Crystallizability of Poly(ε-caprolactone) Blends with Poly(vinylphenol) under Different Conditions

The intermolecular interaction between poly（vinylphenol） （PVPh） and polycaprolactone （PCL） and the crystallization behavior of PCL in PCL/PVPh blends with different compositions and under different conditions were investigated by Fourier transform infrared spectra （FTIR） and differential scanning calorimetry （DSC）. It has been shown that the PCL in the blends with different blend ratios all exists in crystalline state after solution casting, even though the crystallinity decreases with increasing PVPh content. For the melt crystallized samples, PCL in its 80/20 PCL/PVPh sample can still crystallize. The crystallinity is, however, lower than that of the solution cast sample. For blends containing 50% or 20% PCL, the as-cast samples are semicrystalline and can change to compatible amorphous state after heat treatment process. FTIR analysis shows the existence of hydrogen bonding between PCL and PVPh and the fraction of hydrogen bonds increases remarkably after heat treatment process.     

THE EFFECT OF CLAY DISPERSION ON THE CRYSTALLIZATION AND MORPHOLOGY OF POLYPROPYLENE／CLAY COMPOSITES

PP/clay composites with different dispersions, namely, exfoliated dispersion, intercalated dispersion and agglomerates and particle-like dispersion, were prepared by direct melt intercalation or compounding. The effect of clay dispersion on the crystallization and morphology of PP was investigated via PLM, SAXS and DSC. Experimental results show that exfoliated clay layers are much more efficient than intercalated clay and agglomerates of clay in serving as nucleation agent due to the nano-scale dispersion of clay, resulting in a dramatic decrease in crystal size (lamellar thickness and spherulites) and an increase of crystallization temperature and crystallization rate. On the other hand, a decrease of melting temperature and crystallinity was also observed in PP/clay composites with exfoliated dispersion, due to the strong interaction between PP and clay. Compared with exfoliated clay layers, the intercalated clay layers have a less important effect on the crystallization and crystal morphology. No effect is seen for samples with agglomerates and particle-like dispersion, in regard to melting temperature, crystallization temperature, crystal thickness and crystallinity.     

EFFECT OF PROCESSING METHOD ON THE IMPACT STRENGTH OF POM/TPU/CaCO3 TERNARY COMPOSITES

Polyoxymethylene （POM）/elastomer/filler ternary composites were prepared, in which thermoplastic polyurethane （TPU） and inorganic filler, namely, CaCO3, were used to achieve balanced mechanical properties of POM. The dispersion and phase morphology of POM/elastomer/filler composites were found to depend largely on processing method, CaCO3 content in masterbatch and the filler size. Two processing methods were employed to prepare POM/elastomer/filler ternary composites. One is called the one-step method, in which elastomer and the filler directly melt blended with POM matrix. The other is called the two-step method, in which the elastomer and the filler were mixed to get masterbatch first, which was then melt blended with pure POM of different content. The effect of phase morphology and processing method on impact strength was investigated. It was found that the two-step method results in an increase in impact strength but not for the one-step method. Additionally, the impact strength of POM ternary composites decreases with the increase in the size of CaCO3 particles.     

Enhanced Crystallization Rate of Biodegradable Poly(ε-caprolactone) by Cyanuric Acid as an Efficient Nucleating Agent

The influence of cyanuric acid(CA) as an efficient nucleating agent on the crystallization behavior and morphology of biodegradable poly(ε-caprolactone)(PCL) was extensively studied in this work with several techniques for the first time. The nonisothermal melt crystallization behavior and overall isothermal melt crystallization rate of PCL were significantly enhanced by only a small amount of CA. The addition of CA apparently improved the nonisothermal melt crystallization peak temperature, overall isothermal melt crystallization rate, and nucleation density of PCL spherulites, but did not modify the crystallization mechanism and crystal structure of PCL, indicating that CA was an efficient nucleating agent for the crystallization of PCL. The possible nucleation mechanism of CA on the crystallization of PCL was also discussed on the basis of their crystal structures.     

Direct Comparison of Crystal Nucleation Activity of PCL on Patterned Substrates

A sample containing different regions with poly(ε-caprolactone)(PCL), oriented polyethylene (PE), and oriented isotactic polypropylene (iPP) films in contact with glass slide has been prepared to be observed in the same view field in an optical microscope and the crystallization of PCL in different regions during cooling from 80 °C down to room temperature at a rate of 1 °C·min^-1 was studied. The results showed that the crystallization of PCL started first at the PE surface and then at the iPP surface, while its bulk crystallization occured much later. This indicates that though both PE and iPP are active in nucleating PCL, the nucleation ability of PE is stronger than that of iPP. This was due to a better lattice matching between PCL and PE than that between PCL and iPP. Moreover, since lattice matching existed between every (hk0) lattice planes of both PCL and PE but only between the (100)PCL and (010)iPP lattice planes, the uniaxial orientation feature of the used PE and iPP films resulted in the existence of much more active nucleation sites of PCL on PE than on iPP. This led to the fact that the nucleation density of PCL at PE surface was so high that the crystallization of PCL at PE surface took place in a way like the film developing process with PCL microcrystallites happened everywhere with crystallization proceeding simultaneously. On the other hand, even though iPP also enhanced the nucleation density of PCL evidently, the crystallization of PCL at iPP surface included still a nucleation and crystal growth processes similar to that of its bulk crystallization.     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.     

Nanostructured polyelectrolyte-surfactant complex pervaporation membranes for ethanol recovery: the relationship between the membrane structure and separation performance

Polyelectrolyte-surfactant complexes (PESCs) were fabricated through the interaction of poly(acrylic acid) and four different cationic surfactants or their mixtures.PESC membranes were prepared by solution casting method and were applied in ethanol recovery from aqueous solution via pervaporation.Elemental analysis (EA),Fourier transform infrared spectroscopy (FTIR),water contact angle (CA) measurement,differential scanning calorimetry (DSC) and X-ray scattering were employed to characterize the composition,structure and properties of PESCs.The results reveal that the investigated PESCs are similar in hydrophobicity but different in hierarchical nanostructures.In separating 5 wt％ ethanol/water mixture,PESC membranes with high crystallinity will have both low flux and ethanol selectivity because of the high packing density and low permeability of crystalline regions.Meanwhile,the hierarchical nanostructures of PESC membranes change under pervaporation environment as was revealed by in situ synchrotron radiation X-ray scattering measurement.That is,the crystalline region could melt at high temperature in swelling state,thus consequently enhancing the ethanol selectivity.     

Crystalline Morphology and Crystallization Kinetics of Melt-miscible Crystalline/Crystalline Polymer Blends of Poly（vinylidene fluoride） and Poly（butylene succinate-co-24mol% hexamethylene succinate）

Poly（vinylidene fluoride） （PVDF） and poly（butylene succinate-co-24 mol% hexamethylene succinate） （PBHS）, both crystalline polymers, formed melt-miscible crystalline/crystalline polymer blends. Both the characteristic diffraction peaks and nonisothermal melt crystallization peak of each component were found in the blends, indicating that PVDF and PBHS crystallized separately. The crystalline morphology and crystallization kinetics of each component were studied under different crystallization conditions for the PVDF/PBHS blends. Both the spherulitic growth rates and overall isothermal melt crystallization rates of blended PVDF decreased with increasing the PBHS composition and were lower than those of neat PVDF, when the crystallization temperature was above the melting point of PBHS component. The crystallization mechanism of neat and blended PVDF remained unchanged, despite changes of blend composition and crystallization temperature. The crystallization kinetics and crystalline morphology of neat and blended PBHS were further studied, when the crystallization temperature was below the melting point of PBHS component. Relative to neat PBHS, the overall crystallization rates of the blended PBHS first increased and then decreased with increasing the PVDF content in the blends, indicating that the preexisting PVDF crystals may show different effects on the nucleation and crystal growth of PBHS component in the crystalline/crystalline polymer blends.     

STUDY ON THE MORPHOLOGY OF POLYVINYL CHLORIDE/POLYSTYRENE BLENDS BY ELECTRON MICROPROBE ANALYSIS*

The morphology of polyvinyl chloride/polystyrene (PVC/PS) blend samples with different mass ratios, preparedby means of solution casting and melt mixing, have been successfully examined by electron microprobe analysis (EMP). Thisexperiment was performed in a scanning electron microscope attached to an energy dispersive X-ray analyzer. Differentialscanning calorimetry was also used to investigate the phase separation of the blends. The results show that PVC and PS areincompatible and the blends have sea-islands phase structures. Blends prepared via melt mixing have finer phase-dispersionthan those prepared via solution casting.     

ELECTRICAL RESISTIVITY,CRYSTALLIZATION AND MECHANICAL PROPERTIES OF POLYPROPYLENE/MULTI-WALLED CARBON NANOTUBE/CALCIUM CARBONATE COMPOSITES PREPARED BY MELT MIXING

Polypropylene(PP)/multi-walled carbon nanotube(MWCNT)/calcium carbonate(CaCO_3)composites are prepared by melt mixing using two types of CaCO_3 of different sizes.The electrical resistivities of the composites with the two types of CaCO_3 are all lower than those of the corresponding PP/MWCNT composites at various MWCNT loadings (1 wt%-5 wt%).The morphology of the composites is investigated by field emission scanning electron microscopy (FESEM).The crystallization behavior of PP in the composites is char...     

Crystallization,Mechanical and Flame-retardant Properties of Poly(lactic acid) Composites with DOPO and DOPO-POSS

Poly(lactic acid)(PLA) composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) and DOPOcontaining polyhedral oligomeric silsesquioxane(DOPO-POSS) were prepared via melting extrusion and injection molding. The crystallization, mechanical, and flame-retardant properties of PLA/DOPO and PLA/DOPO-POSS were investigated by differential scanning calorimetry(DSC), X-ray diffraction(XRD), tensile testing, thermogravimetric analysis(TGA), limiting oxygen index(LOI),and cone calorimeter test. The DSC results showed that the DOPO added could act as a plasticizer as reflected by lower glass transition temperature and inhibited crystallization of part of the PLA; the DOPO-POSS acted like a filler in the PLA matrix and slightly improved the crystallinity of the PLA matrix. The XRD and DSC analyses indicated that the PLA composites by cold molding injection were amorphous, and the PLA composites following a heat treatment in an oven at 120 °C for 30 min achieved crystallinity. All the PLA and its composites after heat treatment had improved mechanical properties. The thermogravimetric analysis(TGA) tests showed that the PLA,DOPO and DOPO-POSS decomposed separately in the PLA/DOPO and PLA/DOPO-POSS, respectively. The cone calorimeter tests offered clear evidence that addition of the DOPO-POSS resulted in an evident reduction of 25% for the peak of heat release rate(p-HRR).It was also confirmed that the crystalline flame-retardant PLA composites after heat treatment had better flame retardant properties than the amorphous PLA composites prepared by the cold molding.     

Isothermal crystallization behavior and unique banded spherulites of hydroxyapatite/poly(L-lactide) nanocomposites

<正>Hydroxyapatite/poly(L-lactide)(HA/PLLA) nanocomposites were prepared by the solvent mixing method.The isothermal crystallization behavior was studied by differential scanning calorimetry(DSC) and polarized optical microscopy (POM).The results show that the crystallization behavior of HA/PLLA composites was strongly affected by the content of HA and crystallization temperature,and the addition of HA could promote nucleation and enhance the crystallization rate. When isothermal crystallization was carried out at 110℃,the HA/PLLA nanocomposite with 1%HA content crystallized most rapidly among all the composites and the half crystallization time was only 1.0 min.Banded spherulites were observed for the HA/PLLA composites,but no banded spherulites were seen in the crystals of PLLA under the same condition.     

Confined lamella formation in crystalline-crystalline poly(ethylene oxide)-b-poly(ɛ-caprolactone) diblock copolymers

The real time and in situ investigation of the crystallization process and structure transitions of asymmetric crystalline-crystalline diblock copolymers from the melt was performed with synchrotron simultaneous SAXS/WAXS. The asymmetric poly(ethylene oxide)-b-poly(ε-caprolactone) diblock copolymers were chosen for the present study. It was shown that the short blocks crystallized later than the long blocks and final lamellar structure was formed in all of the asymmetric diblock copolymers. The final lamellar structure was confirmed by AFM observation. The SAXS data were analyzed with different methods for the early stage of the crystallization. The Guinier plots indicated that there were no isolated domains formed before the formation of lamellae in the asymmetric diblock copolymers during the crystallization process. Debye-Bueche plots implied the formation of correlated domains during crystallization.     

Morphology, crystallization and mechanical properties of poly(ɛ-caprolactone)/graphene oxide nanocomposites

A series of nanocomposites based on poly(ε-caprolactone) (PCL) and graphene oxide (GO) were prepared by in situ polymerization. Scanning electron microscopy observation revealed not only a well dispersion of GO but also a strong interfacial interaction between GO and the PCL matrix, as evidenced by the presence of some GO nanosheets embedded in the matrix. Effects of GO nanofillers on the crystal structure, crystallization behavior and spherulitic morphology of the PCL matrix were investigated in detail. The results showed that the crystallization temperature of PCL enhanced significantly due to the presence of GO in the nanocomposites, however, the addition of GO did not affect the crystal structure greatly. Thermal stability of PCL remarkably increased with the addition of GO nanosheets, compared with that of pure PCL. Incorporation of GO greatly improved the tensile strength and Young’s modulus of PCL without a significant loss of the elongation at break.     

Proton Conductivity Improvement Effect of Cellulose on SPEEKK Based PEM

The proton exchange membranes(PEMs) were prepared through the solution mixing method of sulfonated poly(etlier ether ketone ketoneXsPEEKK) and cellulose. Cellulose was dissolved by 1-ally 1-3-methylimidazolium chioride(AMIMC1) and then mixed with sPEEKK solution. sPEEKK/cellulose(SC) composite membranes were prepared by solution casting. The membranes have high flexibility and transparency, which meant the compounding in molecular level. Meanwhile, the composite membranes showed excellent mechanical properties and high proton conductivity. The mechanical property reached 29 MPa, and the proton conductivity was as high as 0.32 S/cm. Thus, as a kind of biomaterials, cellulose could be ail excellent reinforcing material for poly(aryl ether ketone)(PAEK) based PEMs.     

TOUGHENING AND STIFFENING EFFECTS OF T-ZnOw WHISKERS ON POLYSTYRENE

The main subject of this work is about the effect of T-ZnOw on the toughness and stiffness of polystyrene (PS).In order to avoid the rupture of T-ZnOw during the melt processing,T-ZnOw/PS composites were obtained via the combination of solution blending and injection moulding methods.Although the tensile strength of the composites decreases slightly,the impact strength and tensile modulus increase with the increase of the T-ZnOw content in the matrix.The stiffness and toughness of the composites are enha...     

Crystallization behavior, thermal and mechanical properties of PHBV/graphene nanosheet composites

Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene nanosheet (GNS) composites were prepared via a solution-casting method at low GNS loadings in this work. Transmission electron microscopy revealed that a fine dispersion of GNSs was achieved in the PHBV matrix. The thermal properties of the nanocomposites were investigated by thermogravimetric analysis, and the results showed that the thermal stability of PHBV was significantly improved with a very low loading of GNSs. Nonisothermal melts crystallization behavior, spherulitic morphology and crystal structure of neat PHBV and the PHBV/GNSs nanocomposites were investigated, and the experimental results indicated that crystallization behavior of PHBV was enhanced by the presence of GNSs due to the heterogeneous nucleation effect; however, the two-dimensional (2D) GNSs might restrict the mobility of the PHBV chains in the process of crystal growing. Dynamic mechanical analysis studies showed that the storage modulus of the PHBV/GNSs nanocomposites was greatly improved.     

EFFECTS OF COUPLING AGENTS ON THE CRYSTALLIZATION BEHAVIOR OF PP/T-ZnOw COMPOSITES

The objectives of this paper are to understand the crystallization behavior of polypropylene(PP)composites with surface modified tetra-needle-shaped zinc oxide whisker(T-ZnOw).T-ZnOw was surface modified with different coupling agents,such as silane coupling agents(KH-550,KH-560)and titanate coupling agent(NDZ-105),in order to improve the compatibility between PP and T-ZnOw.DSC and POM were used to characterize the melt and crystallization behavior and the crystalline structures of the composites,respectively.The results show that the surface modified T-ZnOw acts as a nucleating agent of PP crystallization,depending on the coupling agent used for modification.KH-550 and KH-560 have more apparent role in improving the interfacial interaction than NDZ-105 and induce PP crystallization at higher temperature and with smaller spherulites size.The results also suggest that the crystallization behavior depends on not only the content of coupling agent,but also the content of the surface modified T-ZnOw used in the composites.     

Perovskite LaFeO3 supported bi-metal catalyst for syngas methanation

LaFeO3 perovskite supported Ni and Ni-Fe catalysts were prepared and applied to methanation reaction of syngas.Two preparation methods were employed.One was one-step citrate complexing method,and the other was a two step method using citrate complexing method to produce LaFeO3 and followed by loading nickel oxide on it with impregnation.The structure evolution of the sample as prepared was investigated by XRD,TPR and TEM techniques.For the former,the chemical composites of the calcined sample are NiO-Fe2O3/LaFe1-xNix O3.After reduction and reaction of CO methanation,its composites convert to Fe-Ni@Ni/LaFeO3-La2O2CO3,in which Fe-Ni@Ni is metal particles in nano-size composed of nickel core and Fe-Ni alloy shell.For the latter,the chemical composites of the calcined sample are NiO/LaFeO3; and after reduction and reaction of CO methanation,its chemical composites change to Ni/LaFeO3.Ni/LaFeO3 catalyst is a little more active, while Fe-Ni@Ni/LaFeO3-La2O2CO3 is much more stable and shows very good resistance to carbon deposition.In this work it is aimed to show that the structure and composites of the catalysts can be tailored using perovskite-type oxide as precursor prepared with different methods and conditions.Therefore,it is a promising route to prepare supported bi-metal catalysts in nano-size for a lot of metals with desired catalytic performances.     

Morphology,Crystallization Behavior and Tensile Properties of β-Nucleated Isotactic Polypropylene Fibrous Membranes Prepared by Melt Electrospinning

β-nucleated isotactic polypropylene(iPP) fibers with diameters less than 5 μm were prepared through melt electrospinning. The effects of electrospinning process and rare earth β-nucleating agent(WBG) on the crystal structure of iPP fibers were investigated. The results indicate that the addition of WBG can improve the fluidity of iPP melt remarkably and help the formation of fine fibers with thinner diameter, while the electrostatic force applied on the iPP melt is not favorable for the formation of β-crystal in iPP fibers. In addition, the morphology and crystalline structure of WBG/iPP electrospun fibers depended on the content of WBG. Both the crystallinity and the percentage of β-crystal form of WBG/iPP electrospun fibers increase with the rise of the content of nucleating agent, which endows the prepared electrospun fibers excellent mechanical properties. The β-nucleated iPP electrospun fibrous membranes prepared in this study can be used for protective clothing material, filtration media, reinforcement for composites and tissue engineering scaffolds.