Structure–property correlations of heat‐shrinkable polymer blends based on ethylene vinyl acetate/carboxylated nitrile rubber in the presence of different curatives

Elastic memory was introduced into heat‐shrinkable polymer blends in the form of an elastomeric phase and through subsequent crosslinking. Blends of ethylene vinyl acetate and carboxylated nitrile rubber with different curative systems were studied with respect to their shrinkability. With an increase in the cure time (the crosslinking density, or memory point), shrinkage increased for the blends with all the curative systems except dicumyl peroxide (DCP). Increasing the elastomer content increased shrinkability because of the increasing driving retraction force of the oriented elastomer phase. A sample stretched at a high temperature (HT) showed greater shrinkage than a sample stretched at room temperature (RT) because of the greater concentration and degree of orientation of the extended chains. Generally, the crystallinity of the stretched (RT and HT) samples was higher than that of ordinary unstretched and shrunk samples, and this increased the effectiveness of intermolecular interactions in the former. For all systems except DCP, RT‐stretched samples showed higher crystallinity than corresponding HT‐stretched samples. With RT stretching, rapid extension and subsequent recrystallization occurred in samples molten at high local values of the stored elastic energy. An increase in the crosslinking density and orientation of the blends increased the thermal stability because of the formation of strong networks and compact structures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1414–1420, 2003     

Understanding of intermolecular interaction in PVDF/PTW blends: Crystallization behavior,thermal, and dynamic mechanical properties

Poly(vinylidene fluoride) (PVDF)/ poly(ethylene–butylacrylate–glycidyl methacrylate) (PTW) blends were directly prepared by melt blending and the interaction and properties of PVDF/PTW blends were explored systematically. The crystallization behavior, thermal stability, dynamic mechanical property, and morphological features of PVDF/PTW blends with different ratios have been studied by XRD, attenuated total reflection Fourier transform infrared spectroscopy, differential scanning calorimeter analysis (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analysis, and polarized optical microscopy (POM). The results showed that the crystalline structure of neat PVDF was dominantly α‐phase crystalline and the incorporation of PTW had no effect on the crystalline structure of PVDF in the PVDF/PTW blends. And T_g of PVDF in PVDF/PTW blends shifted to higher temperature compared with that of neat PVDF, indicating the weak interaction between PVDF and PTW, which was corresponding to DSC and TGA results. An increase in the coarseness and ring‐band spacing observed from POM further substantiated the weak interaction between PVDF and PTW. This work provided a way for preparing improved properties of PVDF/PTW blends for the coating material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43908.     

Morphology and thermal expansion in large HDPE injection moldings

Morphology and linear coefficients of thermal expansion (LCTE) within the wall of a large (10 kg) injection molded container were evaluated. The study employed polarized light microscopic birefringence techniques, differential scanning calorimetry, scanning electron microscopy (SEM), as well as thermal mechanical analysis to determine the LCTE anisotropy in the skin and core of the wall. A difference in crystallinity between skin and core was found, and a region with distinct lamellas was seen under SEM without sample etching. A large variability in anisotropy of the LCTE was found in the relatively thick (~700 μm) skin of the molding. The LCTE differences between skin and core were attributed to molecular orientation related to resin flow. LCTE anisotropy as an important source of residual stress in the transition zone between skin and core was confirmed by fractographic analysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47507.     

Crystal structure transformations and orientation in crosslinked elastic fibers of an ethylene‐octene copolymer in response to deformation and heat treatment

Crosslinked elastic fibers, made from a low density (0.875 g/cc) ethylene‐octene copolymer, were studied after constrained at 300% elongation and annealed at different temperatures (40–80°C) to simulate conditions encountered in yarn and textile processing. It is surprisingly found that the transition from pseudo hexagonal to orthorhombic structure is much faster under simultaneously constraining and annealing than that without strain. Almost a neat orthorhombic structure can be produced when the fiber is annealed at 60°C. Annealing above 60°C leads to mixed orthorhombic and pseudo‐hexagonal structures. The average melting point increases with an increase in the fraction of orthorhombic phase. It is also surprisingly noted that the simultaneously constraining and annealing of the fiber can produce highly oriented crystals, even annealed at 80°C (above the average melting point of 65°C). The unique effect of annealing under large strain can be attributed to the crosslinking of the fiber, which makes it possible for the fiber to have strong chain orientation (even in molten state) under large strain. The strong chain orientation in melt leads to a faster structural transition from pseudo hexagonal to more stable orthorhombic structure. The strong chain orientation is also very likely the reason why highly oriented crystal and amorphous phases are formed, including the case where the fiber is annealed above melting point. These findings could be leveraged for improving thermal and mechanical properties of the fabrics made with such fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3565–3573, 2013     

Effects of titanate treatment on morphology and mechanical properties of graphene nanoplatelets/high density polyethylene nanocomposites

The effect of graphene nanoplatelets (GNPs) and titanate coupling agent on morphology and mechanical properties of high density polyethylene (HDPE) nanocomposites was investigated. The titanate has a tendency to link chemically with the two dissimilar species GNPs and HDPE via proton coordination to generate a complete continuous phase for stress/strain transfer via the elimination of air voids and hydrophobicity. The interaction of titanate with GNPs and HDPE was effective to improve the dispersion of GNPs in HDPE composites. At constant weight (1 wt %) of titanate treatment for 2 and 5 wt % HDPE composites, we clearly observed a significantly high value of tensile strength and elongation at break than untreated composites. Particularly, composite containing 2 wt % GNPs in HDPE with titanate showed 66.5% improvement of the ultimate tensile strength and an enormously high value of elongation at break. The effect of GNPs dispersion and orientation in HDPE for the mechanical reinforcement was also evaluated based on the experimental modulus data to theoretical predictions made using the Halpin‐Tsai model. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42073.     

Effect of rolling deformation on the structures and properties of multi‐walled carbon nanotube filled isotactic polypropylene

Isotactic polypropylene filled with various contents of multi‐walled carbon nanotubes (MWCNTs) were fabricated by the injection molding technique and then rolled at room temperature. The unrolled samples (URS) and rolled samples (RS) were characterized by X‐ray diffraction studies, scanning electron microscopy, mechanical and micromechanical tests and differential thermal analyses. Although the URS exhibit the lamellar α‐crystal with a*‐axis orientation, the RS show the same crystals with both a*‐ and c‐axis orientation, which is explained by interlamellar and intralamellar slips and lamellar destruction. Scanning electron micrographs display distinct surface morphological features for both URS and RS. While the tensile strength of RS is higher than that of URS, the Young's modulus (Y) is found to be lower than that of URS. Anisotropy in microharness (H) parallel and perpendicular to the rolled direction has been detected, although H for both samples increases with increasing MWCNT contents. The average relationship H/Y ≈ 0.18 as estimated for URS is closer to the predicted value of 0.10 for polymers than the H/Y ≈ 0.22 obtained for RS. The lamellar thickness for URS increases with increase of MWCNT content and that for RS decreases, as evaluated from both differential thermal analyses and X‐ray diffraction data. Copyright © 2011 Society of Chemical Industry     

Thermal,mechanical, and structural properties of zno/polyethylene membranes made by thermally induced phase separation method

In this study, ZnO/polyethylene membranes were fabricated via thermally induced phase separation method. A set of tests including FE‐SEM, EDX, XRD, DSC, TGA, DMA, mechanical test, and pure water flux (PWF) for characterization of membranes were carried out. The results of EDX, XRD, and TGA analyses confirmed the presence of ZnO nanoparticles in the polymer matrix. The results of DSC analysis revealed that the melting point as well as the crystallinity of the membranes increased slightly with increasing ZnO content. However, glass transition temperature of the membranes was not affected by presence of the particles. Addition of nanoparticles also increased storage modulus, loss modulus. and tensile at break of the membranes due to the stiffness improvement effect of inorganic ZnO. Finally, it was observed that incorporation of the nanoparticles improved PWF of the membranes, whereas humic acid rejection decreased due to the increase in mean pore radius of membranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42338.     

Phase‐separation of heterophasic polymer in solution: A model case of impact‐resistant polypropylene copolymer

Impact‐resistance polypropylene copolymer (IPC) has been well known as commercial heterophasic polymer in which ethylene–propylene random copolymer (EPR) domain is dispersed in the homo‐polypropylene matrix. The phase‐separation of those phases is one of the keys to control the polymer properties. However, especially in the solution, there is rarely report that addresses to the phase‐separation of the IPC due to the difficulties in the investigation; i.e., (i) the proximity of the refractive indices of those phases and (ii) the small size of the EPR droplet. Here, the phase‐separation of the commercial IPC in xylene is traced by the in situ small angle X‐ray scattering which the phase‐separation temperature is clearly revealed. The results also show that the evolution of the EPR domain is strongly depended on the polymer composition. Moreover, the migrations of the copolymers are evidenced, and this could be a model for other heterophasic systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45069.     

Synthesis and properties of novel organosoluble bismaleimides and polyaspartimides containing bis(4‐maleimido‐3, 5‐dimethyl phenyl) halo phenyl methane

A series of bismaleimides was synthesized from bis(4‐amino‐3, 5‐dimethylphenyl) (X) phenyl methane (X = 3′chloro, 3′‐bromo, 3′‐benzyloxy, 4′‐chloro, 4′‐fluoro) and maleic anhydride. The bismaleimides were subsequently polymerized with various diamines by Michael addition to yield novel polyaspartimides. All the polymers exhibited good solubility in organic solvents and the inherent viscosity of the polymers were in the range of 0.40–0.56 dL/g, which is good enough to fabricate composites and films. The temperature at which 10% weight loss occurred was in the range of 390–441°C. The polymers had high glass transition temperature in the range of 205–275°C and left about 31.95–84.20% char yield at 800°C indicating that they have good self‐extinguishing property. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

In situ electrical resistance and X‐ray tomography study of copper–tin polymer composites during thermal annealing

In situ electrical conductivity and X‐ray tomography experiments are conducted on a conductive polymer composite containing polyvinylidene fluoride (PVDF) copolymer, copper (Cu), and tin (Sn) during thermal annealing. During annealing, the electrical resistivity drops by an order of magnitude, while X‐ray tomography, electron microscopy, and spectroscopy results show increasingly homogeneous dispersion of Sn in the conductive filler network, accompanied by the formation of Cu–Sn intermetallic around Cu and Sn particles. This study provides detailed insight into the morphological origins of the beneficial effect of thermal annealing on the electrical properties of conductive composites containing low melting metal fillers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45399.     

Synthesis and evaluation of two new FI‐Ti catalysts for living polymerization of ethylene

Two new FI complexes, bis[N‐(3‐allylsalicylidene)‐pentafluoroanilinato]titanium(IV) dichloride ( AFI ) and bis[N‐(3‐propylsalicylidene)‐pentafluoroanilinato]titanium(IV) dichloride ( PFI ) were designed and synthesized as catalysts for living polymerization of ethylene. The two complexes were characterized by elemental analysis, spectroscopy and X‐ray single diffraction. The catalysts were evaluated in ethylene polymerization under atmospheric pressure. It was found that both catalysts exhibited high activity and good livingness. The effects of temperature and dMAO/Ti molar ratio on the polymerization behavior of AFI were studied in detail. Elevating temperature increased self‐immobilization of the AFI catalyst, which broadened the polymer molecular weight distribution. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Elaboration and thermal analysis of nanocomposites based on poly(methyl methacrylate‐co‐4‐vinylpyridine) and Maghnia bentonite

Nanocomposites based on an organically modified bentonite, from Maghnia Algeria (OBT) and a copolymer of methyl methacrylate with 4‐vinylpyridine (PMM4VP) synthesized in dioxan at room temperature using a neutral Ni(II)α‐benzoinoxime complex as a single component initiator, were elaborated via solution intercalation method and characterized by several techniques. X‐ray diffraction and transmission electron microscopy investigations indicate that mainly exfoliated and intercalated PMM4VP/OBT nanocomposites were elaborated and that the degree of exfoliation decreases with an increase of the OBT loading. Thermal analyses of these nanocomposites compared with their virgin copolymer confirmed a significant improvement of their thermal stability as evidenced by an increase of 28°C in their onset degradation temperatures. In addition, differential scanning calorimetry displayed an increase in the range of 12–18°C in their glass transition temperatures relative to their virgin copolymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of cooling rate on the thermal behavior and solid‐state morphologies of polyhydroxyalkanoates

The influence of cooling rates on the thermal behavior and solid‐state morphologies of polyhydroxyalkanoates have been investigated. The thermal behavior was studied by differential scanning calorimetry (DSC). The crystal structures (～ Å), lamellar (tens of nanometers), fibrillar (several hundred nanometers), and spherulitic (～ μm) morphologies of poly (3‐hydroxybutyrate) (PHB) and the copolymers of poly (3‐hydroxybutyric acid‐co‐3‐hydroxyvaleric acid) (PHBV) and poly (3‐hydroxybutyric acid‐co‐3‐hydroxyhexanoic acid) (PHBHx) crystallized under different cooling rates were studied using simultaneous small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering, simultaneous ultra small angle X‐ray scattering (USAXS) and SAXS, and polarized optical microscopy, respectively. The experimental results showed that the lamellar and spherulitic morphologies depended strongly on cooling rates. However, there was little influence of cooling rates on the crystal structures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

The effect of sulfonation treatment on the structure and properties of isotactic polypropylene fibers prior to the carbonization stage

The effect of sulfonation treatment was investigated on the molecular structure and mechanical properties of isotactic polypropylene fibers extruded at a take up speed of 2500 m/min. It was found that at extensive sulfonation times, the sulfonated structure showed the characteristic features of carbonized structure as indicated by the results of the density and the X‐ray diffraction measurements. Mechanical properties of the sulfonated samples were found to be adversely affected by the sulfonation conditions. Scanning electron microscopy observations showed surface irregularities at low sulfonation times and fiber fractures at high sulfonation times. Polarized infrared spectroscopy measurements analysed by curve fitting procedure showed increasing molecular orientation of long helical chain segments represented by the IR band at 841 cm^?1 whereas amorphous structure represented by the IR band at 2723 cm^?1 showed gradual loss of orientation with the progress of sulfonation. IR bands assigned to the sulfonic acid groups formed during sulfonation treatment showed perpendicular polarization and low molecular orientation characteristics indicating the initiation and the development of crosslinking process being perpendicular to the fiber axis direction. Analysis of the equatorial X‐ray diffraction traces showed the loss of crystallinity where the paracrystalline phase disappeared faster than the crystalline α‐monoclinic phase. During the sulfonation treatment, content of amorphous phase showed gradual increase in line with decreasing crystallinity. In accordance with the loss of crystallinity, apparent crystallite sizes corresponding to the 110, 040 and 130 planes of the α‐monoclinic phase also decreased gradually with increasing sulfonation time. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Surface treatment of eucalyptus wood for improved HDPE composites properties

In this study, the effect of Eucalyptus globulus wood (UE) used as a filler (5–20% w/w) on the physical and thermal properties of high-density polyethylene (HDPE) composites was evaluated. To improve the compatibility with HDPE, the wood was modified (TE) using crude glycerol derived from biodiesel production. The addition of 20% (w/w) of UE or TE led to more rigid and durable composite materials compared to neat HDPE (about 50 or 100% increase in tensile strength, respectively). Composites also revealed 55–75°C higher temperatures at maximal degradation rates. The advantageous behavior of TE over UE in composites was attributed to the improvement of surface morphology of modified wood and it is better compatibility with the HDPE as revealed by surface energy analysis. The changes in wetting behavior of HDPE and ensuing HDPE-TE composites (contact angles of ca 72 and 80°, respectively) explain the matrix-filler interactions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48619.     

Effects of solution mixing temperature on dielectric properties of PMMA/Pristine bentonite nanocomposites

We examined the effects of mixing temperature on the dielectric properties of polymethylmethacrylate (PMMA)‐pristine bentonite nanocomposites by using X‐ray diffraction, FT‐IR and dielectric spectroscopies. The samples were prepared during 8 hours at temperatures 265 K, 273 K, 281 K, 289 K and 298 K without any intercalative agent and the PMMA to pristine bentonite weight ratio was chosen as 1 : 10. It was observed that with decreasing the mixing temperatures, the permittivity decreases and the dielectric relaxation displaces towards the lower frequencies with the decrease of mixing temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39907.     

Enhanced dielectric properties of poly(vinylidene fluoride)–surface functionalized BiFeO3 composites using sodium dodecyl sulfate as a modulating agent for device applications

In this work, we prepared a series of poly(vinylidene fluoride) (PVDF)–surface functionalized BiFeO₃ (h‐BFO)–Sodium dodecyl sulfate (SDS) composite films by solvent casting method to investigate the effect of SDS in the composites. The X‐ray diffraction confirmed that the structure of h‐BFO significantly changed in the PVDF‐(h‐BFO)‐SDS composite in comparison with the rhombohedral structure of pure BiFeO₃. The microscopic study illustrated that the composite with a higher percentage of SDS content facilitated the dispersion as well as proper distribution of ceramic particles in the polymer matrix. The presence of different functionalities of respective polymer and the modified fillers was confirmed by FTIR Spectrophotometer. The dielectric and electrical study done by Impedance Analyzer revealed that the SDS treated surface functionalized composites showed relatively higher dielectric properties than that of two phase composites and pure polymer. Finally, the ferroelectric properties of the composite films done by P‐E loop tracer revealed that the SDS‐treated composites showed an enhanced remanent polarization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45040.     

Thermal and morphological studies of chemically prepared emeraldine‐base‐form polyaniline powder

In this study, emeraldine base (EB)‐form polyaniline (PANI) powder was chemically prepared in 1M HNO₃ aqueous solution. The thermal characteristics and chemical structures of this powder were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). A polarizing optical microscope was also used to examine the crystalline morphology of this sample. The results indicated that the EB‐form PANI powder had a discernible moisture content. Moreover, in the first run of DSC thermal analysis, the exothermic peak at 170–340°C was due to the crosslinking reaction occurring among the EB‐form PANI molecular chains. FTIR and XRD examinations further confirmed the chemical crosslinking reaction during thermal treatment. TGA results illustrated that there were two major stages for weight loss of the EB‐form PANI powder sample. The first weight loss, at the lower temperature, resulted from the evaporation of moisture. The second weight loss, at the higher temperature, was due to the chemical structure degradation of the sample. The degradation temperature of the EB‐form PANI powder was around 420–450°C. The degradation temperature of emeraldine salt (ES)‐form PANI powder was lower (around 360–410°C) than that of the EB form (around 420–450°C). From the TGA results, I roughly estimated that 2.74 aniline repeat units, on average, were doped with 1 HNO₃ molecule in the ES‐form PANI. I found a single crystalline morphology of EB‐form PANI, mostly like a conifer leaf. More complex, multilayered dendritic structures were also found. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2142–2148, 2003     

Mechanical and film properties of thermally curable polysiloxane

Telechelic glycidyl epoxide siloxanes substituted with either methyl, cyclopentyl, or cyclohexyl groups were cured thermally with corresponding telechelic aliphatic amine. Also, the three glycidyl epoxide functionalized siloxanes were homopolymerized via a photo‐initiated cationic mechanism. Both the UV and thermal curing were performed by formulating with reactive diluents. The mechanical properties, viscoelastic behavior, and coatings properties of the thermally cured siloxanes were studied. In addition, the X‐ray measurements were performed. The rate of polymerization increased with the increasing size of substituent on the siloxane backbone. The hardness, adhesion, and solvent resistance increased as the bulk of the substituent increased in the siloxane backbone. The release properties for adhesion and readhesion increased with increase in steric bulk of the backbone substituents. Crosslink density reduced and oxygen permeability increased with increase in siloxane substituent size. There was also an increase in the advancing and the receding contact angles with the increase in substituent size. The inverse dependency of substituent size and free volume was observed in the d‐spacing of the X‐ray data. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010