Effects of co‐hard segments on the microstructure and properties thermoplastic poly(ether ester) elastomers

A thermoplastic poly(ether ester) elastomer (TPEE) is composed of polyester hard segments and polyether soft segments. Polyester and polyether segments are often homopolymer segments. This work aims at incorporating poly(butylene phthalate (PBP) as co‐hard segments in the hard segments of poly(butylene terephthalate) (PBT)‐b‐poly(tetramethylene oxide) (PTMO) thermoplastic elastomer, and investigating structures and properties of the resulting materials, denoted as (PBT‐co‐PBP)‐b‐PTMO. (PBT‐co‐PBP)‐b‐PTMO was synthesized from dimethyl terephthalate (DMT), dimethyl phthalate (DMP), PTMO (M_n = 1000 g/mol), and 1,4‐butanediol (BDO). The crystallinity of (PBT‐co‐PBP)‐b‐PTMO first decreased and then increased with increasing PBP content from 5% to 10% due to a decrease in the average sequence length of the PBT hard segments. Its elongation at break was increased by 200–350%. When the mass fractions of PBT and PBP were 42% and 8%, respectively, the (PBT‐co‐PBP)‐b‐PTMO showed the best performance in terms of permanent deformation, strength, and hardness whose values were 30%, 25 MPa, and 37 D, respectively. All the synthesized copolymers had good thermal stability with a decomposition temperature of 400°C or so. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43337.     

Deeper insights into the thermal properties of epoxy thermoset resins using torsion measurements

The glass transition temperature (T_g) of epoxy thermosets is a critical material property that depends on the component chemistry, the final cross-link density, and processing conditions. This study incorporates dynamic mechanical analysis (DMA) testing with a torsion clamp geometry on a TA Instruments DHR-2 and differential scanning calorimetry (DSC) to characterize five different two-component epoxy-amine systems. Investigation of the T_g dependence on DMA frequency and heating shows that lowering the frequency from 1 to 0.01 Hz results in a T_g very similar to that measured using DSC, while a heating rate of 0.3°C/min using DMA gives a T_g comparable to the DSC measured value at 30°C/min. The DMA technique reveals secondary relaxation transitions and peak broadening in the tan(δ) plots of poorly mixed epoxy blends, quantified using full width at half maximum (FWHM) of tan(δ) peaks, and are indicative of a non-homogeneous cross-linked network and off-ratio blending, respectively. The increase in the FWHM due to poor mixing ranges from 8% to 96%. These parameters are easily measurable and quantifiable in DMA, but are not observed in DSC. The additional DMA insights are valuable for process development and failure analysis, and can improve the understanding of epoxies.     

Differential scanning calorimetry of urea–formaldehyde adhesive resins,synthesized under different pH conditions

The purpose of this study was to investigate the effects of reaction pH conditions on thermal behavior of urea–formaldehyde (UF) resins, for the possible reduction of formaldehyde emission of particleboard bonded with them. Thermal curing properties of UF resins, synthesized at three different reaction pH conditions, such as alkaline (pH 7.5), weak acid (pH 4.5), and strong acid (pH 1.0), were characterized with multiheating rate method of differential scanning calorimetry. As heating rate increased, the onset and peak temperatures increased for all three UF resins. By contrast, the heat of reaction (ΔH) was not much changed with increasing heating rates. The activation energy (E_a) increased as the reaction pH decreased from alkaline to strong acid condition. The formaldehyde emission of particleboard was the lowest for the UF resins prepared under strong acid, whereas it showed the poorest bond strength. These results indicated that thermal curing behavior was related to chemical species, affecting the formaldehyde emission, while the poor bond strength was believed to be related to the molecular mobility of the resin used. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 422–427, 2006     

Structural,thermal, and mechanical properties of silanized boron carbide doped epoxy nanocomposites

In the presented study, the structural, thermal, and mechanical properties of the nanocomposites were investigated by doping silanized hexagonal boron carbide (h-B₄C) nanoparticles in varying proportions (0.5%, 1%, 2%, 3%, 4%, and 5%) into the epoxy resin by weight. For this purpose, the surfaces of h-B₄C nanoparticles were silanized by using 3-(glycidyloxypropyl) trimethoxysilane (GPS) to improve adhesion between h-B₄C nanoparticles and epoxy matrix. Then, the silanized nanoparticles were added to the resin by ultrasonication and mechanical stirring techniques to produce nanocomposites. The bond structure differences of silanized B₄C nanoparticles (s-B₄C) and nanoparticle doped composites were investigated by using Fourier transform infrared spectroscopy. Scanning electron microscopy and energy dispersion X-ray spectroscopy (SEM-EDS) technique was used to examine the distribution of nanoparticles in the modified nanocomposites. Differential scanning calorimetry and thermogravimetric analysis techniques were used to determine the thermal properties of the neat and s-B₄C doped nanocomposites. The tensile test and dynamic mechanical analysis were performed to determine the mechanical properties. When the experimental results were examined, changes in the bonding structure of the s-B₄C nanoparticles doped nanocomposites and significant improvements in the mechanical and thermal properties were observed. The optimum doping ratio was determined as 2% by weight. At this doping ratio, the T_g, tensile strength and storage modulus increased approximately 18%, 35%, and 44% compared to the neat composite, respectively.     

Synthesis of a novel lignin-based epoxy resin curing agent and study of cure kinetics,thermal, and mechanical properties

In this contribution, first of all, the methoxy groups of organic solvent lignin (OSL) was converted to phenolic hydroxyl groups through demethylation reaction for the purpose of fabricating demethylated organic solvent lignin (DOSL). In addition, the resulting DOSL was utilized as a renewable material to synthesize a novel esterified lignin (EDOSL) by reacting with isobutyryl chloride for curing of epoxy resin. Finally, commercial liquid diglycidyl ether of bisphenol A was cured by EDOSL in the presence of 4-dimethylaminopyridine (DMAP) used as a catalyst based on dual-curing mechanism. Dual curing is a processing methodology based upon the alliance of two diverse and compatible polymerization reactions occurring sequentially or simultaneously. According to the FTIR spectra and ¹H-NMR analyses, the demethylation of OSL, esterification of DOSL, and the curing reaction of epoxy resin with EDOSL were successfully conducted. The value of the phenolic hydrogen in the DOSL was approximately 4.89 mmol/g, which increased by 12.64% after demethylation. The thermal and mechanical performances of these cured epoxy samples were measured by DSC, DMA, TGA, and tensile testing. The epoxy system cured by 10%wt esterified lignin with 1%wt DMAP possessed the tensile strength of 71.54 ± 7.50 MPa and the initial degradation temperature (T_5%) of 370°C, which can compete fairly with commercial aromatic curing agents or other lignin-based agents studied currently for the curing of epoxy systems.     

Vitrification,devitrification, and dielectric relaxations during the non‐isothermal curing of diepoxy‐cycloaliphatic diamine

The curing of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) with a diamine based on 4,4′‐diamino‐3,3′‐dimethyldicyclohexylmethane (3DCM) was analyzed by dielectric relaxation spectroscopy (DRS) between ?100 and 220°C, at heating rates ranging from 0.1 to 2 K min^?1. The permittivity, ε′, and the loss factor, ε″, were measured by DRS in the frequency range between 1 and 100 kHz. The dielectric relaxations were correlated with the relaxations observed previously by temperature modulated differential scanning calorimetry (TMDSC) at the same heating rates and in modulation conditions of amplitude 0.2 K and a period of 60 s, which is equivalent to a measuring frequency of 16.7 mHz. The dielectric measurements showed three frequency‐dependent dipolar relaxations and one ionic relaxation, which was independent of the frequency. The dipolar relaxations were associated with the glass transition of the unreacted system and the vitrification and the devitrification processes of the system during the crosslinking reaction, and the ionic relaxation was associated with the beginning of the crosslinking reaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 558–563, 2006     

Effect of succinic acid on the shrinkage of unsaturated polyester resin

Succinic acid was presented as a small molecule low shrinkage additive (LSA) in unsaturated polyester resin (UPR). The effects of succinic acid on the volume shrinkage and the flexural strength of UPR cured at 80 ± 1°C were investigated and compared with those of macromolecule LSAs, including polyvinyl acetate (PVAc), polymethyl methacrylate (PMMA), and polystyrene (PS). The results indicated that the volume shrinkage of succinic acid/UPR specimen was significantly lower than those of specimens with macromolecule LSAs. The flexural strength of succinic acid/UPR specimen was improved. The optimal time of pre‐esterification between succinic acid and the excess dihydric alcohol in UPR was 3.0 h, and the optimal addition of succinic acid was 20 g per 100 g UPR. Compared with 2,2‐dimethyl malonic acid we put forward before, succinic acid was a cheaper and more commercial LSA, which obviously accelerated the pre‐esterification process and presented excellent antishrinkage effect. DSC showed that with the addition of succinic acid, the polymerization of UPR was distinctive. The two‐stage polymerization of UPR glue including the cross‐polymerization of UPR and the homopolymerization of polyester was changed to a one‐stage polymerization with lower exotherm and slower polymerization rate, which was optimal for UPR. FTIR and high resolution magic angle spinning nuclear magnetic resonance (HR/MAS NMR) were applied for the quantitative characterization of pre‐esterification caused by succinic acid. Succinic acid performed better effects on the polymerization of UPR as compared to previous LSAs, and finally the homogeneous micro‐structure of cured succinic acid/UPR formed and was demonstrated by SEM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41276.     

An evaluation of the curing characteristics of thermosetting epoxy carbon fiber sheet molding compounds and validation through computer simulations and molding trials

Sheet molding compounds (SMC) are ready-to-mold thermoset composite materials reinforced with discontinuous fibers, usually compression molded. Finite element (FE) based compression molding tools can be employed to optimize this process; FE tools require to define material models using raw material data measured through different characterization techniques. In this study, the cure kinetics of an epoxy-based carbon fiber SMC has been characterized by means of differential scanning calorimetry (DSC) and moving die rheometer (MDR) techniques. Based on these datasets, Claxton-Liska and Kamal-Souror models have been set and the compression molding of a validation plate was performed, both experimentally and virtually. The results indicate that, even if both characterization techniques are valid for SMC curing characterization, MDR technique enables the characterization of the material at real molding temperatures and the model based on MDR leads to more accurate results.     

Preparation and characterization of thermoresponsive poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide) hydrogel materials for smart windows

In this study, a series of thermoresponsive cross-linked copolymer poly [N-isopropylacrylamide(NIPAm)-co-N-isopropylmethacrylamide(NIPMAm)] (P-M series samples: P-M-0, 10, 20, 30, 40, where numbers are co-monomer contents) hydrogels were prepared by free radical polymerization using the main monomer N-isopropylacrylamide (NIPAm), co-monomer N-isopropylmethacrylamide (NIPMAm), cross-linking agent N, N-methylenebisacrylamide, initiator (ammonium persulfate)/catalyst, and solvent water. In addition, a series of samples [P-G series samples: P-G-0, 10, 20, 30, 40, where numbers are co-solvent glycerol content) were prepared using P-M-40 as components and water/co-solvent glycerol as a mixed solvent. The effects of co-monomer NIPMAm and co-solvent glycerol contents on the lower critical solution temperature (LCST)/freezing temperature and light transmittance as function of temperature of the prepared copolymer gels were investigated. The resulting thermoresponsive polymer gels had LCSTs in the range of 17.9 to 38.7°C and freezing points in the range of 6.3 to −38.5°C. These gels are suitable materials for smart windows that are responsive to various environmental conditions.     

Quasi‐isothermal DSC testing of epoxy adhesives using initial fast heating rates

Three major factors decrease the accuracy of the cure measurement in standard‐isothermal testing using differential scanning calorimetry (DSC). First, cure occurs during the heating step. Second, data are lost during the stabilization period between the dynamic and isothermal step. Third, the baseline selection requires a modification to the protocol. An alternative, which is explored in this study, is the use of fast ramps, which decrease the heating time, but this has been avoided due to overshoot that occurs between the dynamic and isothermal step, which is troublesome for systems with autocatalytic kinetics. By mitigating these factors, a quasi‐isothermal protocol was developed. Therefore, more complete cure kinetics were captured with the implementation of fast DSC to decrease the ramp time and through the optimization of furnace parameters to decrease stabilization time and temperature overshoot. The data suggested this quasi‐isothermal analysis more accurately measured the isothermal curing kinetics of a commercial epoxy adhesive at 110, 115, and 120 °C for fast ramps of 175, 350, and 500 K/min compared to the traditional ramp of 5 K/min. The enthalpy spike at the dynamic to isothermal transition remains an issue; however, an empirical shift can be used to compensate for the enthalpy signal lag. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45425.     

Preparation,characterization, electrical and antibacterial properties of sericin/poly(vinyl alcohol)/poly(vinyl pyrrolidone) composites

In this study, we focused on the fabrication of poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP)/sericin composites via a simple solution‐blending method. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, UV spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and measurements of the conductivity, tensile strength, and antibacterial activity against Staphylococcus aureus. The results of FTIR and UV spectroscopy implied the occurrence of hydrogen bonding between sericin and the PVA/PVP blend. The structure and morphology, studied by XRD and SEM, revealed that the sericin particles were well dispersed and arranged in an orderly fashion in the blend. The glass‐transition temperature (T_g) of the composite was higher than that of the pure blend, and the T_g value shifted toward higher temperatures when the volume fraction of sericin increased. TGA indicated that sericin retarded the thermal degradation; this depended on the filler concentration. The mechanical and electrical properties, such as the tensile strength, alternating‐current electrical conductivity, dielectric constant, and dielectric loss of the composites, were higher than those of the pure blend, and these properties were enhanced when the concentration of sericin was increased up to 10 wt % filler content, whereas the elongation at break of the composite decreased with the addition of sericin particles. The antibacterial properties of the composite showed that sericin had a significant inhibitory effect against S. aureus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43535.     

Influence of BaTiO3 submicrometric particles on the structure,morphology, and crystallization behavior of poly(vinylidene fluoride)

Real uniform dispersion of barium titanate, BaTiO₃, submicrometric particles within Poly(vinylidene fluoride), PVDF, was achieved to understand induced structure, morphology, and crystallization process of the polymer. Composites with uniform dispersions of BaTiO₃ particles within PVDF were accomplished for the first time, blending the polymer with particles by high energy ball milling, HEBM. Different compositions in PVDF/BaTiO₃ composite were considered (0, 1, 5, and 10 weight percent of particles). Morphology and structure were studied by scanning electron microscopy, SEM, and X‐ray diffraction, XRD, respectively. From dynamic experiments by differential scanning calorimetry, DSC, thermal transitions were determined and melting and crystallization processes were studied. To understand the main mechanism by which specific morphologies can be obtained a deep kinetic analysis of the PVDF crystallization process was carried out. Cooling rate and BaTiO₃ content did not provide important variations in the PVDF crystalline structure and morphology; however, the presence of BaTiO₃ particles seemed to favor an athermal nucleation, leading to higher fraction of crystals in shorter times. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41497.     

Influence of particle size and glassy carbon content on the thermal,mechanical, and electrical properties of PHBV/glassy carbon composites

Glassy carbon (GC) constitutes a promising carbonaceous material that can be employed as an antistatic agent in the development of antistatic packaging used in the electronics industry. Thus, the present work aims at developing biodegradable and antistatic packaging from poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) reinforced with different GC contents (0, 0.5, 1.0, 2.5, and 5.0 wt%) and different GC particle size (<45 μm and > 75 μm) using extrusion processing. differential scanning calorimetry analysis shows that the addition of GC decreases the degree of crystallinity (X_c) of PHBV, which can explain the reduction of its stiffness. Impedance spectroscopy results reveal that the use of GC contents greater than 2.5 wt% (GC > 75 μm) makes possible the obtainment of a material with an electrical resistivity small enough to be used in antistatic packaging. It can be concluded that GC is an interesting alternative of antistatic agent for electrically dissipative packaging.     

Effects of physical confinement (< 125 nm) on the curing behavior of phenolic resin

How the physical confinement of phenolic resin in nano porous silica (8 nm ≤ pore diameter (D_p) ≤ 125 nm) affected the polymer's curing behavior was examined by conducting differential scanning calorimetry experiments at 320 K ≤ T ≤500 K. Our results suggested that upon incorporating the phenolic resin into the silica, its curing temperature was lowered. However, what was interesting was that there was an inverse linear dependence between the pore size and the curing temperature, i.e., the smaller the pore diameter the higher the curing temperature. There was evidence that phenolic resin was unable to penetrate into 8 nm‐sized pores. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Silane-functionalized Al2O3-modified polyurethane powder coatings: Nonisothermal degradation kinetics and mechanistic insights

This work reports on nonisothermal degradation kinetics of polyurethane (PU)-based powder coatings containing 1, 3, and 5%wt% vinyltrimethoxysilane functionalized Al₂O₃ (V-Al₂O₃) nanoparticles. Thermogravimetric analysis of PU/V-Al₂O₃ powder coatings with different V-Al₂O₃ contents has been performed at different heating rates. Variation of activation energy (E_a) of PU/V-Al₂O₃ powder coatings was modeled as a function of partial mass loss by using Kissinger–Akahira–Sunose, Ozawa–Wall–Flynn and modified Coats–Redfern isoconversional approaches. The results revealed hindered decomposition process of PU/V-Al₂O₃ nanocomposite powder coatings, featured by an increase in activation energy of degradation from ∼158 for blank PU to 225, 183, and 229 kJ/mol for nanocomposites filled with 1, 3, and 5 wt% of V-Al₂O₃, respectively. Likewise, pre-exponential factor values increased for samples containing V-Al₂O₃ nanoparticles compared to that of blank sample. Sestak–Berggren kinetic model appropriately captured thermal degradation behavior of PU/V-Al₂O₃ nanocomposites than that of nth order decomposition kinetic reaction models.     

Effect of SiC whisker on benzoxazine‐epoxy‐phenolic ternary systems: Microwave curing and thermomechanical characteristics

Microwave radiation at 2.45 GHz with variable power input was investigated as a tool to facilitate the curing reaction of benzoxazine‐epoxy‐phenolic molding compound i.e., BEP893. Dielectric filler for microwave coupling was silicon carbide whisker (SiC_w). Factors such as whisker loading and input irradiation power were found to have a profound effect on the microwave heating of the BEP893 particularly on the rate of temperature rise and maximum heating temperature. The SiC_w loading of 10% by weight with the microwave irradiation condition of 300 W for 10 min renders the ultimate curing of the molding compound. Significant reduction in processing time of the microwave cured sample compared with the conventional heat cured sample i.e., 150 min at 200°C using conventional heating is the key benefit of this technique. Mechanical properties of the microwave cured and conventional heat cured samples show similar characteristics with slightly lower T_g in the microwave cured samples. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis,crosslinking, and characterization of energetic polymers through the azidification of glycidyl ether prepolymers

Low‐molecular‐weight atactic poly(propylene oxide) and poly(epichlorohydrin) (PECH) were chlorinated on average up to 4.42 chlorine atoms per repeat unit. A study of the products showed that chlorine substitution preferentially occurred on already chlorinated repeat units, yielding chlorine ‐rich and chlorine ‐poor sequences. As the extent of chlorine substitution increased, the glass‐transition temperature of the polymers markedly increased, and their solubility in most of the organic solvents drastically decreased. The chlorinated polymers were azidified with NaN₃ in dimethyl sulfoxide solutions. An analysis showed that azide groups replaced 99.8–99.9% of the initially present chlorine atoms. As the azide content of the samples increased, initially opaque polymers become dark brown, and their solubility increased in water but decreased in organic solvents. Samples with approximately four or more azide groups per repeat unit were only soluble in dimethyl sulfoxide and water. The standard enthalpy of formation of the polymers became increasingly positive as the azide content increased. The enthalpy of formation of a sample with 4.42 N₃/repeat unit was 6929 kJ/repeat unit, whereas this value was only 103 kJ/mol for classical GAP. An azidified sample from PECH (4.42 N₃/repeat unit) was crosslinked with a commercial triisocyanide into a rubbery product. The density and ultimate tensile strength of the rubbery product were 1.44 g/cm³ and 4.84 MPa, and it swelled about 10% at 20°C in water.© 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3785–3790, 2004     

Waste ground rubber tire powder/thermoplastic vulcanizate blends: Preparation,characterization, and compatibility

In this article, waste ground rubber tire (WGRT) powder was introduced into thermoplastic vulcanizate (TPV) to prepare the blends of WGRT powder/TPV. The mechanical, rheological, thermal aging, and dynamic properties of the blends were investigated with respect to the particle size and dosage of WGRT powder. The results showed that tensile strength, tear strength, elongation at break, and tensile permanent deformation of the blends increased with the decrease in WGRT particle size and decreased with the dosage of WGRT. The effects of different types and dosages of compatibilizers on mechanical and rheological properties of the blends were studied. The results showed that the compatibilizer PP‐g‐MAH could effectively improve the interfacial compatibility between WGRT and the TPV matrix to enhance the comprehensive properties of blends. The TPV/WGRT/PP‐g‐MAH blends obtained the best overall properties when prepared at the weight ratio 100/30/5. Rheological studies demonstrated that the WGRT/TPV blends represented lower apparent viscosity after PP‐g‐MAH were added, which means that processing performance of the blends was improved by PP‐g‐MAH. Scanning electron microscopy was used to study the morphologies of the blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39868.     

Curing kinetics of a “green” thiol‐containing resin: Oligo(ethylene‐2‐mercaptosuccinate)

This work focuses on examining the curing process of neat oligo(ethylene‐2‐mercaptosuccinate) using differential scanning calorimetry (DSC), rheology, and Fourier transform infrared (FTIR) spectroscopy. The thiol‐containing resin offers much promise as a bioabsorbable polymer in medical field and as a reusable thermoset in sustainable applications. Although curing between thiol groups has been investigated in solutions, studies of neat materials without solvent are rare. Here, the evolution of glass transition temperature (T_g), complex shear modulus (G*), gelation, and chemical structure are monitored as a function of isothermal curing time and temperature. Both T_g and G* increase with curing, indicating the formation of polymer networks. The conversion of the cure is determined from the DiBenedetto equation and is found to follow a second‐order plus second‐order autocatalytic reaction model. Importantly, the intensity of the S–H bond absorption decreases with the extent of curing, which confirms the curing mechanism, i.e., disulfide formation between the thiol groups. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43205.     

Poly(l‐lactic acid) with the organic nucleating agent N,N,N′‐tris(1H‐benzotriazole) trimesinic acid acethydrazide: Crystallization and melting behavior

N,N,N′‐Tris(1H‐benzotriazole) trimesinic acid acethydrazide (BD) was synthesized from 1H‐benzotriazole acetohydrazide and trischloride to serve as an organic nucleating agent for the crystallization of poly(l ‐lactic acid) (PLLA). First, the thermogravimetric analysis of BD exhibited a high thermal decomposition temperature; this indicated that BD maybe used as a heterogeneous nucleating agent of PLLA. Then, the effect of BD on the crystallization and melting behavior of PLLA was investigated through differential scanning calorimetry, depolarized light intensity measurements, and wide‐angle X‐ray diffraction. The appearance of a nonisothermal crystallization peak and increases in the glass‐transition temperature and the intensity of the diffraction peak suggested that the presence of BD accelerated the overall PLLA crystallization. Upon cooling at a rate of 1°C/min, the addition of just 0.5 wt % BD to PLLA increased the onset crystallization temperature from 101.4 to 111.3°C, and the nonisothermal crystallization enthalpy increased from 0.1 to 38.6 J/g. The isothermal crystallization behavior showed that the crystallization half‐time of PLLA with 0.5 wt % BD (PLLA/0.5% BD) decreased from 49.9 to 1.1 min at 105°C. However, the equilibrium melting point of PLLA/0.5% BD was lower than that of the pristine PLLA; this resulted from the increasing nucleating density of PLLA. The melting behavior of PLLA/0.5% BD further confirmed that BD improved the crystallization of PLLA, and the double‐melting peaks of PLLA/0.5% BD were assigned to melting–recrystallization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42402.