Morphology and mechanical properties of blends of thermoplastic polyurethane and polyolefins

Polyolefins (PO) were melt mixed with thermoplastic polyurethane (TPU) in a 20 : 80 weight ratio with or without compatibilizer containing 0.5 wt % of maleic anhydride. Effects of component viscosities on morphology and on mechanical properties of the blend were studied by scanning electron microscope (SEM), tensile property analysis, and dynamic mechanical analysis (DMA). It was found that the disperse particle size of compatibilizer‐free blends decreased with the decreasing viscosity ratio of the disperse phase to TPU. The efficiency of the compatibilizer in reducing the particle size varied with viscosity ratios of the disperse phase to compatibilizer. However, the particle size did not decrease with the decreasing viscosity ratio monotonically. With lower viscosity ratio, addition of 5 wt % compatibilizer resulted in a greater reduction of particle size and less loss in the tensile properties as compared to the TPU matrix. For the polyethene (PE) that has the lowest viscosity value among all the POs, its size in the blend was stabilized with the addition of compatibilizer and no compatibilization was detected by DMA and by tensile property analysis. The mobility of the disperse phase and compatibilizer and the dispersion competition between them seemed important. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 875–883, 2006     

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     

Toughening of syndiotactic polypropylene with chalk

We hypothesized that polymer crystal anisotropy is advantageous for toughening of polymer composites involving easy slip network of oriented crystalline layers around filler particles. To this end, composites of syndiotactic polypropylene (sPP) with high concentration of submicrometer calcium carbonate particles were prepared and examined because usual sPP crystals exhibit high packing anisotropy. The specific orientation of sPP lamellae around chalk grains was found, which is supposed to facilitate the plastic deformation of polymer matrices. The compression molded bars of the composite exhibited markedly higher Izod impact strength than those of neat sPP. Toughening was even enhanced in the injection molded composite, for which 4.5‐fold increase in the impact strength was achieved. Injection‐induced orientation of the disordered form I sPP crystals was enhanced in the composite. The injection molded tensile specimens exhibited also a good drawability. Debonding at chalk–sPP interface occurred both during the impact and tensile tests facilitating the plastic deformation of sPP matrix. Chalk did not have any significant influence on the thermal properties of the composites but it affected the rheological behavior, increasing the loss and storage moduli, and the viscosity. Highly filled sPP composite exhibited solid‐like behavior in a molten state with the storage modulus exceeding the loss modulus in the entire frequency range. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43651.     

Engineering properties of compatibilized polypropylene/liquid crystalline polymer blends

Polypropylene (PP) and Vectra A950, a thermotropic liquid crystalline polymer (LCP), blends were prepared in a single‐screw extruder with the variation in Vectra A950 content in presence of fixed amount (2%, with respect to PP and LCP mixture as a whole) of ethylene‐acrylic acid (EAA) copolymer as a compatibilizer. Mechanical analysis of the compatibilized blends within the range of LCP incorporations under study (2–10%) indicated pronounced improvement in the moduli, ultimate tensile strength (UTS), and hardness. Fourier transform infrared (FTIR) spectroscopy studies revealed the presence of strong interaction through H‐bonding between the segments of Vectra A950 and the compatibilizer EAA. Morphological studies performed by scanning electron microscopy (SEM) manifested the development of fine fibrillar morphology in the compatibilized PP/Vectra A950 blends, which had large influence on the mechanical properties. Differential scanning calorimetry studies showed an initial drop of the melting point of PP in the presence of EAA followed by enhancement of the same in presence of Vectra A950. TGA showed an increase in the thermal stability for all blends with respect to matrix polymer PP. Rheological studies showed that a very small quantity of Vectra A 950 was capable of reducing the melt viscosity of PP particularly in the lower shear rate region and hence facilitated processibility of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallization,mechanical, and fracture behavior of mullite fiber‐reinforced polypropylene nanocomposites

This study describes the reinforcement effect of surface modified mullite fibers on the crystallization, thermal stability, and mechanical properties of polypropylene (PP). The nanocomposites were developed using polypropylene‐grafted‐maleic anhydride (PP‐g‐MA) as compatibilizer with different weight ratios (0.5, 1.0, 1.5, 2.5, 5.0, and 10.0 wt %) of amine functionalized mullite fibers (AMUF) via solution blending method. Chemical grafting of AMUF with PP‐g‐MA resulted in enhanced filler dispersion in the polymer as well as effective filler‐polymer interactions. The dispersion of nanofiller in the polymer matrix was identified using scanning electron microscopy (SEM) elemental mapping and transmission electron microscopy (TEM) analysis. AMUF increased the Young's modulus of PP in the nanocomposites up to a 5 wt % filler content, however, at 10 wt % loading, a decrease in the modulus resulted due to agglomeration of AMUF. The impact strength of PP increased simultaneously with the modulus as a function of AMUF content (up to 5 wt %). The mechanical properties of PP‐AMUF nanocomposites exhibited improved thermal performance as compared to pure PP matrix, thus, confirming the overall potential of the generated composites for a variety of structural applications. The mechanical properties of 5 wt % of AMUF filled PP nanocomposite were also compared with PP nanocomposites generated with unmodified MUF and the results confirmed superior mechanical properties on incorporation of modified filler. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43725.     

Interfacial interaction,morphology, and tensile properties of a composite of highly crystalline cellulose and maleated polypropylene

A composite of highly crystalline cellulose was synthesized via a melt‐mixing method with maleic anhydride (MA)‐grafted polypropylene (PP), MAPP, which was prepared by melt‐mixing PP with 0.25–8.0 phr (part of reagent per hundred parts of PP) of MA, and the morphology and tensile properties were examined with respect to the interfacial interactions of MAPP and cellulose. The graft degree (G_d) of MAPP increases with an increase in the initial MA amount up to 2.5 phr, beyond which it decreases because of the remaining of more free MA monomers and/or the formation of more oligomers remaining in the matrix. The morphology and tensile properties of the composite are affected strongly by G_d as well as the presence of the free MA in the matrix. For the MAPP without any free MA, even the G_d value as small as 0.25–0.5 wt % yields a maximal tensile strength. The existence of free MA monomers in the MAPP decreases the tensile strength, probably because of interrupting the interactions of the grafted MA groups with the OH groups of cellulose. The tensile properties of the composite correlate with the interfacial adhesion as well as the dispersion of cellulose microfibers in the matrix, both of which are determined by the interactions of the OH groups on cellulose with the grafted MA groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3830–3841, 2006     

A highly efficient β‐nucleating agent for impact‐resistant polypropylene copolymer

In this work, we reported calcium tetrahydrophthalate as a high efficient β‐nucleating agent (β‐NA) for impact‐resistant polypropylene copolymer (IPC). The relative fraction of the β‐crystal can reach as high as 93.5% when only 0.03% β‐NA is added. The non‐isothermal and isothermal crystallization behaviors, morphology, lamellar structure and mechanical properties of IPCs with various β‐NA contents were studied. During non‐isothermal crystallization, the cooling rate has an important influence on the relative fraction of the β‐crystal, which decreases remarkably as the cooling rate increases. The β‐NA also greatly accelerates crystallization rate of IPC, resulting from both more crystal nuclei and larger Avrami exponent. The small angle X‐ray scattering characterization shows that more amorphous components are included into the inter‐lamellae after addition of β‐NA. Dynamical mechanical analysis (DMA) reveals that the storage modulus at low temperature and the loss factor above 0 °C from the PP component can be enhanced upon addition of β‐NA and reach a maximum at the β‐NA content of 0.05 wt %. Impact test shows that the impact strength of the IPC at 0°C can be improved as much as 40% when the content of calcium tetrahydrophthalate is 0.10 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40753.     

Syndiotactic polypropylene/microfibrous cellulose composites: Effect of filler size on tensile properties

Syndiotactic polypropylene (SPP)/ethanol swelled microfibrous cellulose (MFC) composite was prepared by a melting mixer, and its morphology and tensile properties were studied. The scanning electron microscope microphotograph did not show the aggregated MFC part up to the 40 wt % MFC loading content, and the Young's modulus was exponentially increasing with the increase of the MFC loading content. These results suggested that the MFC was well‐dispersed in the SPP matrix by an ethanol surfactant work. The Young's modulus was much higher than that of the composite with commonly used fibrous cellulose and moreover, exceeded the theoretical one obtained from the Halpin‐Tsai equation. The differential scanning calorimetry and wide‐angle X‐ray diffraction measurements showed that the MFC acted as a good α‐nucleation agent for SPP. It was found that the excessive Young's modulus of the MFC composite was originated from an increase of that of the SPP matrix induced by the α‐nucleation effect. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of clay type and polymer matrix on microstructure and tensile properties of PLA/LLDPE/clay nanocomposites

Polylactide (PLA)/linear low‐density polyethylene (LLDPE), (PLA/LLDPE), blends and nanocomposites were prepared by melt mixing process with a view to fine tune the properties. Two different commercial‐grade nanoclays, Cloisite® 30B (30B) and Cloisite® 15A (15A) were used. A terpolymer of ethylene, butylacrylate (BA) and glycidylmethacrylate (GMA) was used as a reactive compatibilizer. The influence of type of clay on the morphology and mechanical properties of two PLA‐rich and LLDPE‐rich blend systems was studied. Morphological analysis using X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy revealed that the organoclay layers were dispersed largely at the interface of PLA/LLDPE. Decreasing the PLA content changed the morphology from droplet‐in matrix to coarse co‐continuous. In comparison with 30B, due to less affinity of 15A towards compatibilizer and PLA phase, the reduction of the size of dispersed phase was less than that of the equivalent 30B composites. The mechanical results demonstrated that the composites containing both types of organoclay exhibited higher modulus but lower elongation and tensile strength as compared to the neat blends. The injection molded nanocomposites were shown to have the sequential fracture behavior during tensile test. The tensile testing results on the neat blends and nanocomposites showed significant increase in elongation at break and decrease in the modulus as compared with the neat PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 749‐758, 2013     

A highly active and selective β‐nucleating agent for isotactic polypropylene and crystallization behavior of β‐nucleated isotactic polypropylene under rapid cooling

Zinc adipate (Adi‐Zn) was observed to be a highly active and selective β‐nucleating agent for isotactic polypropylene (iPP). The effects of Adi‐Zn on the mechanical properties and the β‐crystals content of nucleated iPP were investigated. The impact strength of iPP nucleated with 0.2 wt % Adi‐Zn was 1.8 times higher than that of neat iPP. In addition, wide‐angle X‐ray diffraction analysis indicated that the content of β‐crystals in nucleated iPP (k_β value) reached 0.973 with 0.1 wt % Adi‐Zn, indicating that Adi‐Zn is a highly active and selective β‐nucleating agent for iPP. Furthermore, fast scanning chip calorimetry (FSC) studies using cooling rates from 60 to 13,800 °C min^?1 revealed that the formation of β‐crystals significantly depended on the cooling rates. At cooling rates below 3000 °C min^?1, only β‐crystals existed. However, at cooling rates above 6000 °C min^?1, β‐crystals failed to form. Moreover, a lower critical crystallization temperature that corresponded to the generation of β‐crystals was investigated using cooling‐induced crystallization, and the results are in good agreement with those of a previous study. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43767.     

Morphology and mechanical properties of polypropylene and poly(ethylene‐co‐methyl acrylate) blends

The morphology and mechanical properties of isotactic polypropylene (iPP) and poly(ethylene‐co‐methyl acrylate) (EMA) blends were investigated. Various EMA copolymers with different methyl acrylate (MA) comonomer content were used. iPP and EMA formed immiscible blends over the composition range studied. The crystallization and melting reflected that of the individual components and the crystallinity was not greatly affected. The size of the iPP crystals was larger in the blends than those of pure iPP, indicating that EMA may have reduced the nucleation density of the iPP; however, the growth rate of the iPP crystals was found to remain constant. The tensile elongation at break was greatly increased by the presence of EMA, although the modulus remained approximately constant until the EMA composition was greater than 20%. EMA with a 9.0% MA content provided the optimum effect on the mechanical properties of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 175–185, 2003     

Structure and properties of polypropylene/high‐density polyethylene blends by solid equal channel angular extrusion

The solid equal channel angular extrusion (ECAE) process on polypropylene (PP)/high‐density polyethylene (HDPE) blends was carried out. Scanning electron microscopy (SEM) was used to observe the sample structures. Results showed that ECAE process could make PP/HDPE blends to produce orientation structure. Impact performance of ECAE‐PP/HDPE samples after ECAE process improved remarkably, especially for ECAE‐PP/HDPE (90/10)‐O whose impact strength reached 91.91 kJ/m², 18.1 times higher than that of pure PP and 11.2 times higher than that of PP/HDPE (90/10). The mechanism of enhancing between HDPE and PP was discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39759.     

Polytriazoles based on alkyne terminated polybutadiene with and without urethane segments: Morphology and properties

Alkyne terminated polybutadiene with urethane segments (PUPB), a well‐controlled macromolecule, is synthesized with a two‐step routine and characterized by ¹H NMR, IR spectroscopy as well as gel permeation chromatograph. Alkyne terminated polybutadiene without urethane segments (PTPB) is also synthesized and characterized. The two alkyne terminated polybutadiene are cured to generate corresponding polytriazoles. It is found that the mechanical properties of PUPB based polytriazoles are superior to that of PTPB. The fractured surfaces of PTPB based polytriazoles exhibit smooth microstructures whereas PUPB based polytriazoles show the rough microstructures. The atomic force microscopy images reveal well‐established microphase‐separated morphology in polytriazoles with the promotion of urethane segments. Thus, the strong hydrogen bonding interaction existed in urethane has a remarkable effect on the morphology and then the mechanical properties of the as‐prepared polytriazoles. In addition, dioctyl sebacate can serve as an excellent plasticizer to PUPB based polytriazoles, lowering the glass transition temperature (T_g) and improving the ductility. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45178.     

Morphology and properties of isotactic polypropylene modified with hydrocarbon resin MBG273. I. Binary blends

We investigated a system formed of isotactic polypropylene (iPP) and hydrogenated hydrocarbon resin MBG273 (up to 30 wt % resin) to study the influence of the composition on the morphology, structure, and properties of its blends and derived films. All the blends, after the mixing of the components in the melt and cooling at room temperature, were formed by a crystalline phase of iPP and by one homogeneous phase formed by amorphous iPP and the MBG273 resin. The presence of MBG273 did not influence the crystalline structure of iPP, which remained, for every blend, α‐monoclinic, but it reduced the crystallization temperature and nucleation density of iPP. Differential scanning calorimetry and dynamic mechanical thermal analysis showed an increase in the glass‐transition temperature with the resin content, confirming the formation of one amorphous phase. Tensile property analysis indicated an increase in Young's modulus and a decrease in the elongation at break of films as a function of the resin content in the blends. The water vapor permeability and tensile mechanical properties were related to an increase in the glass transition with the addition of MBG273. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3454–3465, 2004     

Structure and tensile properties change of LDPE/UHMWPE blends via solid state shear milling

LDPE/ultrahigh molecular weight polyethylene (UHMWPE) blends were prepared through a pan‐milling reactor in solid state at ambient temperature. The changes of structure and properties of LDPE/UHMWPE blends were investigated by melt flow index, mechanical properties, scanning electronic microscope (SEM), differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction. SEM photos showed that after pan‐milling treatment the dispersed approximately equiaxed UHMWPE particle became rodlike. DSC measurement illustrated that after pan‐milling treatment, the peaks of UHMWPE shift to lower temperatures while the peaks of LDPE kept stable. The more content of UHMWPE led to more evident shift. X‐ray diffraction analysis showed that the crystallinity of milled LDPE/UHMWPE blends decreased lightly, but the crystalline grain size decreased only for high content UHMWPE blends. The tensile properties of pan‐milled LDPE/UHMWPE blends also achieved significant improvement after pan milling treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2487–2493, 2013     

Effects of calcium carbonate and its purity on crystallization and melting behavior,mechanical properties,and processability of syndiotactic polypropylene

Calcium carbonate‐filled syndiotactic poly(propylene) (CaCO₃‐filled s‐PP) was prepared in a self‐wiping, co‐rotating twin‐screw extruder. The effects of CaCO₃ of varying particle size (1.9, 2.8 and 10.5 μm), content (0–40 wt %), and type of surface modification (uncoated, stearic acid‐coated, and paraffin‐coated) on the crystallization and melting behavior, mechanical properties, and processability of CaCO₃‐filled s‐PP were investigated. Non‐isothermal crystallization studies indicate that CaCO₃ acts as a good nucleating agent for s‐PP. The nucleating efficiency of CaCO₃ for s‐PP was found to depend strongly on its purity, type of surface treatment, and average particle size. Tensile strength was found to decrease, while Young's modulus increased, with increasing CaCO₃ content. Both types of surface treatment on CaCO₃ particles reduced tensile strength and Young's modulus, but improved impact resistance. Scanning electron microscopy (SEM) observations of the fracture surfaces for selected CaCO₃‐filled s‐PP samples revealed an improvement in CaCO₃ dispersion as a result of surface treatment. Finally, steady‐state shear viscosity of CaCO₃‐filled s‐PP was found to increase with increasing CaCO₃ content and decreasing particle size. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 201–212, 2004     

Influence of compatibilizers on mechanical properties,crystallization, and morphology of polypropylene/scrap rubber dust blends

Polypropylene blends containing a dispersed phase of scrap rubber dusts obtained from sport shoes manufacture; midsole (M, vulcanized EVA foam) and outsole (O, vulcanized rubber blend of NR, SBR, and BR) were studied. The influence of various compatibilizers on the mechanical properties of these blends were investigated. Significant development of impact strength was attained by using 6 and 10 phr of styrene–ethylene–butylene–styrene (SEBS) and maleic anhydride‐grafted styrene–ethylene–butylene–styrene (SEBS‐g‐MA) as compatibilizers for both compounds filled with midsole and outsole dusts. The tensile strength of each compound was slightly decreased when the compatibilizer loading increased, whereas the elongation at break was significantly increased. The enhancements of the impact strength and the elongation at break are believed to arise from reduction of interfacial tension between two phases of the rubber and the PP, which results in some reduction of the particle size of the fillers. Scanning electron microscopy (SEM) confirmed the evidence of the reduction of scrap rubber dust into small rubber particle sizes in the compound, and also showed the occurrence of some fibrils. Optical microscopy (crossed polars) observations suggested that the addition of the rubber dust resulted in a less regular spherulite texture and less sharp spherulite boundaries. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 148–159, 2002     

Influence of thermal history on crystalline morphologies of isotactic polypropylene in its miscible blends with polybutene‐1

The miscibility behaviors in blends of isotactic polypropylene (iPP) and polybutene‐1 (PB) have been studied using in‐situ FTIR imaging. The heterogeneous melt of 3/7 iPP/PB blends were formed at 250, 220, and 180°C and then quenched to the same crystallization temperature of iPP at 125°C, respectively. Evolution processes of composition distribution during crystallization were monitored according to their characteristic peaks, and the results suggest a trend from local concentration to uniform dispersion of PB fraction. Further studies of the PB fraction as the distance from the growth front of iPP spherulite indicate an irreversible phase behavior with the progress of thermal history. The cyclic melting and crystallization favor the mixing of iPP/PB blend. Meanwhile, the nonlinear growth rate of iPP spherulite is mainly responsible for compatible promotion of iPP/PB blend, which hinders the transportation of iPP chains to its growth front. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43282.     

Dynamic mechanical properties,crystallization behaviors,and low‐temperature performance of polypropylene random copolymer composites

In this study, polypropylene random copolymer (PPR) composites were prepared by the addition of either three kinds of thermoplastic rubber (TPR) modifiers (types 2088A, 2095, and 2096) or an ethylene–octene copolymer (POE)/high‐density polyethylene (HDPE; 2 :1 w/w) blend. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and dynamic mechanical analysis were used to characterize the crystallization behaviors and dynamic mechanical properties of the PPR composites. The results indicated that PPR/POE/HDPE and PPR/TPR2088A had better comprehensive mechanical properties, especially the low‐temperature toughness among all of the samples. The obtained PPR/POE/HDPE blends showed a high toughness and good stiffness in the temperature interval from ?10 to 23°C with the addition of only 10 wt % POE/HDPE. When the temperature continued to fall below ?10°C, the PPR/TPR2088A composites exhibited a better impact toughness without a loss of too much stiffness. The good low‐temperature toughness of those two composites was attributed to both the decrease in the crystallinity and the uniform dispersion, obvious interfacial adhesion, and cavitation ability of POE/HDPE and TPR2088A in the PPR matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42960.     

Morphology and thermal properties of recycled polyacrylonitrile fiber blends with poly(ethylene terephthalate): Microstructural characterization

The compounding of rPAN/PET [polyacrylonitrile/poly(ethylene terephthalate]; 30/70, 50/50, and 70/30 wt %) using a melt‐blending technique was the main focus of this investigation. An X‐ray diffraction study indicated the possibility of interphase boundary interactions between the polymer matrices in the blends. The differential scanning calorimetry results showed that varying the ratios of rPAN in the blends marginally improved the processing temperature of PET. The thermogravimetric analysis revealed that the addition of PET up to 70% increased the thermal stability of the blend, and adding more than 70% of PET resulted in poor adhesion between the matrix and phase. On the basis of the results obtained, we propose a general understanding of how the morphology and the mechanical and thermal properties of the blend could assist in the development of rPAN blends with PET, rather than disposing of the viable materials as wastes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43777.