Compatibilization of low‐density polyethylene/plasticized starch blends by reactive compounds and electron beam irradiation

Blends based on various compositions of low‐density polyethylene (LDPE) and plasticized starch (PLST) were prepared by melt extrusion and molding in the form of sheets under hot press. The rheology properties during mixing were studied in terms of torque and temperature against mixing time. The structural properties of LDPE/PLST blends before and after electron beam irradiation was characterized by IR spectroscopy, tensile mechanical testing, and scanning electron microscopy (SEM). The torque‐time curves during the mixing process showed that the values of torque in the first region of mixing for pure LDPE or LDPE/PLST blends are higher in the presence of the compatibilizer PEMA than that in the presence of EVA. In addition, the stability of mixing was attained after a short time in the presence of PEMA. The IR spectroscopy suggests that the compatibilization by EVA and PEMA compounds proceeds through the formation of hydrogen bonding during mixing and this compatibility was improved after electron beam irradiation. The stress–strain curves of pure LDPE and its blends with PLST showed the behavior of tough polymers with yielding properties. The SEM micrographs of the fracture surfaces give supports to the effect of EVA and PEMA as compatibilizers and the effect of electron beam irradiation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Radiation‐processed polychloroprene‐co‐ethylene–propene diene terpolymer blends: Evaluation of blend morphology,miscibility, and physical properties

The miscibility of polychloroprene rubber (CR) and ethylene–propylene–diene terpolymer rubber (EPDM) was studied over the entire composition range. Different blend compositions of CR and EPDM were prepared by initially mixing on a two‐roll mill and subsequently irradiating to different gamma radiation doses. The blends were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, density measurement, hardness measurement, and solvent permeability analysis. The compatibility of the blends was studied by measuring the glass transition temperature and heat capacity change of the blends. The immiscibility of blends was reflected by the presence of two glass transition temperatures; however, partial miscible domains were observed due to inter diffusion of phases. Permeation data fitted best with the Maxwell's model and indicated that in CR‐EPDM blends, EPDM exists as continuous phase with CR as dispersed phase for lower CR weight fractions and phase inversion occurred in 40–60% CR region. It was observed that CR improved oil resistance of EPDM; however, the effect was prominent for blends of >20% CR content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blends of polypropylene and ethylene octene comonomer with conducting fillers: Influence of state of dispersion of conducting fillers on electrical conductivity

Blends of polypropylene/ethylene octene comonomer (PP/EOC) with conducting fillers viz., carbon black (CB) and multiwall carbon nanotubes (MWNT) were prepared using melt mixing technique with varying filler concentration and blend compositions. Thermo gravimetric analysis studies indicated that presence of filler enhanced the thermal stability of PP/EOC blends. Morphological analysis revealed the formation of matrix‐dispersed droplet and co‐continuous type of morphology depending on the blend compositions. Significant reduction in droplet size and finer ligament thickness in co‐continuous structure were observed in the blends with filler due to compatibilization action. Fillers were found to be aggregated in the EOC phase irrespective of blends compositions and could be related to the affinity of the fillers toward EOC phase. The electrical conductivity of PP/EOC blends with CB and MWNT was found to be highest for 80/20 composition and decreased as EOC content increased. The percolation threshold of CB was between 10 and 15 wt% for the 80/20 and 70/30 blends whereas it was 15–20 wt% for blends with EOC content higher than 30 wt%. The percolation threshold was 2–3 wt% MWNT for PP/EOC blends. This was attributed to the aggregated filler network preferentially in the EOC phase. The melt‐rheological behavior of PP/EOC blends was significantly influenced in presence of both the fillers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Effect of blend ratio and elongation flow on the morphology and properties of epoxy resin‐poly(trimethylene terephthalate) blends

The effect of processing conditions on the morphology of polymer blends is a topic of tremendous practical interest especially for thermoset–thermoplastic blends. The effect of blend ratio and the nature of the flow field (shear flow vs. elongation flow) on the morphology is followed here using blends of diglycidyl ether of bisphenol A (DGEBA)‐poly(trimethylene terephthalate) (PTT). Morphology of the blends prepared by the conventional melt mixing technique is compared with that prepared by using an elongation mixer (RMX device invented by Muller et al.). The blends prepared by the elongation mixer showed excellent transparency and higher storage modulus at room temperature than the conventional mixer. In the case of samples prepared by the RMX device T_g of the epoxy phase has been shifted to lower temperatures indicating a molecular level mixing between PTT and DGEBA. However the conventional melt mixed samples showed only a marginal shift in T_g to low temperatures indicating that the system is not as miscible as that prepared by the RMX device. The use of RMX device for thermoset–thermoplastic blends is novel and no work has been reported in this relation. The properties of the blends were strongly affected by the composition and the crystallization of the semicrystalline PTT phase. POLYM. ENG. SCI., 55:1679–1688, 2015. © 2014 Society of Plastics Engineers     

The influence of matrix viscosity and composition on the morphology,rheology, and mechanical properties of thermoplastic elastomer nanocomposites based on EPDM/PP

The morphological and rheological properties of thermoplastic elastomer nanocomposites (TPE nanocomposites) were studied using different viscosities of polypropylene (PP) and ethylene‐propylene‐diene monomer (EPDM) rubber content (20, 40, 60 wt%). The components, namely EPDM, PP, Cloisite 15A, and maleic anhydride‐modified PP as compatibilizer, were compounded by a one‐step melt mixing process in a laboratory internal mixer. The structure of the nanocomposites was characterized with X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and rheometry in small amplitude oscillatory shear. The distribution state of the clay between the two phases (PP and EPDM) was found to be dependent on the viscosity ratio of PP to EPDM. In the nanocomposites prepared based on low viscosity PP (LVP) and EPDM, the clay was mostly dispersed into the PP phase and the size of the dispersed rubber particles decreased in comparison with unfilled but otherwise similar blends. However, the dispersed elastomer droplet size in the high viscosity PP (HVP) blends containing 40 and 60% EPDM increased with the introduction of the clay. For TPE nanocomposites, the dependence of the storage modulus (G′) on angular frequency (ω) followed a clear nonterminal behavior. The increase in the storage modulus and the decrease in the terminal zone slope of the elastic modulus curve were found to be larger in the LVP nanocomposite in comparison with the HVP sample. The yield stress of nanoclay‐filled blends prepared with LVP increased more than that of HVP samples. The tensile modulus improved for all nanocomposites but a higher percentage of increase was observed in the case of LVP samples. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Influence of the mixing time on the phase structure and glass‐transition behavior of poly(ethylene terephthalate)/poly(ethylene‐2,6‐naphthalate) blends

Blends of poly(ethylene terephthalate) and poly(ethylene‐2,6‐naphthalate) (70 : 30 w/w) were prepared via a melt‐mixing process at 280°C with various mixing times. The melt‐mixed blends were analyzed by magnetic resonance spectroscopy, differential scanning calorimetry, dynamic mechanical measurements, transmission electron microscopy, and tensile tests. The results indicate that the blends mixed for short times had lower extents of transesterification and were miscible to a limited extent. The blends initially show two glass transitions, which approached more closely and merged gradually with increasing mixing time. A mechanical model was used to help understand the glass‐transition behavior. With increasing mixing time, the phase structure of the blends improved, and this led to an increase in the tensile strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of reactive melt mixing on the morphology and thermal behavior of linear low-density polyethylene/rubber blends

Linear low-density polyethylene (LLDPE)/polybutadiene (PB) and LLDPE/poly(styrene-b-butadiene-b-styrene) (SBS) binary blends were prepared by simple melt mixing or by reactive blending in the presence of a free-radical initiator, and for comparison, pure LLDPE was treated under the same conditions with a comparable free-radical initiator concentration. The effect of the reactive melt mixing on the morphology of the blends was studied with transmission electron microscopy, and the corresponding particle size distributions were analyzed and compared to highlight the effects of the crosslinking and grafting phenomena. Thermal properties of the obtained materials were investigated with differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA). In particular, the effect of the reactive mixing parameters on the amorphous phase mobility was investigated. The influence of the chemical modification on the crystallization behavior of LLDPE, neat and blended with PB and SBS, was also studied with dynamic and isothermal differential scanning calorimetry tests, and the isothermal thermograms were analyzed in light of the Avrami equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Conductive mechanism of antistatic poly(ethylene terephthalate)/ZnOw composites

Antistatic composites of poly(ethylene terephthalate) (PET) and tetrapod‐shaped ZnO whisker (ZnOw), the surface of which was treated with a coupling agent, were prepared by melt‐mixing using a twin screw extruder. The structure and morphology of the blends were examined by FTIR and SEM. Antistatic performance and the effect of ZnOw loading levels were investigated. The conductive mechanism of PET/ZnOw composites is presented, which can be classified into tunnel effect, discharging effect at the pinpoint and conductive network. The simple formula of critical volume fraction (v_c) for ZnOw forming conductive network is proposed, based on the actual processing conduction. Comparison of the theory value to the experimental data showed a close agreement. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Solid‐state blending of poly(ethylene terephthalate) with polystyrene: Extent of compatibilization and its dependence on blend composition

Polystyrene (PS) and poly(ethylene terephthalate) (PET) were blended together in the solid state via cryogenic mechanical attrition (CMA) and in the melt through conventional twin‐screw extrusion. Consecutive modulated differential scanning calorimetry (MDSC) and thermogravitometric analysis (TGA) investigations allowed for the quantitative estimation of the extent of blend compatibility through the accurate determination of sample composition. The extent of blend compatibility, i.e., the amount of PET calculated to have been removed from the bulk and into interphase entanglements with PS, was found to be higher for milled blends than for extruded blends. This compatibility enhancement was the most pronounced for PET‐rich blends. The other benefits of CMA are more precise compositional homogeneity through intimate mixing and the ability for more amorphous PET chains to be entangled with the amorphous PS phase at the interphase. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Properties and phase structure of melt-processed PLA/PMMA blends

This study examines the rheological, mechanical and thermal behavior of Poly(lactic acid)/Poly(methyl methacrylate) (PLA/PMMA) blends and takes a look at the phase structure evolution during their melt processing. Semi-crystalline or amorphous PLA grades were combined with PMMA of different molecular weight to prepare the blends. The rheological properties and phase structure was first assessed using small-amplitude oscillatory shear experiments. The blends were injection molded into bars and characterized in terms of their tensile properties and of their dynamic mechanical behavior. Differential scanning calorimetry was also used to study the miscibility and crystallization behavior of prepared blends. Tensile properties of the blends nearly followed a linear mixing rule with no detrimental effect that could have been associated with an uncompatibilized interface. However, dynamic mechanical analysis and calorimetric experiments showed that some phase separation was present in the molded parts. Nevertheless, a single T_g was found if sufficient time was given in quiescent conditions to achieve miscibility. The Gordon-Taylor equation was used to assess the polymer interactions, suggesting that miscibility is the thermodynamically stable state. The ability of PLA to crystallize was strongly restricted by the presence of PMMA and little or no crystallinity development was possible in the blends with more than 30% of PMMA. Results showed an interesting potential of these blends from an application point of view, whether they are phase separated or not.     

Effect of Mixing Conditions on the Tensile Properties of Ethylene Vinyl Acetate/Waste Tire Dust (EVA/WTD) Blend

Blends of Ethylene Vinyl Acetate/Waste Tire Dust (EVA/WTD) were prepared by using a Haake Rheomix at 100/0, 90/10, 80/20, 70/30, and 60/40 blend ratios. The effect of mixing temperature, blend ratio and blending time on the tensile properties of EVA/WTD blends were investigated. The mixing time was varied from 5 to 30 minutes, while the mixing temperature was varied from 120 to 160°C. The tensile properties of the blends found to show a gradual decrease with the addition of WTD. EVA/WTD blends prepared at 140°C mixing temperature and 10 min mixing time found to be suitable mixing parameters to obtain optimum blend properties. In general, declines in the EVA/WTD blends properties were also observed with increase in mixing time and temperature.     

Morphology development of EPDM/PP uncross‐linked/dynamically cross‐linked blends

Ethylene‐propylene‐diene‐terpolymer (EPDM) and polypropylene (PP)‐based uncross‐linked and dynamically cross‐linked blends were prepared both in an internal mixer and in a corotating twin‐screw extruder. The effects of composition, plasticization and mixing equipment on the morphology development and the final viscoelastic properties were studied. In the uncross‐linked blends, the plasticization resulted in a coarser morphology. Furthermore, it was shown that the majority of the plasticizer resided in the EPDM phase, enabling its deformation in the flow direction. In addition, the intensive mixing conditions inside the twin‐screw extruder resulted in a finer morphology. In the dynamically cross‐linked blends, the twin‐screw extrusion process resulted in a higher level of gel content with larger EPDM domains. The plasticization showed again a coarsening effect, resulting in interconnected cross‐linked EPDM domains. An interesting interfacial phenomenon was observed especially in the plasticized vulcanized blends where nanometer size occluded PP domains were stripped off and eroded into the EPDM phase. With the exception of the nonplasticized uncross‐linked blends, the viscoelastic properties of all other blending systems were found to be directly affected by the morphology, gel content (in the case of cross‐linked blends), and the presence of the plasticizer. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Effect of the mixing conditions on the phase structure of PP/PS blends

The effect of the rate and time of mixing in a batch mixer on the phase structure of polypropylene/polystyrene (PP/PS) blends with various rheological properties of the components was studied. Regions with substantially different average sizes of the dispersed particles were found in the studied blends. Differences between the average size of the particles in individual regions of the samples persist in all blends and mixing conditions under study. No dependence of the average particle size on the rate of mixing has been obtained for the PP/PS (75/25) blends. On the other hand, decrease of the average particle size with increasing rate of mixing has been found for the PP/PS (95/5) blend. These results are discussed as a consequence of the competition between the breakup and coalescence of the dispersed particles. © 1996 John Wiley & Sons, Inc.     

Investigation on particular phase morphology of immiscible polyamide 12 and polystyrene blends prepared via anionic ring‐opening polymerization

In this article, the particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring‐opening polymerization of laurolactam (LL) in the presence of polystyrene (PS) was investigated. Scanning electron microscopy (SEM) and Fourier Transform infrared Spectroscopy (FTIR) were used to analyze the morphology of the blends. The results show that the PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is 5 wt%. However, when the PS content is higher than 10 wt%, two particular phase morphologies appeared. Firstly, dispersed PS‐rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 and 15 wt%. Then the phase inversion occurred (the phase morphology of the PA12/PS blends changed from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) when PS content is 20 wt% or higher, which is unusual for polymer blends prepared via conventional methods such as mixing, hydrolytic polycondensation and so on. The formation of this particular phase morphology development was simply elucidated via a phase inversion mechanism. Furthermore, the stability of the phase morphology of the PA12/PS blends after annealing at 230°C was also investigated via SEM. POLYM. ENG. SCI., 52:1831–1838, 2012. © 2012 Society of Plastics Engineers     

Effect of Organo-Modified Montmorillonite on the Morphology and Properties of SEBS/TPU Nanocomposites

In this study, novel polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS)/thermoplastic polyurethane (TPU)/organo-modified montmorillonites (OMMT) nanocomposites were prepared by melt mixing. Three different organo-modified montmorillonites, DK2, DK3, and DK4 (listed in descending order of hydrophilicity) were selected. The compatibilizing and reinforcing effects of OMMT on the structure, morphology, thermal stability, mechanical and rheological properties of the SEBS/TPU blends were studied. It was found that the hydrophilic DK2 nanoparticles were largely located in the continuous TPU phase and partially dispersed at the phase interphase, whereas DK3 and DK4 nanoparticles were preferentially located at the phase interface with an intercalated/exfoliated and intercalated structure, respectively. Scanning electron microscopy (SEM) results showed that SEBS/TPU/OMMT nanocomposites exhibited a more densely organized and interconnected structure compared with SEBS/TPU blends. Better thermal property was achieved after adding DK3, with the tensile properties of the SEBS/TPU increased considerably. Rheological analysis revealed that hydrophilic DK2 nanoparticles were more effective in improving rheology properties and showed a more pronounced nonlinear effect. The prepared SEBS/TPU/OMMT nanocomposites displayed desired thermal, mechanical and rheological properties, which are important for many applications. POLYM. ENG. SCI., 60:850–859, 2020. © 2020 Society of Plastics Engineers     

α-成核剂对PP/SEPS共混体系脆-韧转变的影响

采用熔融共混法制备了具有不同α成核剂(α-NA)含量的聚丙烯(PP)和氢化苯乙烯异戊二烯苯乙烯嵌段共聚物（SEPS）共混体系,通过扫描电子显微镜观察了不同共混体系分散相的粒子尺寸及分布,根据逾渗模型计算了不同共混体系的粒子间距,定量描述了α NA含量对共混体系临界粒子间距的影响。结果表明,α-NA的含量越高,共混体系的临界粒子间距越大,越有利于脆韧转变的发生。     

Morphology and rheology of polysulfone/Vectra-A950 blends

Blends of polysulfone (PSu) with a liquid crystalline copolyester (Vectra-A950; VA) have been prepared by melt mixing. Their morphology has been studied by scanning electron microscopy (SEM). Either blend specimens as obtained from the melt mixing or fibers drawn from the melt were used for the SEM analysis. Further information on the morphology of the blends was gained by extraction of the PSu phase with methylene chloride. Preliminary rheological characterization of the blends was made by measuring the viscosity curves at 290 and 300°C, with a capillary viscometer having a die of 1 mm diameter and L/D = 40. Finally, an attempt at improving the phase compatibility was made by synthesizing a copolyester, having the same structure of commercial VA, in the presence of preformed PSu and using the product as a possible compatibilizer. It was demonstrated that the blends are composed of two immiscible phase showing poor adhesion. The LCP droplets could, nevertheless, be deformed into oriented fibrils under elongational flow conditions. The LCP particles were shown to coalesce into large domains, and to migrate toward the outer layer of, e.g., extruded rods, under the influence of appropriate flow conditions, thus showing that there is a strong mutual influence between morphology and rheology of these materials. © 1995 John Wiley & Sons, Inc.     

Preparation and characterization of poly(methyl methacrylate) beads

The phase behavior of Poly(ethylene terephthalate)/Poly(ethylene‐2,6‐naphthalate)/Poly(ethylene terephthalate‐co‐ethylene‐2,6‐naphthalate) (PET/PEN/P(ET‐co‐EN)) ternary blends in molten state was evaluated from differential scanning calorimetry (DSC) and NMR results as well as optical microscopic observations. Copolymer of ethylene terephthalate and ethylene‐2,6‐naphthalate was prepared by a condensation polymerization, which was a random copolymer with an intrinsic viscosity (IV) of 0.3 dL/g. The phase diagram of the ternary blends revealed that the miscibility of ternary blends in molten state was dependent on the fraction of P(ET‐co‐EN) in the blends and holding time of the blends at high temperatures above 280°C. With increase in the holding time, the fraction of copolymer in the blends necessary to induce the immiscible to miscible transition decreased. For the blends with longer holding time at 280°C, the phase diagram in molten state was irreversible against the temperature, although a reversibility was found for the blends with short holding time of 1 min at 280°C. The irreversibility of phase behavior was not explained simply by the increase of copolymer content produced during heat treatment. Complex irreversible physical and chemical interactions between components and change of phase structure of the blend in the molten state might influence on the irreversibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology evolution of immiscible LDPE/PVC blends in the presence of compatibilizer and phase dispersant

Phase dispersion and coalescence in low‐density polyethylene (LDPE)/polyvinyl chloride (PVC) (70/30) blends influenced by compatibilizer and phase dispersant was studied. It was found that the morphology evolution of blends is sensitive to not only processing conditions (shear strength and mixing time) but also the added compatibilizer or phase dispersant. In our conditions, the stable phase morphology of each blend is obtained after mixing 15–25 min. In addition, the dispersed PVC phase in blends is easy to aggregate when the mixing rotor speed changed from high to low for the binary blends. As a compatibilizer, chlorided polyethylene (CPE) or nitrile rubber (NBR) can stabilize the morphology and hinder the coalescence of the dispersed PVC phase when added to the blends. However, the phase dispersant butadiene rubber (BR) or styrene butadiene rubber (SBR) could not stabilize the phase structure, although it could accelerate phase dispersion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 763–772, 2004     

Effect of montmorillonite modification on the behaviour of polyamide/polystyrene blends

BACKGROUND: In nanocomposites with multiphase matrices, the addition of layered silicate not only has a reinforcing effect, but also changes significantly the morphology, namely the size and the structure of the dispersed phase. In this paper, we focus on systems with polyamide 6 (PA6)/polystyrene (PS) matrices. The effect of clay was studied over the whole composition range together with the simultaneous variation of basic parameters influencing the structure and mechanical behaviour, i.e. the clay treatment type and mixing protocol. RESULTS: At all compositions, remarkable refinements of both particulate and co‐continuous structures by clay were found. This effect and a significant shift of the glass transition temperature of blend components were more pronounced for clay with less polar treatment as a result of distinct localization of clay in the interfacial area (due to its lower affinity for PA6 phase). An increase in modulus was found at all compositions, whereas strength and toughness were enhanced at low PS contents only, as a consequence of small particle size and enhanced interfacial bonding. CONCLUSIONS: The results presented indicate that nanosilicates can effectively influence the structure and properties of PA6/PS blends. Copyright © 2008 Society of Chemical Industry