Realizing the enhancement of interfacial interaction in semicrystalline polymer/filler composites via interfacial crystallization

Polymer/filler composites have been widely used in various areas. One of the keys to achieve the high performance of these composites is good interfacial interaction between polymer matrix and filler. As a relatively new approach, the possibility to enhance polymer/filler interfacial interaction via crystallization of polymer on the surface of fillers, i.e., interfacial crystallization, is summarized and discussed in this paper. Interfacial crystallization has attracted tremendous interest in the past several decades, and some unique hybrid crystalline structures have been observed, including hybrid shish-kebab and hybrid shish-calabash structures in which the filler served as the shish and crystalline polymer as the kebab/calabash. Thus, the manipulation of the interfacial crystallization architecture offers a potential highly effective route to achieve strong polymer/filler interaction. This review is based on the latest development of interfacial crystallization in polymer/filler composites and will be organized as follows. The structural/morphological features of various interfacial crystallization fashions are described first. Subsequently, various influences on the final structure/morphology of hybrid crystallization and the nucleation and/or growth mechanisms of crystallization behaviors at polymer/filler interface are reviewed. Then recent studies on interfacial crystallization induced interfacial enhancement ascertained by different research methodologies are addressed, including a comparative analysis to highlight the positive role of interfacial crystallization on the resultant mechanical reinforcement. Finally, a conclusion, including future perspectives, is presented.     

半结晶性聚合物/碳纳米管复合材料结晶行为的研究

介绍了碳纳米管对半结晶性聚合物结晶行为的影响:提高结晶动力学、改变晶型及影响晶体形貌等。针对碳纳米管和半结晶性聚合物之间的界面相互作用,综述了两者之间的界面结晶问题,包括外延结晶、纳米杂化串晶、横晶的形成,以及一些相应的形成机制。最后对半结晶性聚合物/碳纳米管复合材料结晶行为的研究进行了展望。     

Morphology,crystallization, and mechanical properties of poly(ethylene terephthalate)/multiwall carbon nanotube nanocomposites via in situ polymerization with very low content of multiwall carbon nanotubes

So far, the reported content of multiwall carbon nanotubes (MWNTs) in polymer/MWNTs nanocomposites is usually above 0.1 wt %. In this article, we will report our work on the study of the morphology, crystallization, and mechanical properties of poly(ethylene terephthalate) (PET)/MWNTs nanocomposites prepared by in situ polymerization with very low content of MWNTs (from 0.01 to 0.2 wt %). Well‐dispersed MWNTs with a big network throughout PET matrix were observed by SEM. The very small amount of MWNTs displayed a great nucleating effect on the PET crystallization. The crystallization temperature was improved for 6.4°C by using only 0.01 wt % MWNTs. The decreased chain mobility of PET by adding MWNTs was evident by the formation of imperfect or smaller/thinner crystallites with low melting temperature. An increased storage modulus was also achieved for the nanohybirds with MWNT content less than 0.05 wt %. Our result indicates that using very low content MWNTs (less than 0.1 wt %) is a simple way to achieve good dispersion, yet with remarkable enhancement for polymer/MWNTs modification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3695–3701, 2007     

Nonisothermal crystallization kinetics and thermomechanical properties of multiwalled carbon nanotube‐reinforced poly(ε‐caprolactone) composites

BACKGROUND: The technological development of poly(ε‐caprolactone) (PCL) is limited by its short useful lifespan, low modulus and high crystallinity. There are a few papers dealing with the crystallization behavior of carbon nanotube‐reinforced PCL composites. However, little work has been done on the crystallization kinetics of melt‐compounded PCL/multiwalled carbon nanotube (MWNT) nanocomposites. In this study, PCL/MWNT nanocomposites were successfully prepared by a simple melt‐compounding method, and their morphology and mechanical properties as well as their crystallization kinetics were studied. RESULTS: The MWNTs were observed to be homogeneously dispersed throughout the PCL matrix. The incorporation of a very small quantity of MWNTs significantly improved the storage modulus and loss modulus of the PCL/MWNT nanocomposites. The nonisothermal crystallization behavior of the PCL/MWNT nanocomposites exhibits strong dependencies of the degree of crystallinity (X_c), peak crystallization temperature (T_p), half‐time of crystallization (t_1/2) and Avrami exponent (n) on the MWNT content and cooling rate. The MWNTs in the PCL/MWNT nanocomposites exhibit a higher nucleation activity. The crystallization activation energy (E_a) calculated with the Kissinger model is higher when a small amount of MWNTs is added, then gradually decreases; all the E_a values are higher than that of pure PCL. CONCLUSION: This paper reports for the first time the preparation of high‐performance biopolymer PCL/MWNT nanocomposites prepared by a simple melt‐compounding method. The results show that the PCL/MWNT nanocomposites can broaden the applications of PCL. Copyright © 2008 Society of Chemical Industry     

Crystallization behavior of polyamide 11/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC) was used to investigate the isothermal and nonisothermal crystallization kinetics of polyamide11 (PA11)/multiwalled carbon nanotube (MWNTs) composites. The Avrami equation was used for describing the isothermal crystallization behavior of neat PA11 and its nanocomposites. For nonisothermal studies, the Avrami model, the Ozawa model, and the method combining the Avrami and Ozawa theories were employed. It was found that the Avrami exponent n decreased with the addition of MWNTs during the isothermal crystallization, indicating that the MWNTs accelerated the crystallization process as nucleating agent. The kinetic analysis of nonisothermal crystallization process showed that the presence of carbon nanotubes hindered the mobility of polymer chain segments and dominated the nonisothermal crystallization process. The MWNTs played two competing roles on the crystallization of PA11 nanocomposites: on the one hand, the MWNTs serve as heterogeneous nucleating agent promoting the crystallization process of PA11; on the other hand, the MWNTs hinder the mobility of the polymer chains thus retarding the crystal growth process of PA11. The activation energies of PA11/MWNTs composites for the isothermal and nonisothermal crystallization are lower than neat PA11. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Morphology and mechanical property changes in compatibilized high density polyethylene/polyamide 6 nanocomposites induced by carbon nanotubes

Addition of carbon nanotubes to immiscible polymer blends with co‐continuous morphology features to improve the electrical conductivity has attracted much attention in recent years; however, less attention has been paid to the effect of carbon nanotubes on the morphology and corresponding physical properties of immiscible polymer blends with typical sea‐island morphology. In this work, therefore, functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into an immiscible high density polyethylene/polyamide 6 (HDPE/PA6) blend which was compatibilized by maleic anhydride grafted HDPE (HDPE‐MA). The distribution of FMWCNTs and the phase morphologies of the nanocomposites were characterized using scanning electron microscopy and transmission electron microscopy. The crystallization and melting behaviors of the components were analyzed by differential scanning calorimetry, which is thought to be favorable for an understanding of the distribution of FMWCNTs. It is interesting to observe that the morphology of PA6 particles is very dependent on the method of preparation of the nanocomposites. Correspondingly, FMWCNTs exhibit an apparent reinforcement effect and/or an excellent toughening effect for the compatibilized HDPE/PA6 blend, depending upon their distribution state and the variation of PA6 morphology. This work proves that FMWCNTs have a potential application in further improving the mechanical properties of compatibilized immiscible polymer blends. Copyright © 2012 Society of Chemical Industry     

Strengthening of poly(butylene adipate-co-terephthalate) by melt blending with a liquid crystalline polymer

Poly(butylene adipate-co-terephthalate) (PBAT) is a soft biodegradable polymer with a low melting temperature. PBAT has been melt-blended with a liquid crystalline polymer (LCP) aiming at preparing a new biodegradable polymer blend with improved mechanical properties. The phase structure and crystalline morphologies of the PBAT/LCP blends were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). It was found that the LCP domains are precisely dispersed in the PBAT matrix and that these domains act as the nuclei for PBAT crystallization. The nonisothermal crystallization temperature from the melt was dramatically shifted from 50°C to about 95°C by the addition of 20% LCP. In addition, the tensile modulus of the prepared blends increases gradually with increasing LCP content, indicating the excellent strengthening effects of LCP on the PBAT matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The characteristics of carbon nanotube‐reinforced poly(phenylene sulfide) nanocomposites

Multiwall carbon nanotube reinforced poly (phenylene sulfide) (PPS) nanocomposites were successfully fabricated through melt compounding. Structural, electrical, thermal, rheological, and mechanical properties of the nanocomposites were systematically studied as a function of carbon nanotube (CNT) fraction. Electrical conductivity of the polymer was dramatically enhanced at low loading level of the nanotubes; the electrical percolation threshold lay between 1 and 2 wt % of the CNTs. Rheological properties of the PPS nanocomposites also showed a sudden change with the CNT fraction; the percolation threshold was in the range of 0–0.5 wt % of CNTs. The difference in electrical and rheological percolation threshold was mainly due to the different requirements needed in the carbon nanotube network in different stages. The crystallization and melting behavior of CNT‐filled PPS nanocomposites were studied with differential scanning calorimetry; no new crystalline form of PPS was observed in the nanocomposites, but the crystallization rate was reduced. The thermal and mechanical properties of the nanocomposites were also investigated, and both of them showed significant increase with CNT fraction. For 5 wt % of CNT‐filled PPS composite, the onset of degradation temperature increased by about 13.5°C, the modulus increased by about 33%, and tensile strength increased by about 172%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal Crystallization and Melting Behaviors of PP/PA6/TiO2 Nanocomposites

Titanium dioxide nanoparticles were functionalized with toluene-2,4-diisocyanate and then polypropylene/polyamide 6 blends containing functionalized titanium dioxide were prepared using a twin-screw extruder. The nonisothermal crystallization and melting behaviors of the as-prepared nanocomposites were investigated using differential scanning calorimetry. The nonisothermal crystallization differential scanning calorimetry data were analyzed by the modified-Avrami (Jeziorny) and combination of Ozawa and Avrami (Mo) methods. It can be found that the Jeziorny method can be used to describe the main crystallization process, and the Mo method can better deal with nonisothermal crystallization kinetics of the polypropylene and polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. The nonisothermal crystallization analysis shows that the titanium dioxide nanoparticles have two effects on polypropylene/polyamide 6 blends, i.e., it can favor the improvement of crystallization ability and decrease the crystallization rate of the polypropylene and polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. For one thing, the functionalized titanium dioxide nanoparticles in the polypropylene/polyamide 6-based nanocomposites act as effective nucleation agents and result in higher crystallization temperature (T₀) than that of the polypropylene and polyamide 6 in pure polypropylene/polyamide 6 blends, which indicated titanium dioxide nanoparticles favor the improvement of crystallization ability of the polypropylene and polyamide 6 phase. For another, the existence of functionalized titanium dioxide nanoparticles hinders the free movement of polymer chains and results in lower crystallinity than that of the polypropylene and polyamide 6 in pure polypropylene/polyamide 6 blends, which indicated titanium dioxide nanoparticles decrease the crystallization rate of the polypropylene and polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. The nonisothermal crystallization melting behaviors show that there is single or double melting peak, which varies with different cooling rates for the polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. Multiple melting peak is mainly caused by the different crystalline structure of the polyamide 6 phase, the melting peak I is mainly caused by γ crystal of the polyamide 6 phase, while the melting peak II corresponds to the thermodynamic stability of α crystal. Besides, the recrystallization of the polyamide 6 phase in the heating process, and the effect of the incorporation of the titanium dioxide nanoparticles may have some contributions to the appeared multiple melting peak of the polyamide 6 phase in the polypropylene/polyamide 6-based nanocomposites.     

Crystallization behavior of carbon nanofiber/linear low density polyethylene nanocomposites

Crystallization behavior of LLDPE nanocomposites is reported in the presence of three types of carbon nanofibers (CNFs) (MJ, PR‐19, and PR‐24). During nonisothermal crystallization studies, all three crystalline melting peaks for LLDPE matrix were observed in the presence of PR‐19 nanofibers (up to 15 wt % content), but only the high‐ and low‐temperature peaks were observed in the presence MJ nanofibers. The broad melting peak at low‐temperature became bigger, suggesting an increase in the relative content of thinner lamellae in the presence of MJ nanofibers. TEM results of nanocomposites revealed transcrystallinity of LLDPE on the surface of CNFs, and a slightly broader distribution of lamellar thickness. STEM studies revealed a rougher surface morphology of the MJ nanofibers relative to that of PR nanofibers. Also, BET studies confirmed a larger specific surface area of MJ nanofibers relative to that of PR nanofibers, suggesting that the larger and the rougher surface of MJ nanofibers contributes toward the different crystallization behavior of MJ/LLDPE nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Crystallization kinetics,structure, and rheological behavior of poly(ethylene terephthalate)/multilayer graphene oxide nanocomposites

This work aims to produce poly(ethylene terephthalate)/multilayer graphene oxide (mGO) nanocomposites via continuous melt mixing in twin-screw extrusion, and to study the changes in crystallization and melt flow behavior. Three mGO contents (0.05, 0.1, and 0.3 wt%) were used. Differential scanning calorimetry analyses showed that at 0.1 wt%, mGO acted best as nucleating agent, increasing the crystallization kinetics as well as the melt crystallization temperature (T_mc) by more than 20%. It was also observed that mGO increases the crystals perfection. The nucleating behavior was confirmed by X-ray diffraction and small angle X-ray scattering analyses, which showed a decrease in the composites' crystalline lamella thickness (l_c) and long period. X-ray microtomography data confirms that this behavior is significantly affected by the mGO agglomerates distribution and specific surface area inside the polymer matrix. The rheological behavior was studied under two different conditions. It was noticed that under lower shear stresses the mGO particles hinder the polymer flow, increasing the composites viscosity and the pseudo-solid character. However, under higher shear stresses, for example, when flowing through a die, the nanomaterial enters its “superlubricity state,” acting as a lubricant to the flow. This is industrially interesting, because it may allow the use of less severe processing parameters to produce the nanocomposites.     

Synthesis and characterization of poly(butylene succinate)/epoxy group functionalized organoclay

Poly(butylene succinate) (PBS)/clay nanocomposites were prepared by condensation polymerization of 1,4‐butanediol and succinic acid in the presence of an organoclay containing epoxy groups (TFC) and titanium(IV) butoxide as a catalyst. The intercalation and exfoliation of the clay layers in the resulting composite were examined using X‐ray scattering and transmission electron microscopy. The role of the epoxy groups of TFC was investigated for the improvement of the morphology of the composites. The silicate layers in the composite were exfoliated to a greater extent as the epoxy content of TFC was increased from 0.245 to 0.359 mmol g^?1, while only intercalated morphology was obtained when no epoxy was present. The improved morphologies were attributed to the enhanced interfacial interactions between PBS and TFC through a chemical reaction of the epoxy groups with the end groups of the PBS. The nonisothermal crystallization process of the composites as well as that of neat PBS is well represented by the Avrami equation as modified by Jeziorny [Jeziorny A, Polymer 19 :1142 (1978)]. The crystallization of the composite took place faster as the epoxy content of the clay increased, due to the more effective nucleation of the well‐dispersed TFC layers. Copyright © 2007 Society of Chemical Industry     

Controlled accommodation of metal nanostructures within the matrices of polymer architectures through solution-based synthetic strategies

Controlled accommodation of metal nanostructures (MNSs) into the matrix of a well-defined polymer architecture offers an effective approach to achieve hierarchically structured nanocomposites with tunable synergistic properties to broaden application potentials in the emerging fields of energy, environmental science, and medicine. This review focuses on the recently developed zero-dimensional and one-dimensional MNSs@polymer hybrid nanostructures obtained by solution-based synthetic strategies. Progress in the controlled synthesis of those hybrid nanostructures in terms of the number (e.g., monomer, dimer and trimer), organization manner (e.g., linear alignment or confined assembly in certain domains), and spatial arrangement (e.g., in the core and shell) of the MNSs within the distinct polymer matrices are detailed. The synergistic properties and potential applications of those MNSs@polymer hybrids associated with their compositions and morphologies are also reviewed.     

β-nucleated propylene–ethylene random copolymer filled with multi-walled carbon nanotubes: Mechanical,thermal and rheological properties

Nanocomposites of a β-nucleated propylene–ethylene random copolymer filled with different amounts of multi-walled carbon nanotubes (ΜWCNTs) were prepared by a melt mixing process. The complex crystalline structure that the samples exhibited was attributed to the strong α-nucleating effect of MWCNTs and the presence of calcium pimelate, as it was revealed by X-ray diffraction. It was found that the presence of MWCNTs at concentrations higher than 2.5 wt.% practically diminishes the effect of the β-nucleating agent, and this was also reflected on the mechanical properties of the samples. The quality of MWCNT dispersion in the polymer matrix was evaluated by transmission electron microscopy. Mechanical and thermal properties of the nanocomposites were studied as a function of the crystalline structure and the filler content by tensile and impact testing, thermogravimetric analysis and differential scanning calorimetry. A crystallization kinetics study was also performed in order to export conclusions regarding the rates and parameters of crystallization.     

Synthesis and characterization of bionanocomposites of poly(lactic acid) and TiO2 nanowires by in situ polymerization

Bionanocomposites from biopolymers and inorganic nanoparticles are of great interest for packaging materials due to their enhanced physical, thermal, mechanical, and processing characteristics. In this study, poly(lactic acid) (PLA) nanocomposites with covalent bonding between TiO₂ nanowire surface and PLA chains were synthesized through in situ melt polycondensation. Molecular weight, structure, morphology, and thermal properties were characterized. Fourier transform infrared spectroscopy confirmed that PLA chains were covalently grafted onto TiO₂ nanowire surface. Transmission electron microscopy images also revealed clearly a third phase presence on the nanowires after the grafting process. Those grafted PLA chains exhibited significantly increased glass transition temperature and thermal stability, compared with pure PLA. The weight-average molecular weight of PLA/2% TiO₂ nanowire bulk nanocomposites increased by 66% compared with that of pure PLA. The electron microscopy results showed that strong interfacial interaction and homogeneous distribution were achieved between inorganic nanowires and organic PLA matrix in the bulk nanocomposites. The PLA matrix in bulk nanocomposites exhibited elevated glass transition temperature and decreased crystallization ability as the TiO₂ nanowire concentrations were increased from 0 to 2%.     

Morphology,crystallization, and mechanical properties of poly(ethylene terephthalate)/multiwalled carbon nanotubes composites

Poly(ethylene terephthalate)/multiwalled carbon nanotubes (PET/MWCNTs) with different MWCNTs loadings have been prepared by in situ polymerization of ethylene glycol (EG) containing dispersed MWCNTs and terephthalic acid (TPA). From scanning electronic microscopy images of nanocomposites, it can be clearly seen that the PET/MWCNTs composites with low‐MWCNTs contents (0.2 and 0.4 wt %) get better MWCNTs dispersion than analogous with high‐tube loadings (0.6 and 0.8 wt %). The nonisothermal crystallization kinetics was analyzed by differential scanning calorimetry using Mo kinetics equation, and the results showed that the incorporation of MWCNTs accelerates the crystallization process obviously. Mechanical testing shows that, in comparison with neat PET, the Young's modulus and the yield strength of the PET nanocomposites with incorporating 0.4 wt % MWCNTs are effectively improved by about 25% and 15%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Construction of electrostatic and π–π interaction to enhance interfacial adhesion between carbon nanoparticles and polymer matrix

In this study, an efficient method by constructing electrostatic and π–π interaction to enhance interfacial adhesion of nanocomposites was contrived. As commercial products and commonly used reinforcements, carbon nanotubes (CNTs) and graphene oxide (GO) were selected as fillers. Two kinds of interactions between carbon nanoparticles and polymer matrix were constructed by adding auxiliary comonomers (ACMs) into nanocomposites, in which one was the electrostatic interaction between quaternary ammonium cationic groups on ACMs as well as oxygen-containing groups of carbon nanoparticles, while the other was the π–π interaction between benzene rings on ACMs and conjugated structure on nanoparticles. Poly(methyl methacrylate) (PMMA) was chosen as a polymer matrix. It was found that carbon nanoparticles dramatically improved properties of nanocomposites, including thermal and mechanical performances due to the construction of electrostatic and π–π interaction on the interface. Compared with PMMA, the tensile strength of CNTs and GO reinforced nanocomposites was improved by 43.1 and 57.5%, respectively. The thermal decomposition temperature of CNTs and GO reinforced nanocomposites was improved by 21 and 23°C, respectively. Interesting and convincing results proved that the construction of multiple interactions can provide a promising method to effectively enhance interfacial adhesion of nanocomposites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48633.     

Mechanical and thermal properties of polyphenylene sulfide/multiwalled carbon nanotube composites

Polyphenylene sulfide (PPS)/multiwalled carbon nanotube (MWCNT) composites were prepared using a melt‐blending procedure combining twin‐screw extrusion with centrifugal premixing. A homogeneous dispersion of MWCNTs throughout the matrix was revealed by scanning electron microscopy for the nanocomposites with MWCNT contents ranging from 0.5 to 8.0 wt %. The mechanical properties of PPS were markedly enhanced by the incorporation of MWCNTs. Halpin‐Tsai equations, modified with an efficiency factor, were used to model the elastic properties of the nanocomposites. The calculated modulus showed good agreement with the experimental data. The presence of the MWCNTs exhibited both promotion and retardation effects on the crystallization of PPS. The competition between these two effects results in an unusual change of the degree of crystallinity with increasing MWCNT content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fractional Crystallization Kinetics of Poly(ethylene oxide) in Its Blends with Poly(butylene succinate): Molecular Weight Effects

The fractional crystallization kinetics and phase behavior of PEO with different molecular weights (MWs) in its miscible crystalline/crystalline blends with PBS are studied. Both fractional crystallization kinetics and phase segregation of PEO in PBS/PEO blends are dramatically influenced by its MW. PEO with a medium MW (20 kDa) shows a significant fractional crystallization in the blends with PBS crystallized at a high T_IC,PBS, which, however, is dramatically depressed in the blends with a very low or high MW of PEO. This indicates that the PEO component with a medium MW is more ready to segregate into the interlamellar region of PBS crystals than those with a very low or high MW. The MW‐dependent fractional crystallization kinetics and phase segregation of PEO component in the PBS/PEO blends are discussed.

     

聚丁二酸丁二酯的结晶动力学研究

采用氯仿溶解聚丁二酸丁二酯（PBS）,然后利用甲醇逐级沉淀分离获得不同相对分子质量及其分布的PBS级分,分别采用差示扫描量热仪、广角X射线衍射仪、偏光显微镜等对不同级分PBS的等温和非等温结晶动力学、晶体形态及结构进行了系统研究。结果表明,随着相对分子质量的增加和相对分子质量分布的变宽,各级分的半结晶时间逐渐降低,结晶半峰宽逐渐变窄,结晶度逐渐增加;但各级分PBS的晶型和晶貌并未发生明显的转变。