Mechanical Properties Of Blends Research Articles

Mechanical properties and fractal morphology of high-impact polystyrene/poly(styrene- b-butadiene- b-styrene) blends

Blends of high-impact polystyrene (HIPS) and polystyrene- b-polybutadiene- b-polystyrene block copolymers (SBS) (thermoplastic elastomers, Kraton D1101) have been studied with recycling in view. Binary HIPS/SBS elastomer systems containing up to 85% of SBS elastomer were investigated. The blends were characterized by measuring dynamic mechanical properties, creep and recovery, and by defining morphology. The heterogeneous blends exhibit a two-phase morphology. This structure is investigated by scanning electron microscopy (SEM) and compared to mechanical and processing properties as a function of SBS content. Increasing the SBS content one observes a vanishing PS-related brittle type of fracture, while an SBS-related ductile fracture emerges. Best mechanical properties are obtained for HIPS/SBS 90/10 blends. The topographical images of polymer blend fracture surfaces were processed using fractal analysis software to obtain the fractal indices of the surfaces. The average (classical) fractal index was less than two for the fracture surfaces of styrenic blends (HIPS/SBS). These fractal results were correlated with the blend mechanical properties and with the Hurst roughness exponent, obtained from the time series of processing parameters (torque, melt pressure). Hence, it is considered that the processing and mechanical results are in good agreement with the fractal properties of the fracture surfaces even for heterogeneous polymer blend materials.

Functionalization of Polyethylene with Peroxy-containing Formulations Derived from Resins Modified with Maleic Anhydride. Properties of Blends of Functionalized Polyethylene with Polyamide 6

Peroxy-containing rosin-maleic and rosin-terpene-maleic resins were prepared and grafted to low-density polyethylene macromolecules by reactive extrusion. The morphology and mechanical properties of blends of functionalized polyethylene with polyamide 6 were determined.

Natural rubber/ethylene propylene diene blends for high insulation iron crossarms

AbstractThis research studied the composition and behavior of natural rubber (NR) and ethylene propylene diene monomer (EPDM) blends at various carbon black concentrations (0–30 phr) in terms of electrical resistivity, dielectric breakdown voltage testing, and physical properties. The blends having electrical properties suitable for application in high‐insulation iron crossarms were selected for investigation of compatibility and increased physical properties. The effect of the homogenizing agent concentration on improvement of compatibility of blends was studied by scanning electron microscopy, pulsed nuclear magnetic resonance spectroscopy, and rheology techniques. We also examined mechanical properties such as tensile strength, tear strength, elongation at break, and hardness. The NR/EPDM blends filled with a fixed concentration of silica were investigated for ozone resistance. A carbon black content as high as 10 phr is still suitable for the insulation coating material, which can withstand electrical voltage at 10 kVac. Addition of the homogenizing agent at 5 phr can improve the mechanical compatibility of blends, as evidenced by the positive deviation of shear viscosity of the rubber blend, that is, the calculated shear viscosity being higher than that of experimental data. Moreover, the pulsed NMR results indicated that the spin‐spin relaxation (T2) of all three components of the rubber blend was compressed upon the addition of the homogenizing agent. The ratio of NR/EPDM in the blend to best resist the ozone gas is 80/20 with the addition of silica of 30 phr into the blend. Also, the NR/EPDM filled with silica had a decreased change in thermal and mechanical properties of blends after thermal aging. The synergistic effect of silica content and high NR content (80) in 20 phr EPDM could improve antioxidation by ozone in the absence of a normal antioxidant for natural rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3401–3416, 2004

Phase behavior and mechanical properties of blends of poly(butylene terephthalate) and poly(amino-ether) resin

The structure, thermal and mechanical properties of blends of poly(butylene terephthalate) (PBT) and a poly(amino–ether) (PAE) barrier resin obtained by direct injection molding are reported. The slight shift of the glass transition temperatures (Tg) of the pure components when blended is attributed to partial miscibility rather than interchange reactions. Both the small strain and the break properties of the blends were close or even above those predicted by the direct rule of mixtures. The specific volume of the blends appeared to be the main reason for the modulus behavior. The linear values of the elongation at break indicated that the blends were compatible, and were attributed to a combination of good adhesion between the two phases of the blends and the small size of the dispersed phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 132–139, 2004

Effect of composition and comonomer type on the rheology, morphology and properties of ethylene-α-olefin copolymer/polypropylene blends

The rheology, morphology, thermal and mechanical properties of blends containing low molecular weight polypropylene (PP) and metallocene-based ethylene-α-olefin copolymers (ECs) have been investigated. Evaluation of the thermo-rheological properties of the blends showed that they are immiscible, both in the solid and melt state, over the whole range of compositions. Rheological properties were correlated to blend morphology, by using the Palierne emulsion model. The resulting low values of interfacial tension confirmed excellent compatibility between the phases. Addition of ECs in PP resulted in significant ductility improvement. The transition from plastic to elastomeric properties coincided with phase inversion. The butene-based EC was found to be the most beneficial in terms of impact properties. Fine morphologies, with sub-micron sizes of the dispersed phase, were obtained upon post-extrusion shearing of the blends.

Properties of Starch Blends with Biodegradable Polymers

Starch, one of the most inexpensive and most readily available of all natural polymers, can be processed into thermoplastic materials only in the presence of plasticizers and under the action of heat and shear. Poor water resistance and low strength are limiting factors for the use of materials manufactured only from starch, and hence the modification of starch is often achieved by blending aliphatic polyesters. In this review, the literatures concerning the properties of various blends of starch and aliphatic polyesters have been summarized. The biodegradable rates of blends can be controlled to a certain extent depending on the constitutions of blends, and the mechanical properties of blends are close to those of traditional plastics such as polyethylene and polystyrene. The reduction of their sensitivity to humidity makes these materials suitable for the production of biodegradable films, injection-molded items, and foams.

Structure and mechanical properties of blends of two thermotropic copolyesters

AbstractBlends of two thermotropic copolyesters, poly(ethylene terephthalate/p‐hydroxy benzoic acid) (20/80), EB, and poly(p‐hydroxy benzoic acid/2,6‐hydroxy naphthoic acid) (73/27), BN, were obtained in the melt state by direct mixing in an injection machine throughout the full composition range. They comprised an almost pure EB phase and a BN‐rich phase that contained some reacted EB. Important synergisms with most of the values above those of the two pure blend components were found at most compositions in the modulus of elasticity and the tensile strength. The synergisms appeared to be due to the concomitant effect mainly of an orientation of the components higher in the blends than in the pure components, and to a lesser extent, of a blending‐induced specific volume decrease.

Studies on morphology and mechanical properties of EPDM‐g‐VOS/LLDPE blends for engineering applications

AbstractA new type of vinyloxyaminosilane (VOS) grafted ethylene‐propylene‐diene terpolymer (EPDM‐g‐VOS) has been synthesized in a Haake Rheocord‐90, torque rheometer. Using EPDM‐g‐VOS the blends of linear low density polyethylene (EPDM‐g‐VOS/LLDPE) with varying percentage compositions were prepared in a two‐roll mixing mill. The morphology of the EPDM‐g‐VOS/LLDPE blends was studied using a scanning electron microscope. The morphology of the blends indicated a two‐phase structure in which the minor phase is dispersed as domains in the major continuous phase. However, at 50 wt% both EPDM‐g‐VOS and LLDPE exist as continuous phases and generate co‐continuous morphology. The effect of blend ratio and dicumyl peroxide (DCP) concentration on the mechanical properties such as tensile strength, elongation at break, Young's modulus, and hardness have been investigated. It was ascertained that the mechanical properties of blends increase with increase of LLDPE content and DCP concentration. An attempt has been made in this investigation to correlate the variation of mechanical properties with morphology of the blend. Data from reprocessability studies of the blends indicate that these blends can be recycled and reprocessed several times without appreciable loss of their mechanical characteristics. Data on mechanical characteristics indicate that these blends can be used for engineering applications with better performance than ungrafted EPDM. The EPDM‐g‐VOS/LLDPE blends developed in the present work may find applications in the field of automobiles and medium high voltage cable insulation. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 201–213, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10019

Correlation of rheological and mechanical properties for blends of recycled HDPE and virgin polyolefins

Correlation of rheological and mechanical properties for blends of recycled HDPE and virgin polyolefins

Rheological and Mechanical Characterization of Biodegradable Aliphatic Polyester and Poly(epichlorohydrin) Blends

Rheological, thermal, and mechanical properties for blends of synthetic biodegradable aliphatic polyester (BDP) and poly(epichlorohydrin) (PECH) were examined. The synthetic BDP was a copolymer synthesized from the polycondensation reaction of aliphatic glycols and aliphatic dicarboxylic acids. From differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis, we confirmed the BDP and PECH blends were miscible. The DSC results suggest that the degree of crystallization of BDP in blends decreased sharply as PECH content increased. We also show a great increase of both elongation at the break point and tensile impact strength increase with PECH content. From the static and dynamic rheological experiments, we found that shear viscosity increases with PECH content, which is consistent with the storage moduli increasing with PECH content. This suggests that PECH acts as a diluent for BDP, and these two polymers are compatible in the melt state. The storage moduli of the BDP homopolymer are lower than that of blends.

Improvement of Mechanical Properties of Poly(butylene terephthalate)/Polyarylate Blends with Various Compositions via Zone Drawing-Zone Annealing

Poly(butylene terephthalate)/polyarylate (PBT/PAr) blends of various compositions were subjected to a series of thermal and mechanical treatments. The evolution of the structure together with the static mechanical properties of produced fibers were investigated. It was found that zone drawing-zone annealing at 140 and 190[ddot] C markedly improves the blend mechanical properties: the Young modulus increases up to 5 times, the tensile strength-up to 10 times (compared to neat PBT) and up to 5 times (compared to neat PAr), the elongation at break drops 50–100 times with the rise of PAr content. The highest values of modulus and strength are obtained for blends containing between 10 and 35% (by wt) PAr. The observed improvement is explained by the substantial chain axis orientation and enhanced crystallization. of PBT offered by the zone drawing-zone annealing process, as proven by wide angle X-ray diffraction and birefrigent tests. Finally, a conclusion is drawn that after the appropriate treatments the PBT/PAr blends represent microfibrillar reinforced composites, similarly to other polymer blends for which the same improvements in the mechanical properties are known to be due to the microfibrillar reinforcing effect. The PBT microfibrils are visualized by observations using scanning electron microscope.

Phase morphology, crystallinity and mechanical properties of binary blends of high barrier ethylene–vinyl alcohol copolymer and amorphous polyamide and a polyamide-containing ionomer

A number of dry melt-mixed binary blends of 32mol% ethylene vinyl–alcohol copolymer (EVOH) and an amorphous polyamide (PA) and a crystalline Nylon-containing ionomer have been characterized in terms of phase morphology, crystallinity and mechanical properties by DSC, WAXS, DMA, SEM, microhardness (MH) and tensile testing. Such blends are claimed by manufacturers to improve the thermoformability characteristics of EVOH while retaining/improving its high gas barrier under high relative humidity conditions. From the results, it becomes apparent that the miscibility of this high barrier EVOH grade with the amorphous PA is very poor, and clear phase segregation throughout composition was shown by DSC, DMA and SEM. Factors like geometric hindrance and chain stiffness of the amorphous PA could be responsible for this behavior. A lack of good interaction between EVOH/PA blend components was further supported by the negative deviation from the simple additive rule seen in the mechanical properties of these blends. A two phase structure was also observed in the EVOH/ionomer blends, but from the results a better phase compatibility was inferred. This compatibility increased in the ionomer rich blends and was thought to be enhanced by the presence of crystalline Nylon in the formulation of the ionomer. An increased in flexibility and toughness was measured in the mechanical properties of these EVOH/ionomer blends. The flexibility rose with increasing strain rate in extruded films. The overall crystallinity of the blends was lower than that of neat EVOH, ought to the amorphous condition of the PA and the lower crystallinity exhibited by the ionomer.

Dynamic Mechanical Studies of the Sulfonated Butyl Rubber Ionomers and Their Blends

Dynamic mechanical properties of sulfonated butyl rubber ionomers neutralized with different amine or metallic ion (zinc or barium) and their blends with polypropylene (PP), high-density polyethylene (HDPE), or styrene-butadiene-styrene (SBS) triblock copolymer were studied using viscoelastometry. The results showed that glass transition temperatures of ion pair–containing matrix and ionic domains (T g1 and T g2, respectively) of amine-neutralized ionomers were lower than those of ionomers neutralized with metallic ions, and the temperature range of the rubbery plateau on the storage modulus plot for amine-neutralized ionomers was narrower. The modulus of the rubbery plateau for amine-neutralized ionomers was lower than that of ionomers neutralized with zinc or barium ion. With increasing size of the amine, the temperature range for the rubbery plateau decreased, and the height of the loss peak at higher temperature increased. Dynamic mechanical properties of blends of the zinc ionomer with PP or HDPE showed that, with decreasing ionomer content, the T m of PP or HDPE increased and T g1 decreased, whereas T g2 or the upper loss peak temperature changed only slightly. The T g1 for the blend with SBS also decreased with decreasing ionomer content. The decrease of T g1 is attributed to the enhanced compatibilization of the matrix of the ionomer-containing ion pairs with amorphous regions of PP or HDPE or the continuous phase of SBS due to the formation of thermoplastic interpenetrating polymer networks by ionic domains and crystalline or glassy domains.

Morphology and mechanical properties of blends of polycarbonate and segmented copolyetherester

The solid state features and the mechanical properties of melt mixed polycarbonate (PC)/segmented copolyetherester (CPEE) blends were investigated over the full composition range. The partially crystallized blends were composed of two amorphous phases but with only small composition differences in most blend compositions. The specific interactions, and the free volume decreases observed, gave rise to a decrease in the γ relaxation strength. The dependence on composition of both the decreases in the γ relaxation strength and in the free volume, as well as that of the modulus of elasticity and yield stress, were very similar to those of miscible blends. The nature of the amorphous phases of the blends at room temperature, changed from glassy to partially rubbery as the CPEE content was increased. As a consequence, to discuss the plots of the properties against composition at room temperature, the properties of the rubbery materials in the glassy state had to be determined. The synergistic modulus and yield stress behaviors appeared to be mainly determined by the γ relaxation strength and specific volume decrease, and that of ductility additionally by the Tg change.

Radiation Vulcanization of MDPE/EPDM Blends Loaded with White and Black Fillers

Blends of 60/40 phr of MDPE/EPDM have been subjected to radiation vulcanization by gamma rays of 60Co in the presence of either HAF carbon black or white Hisil. The effect of the level of loading with Hisil has been followed up in the range of 0-100 phr. Mechanical properties, namely, elongation at break, tensile modulus and tensile strength were followed up as a function of irradiation dose for different loading of the blend with Hisil. The most appropriate degree of loading has been found to be 50-75 phr of Hisil. Comparison of mechanical properties of blends loaded with 50 phr of either HAF black or Hisil has been carried out. The data obtained indicated that Hisil is more effective as reinforcing filler than HAF black for radiation vulcanized MDPE/EPDM blends. The improvement attained in mechanical properties may be attributed to the reinforcing effect of filler as well as the induced cross-linking by radiation.

Structure and properties of injection molded blends of poly(ether imide) and a thermotropic copolyester

The phase structure and mechanical properties of blends composed of poly(ether imide) and a thermotropic liquid-crystalline copolyester, Rodrun LC-5000, processed by injection molding were studied in the PEI-rich region. The addition of Rodrun to PEI produces fully immiscible blends and strongly improves the processability of PEI. Injection molding gave rise in very poor LCP blends to fine dispersed phases; in the rest of compositions it gave rise to coarse structures. This was probably due to the very large viscosity difference between the components of the blends. An increase in the melt temperature led to a smaller viscosity difference and as a consequence dispersed phase dispersion improved. The Young's modulus clearly increased with the Rodrun content. The tensile strength was maintained up to a LCP content of 5% but decreased at higher contents because of the coarse morphologies obtained. The overall mechanical behavior was a main consequence of the lack of fibrillation and of the LCP dispersion level in the matrix.

Blends of bisphenol A polycarbonate and rubber-toughened styrene-maleic anhydride copolymers

The morphology and mechanical properties of polycarbonate (PC) blends with rubber-toughened styrene–maleic anhydride copolymer materials (TSMA) were investigated and compared with the properties of blends of PC with acrylonitrile–butadiene–styrene (ABS) materials. The PC/TSMA blends showed similar composition dependence of properties as the comparable PC/ABS blends. Polycarbonate blends with TSMA exhibited higher notched Izod impact toughness than pure PC under sharp-notched conditions but the improvements are somewhat less than observed for similar blends with ABS. Since PC is known for its impact toughness except under sharp-notched conditions, this represents a significant advantage of the rubber-modified blends. PC blends with styrene–maleic anhydride copolymer (SMA) were compared to those with a styrene–acrylonitrile copolymer (SAN). The trends in blend morphology and mechanical properties were found to be qualitatively similar for the two types of copolymers. PC/SMA blends are nearly transparent or slightly pearlescent. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1508–1515, 1999

Rheological, thermal, and mechanical properties of poly(ethylene naphthalate)/poly(ethylene terephthalate) blends

Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and 1H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content.

Phase behavior and mechanical properties of blends of cellulose propionate and an alternating propene-carbon monoxide copolymer

Cellulose propionate (CP) and plasticized cellulose propionate (CP16) were blended, both in solution and by extrusion, with high molecular weight alternating propene-carbon monoxide copolymers (P-CO). Tensile testing was performed on injection molded blends with a P-CO content of up to 50 wt.-%. The phase behavior was investigated by means of differential scanning calorimetry and electron microscopy. The blends are miscible at compositions up to about 10 wt.-% P-CO. P-CO lowers the melt viscosity of both CP and CP16 and acts as a polymeric plasticizer. Higher amounts of P-CO result in phase separation with domains of P-CO-rich material in the dispersed phase and a continuous CP/CP16-rich phase with a T g even higher than that of pure CP. In this state toughness decreases slightly with increasing P-CO content, while modulus and yield stress increase. After transition into the bicontinuous phase, occurring at a P-CO-content of around 25 wt.-%, toughness and elongation at break increase significantly, while modulus and yield stress decrease.

Effect of the components' molar mass and of the mixing conditions on the compatibilization of PE-LCP blends by PE-g-LCP copolymers

The rheology, morphology, and mechanical properties of blends of high-density polyethylene (HDPE) with a semiflexible liquid crystalline copolyester (SBH) were studied in order to assess the compatibilizing ability of added PE-g-SBH copolymers, and its dependence on the molar mass of the PE matrix, and on the technique used for blend preparation. The PE-g-SBH copolymers were synthesized as described in previous articles, either by the polycondensation of the SBH monomers in the presence of a functionalized PE sample containing free carboxyl groups, or by reactive blending of the latter polymer with preformed SBH. Two samples of HDPE having different molar masses, and two samples of SBH with different melt viscosity and different microstructure, were used for preparing the blends. The two components and the compatibilizer were either blended in a single batch or used to prepare binary master blends to which the third component was added at a later stage. The results indicate that the PE-g-SBH copolymers do, in fact, compatibilize the PE–SBH blends and that the effect is more pronounced with the lower molar mass PE matrix and with the SBH sample having lower viscosity. The experiments carried out on blends prepared with different techniques show that the compatibilizing ability of the graft copolymer is improved if the latter is first blended with either of the two main components. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 603–613, 1999