Correlation of nanostructural parameters and macromechanical behaviour of hyperbranched‐modified polypropylene using time‐resolved small‐angle X‐ray scattering measurements

Polypropylene (PP) is modified utilizing a poly(ester amide)‐based hyperbranched polymer (PS). A maleic‐modified PP is used to enhance the compatibility. Usual tensile experiments are carried out. The nanocrystalline structure is studied using small‐angle X‐ray scattering (SAXS) while a uniaxial mechanical load is simultaneously applied. SAXS patterns are analysed using procedures written in PV‐WAVE. The chord distribution function (CDF) is calculated and nanostructural parameters such as long period (l_p) and nanodeformation (?_Nano) are extracted. The correlations between macromechanical parameters and nanostructures are studied. Mechanical results show that PS has a plasticizing effect. Reactively blended samples demonstrate enhanced mechanical properties. SAXS patterns reveal a well‐known structure of PP as a peculiar architecture of the nanostructure. Crystalline branching occurs in a geometry that is known as a mother–daughter crystal lamellar structure, also called a crosshatching structure. It is concluded that adding PS distorts the stacking of crystalline domains. The structural information from SAXS patterns in reciprocal space is visualized in real space in the calculated CDFs. The CDFs indicate that in simple blends, l_p of the crystalline stacks increases compared to blank PP. Nevertheless, reactively blended samples show an increase of l_p compared to blank PP; however, they possess smaller l_p compared to simple blends. © 2012 Society of Chemical Industry     

Crystallization behavior of polypropylene/ethylene butene copolymer blends

One polypropylene (PP) was mixed with two ethylene butene copolymers (EBM). EBM1 had 12.5 mol % of butene and was immiscible with the PP. EBM2 had 51.6 mol % of butene and was miscible with the PP. The dispersed PP in EBM1 showed fractionalized crystallization behavior with a crystallization temperature at around 45°C and a much slower isothermal crystallization rate comparing to the neat PP. The PP did not exhibit fractionalized crystallization behavior in EBM2. EBM1 did not decrease both the crystallization and melting temperatures of the continuous PP. However, EBM2 could decrease both the two temperatures. It was found that EBM2 could largely suppress the epitaxial lamellar branching of the PP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structure and morphology development during deformation of propylene based ethylene-propylene copolymer and its blends with isotactic polypropylene

The structure and morphology development during the deformation of metallocene based ethylene-propylene copolymers with dominant propylene moiety (C3 M-EP) and its isotactic polypropylene (M-iPP) blends were investigated by simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) using synchrotron radiation, high temperature tensile testing and differential scanning calorimetry (DSC). X-ray results showed that the structure and morphology in the blends of M-iPP/C3 M-EP are dictated by the M-iPP component. During stretching at room temperatures, both pure M-iPP and polymer blends exhibited the same transition from the α-form crystal to the mesophase. However, the α-form was found to be unchanged during the deformation of C3 M-EP copolymer, which indicated that the effect of local stress on the crystal domain in pure copolymer was too small to induce the phase transition. Although the DSC results showed that the blends in their isotropic state were immiscible with each other, the mechanical properties of the blends at high temperature (70 °C) indicated that they follow the conventional rule of mixing.     

Dynamic viscoelastic behavior of polypropylene/polybutene-1 blends and its correlation with morphology

In this study the rheology, morphology, and interfacial interaction of polypropylene (PP)/polybutene-1 (PB-1) blends in different percentages of PB-1 are investigated. The morphology of cryo-fractured surfaces of samples was studied by scanning electron microscopy (SEM). The SEM images showed a droplet-matrix structure in all range of compositions and the size of dispersed phase increased proportionally with PB-1 content. The miscibility of blends at various compositions is evaluated by viscoelastic parameters determined by dynamic oscillation rheometry in the linear viscoelastic region. A distinct Newtonian plateau at low frequencies is observed and the variations of complex viscosity (η*) against angular frequency (ω) for all blends are in agreement with Cross model. The complex viscosity of samples at various percentages of PB-1 showed the log-additivity mixing rule behavior in low frequencies and positive-negative deviation behavior (PNDB) at high shear rates. The phenomena such as decrease in the sensitivity of storage modulus to shear rate in the terminal region, the deviation of Cole–Cole plots from the semi-circular shape, and the tail in relaxation spectrums at high relaxation times are the evidences of two phase heterogenous morphology. The effect of time–temperature on the phase behavior is studied and the interfacial tension between matrix and dispersed phase was evaluated by using emulsion theoretical models. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dynamic mechanical properties and morphology of polypropylene/maleated polypropylene blends

The dynamic mechanical properties of both homopolypropylene (PPVC)/Maleated Poly-propylene (PP-g-MA) and ethylene-propylene block copolymer (PPSC)/Maleated Poly-propylene (PP-g-MA) blends have been studied by using a dynamic mechanical thermal analyzer (PL-DMTA MKII) over a wide temperature range, covering a frequency zone from 0.3 to 30 Hz. With increasing content of PP-g-MA, α relaxation of both blends gradually shift to a lower temperature and the apparent activation energy ΔE_α increases. In PPVC/PP-g-MA blends, β relaxation shifts to a higher temperature as the content of PP-g-MA increases from 0 to 20 wt % and then change unobviously for further varying content of PP-g-MA from 20 to 35 wt %. On the contrary, in the PPSC/PP-g-MA blends β₁ relaxation, the apparent activation energy ΔE_β1 and β₂ relaxation are almost unchanged with blend composition, while ΔE_β2 increases with an increase of PP-g-MA content. In the composition range studied, storage modulus É value for PPSC/PP-g-MA blends decreases progressively between β₂ and α relaxation with increasing temperature, but in the region the increment for PPVC/PP-g-MA blends is independent of temperature. The flexural properties of PPVC/PP-g-MA blend show more obvious improvement on PP than one of PPSC/PP-g-MA blends. Scanning electron micrographs of fracture surfaces of the blends clearly demonstrate two-phase morphology, viz. the discrete particles homogeneously disperse in the continous phase, the main difference in the morphology between both blends is that the interaction between the particles and the continuous phase is stronger for for PPVC/PP-g-MA than for PPSC/PP-g-MA blend. By the correlation of the morphology with dynamic and mechanical properties of the blends, the variation of the relaxation behavior and mechanical properties with the componenet structure, blend composition, vibration frequency, and as well as the features observed in these variation are reasonably interpreted. © 1996 John Wiley & Sons, Inc.     

Mechanical properties and morphology of polyethylene–polypropylene blends with controlled thermal history

The effect of time–temperature treatment on the mechanical properties and morphology of polyethylene–polypropylene (PE–PP) blends was studied to establish a relationship among the thermal treatment, morphology, and mechanical properties. The experimental techniques used were polarized optical microscopy with hot‐stage, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and tensile testing. A PP homopolymer was used to blend with various PEs, including high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), linear low‐density polyethylene (LLDPE), and very low density polyethylene (VLDPE). All the blends were made at a ratio of PE:PP = 80:20. Thermal treatment was carried out at temperatures between the crystallization temperatures of PP and PEs to allow PP to crystallize first from the blends. A very diffuse PP spherulite morphology in the PE matrix was formed in partially miscible blends of LLDPE–PP even though PP was present at only 20% by mass. Droplet‐matrix structures were developed in other blends with PP as dispersed domains in a continuous PE matrix. The SEM images displayed a fibrillar structure of PP spherulite in the LLDPE–PP blends and large droplets of PP in the HDPE–PP blend. The DSC results showed that the crystallinity of PP was increased in thermally treated samples. This special time–temperature treatment improved tensile properties for all PE–PP blends by improving the adhesion between PP and PE and increasing the overall crystallinity. In particular, in the LLDPE–PP blends, tensile properties were improved enormously because of a greater increase in the interfacial adhesion induced by the diffuse spherulite and fibrillar structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1151–1164, 2000     

Crystallization behavior and optical and mechanical properties of isotactic polypropylene nucleated with rosin‐based nucleating agents

Background: Rosin‐based nucleating agents, as natural products, do not have any toxicity; hence they could be used in the industrial processing of polypropylene for the manufacture of food containers. As a result they have been the subject of considerable scientific interest in the literature. In this paper, the non‐isothermal crystallization behavior, and optical and mechanical properties of isotactic polypropylene (iPP) nucleated with rosin‐based nucleating agents are reported. Polarized optical microscopy, scanning electron microscopy and wide‐angle X‐ray diffraction were used to investigate the morphology and crystal structure of iPP with different rosin‐based nucleators. The effects of a 1:1:1 co‐crystal on the properties of iPP were also investigated. Results: The addition of rosin‐based nucleating agents led to the following changes in properties: (a) shortened crystallization half time, (b) decreased size of iPP crystals, (c) slightly increased crystallinity and (d) increased transparency, gloss, flexural modulus and tensile strength. The shrinkage of nucleated iPPs was similar to that of the blank iPP. Conclusion: Rosin‐based nucleating agents in iPP were shown to be effective for nucleating crystals, reducing their size and causing preferential growth along the b‐axis, but suppressing detectable spherulites. The 1:1:1 co‐crystal was effective at 0.2 wt%, a greater concentration giving little additional improvement. Copyright © 2007 Society of Chemical Industry     

Crystallization behavior and mechanical properties of polypropylene random copolymer/poly(ethylene‐octene) blends

New polymer blends of polypropylene random copolymer (PP‐R) and poly(ethylene‐octene) (POE) were prepared by melt‐blending process using a corotating twin‐screw extruder. The POE content was varied up to 35%. The toughening efficiency of POE for PP‐R was evaluated by the mechanical properties of the resulted PP‐R/POE blends. The crystallization behavior and morphology of the blends were also studied. Results show that POE acts as nucleation agent to induce the crystallization of PP‐R matrix at higher crystallization temperature. Super‐toughened PP‐R/POE blends (Izod impact strength more than 500 J/m) can be readily achieved with only 10 wt % of POE. The high toughness of PP‐R/POE is attributed to cavitation and shear yielding of matrix PP‐R, as revealed by the morphology studies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dynamic mechanical properties and morphology of polypropylene block copolymers and polypropylene/elastomer blends

The relation between the dynamic mechanical properties and the morphology of polypropylene (PP) block copolymers and polypropylene/elastomer blends was studied by dynamic mechanical analysis (DMA), light- and electron microscopy. The latter techniques contributed to an improvement in assignments of relaxation transitions in the DMA spectra. It was established that PP block copolymers had multiphase structure since the ethylene/propylene rubber phase (EPR) formed in the copolymerization contained polyethylene (PE) domains. An identical morphology was found in the case of PP/polyolefin thermoplastic rubber (TPO) blends. Impact modification of PP by styrene/butadiene block copolymers led to a multiphase structure, too, due to the polystyrene (PS) domains aggregated in the soft rubbery polybutadiene phase. In the semicrystalline polyolefinic and in the amorphous styrene/butadienebased thermoplastic rubbers, PE crystallites and PS do mains acted as nodes of the physical network structure, respectively. PP/EPDM/TPO ternary blends developed for replacing high-density PE showed very high dispersion of the modifiers as compared to that of PP block copolymers. This fine dispersion of the impact modifier is a basic regulating factor of impact energy dissipation in the form of shear yielding and crazing.     

Short jute fiber‐reinforced polypropylene composites: Dynamic mechanical study

Short jute fiber‐reinforced polypropylene (PP) composites were prepared using a high‐speed thermokinetic mixer. A compatibilizer was used to improve the molecular interaction between jute and PP. Both the percent weight fraction of the jute fiber and compatibilizer were varied to study the dynamic mechanical thermal (DMT) properties. Dynamic parameters such as storage flexural modulus (E′), loss flexural modulus (E″), storage shear modulus (G′), loss shear modulus (G″), and loss factor or damping efficiency (tan δ) were determined in a resonant frequency mode. The transition peak nature, amplitude, and temperature of E′, E″, G′, G″, and tan δ of different compositions were shown to indicate possible improvements of molecular interaction in the presence of a compatibilizer. The modulus retention term, a plot of the reduced modulus with the weight fraction of the jute fiber, also indicate its improvement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 531–539, 1999     

Melting,nonisothermal crystallization behavior and morphology of polypropylene/random ethylene—propylene copolymer blends

The melting, nonisothermal crystallization behavior and morphology of blends of polypropylene (PP) with random ethylene–propylene copolymer (PP‐R) were studied by differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X‐ray diffraction. The results showed that PP and PP‐R were very miscible and cocrystallizable. Modified Avrami analysis was used to analyze the nonisothermal crystallization kinetics of the blends. The values of the Avrami exponent indicated that the crystallization nucleation of the blends was heterogeneous, the growth of the spherulites was tridimensional, and the crystallization mechanism of PP was not affected by PP‐R. The crystallization activation energy was estimated using the Kissinger method. An interesting result was obtained with the modified Avrami analysis and the Kissinger method, whose conclusions were in good agreement. The addition of a minor PP‐R phase favored an increase in the overall crystallization rate of PP. Maximum enhancing effect wass found to occur with a PP‐R content of 20 wt %. The relationship between the composition and the morphology of the blends is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 670–678, 2006     

Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk

The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry     

Effect of silane‐grafted polypropylene on the mechanical properties and crystallization behavior of talc/polypropylene composites

Talc‐filled polypropylene (PP) composites coupled with silane‐grafted polypropylene (PP‐g‐Si) were prepared. Effect of PP‐g‐Si on the mechanical properties, crystallization, and melting behavior of PP composites was investigated. Compared with the uncoupled composites, the mechanical properties of Talc/PP composites coupled with a small amount of PP‐g‐Si were increased to some extent. Meanwhile, PP‐g‐Si can promote crystallization rate and increase crystallization temperature of PP in the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2974–2977, 2000     

Shear‐induced fibrillation and resultant mechanical properties of injection‐molded polyamide 1010/isotactic polypropylene blends

It is feasible to control the phase morphology and orientation for immiscible polymer blends to manipulate their properties. In this paper, the blend of polyamide 1010 (PA1010) and isotactic polypropylene (iPP) (mainly at a fixed ratio of PA1010/iPP = 80/20) was used as an example to demonstrate the effect of shear on the morphology and resultant mechanical properties. After being melt blended, the injection‐molded bars were prepared via a dynamic packing equipment to impose a prolonged shearing on the melts during the solidification stage. By controlling the shear time, the structure evolution and morphological development of the blends can be well controlled. Mechanical measurement of the molded bar showed a dramatically improved tensile property and impact strength with increasing shear time. Morphological examination revealed that the iPP droplets are elongated and become thin fibrils along the shear direction with increasing shear time. The shear‐induced fibrillation, instead of orientation, is believed to be responsible for the largely improved properties of the blend, particularly for the impact strength. The toughening mechanism is discussed based on the combined effect of hindrance of crack propagation and the transferring and bearing of the load due to the existence of the fibrils. This was further proved by changing the blending ratio and using low molecular weight iPP. Finally, we propose a concept for designing blending materials with good comprehensive properties. Copyright © 2011 Society of Chemical Industry     

Crystallization behavior and crystallization kinetic studies of isotactic polypropylene modified by long‐chain branching polypropylene

In this article, we discuss the crystallization behavior and crystallization kinetics of isotactic polypropylene (iPP) modified by long‐chain‐branching (LCB) high‐melt‐strength iPP over a wide composition range, that is, LCB‐iPP from 10 to 50 wt %. Over the entire range we investigated, the presence of LCB‐iPP accelerated crystallization in both the isothermal crystallization process and nonisothermal crystallization process, even when the LCB‐iPP content was as low as 10%, and both crystallization processes were enhanced more significantly as the LCB‐iPP content increased. Hoffman–Lauritzen theory analysis revealed that the fold‐free energy decreased effectively with the occurrence of the LCB structure, although the growth rate of spherulites was depressed, as shown by polarized optical microscopy. Meanwhile, the regime III–regime II transition temperature was about 15° higher for all of the LCB‐iPP compositions than that of iPP because the LCB structure reduced the mobility of the polypropylene chains. Furthermore, the γ‐form crystal structure was favored by LCB compared to the β form, which was supported by wide‐angle X‐ray diffraction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal crystallization and melting behavior of β‐nucleated isotactic polypropylene and polyamide 66 blends

A highly novel nano‐CaCO₃ supported β‐nucleating agent was employed to prepare β‐nucleated isotactic polypropylene (iPP) blend with polyamide (PA) 66, β‐nucleated iPP/PA66 blend, as well as its compatibilized version with maleic anhydride grafted PP (PP‐g‐MA), maleic anhydride grafted polyethylene‐octene (POE‐g‐MA), and polyethylene‐vinyl acetate (EVA‐g‐MA), respectively. Nonisothermal crystallization behavior and melting characteristics of β‐nucleated iPP and its blends were investigated by differential scanning calorimeter and wide angle X‐ray diffraction. Experimental results indicated that the crystallization temperature (T) of PP shifts to high temperature in the non‐nucleated PP/PA66 blends because of the α‐nucleating effect of PA66. T of PP and the β‐crystal content (K_β) in β‐nucleated iPP/PA66 blends not only depended on the PA66 content, but also on the compatibilizer type. Addition of PP‐g‐MA and POE‐g‐MA into β‐nucleated iPP/PA66 blends increased the β‐crystal content; however, EVA‐g‐MA is not benefit for the formation of β‐crystal in the compatibilized β‐nucleated iPP/PA66 blend. It can be relative to the different interfacial interactions between PP and compatibilizers. The nonisothermal crystallization kinetics of PP in the blends was evaluated by Mo's method. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Phase transformation and mechanical properties of halloysite nanotubes‐modified isotactic polypropylene filaments

Phase transformation and mechanical properties of isotactic polypropylene (iPP) with well‐distributed 0.3, 0.8, and 1.2 wt % halloysite nanotubes (HNTs) are studied. The spatial distribution of HNTs in the iPP matrix is analyzed using transmission electron microscopy and found to be homogeneously dispersed. Phase transformation from molten to solid states is characterized by polarized optical microscopy under an isothermal condition at different temperatures and differential scanning calorimetric in cooling and heating at different rates. Average size of spherulites, the degree of undercooling and total solidification time of iPP decrease as the amount of HNTs increases, suggesting HNTs act as nucleation sites for iPP. More interestingly, the wide‐angle X‐ray diffraction analysis only showed the formation of the α‐form iPP crystallites for the extruded filament, while kinetics results indicating the existence of β‐form crystals. These results together demonstrated the presence of HNTs leads to heterogeneous phase distribution which enhances the mechanical strength of the iPP filaments without reducing their ability for elongation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44714.     

Comparison of carboxylated and maleated polypropylene as reactive compatibilizers in polypropylene/polyamide‐6,6 blends

Using reactive extrusion, polypropylene is functionalized with maleic anhydride and compared on an equimolar basis to polypropylene that is functionalized with an asymmetric, carboxylic acid containing peroxide. The grafting efficiency for the asymmetric peroxide is double that obtained for the maleic anhydride system. Moreover, the asymmetric peroxide yields a functionalized material with minimal molecular weight degradation and desirable mechanical properties, relative to maleic anhydride‐grafted polypropylene. In compatibilized blends of polypropylene and nylon 6,6, the polypropylene that was functionalized with the asymmetric peroxide is found to be an improved compatibilizer compared to that of maleic anhydride‐grafted polypropylene. The differences in mechanical properties of the two different functionalized polypropylene materials and their respective blends are rationalized on the basis of the grafting efficiency, molecular weight degradation during reactive extrusion, and effect of free functional species on the ability to form graft copolymers in compatibilized blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2398–2407, 2001     

Gas permeability and mechanical properties of polystyrene–polypropylene blends

Permeability to water vapor and oxygen, elastic modulus, tensile strength, and impact strength of polystyrene–polypropylene and high-impact polystyrene–polypropylene blends were determined as functions of blend composition and morphology. Three types of styrene–butadiene block copolymers were tested as compatibilizers and found to improve mechanical properties of blends. The experimental data on permeability and modulus were compared with the predictions for the studied binary and ternary blends. The predictive scheme employs a two-parameter equivalent box model and the data on phase continuity of constituents calculated using general equations derived from percolation theory. Blends with decreased permeability and plausible mechanical properties were proposed with regard to intended applications in food packaging. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2615–2623, 1998