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     

Phase separation and melting behavior in poly(ε‐caprolactone)‐epoxy blends cured by 3,3′‐dimethylmethylene‐di(cyclohexylamine)

The morphology and the melting behavior of poly(ε‐caprolactone)/epoxy blends (PCL/epoxy) have been investigated by SEM and DSC. The mechanism of phase separation varies with the curing temperature and PCL content, which can be deduced from the cured morphology of the blend. Higher temperature leads to lower blend viscosity and a higher curing rate, and the final morphology is determined by the competition of these two factors. The PCL melting behavior of the blend is influenced by the extent of phase separation and crystallization during curing. The dual melting behavior of the PCL blend can be ascribed to the interference of the epoxy, which results in the formation of less perfect PCL crystallites melted at lower temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3107–3114, 2003     

Essential work of fracture of poly(ϵ‐caprolactone)/boehmite alumina nanocomposites: Effect of surface coating

The essential work of fracture (EWF) approach was adopted to reveal the effect of nanofillers on the toughness of poly (?‐caprolactone) (PCL)/boehmite alumina (BA) nanocomposites. Synthetic BA particles with different surface treatments were dispersed into the PCL matrix by extrusion melt compounding. The morphology of the composites was studied by scanning electron microscopy. Differential scanning calorimetry and wide‐angle X‐ray scattering were used to detect changes in the crystalline structure of PCL. Also, mode I type EWF tests, dynamic mechanical analysis, and quasi‐static tensile tests were applied to study the effect of the BA nanofillers on the mechanical properties of the nanocomposites. BA was homogeneously dispersed and acted as heterogeneous crystallization nucleant and a nonreinforcing filler in PCL. The tensile modulus and yield strength slightly increased and the yield strain decreased with increasing BA content (up to 10 wt %). The effect of the BA surface treatment with octylsilane was negligible by contrast to that with alkylbenzene sulfonic acid (OS2). Like the tensile mechanical data, the essential and nonessential work of fracture parameters did not change significantly either. The improved PCL/BA adhesion in case of OS2 treatment excluded the usual EWF treatise. This was circumvented by energy partitioning between yielding and necking. The yielding‐related EWF decreased, whereas the nonessential EWF increased with BA content and with better interfacial adhesion. This was attributed to the effect of matrix/filler debonding. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal,mechanical, and rheological properties of poly(ε‐caprolactone)/halloysite nanotube nanocomposites

Naturally available halloysite nanotubes (HNTs) with hollow nanotubular structures were used as reinforcement in poly(ε‐caprolactone) (PCL). The PCL/HNT nanocomposites were prepared by melt mixing the polymer with as‐received HNTs up to 10 wt % in an internal batch mixer. Transmission electron microscopy analysis indicated that the HNTs were dispersed uniformly on the nanoscale throughout the PCL matrix. Differential scanning calorimeter studies revealed that the PCL crystallinity was decreased in the nanocomposites, and the HNTs dispersed in the PCL matrix led to an increase in the non‐isothermal crystallization temperature of the PCL. Tensile and dynamic mechanical tests showed great enhancement in strength and stiffness at low HNT content, while still maintaining the ductility of the PCL. The glass transition temperature (T_g) of the pristine PCL was substantially increased with increase in filler loading, which indicates good reinforcing effect imparted by the addition of HNT. Melt rheological studies revealed that the nanocomposites exhibited strong shear thinning behavior, and a percolated network of HNT particles was formed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Isothermal and nonisothermal crystallization kinetics of poly(ε‐caprolactone)/multi‐walled carbon nanotube composites

Differential scanning calorimeter (DSC) and polarized optical microscopy (POM) have been used to investigate the isothermal and nonisothermal crystallization behavior of poly(ε‐caprolactone) (PCL)/multi‐walled carbon nanotube (MWNT) composites. PCL/MWNT composites have been prepared by mixing the PCL polymer with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) in tetrahydrofuran solution. Raman spectrum of c‐MWNT indicated the possible presence of carboxylic acid groups at both ends and on the sidewalls of the MWNTs. The TEM micrograph showed that the c‐MWNT is well separated and uniformly dispersed in the PCL matrix. DSC isothermal results showed that the introduction of c‐MWNT into the PCL initiates strongly heterogeneous nucleation, which induced a change of the crystal growth process. The activation energy of PCL significantly decreases by adding 0.25 wt% c‐MWNT into PCL/c‐MWNT composites and then increases as c‐MWNT content increases. The result demonstrates that the addition of c‐MWNT into PCL induces the heterogeneous nucleation at lower c‐MWNT content and then inhibits the polymer chain transportation ability during crystallization at higher c‐MWNT content. In this study, we have also studied the nonisothermal crystallization kinetics and melting behavior of PCL/c‐MWNT composites at various cooling rates. The correlation among isothermal and nonisothermal crystallization kinetics and melting behavior of PCL/c‐MWNT composites can be also discussed. POLYM. ENG. SCI., 46:1309–1317, 2006. © 2006 Society of Plastics Engineers     

Low percolation threshold and high electrical conductivity in melt‐blended polycarbonate/multiwall carbon nanotube nanocomposites in the presence of poly(ε‐caprolactone)

This study focuses on the electrical properties of polycarbonate (PC)/poly(ε‐caprolactone) (PCL)‐multiwall carbon nanotube (MWCNT) nanocomposites. MWCNTs were incorporated into thermoplastic PC matrix by simple melt blending using biodegradable PCL based concentrates with MWCNT loadings (3.5 wt%). Because of the lower interfacial energy between MWCNT and PCL, the nanotubes remain in their excellent dispersion state into matrix polymer. Thus, electrical percolation in PC/PCL‐MWCNT nanocomposites was obtained at lower MWCNT loading rather than direct incorporation of MWCNT into PC matrix. AC and DC electrical conductivity of miscible PC/PCL‐MWCNT nanocomposites were studied in a broad frequency range, 10¹?10⁶ Hz and resulted in low percolation threshold (p_c) of 0.14 wt%, and the critical exponent (t) of 2.09 from the scaling law equation. The plot of logσ_DC versus p^?1/3 showed linear variation and indicated the existence of tunneling conduction among MWCNTs. At low MWCNT loading, the influence of large polymeric gaps between conducting clusters is the reason for the frequency dependent electrical conductivity. Transmission electron microscopy and field emission scanning electron microscopy showed that MWCNTs were homogeneously dispersed and developed a continuous interconnected network path throughout the matrix phase and miscibility behavior of the polymer blend. POLYM. ENG. SCI., 54:646–659, 2014. © 2013 Society of Plastics Engineers     

Crystallization and morphology studies of biodegradable poly(ε‐caprolactone)/silica nanocomposites

Biodegradable poly(ε‐caprolactone) (PCL)/silica nanocomposites at various silica loadings were prepared via direct melt compounding method in this work. Scanning electron microscopy observation indicated that when the silica content was < 3 wt%, the nanoparticles dispersed evenly in the PCL matrix and exhibited only aggregates with particle size of less than 100 nm. The results of nonisothermal melt crystallization showed that the crystallization peak temperature was higher in the nanocomposites than in neat PCL; moreover, the overall crystallization rate was faster in the nanocomposites than in neat PCL during isothermal melt crystallization. Both nonisothermal and isothermal melt crystallization studies suggested that the crystallization of PCL was enhanced by the presence of silica and influenced by the silica loading. The effect of silica on the crystallization behavior was twofold: the presence of silica may provide heterogeneous nucleation sites for the PCL crystallization while the aggregates of silica may restrict crystal growth of PCL. However, the crystal structure of PCL remained almost unchanged despite the presence of silica in the nanocomposites. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

Effective preparation and characterization of montmorillonite/poly(ε‐caprolactone)‐based polyurethane nanocomposites

In this study, montmorillonite (MMT)/poly(?‐caprolactone)‐based polyurethane cationomer (MMT/PCL‐PUC) nanocomposites were prepared and their mechanical properties, thermal stability, and biodegradability were investigated. PCL‐PUC has 3 mol % of quaternary ammonium groups in the main chain. The MMT was successfully exfoliated and well dispersed in the PCL‐PUC matrix for up to 7 wt % of MMT. The 3 mol % of quaternary ammonium groups facilitated exfoliation of MMT. The 1 wt % MMT/PCL‐PUC nanocomposites showed enhanced tensile properties relative to the pure PCL‐PU. As the MMT content increased in the MMT/PCL‐PUC nanocomposites, the degree of microphase separation of PCL‐PUC decreased because of the strong interactions between the PCL‐PUC chains and the exfoliated MMT layers. This resulted in an increase in the Young's modulus and a decrease in the elongation at break and maximum stress of the MMT/PCL‐PUC nanocomposites. Biodegradability of the MMT/PCL‐PUC nanocomposites was dramatically increased with increasing content of MMT, likely because of the less phase‐separated morphology of MMT/PCL‐PUC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and dielectric properties of poly(ε‐caprolactone) compounded with “bucky gels”‐like mixture

Poly(ε‐caprolactone) (PCL) was melt compounded with “Bucky gels”‐like mixture that prepared by grinding multiwalled carbon nanotubes (MWNTs) and ionic liquids (ILs). Raman spectrum showed the significant interaction between ILs and MWNTs. The dielectric behavior of PCL nanocomposites based on unmodified and IL‐modified MWNTs was studied from 40 Hz to 30 MHz. The addition of ILs significantly enhanced the dielectric property of PCL/IL/MWNT ternary nanocomposites, which was much higher than that of the sum of PCL/IL with PCL/MWNT binary nanocomposites. The dielectric properties of PCL/IL/MWNT nanocomposites were mainly influenced by ILs in low frequency and were dominated by MWNTs in high frequency. SEM results revealed that a more uniform and fine dispersion of MWNTs were achieved throughout the PCL matrix because of ILs. The addition of ILs in nanocomposites changed the crystallinity of PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40231.     

Crystallization behavior of poly(p‐dioxanone)‐PU/montmorillonite nanocomposites prepared by chain‐extending reaction

Organo‐modified montmorillonites and poly(p‐dioxanone) (PPDO) diol prepolymers were used to prepare Poly(p‐dioxanone)‐PU/organic montmorillonite (PPDO‐PU/OMMT) nanocomposites by chain‐extending reaction. The crystallization behavior and spherulitic morphology of PPDO‐PU/OMMT nanocomposites were investigated by WXRD, differential scanning calorimetry, and polarized optical microscopy. The results show that the regularity of the chain structure plays a dominant role during the crystallization process rather than that of OMMT content and its dispersion status in PPDO matrix. With similar molecular weight and same OMMT content, PPDO‐PU/OMMT nanocomposite, which derived from lower molecular weight PPDO prepolymer, exhibits lower crystallization rate, melting point, and crystallinity. The influence of the clay content on the crystallization behavior highly depends on its dispersing state. The nucleating effect of OMMT can be only observed at high loading percentage. For the nanocomposites with low clay loading percentage, the retarding effect of exfoliated platelets on the chain‐ordering into crystal lamellae became the key factor. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal and mechanical properties of poly(ε‐caprolactone)/polyhedral oligomeric silsesquioxane nanocomposites

Poly(ε‐caprolactone) (PCL)/trisilanolphenyl polyhedral oligomeric silsesquioxane (TspPOSS) nanocomposites were prepared by solution mixing followed by film casting. Wide‐angle X‐ray diffraction and field‐emission scanning electron microscopy observations showed that the POSS molecules formed crystal domains and dispersed uniformly on the nanoscale in the PCL matrix. Fourier transform infrared analysis of the nanocomposites revealed that there are hydrogen‐bonded interactions between the silanol group of the TspPOSS and carbonyl oxygen of the PCL. Differential scanning calorimetry, tensile testing, and dynamic mechanical analysis (DMA) showed that, with increasing POSS content in the nanocomposites, the melting temperature and degree of crystallinity decreased while glass transition temperature, tensile modulus and strength increased without sacrificing the ductility of the PCL. DMA results also demonstrated the presence of a rubbery plateau above the melting temperature of the PCL/TspPOSS nanocomposites, and the moduli at the plateau region increased with increasing POSS content in the nanocomposites, implying that the PCL/TspPOSS nanocomposites formed a physically crosslinked structure. The physically crosslinked PCL/TspPOSS nanocomposites exhibited a thermally triggered shape memory effect. Copyright © 2012 Society of Chemical Industry     

Nonisothermal crystallization behavior of poly(ϵ‐caprolactone)/attapulgite nanocomposites by DSC analysis

Nanocomposites based on biodegradable poly(ε‐caprolactone) (PCL) and attapulgite (AT) were prepared by solution mixing. The nonisothermal crystallization of the pure PCL and PCL/AT nanocomposites at different AT contents and different cooling rates were investigated by differential scanning calorimetry (DSC). There are significant dependence of nonisothermal crystallization behavior and kinetics of PCL/AT nanocomposites on the AT content and cooling rate. The Jeziorny method has been employed to analyze the DSC data. The results show that Jeziorny method could describe this system well. It can be concluded that AT can be used as an effective nucleating agent and has effects on the growth of crystallites in the crystallization process of PCL matrix. POLYM. ENG. SCI., 47:460–466, 2007. © 2007 Society of Plastics Engineers.     

Preparation and properties of TiO2‐filled poly(acrylonitrile‐butadiene‐styrene)/epoxy hybrid composites

Poly (acrylonitrile‐butadiene‐styrene) (ABS) was used to modify diglycidyl ether of bisphenol‐A type of epoxy resin, and the modified epoxy resin was used as the matrix for making TiO₂ reinforced nanocomposites and were cured with diaminodiphenyl sulfone for superior mechanical and thermal properties. The hybrid nanocomposites were characterized by using thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), universal testing machine (UTM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The bulk morphology was carefully analyzed by SEM and TEM and was supported by other techniques. DMA studies revealed that the DDS‐cured epoxy/ABS/TiO₂ hybrid composites systems have two T_gs corresponding to epoxy and ABS rich phases and have better load bearing capacity with the addition of TiO₂ particles. The addition of TiO₂ induces a significant increase in tensile properties, impact strength, and fracture toughness with respect to neat blend matrix. Tensile toughness reveals a twofold increase with the addition of 0.7 wt % TiO₂ filler in the blend matrix with respect to neat blend. SEM micrographs of fractured surfaces establish a synergetic effect of both ABS and TiO₂ components in the epoxy matrix. The phenomenon such us cavitation, crack path deflection, crack pinning, ductile tearing of the thermoplastic, and local plastic deformation of the matrix with some minor agglomerates of TiO₂ are observed. However, between these agglomerates, the particles are separated well and are distributed homogeneously within the polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallization kinetics of thermosetting polymer blends of poly(ε‐caprolactone) and unsaturated polyester resin

A study has been made of the isothermal crystallization kinetics of poly(ε‐caprolactone) (PCL) in partially miscible crosslinked polyester resin (PER)/PCL blends by using differential scanning calorimetry (DSC). For comparison, miscible blends of PCL with uncured polyester resin, i.e., oligoester resin (OER), were also investigated. The overall crystallization rate of PCL remarkably decreased with the addition of amorphous component, OER or PER. The kinetic rate constant K_n decreased sharply for both the OER/PCL blends and the crosslinked PER/PCL blends with decreasing PCL concentration. The mechanism of nucleation and geometry of the growing PCL crystals was not remarkably affected by the incorporation of OER, but changed considerably with the addition of PER. However, the overall crystallization rate of PCL in the crosslinked PER/PCL blends was much higher compared with the corresponding uncured OER/PCL blends, which is attributable to the phase‐separated structure and the reduced miscibility in the crosslinked blends. According to the nucleation and growth theories, the nucleation process was considered to be the rate controlling step in the crystallization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 322–327, 1999     

Reaction‐induced phase separation and resulting thermomechanical and surface properties of epoxy resin/poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) blends cured with 4,4′‐diaminodiphenylsulfone

We investigated the phase separation, cure kinetics and thermomechanical properties of diglycidyl ether of bisphenol‐A/4,4′‐diaminodiphenylsulfone/poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer (TBCP) blends. Fourier transform infrared spectroscopy, differential scanning calorimetry, and atomic force microscopy revealed that the blends exhibited heterogeneous phase morphology in which the TBCP formed dispersed domains in epoxy matrix, due to reaction induced phase separation. A fraction of phase‐separated PEO phase underwent partial crystallization whereas another fraction formed interphases between the dispersed domains and epoxy matrix. Moreover, the dispersed PEO chains improved the compatibility and interfacial adhesion between the matrix and domains and, consequently, significantly improved the mechanical properties of epoxy resin. Furthermore, the thermal degradation studies and contact angle measurements disclosed that the dispersed domains were well protected by the epoxy matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44406.     

Crystallization behavior of poly(ϵ‐caprolactone)/Tio2 nanocomposites obtained by in situ polymerization

Poly(?‐caprolactone) (PCL)/titanium dioxide (TiO₂) nanocomposites were prepared by in situ polymerization of ?‐caprolactone in the presence of modified‐TiO₂ nanoparticles as initiators. The molecular weight of PCL matrix was dependent on the amount of the TiO₂ fillers. The incorporation of TiO₂ did not significantly affect the crystalline structure of PCL. Moreover, a tendency of the nanoparticles to form aggregates was observed, especially at higher fillers contents. The analysis of the crystallization process showed that the addition of TiO₂ nanoparticles accelerated the crystallization rate of PCL, and the crystallization rates increased by increasing the filler content. The crystallization activation energy dependence on the filler content observed here is probably the consequence of the two competing factors. The tendency of activation energy obtained by nonisothermal crystallization is similar to that of isothermal crystallization. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Crystallization behavior of poly(ε‐caprolactone)/layered double hydroxide nanocomposites

Poly(?‐caprolactone) (PCL)/layered double hydroxide (LDH) nanocomposites were prepared successfully via simple solution intercalation. The nonisothermal melt crystallization kinetics of neat PCL and its LDH nanocomposites was investigated with the Ozawa, Avrami, and combined Avrami–Ozawa methods. The Ozawa method failed to describe the crystallization kinetics of the studied systems. The Avrami method was found to be useful for describing the nonisothermal crystallization behavior, but the parameters in this method do not have explicit meaning for nonisothermal crystallization. The combined Avrami–Ozawa method explained the nonisothermal crystallization behavior of PCL and its LDH nanocomposites effectively. The kinetic results and polarized optical microscopy observations indicated that the addition of LDH could affect the mechanism of nucleation and growth of the PCL matrix. The Takhor model was used to analyze the activation energies of nonisothermal crystallization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Transesterification in homogeneous poly(ε‐caprolactone)–epoxy blends

Transesterification has been investigated in poly(ε‐caprolactone) (PCL)–epoxy blends. In the hot melt process, the hydroxyl on diglycidyl ether of bisphenol‐A (DGEBA) monomers is too low to give a noticeable transesterification reaction. In the postcure process, model reactions reveal that the hydroxyls from a ring‐opening reaction are able to react with the esters of PCL. In the meantime, the PCL molecular weight decrease and its distribution becomes broader. Nuclear magnetic resonance spectra reveal that fraction of the tertiary hydroxyls converts to secondary hydroxyls. In the cured DGEBA–3,3′‐dimethylmethylene‐di(cyclohexylamine)–PCL blend, a homogeneous morphology is achieved. PCL segments are grafted onto the epoxy network after postcuring and result in the lower T_g observed in the differential scanning calorimetry thermogram. A higher transesterification extent also results in broader transition peaks by dynamic mechanical analysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 75–82, 1999     

Comparison of crystallization behaviors of poly(ε‐caprolactone) in confined environment with that in bulk

The spatial confinement of poly(ε‐caprolactone) (PCL) in the matrix of PMMA was synthesized by insitu polymerization and characterized by WAXD and SEM. The nonisothermal crystallization behavior and the kinetics of PCL in PMMA/PCL (85/15) blend and pure PCL were investigated by means of DSC. Jeziorny and Ozawa's theoretical prediction methods were used to analyze the crystallization kinetics. The melting behavior after cooling was also studied. There was an additional interesting phenomenon of double‐melting peak for pure PCL. Peaks at lower temperature shifted to lower temperature, and peaks at higher temperature did not shift with the increasing cooling rate. This behavior can be due to recrystallization. For the high‐crystallization activity energy and low‐crystallization rate, PCL in bulk would recrystallize during the melting process, and displayed a double‐melting behavior. Under spatial confinement of the rigid PMMA, PCL had much lower crystallization activity energy and had only one melting peak. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Confined crystallization morphology of poly(ϵ‐caprolactone) block within poly(ϵ‐caprolactone)–poly(l‐lactide) copolymers

The confined crystallization of poly(?‐caprolactone) (PCL) block in poly(?‐caprolactone)–poly(l ‐lactide) (PCL‐PLLA) copolymers was investigated using differential scanning calorimetry, polarized optical microscopy, scanning electronic microscopy and atomic force microscopy. To study the effect of crystallization and molecular chain motion state of PLLA blocks in PCL‐PLLA copolymers on PCL crystallization morphology, high‐temperature annealing (180 °C) and low‐temperature annealing (80 °C) were applied to treat the samples. It was found that the crystallization morphology of PCL block in PCL‐PLLA copolymers is not only related to the ratio of block components, but also related to the thermal history. After annealing PCL‐PLLA copolymers at 180 °C, the molten PCL blocks are rejected from the front of PLLA crystal growth into the amorphous regions, which will lead to PCL and PLLA blocks exhibiting obvious fractionated crystallization and forming various morphologies depending on the length of PLLA segment. On the contrary, PCL blocks more easily form banded spherulites after PCL‐PLLA copolymers are annealed at 80 °C because the preexisting PLLA crystal template and the dangling amorphous PLLA chains on PCL segments more easily cause unequal stresses at opposite fold surfaces of PCL lamellae during the growth process. Also, it was found that the growth rate of banded spherulites is less than that of classical spherulites and the growth rate of banded spherulites decreases with decreasing band spacing. © 2019 Society of Chemical Industry