Effect of Malonic Acid Treatment on Crystal Structure,Melting Behavior,Morphology, and Mechanical Properties of Isotactic Polypropylene/Nano-CaCO3 Composites

The influence of malonic acid (MA) treatment of nano-calcium carbonate (CaCO₃) on the crystallization, morphology, and mechanical properties of isotactic polypropylene (iPP)/nano-CaCO₃ composites have been studied. The results of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized light microscopy (PLM) show that untreated nano-CaCO₃ facilitates the formation of α phase, while MA treated nano-CaCO₃ increases the relative content of β phase of iPP dramatically. The results of scanning electron microscopy (SEM) show that MA treated nano-CaCO₃ has better dispersion in the matrix than the untreated one. The toughness of PP/MA treated nano-CaCO₃ composite is improved drastically. When 2.5 wt% MA treated nano-CaCO₃ is added, the Izod notched impact strength reaches its maximum, which is 2.89 times greater than that of the pure iPP.     

Effect of Surface Structure of Nano-CaCO3 Particles on Mechanical and Rheological Properties of PVC Composites

To study the effect of different surface structures on resultant mechanical and rheological properties, nano-CaCO₃ particles were treated with isopropyl tri-stearyl titanate (H928), isopropyl tri-(dodecylbenz-enesulfonyl) titanate (JN198), and isopropyl tri-(dioctylpyrophosphato) titanate (JN114). Scanning electron microscopy (SEM) and dynamic mechanic analysis (DMA), carried out to characterize the effective interfacial interaction between the nano-CaCO₃ particles and a poly(vinyl chloride) (PVC) matrix, indicated that JN114 treated nano-CaCO₃ particles had the strongest interfacial interaction with a PVC matrix, while H928 treated nano-CaCO₃ had the weakest. The rheological and mechanical properties of PVC/nano-CaCO₃ composites were investigated as a function of surface structure and filler volume fraction. The tensile yield stress and elongation at break decreased with the increasing of calcium carbonate content while tensile modulus increased. PVC filled with JN114 treated nano-CaCO₃ had the highest tensile modulus and tensile yield stress, while those filled with H928 treated nano-CaCO₃ had the highest elongation at break at the same filler content. The impact strength of PVC/nano-CaCO₃ composites increased with the increasing of CaCO₃ content, and PVC composites filled with JN198 treated nano-CaCO₃ particle had a higher impact strength than those with JN114 or H928 treated, with the value reaching 23.9 ± 0.7 kJ/m² at 11 vol% CaCO₃, four times as high as that of pure PVC. Rheological properties indicated that a suitable interfacial interaction and a good dispersion of inorganic filler in a PVC matrix could reduce the viscosity of PVC/nano-CaCO₃ composites. The interfacial interaction was quantitatively characterized by semiempirical parameters calculated from the tensile strength of PVC/nano-CaCO₃ composites to confirm the results from the SEM and DMA experiments.     

The Effects of Different Processing Methods on the Morphology and Properties of PP/EPDM/Nano-CaCO3 Ternary Blend

The effects of different processing methods (direct extrusion, two-step extrusion or lateral injection extrusion) on the morphology of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM)/calcium carbonate nanoparticles (nano-CaCO₃) ternary blend were investigated, including the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles, by means of scanning electron microscopy (SEM). The results showed that the processing methods had a significant influence on the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles. In the lateral injection extruded blends, it was amazingly observed that the EPDM particles encapsulated the PP phase tightly, and the dimension of EPDM particles was remarkably decreased. It was also found that the content of nano-CaCO₃ particles in the matrix of the lateral injection extruded blends was less than that of the two-step extruded blend, and that of the direct extruded blend was most. The properties of the ternary blend, including dynamic mechanical properties, rheological properties, and crystallization, were characterized in order to confirm the variety of morphologies caused by the different processing methods. The differences in the crystallization temperature, elastic modulus, and glass transition temperature of the blends prepared by different methods well agreed with the variation of their morphology.     

Effect of Filler Treatment on Crystallization,Morphology and Mechanical Properties of Polypropylene/Calcium Carbonate Composites

Pimelic acid (PA) was used as a new surface modifier for CaCO₃. The effects of PA treatment on the crystallization, morphology, and mechanical properties of PP/CaCO₃ composites were investigated. Fourier transform infrared (FTIR) spectroscopy analysis revealed that PA bonded to CaCO₃ and formed a calcium pimelate surface layer after reacting with CaCO₃. The results of wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and polarized light microscopy (PLM) proved that the PA treated CaCO₃ induced a large amount of β -iPP and decreased the spherulitic size of PP. The results of scanning electron microscopy (SEM) showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between PP and CaCO₃. The toughness of the composites was improved by the more ductile β -form spherulites. When 1% of PA treated CaCO₃ was added, the notched impact strength reached its maximum, a value of 19.79 kJ/m², which was 3.64 times greater than that of the pure PP.     

Crystallization and Thermal Conductivity of CaCO3 Nanoparticle Filled Polypropylene

Isotactic polypropylene (IPP) and calcium carbonate (CaCO₃) nanocomposites were prepared by melt extrusion in a twinscrew extruder. The effect of CaCO₃ nanoparticles on the crystallization and thermal conductivity (TC) of PP was studied by thermal analysis (DSC) and thermal conductivity analysis (TCA). The introduction of CaCO₃ nanoparticles resulted in an increase in crystallinity. The incorporation of this nanoparticle (up to 15 phr) caused a significant increase of TC of PP, especially for larger filler content. Several models were used for prediction of TC of the nanocomposites. The experimental results had a good correlation with the Ce Wen Nan Model.     

Thermal Behavior of Polypropylene-g-glycidyl Methacrylate Prepared by Melt Grafting

The thermal behaviors of glycidyl methacrylate (GMA)-grafted polypropylene (PP) (PP-g-GMA) with two different grafting degrees, namely, GPP1 and GPP2, were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), and thermogravimetrical analysis (TGA). DSC results suggested that the GMA grafted PP exhibited higher crystallization temperature T_c, higher melting temperature T_m, and higher crystallinity compared with the neat PP. The isothermal crystallization kinetics was analyzed with the Avrami equation and the total crystallization activation energy was calculated. It was concluded that the crystallization processes of PP and the grafted PP were controlled by nucleation and the values of the crystallization activation energy of PP and the grafted PP were almost identical. POM results suggested that the GMA grafted PP exhibited smaller spherulites size compared with the neat PP. WAXD patterns indicated that the neat PP encouraged the formation of γ phase, compared with the grafted PP, during the crystallization process. DMA results showed that melt grafting did not induce a clear effect on the γ-transition and β-transition of the amorphous phase but resulted in a decrease in mobility of the PP chains in the crystals. TGA curves suggested that the melt grafting slightly improved the thermal stability of PP.     

On the synthesis of AlPO4-21 molecular sieve by vapor phase transport method and its phase transformation to AlPO4-15 molecular sieve

An experimental design was applied to the synthesis of AlPO₄-21 molecular sieve (AWO structure) by vapor phase transport (VPT) method, using tetramethylguanidine (TMG) as the template. In this study, the effects of crystallization time, crystallization temperature, phosphor content, template content and water content in the synthesis gel were investigated. The materials obtained were characterized by X-ray diffraction, scanning electron microscopy and fourier transform infrared spectroscopy (FT-IR). Microstructural analysis of the crystal growth in vapor synthetic conditions revealed a revised crystal growth route from zeolite AlPO₄-21 to AlPO₄-15 in the presence of the TMG. Homogenous hexagonal prism AlPO₄-21 crystals with size of 7 × 3 μm were synthesized at a lower temperature (120 °C), which were completely different from the typical tabular parallelogram crystallization microstructure of AlPO₄-21 phase. The crystals were transformed into AlPO₄-21 phase with higher crystallization temperature, longer crystallization time, higher P₂O₅/Al₂O₃ ratio and higher TMG/Al₂O₃ ratio.     

Effect of Spherical Nanoparticles on the Motion of Macromolecular Chains and Segments of Isotactic Polypropylene. I. Dynamic Mechanical and Thermal Properties

The role of spherical nano-CaCO₃ particles treated with 2 wt% and 6 wt% stearic acid (SA), respectively, on the motion of macromolecular chains and segments of isotactic polypropylene (iPP) was studied through the dynamic mechanical analysis and nonisothermal crystallization. Higher nucleation activity of the particles and more nucleating sites were achieved in the 6 wt% SA treated particle nanocomposites with respect to the 2 wt% SA counterpart. The increased nucleation efficiency caused high inhomogeneity and thus large mobility of the amorphous phase of iPP, which favored a low glass transition temperature (T_g ) in the nanocomposites. However, the spherical nanoparicles also spatially restrained the motion of macromolecular chains and segments, and the better the nanoparticles dispersed, the stronger the restriction was. Thus the glass transition temperature (T_g ) of the nanocomposites decreased with increasing filler loading but recovered at a certain particle concentration. At this filler content, the maximal α-transition temperature (T_α ) and the main melting peak temperature (T_m1 ) as well as the lowest degree of crystallinity (X_PP ) also occurred. This critical filler loading appeared at lower value (20 wt%) in 6 wt% SA treated nano-CaCO₃ composites with respect to 2 wt% SA counterpart (25%) due to the better dispersion of particles in the former. It was concluded that the mobility of the macromolecular chains and segments of iPP was dominated by the competition of the spatial confinement and nucleation effect of nano-CaCO₃ particles in the matrix.     

Non-isothermal crystallization kinetics of alkyl-functionalized graphene oxide/high-density polyethylene nanocomposites

Dodecyl amine-functionalized graphene oxide (DA-GO) was obtained via an amidation reaction. The results of X-ray diffraction and Fourier-transform infrared spectroscopy verified that long alkyl chains of DA were successfully grafted on the GO sheets. Transmission electron microscope and scanning electron microscope techniques illustrated that homogeneously dispersed DA-GO/high-density polyethylene (HDPE) nanocomposites were obtained. The effects of DA-GO on the non-isothermal crystallization of HDPE were then investigated by differential scanning calorimetry (DSC) at various cooling rates (2, 5, 10, and 20?°C/min). Significant increase in the onset crystalline temperature (T_o) and the peak crystallization temperature (T_p) of HDPE incorporating DA-GO indicated the strong nucleating ability of DA-GO. The investigation of half-time crystallization time (t_1/2) demonstrated that crystallization rate of HDPE consisting of DA-GO is faster than that of pure HDPE at a given cooling rate. Ozawa, Avrami, and the combined Avrami–Ozawa methods (Mo) were used for analyzing experimental data. The Mo approach was successful in describing the non-isothermal crystallization process of DA-GO/HDPE nanocomposites. The results indicated that low DA-GO content accelerates the crystallization of HDPE, while higher content hinders the crystallization of HDPE.     

Flexural Properties of Poly-L-Lactide and Polycaprolactone Shape Memory Composites Filled with Nanometer Calcium Carbonate

The flexural properties of poly-L-lactide (PLLA) and polycaprolactone (PCL) shape memory composites filled with nanometer calcium carbonate (nano-CaCO₃) were determined at room temperature. The results showed that with the increase of the nano-CaCO₃ weight fraction the flexural moduli and strength of PCL/nano-CaCO₃ composites increased roughly linearly and reached a maximum at the filler content of 2%, while the flexural strength of the composites decreased. The flexural moduli and strength of the composites decreased roughly linearly with increasing PLLA/PCL ratio for the PLLA/PCL/nano-CaCO₃ composites.     

Clay‐induced Preferred Orientation in Polyethylene/Compatibilized Clay Nanocomposites

Nanocomposites of the organically modified clay Cloisite^® 15A (CL15A) dispersed in HDPE‐g‐MA were prepared by melt‐compounding. Microcomposites of the same clay with HDPE were also obtained with similar procedures. The spherulitic morphology of the polymer matrix was evidenced by optical microscopy in thin films, whereas the structure of the up to 2‐mm–thick, compression‐molded samples was investigated by WAXD and SAXS. Preferred orientation of both the clay and the HDPE crystallites were evidenced in the microcomposites and, to a greater extent, in nanocomposites, whereas in HDPE and HDPE‐g‐MA control specimens hardly any anisotropy was detected. The degree of orientation of PE crystals increases with CL15A concentration, but also with clay exfoliation, with lower cooling rates and decreasing sample thickness. The orientation of the clay platelets parallel to the compression‐molded surface appears to be determined by the platelets anisotropy and by shear in the mixing and the compression‐molding procedures. In turn, it determines the preferred uniaxial orientation of HDPE crystals, which have their crystallographic a axis orthogonal, while b and c are coplanar, to the sample surface, as already reported in the literature for melt‐crystallized HDPE films with thickness below 0.3 μm. It is proposed that the HDPE orientation results from confined crystallization between parallel clay platelets which are on average less than 0.1 μm apart. Simple models, qualitatively accounting for the observed orientation of HDPE, are discussed. Organized architectures resulting from confined crystallization of the polymer matrix in nanocomposites with appropriate anisotropic fillers may be a general feature, important in determining key properties of these systems.     

Effect of Interfacial Structure on Crystallization Behavior of Polypropylene/Polyolefin Elastomer/Barium Sulfate Ternary Composites

In this paper, interfacial structure induced development of crystallization behavior of polypropylene (PP)/polyolefin elastomer (POE)/barium sulfate (BaSO₄) ternary composites was studied by DSC. Two kinds of PP (copolymer and homopolymer) were used. The compatibility between PP and POE had a distinct influence on nucleation and crystal growth of PP in PP/POE binary composites. The crystallization rate of PP homopolymer increased because of the heterogeneous nucleation by POE, while the crystallinity of PP homopolymer decreased because of an inhibition effect of the hexane side chains in POE. BaSO₄ particles acted as heterogeneous nucleating agents of PP in ternary composites. The dispersion of BaSO₄, controlled by interfacial design, had a distinct influence on the nucleation activity of BaSO₄ in ternary composites. Interfacial structure had the same effect on nucleation activity of BaSO₄ particles and crystallization rate of PP matrix in PP copolymer ternary composites as those in PP homopolymer ternary composites.     

Reactive Compatibilization of Poly(trimethylene terephthalate)/Polypropylene Blends by Polypropylene‐graft‐Maleic Anhydride. Part 1. Rheology,Morphology, Melting,and Mechanical Properties

Poly(trimethylene terephthalate)/polypropylene (PTT/PP) blends were prepared by melt blending. The rheology, morphology, melting, and mechanical properties of PTT/PP blends were investigated with and without the addition of polypropylene‐graft‐maleic anhydride (PP‐g‐MAH). The melt viscosity results showed that the fluid behavior of PTT/PP blends exhibited great disparity to that of PTT but similar to that of PP; the dispersed flexible PP phase in the blends served as a “ball bearing effect” under shear stress, which made the fluid resistance markedly reduced; by contrast, the relatively rigid PTT dispersed phase made only a small contribution to the viscosity. With 5 wt.% PP‐g‐MAH addition during melt processing, both the shear viscosity and the non‐Newtonian index of 70/30 PTT/PP blend were increased over that of the corresponding uncompatibilized one, whereas the shear viscosity of the 30/70 PTT/PP melt decreased slightly indicating that a considerable amount of PP‐g‐MAH did not act as compatibilizer but probably served as plasticizer.

With the increasing of the other component, the melting temperature of the PTT phase showed a slight decrease while the melting temperature of the PP phase showed a slight increase. 5 wt.% PP‐g‐MAH addition had little influence on the melting temperatures of the two components. When PP≤20 wt.%, the cold crystallization temperature of the PTT phase (T_cc (PTT‐phase)) showed little change with the composition; however, it shifted to higher temperature when PP≥30 wt.%. The variations of the T_cc (PTT‐phase), with and without PP‐g‐MAH, suggested that, when PTT was a minor component, the excess PP‐g‐MAH which did not act as compatibilizer might serve as a plasticizer that made the PTT's cold crystallization process to be easier. The SEM results indicated that, for the uncompatibilized blends, the interfaces from particles pulling‐out are clear and smooth, while, for compatibilized blends, the reactive products are at the interfaces. The mechanical properties suggested that PP‐g‐MAH did not result in significant improvement of the toughness of the blend, but the tensile strength increased markedly.     

Toughening of Propylene‐ethylene Copolymer/Calcium Carbonate Composites with High‐Density Polyethylene

Propylene‐ethylene copolymer/calcium carbonate (CaCO₃) composites (weight ratio=50/50) toughened with high density polyethylene (HDPE) were prepared using a twin‐screw extruder; the HDPE content in composites was in the range of 0–4 wt.%. The notched impact strength of propylene‐ethylene copolymer/CaCO₃ composites with 1.5 wt.% HDPE was 46% higher than that of propylene‐ethylene copolymer/CaCO₃ composites. Differential scanning calorimetry (DSC) experiments showed that good miscibility between propylene‐ethylene copolymer and HDPE enhanced the interpenetration of the macromolecules located in the interface. It was shown that debonding of the small HDPE particles within the propylene‐ethylene copolymer matrix resulted in the formation of small voids; the subsequent plastic deformation of the propylene‐ethylene copolymer matrix next to the voids thinned the ligaments and led to large energy consumption.     

The Role of Poly(phenylene sulfide) Microfibrils in Isothermal Crystallization of Isotactic Polypropylene under Shear

An optical polarizing microscope with a hot shear stage was used for an in‐situ investigation of the influences of poly(phenylene sulfide) (PPS) microfibrils on isothermal crystallization of isotactic polypropylene (iPP) under shear. As the nucleation sites on the PPS microfibril's surface are not able to induce a transcrystalline layer, there are only spherulites generated in a PPS/iPP in‐situ microfirbillar blend in quiescent condition. Applying shear during isothermal crystallization, the crystalline morphology greatly changes. There are fibrillar nuclei induced after steady shear with a shear rate of 5 and 10 s^–1, and these nuclei formed fibrillar crystals after crystallization completion. Two opposite effects coexist in PPS/iPP in‐situ microfibrillar blends during shear‐induced isothermal crystallization; one is the obstructive effect of PPS microfibrils on the iPP molecular chains orientation; the other is the positive effect provided by stress between fiber and matrix, generated by shear, which reduces the potential barrier of crystallization. The results of wide angle x‐ray diffraction (WAXD) show that there are β‐iPP crystals generated in neat iPP and PPS/iPP blends, but that PPS microfibrils have an inhibiting influence on the formation of β‐iPP.     

Biomimetic nucleation and growth of hydrophobic vaterite nanoparticles with oleic acid in a methanol solution

Hydrophobic vaterite nanoparticles were prepared via crystallization of CaCO₃ with oleic acid in methanol by mimicking the process of biomineralization. The molar ratio of oleic acid to calcium ion was varied from 0.1 to 0.5. By changing the concentration of the oleic acid, CaCO₃ particles with different shapes and polymorphism were obtained. High concentration of the oleic acid gave stable vaterite crystals, the polymorph of which did not change when the composite was kept in water for more than one week. Fourier transform infrared spectroscopy (FT-IR) and TGA analysis of the obtained product indicated that the oleic acid was bound to the crystalline CaCO₃. The contact angle of the modified vaterite reached 122°. We have succeeded in crystallization of hydrophobic CaCO₃ nanoparticles in situ.     

Synthesis of CaCO3 Nanoparticles by Mechanochemical Processing

The synthesis of calcite (CaCO₃) nanoparticles by mechanochemical reaction and subsequent heat treatment was investigated. A solid-state displacement reaction CaCl₂ + Na₂CO₃ CaCO₃+2NaCl was induced during mechanical milling of a CaCl₂+ Na₂CO₃ powder mixture. Heat treatment of the as-milled powder at 350°C completed the reaction, forming crystalline CaCO₃ nanoparticles separated from each other in a dry-salt matrix. A simple washing process to remove the matrix yielded calcite single phase ultrafine powder. The mean particle size was controlled by changing the volume fraction of CaCO₃ in the matrix. 20% volume fraction yielded nanoparticles of ~ 140 nm in size, whereas 10% volume fraction led to ~ 80 nm size nanoparticles.     

In situ preparation of hydrophobic CaCO3 in the presence of sodium oleate

Hydrophobic CaCO₃ particles were directly prepared via carbonation of Ca(OH)₂ slurry in the presence of sodium oleate at room temperature. Sodium oleate was used to modify the surface property of CaCO₃ particles. The measurement of relative contact angle and active ratio indicated that CaCO₃ samples were hydrophobic. DTG, FT-IR and TEM analysis of the obtained product indicated that the hydrophobic property was attributed to the deposition of calcium oleate, produced in the reaction mixture, onto the surface of calcium carbonate particles. They were covered on the CaCO₃ crystals surface and modified their surface property; at the same time they own CC bonds and could be polymerized or copolymerized later to give a polymeric monolayer.     

Nanocomposites Prepared by Solution Blending: Microstructure and Mechanical Properties

Composites of poly(vinyl chloride) (PVC) filled with micron‐ and nanosized calcium carbonate (CaCO₃) particles were prepared by solution blending. The influences of particle size and CaCO₃ content on the microstructure and mechanical properties of the PVC composites were investigated by means of polarized optical microscopy and mechanical testing. The polarized optical microscope images revealed that nanosized CaCO₃ particles were more agglomerated than micron‐sized CaCO₃ particles and the amount of agglomerates increased with increasing particle content. PVC/CaCO₃‐0.22 composites (PVC nanocomposite filled with 220‐nm‐particle‐sized CaCO₃) 5 phr CaCO₃ content had the maximum tensile strength. The Young's modulus of all composites increased with increasing particle content. The energy at break of all composites showed a decreasing trend as a function of CaCO₃ content and varied with particle size.     

Bias field effects on the dielectric properties of 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystals with different orientations

The domain states and phase transitions in 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ single crystals were investigated by studying their relative permittivity under various dc bias at constant heating and cooling rates. The orientation dependence of the bias field effect was revealed by examining the temperature dependence of relative permittivity as a function of crystal orientation (the 〈111〉, 〈011〉 and 〈001〉 directions) and dc bias field. The crystals basically have a macrodomain rhombohedral ferroelectric state in the ferroelectric phase under zero dc bias. External bias field could modulate the domain state and induce a stable macrodomain state in the crystals. Also, it is proposed that the dc bias applied along the 〈001〉 or 〈011〉 direction could induce a tetragonal ferroelectric phase or an orthorhombic ferroelectric phase, respectively, in an intermediate temperature range.