Thermal and mechanical properties of nanocomposites based on a PLLA‐b‐PEO‐b‐PLLA triblock copolymer and nanohydroxyapatite

Composites which combine biocompatible polymers and hydroxyapatite are unique materials with regards to their mechanical properties and bioactivity in the development of temporary bone‐fixation devices. Nanocomposites based on a biocompatible and amphiphilic triblock copolymer of poly(l‐ lactide) (PLLA) and poly(ethylene oxide) (PEO) —PLLA‐b‐PEO‐b‐PLLA— and neat (nHAp) or PEO‐modified (nHAp@PEO) hydroxyapatite nanoparticles were prepared by dispersion in benzene solutions, followed by freeze‐drying and injection moulding processes. The morphology of the copolymers of a PEO block dispersed throughout a PLLA matrix was not changed with addition of the nanofillers. The nHAp particles were spherical and, after modification, the nHAp@PEO nanoparticles were partially agglomerated. In the nanocomposites, these particles characteristics remained unchanged, and the nHAp particles and nHAp@PEO agglomerates were uniformly dispersed through the copolymer matrix. These particles acted as nucleating agents, with nHAp@PEO being more efficient. The incorporation of nHAp increased both the reduced elastic modulus (～22%) and the indentation hardness (～15%) in comparison to the copolymer matrix, as determined by nanoindentation tests, while nHAp@PEO addition resulted in lower increments of these mechanical parameters. The incorporation of untreated nHAp was, therefore, more beneficial with regards to the mechanical properties, since the amphiphilic PLLA‐b‐PEO‐b‐PLLA matrix was already efficient for nHAp nanoparticles dispersion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44187.     

Polypropylene‐organoclay nanocomposite: Preparation,microstructure, and mechanical properties

A series of polypropylene (PP) nanocomposites containing 2, 4, and 6 wt % of an organophilic montmorillonite clay was prepared via direct melt mixing in the presence of maleic anhydride grafted polypropylene (PP‐g‐MAH) as compatibilizing agent. Microstructure characterization was performed by X‐ray diffraction analysis. Nanocomposites exhibited a 15 and 22% enhancement in tensile modulus and impact strength, respectively. The heat deflection temperature of PP nanocomposites was 36°C greater than for pure PP. Thermal and mechanical properties of nanocomposites were compared to properties of traditional PP‐talc and PP‐glass fiber composites. The results showed that the properties of nanocomposites improved compared to ordinary polypropylene composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Investigation of nanostructure and properties of aromatic–aliphatic polyamide‐based nanocomposites with clay additives

Aromatic–aliphatic polyamide/clay nanocomposites were produced using solution intercalation technique. Surface modification of the clay was performed with ammonium salt of aromatic diamine and the polyamide chains were produced by condensation of 4‐aminophenyl sulfone with sebacoyl chloride (SCC) in dimethyl acetamide. Carbonyl chloride endcapped polymer chains were prepared by adding extra SCC near the end of polymerization reaction. The nanocomposites were investigated for organoclay dispersion, water absorption, mechanical, and thermal properties. Formation of delaminated and intercalated nanostructures was confirmed by X‐ray diffraction and TEM studies. Tensile strength and modulus improved for nanocomposites with optimum organoclay content (8 wt %). Thermal stability and glass transition temperatures of nanocomposites increased relative to pristine polyamide with augmenting organoclay content. The amount of water uptake for these materials decreased as compared with the neat polyamide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical,thermal, and morphological properties of injection molded poly(lactic acid)/SEBS‐g‐MAH/organo‐montmorillonite nanocomposites

Poly(lactic acid)/organo‐montmorillonite (PLA/OMMT) nanocomposites toughened with maleated styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) were prepared by melt‐compounding using co‐rotating twin‐screw extruder followed by injection molding. The dispersibility and intercalation/exfoliation of OMMT in PLA was characterized using X‐ray diffraction and transmission electron microscopy (TEM). The mechanical properties of the PLA nanocomposites was investigated by tensile and Izod impact tests. Thermogravimetric analyzer and differential scanning calorimeter were used to study the thermal behaviors of the nanocomposite. The homogenous dispersion of the OMMT silicate layers and SEBS‐g‐MAH encapsulated OMMT layered silicate can be observed from TEM. Impact strength and elongation at break of the PLA nanocomposites was enhanced significantly by the addition of SEBS‐g‐MAH. Thermal stability of the PLA/OMMT nanocomposites was improved in the presence of SEBS‐g‐MAH. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Novel Polymer Clay‐Based Nanocomposites: Films with Remarkable Optical and Water Vapor Barrier Properties

The impact of varying the copolymer composition of styrene–co‐butyl acrylate copolymers on the dispersion of montmorillonite (MMT) clay and the effect thereof on the transparency and water vapor barrier properties of the resultant films is assessed. The hybrid latexes containing MMT clay concentrations of 10–30 wt% are prepared using miniemulsion polymerization. The morphology of the resultant latexes shows that the MMT particles are predominantly adhered onto the surface of the latex particles. However, the transparency of the films suggests a fair dispersion of the MMT platelets in the matrix. The thickness‐normalized light transmittance for copolymers with 40 and 50 mol% styrene only decreases from 70% in the neat films to 50% in the nanocomposite films containing 30 wt% clay. The best optical properties are observed for the copolymers with 30 mol% styrene, in which the light transmittance only decreases from 85% (unfilled film) to 60% in the nanocomposite films containing 30 wt% clay. Overall, the water vapor barrier properties are much higher in the copolymer films with 30 mol% styrene due to the unique morphological organization of MMT platelets in the matrix.

     

Effect of fiber‐forming conditions and type of MMT modifier on the structure and properties of multifunctional polyimideamides nanocomposite fibers

The effect of fiber‐spinning conditions on the structure, sorption, and strength properties of polyimideamides (PIA) nanocomposite fibers has been examined. Montmorillonite (MMT) modified with octadecylamine was used as a nanoadditive. The properties of fibers containing differently modified MMT were compared. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2940–2944, 2007     

Thermal properties and morphology of a poly(vinyl alcohol)/silica nanocomposite prepared with a self‐assembled monolayer technique

A poly(vinyl alcohol) (PVA)/silica (SiO₂) nanocomposite was prepared with a novel self‐assembled monolayer technique, and its morphology and thermal properties were studied with different material characterization instruments. The treated SiO₂ nanoparticles were dispersed in the PVA matrix homogeneously, and the thermal properties of the nanocomposite were markedly improved in comparison with those of pure PVA. Under the same isothermal heating conditions, the decomposition of the nanocomposite was delayed significantly in comparison with that of PVA. The thermal degradation of the nanocomposite was a two‐step reaction, including the degradation of the side chain and main chain. The products of side‐chain degradation were mainly carboxylic acid, whereas main‐chain degradation primarily produced carbon dioxide and low‐molecular‐weight conjugated polyene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1436–1442, 2005     

Waste polystyrene foam‐graft‐acrylic acid/montmorillonite superabsorbent nanocomposite

A novel superabsorbent nanocomposite based on partially neutralized acrylic acid, waste polystyrene foam, and sodium type montmorillonite (Na‐MMT) powder was synthesized through emulsion polymerization using N, N′‐methylenebisacrylamide as a crosslinker, 2,2′‐azo‐bisiso‐butyronitrile, ammonium persulfate, and sodium sulfite as mixed redox initiators. The effects of such factors as amount of Na‐MMT, crosslinker, initiator, and neutralization degree on water absorbency of the superabsorbent were investigated. The composites were characterized by Fourier transform infrared spectroscope, X‐ray diffraction, thermo gravimetric analysis, and scanning electron microscope. The results show that acrylic acid monomer successfully grafted onto the polystyrene chain, the layers of Na‐MMT were exfoliated and dispersed in the composite at nano size after copolymerization. The introduction of waste polystyrene foam in the composite increased the water absorbency rate. The addition of Na‐MMT not only enhanced the thermal stability of the composites but also increased its water absorbency, and the optimal water absorbencies of distilled water and saline water (w_NaCl = 0.9%) of the nanocomposites were more than 1180 g H₂O/g and 72.6 g H₂O/g, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2341–2349, 2007     

Compatibilizing polyimide/silica hybrids by alkoxisilane‐terminated oligoimides: Morphology–Properties relationships

A fluorinated polyimide (PI), synthesized from 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride and 4,4′‐diaminodiphenyl ether, was used as matrix for the preparation of PI/silica hybrids. The inorganic phase was obtained in situ by a sol–gel route with tetraethoxysilane as precursor. Both micron‐ and nano‐scale hybrids were obtained depending on the interfacial interaction between the organic and inorganic phases. To promote such interaction a compatibilizing agent was synthesized, in the form of an alkoxisilane‐terminated oligoimide. Both the PI and the coupling agent were characterized by FTIR and Raman spectroscopies and by GPC measurements. The effect of the coupling agent on the morphology of the hybrids and on the size of the silica particles was investigated by scanning electron microscopy. The viscoelastic, mechanical, and thermal properties of hybrid composites were studied. It was shown that by adding appropriate amounts of the compatibilizer it was possible to control the morphology and to obtain homogeneous nanostructured systems. A general improvement of the mechanical performances and of the thermal stability was demonstrated, together with an increase of T_g, which was found more pronounced for the nanocomposites than for the microcomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Properties of organo‐clay/natural rubber nanocomposites: Effects of organophilic modifiers

The effect of various modifiers on the structure and properties of clay/natural rubber nanocomposites are investigated with the aim to evaluate the effect of size and structure of the modifier. Nanocomposites are prepared by melt intercalation method. Mechanical properties of the cured rubber containing nanoclay are compared with the reference compound without the filler. No improvement of mechanical properties is observed for small organic cations; however, stress and strain at break of clay/rubber nanocomposites increase with rising number of octyl chains in the interlayer spaces of organo‐clays. Concerning organo‐cations with the same number of carbon atoms, more effective are the modifiers with several shorter carbon chains compared to those with one long chain. The composites exhibit hybrid structure of nanocomposite and microcomposite as revealed by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The details of the structure are supported by DMTA and hysteresis measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of hybrid nanoparticle additives on epoxy‐nanocomposite behavior and morphology

Amine modified polyhedral oligomeric silsesquioxane (POSS‐NH₂) was used to modify sodium montmorillonite (MMT) nanoclays for improved dispersion in epoxy resin. The dispersion of the clay particles was inspected using scanning electron microscopy, energy dispersive spectroscopy (EDS) and X‐Ray diffraction and the thermal properties compared using differential scanning calorimetry (DSC) and thermogravametric analysis. The introduction of the amine‐POSS was found to have a positive effect on the dispersion of the MMT clays and prevented agglomeration. The absence of clay agglomerates lead to an increase in glass transition temperature (T_g) from 44°C in the samples with the untreated clay up to 54°C in the samples with 10% additional POSS‐NH₂. The addition of POSS‐NH₂ initial increase of the weight loss (T_{d 5%}) but slowed down the rate of degradation due to the formation of an inert silica layer and eventually leading to an increased charyield. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of PP‐g‐MA on morphology,mechanical properties and deformation mechanism of copolypropylene/clay nanocomposite

Copolypropylene/organoclay nanocomposites are prepared by melt intercalation method in this research. Two different routes for addition of compatibilizer are examined, i.e. addition in the twin‐screw extruder along with the polymer and the clay powder simultaneously and premixing the compatibilizer with the reinforcement in a batch mixer before addition to the polypropylene (PP) matrix. Morphology, tensile and impact properties and deformation mechanisms of the samples made via two procedures are studied and compared with those of the noncompatibilized system. To study the structure of nanocomposites, x‐ray diffraction and transmission electron microscopy techniques are utilized. The deformation mechanisms of different samples are examined via reflected and transmitted optical microscopy. The results reveal that introduction of compatibilizer and also the procedure in which the compatibilizer is added to the compound, affect structure and mechanical properties of nanocomposite. The elastic modulus of PP‐clay nanocomposite has increased 11.5% with incorporation of compatibilizer. Also, introduction of organoclay without compatibilizer facilitates crazing at the notch tip of PP in 3PB testing. Incorporation of compatibilizer, however, makes difficulties in initiation and growth of crazes at the notch tip. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of modifiers on morphology and thermal properties of novel thermoplastic polyurethane‐peptized laponite nanocomposite

Laponite RDS (Laponite containing pyrophosphate based peptizer) was modified with cetyl trimethyl ammonium bromide (cLS) and dodecylamine hydrochloride (dLS), respectively. Thermoplastic polyurethane (TPU)‐modified Laponite RDS nanocomposites were prepared by solution mixing technique. Morphologies of these two modified clay‐nanocomposites are found to be markedly different. cLS based TPU nanocomposites exhibit partly exfoliated, intercalated, and aggregated structure at lower clay content but a network type of structure is observed at higher clay content. However, dLS based TPU nanocomposites demonstrate spherical cluster type of structure at all clay contents. Nearly two fold increase in storage modulus is observed in both glassy and rubbery state with merely 1% cLS content which gradually decreases with an increase in the clay content. However, in case of dLS filled nanocomposite, gradual increase in storage modulus is observed with an increase in the clay content. Thermogravimetric analysis (TGA) studies indicate that the temperature corresponding to 5 wt % degradation of TPU is enhanced by 19.1 and 12.5°C with the addition of merely 1% cLS and dLS, respectively. However, the activation energy of degradation of neat TPU, as determined by isothermal TGA analysis, is found to be higher than that of the nanocomposites containing 1% of cLS and dLS, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride)/silica nanocomposites derived from in situ suspension polymerization

Poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride) (PVVM)/silica nanocomposites were prepared by the suspension radical copolymerization of the monomers in the presence of fumed silica premodified with γ‐methylacryloxypropl trimethoxy siliane. Morphological observation showed that the silica particles of nanometer scale were well dispersed in the copolymer matrix of the nanocomposites films, whereas silica particles tended to agglomerate in the composites films prepared by the solution blending of PVVM with silica. The experimental results show that the thermal stability, glass‐transition temperature, tensile strength, and Young's modulus were significantly enhanced by the incorporation of silica nanoparticles. The enhancement of properties was related to the better dispersion of silica particles in polymer matrix and the interaction between the polymer chains and the surfaces of the silica particles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Nanocomposites based on poly(ϵ‐caprolactone) and the montmorillonite treated with dibutylamine‐terminated ϵ‐caprolactone oligomer

Dibutylamine‐terminated ε‐caprolactone oligomers (CLOs: CLOL, CLOM, and CLOH) with number–averaged molecular weight (M_n), 500, 1300, and 2200, respectively, were synthesized by the ring‐opening polymerization of ε‐caprolactone initiated by 2‐(dibutylamino)ethanol in the presence of tin(II) 2‐ethylhexanoate. Nanocomposites based on poly(ε‐caploractone) (PCL) and the caprolactone oligomer‐treated montmorillonites (CLO‐Ms: CLOL‐M, CLOM‐M, and CLOH‐M) were prepared by melt intercalation method. The XRD and TEM analyses of the PCL composites revealed that the extent of exfoliation of the clay platelets increased with increasing molecular weight of the used CLOs. Tensile strength and modulus of the PCL/CLO‐M composites increased with increasing molecular weight of the CLO and increasing inorganic content. The tensile modulus of the PCL/CLOH‐M nanocomposite with inorganic content 5.0 wt % was three times higher than that of control PCL. Among the PCL/CLO‐M composites, the PCL/CLOM‐M composite had the highest crystallization temperature and melting temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Solvothermal synthesis of organically modified α‐zirconium phosphate‐based polystyrene nanocomposites and thermal stability

Polystyrene/α‐zirconium phosphate (PS/OZrP) nanocomposites were prepared based on the organically modified α‐ZrP(OZrP) with hexadecyltrimethyl ammonium bromide (C16) by solvothermal technique and solution refluxing. The structure of the PS/OZrP composites was characterized by X‐ray diffraction and high‐resolution electronic microscopy. The thermal behaviors of the composites obtained were investigated by thermogravimetric analysis. The maximum decomposition temperatures (T_max) of PS/OZrP nanocomposites prepared by solvothermal method increased gradually from 431 to 458°C with the increase of the OZrP loading from 0 to 20 wt %, and the amounts of the charred residue at 600°C (char wt %) had a remarkable increase from 1.6 to 17.1 wt %, respectively. Moreover, the TG results of the nanocomposites prepared by solvothermal method have more obvious enhancement in the thermal stabilities and especially in the amount of charred residue at 600°C (char wt %), which has a double increase from 4.2 to 8.5 wt % at the content of 10 wt % OZrP than by solution refluxing. All results suggested that the solvothermal method is an effective way for the preparation of PS/OZrP nanocomposites with the intercalated nanostructure, which led to the obviously improved thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122:593–598, 2011     

Preparation and structure and mechanical properties of poly(styrene‐b‐butadiene)/clay nanocomposites

Star‐shaped and linear block thermoplastic poly(styrene‐b‐butadiene) copolymer (SBS)/organophilic montmorillonite clays (OMMT) were prepared by a solution approach. The intercalation spacing in the nanocomposites and the degree of dispersion of nanocomposites were investigated by X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The mechanical properties, dynamic mechanical properties, and thermal stability of these nanocomposites were determined. Results showed that SBS chains were well intercalated into the clay galleries and an intercalated nanocomposite was obtained. The mechanical strength of nanocomposites with the star‐shaped SBS/OMMT were significantly increased. The addition of OMMT also gave an increase of the elongation, the dynamic storage modulus, the dynamic loss modulus, and the thermal stability of nanocomposites. The increase of the elongation of nanocomposites indicates that SBS has retained good elasticity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3430–3434, 2004     

Incorporating functionalized silica nanoparticles in polyethersulfone‐based anion exchange nanocomposite membranes

In order to investigate for anion exchange membranes (AEMs) with improved properties, four series of polyethersulfone‐based composite AEMs are fabricated by incorporating pristine and three functionalized silica nanoparticles containing propylamine, trimethylpropylamine, and melamine‐based dendrimer amine groups. The results show that by choosing appropriate functional agent, anion exchange membranes with improved parameters can be achieved. The polymeric matrix of the membranes is synthesized by chloromethylation of polyethersulfone using thionyl chloride followed by amination with trimethylamine (TMA). The effectiveness of chloromethylation process is confirmed by ¹H NMR analysis. The effects of functional groups on characteristic and transport properties of the prepared composite membranes i.e., SEM, IEC, water uptake, porosity transport properties, and conductivity are investigated. The scanning electron microscope images illustrates that the synthesized membranes possess dense structures. Ion exchange capacity (IEC), water uptake, transport properties, and conductivity of the composite membranes are measured. In addition, the morphology and thermal stability are characterized. IECs and ion conductivities of up to 1.45 meq g^?1 and 45.46 mS cm^?1 and moderate transport characteristics are obtained from the modified membranes which confirm that these membranes are appropriate for applying in electro‐membrane processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44596.     

Structural,mechanical and thermal studies of double‐molded isotactic polypropylene nanocomposites with multiwalled carbon nanotubes

Nanocomposites of isotactic polypropylene (iPP) and multiwalled carbon nanotubes (MWCNTs) with various contents of MWCNTs were fabricated by double molding techniques. X‐ray diffraction measurements reveal a development of α‐crystal with lamellar stacks having a long period of 150 Å in the neat iPP that increases to 165 Å in 2 wt % MWCNTs‐loaded composites, indicating that MWCNTs enhance crystallization of iPP as a nucleating factor. Mechanical properties, such as tensile strength, flexural strength, Young's modulus, tangent modulus, and microhardness are found to increase with increasing MWCNTs content. Thermal analyses represent an increase of crystallization and melting temperatures and a decrease of thermal stability of the composites with increasing MWCNTs. Changes in structural, mechanical, and thermal properties of the composites due to the addition of MWCNTs are elaborately discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of BCDA‐based polyimide–clay nanocomposites

Bicyclo[2.2.2]oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride (BCDA)‐based polyimide–clay nanocomposites were prepared from their precursor, namely polyamic acid, by a solution‐casting method. The organoclay was prepared by treating sodium montmorillonite (Kunipia F) clay with dodecyltrimethylammonium bromide at 80 °C. Polyamic acid solutions containing various weight percentages of organoclay were prepared from 4,4′‐(4,4′‐isopropylidenediphenyl‐1,1′‐diyldioxy)‐dianiline and BCDA in N‐methyl‐2‐pyrrolidone containing dispersed particles of organoclay at 20 °C. These solutions were cast on a glass plate using a Doctor's blade and then heated subsequently to obtain nanocomposite films. The nanocomposites were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal mechanical analysis, dynamic mechanical analysis, polarizing microscopy, scanning electron microscopy, transmission electron microscopy, wide‐angle X‐ray diffraction (WAXD) and thermogravimetric analysis. The glass transition temperature of the nanocomposites was found to be higher than that of pristine polymer. The coefficient of thermal expansion of the nanocomposites decreased with increasing organoclay content. WAXD studies indicated that the extent of silicate layer separation in the nanocomposite films depended upon the organoclay content. Tensile strength and modulus of the nanocomposite containing 1% organoclay were significantly higher when compared to pristine polymer and other nanocomposites. The thermal stability of the nanocomposites was found to be higher than that of pristine polymer in air and nitrogen atmosphere. Copyright © 2007 Society of Chemical Industry