Synthesis,thermal, and rheological properties of poly(trimethylene terephthalate)/BaSO4 nanocomposites

A novel method was developed for fabricating poly(trimethylene terephthalate) (PTT)/BaSO₄ nanocomposites using in situ polymerization. A nano‐BaSO₄ suspension was prepared by reacting H₂SO₄ with Ba(OH)₂ in 1,3‐propanediol (PDO). The mean size of original nano‐BaSO₄ is 15–23 nm. PTT matrix was synthesized by condensation polymerization of bis(3‐hydroxypropyl terephthalate) after the completion of transesterification of dimethyl terephthalate (DMT) with PDO. It was found that the addition of BaSO₄ had little influence on the synthesis of PTT. The properties of nanocomposites with a wide range of BaSO₄ fraction were systematically studied. The morphologies of the composites were investigated by transmission electron microscopy (TEM), which showed that agglomerate structures did not form until BaSO₄ content higher than 8 wt%. The thermal properties of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results revealed that the triple endothermic melting phenomenon is only observed for the nanocomposites which contained 4 wt% BaSO₄, other samples exhibit double endothermic melting. These results indicated that nano‐BaSO₄ could induce a microcrystal to form more perfect morphology and restrain the formation of much thicker lamellar crystallinity, that is, nano‐BaSO₄ could induce the formation of more uniform crystallinity. Besides, the crystallization ability of the composites was greatly improved by loading nano‐BaSO₄. The TGA results suggested that nano‐BaSO₄ slightly increased the maximum‐decomposing‐rate temperature 1 (T_max1), but markedly increased the maximum‐decomposing‐rate temperature 2 (T_max2). Furthermore, the steady‐state shear behavior of samples was investigated by a parallel‐plate rheometer. The storage modulus (G') and loss modulus (G”) curves shifted to higher modulus upon addition of 2–16 wt% of nano‐BaSO₄. All of the samples investigated exhibited the expected shear‐thinning behavior. Proper contents of nano‐BaSO₄ would decrease the shear viscosity of nanocomposites, whereas superfluous amounts would greatly increase the viscosity of nanocomposites and the composites which loaded 8 wt% nano‐BaSO₄ revealed an equivalent shear viscosity compared to pure PTT. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of HMWCNT/PLLA nanocomposite scaffolds for application in nerve tissue engineering and evaluation of their physical,mechanical and cellular activity properties

This study was aimed to prepare biodegradable and porous nanocomposite scaffolds with microtubular orientation structure as a model for nerve tissue engineering by thermally induced phase separation (TIPS) method using dioxane as the solvent, crystalline poly (L‐lactic acid) (PLLA) and multi‐walled carbon nanotubes (MWCNTs). In order to overcome dispersion of MWCNTs in the PLLA matrix, heparinization of MWCNTs was performed. Solvent crystallization, oriented structure, the mean pore diameter and porosity percentage of the scaffolds were controlled by fundamental system parameters including temperature‐gradient of the system, polymer solution concentration and carbon nanotube content. Scanning Electron Microscopy (SEM), ImageJ, software and dynamic mechanical thermal analysis (DMTA) were used to investigate the structural and mechanical properties. TEM observation was carried out for characterization of nanotube dispersion in PLLA. It was found that the scaffolds containing heparinized multi‐walled carbon nanotubes (HMWCNTs) exhibited higher storage modulus, better carbon nanotube (CNT) dispersion and tubular orientation structure than those with non heparinized MWCNTs. In‐vitro studies were also conducted by using murine P₁₉ cell line as a suitable model system to analyze neuronal differentiation over a 2‐week period. Immunofluorescence and DAPI staining were used to confirm the cells' attachment and differentiation on the PLLA/HMWCNT nanocomposite scaffolds. Based on the results, we can conclude that the PLLA/HMWCNT scaffolds enhanced the nerve cell differentiation and proliferation, and therefore, acted as a positive cue to support neurite outgrowth. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of nanoalumina/EPDM composites with good performance in thermal conductivity and mechanical properties

In this paper, nanoalumina (Al₂O₃) highly filled ethylene propylene diene monomer (EPDM) composites are prepared, and the mechanical (static and dynamic) properties and thermal conductivity are investigated systemically through various characterization methods. Furthermore, influences of in situ modification (mixing operation assisted by silane at high temperature for a certain time) with the silane‐coupling agent bis‐(3‐triethoxy silylpropyl)‐tetrasulfide (Si69) and stearic acid (SA) pretreatment on the nano‐Al₂O₃ filled composites are as well investigated. The results indicate that nano‐Al₂O₃ particles can not only perform well in reinforcing EPDM, but also improve the thermal conductivity significantly. Assisted by in situ modification with Si69, the mechanical properties (especially dynamic mechanical properties) of the nano‐Al₂O₃ filled composites are improved obviously, without influencing the thermal conductivity. By comparing to the traditional reinforcing fillers, such as carbon black (grade N330) and silica, in situ modified nano‐Al₂O₃ filled composites exhibit excellent performance in mechanical (static and dynamic) properties as well as better thermal conductivity, especially lower compression heat build‐up and better fatigue resistance. In general, our work indicates that nano‐Al₂O₃, as the novel thermal conductive reinforcing filler, is suitable to prepare rubber products serving in dynamic conditions, with the longer expected service life. Copyright © 2010 John Wiley & Sons, Ltd.     

Nano‐hydroxyapatite/polyamide66 composite tissue‐engineering scaffolds with anisotropy in morphology and mechanical behaviors

Based on a biomimetic conception, nano‐hydroxyapatite (n‐HA)/polyamide66 (PA66) composite scaffolds were prepared with anisotropic properties both in morphology and mechanical behavior. A novel improved thermally induced phase separation (TIPS) technique was developed to generate orientation‐structured scaffolds for tissue engineering. The physiochemical, morphological, and mechanical properties of the resultant scaffolds were evaluated. According to the results, the improved TIPS method exhibited good processability and reproducibility and enabled the composite scaffolds to have a high content of inorganic fillers. The morphological study proved that the n‐HA/PA66 scaffolds exhibited unidirectional microtubular architecture with high porosity (ca. 80–85%) and an optimal pore size ranging from 200 to 500 μm. Besides, the effect of n‐HA content on the morphology of the scaffolds was studied, and the results indicated that the obtained scaffolds presented an improvement in anisotropic morphology with increase of n‐HA content. The anisotropy was also evaluated in the mechanical properties of the scaffolds, that is, the longitudinal compressive strength and modulus were ～1.5 times of the transverse ones. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 658–669, 2009     

A “Cell‐Friendly” Window for the Interaction of Cells with Hyaluronic Acid/Poly‐l‐Lysine Multilayers

Polyelectrolyte multilayers assembled from hyaluronic acid (HA) and poly‐l ‐lysine (PLL) are most widely studied showing excellent reservoir characteristics to host molecules of diverse nature; however, thick (HA/PLL)_n films are often found cell repellent. By a systematic study of the adhesion and proliferation of various cells as a function of bilayer number “n” a correlation with the mechanical and chemical properties of films is developed. The following cell lines have been studied: mouse 3T3 and L929 fibroblasts, human foreskin primary fibroblasts VH‐Fib, human embryonic kidney HEK‐293, human bone cell line U‐2‐OS, Chinese hamster ovary CHO‐K and mouse embryonic stem cells. All cells adhere and spread well in a narrow “cell‐friendly” window identify in the range of n = 12–15. At n < 12, the film is inhomogeneous and at n > 15, the film is cell repellent for all cell lines. Cellular adhesion correlates with the mechanical properties of the films showing that softer films at higher “n” number exhibiting a significant decrease of the Young's modulus below 100 kPa are weakly adherent to cells. This trend cannot be reversed even by coating a strong cell‐adhesive protein fibronectin onto the film. This indicates that mechanical cues plays a major role for cell behavior, also in respect to biochemical ones.     

Mechanical and anti‐stabbing properties of modified thermoplastic polymers impregnated multiaxial p‐aramid fabrics

New forms of hybrid multiaxial nanocomposites with enhanced mechanical and stab resisting properties are presented. This study is motivated by the lack of knowledge in the study of the multiaxial fabric nanocomposites with two modified thermoplastic matrices for antiballistic protection. Introduction of 5 wt.% silica nanoparticles in the composite of polyurethane/p‐aramid/poly (vinyl butyral) leads to significant improvement in mechanical properties, and the addition of silane as a coupling agents and glutaraldehyde as a crosslinking agents yielded maximal values of storage modulus, tensile modulus and anti‐stabbing properties for hybrid nanocomposites. Ballistic resistance testing and penetration depth of the hybrid nanocomposites were visualized using image analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of Organic Nano Carboncapsule Incorporated Modified Clay on Fire‐Retardancy of PMMA Nanocomposites

Here we investigate a new type of highly flame retardant poly(methyl methacrylate) (PMMA) nanocomposite by bulk polymerization of methyl methacrylate (MMA) in the presence of organic nano carboncapsule (OCNC/NCNC)‐incorporated modified montmorillonites (CL120, CL42). The morphology of the modified clay was confirmed by X‐ray diffraction (XRD), and Fourier transform infrared (FT‐IR) spectroscopy was used to identify the functional groups in the clay. The nano morphological characterization of the clay in the PMMA matrix was confirmed by XRD and transmission electron microscopy (TEM). The thermal and mechanical properties of the PMMA nanocomposites were investigated by thermogravimetry and dynamic mechanical analysis, respectively. PMMA containing organo nano carboncapsule‐doped CL42 modified cocoamphodipropionate (K2) (P‐O‐CL42) could achieve very high thermal stability compared to pristine PMMA. The 5% thermal decomposition temperature (T _5d) increased by 63.2°C. Storage modulus of PMMA nanocomposites measured by DMA analysis. An enhancement of storage modulus and significant reduction in the peak heat release (PHR) rate were observed in the almost all PMMA nanocomposites as compared to pristine PMMA. Moreover, these results suggest that PMMA nanocomposites can have potential applications in the building industry and the medical field.     

Fabrication of poly(lactide‐co‐glycolide) scaffold embedded spatially with hydroxyapatite particles on pore walls for bone tissue engineering

Poly(lactide‐co‐glycolide) (PLGA) scaffolds embedded spatially with hydroxyapatite (HA) particles on the pore walls (PLGA/HA‐S) were fabricated by using HA‐coated paraffin spheres as porogens, which were prepared by Pickering emulsion. For comparisons, PLGA scaffolds loaded with same amount of HA particles (2%) in the matrix (PLGA/HA‐M) and pure PLGA scaffolds were prepared by using pure paraffin spheres as porogens. Although the three types of scaffolds had same pore size (450–600 µm) and similar porosity (90%–93%), the PLGA/HA‐S showed the highest compression modulus. The embedment of the HA particles on the pore walls endow the PLGA/HA‐S scaffold with a stronger ability of protein adsorption and mineralization as well as a larger mechanical strength against compression. In vitro culture of rat bone marrow stem cells revealed that cell morphology and proliferation ability were similar on all the scaffolds. However, the alkaline phosphatase activity was significantly improved for the cells cultured on the PLGA/HA‐S scaffolds. Therefore, the method for fabricating scaffolds with spatially embedded nanoparticles provides a new way to obtain the bioactive scaffolds for tissue engineering. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation,characterization, and mechanical properties of microcellular poly(aryl ether ketone) foams

High‐performance microcellular closed‐cell foams were prepared by a two‐stage batch foaming process from fluorinated poly(ether ether ketone) and characterized by scanning electronic microscopy, tensile, and dynamic mechanical analysis (DMA). The effects of saturation pressure and temperature on the cell size, cell density, and bulk density of porous materials had been discussed. The resulting materials had average cell diameters in the range 3–17 μm, and cell densities (N_f) in the order of 0.6 × 10⁹–1.39 × 10¹⁰ cells/cm³. The porosity (V_f) was in the range of 0.2–0.85. In contrast, experimental values of Young's moduli were in good agreement with theoretically predicted values, but the relative strengths were somewhat lower than that predicted. The relaxation mechanism of microcellular was systematically investigated by DMA. The dynamic mechanical spectrometry showed that the storage modulus curve at high temperature region appeared a peak and the loss modulus was lower as compared to their solid counterparts. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 173–183, 2007     

Aligned Bioactive Multi‐Component Nanofibrous Nanocomposite Scaffolds for Bone Tissue Engineering

The ability to mimic the chemical, physical and mechanical properties of the natural extra‐cellular matrix is a key requirement for tissue engineering scaffolds to be successful. In this study, we successfully fabricated aligned nanofibrous multi‐component scaffolds for bone tissue engineering using electrospinning. The chemical features were mimicked by using the natural components of bone: collagen and nano‐hydroxyapatite along with poly[(D ,L ‐lactide)‐co‐glycolide] as the major component. Anisotropic features were mimicked by aligning the nanofibers using a rotating mandrel collector. We evaluated the effect of incorporation of nano‐HA particles to the system. The morphology and mechanical properties revealed that,at low concentrations, nano‐HA acted as a reinforcement. However, at higher nano‐HA loadings, it was difficult to disrupt aggregations and, hence, a detrimental effect was observed on the overall scaffold properties. Thermal analysis showed that there were slight interactions between the individual components even though the polymers existed as a two‐phase system. Preliminary in vitro cell‐culture studies revealed that the scaffold supported cell adhesion and spreading. The cells assumed a highly aligned morphology along the direction of fiber orientation. Protein adsorption experiments revealed that the synergistic effect of increased surface area and the presence of nano‐HA in the polymer matrix enhanced total protein adsorption. Crosslinking with 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride resulted in improved mechanical properties of the scaffolds and improved degradation stability, under physiological conditions.

     

Mechanical and dynamic viscoelastic properties of hydroxyapatite reinforced poly(ε-caprolactone)

Poly(ε-caprolactone)/hydroxyapatite (PCL/HA) composites as potential bone substitutes were prepared by melt-blending. The melting, crystallization and glass transition temperatures deduced from differential scanning calorimetery and dynamic mechanical thermal analysis (DMTA) were all changed by the addition of HA, suggesting an interaction at the interface of these two phases. Quasi-static mechanical testing shows that the yield strength and Young's modulus of PCL were increased by the addition of the reinforcement filler, HA. Dynamic viscoelastic properties were investigated using DMTA and an advanced rheometric expansion system. The results show that both the storage modulus and viscous modulus are enhanced by HA, and the PCL composite melts still behave like pseudo-plastic liquid.     

Thermal,viscoelastic, and mechanical properties of DCPD-containing polymers

The thermal, viscoelastic, and mechanical properties of cured dicyclopentadiene (DCPD)-containing polymers prepared from novel DCPD-modified unsaturated epoxypolyesters and styrene were evaluated. This was accomplished using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, three-point bending test, and Brinell’s hardness. The thermal, viscoelastic, and mechanical properties of DCPD-containing polymers were strongly dependent on chemical structure. The cross-linking density (υ _e) of obtained networks increased with increasing content of carbon–carbon double bonds in the poly(ester) structure. In addition, the introduction of DCPD rings into the poly(ester) structure increased the rigidity of the molecular backbone. It resulted in obtaining polymers which showed great improvement in mechanical properties including remarkably higher storage modulus ( E_{20 ^°\textC}^￠ E_{{20\,{}^{\circ}{\text{C}}}}^{'} ), flexural modulus at bending (E _mod), hardness, lower extension at maximum force (ε-F _max), as well as higher thermal stability. These good properties make these materials highly promising as potential candidates for structural applications.     

Effects of microscale calcium carbonate and nanoscale calcium carbonate on the fusion,thermal, and mechanical characterizations of rigid poly(vinyl chloride)/calcium carbonate composites

A Haake torque rheometer equipped with an internal mixer has been used to study the influence of microscale calcium carbonate (micro‐CaCO₃) and nanoscale calcium carbonate (nano‐CaCO₃) on the fusion, thermal, and mechanical characteristics of rigid poly(vinyl chloride) (PVC)/micro‐CaCO₃ and PVC/nano‐CaCO₃ composites, respectively. The fusion characteristics discussed in this article include the fusion time, fusion temperature, fusion torque, and fusion percolation threshold (FPT). The fusion time, fusion temperature, and FPT of rigid PVC/calcium carbonate (CaCO₃) composites increase with an increase in the addition of micro‐CaCO₃ or nano‐CaCO₃. In contrast, the fusion torque of rigid PVC/CaCO₃ composites decreases with an increase in the addition of micro‐CaCO₃ or nano‐CaCO₃. The results of thermal analysis show that the first thermal degradation onset temperature (T_onset) of rigid PVC/micro‐CaCO₃ is 7.5 °C lower than that of PVC. Meanwhile, the glass‐transition temperature (T_g) of rigid PVC/micro‐CaCO₃ is similar to that of PVC. However, T_onset and T_g of PVC/nano‐CaCO₃ composites can be increased by up to 30 and 4.4%, respectively, via blending with 10 phr nano‐CaCO₃. Mechanical testing results for PVC/micro‐CaCO₃ composites with the addition of 5–15 phr micro‐CaCO₃ and PVC/nano‐CaCO₃ composites with the addition of 5–20 phr nano‐CaCO₃ are better than those of PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 451–460, 2006     

Minimally adhesive polymer surfaces prepared from star oligosiloxanes and star oligofluorosiloxanes

The effects of the surface energy, storage modulus (G′), and glass‐transition temperature (T_g) on the biofouling behavior of siloxane and fluorosiloxane polymer surfaces (films) were studied. Irregular Si? H‐terminated tetrabranched star oligosiloxanes and star oligofluorosiloxanes were prepared by the acid‐catalyzed equilibration of octamethylcyclotetrasiloxane or 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane with tetrakis(dimethylsiloxy)silane, respectively. Terminal epoxy groups were introduced via Pt‐catalyzed hydrosilylation with allyl glycidyl ether to yield compounds that were subsequently crosslinked with α,ω‐bis(3‐aminopropyl)poly(dimethylsiloxane). The resulting films were characterized by goniometry, dynamic mechanical thermal analysis, and thermogravimetric analysis. The foul‐release behavior was studied by the measurement of how strongly sporelings (young plants) of the green seaweed Ulva adhered. The corrosion protection of aluminum was evaluated by electrochemical impedance spectroscopy. Fluorosiloxane films displayed higher G′ and T_g values, decreased contact angles (with water), and more effectively released Ulva sporelings in comparison with siloxane films. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2551–2566, 2006     

Effects of Wood Flour (WF) Pretreatment and the Addition of a Toughening Agent on the Properties of FDM 3D-Printed WF/Poly(lactic acid) Biocomposites

In order to improve the properties of wood flour (WF)/poly(lactic acid) (PLA) 3D-printed composites, WF was treated with a silane coupling agent (KH550) and acetic anhydride (Ac₂O), respectively. The effects of WF modification and the addition of acrylicester resin (ACR) as a toughening agent on the flowability of WF/PLA composite filament and the mechanical, thermal, dynamic mechanical thermal and water absorption properties of fused deposition modeling (FDM) 3D-printed WF/PLA specimens were investigated. The results indicated that the melt index (MI) of the specimens decreased after WF pretreatment or the addition of ACR, while the die swell ratio increased; KH550-modified WF/PLA had greater tensile strength, tensile modulus and impact strength, while Ac₂O-modified WF/PLA had greater tensile modulus, flexural strength, flexural modulus and impact strength than unmodified WF/PLA; after the addition of ACR, all the strengths and moduli of WF/PLA could be improved; after WF pretreatment or the addition of ACR, the thermal decomposition temperature, storage modulus and glass transition temperature of WF/PLA were all increased, and water absorption was reduced.     

Synthesis,Crystal Structures,and Anti‐cervical Cancer Activity Evaluation of Three Trinuclear Transition Metal(II) Complexes with N,O‐Donor Schiff Base Ligand

A new bi‐nucleating Schiff base ligand, 2‐(((3‐(dimethylamino)propyl)imino)methyl)‐6‐methoxyphenol (HL₁) was prepared by a one‐pot condensation reaction, which was further used in the construction of three trinuclear Schiff base transition metal(II) complexes [Cu₃(L1)₂(OH)₂(H₂O)₂](NO₃)₂ ( 1 ), [Co₃(L1)₂(OH)₂(H₂O)₂](NO₃)₂ ( 2 ), and [Cu₃(L1)₂(N₃)₄] ( 3 ). Furthermore, a green hand grinding technique was implemented to reduce the particle size of the coordination complexes to generate the nanoscale compounds. The SEM studies reveal the formation of square and spherical particles for nano 1 and 2 , and nanorod for nano 3 . In addition, the anti‐proliferation activity of nano 1 – 3 was detected on the human cervical cancer Hela cells with CCK‐8 assay. The cell viability curves and IC₅₀ values indicated that only nano 1 has anti‐proliferation activity on Hela cells. To further investigate the mechanism of nano 1 induced Hela cell death, the Annexin V‐FITC/PI double staining assay, western blot assay, and ROS level detection was conducted.     

Viscoelastic properties of poly(ε‐caprolactone) – hydroxyapatite micro‐ and nano‐composites

Various composites have been proposed in the literature for the fabrication of bioscaffolds for bone tissue engineering. These materials include poly(ε‐caprolactone) (PCL) with hydroxyapatite (HA). Since the biomaterial acts as the medium that transfers mechanical signals from the body to the cells, the fundamental properties of the biomaterials should be characterized. Furthermore, in order to control the processing of these materials into scaffolds, the characterization of the fundamental properties is also necessary. In this study, the physical, thermal, mechanical, and viscoelastic properties of the PCL‐HA micro‐ and nano‐composites were characterized. Although the addition of filler particles increased the compressive modulus by up to 450%, the thermal and viscoelastic properties were unaffected. Furthermore, although the presence of water plasticized the polymer, the viscoelastic behavior was only minimally affected. Testing the composites under various conditions showed that the addition of HA can strengthen PCL without changing its viscoelastic response. The results found in this study can be used to further understand and approximate the time‐dependent behavior of scaffolds for bone tissue engineering. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel synthesis of nano‐calcium carbonate (CaCO3)/polystyrene (PS) core–shell nanoparticles by atomized microemulsion technique and its effect on properties of polypropylene (PP) composites

Calcium carbonate (CaCO₃)/polystyrene (PS) nanoparticles (<100 nm) with core–shell structure were synthesized by atomized microemulsion technique. The polymer chains were anchored onto the surface of nano‐CaCO₃ through triethoxyvinyl silane (TEVS) as a coupling agent. Ammonium persulfate (APS), sodium dodecyl sulfate (SDS) and n‐pentanol were used as initiator, surfactant, and cosurfactant, respectively. Polymerization mechanism of core–shell latex particles was discussed. Encapsulation of nano‐CaCO₃ by PS was confirmed by using transmission electron microscope (TEM). Grafting percentage of core–shell particles was investigated by Thermogravimetric Analyzer (TGA). Nano‐CaCO₃/PS core–shell particles were characterized by Fourier transform infrared (FTIR) spectrophotometer and differential scanning calorimeter (DSC). The results of FTIR revealed existence of a strong interaction at the interface of nano‐CaCO₃ particle and PS, which implies that the polymer chains were successfully grafted onto the surface of nano‐CaCO₃ particle through the link of the coupling agent. In addition, TGA and DSC results indicated an enhancement of thermal stability of core–shell materials compared with the pure nano‐PS. Nano‐CaCO₃/PS particles were blended with polypropylene (PP) matrix on Brabender Plastograph by melt process with different wt% of loading (i.e. 0.1–1 wt%). The interfacial adhesion between nano‐CaCO₃ particles and PP matrix was significantly improved when the nano‐CaCO3 particles were grafted with PS, which led to increased thermal, rheological, and mechanical properties of (nano‐CaCO₃/PS)/PP composites. Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed a perfect dispersion of the nano‐CaCO₃ particles in PP matrix. Copyright © 2011 John Wiley & Sons, Ltd.     

Dynamic mechanical properties of aluminum nitride/cyanate ester composites for high performance electronic packaging

Viscoelastic ature is one of the key features of polymeric composites. A series of cyanate ester (CE)‐based composites with different aluminum nitride (AlN) contents for high performance electronic packaging, coded as AlN/CE, were developed; the viscoelastic nature of AlN/CE composites was intensively investigated by employing dynamic mechanical analysis (DMA). Results show that the AlN content has a great effect on dynamic mechanical properties of AlN/CE composites. The storage modulus in the glassy region increases linearly with the addition of AlN as well as the increase of AlN content. Meanwhile, all composites also exhibit notably higher loss modulus than cured CE resin due to the appearance of new energy dissipation forms. In addition, the incorporation of AlN has a significant effect on damping factor peak. All reasons leading to these phenomena are analyzed from the view of structure–property relationship. Copyright © 2009 John Wiley & Sons, Ltd.     

Biodegradable poly(p‐dioxanone) reinforced and toughened by organo‐modified vermiculite

Poly(p‐dioxanone) (PPDO)/vermiculite (VMT) nanocomposites with exfoliated structure were prepared successfully by in situ intercalative polymerization of p‐dioxanone (PDO) in the presence of organo‐modified vermiculite (OVMT) with the aid of ultrasonic action. The nano‐structure of the nanocomposites was established using X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observations. The investigation of crystallization behavior by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) proved that exfoliated OVMT platelets acted as a template for spherulite growth. The thermal stability of nanocomposites was enhanced than that of pure PPDO. Dynamic mechanical analysis (DMA) indicated nanoscale OVMT platelets restricted the motion of PPDO segments, which benefitted the increase of storage and loss modulus. The tensile properties showed that nanocomposites were reinforced and toughened significantly by the addition of nanoscale OVMT platelets. Copyright © 2009 John Wiley & Sons, Ltd.