL) matrix, native, predried, thermoplastic starch (TPS) granules and TPS. All systems were found to be phase‐separated. Tensile properties were obtained after formulation of various mixtures and processing of suitable test specimens. It was found that elongation at break of composites comprising native starch and thermoplastic starch decreases almost linearly with volume fraction of starch whereas tendencies to nonlinear dependencies were observed for predried and thermoplastic starch granules. Except for composites containing native starch, tensile strength was found to decrease linearly with volume fraction of starch. However, statistical analysis of the corresponding regression coefficients shows that the coefficients ruling the compostion dependence of tensile properties are not significantly different for the four starch types. One may conclude that in all cases, tensile properties decrease almost linearly with volume fraction and maximum volume fraction of starch loading is around 0.6. Scanning electron micrographs of fracture surfaces revealed weak interfacial adhesion between sago starch and the polymer matrix.     

Preparation and properties of biocomposites based on jute fibers and blend of plasticized starch and poly(β‐hydroxybutyrate)

In this work, preparation and properties of biocomposites based on jute fibers and blend of plasticized starch and poly(β‐hydroxybutyrate) (PHB) have been investigated. Different amounts of glycerol and aliphatic polyesters (PHB) have been added to native starch to obtain a processable biodegradable matrix. In the same way natural jute fibers up to 30 wt % loading were added to improve the mechanical and thermal stability of the material. Tensile mechanical, thermal, and thermomecahnical analyses have been performed to characterize the ensuing materials. Significant enhancement in the mechanical properties and water sensitivity were noted by the addition of 8 wt % PHB. The fibers incorporation into the biopolymer matrix brings about an increase in both the mechanical strength and modulus as much higher as the fibers loading is important. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Blends of poly(3‐hydroxybutyrate) with poly(β‐alanine) and its derivatives

Nanofibers and films of poly(3‐hydroxybutyrate) (PHB)/nylon 3 [poly(β‐alanine) (N3)], PHB/poly(α‐methyl‐β‐alanine) (2mN3), and PHB/poly(β‐methyl‐β‐alanine) (3mN3) blends were prepared by electrospinning and film‐casting techniques, respectively. The miscibility of the blends was studied by Fourier transform infrared spectrometry, differential scanning calorimetry, thermogravimetric analysis, and X‐ray diffraction (XRD). The electrospinnability of the blends was studied by scanning electron microscopy. Some characteristic IR absorption bands of the components in the blends shifted gradually with changes in the compositions. The melting temperature and decomposition temperature of PHB decreased gradually with increasing fractions of N3, 2mN3, and 3mN3. The XRD spectra of all of the blends exhibited peaks with lower intensities compared to those of the neat species. The suppression of PHB crystallinity in the blends after blending was attributed to the disruption of its crystal lattice and the prevention of recrystallization of each component by means of other components and segmental interactions between the components in the amorphous phase. Thermal, spectroscopic, and optical analyses of the polymer blends revealed that the polymers were miscible with good compatibility, and this could have improved the scaffold properties of PHB. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40484.     

Preparation,characterization, and mechanical properties of poly(ε‐caprolactone)/polylactic acid blend composites

Mechanical properties of poly(ε‐caprolactone) (PCL) and polylactic acid (PLA) blend reinforced with Dura and Tenera palm press fibers were studied. Dicumyl peroxide (DCP) was used as compatibilizer in the blend composites. Fourier transforms infrared spectrophotometer (FTIR) and field emission scanning electron microscope (FESEM) was used to study the effect of treatment on the fibers and fiber/matrix adhesion respectively. The uncompatibilized blend composites exhibited higher Young's modulus than the compatibilized blend composites. Impact strength of compatibilized blend composites of Tenera fibers (FM) increased by 161% at 10 wt% fiber load more than the uncompatibilized blend composites at same fiber load. The Dura fibers (FN) enhanced impact strength by 133% at 10 wt% fiber load. Tensile strength increased by 40% for compatibilized FM blend composites. In conclusion, it was observed that DCP incorporation resulted in good interfacial adhesion as revealed by the FESEM micrographs and evidenced in the improved mechanical properties. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Surface‐modified pliable PDLLA/PCL/β‐TCP scaffolds as a promising delivery system for bone regeneration

Surface‐modified poly(d , l ‐lactide)/polycaprolactone/β‐tricalcium phosphate complex scaffold was fabricated in this study and we hypothesized that pliable and mechanical strong scaffold would be achieved by regulation of ternary compositions; while superficial modification strategy conduced to preserve and controlled‐release of bioactive growth factors. Properties of the composite scaffolds were systematically investigated, including mechanical properties, surface morphology, porosity, wettability, and releasing behavior. Moreover, the representative cytokine, recombinant human bone morphogenetic protein‐2 (rhBMP‐2), was loaded and implanted into muscular pouch of mouse to assess bone formation in vivo. Improved osteogenesis was achieved ascribed to both amplified β‐tricalcium phosphate (β‐TCP) content and retarded initial burst release. Particularly, scaffold doped with hydroxypropyl methylcellulose (HPMC) displayed optimal osteogenic capability. The results indicated that the PDLLA/PCL/β‐TCP complex scaffold along with HPMC‐coating and rhBMP‐2 loading was a promising candidate for bone regeneration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40951.     

Kenaf fiber/poly(ε‐caprolactone) biocomposite with enhanced crystallization rate and mechanical properties

Plant‐derived kenaf fiber (KF)‐reinforced poly(ε‐caprolactone) (PCL) biocomposites were successfully fabricated by the melt mixing technique. The crystallization behavior, morphology, and mechanical and dynamic mechanical properties of PCL/KF composites with various KF weight contents were investigated. The crystallization rate, tensile and storage moduli significantly improved as compared to the virgin polymer. The half times of PCL/KF composite (20 wt % fiber content) in isothermal crystallization at 40°C and 45°C reduced to 31.6% and 42.0% of the neat PCL, respectively. Moreover, the tensile and storage modulus of the composite are improved by 146% and 223%, respectively, by the reinforcement with 30% KF. The morphology evaluated by SEM indicates good dispersion and adhesion between KF and PCL. Overall, these findings reveal that KF can be a potential reinforcement for the biodegradable polymer composites owing to its good ability to improve the mechanical properties as well as crystallization rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Concentration effect of γ‐glycidoxypropyltrimethoxysilane on the mechanical properties of glass fiber–epoxy composites

In this study, glass fibers were modified using γ‐glycidoxypropyltrimethoxysilane of different concentrations to improve the interfacial adhesion at interfaces between fibers and matrix. Effects of γ‐glycidoxypropyltrimethoxysilane on mechanical properties and fracture behavior of glass fiber/epoxy composites were investigated experimentally. Mechanical properties of the composites have been investigated by tensile tests, short beam tests, and flexural tests. The short‐beam method was used to measure the interlaminar shear strength (ILSS) of laminates. The tensile and flexural properties of composites were characterized by tensile and three‐point bending tests, respectively. The fracture surfaces of the composites were observed with a scanning electron microscope. On comparing the results obtained for the different concentrations of silane solution, it was found that the 0.5% GPS silane treatment provided the best mechanical properties. The ILSS value of heat‐cleaned glass fiber reinforced composite is enhanced by ∼59% as a result of the glass fiber treatment with 0.5% γ‐GPS. Also, an improvement of about 37% in tensile strength, about 78% in flexural strength of the composite with the 0.5% γ‐GPS treatment of glass fibers was observed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Poly(lactic acid)–thermoplastic poly(ether)urethane composites synergistically reinforced and toughened with short carbon fibers for three‐dimensional printing

In this study, we prepared short‐carbon‐fiber (CF)‐reinforced poly(lactic acid) (PLA)–thermoplastic polyurethane (TPU) blends by melt blending. The effects of the initial fiber length and content on the morphologies and thermal, rheological, and mechanical properties of the composites were systematically investigated. We found that the mechanical properties of the composites were almost unaffected by the fiber initial length. However, with increasing fiber content, the stiffness and toughness values of the blends were both enhanced because of the formation of a TPU‐mediated CF network. With the incorporation of 20 wt % CFs into the PLA–TPU blends, the tensile strength was increased by 70.7%, the flexural modulus was increased by 184%, and the impact strength was increased by 50.4%. Compared with that of the neat PLA, the impact strength of the CF‐reinforced composites increased up to 1.92 times. For the performance in three‐dimensional printing, excellent mechanical properties and a good‐quality appearance were simultaneously obtained when we printed the composites with a thin layer thickness. Our results provide insight into the relationship among the CFs, phase structure, and performance, as we achieved a good stiffness–toughness balance in the PLA–TPU–CF ternary composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46483.     

Facile synthesis and antibacterial evaluation of poly(acrylamide‐co‐(β‐cyclodextrin))/silver nanocomposite

Hydrogel/silver nanocomposites have shown immense potential in many biological applications. In this article, a facile method to synthesize poly(acrylamide‐co‐(β‐cyclodextrin))/silver nanocomposites is reported. The silver nanoparticles were in situ synthesized accompanying with the formation of poly(acrylamide‐co‐(β‐cyclodextrin)) hydrogel by gamma irradiation without additional reducing and stabilizing agents. In addition, the nanocomposites were prepared under ambient conditions. The formation of silver nanoparticles was confirmed by ultraviolet used to characterize the structure and composition of the synthetic nanocomposites. Transmission electron microscope verified the formation and homogeneous distribution of silver nanoparticles in the hydrogel matrix. The hybrid hydrogel exhibited excellent water‐swelling properties, which could be controlled by varying the mass ratio of acrylamide (AM) to β‐cyclodextrin (β‐CD) in the hydrogel. Furthermore, the poly(acrylamide‐co‐(β‐cyclodextrin))/silver nanocomposites were found to be effective in inhibiting the growth of both Gram‐negative Escherichia coli and Gram‐positive Staphylococcus aureus. POLYM. COMPOS., 37:1480–1487, 2016. © 2014 Society of Plastics Engineers     

Improvement of interfacial adhesion of poly(m‐phenylene isophthalamide) short fiber–thermoplastic elastomer (SEBS) composites by N‐alkylation on fiber surface

A composite of short‐fiber, poly(m‐phenylene isophthalamide), and thermoplastic elastomer styrene (ethylene–butylene) styrene (SEBS), was investigated. The fiber surface was modified by N‐alkylation (heptylation and dodecylation) to improve their compatibility with a less polar SEBS matrix. Observation of fiber‐surface morphology by SEM revealed surface roughness after N‐alkylation. Nearly complete coating of the polymer matrix on the fiber was observed on a fractured surface of the composite, which is evidence for the improvement of fiber–matrix adhesion. It was found that the modulus of the composites grew with increasing fiber loading to approximately the same extent for both unmodified and modified fiber composites. Tensile strength of the modified fiber composites was found to improve significantly over that of the unmodified fiber composite. This suggests that the presence of the alkyl group on the fiber surface is responsible for an improvement of interfacial adhesion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2414–2422, 1999     

Preparation of β‐SiCw/BDM/DBA composites with excellent comprehensive properties

Functionalized β‐SiC whiskers (β‐SiCw) are employed to prepare β‐SiCw/N,N′‐4, 4′‐bimaleimide diphenyl methane/diallylbisphenol A (β‐SiCw/BDM/DBA) composites via powder blending‐casting method. The thermal conductive coefficient of the β‐SiCw/BDM/DBA composites is 0.994 W/mK with 40 wt% functionalized β‐SiCw, five times higher than that of pure BDM/DBA. The mechanical properties of the β‐SiCw/BDM/DBA composites are optimal with 10 wt% functionalized β‐SiCw. Both thermal resistance and dielectric constant are increased with the increasing addition of β‐SiCw. For a given β‐SiCw loading, the surface functionalization of β‐SiCw exhibits a positive effect on the thermal conductivities and mechanical properties of the β‐SiCw/BDM/DBA composites. POLYM. COMPOS., 35:1875–1878, 2014. © 2014 Society of Plastics Engineers