Light‐scattering capacity of ethylene–vinyl acetate copolymers in polypropylene: Toward high haze and transmittance

Light‐scattering materials were fabricated by the melt blending of polypropylene with an ethylene–vinyl acetate copolymer (EVA) to prevent the glare effect of light‐emitting diodes. The results show that the light‐scattering capacity was remarkably dependent on the phase morphologies of EVA. (1) When EVA was dispersed as spherical droplets, the transmittance and haze gradually increased with the enrichment of EVA, and the half‐peak width of the light‐scattering pattern reached a maximum when 30 wt % EVA was loaded. On the basis of the analysis of Mie scattering theory, the enlargement of scattering particles promoted light transmittance, and more incoming light was deflected at the arclike interfaces. This induced a distinct antiglare effect. (2) When scattering particles deformed and expanded vertically in the light‐transmitting direction, the light‐scattering capacity turned out to be weakened by further enrichment of the EVA phase. The planelike interfaces reduced the deflection of incoming light, and this led to decreases in the scattering angles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42844.     

Role of crystalline ethylene‐propylene copolymer on mechanical properties of impact polypropylene copolymer

Impact polypropylene copolymer (IPC) has been known as a multiphase material in which an ethylene‐propylene (EP) random copolymer, serves as toughening component, is dispersed in the homo‐polypropylene hPP matrix. The crystalline EP copolymer (cEP) is another component whose role and microstructural effect on the IPC properties has not been well understood. This work reveals the relationship between the microstructure of cEP and the mechanical properties, that is, impact and tensile resistance, of IPC. We clarify that IPC comprising high contents of cEP with long homo‐PP segment can extend the elongation at break while cEP with high content of homo‐PE segment contributes to high impact strength. Mechanisms for both of these processes have been proposed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rheological,mechanical, thermal,and morphological properties of polypropylene/ethylene‐octene copolymer blends

Rheological and morphological studies were performed on polymer blends of ethylene‐octene copolymer [polyethylene elastomer (PEE)] and polypropylene (PP). The viscosities of PEE, PP, and PEE/PP blends were analyzed using an Instron capillary rheometer and a Rheometrics Dynamic Stress Rheometer, SR 200. A non‐Newtonian flow behavior was observed in all samples in the shear rate range from 27 to 2700 s⁻¹, whereas at shear rates in the range from 0.01 to 0.04 s⁻¹, a Newtonian flow behavior was verified. The scanning electron micrographs showed that dual‐phase continuity may occur between 50 and 60 (wt %) of PEE. This result is consistent with the Sperling's model. The mechanical analysis showed that PEE/PP, with 5 wt % of PEE, presented an increase on the mechanical properties and as the PEE content increased, a negative deviation in relation to an empirical equation was observed. Thermal analysis showed that there were no change in the crystallization behavior of the matrix when different elastomer contents were added. Dynamic mechanical thermal analysis showed that samples with low PEE contents presented only one peak, indicating a certain degree of miscibility between the components of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 692–704, 2000     

Preparation and characterization of high MFR polypropylene and polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloys

In this work, high melt flow rate (MFR) polypropylene (HF‐PP) and polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloys (HF‐PP/EPR) with MFR ≈ 30 g/10 min were synthesized by spherical MgCl₂‐supported Ziegler–Natta catalyst with cyclohexylmethyldimethoxysilane (CHMDMS) or dicyclopentyldimethoxysilane (DCPDMS) as external donor (De). The effects of De on polymerization activity, chain structure, mechanical properties, and phase morphology of HF‐PP and HF‐PP/EPR were studied. Adding CHMDMS caused more sensitive change of the polymers MFR with H₂ than DCPDMS, and produced PP/EPR alloys containing more random ethylene‐propylene copolymer (r‐EP) and segmented ethylene‐propylene copolymer (s‐EP). CHMDMS also caused formation of s‐EP with higher level of blockiness than DCPDMS. HF‐PP/EPR alloy prepared in the presence of DCPDMS exhibited higher flexural properties but lower impact strength than that prepared with CHMDMS. Toughening efficiency of the rubber phase was nearly the same in the alloys prepared using CHMDMS or DCPDMS as De, but stiffness of the alloy can be improved by using DCPDMS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42984.     

Polypropylene/polypropylene‐grafted acrylic acid copolymer/ethylene–Acrylic acid copolymer ternary blends for hydrophilic polypropylene

Ternary blends of polypropylene (PP), a polypropylene‐grafted acrylic acid copolymer (PP‐g‐AA), and an ethylene–acrylic acid copolymer (EAA) were prepared by melt blending. The surfaces of films with different contents of these three components were characterized with contact‐angle measurements. Scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis were used to characterize the microstructure, melting and crystalline behavior, and thermal stability of the blends. The contact angles of the PP/PP‐g‐AA blends decreased monotonically with increasing PP‐g‐AA content. With the incorporation of EAA, the contact angles of the PP/PP‐g‐AA/EAA ternary blends decreased with increasing EAA content. When the concentration of EAA was higher than 15 wt %, the contact angles of the ternary blends began to increase. Scanning electron microscopy observations confirmed that PP‐g‐AA acted as a compatibilizer and improved the compatibility between PP and EAA in the ternary blends. Differential scanning calorimetry analysis suggested that acrylic acid moieties could act as nucleating agents for PP in the polymer blends. Thermogravimetric analysis and differential thermogravimetry confirmed the optimal blend ratio for the PP/PP‐g‐AA/EAA ternary blends was 70/15/15. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 436–442, 2006     

Interfacial influence on mechanical properties of polypropylene/polypropylene‐grafted silica nanocomposites

Three types of polypropylene‐grafted silica (PGS‐2 K, PGS‐8 K and PGS‐30 K) with different grafting chain lengths were prepared. After melt‐blending PGS with polypropylene (PP), we studied the PP/PGS interface properties and the influence of PP/PGS interfaces on mechanical properties of nanocomposites. The strong matrix/particle interface was observed in PP/PGS‐30 K nanocomposites with 5 wt % particle loading as evidenced by 2.5 °C increased glass transition temperature (T_g) compared with neat PP, whereas the weak matrix/particle interface was observed in PP/PGS‐2 K nanocomposites with decreased T_g. The variations in the matrix/particle interfacial strength lead to a transition in the yield stress of nanocomposites. Compared with the unfilled PP, the yield stress of the PP/PGS‐2 K nanocomposites is decreased by 0.7 MPa, and the yield stress of the PP/PGS‐30 K nanocomposites is enhanced by 1.4 MPa. In addition, benefiting from good dispersion, the PP/PGS‐masterbatch nanocomposites with a strong matrix/particle interface not only exhibit increased Young's modulus and yield stress, but also the strain at break remains in line with the unfilled PP, which is in contrast to the conventional wisdom that the gain in modulus and strength must be at the expense of the decreased break strain. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45887.     

Characteristics of diether‐ and phthalate‐based Ziegler‐Natta catalysts for copolymerization of propylene and ethylene and terpolymerization of propylene,ethylene, and 1‐butene

Copolymerization of propylene and ethylene and terpolymerization of propylene, ethylene, and 1‐butene were carried out to compare the characteristics of diether‐ and phthalate‐based Ziegler‐Natta catalysts in a reaction system of pilot scale. The ethylene incorporation with the diether‐based catalyst was higher but the 1‐butene incorporation was lower compared with those of the phthalate‐based catalyst. In the case of copolymers from the diether‐based catalyst, melting behavior, determined through differential scanning calorimetry (DSC), showed a distinct shoulder peak and lots of nuclei were formed during crystallization. The diether‐based catalyst led to polymers having blockier ethylene sequences compared with those of the phthalate‐based catalyst; the highly crystallizable fraction (HIS) containing blockier ethylene sequences was produced with the diether‐based catalyst. These results seem to be the result of regio‐irregular characteristics of the diether‐based catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 851‐859, 2013     

Compatibilization of a polyolefin blend through covalent and ionic coupling of grafted polypropylene and polyethylene. I. Rheological,thermal, and mechanical properties

A polypropylene/high‐density polyethylene blend containing 70 wt % polypropylene was prepared and compatibilized via the addition of maleic anhydride grafted polypropylene and polyethylene. The functionalized polymer chains were coupled with two types of coupling agents. Dodecane diamine formed covalent bonds with the maleic anhydride, whereas two metallic salts, zinc acetate and sodium hydrogenocarbonate, formed ionic interactions with the carboxylic functions produced by the hydration of the anhydride cycle. The coupling of the grafted polyolefin chains was successfully realized by a single operation in a twin‐screw extruder. The coupling agents were efficient in improving the elongation at break and impact properties of the studied blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 312–320, 2005     

Zeolite A‐polypropylene and silver‐zeolite A‐polypropylene composite films for antibacterial and breathable applications

Polypropylene (PP) composite films were successfully prepared using melt blending by directly mixing PP pellets with zeolite A or silver‐zeolite A powder and then blowing. All the prepared films were characterized in terms of their physical, mechanical, optical, and gas permeability properties. The structure of each composite film was similar to that of the pure PP film. The crystallinity and glossy quality of the composite films were increased by the addition of silver, zeolite, and maleic anhydride grafted PP (PP‐g ‐MA). The composite PP film with zeolite A and PP‐g ‐MA exhibited a level of oxygen and carbon dioxide permeation (6438 and 15,087 cc m^?2 day^?1 atm^?1, respectively). Finally, all the films were evaluated for their antibacterial activity and fruit packaging applications. Silver‐zeolite A‐PP composite films exhibited a bactericidal activity of 79% against Staphylococcus aureus and 52% against Escherichia coli , while the zeolite A‐PP film could extend the shelf‐life of bananas for over a week. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45450.     

Morphology and thermal properties of maleic anhydride grafted polypropylene/ethylene–vinyl acetate copolymer/wood powder blend composites

Maleic anhydride grafted polypropylene (MAPP) was blended with ethylene–vinyl acetate (EVA) copolymer to form MAPP/EVA polymer blends. Wood powder (WP) was mixed into these blends at different weight fractions to form MAPP/EVA/WP blend composites. Differential scanning calorimetry (DSC) analysis of the blends showed small melting peaks between those of EVA and MAPP, which indicated interaction and cocrystallization of fractions of EVA and MAPP. The presence of MAPP influenced the EVA crystallization behavior, whereas the MAPP crystallization was not affected by the presence of EVA. Scanning electron microscopy, Fourier transform infrared spectroscopy, and DSC results show that the WP particles in the MAPP/EVA blend were in contact with both the MAPP and EVA phases and that there seemed to be chemical interaction between the different functional groups. This influenced the crystallization behavior, especially of the MAPP phase. The thermogravimetric analysis results show that the MAPP/EVA blend had two degradation steps. An increase in the WP content in the blend composite led to an increase in the onset of the second degradation step but a decrease in onset of the first degradation step. The presence of WP in the blend led to an increase in the modulus but had almost no influence on the tensile strength of the blend. The dynamic mechanical analysis results confirm the interaction between EVA and MAPP and show that the presence of WP only slightly influenced the dynamic mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Determination of the minimum sample size for a reliable strength measurement of talc‐filled polypropylene fibers

Accurate determination of mechanical properties plays an important role to comment on improvement in the mechanical properties of particle‐filled PP fibers. However, the existing standards are not totally suitable for reliable strength determination of particle‐filled PP fibers. In the framework of this study, microsized talc particle‐filled PP fibers were produced with different talc ratio and tensile strength measurements were performed with various gage lengths. Statistical Akaike Information Criterion analysis shows that strength distribution of talc‐filled PP fibers is best characterized by Weibull distribution function. It is reported that, the gage length has almost no influence of Weibull parameters of pure PP fibers while strong effects on Weibull parameters of talc‐filled PP fibers. It is shown that if the tensile strength of talc‐filled PP fibers is to be measured, at least 50 samples, which is more than value suggested by existing standard, should be used for a reliable determination of Weibull parameters. Therefore, the main aim of this study is to question the feasibility of minimum sample size suggested by the existing ASTM D3822 standard for reliable strength measurement of talc filled PP fibers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44083.     

Using Raman spectroscopic imaging for non‐destructive analysis of filler distribution in chalk filled polypropylene

A feasibility study on using Raman spectral imaging for visualization and analysis of filler distribution in chalk filled polypropylene samples has been carried out. The spectral images were acquired using a Raman spectrometer with 785 nm light source. Eight injection‐molded samples with concentration of chalk 25% and 50% were used in the experiment. Two methods for spectral unmixing were applied to the images and both revealed almost identical distribution maps over the samples’ surface. The maps also correlated with the ones obtained for several separated peaks, typical for the chalk and the polypropylene. The revealed distribution patterns show the same trend for each concentration level and agree with theoretical explanation of plastic flow into an injection molding tool. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43016.     

Melt‐state miscibility of poly(ethylene‐co‐1‐octene) and linear polyethylene

On purpose to examine the effect of branch length on the miscibility of polyolefin blends, miscibility behavior of linear polyethylene/poly(ethylene‐co‐1‐octene) blend was studied and compared to that of linear polyethylene/poly(ethylene‐co‐1‐butene) blend. Miscibility of the blend was determined by observing the morphology quenched from the melt, and by using the relation between interaction parameter and copolymer composition. When the weight composition and molecular weight was the same, poly(ethylene‐co‐1‐octene) was slightly more miscible with linear polyethylene than poly(ethylene‐co‐1‐butene) was. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Relationship between branch length and the compatibilizing effect of polypropylene‐g‐polystyrene graft copolymer on polypropylene/polystyrene blends

Three polypropylene‐g‐polystyrene (PP‐g‐PS) graft copolymers with the same branch density but different branch lengths were evaluated as compatibilizing agents for PP/PS blends. The morphological and rheological results revealed that the addition of PP‐g‐PS graft copolymers significantly reduced the PS particle size and enhanced the interfacial adhesion between PP and PS phases. Furthermore, it is verified that the branch length of PP‐g‐PS graft copolymer had opposite effects on its compatibilizing effect: on one hand, increasing the branch length could improve the compatibilizing effect of graft copolymer on PP/PS blends, demonstrated by the reduction of PS particle size and the enhancement of interfacial adhesion; on the other hand, increasing the branch length would increase the melt viscosity of PP‐g‐PS graft copolymer, which prevented it from migrating effectively to the interface of blend components. Additionally, the crystallization and melting behaviors of PP and PP/PS blends were compared. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40126.     

Correlation between the fracture toughness and β‐crystal fraction in a β‐nucleated propylene‐based propylene–ethylene random copolymer

Propylene‐based propylene–ethylene random copolymer (PPR) has been widely used in the production of hot‐water pipes. To further improve its toughness and thermal resistance, β‐nucleating agents (β‐NAs) are frequently incorporated. In this study, PPR containing 5.6 mol % ethylene units was modified by two kinds of β‐NAs, that is, calcium pimelate and N,N′‐dicyclohexylterephthalamide. The notched Izod impact strength of PPR increased with the addition of the β‐NAs. Drastically different toughening effects were found between the two β‐NAs. The structure of PPR with and without a β‐NA was investigated by calorimetry, X‐ray diffraction, and thermomechanical analysis. The results indicated that the relative fraction of β crystals (k_β) in the injection‐molded specimens was determined by the type and content of β‐NA. The relationship between k_β and the impact toughness was summarized. A critical value for k_β (0.68) was identified for the brittle–ductile transition of PPR. PPR with β‐NA having a k_β greater than 0.68 displayed a higher impact strength than the other mixtures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42930.     

Dynamic‐mechanical and thermal characterization of polypropylene/ethylene–octene copolymer blend

Polypropylene/Ethylene–Octene copolymer (PP/EOC) blends were prepared by melt blending technique followed by compression molding. The effect of addition of EOC on the mechanical behavior of the PP matrix was investigated. Tensile and flexural strengths decreased with the incorporation of EOC. However, the impact strength of the matrix polymer increased in all the blend systems. The blends prepared at 30% EOC content showed an increase in the impact strength to the tune of 380% as compared with polypropylene (PP) matrix. The morphology of the fractured surfaces was investigated employing Scanning Electron Microscopy. SEM micrographs depicted the formation of biphase structure, wherein the EOC phases were homogeneously dispersed as small droplets within the PP matrix. WAXD patterns revealed that the α monoclinic form of isotactic PP does not show any significant change with the incorporation of EOC up to 70 wt %. DSC thermograms revealed a decrease in the melting temperature of the virgin matrix with the addition of EOC. The blend system at 50% EOC exhibited a broad crystallization exotherm at 75°C thus indicating multiple crystallization behavior primarily attributed to the difference in the nucleation process. Further DMA analysis showed presence of two different relaxation peaks corresponding to the T_g of EOC and PP matrix respectively, confirming the formation of a biphase structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A novel combination of sandwich and co‐continuous structure based on polypropylene and styrene‐butadiene‐styrene block copolymer formed with wide range of polypropylene content

The styrene–butadiene–styrene block copolymer (SBS)/polypropylene (PP) blends with a unique sandwich layered co‐continuous structure were prepared by melt compounding. Differing from single conventional co‐continuous and sandwich structure, this structure was formed, where pure PP and co‐continuous SBS/PP phase acting as the face sheets and core. Even though the volume content was 20 or 10 vol %, PP always amazingly formed a continuous phase in SBS/PP blends, whereas the morphology of SBS phase relatively changed from dispersed particles to continuous network as its content increased to 50 vol %. For immiscible SBS/PP blends, due to the huge difference of complex viscosity and surface tension between SBS and PP, a pure PP layer existed on the surface of blends which can be ascribed to the PP enrichment. Herein, the structure of blends with more than 50 vol % SBS was presented as sandwich layered co‐continuous structure by combining the pure PP layer and co‐continuous structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46580.     

Rheological and thermal properties of polypropylene blends based in a low molecular weight EVA

Blends of polypropylene (PP) and poly(ethylene-co-vinyl acetate) (EVA) having a PP/EVA viscosity ratio of 240 were prepared by melt mixing. EVA concentration varies from 2 to 26 wt%. All blends display two-phase structure with quasi-spherical EVA domains evenly distributed in the PP matrix. The diameter of the domains increases with EVA concentration from about 0.4 to 6 μm. Each component crystallizes separately. The melting temperature of PP phase is no noticeably affected by the presence of EVA while the crystallization one gradually increases by 4°C. The dynamic moduli of the blends are well predicted by the emulsion model of Palierne, revealing that the system PP/EVA has a very small interfacial tension. The thermal degradation behavior of the blends, determined by thermogravimetry, shows that the deacylation process in EVA is not affected by the presence of PP while the beginning of the degradation process of PP is increased by up to 20°C due to the presence of EVA. This effect goes along with an increment in the maximum degradation rate of PP.     

Rheological and thermal properties of binary blends of polypropylene and poly(ethylene‐CO‐1‐octene)

Dynamic viscoelastic properties of binary blends consisting of an isotactic polypropylene (i‐PP) and ethylene‐1‐octene copolymer (PEE) were investigated to reveal the relation between miscibility in the molten state and the morphology in the solid state. In this study, PEE with 24 wt % of 1‐octene was employed. The PEE/PP blend with high PEE contents showed two separate glass‐relaxation processes associated with those of the pure components. These findings indicate that the blend presents a two‐phase morphology in the solid state as well as in the molten state. The PEE/PP blend with low PEE content showed a single glass‐relaxation process, indicating that PEE molecules were probably incorporated in the amorphous region of i‐PP in the solid state. The DMTA analysis showed that the blends with low PEE contents presented only one dispersion peak, indicating a certain degree of miscibility between the components of these blends. These results are in accordance with the results of the rheological analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1634–1639, 2001     

Control of rotation extrusion over shish‐kebab crystal alignment in polyethylene pipe and its effect on the pipe's crack resistance

A self‐designed rotation extrusion system was adopted to extrude polyethylene (PE) pipe. The experimental results showed that when the mandrel and die rotated in the same directions during the PE pipe extrusion, apart from the axial stress, all polymer melts in PE pipes were also subjected to the hoop stress so that the formed shish‐kebab crystal in the whole pipe deviated from the axial direction greatly, which was further fixed by the double cooling on both inner and outer walls. As a result, the PE pipe with better resistance to slow crack growth was prepared. As compared to the PE pipe produced by the convention extrusion, the crack initiation time of the PE pipe manufactured by the novel method increased from 27 to 174 h, by 544%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013