Poly(butylene succinate)/layered double hydroxide bionanocomposites: Relationships between chemical structure of LDH anion,delamination strategy,and final properties

A series of poly(butylene succinate) (PBS) containing organo‐modified layered double hydroxide (LDH) are prepared by melt compounding and by in situ polymerization of succinic ester and 1,4‐butanediol. Various LDHs intercalated with renewable organic anions are used. More specifically, lauryl sulfate, stearate, succinate, adipate, sebacate, citrate, and ricinoleate ions are used as LDHs organo‐modifiers. The thermal, rheological, and dynamic mechanical properties of the samples are investigated. The results reveal a general mechanical reinforcement imparted by the clays. Significant changes are observed for the in situ polymerized nanocomposites, especially for LDH stearate which improves the properties of PBS nanostructure, whereas very few differences are observed for the other samples. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1931–1940, 2013     

Melt-spinning of LDH/HDPE nanocomposites

Melt-spinning of layered double hydroxide (LDH)/high density polyethylene (HDPE) nanocomposites was reported for the first time. Initially LDH/HDPE nanocomposites were prepared by melt-mixing, in which clay loadings were up to 3 wt% while compatibilizer to clay ratio was kept to be 2:1. LDHs were hydrophobically modified by hexadienoic acid, tetradecanoic acid, and octadecanoic acid to overcome the incompatibility between matrix polymer and LDH. The organomodified LDH showed different interlayer arrangements. Both the modifications and the processing conditions affected the properties of melt-spun fibers. Nanocomposites were rheologically characterized by using a classical semi-quantitative method and additionally by a rather new method, which is an interpretation of Carreau–Yasuda model. Tetradecanoic acid modified LDH at 1 wt% filler loading was found to give most notable results.     

Structure and crystallization behaviour of syndiotactic polystyrene/layered double hydroxide nanocomposites

Syndiotactic polystyrene (sPS) based polymer nanocomposites have been prepared using surfactant‐free layered double hydroxides (SF‐LDHs) by a modified solvent mixing method with different loadings of 1, 2.5, 5 and 10 wt%. The nanocomposite preparation process involves a wash treatment of as‐prepared SF‐LDHs in an appropriate organic solvent followed by gel formation in a non‐polar solvent. The gel was directly used to make highly dispersed polymer nanocomposites. The influence of highly dispersed SF‐LDH platelets on the crystallization, polymorphism, thermal stability and flame retardancy of sPS was examined. It was shown that SF‐LDHs significantly enhance the crystallization rate of sPS and favour the formation of the thermodynamically stable β form along with the α form of sPS. Moreover, highly dispersed SF‐LDHs decrease the heat release rate and total heat release of sPS indicating the enhancement of flame‐retardant properties of sPS. In this way, it was found that the dispersed SF‐LDH platelets act as a multifunctional nanofiller for sPS. © 2015 Society of Chemical Industry     

Preparation and flame retardancy of polystyrene nanocomposites based on layered double hydroxides

Various layered double hydroxides (LDHs), including MgAl, CoAl, NiAl, and ZnAl‐LDHs, were synthesized and modified using sodium dodecyl benzene sulfonate. Nonhalogen flame‐retardant PS/LDHs nanocomposites were prepared via melt mixing method. The structure of PS/LDHs nanocomposites was investigated by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) pattern technique, and scanning electronic microscope. Results from XRD indicated that intercalated/exfoliated structure was achieved in the polystyrene matrix. Dynamic mechanical thermal analysis suggested that the storage modulus and T _g for the PS/LDHs nanocomposites was efficiently improved. Thermal and flammability properties of PS nanocomposites were investigated using thermogravimetry and cone calorimetry. Thermal analysis was evaluated and the prepared nanocomposites showed slightly lower thermal stability probably due to the presence of LDH, which starts to decompose at a lower temperature. Compared with neat PS, the peak heat release rate of PS/MgAl and PS/ZnAl‐LDHs nanocomposites filled with 5 wt% LDHs is reduced by 7% and 12%, respectively. Among all LDHs, MgAl, and ZnAl‐LDHs had a better smoke suppression effect with a reduction of peak smoke production rate and CO release rate of 37% and 44%, respectively. POLYM. COMPOS., 38:1680–1688, 2017. © 2015 Society of Plastics Engineers     

Preparation of PET/LDH composite materials and their mechanical properties and permeability for O2

The terephthalate‐intercalated LDHs (TA‐LDHs) are used to improve the barrier properties of poly(ethylene terephthalate) (PET) for their application in liquid food packaging. First, TA‐LDHs were synthesized from freshly prepared metal hydroxides. PET/LDH nanocomposites were then prepared by a masterbatch process. The structures and morphologies of TA‐LDHs and PET/LDH nanocomposites were characterized using X‐ray diffractometer, transmission electronic microscopy, and scanning electron microscope. The mechanical performances and the oxygen permeability of the PET/LDH composites were measured using a precision universal tester and differential pressure gas permeameter, respectively. The influence of TA‐LDH content on their structures and properties was studied. PET/LDH nanocomposites with 1 and 2 wt% of TA‐LDHs are partially exfoliated nanocomposites, while PET/LDH with 5 wt% of TA‐LDHs is an intercalated nanocomposite. The PET/LDH nanocomposites prepared by a masterbatch process show better mechanical properties and gas barrier properties. PET/LDHs‐m2 with 2 wt% of TA‐LDHs could offer up to a 29.4% improvement in tensile strength over PET and the Young's modulus is increased by 38.9%. The O₂ permeation of PET/LDHs‐m2 with 2 wt% of TA‐LDHs is decreased by 46.2%. POLYM. ENG. SCI., 59:E366–E371, 2019. © 2019 Society of Plastics Engineers     

Study on response behaviors of mixed solution of polyelectrolytes and worms under shear

In this contribution, polyvinylpyrrolidone (PVP) nanocomposites (NCs) with novel chiral diacid intercalated layered double hydroxides (LDHs) as nanofillers were prepared via ultrasonic irradiation. Chiral LDH was synthesized in one step via a co-precipitation reaction in aqueous solution under ultrasonic irradiation. The modified Mg-Al LDH shows an increase in interlayer distance as compared to the unmodified Mg-Al LDH by X-ray diffraction (XRD). Different NCs of organo-modified chiral LDHs and PVP were constructed by means of an ultrasonic process. The structures of these new materials were investigated by XRD, Fourier transform infrared, field emission scanning electron microscopy and transmission electron microscopy techniques. XRD and electron microscopy results confirmed the delaminated state of the LDH in the PVP matrix. Furthermore, thermal analysis was evaluated and the prepared NCs show significantly improved thermal stability at higher temperature because of the homogeneous and good dispersion of modified LDH in polymeric matrix.     

Thermal properties and degradation behavior of poly(1,4‐butylene adipate)/modified layered double hydroxide nanocomposites

In this study, poly(1,4‐butylene adipate) (PBA)/organomodified layered double hydroxide (m‐LDH) nanocomposites were synthesized and characterized as a new material for green materials use. m‐LDH was initially prepared with magnesium nitrate hexahydrate, aluminum nitrate‐9‐hydrate, oleic acid, and sorbitol by a novel one‐step coprecipitation method to intercalate the oleic acid and sorbitol organomodifier into the interlayer of the layered double hydroxide. The solution mixing process was then applied and shown to be an efficient method for fabricating the PBA/m‐LDH nanocomposites. The m‐LDH characterized by X‐ray diffraction (XRD) showed a high interlayer spacing of 58.8 Å. The morphology and thermal properties of the PBA/m‐LDH nanocomposites were characterized with XRD, transmission electron microscopy, and thermogravimetric analysis. It was shown that the m‐LDH was well distributed in the PBA matrix and that the thermal properties of the PBA/m‐LDH nanocomposites significantly improved with a loading of 0.1 wt % m‐LDH. Finally, the biodegradability of the PBA/m‐LDH nanocomposites was tested with lipase from Pseudomonas fluorescens as a microbial catalyst. It was shown that an addition of m‐LDH up to 0.5% resulted in a significant difference in terms of the biodegradability. After 120 h of degradation, the residual weight and surface morphology of the composite films were affected by the presence of m‐LDH. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42083.     

Modeling the effect of the curing conversion on the dynamic viscosity of epoxy resins cured by an anhydride curing agent

Nanocomposites of poly(vinyl alcohol) (PVA) with Mg‐Al layered double hydroxides (LDHs) were prepared with different compositions, viz., 2, 4, 6, and 8 wt %, of LDH, by solution‐intercalation method. The effect of LDH contents on thermal, physicomechanical, and morphological property of PVA films were investigated. Differential scanning calorimetric analysis reveals that LDH layers promote a new crystalline phase for PVA. The tensile analysis of PVA/LDH nanocomposites indicates reduction in tensile strength and modulus with change in LDH concentration and moisture. The microstructure analysis by optical microscopy and scanning electron microscopy demonstrates exfoliation and dispersion of LDHs in the PVA matrix in a disorderly fashion. The primary focus of the present investigation is to explore the potential of LDHs as nanofiller in a polyhydroxy polymer without surface modification. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In situ microwave‐assisted polymerization of polyethylene terephtalate in layered double hydroxides

The synthesis of poly(ethylene terephthalate) (PET)/layered double hydroxide (LDH) nanocomposites through microwave methods has been investigated. To enhance the compatibility between the PET polymer and the LDH, dodecyl sulfate was intercalated in the lamellar structure. The organo‐LDH structure was confirmed by powder X‐ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR). PET nanocomposites were prepared with 0–10 wt % of LDH content by in situ microwave‐assisted polymerization. PXRD was used to detect the formation of the exfoliated PET/LDH nanocomposites. Transmission electron microscopy was used to observe the dispersed layers and to confirm the exfoliation process. FTIR spectroscopy confirmed that the polymerization process had occurred. TG and DTA are used to study changes in thermal stability of the nanocomposites, which resulted enhanced by well dispersed LDHs layers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(ɛ‐caprolactone) nanocomposites with layered double hydroxides modified by in situ grafting polymerization: Structure characterization and barrier properties

The synthesis of multimetallic layered double hydroxides‐g ‐poly(?‐caprolactone) (LDHs‐g ‐PCL) was explored by in situ ring‐opening polymerization, considering layered clay's improvement on barrier properties in polymer films. LDHs/PCL nanocomposites were prepared by blending LDHs‐g ‐PCL and pure PCL via solution casting method. With incorporation of as low as 0.2 wt % of LDHs, LDHs/PCL nanocomposites exhibited excellent mechanical performance with tensile strength and elongation at break over 45 MPa and 837%, respectively. Compared with pure PCL, the O₂ permeability of LDHs/PCL nanocomposites decreased by nearly 78% as LDHs content increased up to 1 wt %. It was revealed that the key parameter to improve the barrier properties is not only the high aspect ratio of layered clays but also the specific interactions that they develop in the polymers matrix. Due to the merits of its biodegradation and physical properties, LDHs/PCL nanocomposites could be potential materials applied in packaging industry widely. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45320.     

The Polymerization of Unsaturated Polyester and Silane-Functionalized Layered Double Hydroxides

The preparation of surface-modified layered double hydroxides/unsaturated polyester (LDH/UP) nanocomposites were performed. By in situ coprecipitation, LDHs, modified through grafting of vinyltriethoxysilane (VTS) carrying a double bond using the anionic surfactant sodium dodecyl sulfate (SDS), were used as nanofillers for unsaturated polyester (UP). The morphology of LDH and nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). Moreover, the thermal properties were determined by thermogravimetric analysis (TGA) and thermal degradation mechanism was discussed.     

Synthesis and characterization of ethylene vinyl acetate/Mg–Al layered double hydroxide nanocomposites

Mg–Al layered double hydroxide (LDH)/Ethylene vinyl acetate (EVA‐28) nanocomposites were prepared through solution intercalation method using organically modified layered double hydroxide (DS‐LDH). DS‐LDH was made by the intercalation of sodium dodecyl sulfate (SDS) ion. The structure of DS‐LDH and its nanocomposites with EVA‐28 was determined by X‐ray diffraction (XRD) and transmission electron microscope (TEM) analysis. XRD analysis shows that the original peak of DS‐LDH shifted to lower 2θ range and supports the formation of intercalated nanocomposites while, TEM micrograph shows the presence of partially exfoliated LDH nanolayers in addition to orderly stacked LDH crystallites in the polymer matrix. The presence of LDH in the nanocomposites has been confirmed by Fourier transform infrared (FTIR) analysis. The mechanical properties show significant improvement for the nanocomposite with respect to neat EVA‐28. Thermogravimetric (TGA) analysis shows that thermal stability of the nanocomposites is higher than that of EVA‐28. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1845–1851, 2007     

Preparation and flame resistance properties of revolutionary self-extinguishing epoxy nanocomposites based on layered double hydroxides

Layered double hydroxides/epoxy (LDHs/EP) nanocomposites were prepared from organo-modified LDHs, a diglycidyl ether of bisphenol A monomer (DGEBA) and amine curing agents. The organo-modified LDHs were obtained by ionic exchange of a magnesium-aluminum carbonate LDH in an acid medium. X-ray diffraction and transmission electron microscopy showed a dispersion of the layers at a nanometer scale, indicating the formation of LDH/EP nanocomposites. The thermal degradation and flame resistance properties of LDH/EP nanocomposites, montmorillonite-epoxy (MMT/EP) nanocomposites, LDH/EP microcomposites and aluminum hydroxide-epoxy microcomposites were compared by thermogravimetrical analyses, simultaneous thermal analyses, UL94 and cone calorimeter tests. Only LDH/EP nanocomposites showed self-extinguishing behavior in the horizontal UL94 test; LDH/EP microcomposites and MMT/EP nanocomposites samples burned completely showing that the unique flame resistance of LDH/EP nanocomposites is related to both the level of dispersion and the intrinsic properties of LDH clay. Furthermore, cone calorimeter revealed intumescent behavior for LDH/EP nanocomposites and a higher reduction in the peak heat release rate compared to MMT/EP nanocomposites.     

Preparation and properties of layered double hydroxide/poly(ethylene terephthalate) nanocomposites by direct melt compounding

Thermal, rheological and mechanical properties of layered double hydroxide (LDHs)/PET nanocomposites were investigated. To enhance the compatibility between PET matrix and LDHs, organic modification of parent LDH having carbonate anion was carried out using various anionic surfactants such as dodecylsulfate (DS), dodecylbenzenesulfonate (DBS), and octylsulfate(OS) by rehydration process. Then, PET nanocomposites with LDH content of 0, 1.0, and 2.0 wt% were prepared by direct melt-compounding. The dispersion morphologies were observed by transmission electron microscopy and X-ray diffraction, indicating that LDH-DS were exfoliated in PET matrix. From the rheology study, there are some network structures owing to filler-filler and/or filler-matrix interactions in nanocomposite systems. Consequently, DS intercalated LDH provided good compatibility with PET molecules, resulting in exfoliated LDH-DS/PET nanocomposites having enhanced thermal and mechanical properties as compared to other nanocomposites as well as homo PET.     

Synthesis and characterization of polyimide/silica hybrid nanocomposites

Polyimide/silica (PI/SiO₂) hybrid nanocomposites were prepared by the sol‐gel process directly from a soluble polyimide. This soluble PI was synthesized from a diamine with a pendant phenyl hydroxyl group, 4,4′‐diamino‐4″‐hydroxy triphenyl methane (DHTM) and a dianhydride, pyromellitic dianhydride (PMDA), followed by cyclodehydration. Three ways of preparing PI/SiO₂ hybrid nanocomposites were investigated in this study. Two of them used the coupling agent 3‐glycidyloxy propyl trimethoxysilane (GPTMOS) to enhance the compatibility between PI and silica. The coupling agent can react with the PI to form covalent bonds. The structures of the modified hybrid nanocomposites were identified with a FTIR, whereas the size of the silica in polyimides was characterized with a scanning electron microscope. The size of silica particles in the modified system was <100 nm. The covalently bonded PI/SiO₂ hybrid nanocomposites prepared by the novel third approach exhibited good transparency when the silica content was <15%. Moreover, their thermal and mechanical properties exhibited a significant improvement. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 382–393, 2004     

丙烯腈-苯乙烯磺酸共聚物/层状双金属氢氧化物纳米复合质子传导聚合物电解质的制备与表征

Acrylonitrile-sodium styrene sulfonate copolymer/layered double hydroxides nanocomposites were prepared by in situ aqueous precipitation copolymerization of acrylonitrile （AN） and sodium styrene sulfonate （SSS） in the presence of 4-vinylbenzene sulfonate intercalated layered double hydroxides （MgA1-VBS LDHs） and transferred to acrylonitrile-styrene sulfonic acid （AN-SSA） copolymer/LDHs nanocomposites as a proton-conducting polymer electrolyte. MgA1-VBS LDHs were prepared by a coprecipitation method, and the structure and composition of MgAl-VBS LDHs were determined by X-ray diffraction （XRD）, infrared spectroscopy, and elemental analysis. X-ray diffraction result of AN-SSS copolymer/LDHs nanocomposites indicated that the LDHs layers were well dispersed in the AN-SSS copolymer matrix. All the AN-SSS copolymer/LDHs nanocomposites showed significant enhancement of the decomposition temperatures compared with the pristine AN-SSS copolymer, as identified by the thermogravimetric analysis. The methanol crossover was decreased and the proton conductivity was highly enhanced for the AN-SSA copolymer/LDHs nanocomposite electrolyte systems. In the case of the nanocomposite electrolyte containing 2% （by mass） LDHs, the proton conductivity of 2.60×10^- 3 S·m^-1 was achieved for the polymer electrolyte.     

Comparison of morphology and mechanical properties of peroxide‐cured acrylonitrile butadiene rubber/LDH composites prepared from different organically modified LDHs

Rubber compounds based on acrylonitrile butadiene rubber (NBR) containing organically modified layered double hydroxides (LDHs) were prepared using peroxide as a curing agent. The LDHs intercalated by organic compounds including sodium styrene sulfonate (SSS) and sodium dodecylbenzene sulfonate (SDBS) were investigated using thermogravimetric analysis (TGA) and X‐ray diffraction (XRD) while the unmodified LDHs were used as contrast. Experimental results from TGA and XRD showed that both SSS‐ and SDBS‐intercalated LDHs were successfully obtained. The morphology of the LDH composites was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and XRD. The chemical structure of NBR/LDHs compounds were measured by Fourier transform infrared spectrum. The thermal properties were measured by TGA and differential scanning calorimetry. Other properties such as mechanical and swelling properties were also investigated. The results showed that a chemical bonding between organically modified LDHs and rubber matrix through SSS was built during vulcanization, which leads to improved interfacial strength of the cured compound. A high‐performance acrylonitrile butadiene rubber/SSS‐modified LDH compound, which has two times higher tensile strength than cured pure rubber without significant loss of elongation, was obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphology and properties of stearate‐intercalated layered double hydroxide nanoplatelet‐reinforced thermoplastic polyurethane

In the past few years, layered double hydroxides (LDHs) with monolayer structure have been much studied for the development of polymer nanocomposites. LDHs with intercalated stearate anions form a bilayer structure with increased interlayer spacing and are expected to be better nanofillers in polymers. In the work reported, thermoplastic polyurethane (PU)/stearate‐intercalated LDH nanocomposites were prepared by solution intercalation and characterized. X‐ray diffraction and transmission electron microscopy confirmed the exfoliation at lower filler loading followed by intercalation at higher filler loading in PU matrix. As regards mechanical properties, these nanocomposites showed maximum improvements in tensile strength (45%) and elongation at break (53%) at 1 and 3 wt% loadings. Maximum improvements in storage and loss moduli (20%) with a shift of glass transition temperature (15 °C) and an increase in thermal stability (32 °C) at 50% weight loss were observed at 8 wt% loading in PU. Differential scanning calorimetry showed a shift of melting temperature of the soft segment in the nanocomposites compared to neat PU, possibly due to the nucleating effect of stearate‐intercalated LDH on the crystal structure of PU. All these findings are promising for the development of mechanically improved, thermally stable novel PU nanocomposites. Copyright © 2011 Society of Chemical Industry     

Ethylene vinyl acetate/Mg‐Al LDH nanocomposites by solution blending

Partially exfoliated ethylene vinyl acetate (EVA‐40, 40% vinyl acetate content)/layered double hydroxide (LDH) nanocomposites using organically modified layered double hydroxide (DS‐LDH) have been synthesized by solution intercalation method. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) studies of nanocomposites shows the formation of exfoliated LDH nanolayers in EVA‐40 matrix at lower DS‐LDH contents and partially intercalated/exfoliated EVA‐40/MgAl LDH nanocomposites at higher DS‐LDH contents. These EVA‐40/MgAl LDH nanocomposites demonstrate a significant improvement in tensile strength and elongation at break for 3 wt% of DS‐LDH filler loading compare to neat EVA‐40 matrix. Thermogravimetric analysis also shows that the thermal stability of the nanocomposites increases with DS‐LDH content in EVA‐40. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synergistic effect of dual nanofillers (MWCNT and Ni–Al LDH) on the electrical and thermal characteristics of polystyrene nanocomposites

The advantage of using 3D hybrid filler containing carboxylic acid functionalized multiwalled carbon nanotubes (c‐MWCNTs) and sodium dodecyl sulfate modified Ni–Al layered double hydroxide (sN‐LDH) over c‐MWCNTs and sN‐LDHs acting alone was investigated. PS/c‐MWCNT composites proved to be good for improvement of properties, but not to an appreciable level, especially in case of electrical conductivity, flame retardancy, rheology, and water vapor permeability. Hence, a combination of 0.3 wt % of c‐MWCNT and 3 wt % of sN‐LDH was optimized as additives to assist in the full expression of the filler traits in the nanocomposite and to obtain a versatile nanocomposite with properties specific to both the fillers. This approach slightly decreases the dispersion challenge faced with handling high loadings of CNT and also the intrinsic limitations specific to the individual fillers (i.e., inertness of CNTs and low conductivity of LDHs). Moreover, the anion/anionic repulsion of organically modified CNT/LDH facilitates effective dispersion of the additive opposing adhesion. FTIR and Raman spectroscopy provided evidence for incorporation and proper dispersion of the additives in the polymer matrix, with XRD and TEM confirming a well‐dispersed morphology of the nanocomposites. In this work, focus is made on the improvement of thermal stability, flame retardancy, melt rheology, hardness, electrical conductivity, and water vapor permeability of PS/0.3 wt % c‐MWCNT/3 wt % sN‐LDH nanocomposites over PS/0.3 wt % c‐MWCNT, making use of the synergistic effect of c‐MWCNT coupled with sN‐LDH on polystyrene. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46513.