Crystallization Rate Of PCL Research Articles

Effect of liquid plasticizers on crystallization of PCL in soft PVC/PCL/plasticizer blends

ABSTRACTIn this work, poly(ε‐caprolactone) (PCL) and liquid plasticizer were combined used to plasticize poly(vinyl chloride) (PVC), and the possibility of using PVC/PCL/plasticizer blends to fabricate soft PVC with enhanced migration resistance was investigated. Through partial replacement of liquid plasticizers in soft PVC by equal quantity of PCL, flexibility was maintained while extraction loss of plasticizer by organic solvent was reduced significantly. Furthermore, crystallization of PCL in PVC/PCL/plasticizer blends with low PCL content was observed, and crystallization rate of PCL was found to be influenced by plasticizer contents and structures. For instance, crystallization rate of PCL in PVC/PCL/diisononyl phthalate (DINP) (100/40/100) was 3.7 times faster than in PVC/PCL/DINP (100/40/80), while crystallization rate of PCL in PVC/PCL/dioctyl adipate(DOA)(100/40/100) was 8.3 times faster than in PVC/PCL/diisononyl cyclohexane‐1,2‐dicarboxylate (DINCH) (100/40/100). Low‐field 1H NMR test manifested that different crystallization rate of PCL in PVC/PCL/plasticizer blends with different plasticizer structures was triggered by difference in plasticizers' compatibility with PVC, that is, the number of interaction point between PVC and plasticizers. It is concluded that PCL crystallization favored by liquid plasticizers in PVC/PCL/plasticizer blends was induced by interaction competition between PVC/plasticizer and PVC/PCL. As plasticizer content increases or its compatibility with PVC decreases, interaction competition becomes more intense and consequently faster crystallization of PCL occurs. Thus, to obtain soft PVC products with improve migration resistance while avoiding PCL crystallization, the total content of plasticizer (including both liquid plasticizer and PCL) should be lower than 66 phr (40 wt %). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48803.

Crystallization Behavior of Poly(sodium 4-styrenesulfonate)-Functionalized Carbon Nanotubes Filled Poly(ε-caprolactone) Nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were modified with a noncovalent functionalization method via ultrasonication in the presence of poly(sodium 4-styrenesulfonate) (PSS) as a modifier. The PSS-functionalized MWCNTs dispersed well in PCL matrix and showed good interfacial adhesion with PCL after being incorporated by solution coagulation. The isothermal crystallization kinetics of neat PCL and PCL/MWCNT nanocomposites were comparatively investigated by DSC. It was found that the overall crystallization rate of PCL was enhanced significantly, while the crystallization mechanism was unchanged by incorporation of the functionalized MWCNTs. The addition of only 0.1 wt % MWCNT caused 23.4 times improvement in overall crystallization rates, ascribing to the efficient nucleating effect of well-dispersed PSS-functionalized MWCNTs toward crystallization of PCL in the nanocomposites. The spherulitic morphology observation by polarizing optical microscope confirmed the nucleating effect. X-ray diffraction investig...

Effect of electron beam irradiation on the crystallization of silk fibroin fiber‐reinforced poly(ε‐caprolactone) biocomposites

AbstractIn the medical industry, ionizing radiation has attracted increasing interest in recent years for the sterilization of biomedical materials due to its high effectiveness at relatively low cost and simple operation. In the study reported here, silk fibroin (SF) fiber was used to prepare novel reinforced poly(ε‐caprolactone) (PCL) biocomposites, and the effect of electron beam irradiation on both non‐isothermal and isothermal crystallization kinetics of the SF/PCL biocomposites was investigated. The models of Ozawa treatment, Avrami analysis and regime theory of crystal growth are applicable for describing the non‐isothermal and isothermal crystallization kinetics of the irradiated PCL and SF/PCL composites. Compared with non‐irradiated PCL and SF/PCL composites, the irradiated specimens exhibit the same crystallization regime (regime II) and similar lateral surface free energy (σ), except for smaller fold surface free energy (σe) and work of chain folding (q). The crosslinked PCL network formed in the irradiation process can act as a nucleation agent and accelerate the primary crystallization of PCL. However, the restriction effect of the crosslinked PCL network on the molecular chain mobility will reduce the overall crystallization rate of PCL, and this restriction effect appears stronger in the non‐isothermal crystallization process than in the isothermal crystallization process. Copyright © 2009 Society of Chemical Industry

Isothermal crystallization kinetics of silk fibroin fiber‐reinforced poly(ε‐caprolactone) biocomposites

AbstractBACKGROUND: Poly(ε‐caprolactone) (PCL) has attracted great attention due to its wide applications for pharmaceutical controlled released systems and implanted polymer devices. In this study, silk fibroin fiber (SF) obtained from degumming treatment of silk was used to prepare novel reinforced PCL biocomposites. The isothermal crystallization behavior of these composites was investigated using differential scanning calorimetry measurements.RESULTS: With a decrease of isothermal crystallization temperature (Tc) and an increase of fiber filler, the crystallization time of the SF/PCL composites becomes shorter, the crystallization rate constant (K) increases and the Avrami exponent (n) gradually decreases (being between 1 and 2). The crystallization of PCL and SF/PCL composites occurs in the same regime. With the gradual addition of fiber, lateral surface free energy (σ) is nearly unchanged, but fold surface free energy (σe) decreases.CONCLUSION: Heterogeneous nucleation is dominant and different growth morphologies coexist during the isothermal crystallization process of the SF/PCL hybrid systems. Although the introduction of SF obviously increases the overall crystallization rate of PCL, the growth rate constant and nucleation constant of PCL are reduced because of the confinement effect of fiber network structures on the molecular mobility of polymer molecular chains. Copyright © 2009 Society of Chemical Industry

Synthesis and characterization of well‐defined polystyrene and poly(ε‐caprolactone) hetero eight‐shaped copolymers

AbstractWell‐defined hetero eight‐shaped copolymers composed of polystyrene (PS) and poly(ε‐caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution were successfully synthesized by the combination of ring‐opening polymerization, ATRP, and “click” reaction. The synthetic procedure involves three steps: (1) preparation of a tetrafunctional PS and PCL star copolymer with two PS and two PCL arms using the tetrafunctional initiator bearing two hydroxyl groups and two bromo groups; (2) synthesis of tetrafunctional star copolymer, (α‐acetylene‐PCL)2(ω‐azido‐PS)2, by the transition of terminal hydroxyl and bromo groups to acetylene and azido groups through the reaction with 4‐propargyloxybutanedioyl chloride and NaN3 respectively; (3) intramolecular cyclization reaction to produce the hetero eight‐shaped copolymers using “click” chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resulted intermediates and the target polymers. Their thermal behavior was investigated by DSC, and their crystallization behaviors of PCL were studied by polarized optical microscopy. The decrease in chain mobility of the eight‐shaped copolymers restricts the crystallization of PCL and the crystallization rate of PCL is slower in comparison with their corresponding star precursors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6496–6508, 2008

Fullerene End‐Capped Biodegradable Poly(ε‐caprolactone)

AbstractFullerene capped poly(ε‐caprolactone)s (PCLs), namely single‐ and double‐fullerene end‐capped PCLs with different fullerene content, were successfully synthesized. The effect of the fullerene end on the crystallization behavior and mechanical properties of the PCL was studied. The aggregation behavior of the fullerene moieties at the end of the PCL chain was also studied. It was found that the aggregated fullerenes have two kinds of effect on the crystallization behavior of the PCL i.e., confinement effect and nucleating effect. The fullerene content shows a certain balance between the confinement effect and the nucleating effect on the crystallization rate of PCL. It was also found that the mechanical properties of the fullerene end‐capped PCLs are strongly related to the content of fullerene and the mode of end‐capping style: either single or double end‐capping.magnified image

Crystallization and Melting Behavior of Poly(ε-caprolactone) under Physical Confinement

The crystallization and melting behavior of poly(e-caprolactone) (PCL) in a physically confined system, self-assembly blends of poly(e-caprolactone)/polystyrene-b-poly(ethylenepropylene) (PCL/PS−PEP), were studied by differential scanning calorimetry (DSC). The glassy PS-rich phases effectively confine the PCL crystallization due to the localization behavior of PCL where the PCL component appears to be localized in between the lamellae-like microdomains of PS block. Macrophase-separated and microphase-separated morphology were both identified in the self-assembly blends. The crystallization rate of PCL is strongly affected by the phase-separated morphology. The effective confinement on crystallization occurs while the size of lamellae-like confinement goes below submicrometer. Under effective confinement, the crystalline chains of PCL appear in random orientation at low crystallization temperature and in parallel orientation at high crystallization temperature as evidenced by simultaneous small-angle X-ra...

Polymer-layered silicate nanocomposites based on poly(ε-caprolactone)

Poly(ε-caprolactone) nanocomposites based on montmorillonite modified with hexadecyltrimethylammonium bromide (M-HTAB) were prepared by the in situ polymerization technique. As a result, nano-structured PCL/M-HTAB systems were obtained. It was found that the molecular weight of PCL decreased with an increase in silicate content in the system. Within the investigated range of molecular weight, crystallization behavior of poly(ε-caprolactone) was affected only by the presence of M-HTAB. A silicate loading of higher than 10 wt.% reduced both crystallinity degree and the crystallization rate of PCL. The structure of obtained intercalated nanocomposites depended on the amount of montmorillonite in the systems. The periodicity of clay layers, estimated by X-ray diffraction, was found to be high at increased silicate loading in the nanocomposite. Since PCL and SAN are miscible, an attempt was made to use PCL/M-HTAB systems as a modifier for SAN matrix. Apparently, a quantity as small as 0.66 wt.% of M-HTAB in such blends induced a clear increase in material stiffness. An increase of Young's modulus of more than 40% in comparison to neat SAN was observed at 5.65 wt.% silicate loading.

The Comparison of the Ringed Spherulite Morphology of PCL Blends with Poly(vinyl chloride), Poly(bisphenol A carbonate) and Poly(hydroxyether of bisphenol A)

The crystallization and ringed spherulite morphology of poly(ε-caprolactone) (PCL) in the miscible blends of PCL/poly(vinyl chloride) (PVC), PCL/poly(hydroxyether of bisphenol A) (phenoxy resin) and PCL/poly(bisphenol A carbonate) (PC) were investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Through the comparison of the PCL crystalline morphology with the interaction energy density B between the miscible components in these blends, it was found that the addition of the non-crystallizable component had great effect on the regularity of the ringed spherulite, which was coincided with the change of the interaction energy density B. To grow regular ringed spherulites in the PCL miscible blends, it was most important that the crystallization rate of PCL in the blends must be matched with the diffusion rate of the non-crystallizable component. Such a matching relation in the process of the ringed spherulite growth was a most important condition for the regular twisting of PCL lamellae.

The Comparison of the Ringed Spherulite Morphology of PCL Blends with Poly(vinyl chloride), Poly(bisphenol A carbonate) and Poly(hydroxyether of bisphenol A)

The crystallization and ringed spherulite morphology of poly(e-caprolactone) (PCL) in the miscible blends of PCL/poly(vinyl chloride) (PVC), PCL/poly(hydroxyether of bisphenol A) (phenoxy resin) and PCL/poly(bisphenol A carbonate) (PC) were investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Through the comparison of the PCL crystalline morphology with the interaction energy density B between the miscible components in these blends, it was found that the addition of the non-crystallizable component had great effect on the regularity of the ringed spherulite, which was coincided with the change of the interaction energy density B. To grow regular ringed spherulites in the PCL miscible blends, it was most important that the crystallization rate of PCL in the blends must be matched with the diffusion rate of the non-crystallizable component. Such a matching relation in the process of the ringed spherulite growth was a most important condition for the regular twisting of PCL lamellae.

Miscible Blends of Polystyrene and Poly(ε-caprolactone) with Phenylacetylene-Carbon Monoxide Alternating Copolymer

The alternating copolymer of phenylacetylene (PA) and carbon monoxide (CO) (poly(PA-alt-CO)) synthesized by palladium complex has been blended with polystyrene (PS) and poly(ε-caprolactone) (PCL). The miscibility of the blends was investigated by differential scanning calorimetry (DSC). A single Tg was observed over the entire composition range for both blending systems, indicating that PS and PCL were miscible with poly(PA-alt-CO). The effect of blending with poly(PA-alt-CO) on the crystallization behavior of PCL was also studied. Both the degree of crystallinity and the crystallization rate of PCL were found to be depressed with the presence of copolymer. Blending with poly(PA-alt-CO) also exerted a strong effect on the melting behavior of PCL. The recrystallization of PCL in the melting region was hindered by poly(PA-alt-CO).

A DSC study on miscible blends containing two crystalline components: poly(ε‐caprolactone)/poly[3,3‐bis(chloromethyl)oxetane

AbstractBlends of poly(ε‐caprolactone) (PCL) with poly[3,3‐bis(chloromethyl)oxetanel] (Penton) were prepared by casting from a common solvent. All blends show a single, composition‐dependent glass transition temperature (Tg), indicating that the blends are miscible in the amorphous state and in the melt. The crystallization rate of PCL in the blend decreases with increasing Penton content, that of Penton decreases with increasing PCL content. The crystallinity index of PCL in the blend decreases with increasing Penton content owing to the enhanced Tg of the system, whereas that of Penton does not depend on composition. The interaction parameter B of the two polymers in the melt was found to be −15 J/cm3.