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Dielectric capacitors have attracted increasing attention for their fast charge–discharge speeds as well as high power density, and they have been widely used in advanced electronics and electric power systems. Here, dopamine-modified TiO2 (TiO2@PDA) nanosheets were synthesized via hydrothermal reaction and in situ polymerization. Then the synthesized TiO2@PDA nanosheets were introduced into the poly(vinylidene fluoride) (PVDF) matrix via solution blending. Our results reveal that loading a small amount of TiO2@PDA nanosheets can effectively enhance the energy storage performance of the nanocomposites. For example, a superior discharge energy density with 10.53 J/cm3 is obtained for the 9 wt.% TiO2@PDA/PVDF nanocomposite at 195 MV/m, which is 1.75 times as large as discharge energy density of pure PVDF (6.01 J/cm3 at 170 MV/m). Such significant improvement is due to the large aspect ratio as well as dopamine modification of the TiO2 nanosheets. The study provides a feasible way to prepare the nanocomposites with excellent energy storage performance.

Flexible dielectric materials such as poly(vinylidene fluoride)-based nanocomposites with high energy density are employed for applications in modern electronic and electric systems. In this study, we improve traditional methods by optimizing the interfacial structure, achieving a 34% increase in energy density without reduced discharge efficiency. Herein, a simple solution-cast method is used to prepare poly(vinylidene fluoride-co-trifluoroethylene) nanocomposites filled by γ-methacryloyl-propyltrimethoxysilane (MPMS) grafting barium titanate nanoparticles, forming a class of cross-linking networks by irradiation. More additional interfaces arising from irradiation cross-linking give rise to high discharge energy density, and the small crystalline domain and cross-linking network enhance the charge-discharge efficiency. Furthermore, we find two types of cross-linking centers on the network. One is more beneficial to energy density, and the other is more beneficial to efficiency. Regulating two types of cross-linking centers can balance efficiency and energy density. In summary, this work provides a promising strategy for exploiting advanced flexible dielectric materials to meet application requirements.

Polyvinylidene fluoride (PVDF) preferentially crosslinks upon exposure to ionizing electron beam irradiation, leading to substantial changes in its physicomechanical and thermophysical properties. However, low dose electron beam irradiation produces inefficient crosslinking in pure PVDF while high dose irradiation tends to induce the concomitant process of transverse bond degradation. This has been addressed by incorporating a sensitizer into PVDF to increase crosslinking efficiency under low dose irradiation. However, conventional sensitizers typically suffer from self-polymerization and the release of toxic volatile gases at high temperature, which diminishes the crosslinking efficiency and is toxic. This issue is addressed here via a series of well-designed bismaleimide (BMI) sensitizers and incorporating these into PVDF films for facilitating chemical crosslinking reactions under low electron beam irradiation doses. Analysis indicates that the sensitizing action of the proposed BMI sensitizers may be due to the formation of transverse bonds between vinylene groups and PVDF chains. Versus conventional triallyl isocyanurate and trimethylolpropane triacrylate sensitizers, the proposed BMI sensitizers facilitate high radiation crosslinking efficiency and exhibit good compatibility. Accordingly, the proposed sensitizers leading to irradiated PVDF films with outstanding thermomechanical performance and shape memory functionality.

In recent years, high energy density polymer capacitors have attracted a lot of scientific interest due to their potential applications in advanced power systems and electronic devices. Here, core–shell structured TiO2@SrTiO3@polydamine nanowires (TiO2@SrTiO3@PDA NWs) were synthesized via a combination of surface conversion reaction and in-situ polymerization method, and then incorporated into the poly(vinylidene fluoride) (PVDF) matrix. Our results showed that a small amount of TiO2@SrTiO3@PDA NWs can simultaneously enhance the breakdown strength and electric displacement of nanocomposite (NC) films, resulting in improved energy storage capability. The 5 wt% TiO2@SrTiO3@PDA NWs/PVDF NC demonstrates 1.72 times higher maximum discharge energy density compared to pristine PVDF (10.34 J/cm3 at 198 MV/m vs. 6.01 J/cm3 at 170 MV/m). In addition, the NC with 5 wt% TiO2@SrTiO3@PDA NWs also demonstrates an excellent charge–discharge efficiency (69% at 198 MV/m). Enhanced energy storage performance is due to hierarchical interfacial polarization among their multiple interfaces, the large aspect ratio as well as surface modification of the TiO2@SrTiO3 NWs. The results of this study provide guidelines and a foundation for the preparation of the polymer NCs with an outstanding discharge energy density.

Exploring polymer-based composites with a high dielectric constant and energy density simultaneously, as well as low dielectric loss, is of crucial importance because of their potential applications in modern electronics and electric power systems. Here, a multilayer-structured Ti3C2Tx MXene/poly(vinylidene fluoride) (PVDF) film with a high dielectric constant and ultralow dielectric loss is fabricated via spin coating, spray coating and hot-press methods. 4MXene/5PVDF (namely four layers of MXene and five layers of PVDF) exhibits a high dielectric constant (41) and an ultralow dielectric loss (0.028, smaller than that of pure PVDF) at 1 kHz. Surprisingly, the MXene/PVDF films show good broadband dielectric behaviors and the dielectric constant of 4MXene/5PVDF can reach up to 32.2 at 1 MHz, which can remain as high as 78.4% of that at 1 kHz. Based on the crystalline phase transformation and temperature dependence of electrical modulus results, the excellent dielectric properties are attributed to the enhanced interfacial polarization. The multilayered structure can efficiently prevent the formation of a conductive network across the entire film, leading to suppressed dielectric loss, a comparative breakdown strength with pure PVDF and a maximum discharge energy density of 7.4 J cm−3. This work provides a promising design paradigm to construct polymer films with a high dielectric constant and low dielectric loss.

Introducing conductive nanofillers into a dielectric polymer is the most common way to tailor percolative composites with high dielectric constant. However, it usually contributes to large increase of dielectric loss, thereby restricting the improvement of practical energy storage capability. In this study, by regulating the conjugation degree of graphene derivatives and their interfacial interactions with polymer matrix, high dielectric constants were achieved for graphene/polymer composites and the loss was suppressed at a relatively low level. Electrochemical exfoliated graphene with high conjugation degree modified with a carboxyl-riched perylene derivative via π-π stacking interaction was used as a conductive nanofiller. Due to the high conjugation degree of graphene and carboxyl groups-induced high interfacial interactions with PVDF matrix, a high dielectric constant (e = 480) was obtained at a low filler content of 0.74 vol% and the dielectric loss was suppressed as low as 0.27. The enhanced dielectric properties could be reasonably explained by a proposed model. This research provides a new and promising route for researchers to construct graphene/polymer composites with good dielectric properties for applications in modern electronics and electric power systems.

Poly(vinylidene fluoride) (PVDF)-based ferroelectric polymers with excellent flexibility and tuneable ferroelectric performance characteristics have attracted continuous attention for high energy storage applications. To produce ideal novel ferroelectric polymers to enhance released energy density and reduced hysteresis loss, smaller ferroelectric domains are necessary. In this study, we prepared poly(vinylidene fluoride-co-trifluoroethylene)-graft-poly(methyl methacrylate) (P(VDF-TrFE)-g-PMMA) graft copolymers via the pre-irradiation process, achieving the transition from normal ferroelectric performance to either antiferroelectric-like or linear behaviour. Compared to the atom transfer radical polymerization (ATRP), this method is attractive due to its unique merits, such as user-friendly control, short processing time and catalyst-free reaction. By using the nanoconfinement effect concept, grafted-PMMA with fairly strong intermolecular interactions was miscible with P(VDF-TrFE) in an amorphous phase, which effectively impeded the formation of large lamellar crystals. Compared to pristine film, the best performance was achieved for the irradiated grafting film with dielectric loss reduced by 67% (from 0.27 to 0.09) at 1 MHz, released energy density increased by 77% (from 2.2 to 9.5 J/cm3) and released energy efficiency improved by 80% (from 0.15 to 0.75 J/cm3). This work provides a simple and efficient strategy for the fabrication of novel dielectrics for high released energy density and low loss application.

Polymer-based nanocomposites are excellent and promising in developing dielectric and energy storage applications, and one-dimensional (1D) nanofibers with large aspect ratio exhibit superiority in improving dispersibility, dielectric properties and energy storage performance of polymer nanocomposites as compared with their spherical counterparts. In this work, novel heterostructural carbon-doped inorganic nanoassemblies (TiO2/C nanofibers, NFs) were designed and synthesized in site via easy-processing electrospinning technique. Three different carbon contents of TiO2/C NFs were obtained as 2 wt%, 4.5 wt% and 13.6 wt% by regulating precalcination conditions, respectively. P(VDF-HFP) was chosen to incorporate with different nanofibers as prepared due to its relatively high dielectric constant. A comparative study on dielectric energy storage performance of the TiO2/C NFs/P(VDF-HFP) nanocomposites has been systematically presented. The results reveal that the dielectric constant and the energy density are significantly enhanced for nanocomposites with appropriate content of doped carbon inside NFs. At relatively low doping content, the carbon nanoparticles could well disperse in TiO2/C NFs for forming numerous micro-capacitors, which is beneficial for enhancing interfacial polarization and suppressing loss. This work provides insights into the effect of the carbon-doped nanoassemblies for further improving energy storage capability of polymer nanocomposites for high-performance device applications. Keywords: TiO2/C nanofibers, Electrospinning, Nanocomposites, Dielectric, Energy storage

It is a challenge to intentionally prepare the pure PVDF film containing exclusive γ-phase (γ-PVDF film). In this study, the γ-PVDF film containing extremely rare β-phase was prepared by solution casting method. γ-PVDF films were then irradiated with 2.5 MeV electron beam in vacuum at 92, 442 and 993 kGy, respectively. Modifications of γ-PVDF films by the irradiation were detailedly investigated by FTIR, DSC, TGA and XPS measurements. FTIR results show that the irradiation does not induce the crystal phase transition and carbon-carbon double bonds (C=C bonds) are obviously formed for γ-PVDF films when irradiated at high dose of 442 and 993 kGy. In addition, the evolution process of chemical structures was proposed for γ-PVDF films by the irradiation at different dose based on FTIR and XPS analyses. For thermal properties, the irradiation decreases the melting and crystallization temperatures, and thermal decomposition temperature for γ-PVDF film due to the irradiation-induced damage effects. The sample irradiated at 92 kGy has the maximum melting and crystallization enthalpies. However, the irradiation increases the residual yield at high temperature (> 500 °C) of γ-PVDF film due to the formation of crosslinked network structures in the irradiated samples.

In this work, the thermal stability, rheological properties and mechanical properties of ethylene-tetrafluoroethylene copolymer (ETFE)/poly(vinylidene fluoride) (PVDF) blends were investigated by thermogravimetric analysis, rheometer and the tensile test. Thermal results indicated that blends had better thermal oxidation resistance than pure ETFE. Particularly, the initial thermal decomposition temperature (T d 0) and the temperature at maximum decomposition rate (T d max) of PVDF/ETFE (10/90 wt%) blends were at 374.49°C and 480°C, which were 52.6°C and 34°C higher than pure ETFE. The activation energy of thermal degradation (E d ) of ETFE was 66 kJ/mol, while the PVDF/ETFE (10/90 wt%) blends presented a higher E d , near 187 kJ/mol. Furthermore, rheological measurements demonstrated that the shear-thinning tendency of blends became stronger with increasing PVDF content. PVDF/ETFE (10/90 wt%) blends had somewhat lower mechanical properties than ETFE, which was still high enough for various applications. Blends with PVDF provided an efficient method to extend the application area of ETFE.

This work focus on improving the heat resistant and mechanical properties of poly(lactic acid)/poly(butylene succinate) (PLA/PBS) blends using appropriate contents of polyaryl polymethylene isocyan...

In this study, we successfully prepared the pure PVDF film containing almost exclusive γ-phase (γ-PVDF) using 15 wt% solution in N, N-dimethylformamide. These γ-PVDF films were irradiated by 3.0 MeV electron beam in vacuum at room temperature up to 358 kGy. The effect of the irradiation on the chemical structural and thermal properties of pristine and irradiated γ-PVDF films were detailedly investigated by FTIR, XRD and DSC, respectively. DSC results show that two single and different melting endotherms from the successive heating curves correspond to γ-phase and α-phase, respectively. FTIR results show that the characteristic absorption peaks corresponding to γ-phase do not shift, and the C˭C bond formation is not significantly observed in the irradiated γ-PVDF films until above 30 kGy. XRD results show that the crystal form of γ-PVDF is not influenced significantly by irradiation. All PVDF films exhibit a single melting endotherm, irrespective of the irradiation dose. Two superpositioned crystallization peaks were observed for PVDF films only irradiated at high dose of 232 and 358 kGy, which can be related to the fractionated crystallization of irradiated PVDF. The dependences of thermal characteristics on the irradiation dose were detailedly investigated by DSC in this study.

The microstructure evolution of partial miscible polylactide/poly(butylene carbonate) (PLA/PBC) blend during annealing, including the variation in crystalline structure of PLA and PBC, the morphologies of PBC particles, and the relaxation of chain segments in the amorphous region of PLA, is investigated in detail. Based on the significant difference in melting temperature, phase separation arises as a result of the occurrence of crystallization of PLA and is further enhanced due to the crystallization of PBC. The glass transition temperature Tg of the PLA phase in the phase separation blend is significantly higher than that of the pure PLA due to increasing crystallinity. The increasing annealing time resulted in enhanced phase separation, as reflected in the harsher morphology, the decrease of molecular dynamics, and the reduction amount of the amorphous domain. It can be verified by the interaction parameter C values at various annealing conditions from the yield stress data. Therefore, blend is aptitude to elongation decrease and the toughening micromechanism changes, while the plastic deformation is the important energy dissipation process for quenched PLA/PBC blend. Debonding of the PBC particles followed by plastic void growth of the PLA matrix is the major toughening micro-mechanisms for phase separation blend.

Inorganic montmorillonite (MMT)/poly(vinylidene fluoride) nanocomposites were prepared by two methods: co-precipitation and solution casting. The effect of preparation methods and thermal treatment on crystalline phase was investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry tests. The isothermal crystallization process was observed with polarized optical microscopy. It was found that the solution-casting method was more effective than the co-precipitation method in inducing the polar phase in the melt-isothermal crystallization process. The addition of inorganic MMT by the solution-casting method without further thermal treatment promoted the β-phase crystallization. The inorganic MMT significantly improved the γ phase of the solution-cast samples in the melt-recrystallization process. The degree of dispersion of inorganic MMT influenced the relative content of the polar phase and the crystallinity of the samples in the same crystallization conditions, i.e. the preparation method and the thermal treatment. The effect of dispersion on crystallization kinetics was also studied to verify the enhancement of finely dispersed nanolayer clusters on the γ phase.

This work focuses on improve the mechanical properties of poly(lactic acid)/poly(ethylene-co-vinyl alcohol) (PLA/EVOH) blend and simultaneously remained a high Vicat softening temperature (VST) using appropriate contents of methyl methacrylate–butadiene–styrene copolymer (MBS) via simple melt blending. The effects of MBS on the heat resistant, mechanical properties, thermal properties and rheological behavior were examined in detail with various techniques. The VST of neat PLA significantly increased to 159 °C from 66.8 °C after blending with 50 wt% EVOH. However, the VST was gradually decreased with increasing MBS content but were still much higher than that of neat PLA. On the basis of the tensile and impact tests results, PLA/EVOH/MBS blends showed a considerably higher elongation at break and impact strength. For all PLA/EVOH/MBS blends, the thermal stability was increased compared than that of PLA/EVOH blend without MBS. With increasing MBS content, the complex viscosity and storage modulus of PLA/EVOH blend increased, especially at low frequencies, indicating that MBS enhanced the chain entanglement in the PLA/EVOH matrix. In addition, the results Han curves and Cole–Cole plots indicated that the relaxation time was increased when MBS was added.

The desired electroactive β and γ phases of poly(vinylidene fluoride) (PVDF) nanostructures are rarely obtained through wetting methods using anodic aluminum oxide (AAO) as a template. Further and systematic studies on the corresponding induction mechanism are also lacking. Herein, we designed and fabricated PVDF nanowires using a solution wetting method with pristine and modified AAO templates. The morphology and crystalline structure of the PVDF nanowires were characterized by SEM and micro-FTIR respectively. Then, the induction mechanism was investigated by AFM, FTIR, TGA and contact angle measurements. It is found that the polarity of the solvent and the surface hydroxyl groups on the template nanopores both have an inductive effect on the polar phase. After the oxygen plasma treatment, the proportion of β phase of the PVDF nanowires becomes higher although the total polar phase content remains the same. This is attributed to the high polarity of the nanopore surface and regular arrangement among the hydroxyl groups. The polar phase content of the PVDF nanowires increases from 40% when prepared by the pristine template to 71% when prepared by a 3-aminopropyltrimethoxysilane (APMS) modified template. It can be explained that more interaction points and stronger interactions result in the formation of more of the electroactive phase.

Recently, as an important class of mechanically active smart materials, thermoplastic dual-shape memory polymers (SMPs) have attracted notable attention and can be fabricated in many different manufacturing techniques. Here in this paper, we present experimental results, demonstrating a cost-effective manufacturing technique to enable thermoplastic SMPs with enhanced properties for a wide variety of applications. Thermoplastic SMPs based on low density polyethylene (LDPE) and polypropylene (PP) with various compositions were prepared by melt compounding, followed by a post-processing of e-beam irradiation at 5, 10, 15, 25, 50 and 100 kGy. SEM, DSC, tensile test, rheological properties measurement, sol/gel analysis and shape memory test were performed sequentially to investigate the relationship between the phase morphologies, the content fluctuations, the e-beam irradiation and the shape memory performances. In addition, we also optimized the fabrication process and studied mechanisms of shape memory performances. It was found that the melting point associated to the LDPE soft phase Tm,LDPE is almost independent of the content fluctuations. At the same time the mechanical properties (determined at 25 °C) and rheological properties (measured at 180 °C) can be varied systematically by controlling the structure and radiation dose. More importantly, the results also revealed that (1) irradiated LDPE-rich blends were more suitable and effective than both irradiated PP-rich and non-irradiated blends to be dual-SMPs with advantageous shape memory properties, and (2) increased radiation dose could give rise to enhanced shape recovery capacity without significantly weakening the shape fixity.

Brittle polylactide (PLA) was toughened by introducing 5–25 wt % of methyl methacrylate–butadiene–styrene (MBS) copolymer. PLA/MBS blends were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), dynamic rheometer, mechanical testing, scanning electron microscopy, and transmission electron microscope. From the result of DSC, MBS could act as an effective heterogeneous nucleation agent for PLA and significantly improved the degree of crystallinity of PLA. DMA results showed a single high temperature peak of Tg between that of pure PLA and that of the shell composition of the MBS, which suggested that PLA and the shell of MBS were compatible. With an increase of MBS content, the tensile strength of the blends decreased; however, the elongation at break and impact strength increased significantly which indicated the toughening effects of the MBS on PLA. It was found that the PLA matrix showed large plastic deformation (shear yielding) in the blend subjected the impact tests, which was an important energy-dissipation process and led to a toughened polymer blend. MBS could act as impact modifier of PLA. Rheological investigation demonstrated that there was a significantly dependence of viscosity on composition. When the MBS content increased, the viscosity began to increase. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Melt blending of poly(lactic acid) (PLA) and poly(epichlorohydrin-co-ethylene oxide) copolymers (ECO) was performed to improve the toughness and crystallization of PLA. Thermal and scanning electron microscopy analysis indicated that PLA and ECO were not thermodynamically miscible but compatible to some extent. The addition of a small amount of ECO accelerated the crystallization rate and increased the final crystallinity of PLA in the blends. Significant enhancement in toughness and flexibility of PLA were achieved by the incorporation of the ECO elastomer. When 20 wt% ECO added, the impact strength increased from 5 kJ/m(2) of neat PLA to 63.9 kJ/m(2), and the elongation at break increased from 5% to above 160%. The failure mode changed from brittle fracture of neat PLA to ductile fracture of the blend. Rheological measurement showed that the melt elasticity and viscosity of the blend increased with the concentration of ECO. POLYM. ENG. SCI., 51:2370-2380, 2011. (C) 2011 Society of Plastics Engineers

Poly(L-lactide) (PLA)/silica (SiO2) nanocomposites containing 1, 3, 5, 7, and 10 Wt % SiO2 nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO2 nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition Of SiO2 nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glass-transition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving C=O of PLA with Si-OH Of SiO2 was evidenced by Fourier transform infrared analysis for the first time.

Poly(epsilon-caprolactone) (PCL), a saturated polyester, derived from ring-opening polymerization of epsilon-caprolactone, was chemically crosslinked with various amounts of benzoyl peroxide (BPO) by a two-step method by first evenly dispersing the BPO into the PCL matrix and then crosslinking at elevated temperature. The gel fraction increased with an increase in BPO content. The modified Charlesby-Pinner equation was used to calculate the ratio of chain scission and crosslinking. The results showed that both scission and crosslinking occurred, and that crosslinking predominated over scission. The number-average molecular weight between the crosslinks determined by the rubber elasticity theory using the hot set test showed a decrease with increasing BPO content. The melting temperature and crystallinity decreased with an increase in BPO content, and the crystallization temperature increased after crosslinking. Dynamic mechanical analysis results showed a decrease in the glass transition temperature as a result of chemical crosslinking of PCL. This was explained by the observed reduction in crystallinity and the increase in free volume due to restrictions in chain packing.

Poly(epsilon-caprolactone) was crosslinked by gamma radiation in the presence of triallyl isocyanurate. The influence of gamma-radiation crosslinking on the thermal and mechanical properties of poly(epsilon-caprolactone)/triallyl isocyanurate was investigated. Differential scanning calorimetry analyses showed differences between the first and second scans. Dynamic mechanical analysis showed an increase in the glass-transition temperature as a result of the radiation crosslinking of poly(epsilon-caprolactone). Thermogravimetric analysis showed that gamma-radiation crosslinking slightly improved the thermal stability of poly(epsilon-caprolactone). The 7 radiation also strongly influenced the mechanical properties. At room temperature, crosslinking by radiation did not have a significant influence on the Young's modulus and yield stress of poly(E-caprolactone). However, the tensile strength at break and the elongation at break generally decreased with an increase in the crosslinking level. When the temperature was increased above the melting point, the tensile strength at break, elongation at break, and Young's modulus of poly(epsilon-caprolactone) were also reduced with an increase in the crosslinking level. The yield stress disappeared as a result of the disappearance of the crystallites.

Dominant electroactive phases (β- and γ-phase) are induced in poly(vinylidene fluoride) (PVDF) by simply melt-blending with a small amount of quaternary phosphonium salts (QPS), required no organic treatment for regularly-used inorganic nanofillers. Two kinds of QPS with similar structure are selected to investigate the correlation between crystallization kinetics from melt and electroactive phase formation of PVDF. What is more, nearly 100% electroactive phase is achieved. Tetraphenylphosphonium bromide (TPPB) can effectively increase the crystallization rate of PVDF and initiate the PVDF crystallize into γ-phase directly from the melt. Smaller amount of tetraphenylphosphonium chloride (TPPC) added into PVDF matrix achieves an abrupt increasing of the crystallization rate and cause the PVDF trend to crystallize into β-phase. Moreover, the crystallization regime II disappears or moves to higher temperature where the crystal growth rate is controlled by segmental diffusion rate together with the secondary nucleation rate. These results can be attributed to a stronger interaction between the TPPC nanoparticles and PVDF chain segments than TPPB. The inductive mechanism of TPPB and TPPC on PVDF polymorphism behavior is also researched.

Two kinds of polylactide (PLA) which was named PLA1 with L-lactide content of 98% and PLA2 with L-lactide content of 88% were blended with poly(ethylene glycol-co-propylene glycol) (PI-PG) in a batchwise mixer and pressed into films. The effect of annealing on the thermal properties, crystallization behavior, and mechanical properties of the quenched blends were Studied by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), polar optical microscopy (POM), and tensile tests. PEPC was miscible with the two kinds of PLA in the blend composition range of 5-20 wt % and can effectively decrease the,lass transition temperature of PLA. Neat PLA2 lost the ability to crystallize in the DSC and DMA measurements; however, it could crystallize after annealing for long time and crystallize more easily due to the improved crystallizability with the addition of PFPG. Both of the PLAs underwent cold crystallization when annealing at 90 degrees C, and there were signs of phase separation occurring in the blends at the same time. The crystallization morphology and tensile properties of the annealed blends were different and dependent of the Optical purity of PLA. The blends with PLA2 after annealing regained the brittleness with maximum of elongation at break about 20% and showed larger spherulites in the POM images, whereas the blends with PLA1 after annealing still kept some flexibility with maximum of elongation at break about 65% and showed fine spherulites. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2050-2057, 2010