Polymer blends • molecular level • A short Review on new ......hydrogen bonding, acid-base reaction or charge transfer [4]. Classifications of polymer blends [5-7] During the last

ELASTOMERE UND KUNSTSTOFFE ELASTOMERS AND PLASTICS

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Polymer blends • molecular level • Compatibilizer

Polymer blends have been become one of the most important research in the field of polymers. Their importance ari-ses from new and superior properties compared with one component poly-mers. The production of such polymer blends makes it possible to improve the physical properties of the individual po-lymers and consequently offers an eco-nomic way to design new polymeric materials with improved properties.Polymer blends may be miscible or im-miscible according to molecular level. Three different types of blend can be di-stinguished: completely miscible blends; partially miscible blends; and fully im-miscible blends. Most polymer blends form immiscible blends, revealing a pro-minent interface. This can be achieved by using different sorts of compatibili-zers, added to the polymers involved, which are often semi-crystalline.

Ein kurzer Überblick zu neuen Trends bei Polymerverschnitten Polymerverschnitte • Molekulares Niveau • Verträglichmacher

Polymerverschnitte sind ein sehr be-deutendes Feld der Polymerforschung geworden. Ihre Bedeutung geht aus neuen und überragenden Eigenschaf-ten im Vergleich zu Einkomponenten-polymeren hervor. Die Herstellung der-artiger Polymerverschnitte macht es möglich die physikalischen Eigenschaf-ten der einzelnen Polymer zu verbes-sern und folglich einen wirtschaftlichen Weg anzubieten, um neue Polymer-werkstoffe mit verbesserten Eigen-schaften zu entwickeln. Polymerver-schnitte können auf molekularer Ebene mischbar oder nicht mischbar sein. Es werden drei verschiedene Typen von Verschnitten unterschieden: Vollständig mischbar, teilweise mischbar und voll-ständig umischbar. Die meisten Poly-merverschnitte bilden unmischbare Verschnitte, welche eine vorherrschen-de Übergangsphase aufweisen. Diese kann durch den Einsatz von verschiede-nen Sorten von Verträglichmachern er-reicht werden.

Figures and Tables: By a kind approval of the authors.

IntroductionPolymer blends are defined as physical mixture of at least two polymers or co-polymers that may be either homogene-ous or heterogeneous at the molecular level. The commercially useful polymer- polymer combinations are linked by in-termolecular forces, such as hydrogen bonding, Vander Waals force, or dipole moment and exhibit sufficient thermo-dynamic compatibility to prevent the polymer phases from separation during melt processing [1].

The ability to produce blends that have a better combination of properties than that of the individual components depends on the compatibility of the sys-tem. The term compatibility refers to in-timate mixtures of two or more poly-mers. The individual components may be melt-mixed, solution-bonded, and copre-cipitated or lattices may be bonded and coagulated before final processing.

Blending or mixing of polymers are employed for variety of reasons which include improvement of the technical properties of the original polymer, achievement of better processing behav-ior, improved physical properties, and lowering of compound cost. All polymers have deficiencies in one or more proper-ties and blending is a way of obtaining optimum all-around performance [2&3].

Generally, any property of the blend can be predicted by the following rela-tionship:

P = P1C1 + P2C2 + IP1P2

Where, P is the property value of the blend, P1 and P2 are the property values of the individual polymer constituents, C1 and C2 are the concentrations of the two polymer components, and I is the interaction coefficient, which describes the level of synergism or thermodynamic compatibility of the polymers in the mix-tures. Therefore, positive value of the in-teraction coefficient (I > 0) leads to poly-mer combination exhibiting better prop-erty values than that of arithmetic aver-age of the constituent polymer properties, and a synergistic property will result. If I = 0, the properties of the combination are equal to that of arith-

metic average of the constituent proper-ties, i.e. additive property of the blend will result. When negative value (I < 0) for interaction coefficient will give proper-ties below those predicted by arithmetic property averages of the components, i.e. a non synergetic property of the blend will result. The effect of various interaction of polymer mixture is depict-ed in Figure 1.

Thermodynamic of polymer blendsThe Gibbs free energy of mixing must be negative for miscible polymer blend. The expression that governs free energy of mixing is

∆Gmix = ∆Hmix - T ∆Smix

The enthalpy term ∆Hmix is essentially independent of molecular weight and is a measure of the energy change associ-ated with intermolecular interactions. It is the dominating factor determining miscibility of high molecular weight pol-ymers.

A short Review on new Trends in Polymer Blends

AuthorA. I. Khalaf, Dokki, Giza, Egypt Corresponding Author:A. I. KhalafPolymers and Pigments Depart-mentNational Research Centre33 EL Bohouth St. (former EL Tahrir st.)Post Number 12622 Dokki - Giza, EgyptTel: + (202) (333 5 975) or

+ (202) (333 5 477) Fax: + (202) (3337 0 931) E-Mail: [email protected], [email protected], [email protected]


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The entropy term ∆S mix reflects the energy change associated with change in molecular arrangements. The magnitude of the entropy change is essentially an inverse function of the molecular weight of the polymers being mixed. The higher the molecular weight, the lower the num-ber of possible arrangements is available to the segments of the covalently linked molecules. The simplest system to consid-er is a mixture of nonpolar polymers. Be-cause they are generally more attracted to themselves than to other polymers, ∆Hmix is positive, T∆Smix must be greater than ∆Hmix in order for the Gibbs free energy of mixing ∆Gmix to be negative. However, because ∆Smix is usually low for high mo-lecular weight polymers, it is rarely suffi-cient to overcome the positive enthalpic contribution, and the Gibbs free energy of mixing is therefore positive. Thus, ther-modynamics does not favor miscibility in nonpolar polymers, and miscibility is more favored in blends of low molecular weight polymers than in blends of high molecular weight polymers.

When mixing polar polymers, the thermodynamic arguments are slightly

different than those for mixing nonpolar polymers. Polar molecules may contain different functional groups, which at-tract each other upon blending. This sat-isfies the requirements for miscibility and explains why most of miscible poly-mer blends comprise polar polymers. The specific interaction capable of inducing polymer miscibility includes dipole-di-pole interaction, ion-dipole interaction, hydrogen bonding, acid-base reaction or charge transfer [4].

Classifications of polymer blends [5-7]During the last decade much attention has been paid to the development and investigation of binary polymer blends. Generally, the polymer blends can be di-vided into completely compatible, in-compatible, and semi-compatible. Up till now, there are many reports on the com-patibility of polymer blends. It was found that the miscibility of polymer blends is strongly affected by many factors such as molecular weight, chemical structure, sample preparation, compositions, crys-tallization temperature, and pressure. This classification includes:

a) Totally compatible blends Compatible blends are polymer mixtures when it does not exhibit gross symptoms of polymer segregation and having inter-mediate physical properties of the com-ponents. They exhibit strong attraction between the blend constituents, gener-ally, arising from interaction between the functional groups of the polymers (OH, CN, CH2OH, COOH, CH3 ...).

A totally compatible polymer blend consists of only one single phase. On a molecular level, molecules of polymer (A) intermingle with polymer (B) molecules as shown in Figure 2a. in a compatible one-phase blend of two amorphous pol-ymers, no domains are present to refract light, and hence the blend may be trans-parent. Also compatible blend has one glass transition temperature (Tg). There-fore in compatible blends, some attrac-tion forces between the two polymers must be present to partially overcome the intermolecular cohesive forces of the individual polymer molecules.

b) Incompatible blendsHowever, most of the useful polymers are almost incompatible at a molecular level. Even if they are mechanically blended af-ter being melted, they soon exhibit phase separation, i.e. polymer (A) forms a sepa-rate phase with polymer (B) Figure 2b. Therefore incompatible blends show two distinct glass transitions which are similar to those of the constituent polymers.

c) Semi-compatible blendsA blend of two polymers is neither totally compatible nor totally incompatible, but falls somewhere in between. Partially compatible polymers may form com-pletely miscible blends when either poly-mer is present in small amounts. In par-tially compatible polymer blends, the phases may not have a well-defined boundary, since polymer (A) molecules can significantly penetrate into the poly-mer (B) phase and vice versa, as depicted in Figure 2c.

Characterization techniques for blend compatibilityVarious methods were used to study the compatibility of polymer blends.

Heat of mixing (∆Hm)The calculation of heat of mixing is con-sidered to be a tool for determination of the degree of compatibility between pol-ymer blends [8]. It was noted that the polymer compatibility in the solid state

Fig. 1: Homogeneity on a macroscopic level and a single bulk pro-perty profile exhibited by alloys and blends.

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Fig. 2: Morphologies of the blend of polymer (A) and (B); (a) compatible (b) incompatible and (c) semi-compatible.

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might occur if the heat of mixing is below 41.85x10-3 joule/mole. The heat of mix-ing was calculated for the systems under investigation using the following equa-tion:

∆Hm = {X1M1ρ1 (δ1-δ2)2[X2/(1- X2) M2ρ2 + (1-X1) M1ρ1] 2} ½

Where X, ρ and M are the weight fraction of polymer, density and monomer unit molecular weight respectively, δ is the solubility parameter of the polymer.

Differential scanning calorimetry method (DSC) [9&10]The thermal analysis technique yields a plot of the differential heat absorbed or dissipated by the sample compared with a reference. The temperatures of both samples and reference are raised at a constant rate. The increase in the specific heat of the polymer is accompanied by an increase in molecular motion. With one phase blends, only one glass transition temperature (Tg) is observed at a temper-ature which lies between that of the component polymers. In case of phase separation, two Tgs are located in the same position for the component poly-mers.

Viscosity [11-17]Viscosity techniques have been applied to investigate the compatibility of polymer-ic blends in dilute solutions. The nature of viscosity of dilute polymer solutions is based on analyzing hydrodynamic prop-erties related to the movement of macro-molecules in solutions. The two phase structures of polymer mixtures and deformation of drops in flow mixture de-pends not only on the component ratio but also on the value of the viscosity, which is estimated from the degree of deviation of viscosity from the initial vis-cosity. The type of compatibility of the polymer blends can be deduced as fol-lowing:

C ][K ][ C) / ( 2sp ηηη +=

Where ηsp is the specific viscosity, C is the the concentration in g/100 ml, η is the intrinsic viscosity and K is a constant. A linear relation ship is obtained by plot-ting ηsp / C against the concentration C. From the intercepts of these lines with the y axes, the intrinsic viscosity η can be obtained. The plot of, η versus the blend compo-sition gives an idea about the compatibil-

ity of the investigated blend. Linear rela-tion denotes good compatibility, while deviation from linearity indicates semi or incompatible blends.

Ultrasonic velocity method [12&18]Ultrasonic techniques have become very valuable tool for the study of the degree of compatibility of blend systems. In com-patible blends, the longitudinal ultrason-ic velocity varies linearly with composi-tion, while it deviates from linearity in incompatible polymer blends.

Microscopy [19-21]Microscopy is a useful tool to determine whether a blend is single or multiphase. Microscopy is best applied to system, where the phases can be differentiated from one another by chemical or physical treatment such as staining or solvent swelling. There are three general meth-ods of observing samples: light microsco-py, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).

Dielectric relaxation method [22] Phase separation in polymer blends can be detected by means of dielectric relax-ation method. As the different relaxa-tion process of the different component of the blend can be detected simultane-ously at the same measuring tempera-ture. The plot of permittivity vs. blend composition one can detect the behav-ior of the blend i.e. if a linear relation-ship is found this means that the blend is compatible.

Dynamic mechanical method [23]In this technique a dynamic modulus can be measured as a function of tempera-ture over a range of frequencies. The curves show only one or two peaks repre-senting the glass transitions for compati-ble and incompatible respectively.

Infra red spectroscopy [18]Infra red spectroscopy has considerable potential for studying complex multi-component system such as compatible blends.

Gas chromatography [24]Gas chromatography technique was used to study polymer structure; as well as polymer blend compatibility. The compat-ibility of blends depends on the specific properties of polymers, such as cohesion energy and average number molecular weight.

Nuclear magnetic resonance spectroscopy [25] The use of Nuclear magnetic resonance (NMR) in study of vulcanized filled elas-tomer blends has been limited owing to line broading of the spectra.

X-ray spectroscopy [25]X-ray method was used to measure the degree of crystallinity of the polymer blends. The method depends on the size of the domain which is necessary to give characterize X-ray patterns.

Differential thermal analysis (DTG)Differential thermal analysis DTA is used to study the thermal behaviour of the blend. Thermal spectrometry measures the heat-energy change occurring in a substance as a function of temperature.

CompatibilizersStable polymer blends might be pro-duced from immiscible polymers by us-ing compatibilizers. Just as a surfactant can stabilize oil- water mixtures, it should be possible to enhance the stabil-ity and properties of an immiscible poly-mer blends by adding a compatibilizing polymers, usually a block or graft copoly-mer [7]. Compatibilizers can be classified into

Crosslinking agentsThe addition of low molecular weight compounds in a polymer blend may pro-mote miscibility through the formation of copolymers (random, block, graft) or through the combined effects of copoly-mer formation and cross-linking. Low molecular weight compounds such as peroxides are usually added at relatively low concentrations (typically 0.1 to 3 wt %). Thus, they may offer economic ad-vantages vs. polymeric compatibilizers that are usually [26-28] effective at high-er concentration.

Blend composition, type and concen-tration of curing agent are of importance in producing a variety of (hard) and (soft) thermoplastic elastomers. It is believed that phase separation in these systems is inhibited by the presence of inter-crosslinked morphology with good inter-phase bonding. Such morphology is as-sumed to be present in various cure compatible” blends such as) styrene butadiene rubber/butadiene rubber (SBR/BR), natural rubber/butadiene rub-ber (NR/BR), etc. [7, 29 & 30] based on components having approximately equal cure rates. Good properties may also be



obtained by a slow overall rate of cure that favors overlapping and interdiffu-sion [31&32].

CopolymersThe copolymers may be block or graft copolymers. The block and graft copoly-mers can be prepared by the action of active chemicals or high energy radiation in presence of monomers [26, 32-34]. The formation of block and graft copoly-mers involves the attachment of the chains of two (or more) different poly-mers to give a single product. If chains are combined at their ends, the product is a block polymer (Figure 3a), if the chain ends of one polymer are attached along the chain of the other polymer, the prod-uct is graft copolymer (Figure 3b).

Advantages of compatibilizers ■ Reduce the interfacial energy be-

tween phases. ■ Permit a finer dispersion during mixing. ■ Provide measure of stability against

gross segregation. ■ Improve interfacial adhesion. ■ Decrease the size of phase domains. ■ Improve physical properties, thermal

stability and influence dynamic prop-erties.

New trends in polymer blendsShokri et al [35] used phthalic anhydride (PAH), succinic anhydride (SAH) and ma-leic anhydride (MAH) as compatibilizers in acrylonitrile butadiene rubber/poly (vinyl chloride) blends for improvement of interfacial interaction, mechanical properties and processability of polymer blends. It was found that the incorpora-tion of compatibilizing agents has a good effect on the improvement of mechani-cal properties and swelling behavior of these blends, which is evident from high-er stabilization torque and tensile strength, reduced swelling index and in-frared spectroscopic studies of blends.

Morphology study of tensile fractured surfaces indicates the improvement of interfacial adhesion between NBR and PVC phases in the presence of compatibi-lizing agent. From these compatibilizing agent MAH has a good effect on PAH and SAH. Also, in this work the effect of mix-ing of NBR form (powder and bale) on the final properties of NBR/PVC blends were investigated.

The effects of polypropylene maleic anhydride (PPMAH) as a compatibilizer on the mechanical and morphological properties of polypropylene (PP)/ recy-cled acrylonitrile butadiene rubber (NBRr)/ empty fruit bunch (EFB) compos-ites were studied [36]. Composites were prepared through melt mixing using heated two roll mill at 180 °C for 9 min-utes and rotor speed of 15 rpm. NBRr loading were varied from 0 to 60 phr and PPMAH was fixed for 5 phr. The compos-ites were moulded into a 1 mm thin sheet using hot press machine and then cut into dumbbell shape. The mechanical and morphological properties of com-posites were examined using universal tensile machine (UTM) and scanning electron microscope (SEM), respectively. Tensile strength and Young’s modulus of PP/NBRr/EFB composites decreased with increasing NBRr loading, whilst increas-ing the elongation at break. However, PPMAH compatibilized composites have resulted 27% to 40% and 25% to 42% higher tensile strength and Young’s mod-ulus, respectively, higher compared to uncompatibilized composites. This was due to the better adhesion between PP/NBRr matrices and EFB filler with the presence of maleic anhydride moieties. From the morphological study, the mi-crograph of PPMAH compatibilized com-posites has proved the well bonded and good attachments of EFB filler with PP/NBRr matrices which results better ten-sile strength to the PP/NBRr/EFB com-posites.

Chuanhui and his coworkers [37] studied the compatibilization between polypropylene (PP) and acrylonitrile butadiene rubber (NBR) by using maleic anhydride grafted polypropylene (MA-g-PP) as a compatibilizer in the presence of zinc dimethacrylate (ZDMA). It was ob-served that ZDMA increased the interfa-cial bonding between NBR and PP ma-trix. Incorporation of MA-g-PP further increased the mechanical properties of the resultant blends. The morphology analysis, dynamic mechanical analysis (DMA) and crystallization behavior study indicated that incorporation of MA-g-PP would change the polarity of the PP phase, facilitating more ZDMA diffusing from NBR into the PP phase during melt mixing. As a result, the possible creation resulted from polymerization of ZDMA combined with MA-g-PP increased the interface adhesion and compatibility be-tween PP and NBR phases, which con-tributed to the considerable improve-ment in mechanical properties of the re-sultant blends. Moreover, we found that MA-g-PP did not influence the size of the crosslinked NBR phase, but significantly improved the viscosity of the resultant materials.

Poly(trimethylene-terephthalate)/acrylonitrile-butadiene-styrene (PTT/ABS) blends by melt processing with and without epoxy or styrene-butadiene-ma-leic anhydride copolymer (SBM) as a re-active compatibilizer were Prepared by Xue et al [38]. In the presence of the compatibilizer, both the cold crystalliza-tion and glass transition temperatures of the PTT phase shifted to higher tempera-tures, indicating their compatibilization effects on the blends. The SEM micro-graphs of the epoxy or SBM compatibi-lized PTT/ABS blends showed a finer mor-phology and better adhesion between the phases.

Polypropylene (PP)/poly(acryloni-trile-butadiene-styrene) (ABS) blends

Fig. 3: The basic structure of multicomponent polymer, (a) block polymer (b) graft copolymer.

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containing montmorillonite (MMT) com-patibilized with polypropylene-grafted maleic anhydride were prepared [39] by melt extrusion using twin screw extruder followed by injection molding. Mechani-cal properties were evaluated through tensile, flexural, and impact testing. The microstructure and formation of nano-composites were assessed by scanning and transmission electron microscopy and X-ray diffraction (XRD). Incorporation of polypropylene-grafted maleic anhy-dride and MMT into PP/ABS blend led to higher strength and stiffness but at the expense of toughness. Scanning electron micrographs revealed a fine and homoge-neous dispersion of ABS phase in PP ma-trix. Both XRD and transmission electron microscopic analysis revealed the forma-tion of intercalated clay silicate layer in PP/ABS nanocomposites.

As’Habi et al [40] investigated the ef-fect of nanoclay addition on rheological, thermal stability, crystallization and morphological properties of the nano-composites and compared with those of the neat polyamide 6 (PA6) and sty-rene-butadiene-acrylonitrile (ABS) blends through a one step melt mixing process. The nanoscale dispersion of the clay layers in the blends were confirmed through X-ray diffraction and transmis-sion electron microscopy methods. Rheo-logical investigation indicated an in-creased viscosity and melt elasticity for the nanocomposite systems. The viscosi-ty of nanocomposites followed a shear thinning flow behavior and decreased with increasing shear rates. The changes in the rheological properties were ac-companied by refinement of the co-con-tinuous morphology. For thermal degra-dation under nitrogene atmosphere, the onset and maximum of degradation temperatures for the nanocomposites were as high as the neat blends, while significant improvement in thermal sta-bility (about 60 °C by 3 wt. % clay addi-tion) was observed in the air environ-ment. In addition agglomerated clay par-ticles did not significantly affect thermal stability of the polymer matrix. Non-iso-thermal crystallization results indicated that the clay layers had a retarding effect on the crystal growth rate and facilitated the formation of α crystalline form. In addition no nucleation effect was ob-served during the crystallization process due to incorporation of nanoclay into the blends.

Botros and Moustafa [41] prepared acrylonitrile-co-styrene-co-methylmeth-

acrylate (AN-S-MMA) terpolymer as com-patibilizers in butadiene - acrylonitrile rubber (NBR)/ethylene propylene diene monomer rubber (EPDM) blends and into chloroprene rubber (CR)/EPDM blend and found that the terpolymers im-proved the compatibility of CR/EPDM and NBR/EPDM blends.

Waste polyethylene (WPE) was segre-gated from the municipality solid waste, cleaned, dried, and chopped into pieces, then processed in a Brabender Plasti-corder using the melt mixing technique. Blends of WPE and virgin polyethylene were prepared in various proportions under optimized process conditions. Of the various blend proportions studied, 70/30 blend of WPE/low density poly-ethylene (LDPE) and 50/50 blend of WPE/high density polyethylene showed better mechanical properties and hence select-ed for further modification involving electron beam irradiation. Aforemen-tioned blends were exposed to various doses of electron beam irradiation and the effect of irradiation on physical me-chanical properties such as tensile strength, flexural modulus, hardness, and impact resistance were studied. Thermogravimetric analysis, X-ray dif-fraction studies, Fourier transform infra-red spectroscopy, scanning electron mi-croscopy, and gel content were consid-ered to characterize the blends. Physical mechanical properties improved to an appreciable extent on irradiation but the elongation at break reduced drastically. Blow molding of the 70/30 WPE/LDPE blend could be done successfully to make bottles [42].

Waste polyethylene (WPE) was melt blended with reclaim rubber (RR) in dif-ferent proportions were prepared and characterized by Satapathy et al [43] in presence as well as in absence of a si-lane-coupling agent (Si-69). Tensile strength, flexural strength, flexural mod-ulus, impact strength and hardness prop-erties of the blend was found to be im-proved in presence of Si-69.

Kudva et al [44] used an imidized acrylic (IA) polymer and a styrene/acry-lonitrile/maleic anhydride (SANMA) ter-polymer as compatibilizing agents on the blends of nylon 6 and acrylonitrile–butadiene–styrene (ABS). In general, the ductile-to-brittle transition temperature of blends containing high IA contents increase more rapidly with the number of extrusions than at lower IA contents. High IA content blends exhibited signifi-cant changes in morphology with in-

creased number of extrusion steps; some of the ABS domains became larger, lead-ing to a poorer dispersion of rubber par-ticles. Blends containing the IA polymer developed higher melt viscosities than blends containing the SANMA polymer (particularly at higher IAcontents), since the nylon 6/IA reaction appears to con-tinue with increasing processing time, whereas the nylon 6/SANMA reaction does not. They found that SANMA mate-rial is a more attractive compatibilizer than the IA polymer, particularly at high-er compatibilizer contents.

To overcome drawbacks of the nylon 6/poly (acrylonitrile-co-butadi-ene-co-styrene) (ABS) blend, nylon 6 blend with poly (acrylonitrile - co-styrene - co-acrylic rubber) (ASA) which contain-ing poly (butyl acrylate) as a rubber phase in substitute of poly (butadiene) in ABS, was examined. Poly (styrene-co-ma-leic anhydride) (SMA) containing 25 wt% of maleic anhydride (MA) or poly (sty-rene- co-acrylo-nitrile-co-maleic anhy-dride) (SANMA) containing less than 3 wt% MA was used as a compatibilizer to fabricate blends having high impact strength. Changes in the mechanical properties of nylon 6/ASA blend with compatibilizer content were similar with those of nylon 6/ABS blend. Blends hay-ing high impact strength was produced when blends contained more than about 20 wt% rubber. Blends containing SAM or SANMA as a compatibilizer were stayed in a injection molding machine at the molding temperature and afterwards specimens for the examination of the impact strength was prepared. Impact strength of blends containing SMA was decreased with retention time, while that of blends containing SANMA was not changed with retention time [45].

Zhang et al [46] studied the effect of Maleic-anhydride modified Ethylene–Propylene–Diene rubber (EPDM) (MAH-EPM) as a compatibilizing agent for natu-ral rubber (NR)/butadiene rubber (BR). The addition of 5 phr of MAH-EPM im-proved tensile and tear strength when compared to a straight NR/BR/EPDM blend. These improvements can mainly be attributed to a compatibilizing effect of MAH-EPM, resulting in a more homo-geneous phase distribution.

The effectiveness of maleic anhydride grafted ethylene propylene diene mono-mer rubber (EPDM-g-MAH) as an interfa-cial compatibilizer in enhancing the ex-tent of interaction between natural rub-ber (NR) matrix and organoclay (OC) nan-



olayers, and also the eventually developed microstructure during a melt mixing process, has been evaluated as an alternative material to be used in place of commonly used epoxidized NR with 50 mol % epoxidation (ENR50). The latter usually weakens the processability of the final compound. The curing behavior, rheological, and dynamic mechanical properties of the prepared nanocompos-ites have been evaluated. Microstructur-al characterizations revealed better in-terfacial compatibilization by EPDM-g-MAH than ENR50, which is attributed to the lower polarity of the EPDM-g-MAH and hence more affinity for the NR ma-trix to be diffused onto the galleries of OC. This was confirmed with transmis-sion electron microscopy (TEM) examina-tion and higher elasticity exhibited by the unvulcanized NR/OC/EPDM-g-MAH nanocomposites in melt rheological measurements. Also, lower damping be-havior was observed for the vulcanized NR/OC/EPDM-g-MAH samples. These imply intensified polymer–filler interfa-cial interaction and hence restricted vis-cous motions by the NR segments. Vul-canized NR/OC nanocomposites compat-ibilized with EPDM-g-MAH showed

greater enhancements in tensile proper-ties than the sample compatibilized with ENR50 [47].

Styrene butadiene rubber (SBR) and epoxidized natural rubber (ENR) blends were compatibilized by styrene-(epoxi-dized butadiene)-styrene triblock copoly-mer (ESBS) investigated by Ismail and Hairunezam [48]. The results indicate that the increasing content of ENR and the presence of ESBS improve processa-bility, tensile strength, tear strength and tensile modulus of SBR/ENR blends. Also the presence of ESBS in SBR/ENR blends resulted better oil resistance than the similar blends without ESBS.

Halimatudahliana et al [49] studied morphology of uncompatibilized and compatibilized polystyrene/polypropyl-ene (PS/PP) blends with 20/80, 50/50 and 80/20 (wt. %). Various compatibiliz-ers, viz. polystyrene-block-poly(ethyl-ene-butylene)-block polystyrene (SEBS), ethylene vinyl acetate (EVA) and sodium salt hydrate of 4 styrene sulfonic acid with concentration 7.5% w/w were em-ployed. The etched surfaces of uncom-patibilized and compatibilized blends were analyzed by a scanning electron micrograph (SEM) as shown in Figure 4.

For all blend compositions, the micro-graphs indicate a multiphase system for the PS/PP blend. The incorporation of SEBS into the PS/PP blends resulted in a finer degree of dispersion of particles together with morphological evidence of interfacial adhesion. EVA showed higher plastic deformation.

Noriman et al [50] studied the effects of epoxidized natural rubber (ENR-50) as a compatibilizer on the properties of sty-rene butadiene rubber/recycled acryloni-trile-butadiene rubber (SBR/NBRr) blends. The cure characteristics showed that SBR/ NBRr blends with the presence of ENR-50 have lower scorch time t2 and cure time t90 than SBR/NBRr blends with-out ENR-50. The SBR/NBRr blends with ENR-50 exhibited lower minimum torque (ML) compared with SBR/NBRr blends without ENR-50, which indicates better processability of the blends after com-patibilization. However, SBR/NBRr blends with ENR-50 exhibited a higher value of maximum torque (MH) than SBR/NBRr blends without ENR-50. The incorpora-tion of ENR-50 improved the tensile strength and tensile modulus (M100, stress at 100% elongation) of SBR/NBRr blends with ENR-50 compared with SBR/ NBRr blends without ENR-50 at all blend ratios. Nevertheless, the addition of ENR-50 reduced the elongation at break (Eb) and rebound resilience of compatibilized SBR/NBRr blends compared with SBR/NBRr without ENR-50. The improvement in hardness upon compatibilization is due to an increase in crosslink density. FTIR analysis showed that ENR-50 is compatible with NBRr. Differential scan-ning calorimetry results show an im-provement in the compatibility of SBR/NBRr blends with the presence of ENR-50. Scanning electron microscopy (SEM) of the fracture surfaces indicates that, with the addition of ENR-50 in SBR/NBRr blends; better adhesion between SBR and NBRr was obtained, thus improving the compatibility of SBR/ NBRr blends.

Epoxidized natural rubber (ENR50) and two different kinds of organoclay (C30B and C15A) were used in blends of styrene-butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR) and their effects upon interaction between phases, morphology, and mechanical properties of the blends were investigat-ed. The compounds were characterized by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron micros-

Fig. 4: Morphology of 80/20 PS/PP blends (a) without and (b) with the addition of 7.5% w/w SEBS as a compatibilizer.

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Fig. 7: SEM micro-graphs of: (a) SBR/LLP-DE blend (50/50), (b) SBR LLPDE blend (50/50) loaded with 2.5 phr MAH, (c) SBR/LLPDE blend (50/50) loaded with 20 phr rice husk &2.5 phr MAH and (d) SBR-LLPDE blend (50/50) loaded with 20 phr rice husk & 5 phr MAH.

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copy (FE-SEM), and differential scanning calorimetry (DSC). The obtained results showed formation of hydrogen bonding between the compounds ingredients due to incorporation of C30B, especially in presence of ENR. AFM and FE-SEM analysis revealed good dispersion of the nanoparticles in the polymer matrix up-on addition of ENR as well as better dis-persion of C30B than C15A in the NBR phase. XRD results showed a greater ex-pansion of the silicate layers by simulta-neous use of organoclay and ENR Incor-poration of organoclay alone or in combi-nation with ENR in the blends caused shifting of the SBR Tg toward the NBR Tg. The tensile properties of the blends showed improvement by using nanopar-ticles in the presence of ENR [51].

Khalf and Ward [52] studied the effect of maleic anhydride (MAH) as a compati-bilizer on the physical-mechanical as well as dielectric of styrene butadiene rubber (SBR)/linear low density polyeth-ylene (LLDPE) 50/50 filled with rice husks. Increasing MAH concentrations in SBR/LLDPE blends resulted in an increase in the tensile strength, elongation at break and hardness. The scanning electron mi-croscopy (SEM) indicates that the pres-ence of MAH increases the interfacial in-teraction between SBR/LLDPE blends.

The oil extended natural rubber (OENR) and HDPE blends with different rubber–plastic components (i.e., OENR/HDPE = 0/100, 20/80, 30/70, 40/60, 50/50, 60/40, 70/30, 80/20 and 100/0) were prepared by Pechurai et al [53]. They studied the effect of blend compat-ibilizer (i.e., phenolic modified polyethyl-ene, PhHRJ-PE) on the blends of OENR/HDPE. It was found that the blend with compatibilizer exhibited higher flow and viscosity curves as well as mechanical properties in terms of 100% modulus, tensile strength and elongation at break. SEM micrographs and rheological prop-erties indicated that the blends of OENR/HDPE are two-phase systems (i.e., sepa-ration of rubber and plastic phases). The component with the lower proportion was found to be a dispersed phase in the major continuous matrix phase. Co-con-tinuous phase morphology was also ob-served in the blend with the blend ratios of OENR/HDPE = 50/50 and 60/40, where the materials behave as thermo-plastic elastomers.

Thermoplastic elastomers (TPEs) based on high-density polyethylene (HD-PE)/waste ground rubber tire (WGRT) powder composites were prepared by

melt compounding, and the composites were compatibilized by styrene–butadie-ne–styrene block copolymer (SBS). The effects of the SBS compatibilizer on me-chanical properties, morphological pro-perties and the Mullins effect of the composites were investigated systemi-cally. Experimental results indicated that SBS had a good compatibilization effect on the HDPE/WGRT composites. Compa-red with HDPE/WGRT composites, the tensile strength and the elongation at break went through maximum values at a compatibilizer resin content of 12 phr. Morphological study showed that the interface interaction of the HDPE/WGRT composites compatibilized by SBS was strong, which contributed to the signifi-cantly improved mechanical properties. The Mullins effect results showed that the softening appeared after the first loading of the HDPE/WGRT and HDPE/SBS/WGRT composites, the maximum stress decreased at the later cycles, and the residual deformations in uniaxial loading–unloading cycles of the HDPE/SBS/WGRT sample were lower than tho-se of the HDPE/WGRT sample, indicating that the elasticity of the HDPE/SBS/WGRT TPE was improved [54].

EL-Nashar and Turky [55] used low molecular weight compound such as di-vinyl benzene (DVB) to enhance the physico-mechanical properties, morpho-logical characteristics and dielectric properties of Natural rubber (NR) / Acry-lonitrile rubber (NBR) 50/50 blend. Abd-El-Messieh et al [56] prepared polyester based on the glycolyzed prod-ucts of PET and added in different con-centrations to a series of SBR/PVC blends.The addition of the polyester showed that all properties of SBR/PVC blends were improved. Highest mechanical strength values were obtained at a poly-ester concentration of 7.5 phr. Blends were showed good thermal stability. Thermal analysis as well as dynamic me-chanical properties of SBR/PVC blends after the addition of 7.5 and 10 phr poly-ester indicated one single glass transi-tion temperature. This means that the compatibility of SBR/PVC blends was greatly enhanced. These results con-firmed by dielectrical properties and find further justification through the micro-structure analysis carried out by using scanning electron microscope.

Compatibility of NBR/NR blends was studied by El- Nashar et al [57]. It was found that these blends are incompati-ble, science the calculated heat of mixing

(ΔHm) lies above the upper limit of com-patibility. The use of tetrachloro phthalic anhydride (TCPA) as a compatibilizer en-hance the dielectric and mechanical properties and increase flame resistance of the blends, which could be very useful in electric applications as in cables, wires and insulating purposes.

Shojaei and Faghihi [58] studied the effect of organoclay (OC) on the perfor-mance of styrene-butadiene rubber (SBR)/phenolic resin (PH) blend .It was found that the OC is mainly localized in the SBR phase of SBR/PH blend through the kinetically favored mechanism rele-vant to rubber chains. The results also demonstrated the positive role of PH on the dispersion of OC. Both PH and OC showed accelerating role on the cure rate of SBR and increased the crosslinking density of the rubber phase. Additionally, the mechanical and dynamic mechanical properties of SBR were influenced by in-corporation of both PH and OC. TGA showed that the OC improves thermal stability of SBR vulcanizate, while it ex-hibits a catalytic role in presence of PH.

Kim and Kim [59] investigated the miscibility behavior of melamineformal-dehyde (MF) resin and poly (vinyl ace-tate) (PVAc) blends for their use as adhe-sives for bonding fancy veneer and ply-wood in engineered flooring. They pre-pared blends of various compositions of MF resin/PVAc to determine and com-pare the effect of PVAc content, blends with PVAc to MF resin weight ratios of 0, 30, 50, 70 and 100%. These blends dis-played a single cure temperature over the entire range of compositions indicat-ing that this blend system was miscible in the amorphous phase due to the for-mation of hydrogen bonding between the amine groups of the MF resin and the carbonyl groups of PVAc.

Liau et al [60] investigated the misci-bility and crystallization behavior of bi-nary crystalline blends of poly (butylene terephthalate) [PBT] and polyacrylate based on Bisphenol A and a 27:73 mole ratio of isophthalic and terephthalic ac-ids by differential scanning calorimetry (DSC). This blend system exhibits a single composition-dependent glass transition temperature over the entire composition range. These indicate that the blends are thermodynamically miscible in the melt.

Si and his co works [62] studied the morphology of blends of polystyrene/poly (methyl methacrylate) (PS/PMMA), polycarbonate /poly(styrene-co-acryloni-trile) (PC/SAN), and poly(methyl meth-



acrylate) / ethylene vinyl acetate ( PM-MA/EVA) and compared the morpholo-gies with and without modified organo-clay Cloisite 20A or Cloisite 6A clays.

PC/ SAN /PMMA blends with a varied content of PMMA were studied. The pre-pared blends were evaluated by TEM mi-croscopy, Uniaxial tensile testing and in-strumented macro-hardness indenta-tionwere, indentation modulus, elastic and plastic deformation work during in-dentation. The data was correlated with the morphology. In case PMMA is the minor phase, it tends to locate on the PC/SAN interface; whereas in case of being the major one, SAN plays the role of com-patibilizer and encapsulates the PC parti-cles. Good compatibility of the blends was confirmed by the results of mechan-ical testing, which revealed strain-con-trolled plasticity.

Khalaf et al [63] studied the effect of adding of 5% hydrolyzed poly (ethyl-ene-covinyl acetate) (EVAOH), itaconic anhydride (naturally obtained during fer-mentation of sugars (It.anhydride)), and mercapto-modified ethylene-co-vinyl ac-etate (EVASH) as compatibilizers on the mechanical properties before and after thermal oxidative aging at 90˚C for dif-ferent time periods up to 7 days, electri-cal properties, and morphology of ethyl-ene propylene diene monomer/ethylene vinyl acetate (EPDM/EVA) blends of dif-ferent compositions (75/25, 60/40, 50/50, and 25/75, respectively).

The effect of polymer-polymer inter-actions on the miscibility of polyvinyal-cohol /poly(methyl methacrylate) (PVC /PMMA) and polystyrene /poly(methyl methacrylate) (PS/PMMA) blends were studied in a broad composition range using viscosity and Infrared Spectroscop-ic Analysis (FTIR) techniques by Khan [64]. Both techniques pointed out the existence of interaction between PVC and PMMA in both, solution and solid state. However, in the case of PS/PMMA blend no interaction was shown, even it failed to identify any perturbation of the ether lone-pair electron of PMMA and the benzene ring vibration of PS as a re-sult of blending the PS and PMMA. This means that both the polymers are im-miscible.

Dikobe and Luy [65] prepared the blend of Polypropylene (PP) with ethyl-ene vinyl acetate copolymer (EVA) to form PP/EVA polymer blends. Wood pow-der (WP) was mixed into these blends at different weight fractions (50/50/0, 45/45/10, 40/40/20, 35/35/30 w/w PP/

EVA/WP) to form PP/EVA/WP blend com-posites. The scanning electron microsco-py (SEM) and differential scanning calo-rimetry (DSC) results confirm the immis-cibility of EVA and PP in the blends, and show that WP is primarily concentrated in the EVA phase. DSC results further show that the EVA crystallization behav-ior is significantly influenced by the pres-ence of WP. Dynamic mechanical analy-sis (DMA) results confirm immiscibility of PP and EVA, as well as an interaction be-tween EVA and WP. Interaction between EVA and WP was further confirmed by Fourier-Transform infrared spectroscopy (FTIR).

Reffaee et al [66] studied the electrical and mechanical properties of NBR/SBR blends with different compositions. The electrical as well as the mechanical prop-erties were carried on NBR, SBR and NBR/SBR blend (50/50) to be loaded with different concentrations of high abrasion furnace black (HAF) . The elec-trical conductivity of carbon-black-filled composites is increased from pure poly-mer to that of pure carbon, through the change in the different composites. Up till certain concentration of HAF (30 phr for both NBR and SBR) and 20 phr for NBR/SBR blends the conductivities of the composites are approximately the same and closed to that of the pure. The me-chanical properties, which investigated through the measurements of tensile and elongation indicate an increase at the same concentration of HAF found in the case of electrical measurements. This result gives evidence to the good applica-bility between both mechanical and electrical investigations through the net-work formations.

Filling effect of silica on dielectric and mechanical properties of ethylene pro-pylene diene/acrylonitrile butadiene rubber EPDM/NBR blends with different compositions was studied by Eid and El-Nashar [67]. To solve the problem of phase separation polyvinyl chloride (PVC) with concentration 10 phr was added. The study led to a conclusion that the blend 75/25 EPDM/ NBR possesses the most promising properties. This blend was chosen to be loaded with silica in increasing quantities up to 90 phr, the resuls indicate that the EPDM / NBR blend loaded with 50–60 phr of silica possess the most suitable electrical and mechanical properties.

A tire thread formulation for heavy-duty trucks containing sty-rene-butadiene rubber/butadiene rub-

ber (SBR/BR) blend and varying propor-tions of silica/clay fillers have been inves-tigated by Ogbebor et al [68]. Substitu-tion of silica (80 phr) with china clay up to ( 40 phr ) increased the cure rate of the rubber blend mixes as well as their max-imum torque level (Tmax). Tmax was ob-served to be highest at a filler blend ratio of 40/40 phr. The heat buildup was re-duced from 43 to 20°C as the clay con-tent increased. Results also showed that the rubber blend compound containing silica/clay (60/20) filler blend in the stat-ed ratio exhibited the best properties, and abrasion resistance.

Perez and his co works [69] used fillers (mesoporous silica and a precipitated silica) as compatibilizers and found that NBR is preferentially located at the silica surface improving its dispersion, larger rubber/filler as well as SBR/NBR inter-phases are obtained for the blends rein-forced with the mesoporous silica, whose high surface area and organized porous structure allow a better polymer/filler interaction, and also the reinforced blends present higher strength at break than each reinforced polymer alone. The best performance is attained for blends reinforced with mesoporous silica.

The synthesis of novel modified mi-cronized phosphate pigments as rein-forcing materials for the vulcanizates of styrene-butadiene rubber (SBR), natural rubber (NR) and their blends studied by El-Nashar et al [70]. The results showed that, phenyl phosphate pigments exer-cised a great effect on the rheological characteristics (scorch time, cure time…etc.), and achieved high performance and pronounced mechanical properties.

Abdul Kader and Bhowmick [71] in-vestigated the effects of fillers (carbon black and silica) on the mechanical, dy-namic mechanical and aging properties of rubber/plastic blends derived from acrylic rubber, fluorocarbon rubber, and multifunctional acrylates. The tensile and tear strengths increased with the addition of the fillers and with loading, but the elongation at break decreased, and the tension set remained unaffect-ed. The aging properties of carbon-black-filled blends were better because of the thermal antioxidant nature of carbon black. They concluded that the filler al-tered the height and half-width of the damping peak at the glass transition temperatures.

The effects of filler (Carbon black , silica and calcium carbonate) loading on the tensile and tear properties of SMR L (one



grade of natural rubber)/ ENR 25 (epoxi-dized natural rubber) and SMR L/SBR (styrene butadiene rubber) blends were conducted by Poh et al [72] by using a semi-efficient vulcanization system. Re-sults show that for the carbon black and silica-filled blends, elongation at break decreases, but tensile strength, and tear strength increase with filler loading. The reverse behavior is obtained for the calci-um carbonate-filled blends. This observa-tion is attributed to the better rubber/filler interphase interaction of carbon black and silica compared to the non-rein-forcing nature of calcium carbonate, the dilution effect of which becomes more significant as the filler loading is in-creased. For a fixed filler loading, SMR L/ENR 25 blend consistently exhibits higher tensile strength, M300 and tear strength but lower elongation at break compared to SMR L/SBR blend.

Ahmed and his co-works [73] pre-pared natural rubber (NR) hybrid com-posites reinforced with marble sludge (MS)/Silica and MS/rice husk derived sili-ca (RHS). The cure characteristics, me-chanical and swelling properties of such hybrid composite were studied. The re-sults revealed that the performance of NR hybrid composites with MS/Silica and MS/RHS as fillers is extremely better in mechanical and swelling properties as compared with the case where MS used as single filler.

Blends of acrylonitrile butadiene rub-ber/high density polyethylene (NBR/HDPE) compatibilized by chloroprene rubber (CR) were prepared. A fixed quan-tity of industrial waste such as marble waste (MW, 40 phr) was also included. The effect of the blend ratio and CR on cure characteristics, mechanical and swelling properties of MW-filled NBR/HDPE blends was investigated. The re-sults showed that the MW-filled NBR/HDPE blends revealed an increase in ten-sile strength, tear, modulus, hardness and cross-link density for increasing weight ratio of HDPE. The minimum torque (ML) and maximum torque (MH) of blends increased with increasing weight ratio of HDPE while scorch time (ts2) cure time (tc90), compression set and abrasion loss of blends decreased with increasing weight ratio of HDPE. The blends also showed a continuous reduction in elon-gation at break as well as swelling coeffi-cient with increasing HDPE amount in blends. MW filled blends based on CR provided the most encouraging balance values of overall properties [74].

Blend polymer, based on waste poly-ethylene and nitrile butadiene rubber, has been irradiated with gamma-rays, mechanically and thermally investigated at varying NBR content. Blend formation was characterized by FTIR, SEM tech-niques and also swelling behavior. Me-chanical properties like tensile strength, elongation at break and modulus at dif-ferent elongations were studied and compared with those of unirradiated ones. A relatively low-radiation dose was found effective in improving the level of mechanical properties. Differential scan-ning calorimeter and thermogravimetric analysis were used to study the thermal characteristics of the irradiated polymer. Enhancement in thermal stability has been observed for higher NBR containing blends and via radiation-induced crosslinking up to ≈ 50 kGy [75].

Markovic et al [76] studied the effect of the blend ratio of chlorosulphonated polyethylene/natural rubber (CSM/SMR 20 CV) and chlorosulphonated polyethyl-ene/chlorinated natural rubber blends in the temperature range from 120°C to 160°C using a Monsanto Rheometer. The results showed that the scorch time de-creased with increasing natural rubber and chlorinated natural rubber contents. This observation is attributed to the in-creasing solubility of sulfur, as the con-tent of natural rubber and chlorinated natural rubber in the composition in-creased. For temperatures greater than 140°C, the dependence of the scorch time on blend ratios diminishes, as enough thermal energy is available to overcome the activation energy of vul-canization. The differing curing charac-teristics of the two blends is explained by the compatibility factor of the respective blend. Morphological analysis of the blends shows a very satisfactory agree-ment.

Marković et al [77] studied the effect of N-cyclohexylbenzothiazylsulphena-mide (CBS), tetramethylthiuram disul-phide (TMTD), and 2-mercaptobenzothi-azol (MBT) on the curing characteristics and mechanical properties of vulcanized rubber blend based on natural rubber (NR) and chlorosulphonated polyethyl-ene (CSM) filled with carbon black. The results revealed that the accelerator type not only affects the cure characteristics, but also has great influence on the me-chanical properties of obtained elasto-mers. It was determined that the tensile strength of rubber blends cured in the presence of TMTD was relatively high.

Kaushik et al [78] prepared the blends of high styrene rubber (HSR) and natural rubber (NR) with nano silica using differ-ent types of carbon black. ISAF (Interme-diate Super Abrasion Furnace) type of carbon black have showed a significant effect on optimum cure time, cure rate index and mechanical properties by re-acting at the interface between HSR and NR matrix. All the samples show only one melting peak on the DSC curve; this is attributed to the same backbone struc-ture of the matrix and the carbon black reinforcement. The samples containing 30 wt % of HSR with ISAF type of carbon black has shown maximum heat build-up, lower swelling and lower compres-sion set value. Blends containing ISAF type of carbon black with 30 wt% of HSR showed high abrasion resistant proper-ties.

Maziad et al [79] prepared blends of natural rubber and low-density polyeth-ylene in different weight compositions in presence of dicumyl peroxide and maleic acid anhydride. The effects of rice husk (RH) content and a silane coupling agent, that is, 3-aminopropyl triethoxy silane (3-APE, 1 wt% of filler content) on the physicomechanical properties and mass swell of the tested blend were investi-gated. The incorporation of untreated RH into the blend improved Young’s modu-lus, hardness but decreased tensile strength, elongation at break, impact strength, and mass swell. Incorporation of 3-APE has produced composite with improved tensile strength, Young’s mod-ulus, hardness and impact strength with a sharp decrease in elongation, and bet-ter mass swell in comparison with un-treated one. The results showed that si-lane treatment increased the resistance toward γ-irradiation compared to un-treated samples. The efficiency of si-lanized RH (30 phr) showed superior crosslink density and thermal stability compared to untreated ones. In addition scanning electron microscopy (SEM) in-vestigations were found to support the previous results.

Khalf et al [80] used a graft copolymer of acrylonitrile butadiene rubber (NBR) grafted with cellulose acetate (CA) i.e. (NBR-g-CA) and acrylonitrile butadiene rubber (NBR) grafted with methylmeth-acrylate i.e. (NBR-g-MMA) by gamma ra-diation to improve of processability, in-terfacial interaction and mechanical properties of acrylonitrile butadiene rub-ber (NBR) and styrene-butadiene rubber (SBR) blends (NBR/SBR (50/50)) by The



results showed that, the blends with graft copolymer enhanced the rheologi-cal characteristics. The physical-mechan-ical properties of the investigated blends were enhanced by the incorporation of these graft copolymers, while the resist-ance to swelling in toluene became high-er. SEM photographs confirm that, these compatibilizers improve the interfacial adhesion between NBR/SBR (50/50) blend which induce compatibilization in the immiscible blends. The presence of the graft copolymer compatibilizer (i.e. NBR-g-CA and NBR-g-MMA) increased the thermal stability compared with the blend without compatibilizer.

Ethylene-propylene-diene-graft-poly-styrene (EPDM-g-PS) copolymers were syn-thesized by Pticek et al [81]. They added (5 phr) to styrene-acrylonitrile (SAN) and eth-ylene-propylene-diene (EPDM) blend (SAN/EPDM ratios 95/5 and 90/10). Opti-mal concentration of side branches of graft copolymers provide the finest mor-phology and enhance mechanical proper-ties.

Rheological and morphological prop-erties of the polypropylene (PP) and poly (styrene-co-acrylonitrile) (SAN) blend containing polypropylene-g-poly (sty-rene-co-acrylonitrile) (PP-g-SAN) was studied by Sung et al [82]. In this study the viscosity of the PP–SAN (20/80) blend showed maximum value in the 1.0 phr PP-g-SAN copolymer, which suggest-ed that the compatibilizing effect of the PP-g-SAN copolymer was achieved. From the morphological studies, the PP–SAN (20/80) blend showed droplet dispersion type morphology, and the PP droplet size showed minimum value in the 1.0 phr PP-g-SAN copolymer content. Morpho-logical and rheological studies were showed that the compatibility of the PP–SAN (20/80) blend increased more in the 1.0 phr PP-g-SAN copolymer content.

Series of various types (different structures) of ethylene-polypropyl-ene-diene-graft-polystyrene (EPDM-g-PS) copolymers were synthesized and their surface property variations were studied using surface analysis tech-niques such as surface contact angle measurement [83]. Pre-synthesized graft copolymers were added (5 phr) in sty-rene-acrylonitrile (SAN)/ethylene-propyl-ene-diene (EPDM) blends composition of 95/5 and 90/10. The adhesion parame-ters at the interface, that is work of ad-hesion, the interfacial energy and the coefficient of wetting were calculated and correlated to the differential scan-

ning measurements measurements and SEM micrographs in order to study the effect of graft copolymers on compatibil-ity of SAN/EPDM blends. It is obvious that depending of the graft copolymer’s structure, various interactions between the components in the blend will be es-tablished, resulting in better adhesion which implicates improvement of com-patibility in blends. Also, from the re-sults, it can be seen that differences in structures of the added compatibilizer are clearly reflected in the adhesion pa-rameters results, making this an accept-able method to determine whether two polymers are compatible. Morphology of the blends with the graft copolymers is significantly finer and the dispersed size is more uniformly distributed in compar-ison to the neat SAN/EPDM blend.

Nakason et al [84] prepared maleated natural rubber / polypropylene blends by a melt mixing process using graft copoly-mer of polypropylene and maleic anhy-dride (PP-g- MA), and phenolic modified polypropylene (Ph-PP) and Ph-PP as com-patibilizers at various loading levels of 3, 5, 10, 15 and 20 wt% of PP and found that the shear stress and shear viscosity increased with an increase of loading levels of compatibilizers of 0–5%. This may be attributed to the chemical inter-action between different phases of the blend caused by compatibilizers. The in-crease in chemical interaction between the interfaces caused an improvement of interfacial tension and led to decreasing size of dispersed domains of the minor phase (PP) in the MNR matrix. Increasing loading level of compatibilizers higher than 5 wt% caused a decreasing trend of the flow properties. This may be attribut-ed to the formation of micelles dispersed in the MNR matrix. Therefore, the appar-ent shear stress and shear viscosity de-creased because the micelles act as a lu-bricant in the polymer melt flow.

Ryu and co-works [85] studied the morphological, mechanical, and rheolog-ical properties of polycarbonate (PC) and poly(acrylonitrile–butadiene–styrene) (PolyABS) blends with different types of compatibilizer. Styrene–acrylonitrile–ma-leic anhydride terpolymer (SAM) and sty-rene–acrylonitrile–glycidyl methacrylate terpolymer (SAG) were used as a compat-ibilizers of the blends. For the PC–PolyABS (70/30 wt %) blends with SAM, the me-chanical strength and complex viscosity reached a maximum when the SAM con-centration was 5 phr. The mechanical and rheological results of the blend were con-

sistent with the morphological result that the PolyABS domain size reached a minimum when the SAM content was 5 phr. The interfacial tension (α) of the blend was compared with the compatibi-lizer type and content, which were calcu-lated by the Palierne emulsion model with the relaxation time of the PC–Poly-ABS blend. The α is consistent with the morphological and mechanical proper-ties of the PC–PolyABS blend. The results of the morphological, mechanical, and rheological properties of the blend sug-gest that SAM was a more effective com-patibilizer than SAG, and the optimum compatibilizer content of SAM was 5 phr.

Bertin et al [86] prepared and charac-terized virgin and recycled low-density polyethylene (LDPE) and polypropylene (PP) (LDPE/PP) blends by adding compat-ibilizing agents such as ethylene–propyl-ene–diene monomer, ethylene–propyl-ene monomer, or PE-g-(2-methyl-1,3-butadiene) graft copolymer.The elonga-tion at break and impact strength were improved for all blends. The effect of these various copolymers is quite differ-ent and is in relation with their chemical structure. The recycled blends exhibit suitable properties leading to applica-tions that require good mechanical prop-erties.

Ward et al [87] used Dielectric and viscosity techniques to determine the degree of the compatibility of poly(me-thyl methacrylate)/polycarbonate, poly(methyl methacrylate)/ polystyrene, and polycarbonate/polystyrene blends in different ratios (25/75, 50/50, and 75/25 w/w). It was found from the dielectric and viscosity measurements that the ad-dition of 10% polyester to poly(methyl methacrylate)/polycarbonate, 20% poly-ester to poly(methyl methacrylate)/poly-styrene, and 5% polyester to polycar-bonate/polystyrene blends enhanced the degree of compatibility of such blends.

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Neuer IoT-Sensor erfasst metallische Strukturen in Kunststoffen mit Mikrometerpräzision

IOT-RADARSENSOR Ondo Sen-se, Freiburg, hat einen IoT-Sen-sor entwickelt, der erstmals ei-ne ultrapräzise Erfassung me-tallischer Strukturen innerhalb von Kunststoffen oder anderen elektrisch nicht leitenden Mate-rialien ermöglicht: Die auf Ra-dartechnologie basierende Sen-sorik misst mit Mikrometer-genauigkeit Abstände zu metal-lischen Objekten, die unter anderem in Plastik, Pappe und Gummi eingebettet sind. Zu-dem werden auch Objekte er-fasst, die sich hinter diesen elektrisch nicht leitfähigen Ma-terialien befinden. Das Unter-nehmen investiert nun in die Weiterentwicklung der Techno-logie: So wird der Sensor künf-tig nicht nur die Abstandsmes-

sung metallischer Strukturen in Materialen wie beispielsweise Kunststoff oder Karton ermög-lich, sondern gleichzeitig das Material über seine relative Per-mittivität – das heißt der Durch-lässigkeit für elektrische Felder – identifizieren und klassifizie-ren. Der Vorteil: Falls Kunden Distanzmessungen zu Gegen-

ständen in verschiedenen Materialien durchführen, erfolgt die Kalibration des Systems auf das neue Ma-terial bereits während der

Messung. Die Sensortechnolo-gie ermöglicht eine Vielzahl von Einsatzmöglichkeiten in der zer-störungsfreien Inspektion von schwer zugänglichen Bauteilen oder Produkten in der Qualitäts-kontrolle oder Montage. Hierzu gehört nicht nur die mikromet-ergenaue Positionierung und Inspektion von metallischen

Objekten in Kunststoffen, Kar-ton und Gummi, sondern auch die Präsenzkontrolle von ver-deckten Bauteilen bei Produk-ten aus Verbundwerkstoffen. Auch Analysen von Materialien aus glasfaserverstärkten Kunst-stoffen auf Materialdefekte wie Lufteinschlüsse sind möglich, wie zum Beispiel an Windkraft-flügeln, laminierten Flächen oder Kunststoffbauteilen aus Spritzguss. Eine weitere Anwen-dung ist die Defektanalyse von Verpackungen in der Lebens-mittel- und Pharmaindustrie oder auch die Lebensmittelkon-trolle. n

KONTAKTOndo Sense, Freiburg www.ondosense.com

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Die cloudbasierten IoT-Sen-sorlösungen liefern Unterneh-men relevante Daten zur in-telligenten Steuerung und Re-gelung von Produktionsanla-gen und Maschinen.

Cellulosefaserverstärkung für leichtbauorientierte Anwendungen mit Bio-PPT

BIO-PPT, BIO-PBT Gebräuchli-che Kunststoffe für technische Anwendungen sind PPT und PBT. Oft werden sie als glasfa-serverstärkte Kunststoffe einge-setzt. Mittlerweile können bei-de Kunststoffe als biobasierte Variante mit einem ca. 35 %-igen Bio-Anteil hergestellt werden. Als Alternative zu Glas-fasern bieten sich die leichteren Celluloseregeneratfasern an.

Das sind chemisch aufgearbei-tete Naturfasern, die jedoch wesentlich weniger hitzeemp-findlich sind als klassische Na-turfasern. Im Verbundprojekt „Bio-PPT und Bio-PBT mit Cellu-losefaserverstärkung zur leicht-bauorientierten Verwendung in der Automobil- und Elektroin-dustrie“ untersuchten das Insti-tut für Werkstofftechnik der Universität Kassel und das

Fraunhofer-Institut für Ange-wandte Polymerforschung, Potsdam, die Verarbeitungs- und Materialeigenschaften ent-sprechender Bioverbundwerk-stoffe. Ihnen gelang es, in Zu-sammenarbeit mit Industrie-partnern Produktmuster für verschiedene Anwendungsbe-reiche mit ausgezeichneten technischen Eigenschaften her-zustellen. Für elektronische

Bauteile wurde zudem eine ha-logenfreie Flammschutzadditi-vierung ermittelt. Das Verbund-projekt wurde durch das Bun-desministerium für Ernährung und Landwirtschaft gefördert. n

KONTAKTInstitut für Werkstofftechnik der Universität Kassel, Kassel www.fnr.de

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