Studies on crystallization behaviors and crystal morphology of polyamide 66/clay nanocomposites

X‐ray diffraction methods, DSC thermal analysis, and polarized light microscopy (PLM) were used to investigate the structural changes of nylon 66/clay nanocomposites. PA 66/clay nanocomposites were prepared by the method of melt intercalation. The results indicate that the addition of the intercalated organo‐montmorillonite (OMMT) can induce generation of the β‐form crystal of PA 66 and substantially affect the arrangement of molecules in the α‐form crystal, although the crystallinity scarcely changes. Also, the DSC results indicate that the addition of OMMT in the PA 66 matrix leads to increases of crystallization temperatures and the full width at half maximum (FWHM) of the exothermic peaks. Moreover, the viscosity factor is the main influence on FWHM of the exothermic peaks of PA 66/clay nanocomposites. The results of nonisothermal crystallization kinetics show that OMMT has the effect of heterogeneous nucleation and leads to the decrease of the size of the spherocrystal. The heterogeneous nucleation effects of OMMTs influence the mechanism of crystallization and the growth mode of PA 66 crystals. PLM photographs verify that the size of spherocrystal is decreased and visually confirm the theory of crystallization kinetics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 756–763, 2005     

Isothermal crystallization behavior of polyamide 6,6/multiwalled carbon nanotube nanocomposites

The good dispersion of functionalized multiwalled carbon nanotube (f‐MWCNT) in polyamide 6,6 (PA 6,6) matrix was prepared by solution mixing techniques. The crystalline structure and crystallization behaviors of PA 6,6 and PA 6,6/f‐MWCNT nanocomposites were studied by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analysis. DSC isothermal results revealed that the overall isothermal crystallization rates of PA 6,6 increased as well as the activation energy of PA 6,6 extensively decreased by adding f‐MWCNT into PA 6,6, suggesting that the addition of f‐MWCNT probably induces the heterogeneous nucleation. The effect of f‐MWCNT on the chain arrangement for the crystallization of PA 6,6/f‐MWCNT nanocomposites was also discussed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Preparation and characterization of sepiolite‐poly(ethyl methacrylate) and poly(2‐hydroxyethyl methacrylate) nanocomposites

Poly(ethyl methacrylate) (PEMA) and poly(2‐hydroxyethyl methacrylate) (PHEMA) nanocomposites with sepiolite in pristine and silylated form were prepared using the solution intercalation method and characterized by the measurements of XRD, TEM, FTIR‐ATR, TG/DTG, and DSC. The TEM analysis indicated that the volume fraction of fibers in sepiolite decreased and the fiber bundles dispersed in PEMA and PHEMA at a nanometer scale. These results regarding TEM micrographs were in agreement with the data obtained by XRD. The increase in thermal stability of nanocomposites of PEMA is higher than that of PHEMA according to the data obtained from TG curves. The DTG analysis revealed that sepiolite/modified sepiolite caused some changes, as confirmed by FTIR in the thermal degradation mechanism of the polymers. T_g temperatures of PEMA and PHEMA usually increased upon the addition of sepiolite/modified sepiolite. In addition, modification of sepiolite with 3‐APTS had a slight influence on thermal properties of the nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Polymer‐Clay Nanocomposites Based on Blends of Polyamide‐6 and Polyethylene

The preparation of polyamide‐6/clay, high‐density polyethylene/clay, and high‐density polyethylene/ polyamide‐6/clay nanocomposites is considered. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier Transform Infrared (FTIR) measurements show that the clay enhances the crystallization of the γ‐form of polyamide‐6. The clay also acts as a nucleation agent and causes a reduction of spherulitte size. Scanning electron microscopy (SEM) analysis of fracture surfaces shows that the clay reduces the PA‐6 particle size in the HDPE/PA‐6/clay nanocomposites and changes the morphology. Mechanical properties and the effect of maleated polyethylene are also reported.     

Laser transmission welding of poly(lactic acid) and polyamide66/sepiolite nanocomposites

Influence of sepiolite nanoclay on the properties of the resulting join between poly(lactic acid) (PLA) and different Polyamide66 (PA66)/nanoclay nanocomposites was studied in this work. Six different polymer nanocomposites based on PA66 were manufactured through a melt compounding process by adding a fixed 1.64 wt % of a commercial IR absorber additive and the respective weight percentages of sepiolite to the polymer matrix. Several nanocomposite/PLA joints were finally performed by means of the transmission laser welding technology and the resulting weldings were characterized in terms of mechanical properties by performing peeling and shearing tests. Furthermore, both welded and mechanically tested samples were also analyzed by scanning electron microscopy in order to study the morphology of the weld seam. The results of the performed tests show that the addition of sepiolite to the PA66 improves the welding performance only in those cases in which the percentage of sepiolite of the nanocomposites is higher than 5 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46638.     

Characterization and charge transfer mechanism of PIN–cdse nanocomposites

This paper reports structural, thermal, and temperature‐dependent dielectric properties of polyindole–cadmium selenide (PIN–CdSe) nanocomposites. PIN and its nanocomposites were synthesized via in situ chemical oxidative polymerization method. Samples were characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), scanning electron microscopy with energy dispersive X‐ray (SEM/EDX), atomic force microscope, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Dielectric properties were analyzed as a function of temperature. FT‐IR spectroscopy indicated that both N H and aromatic CC bonds were affected more by doping process. Significant structural differences were observed in XRD and SEM analyses of PIN and its nanocomposites. Both XRD and DSC measurements revealed that crystallinity of the PIN increases to a certain degree with increasing doping level. Thermogravimetric analysis showed that addition of CdSe decreased degradation temperature of the PIN. Conductivity measurements investigated by universal power law indicated that the charge transport mechanism of all the samples is consistent with correlated barrier hopping model. POLYM. COMPOS., 37:3057–3065, 2016. © 2015 Society of Plastics Engineers     

Effect of sepiolite on the crystallization behavior of biodegradable poly(lactic acid) as an efficient nucleating agent

To enhance the crystallization kinetics of poly(lactic acid) (PLA), fibrous sepiolite was explored for nucleating the crystallization of PLA. PLA/sepiolite nanocomposites were prepared via the melt‐extrusion method. The effect of sepiolite on the crystallization behavior, spherulite growth and crystal structure of PLA were investigated by means of differential scanning calorimetry (DSC), polarized optical microscope (POM), wide angle X‐ray diffraction (WAXD), Fourier transform infrared (FTIR), and scanning election microscope (SEM). On the basis of DSC and POM results, the overall crystallization kinetics of PLA/sepiolite nanocomposites were significantly enhanced leading to higher crystallinity and nucleation density, faster spherulite growth rate (G) and lower crystallization half‐time (t_1/2) compared with the neat PLA. Under non‐isothermal conditions, the PLA blend comprising 1.0 wt% of sepiolite still revealed two crystallization peaks upon cooling at a rate of 35°C/min. Above phenomena strongly suggested that sepiolite was an effective nucleating agent for PLA. FTIR and WAXD analyses confirmed that the crystal structure of PLA matrix was the most common α‐form. SEM micrographics illustrated the fine three‐dimensional spherulite structures with the lath‐shape lamellae regularly arranged in radial directions. POLYM. ENG. SCI., 55:1104–1112, 2015. © 2014 Society of Plastics Engineers     

Characterization of nanocomposite resol resins: Individual/synergist effects of alendronic acid and sepiolite

Alendronic acid modified resol nanocomposite resins (AA‐PFNCRs) and sepiolite modified resol nanocomposite resins (SEP‐PFNCRs) have been synthesized by in situ method in the presence of base catalyst. Additionally, the synergistic effects of alendronic acid and sepiolite clay (AA‐SEP‐PFNCR) on the resol resin have been studied. The structure, morphology, and thermal properties of these nanocomposites have been investigated by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and X‐ray Diffraction (XRD). The results demonstrated the interactions between the fillers and resol resin. Thermal properties of nanocomposite resins were improved due to alendronic acid and sepiolite. The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43807.     

良好分散尼龙6/多壁碳纳米管复合材料的研究

采用柔和混合法制备纳米粒子良好分散的尼龙-6/多壁碳纳米管(PA6/MWNTs)复合材料,采用差示扫描量热仪(DSC)和广角X射线衍射法(XRD)研究了MWNTs对PA6基体结晶熔融行为的影响。DSC结果表明,MWNTs的加入大幅度地提高了PA6的结晶温度(最高提高约20℃),基体的结晶度也有所提高,说明良好分散的MWNTs在PA6结晶过程中呈现明显的异相成核作用;XRD结果证实,分散良好的MWNT促进PA6形成α晶型,抑制γ晶型的形成。同时,MWNT的加入导致复合材料出现熔融双峰现象,其形状随MWNT含量的变化而改变,双峰结构可能是由于熔融过程中伴随着重结晶而引起的。     

Morphology and Crystallization of Biobased Polyamide 56 Blended with Polyethylene Terephthalate

This study attempts to promote biobased polyamide 56 (PA56) as a sustainable candidate to replace commercial PA6 and PA66 when blended with polyethylene terephthalate (PET). Scanning and transmission electron microscopy of the blends with different PA56 contents reveals an immiscible morphology with an increase in the size of the dispersed domains by increasing PA56 content. The steady‐state mixing torque of the kneader is decreased to half by adding 10 wt% of PA56 to PET. Further addition of PA56 gradually increases this torque but does not surpass the neat PET sample up to 30 wt% of PA56. As revealed by microscopic dissipative particle dynamics (DPD) simulations, this gradual increase is ascribed to the difficulty to disperse larger domains of PA56 in the thermodynamically undesired PET. The results confirm that PA56 has a lubricating effect in PET. Using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD) techniques, it is shown that PA56 acts as a nucleating agent in PET. This leads to the formation of numerous small crystals in the blends as opposed to several large crystals in the neat samples. The results encourage the use of PA56 biomaterial in combination with PET in products such as bicomponent segmented pie fibers.     

Preparation and properties of unsaturated polyester nanocomposites based on silylated sepiolite nanofibers

The novel surface‐modified sepiolite/unsaturated polyester (sepiolite/UP) nanocomposites were prepared by in situ polymerization. Sepiolite fibers were first organo‐modified by grafting of vinyltriethoxysilane (VTS) containing a double bond onto the surfaces and used as nanofillers. The morphology of sepiolites and nanocomposites were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and transmission electron microscope (TEM). Moreover, the thermal properties were determined by thermogravimetric analysis (TGA) and the thermal degradation mechanism was discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of linear low‐density polyethylene/sepiolite nanocomposites

Linear low‐density polyethylene (LLDPE)/sepiolite nanocomposites were prepared by melt blending using unmodified and silane‐modified sepiolite. Two methods were used to modify sepiolite: modification before heat mixing (ex situ) and modification during heat mixing (in situ). The X‐ray diffraction results showed that the position of the main peak of sepiolite remained unchanged during modification step. Infrared spectra showed new peaks confirming the development of new bonds in modified sepiolite and nanocomposites. SEM micrographs revealed the presence of sepiolite fibers embedded in polymer matrix. Thermogravimetric analysis showed that nanocomposites exhibited higher onset degradation temperature than LLDPE. In addition, in situ modified sepiolite nanocomposites exhibited higher thermal stability than ex situ modified sepiolite nanocomposites. The ultimate tensile strength and modulus of the nanocomposites were improved; whereas elongation at break was reduced. The higher crystallization temperature of some nanocomposite formulations revealed a heterogeneous nucleation effect of sepiolite. This can be exploited for the shortening of cycle time during processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of a synthetic ureido nucleating agent on crystallization behavior and mechanical properties of polyamide 6

A synthetic ureido mixture prepared from the reaction of 4,4′‐diphenylmethane disocynanate (MDI) and cyclohexylamine without using any harmful organic solvents, has been used as a nucleating agent (PNA) for polyamide 6 (PA6). The effect of PNA on the crystallization and mechanical properties of PA6 has been studied by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM), tensile test, melt flow index (MFI), and X‐ray diffraction (XRD). The results show that PNA is an effective nucleation agent for PA6. PNA affects the nucleation mechanism of PA6, and substantially accelerates the crystallization rate of PA6 and gives rise to smaller crystal size. In comparison with PA6, the crystallization temperature (T_c) of PA6/PNA (100/0.5) increases 21.3°C and the degree of sub‐cooling (ΔT_c) decreases 23.7°C. Furthermore, because of the heterogeneous nucleation induced by PNA, the spherulites of PA6 become even and tiny based on POM observation. Polymorph transform has been obtained from XRD analysis. The virgin PA6 is free of γ‐phase crystals, presented as α‐phase crystals in this study, but γ‐phase crystal appears after the introduction of PNA. The mechanical and thermal properties of PA6 are obviously improved by the addition of PNA. POLYM. ENG. SCI., 55:2011–2017, 2015. © 2015 Society of Plastics Engineers     

Synthesis and characterization of poly(propylene carbonate)/modified sepiolite nanocomposites

A series of poly(propylene carbonate) (PPC)/modified sepiolite (mSp) nanocomposites with different mSp contents were prepared via a solution‐based processing method. The modified sepiolite was obtained by fabricating sepiolite with methyl trimethoxysilanes (MTMS) gel. The effect of mSp amount, in the range 1–10 wt%, on the morphology, mechanical properties, and thermal degradation of PPC was investigated by means of scanning electron microscopy (SEM), X‐ray diffractometry (XRD), static strenching analysis, thermogravimetric analyses (TGA), differential scanning calorimetry (DSC). Morphological studies showed the homogeneous dispersion of mSp in the PPC matrix whose structure remains amorphous. The nanoscale dispersion of mSp significantly enhanced the mechanical properties and thermal stability. The thermal motion and degradation of the polymer occur at higher temperature in the presence of mSp because of the strong interfacial adhesion between the two components. POLYM. COMPOS., 21–27, 2016. © 2014 Society of Plastics Engineers     

Effect of dendrimer‐like PAMAM grafted attapulgite on the microstructure and morphology of Nylon‐6

The effect of dendrimer‐like polyamidoamine grafted attapulgite (ATP‐PAMAM) on the microstructure and morphology of Nylon‐6 (PA6) was investigated. The ATP‐PAMAM nanoparticles were prepared by treating attapulgite (ATP) with heat and acid followed by grafting with polyamidoamine (PAMAM) molecules, which was confirmed by Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and dispersion state in formic acid. The X‐ray diffraction (XRD) analysis result indicated that the grafting modification was occurred on the surface of fibrous crystals and did not shift the crystal structure of ATP. PA6/ATP‐PAMAM (G_2.0) nanocomposites with different modified ATP content were prepared by melt compounding in a twin screw extruder. XRD measurements suggested that the intensity of diffraction peak of α crystalline form of PA6 decreased gradually as the inclusion of ATP‐PAMAM(G_2.0) into the PA6 matrix, while that of γ crystalline form increased gradually. The results of molau experiment and scanning electron microscopy (SEM) observation showed not only a uniform dispersion of ATP‐PAMAM(G_2.0) in the PA6 matrix but also a strong interfacial adhesion between them. Mechanical investigation (by tensile test) showed an obvious improvement in the presence of surface modified ATP. POLYM. COMPOS., 35:627–635, 2014. © 2013 Society of Plastics Engineers     

Crystallization behavior of PA66/SiO2 organic‐inorganic hybrid material

The poly 2‐hydroxy propylmethacrylate‐methyl methacrylate (PHPMA‐MMA)/SiO₂ composite, derived from 2‐hydroxy propylmethacrylate (HPMA), methyl methacrylate (MMA), and tetraethoxysilane (TEOS), was used to synthesize polyamide 66(PA66)/SiO₂ organic‐inorganic hybrid material. X‐ray diffraction (XRD) was used to investigate the lattice spacing change of the PA66/SiO₂ hybrid material. It was found that the addition of PHPMA‐MMA/SiO₂ composite nearly did not change the crystal form of PA66. The nonisothermal crystallization kinetics of PA66 and PA66/SiO₂ hybrid material was investigated by differential scanning calorimetry (DSC) with various cooling rates. At every given cooling rate, the start crystallization temperature of the PA66/SiO₂ hybrid material was higher than that of PA66, while the crystallization temperature range was narrower than that of PA66. Avrami analysis modified by the Jeziorny method, the Ozawa method, and a method developed by Liu were employed to describe the nonisothermal crystallization process of the samples. The results showed that the Jeziorny method and the Ozawa method were not suitable to describe the nonisothermal crystallization process of PA66/SiO₂ hybrid material; however, when the relative degree of crystallinity X (t) was less than 1 ? 1/e, ln [? ln (1 ? X (t))] was still linear to lnt. The Liu method was successful to describe the nonisothermal crystallization processes for both PA66 and the PA66/SiO₂ hybrid material. It was confirmed that the presence of PHPMA‐MMA/SiO₂ composite could increase the crystallization rate and had a hetero phase nucleation effect on the PA66 matrix. Moreover, the introduction of PHPMA‐MMA/SiO₂ could improve the crystallization active energy ?E calculated by the Kissinger equation, attributing to the strong interaction between the polyamide chains and the PHPMA‐MMA/SiO₂ composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 810–817, 2006     

OMMT对PE-HD/PA6合金的结晶性能和相容性的影响

研究了不同含量的有机蒙脱土（OMMT）对高密度聚乙烯/聚酰胺6（PE-HD/PA6）合金的结晶性能和微观结构的影响。X射线衍射和差示扫描量热仪分析表明,随着OMMT的含量的增加,PA6倾向于生成γ晶型;扫描电镜分析表明,对于PE-HD/PA6合金,PA6以球状分散在PE-HD基体中,相尺寸直径较大,为30~40 μm;添加OMMT后,PA6分子链的极性基团可以与OMMT层间表面产生强的相互作用,使得大分子链在熔融过程中进入OMMT层间,得到PE-HD/PA6/OMMT纳米复合材料。当添加3份OMMT后,复合材料中分散相PA6的相尺寸降低至10 μm,尺寸分布均匀,说明OMMT起到了相容剂的作用。同时,适量的OMMT提高了PE-HD/PA6合金对有机溶剂的阻透性。     

Effect of clay addition on the morphology and thermal behavior of polyamide 6

The nanostructure, morphology, and thermal properties of polyamide 6 (PA6)/clay nanocomposites were studied with X‐ray scattering, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The wide‐angle X‐ray diffraction (WAXD) and TEM results indicate that the nanoclay platelets were exfoliated throughout the PA6 matrix. The crystallization behavior of PA6 was significantly influenced by the addition of clay to the polymer matrix. A clay‐induced crystal transformation from the α phase to the γ phase for PA6 was confirmed by WAXD and DSC; that is, the formation of γ‐form crystals was strongly enhanced by the presence of clay. With various clay concentrations, the degree of crystallinity and crystalline morphology (e.g., spherulite size, lamellar thickness, and long period) of PA6 and the nanocomposites changed dramatically, as evidenced by TEM and small‐angle X‐ray scattering results. The thermal behavior of the nanocomposites was investigated with DSC and compared with that of neat PA6. The possible origins of a new clay‐induced endothermic peak at high temperature are discussed, and a model is proposed to explain the complex melting behavior of the PA6/clay nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1191–1199, 2007     

Crystallization and melting behavior of polyester/clay nanocomposites

Polyester/clay nanocomposites were prepared by melt compounding with different clay loadings. Comparing against neat polyester resins, the crystallization and multiple melting behavior of the nanocomposites was investigated by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). Nanoclay filler is an effective heterogeneous nucleating agent, as evidenced by a decrease and an increase in the crystallization temperature for both cold and melt crystallization of polyesters, respectively. The degree of crystallinity was found to increase with increasing clay content, due to heterogeneous nucleation effects by the addition of a nanofiller. For the annealed samples, multiple melting peaks were always observed for both neat polyester and its nanocomposites. The origins of the multiple melting behavior are discussed, based on the DSC and XRD results. Interestingly, an ‘abnormal’ high‐temperature endothermic peak (T_{m, 3}) at about 260 °C was observed when the nanocomposite samples were annealed at higher temperatures (eg ≥240 °C). The constrained polyester crystals formed within intercalated clay platelets due to confinement effects were probably responsible for this melting event at these higher temperatures. Copyright © 2004 Society of Chemical Industry     

Mechanical properties and nonisothermal crystallization kinetics of polyamide 6/functionalized TiO2 nanocomposites

Titanium dioxide (TiO₂) nanoparticles were pretreated with excessive toluene‐2,4‐diisocyanate (TDI) to synthesize TDI‐functionalized TiO₂ (TiO₂‐NCO), and then polymeric nanocomposites consisting of polyamide 6 (PA6) and functionalized‐TiO₂ nanoparticles were prepared via a melt compounding method. The interfacial interaction between TiO₂ nanoparticles and polymeric matrix has been greatly improved due to the isocyanate ( NCO) groups at the surface of the functionalized‐TiO₂ nanoparticles reacted with amino groups ( NH₂) or carboxyl ( COOH) groups of PA6 during the melt compounding and resulted in higher tensile and impact strength than that of pure PA6. The nonisothermal crystallization kinetics of PA6/functionalized TiO₂ nanocomposites was investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization DSC data were analyzed by the modified‐Avrami (Jeziorny) methods. The results showed that the functionalized‐TiO₂ nanoparticles in the PA6 matrix acted as effective nucleation agents. The crystallization rate of the nanocomposites obtained was faster than that of the pure PA6. Thus, the presence of functionalized‐TiO₂ nanoparticles influenced the mechanism of nucleation and accelerated the growth of PA6 crystallites. POLYM. COMPOS., 35:294–300, 2014. © 2013 Society of Plastics Engineers