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2015 Volume 33 Issue 3
2015, 33(3): 371-375
doi: 10.1007/s10118-015-1589-z
Abstract:
A novel method for preparing conductive polyethylene (PE) composites has been developed. In the method, the powder of low melting point metal alloy (LMPA) is filled into the PE matrix by using twin screw extruder at a temperature below the melting point of the LMPA, and followed by a die drawing process at a temperature around the melting point of the metal alloy. It has been found that die drawing process, repeating the die drawing process and adding nano-fillers, such as montmorillonite (MMT) and multi-wall carbon nanotubes (MWCNTs), all help reduce the metal particle size in the PE matrix, thus improve the conductivity of the composite. The conductivity improvement is attributed to an increased number of the smaller metal particles. Therefore, conductive composites of polymer/metal alloy/nano-filler with high conductivity are possible to be prepared by using the new method.
A novel method for preparing conductive polyethylene (PE) composites has been developed. In the method, the powder of low melting point metal alloy (LMPA) is filled into the PE matrix by using twin screw extruder at a temperature below the melting point of the LMPA, and followed by a die drawing process at a temperature around the melting point of the metal alloy. It has been found that die drawing process, repeating the die drawing process and adding nano-fillers, such as montmorillonite (MMT) and multi-wall carbon nanotubes (MWCNTs), all help reduce the metal particle size in the PE matrix, thus improve the conductivity of the composite. The conductivity improvement is attributed to an increased number of the smaller metal particles. Therefore, conductive composites of polymer/metal alloy/nano-filler with high conductivity are possible to be prepared by using the new method.
2015, 33(3): 376-385
doi: 10.1007/s10118-015-1591-5
Abstract:
Multi-walled carbon nanotubes (MWCNTs) were grafted with poly(N-vinyl-2-pyrrolidone) and with poly(2-acrylamido-2-methyl-1-propanesulfonic acid) at different compositions by using g-rays technique as initiator. The MWCNTs, MWCNT-graft-PNVP, MWCNT-graft-PAMPS and MWCNTs-graft-P(NVP-co-AMPS) were characterized by Fourier transform infra red (FTIR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), elemental analysis and high-resolution transmission electron microscopy (HR-TEM). The results indicated that the grafting processes of PNVP, PAMPS and P(NVP-co-AMPS) occurred on to the surfaces of MWCNTs without destroying the framework of MWCNTs. Tramadol hydrochloride (TH) was loaded as model drug and its release behavior was analyzed via various kinetic models. Release of the loaded TH was studied in simulated gastric fluid (SGF, pH = 1.2) and simulated intestinal fluid (SIF, pH = 7.4) at 37 ℃. Controlled release of TH from grafted MWCNTs was investigated. The outcome results suggest that the grafted MWCNTs could be used as a promising matrix candidate for oral drug delivery system by harmonization between the composition and pH level of the simulated biological fluids.
Multi-walled carbon nanotubes (MWCNTs) were grafted with poly(N-vinyl-2-pyrrolidone) and with poly(2-acrylamido-2-methyl-1-propanesulfonic acid) at different compositions by using g-rays technique as initiator. The MWCNTs, MWCNT-graft-PNVP, MWCNT-graft-PAMPS and MWCNTs-graft-P(NVP-co-AMPS) were characterized by Fourier transform infra red (FTIR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), elemental analysis and high-resolution transmission electron microscopy (HR-TEM). The results indicated that the grafting processes of PNVP, PAMPS and P(NVP-co-AMPS) occurred on to the surfaces of MWCNTs without destroying the framework of MWCNTs. Tramadol hydrochloride (TH) was loaded as model drug and its release behavior was analyzed via various kinetic models. Release of the loaded TH was studied in simulated gastric fluid (SGF, pH = 1.2) and simulated intestinal fluid (SIF, pH = 7.4) at 37 ℃. Controlled release of TH from grafted MWCNTs was investigated. The outcome results suggest that the grafted MWCNTs could be used as a promising matrix candidate for oral drug delivery system by harmonization between the composition and pH level of the simulated biological fluids.
2015, 33(3): 386-394
doi: 10.1007/s10118-015-1592-4
Abstract:
Phase structure and crystallization behavior of polyethylene (PE) in its blends with cis-1,4-butadiene rubber (BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 ℃, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 ℃, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.
Phase structure and crystallization behavior of polyethylene (PE) in its blends with cis-1,4-butadiene rubber (BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 ℃, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 ℃, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.
2015, 33(3): 395-403
doi: 10.1007/s10118-015-1594-2
Abstract:
According to the vulcanization kinetic equation of natural rubber (NR) established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructed by means of incremental method. The description of non-isothermal in-mold vulcanization process is carried out by the finite element method. The mold-opening time, the rubber and mold temperatures, the degree of rubber cure and its distribution characteristics are numerically analyzed, by changing the key formulas and parameters in the process including the temperature of curing medium, the concentration of 2-mercaptobenzothiazole, the heat transfer manner of mold side, and the convective heat transfer coefficient of heating boundary. The quantitative results will help engineers to design proper formulas and optimize processing conditions.
According to the vulcanization kinetic equation of natural rubber (NR) established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructed by means of incremental method. The description of non-isothermal in-mold vulcanization process is carried out by the finite element method. The mold-opening time, the rubber and mold temperatures, the degree of rubber cure and its distribution characteristics are numerically analyzed, by changing the key formulas and parameters in the process including the temperature of curing medium, the concentration of 2-mercaptobenzothiazole, the heat transfer manner of mold side, and the convective heat transfer coefficient of heating boundary. The quantitative results will help engineers to design proper formulas and optimize processing conditions.
2015, 33(3): 404-415
doi: 10.1007/s10118-015-1590-6
Abstract:
A general protocol was described for fabricating uniform molecularly imprinted polymer (MIP) particles via controlled living radical precipitation polymerization at ambient temperature. By adopting glutathione as model template, benzyl dithiocarbamate as iniferter agent, 4-vinylpyridine as monomer, and ethylene glycol dimethacrylate as cross-linker, it is demonstrated that the polymerization parameters including the iniferter concentration, monomer loading and molar ratio of cross-linker to functional monomer have profound effect on the final particle size and recognition property of the MIP particles. The batch static binding experiments were carried out to estimate the adsorption kinetics, adsorption isotherms and selective recognition of the MIP particles. The adsorption behavior followed the pseudo-second order kinetic model, revealing that the process was chemically carried out. Two adsorption isotherm models were applied to analyze equilibrium data, obtaining the best description by Langmuir isotherm model. In addition, the MIP particles also could selectively recognize glutathione over similar analogs, indicating the possibility for the separation and enrichment of the template from complicated matrices.
A general protocol was described for fabricating uniform molecularly imprinted polymer (MIP) particles via controlled living radical precipitation polymerization at ambient temperature. By adopting glutathione as model template, benzyl dithiocarbamate as iniferter agent, 4-vinylpyridine as monomer, and ethylene glycol dimethacrylate as cross-linker, it is demonstrated that the polymerization parameters including the iniferter concentration, monomer loading and molar ratio of cross-linker to functional monomer have profound effect on the final particle size and recognition property of the MIP particles. The batch static binding experiments were carried out to estimate the adsorption kinetics, adsorption isotherms and selective recognition of the MIP particles. The adsorption behavior followed the pseudo-second order kinetic model, revealing that the process was chemically carried out. Two adsorption isotherm models were applied to analyze equilibrium data, obtaining the best description by Langmuir isotherm model. In addition, the MIP particles also could selectively recognize glutathione over similar analogs, indicating the possibility for the separation and enrichment of the template from complicated matrices.
2015, 33(3): 416-421
doi: 10.1007/s10118-015-1593-3
Abstract:
A facile and general route to a new generation of polyaniline (PANI)-citric acid (CA) crystals such as 2D nanoplates, 2D nanosheets and 3D microrods self-assembled by the - stacking interaction is reported. Dramatic, 3D rectangular shaped microrods and 2D nanosheets are single crystals indicated by SAED patterns and HRTEM images. Moreover, the method does not depend on any specific equipment or heating, cooling and complex procedures. The novel polyaniline crystals will be useful for next generation organic electronics such as nano-transistors.
A facile and general route to a new generation of polyaniline (PANI)-citric acid (CA) crystals such as 2D nanoplates, 2D nanosheets and 3D microrods self-assembled by the - stacking interaction is reported. Dramatic, 3D rectangular shaped microrods and 2D nanosheets are single crystals indicated by SAED patterns and HRTEM images. Moreover, the method does not depend on any specific equipment or heating, cooling and complex procedures. The novel polyaniline crystals will be useful for next generation organic electronics such as nano-transistors.
2015, 33(3): 422-432
doi: 10.1007/s10118-015-1595-1
Abstract:
Narrow-disperse, surface-functionalized living polymer microspheres with uniformly cross-linked structures were prepared by two-stage precipitation copolymerization of styrene and divinylbenzene. The two-stage precipitation polymerization is composed of an initial conventional precipitation polymerization for the nucleation followed by a reverse atom transfer radical polymerization (reverse ATRP) for the controlled polymerization process. The polymerization parameters (including reaction time for the first stage, AIBN amount and monomer loading) have been studied to show significant influences on the morphologies. Moreover, narrower size distribution and an ATRP initiator-functional surface of resulting particles can be obtained by applying reverse ATRP to conventional precipitation polymerization in the second stage. Furthermore, the livingness of the resulting polymer microspheres was testified by their surface modification of poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) brushes via surface-initiated ATRP (SI-ATRP).
Narrow-disperse, surface-functionalized living polymer microspheres with uniformly cross-linked structures were prepared by two-stage precipitation copolymerization of styrene and divinylbenzene. The two-stage precipitation polymerization is composed of an initial conventional precipitation polymerization for the nucleation followed by a reverse atom transfer radical polymerization (reverse ATRP) for the controlled polymerization process. The polymerization parameters (including reaction time for the first stage, AIBN amount and monomer loading) have been studied to show significant influences on the morphologies. Moreover, narrower size distribution and an ATRP initiator-functional surface of resulting particles can be obtained by applying reverse ATRP to conventional precipitation polymerization in the second stage. Furthermore, the livingness of the resulting polymer microspheres was testified by their surface modification of poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) brushes via surface-initiated ATRP (SI-ATRP).
2015, 33(3): 433-443
doi: 10.1007/s10118-015-1596-0
Abstract:
The sliding graft copolymer (SGC), in which many linear poly-e-caprolactone (PCL) side chains are bound to cyclodextrin rings of a polyrotaxane (PR), was prepared and employed to toughen diglycidyl ether of bisphenol A (DGEBA) based epoxy resin. The aim of the work is to understand the effect of SGC on the miscibility, morphology, thermal behavior, curing reaction and mechanical performance of the cured systems. From differential scanning calorimetry (DSC) analysis and dynamic mechanical thermal analysis (DMTA) of DGEBA/SGC thermosetting blends, it is found that DGEBA and SGC are miscible in the amorphous state. Fourier transform infrared spectroscopy (FTIR) suggested that the miscibility between SGC and DGEBA is due to the existence of intermolecular specific interactions (viz. hydrogen bonding). The impact strength is improved by 4 times for DGEBA/SGC (80/20) blends compared with that of the unmodified system. The increase in toughness of SGC-modified thermosets can be explained by the effect of intermolecular specific interactions of SGC with DGEBA, which is beneficial to induce the plastic deformation of matrix. This is the first report on utilizing this novel supramolecular polymer to toughen rigid epoxy matrix.
The sliding graft copolymer (SGC), in which many linear poly-e-caprolactone (PCL) side chains are bound to cyclodextrin rings of a polyrotaxane (PR), was prepared and employed to toughen diglycidyl ether of bisphenol A (DGEBA) based epoxy resin. The aim of the work is to understand the effect of SGC on the miscibility, morphology, thermal behavior, curing reaction and mechanical performance of the cured systems. From differential scanning calorimetry (DSC) analysis and dynamic mechanical thermal analysis (DMTA) of DGEBA/SGC thermosetting blends, it is found that DGEBA and SGC are miscible in the amorphous state. Fourier transform infrared spectroscopy (FTIR) suggested that the miscibility between SGC and DGEBA is due to the existence of intermolecular specific interactions (viz. hydrogen bonding). The impact strength is improved by 4 times for DGEBA/SGC (80/20) blends compared with that of the unmodified system. The increase in toughness of SGC-modified thermosets can be explained by the effect of intermolecular specific interactions of SGC with DGEBA, which is beneficial to induce the plastic deformation of matrix. This is the first report on utilizing this novel supramolecular polymer to toughen rigid epoxy matrix.
2015, 33(3): 444-455
doi: 10.1007/s10118-015-1597-z
Abstract:
Poly(propylene carbonate) (PPC) was melt blended in a batch mixer with poly(butylene carbonate) (PBC) in an effort to improve the toughness of the PPC without compromising its biodegradability and biocompatibility. DMA results showed that the PPC/PBC blends were an immiscible two-phase system. With the increase in PBC content, the PPC/PBC blends showed decreased tensile strength, however, the elongation at break was increased to 230% for the 50/50 PPC/PBC blend. From the tensile strength experiments, the Pukanszky model gave credit to the modest interfacial adhesion between PPC and PBC, although PPC/PBC was immscible. The impact strength increased significantly which indicated the toughening effects of the PBC on PPC. SEM examination showed that cavitation and shear yielding were the major toughening mechanisms in the blends subjected the impact tests. TGA measurements showed that the thermal stability of PPC decreased with the incorporation of PBC. Rheological investigation demonstrated that the addition of PBC reduced the value of storage modulus, loss modulus and complex viscosity of the PPC/PBC blends to some extent. Moreover, the addition of PBC was found to increase the processability of PPC in extrusion. The introduction of PBC provided an efficient and novel toughened method to extend the application area of PPC.
Poly(propylene carbonate) (PPC) was melt blended in a batch mixer with poly(butylene carbonate) (PBC) in an effort to improve the toughness of the PPC without compromising its biodegradability and biocompatibility. DMA results showed that the PPC/PBC blends were an immiscible two-phase system. With the increase in PBC content, the PPC/PBC blends showed decreased tensile strength, however, the elongation at break was increased to 230% for the 50/50 PPC/PBC blend. From the tensile strength experiments, the Pukanszky model gave credit to the modest interfacial adhesion between PPC and PBC, although PPC/PBC was immscible. The impact strength increased significantly which indicated the toughening effects of the PBC on PPC. SEM examination showed that cavitation and shear yielding were the major toughening mechanisms in the blends subjected the impact tests. TGA measurements showed that the thermal stability of PPC decreased with the incorporation of PBC. Rheological investigation demonstrated that the addition of PBC reduced the value of storage modulus, loss modulus and complex viscosity of the PPC/PBC blends to some extent. Moreover, the addition of PBC was found to increase the processability of PPC in extrusion. The introduction of PBC provided an efficient and novel toughened method to extend the application area of PPC.
2015, 33(3): 456-464
doi: 10.1007/s10118-015-1598-y
Abstract:
The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with -cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and formed inclusion complexes (ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of -CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with -CD was also studied. The ICs were prepared with -CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the -CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to -CD of the resulted ICs increases with increasing of temperature.
The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with -cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and formed inclusion complexes (ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of -CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with -CD was also studied. The ICs were prepared with -CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the -CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to -CD of the resulted ICs increases with increasing of temperature.
2015, 33(3): 465-474
doi: 10.1007/s10118-015-1599-x
Abstract:
In this study, the glass transition and uniaxial tensile properties of a commercially available epoxy adhesive were investigated using experimental measurements and molecular dynamics (MD) simulation. Differential scanning calorimetry (DSC) was used to study the change of glass transition temperature (Tg) with cross-link density (CLD). Uniaxial tensile test was performed to measure the Young's modulus (E), Poisson's ratio () and yielding strength (sY). In MD simulation, the complicated epoxy system was simplified as the mixture of two kinds of simple molecules, with the key information well preserved and the less important details omitted. The molecular model of the cross-linked epoxy network was constructed and its mechanical properties were calculated using MD simulation. Overall, the MD simulation results agreed with experimental ones, which proved the validity of the molecular model and justified the simplification method of the industry-level epoxy system.
In this study, the glass transition and uniaxial tensile properties of a commercially available epoxy adhesive were investigated using experimental measurements and molecular dynamics (MD) simulation. Differential scanning calorimetry (DSC) was used to study the change of glass transition temperature (Tg) with cross-link density (CLD). Uniaxial tensile test was performed to measure the Young's modulus (E), Poisson's ratio () and yielding strength (sY). In MD simulation, the complicated epoxy system was simplified as the mixture of two kinds of simple molecules, with the key information well preserved and the less important details omitted. The molecular model of the cross-linked epoxy network was constructed and its mechanical properties were calculated using MD simulation. Overall, the MD simulation results agreed with experimental ones, which proved the validity of the molecular model and justified the simplification method of the industry-level epoxy system.
2015, 33(3): 475-480
doi: 10.1007/s10118-015-1600-8
Abstract:
The polymerization of 1,3-butadiene was examined by using a novel halogen-free neodymium m-nitrobenzenesulfonate (Nd(3-NBSO3)3donors)/alkylaluminum binary catalyst system. The catalyst showed fairly high activity and controllable selectivity. The microstructure of the resultant polymer was adjustable by variation of electron donor and/or the alkylaluminum. 13C-NMR and thermal analysis demonstrate that the produced polybutadienes have stereo-block chain structures of cis-1,4 and trans-1,4 segments with adjustable Tm and Tc. The neodymium sulfonate-based catalyst is believed to be significant in regulating the chain structure of polydienes and in exploring 1,3-diene polymerization mechanism.
The polymerization of 1,3-butadiene was examined by using a novel halogen-free neodymium m-nitrobenzenesulfonate (Nd(3-NBSO3)3donors)/alkylaluminum binary catalyst system. The catalyst showed fairly high activity and controllable selectivity. The microstructure of the resultant polymer was adjustable by variation of electron donor and/or the alkylaluminum. 13C-NMR and thermal analysis demonstrate that the produced polybutadienes have stereo-block chain structures of cis-1,4 and trans-1,4 segments with adjustable Tm and Tc. The neodymium sulfonate-based catalyst is believed to be significant in regulating the chain structure of polydienes and in exploring 1,3-diene polymerization mechanism.
2015, 33(3): 481-489
doi: 10.1007/s10118-015-1602-6
Abstract:
A diamine monomer o-phenylenedioxybis(5-amino-2-pyridine) was synthesized via reduction of a dinitro compound o-phenylenedioxybis(5-nitro-2-pyridine), producing a series of new polyimides from this diamine and various commercially available aromatic dianhydrides via conventional two-stage processes. The resulting polyimides are able to form tough and transparent films, with decomposition temperatures in the range of 529-551 ℃, and can be dissolved in organic polar solvents. Meanwhile, these polyimides can be degraded in a hydrazine hydrate medium, a degradation mechanism proposed by analyzing the degradation products suggests that the degradable properties could be attributed to the phenyl-2-pyridyl ether structure in the polymer. In addition, the transformation of the compound structure from dinitro compound to damine monomer in the synthetic process is discussed in respect to X-ray structure.
A diamine monomer o-phenylenedioxybis(5-amino-2-pyridine) was synthesized via reduction of a dinitro compound o-phenylenedioxybis(5-nitro-2-pyridine), producing a series of new polyimides from this diamine and various commercially available aromatic dianhydrides via conventional two-stage processes. The resulting polyimides are able to form tough and transparent films, with decomposition temperatures in the range of 529-551 ℃, and can be dissolved in organic polar solvents. Meanwhile, these polyimides can be degraded in a hydrazine hydrate medium, a degradation mechanism proposed by analyzing the degradation products suggests that the degradable properties could be attributed to the phenyl-2-pyridyl ether structure in the polymer. In addition, the transformation of the compound structure from dinitro compound to damine monomer in the synthetic process is discussed in respect to X-ray structure.
2015, 33(3): 490-498
doi: 10.1007/s10118-015-1603-5
Abstract:
This paper reports the synthesis and characteristics of a series of alkyl-substituted planar polymers. The physical properties are carefully tuned to optimize their photovoltaic performance. Depending on the length of soluble alkyl side chains which modify the structural order and orientation substantially in polymer backbones, the device performance can be improved significantly. The tuning of HOMO energy levels optimized polymers' spectral coverage of absorption and their hole mobility, as well as miscibility with fullerene; all these efforts enhanced polymer solar cell performances. The short-circuit current, Jsc for polymer solar cells was increased by adjusting polymer chain packing ability. It was found that films with well distributed polymer/fullerene interpenetrating network exhibit improved solar cell conversion efficiency. Enhanced efficiency up to 5.8% has been demonstrated. The results provide important insights about the roles of flexile chains in structure-property relationship for the design of new polymers to be used in high efficient solar cells.
This paper reports the synthesis and characteristics of a series of alkyl-substituted planar polymers. The physical properties are carefully tuned to optimize their photovoltaic performance. Depending on the length of soluble alkyl side chains which modify the structural order and orientation substantially in polymer backbones, the device performance can be improved significantly. The tuning of HOMO energy levels optimized polymers' spectral coverage of absorption and their hole mobility, as well as miscibility with fullerene; all these efforts enhanced polymer solar cell performances. The short-circuit current, Jsc for polymer solar cells was increased by adjusting polymer chain packing ability. It was found that films with well distributed polymer/fullerene interpenetrating network exhibit improved solar cell conversion efficiency. Enhanced efficiency up to 5.8% has been demonstrated. The results provide important insights about the roles of flexile chains in structure-property relationship for the design of new polymers to be used in high efficient solar cells.
2015, 33(3): 499-507
doi: 10.1007/s10118-015-1604-4
Abstract:
Miscibility, isothermal crystallization kinetics, and morphology of poly(L-lactide)/poly(trimethylene carbonate) (PLLA/PTMC) crystalline/amorphous blends were studied by differential scanning calorimetry (DSC) and optical microscopy (OM). The heterogeneity of OM images and an unchanged glass transition temperature showed that PLLA was immiscible with PTMC. During isothermal crystallization, the crystallization rate of PLLA improved when the PTMC content was low ( 20%). However, when the PTMC content was high ( 30%), the crystallization rate decreased significantly. The reason of these nonlinear changes in crystal kinetics was analyzed according to the nucleation and growth process by virtue of a microscope heating stage. The isothermal crystallization morphologies of the blends were also studied by polarized optical microscopy and the results confirmed the conclusions obtained from crystallization kinetics.
Miscibility, isothermal crystallization kinetics, and morphology of poly(L-lactide)/poly(trimethylene carbonate) (PLLA/PTMC) crystalline/amorphous blends were studied by differential scanning calorimetry (DSC) and optical microscopy (OM). The heterogeneity of OM images and an unchanged glass transition temperature showed that PLLA was immiscible with PTMC. During isothermal crystallization, the crystallization rate of PLLA improved when the PTMC content was low ( 20%). However, when the PTMC content was high ( 30%), the crystallization rate decreased significantly. The reason of these nonlinear changes in crystal kinetics was analyzed according to the nucleation and growth process by virtue of a microscope heating stage. The isothermal crystallization morphologies of the blends were also studied by polarized optical microscopy and the results confirmed the conclusions obtained from crystallization kinetics.
2015, 33(3): 508-522
doi: 10.1007/s10118-015-1609-z
Abstract:
A low-density polyethylene (LDPE) resin with excellent processing and film-forming properties is fractionated through temperature rising elution fractionation (TREF) technique. The chain structures of both the original resin and its fractions are further analyzed using high-temperature gel permeation chromatography (GPC) coupled with triple detectors (refractive index (RI)-light scattering (LS)-viscometer (VIS)), 13C-nuclear magnetic resonance spectroscopy (13C-NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and successive self-nucleation/annealing (SSA) thermal fractionation. The 13C-NMR results show that the original resin has both short chain branch (SCB) (2.82 mol%) and long chain branch (LCB) (0.52 mol%) structures. The FTIR results indicate that the methyl numbers (per 1000 C) of the fractions gradually decrease from 81 to 46 with increasing elution temperature from 25 ℃ to 75 ℃. The TREF-GPC cross-fractionation results show that the main component is collected at around 68 ℃. The molecular weight of the components in the high elution temperatures of 60 ℃ to 75 ℃ is from 2.0 103 g/mol to 2.0 106 g/mol, and the relative amount is more than 80%. In the low elution temperature region below 50 ℃, the molecular weights of the components range from 1.0 103 g/mol to 1.6 104 g/mol, and the relative amount is less than 10%. In the DSC results, the melting peaks of the fractions gradually increase from 80.1 ℃ to 108.8 ℃ with elution temperature. In the SSA thermal fractionation, each resin fraction shows a broad range of endotherm with multiple melting peaks (more than eight peaks). The melting peaks shift toward high temperatures with the elution temperature. The characteristic chain microstructure for the resin is also discussed in detail.
A low-density polyethylene (LDPE) resin with excellent processing and film-forming properties is fractionated through temperature rising elution fractionation (TREF) technique. The chain structures of both the original resin and its fractions are further analyzed using high-temperature gel permeation chromatography (GPC) coupled with triple detectors (refractive index (RI)-light scattering (LS)-viscometer (VIS)), 13C-nuclear magnetic resonance spectroscopy (13C-NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and successive self-nucleation/annealing (SSA) thermal fractionation. The 13C-NMR results show that the original resin has both short chain branch (SCB) (2.82 mol%) and long chain branch (LCB) (0.52 mol%) structures. The FTIR results indicate that the methyl numbers (per 1000 C) of the fractions gradually decrease from 81 to 46 with increasing elution temperature from 25 ℃ to 75 ℃. The TREF-GPC cross-fractionation results show that the main component is collected at around 68 ℃. The molecular weight of the components in the high elution temperatures of 60 ℃ to 75 ℃ is from 2.0 103 g/mol to 2.0 106 g/mol, and the relative amount is more than 80%. In the low elution temperature region below 50 ℃, the molecular weights of the components range from 1.0 103 g/mol to 1.6 104 g/mol, and the relative amount is less than 10%. In the DSC results, the melting peaks of the fractions gradually increase from 80.1 ℃ to 108.8 ℃ with elution temperature. In the SSA thermal fractionation, each resin fraction shows a broad range of endotherm with multiple melting peaks (more than eight peaks). The melting peaks shift toward high temperatures with the elution temperature. The characteristic chain microstructure for the resin is also discussed in detail.
