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1.
《塑料、橡胶和复合材料》2013,42(6):218-225
AbstractLow density polyethylene (LDPE)/ultrahigh molecular weight polyethylene (UHMWPE) and LDPE/poly(ethylene-co-vinylacetate) (EVA) blends were tested and compared with respect to their environmental stress cracking resistance (ESCR) using the Bell telephone test. The time to failure in the ESCR test improved with increasing UHMWPE and EVA content, and considerable improvements were produced when an UHMWPE weight fraction of 0.4 and EVA weight fraction of 0.03 were used. Thermal and morphological studies were conducted, and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterised by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples. 相似文献
2.
Rheology, Morphology and Estimation of Interfacial Tension of LDPE/EVA and HDPE/EVA Blends 总被引:1,自引:0,他引:1
H.A. Khonakdar S.H. Jafari A. Yavari A. Asadinezhad U. Wagenknecht 《Polymer Bulletin》2005,54(1-2):75-84
Summary Rheological characteristics and morphology of low-density polyethylene (LDPE) /ethylene vinyl acetate copolymer (EVA) and high-density polyethylene (HDPE)/EVA blends were compared. Morphological examinations clearly reveal a two-phase morphology in which the LDPE/EVA blends have smaller dispersed domain size than HDPE/EVA Furthermore, LDPE/EVA shows a finely interconnected morphology at 50wt% of EVA while HDPE/EVA exhibits a coarse co-continuous morphology at the same composition. The morphological observations can be attributed to the lower viscosity ratio and lower interfacial tension in the LDPE/EVA system. The Palierne model also successfully fits to the experimental data giving higher values for interfacial tension of HDPE/EVA system as compared to LDPE/EVA. 相似文献
3.
H. A. Khonakdar S. H. Jafari A. Haghighi‐Asl U. Wagenknecht L. Häussler U. Reuter 《应用聚合物科学杂志》2007,103(5):3261-3270
Uncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 2007 相似文献
4.
Radiation effects of low‐density polyethylene/ethylene‐vinyl acetate copolymer (LDPE/EVA) blends were discussed. EVA content in the LDPE/EVA blends was an enhancement effect on radiation crosslinking of LDPE/EVA blends, and the highest radiation crosslinking was obtained when the EVA content was reached at 30% when irradiated by γ‐ray in air. The phenomenon was discussed with the compatibility, morphology, and thermal properties of LDPE/EVA blends and found that the enhanced radiation crosslinking of the LDPE/EVA blends was proportional to the good compatibility, the increasing degree of the amorphous region's content of the LDPE/EVA blends, and the vinyl acetate content of EVA. We also found that the vinyl acetate of EVA in the blends is easily oxidized by γ‐ray irradiation in air. The possible radiation crosslinking and degradation mechanism of LDPE/EVA blends was discussed quantitatively with a novel method “step‐analysis” process of irradiated LDPE/EVA blends in the thermal gravimetric analysis (TGA) technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1296–1302, 2002 相似文献
5.
In this article, we discuss the radiation effects of high‐density polyethylene (HDPE)/ethylene–vinyl acetate (EVA) copolymer blends. In comparison with the low‐density polyethylene/EVA blends, the EVA content in the HDPE/EVA blends had a lower enhancement effect on radiation crosslinking by γ‐ray irradiation in air. The phenomenon is discussed with the compatibility, morphology, and thermal properties of HDPE/EVA blends. The HDPE/EVA blends were partly compatible in the amorphous region, and radiation crosslinking of the HDPE/EVA blend was less significant, although increasing the amorphous region's content of the HDPE/EVA blends and the vinyl acetate content of EVA were beneficial to radiation crosslinking. The good compatibility was a prerequisite for the enhancement effect of EVA on the radiation crosslinking of the polyethylene/EVA copolymer. The radiation crosslinking and the degradation mechanism of HDPE/EVA blends were examined quantitatively by a novel method, the step analysis process of irradiated HDPE/EVA blends with a thermal gravimetric analysis technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 553–558, 2002 相似文献
6.
7.
Z. I. Ali 《应用聚合物科学杂志》2007,104(5):2886-2895
The radiation‐induced crosslinking, compatibility, and surface modification of low density polyethylene/ethylene vinyl acetate blends (LDPE/EVA) were investigated. The structural and physical properties were characterized in terms of gel content, hot set, mechanical properties, contact angle, and surface free energy. The highest crosslink density was obtained at 20 wt % of EVA. Gel content of LDPE/EVA blends was increased with increasing irradiation dose, vinyl acetate (VA), and EVA contents. The hot set results are consistent with the gel content data. Mechanical testing showed that the tensile strength of samples increased with increasing irradiation dose up to 180 kGy, whereas the elongation at break was decreased with increasing irradiation dose. Contact angle measurements showed that the surface hydrophillicity of LDPE blend was increased with increasing irradiation dose and contents of both VA and EVA. The surface free energy was greatly dependent on irradiation dose and content of both VA and EVA. The total surface free energies of different LDPE formulations were in the range 17.25–32.51 mN/m, in which the polar (pσ) and disperse (dσs) values were within the range 16.52–26.6 and 0.9–5.91 mN/m, respectively. In conclusion, electron beam irradiation and blending LDPE with EVA improved the wettability or adhesion properties of LDPE/EVA blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
8.
Blends of low‐density polyethylene with random copolymers of ethylene and vinyl acetate (PE/EVA) are studied with respect to their environmental stress‐cracking resistance (ESCR) using the Bell‐telephone test. This system shows the shortest time to failure in the ESCR test after annealing at 50 °C in a stress‐cracking agent (Igepal solution) compared with that in the tests conducted at 30 and 70 °C. The increase of the time to failure at 70 °C as compared with that at 50 °C is probably the result of the semicrystalline proportion of EVA melting. Transmission electron microscopy images (see Figure) reveal that EVA particles are molten and deformed in bending direction of the sample at 70 °C in contrast to samples annealed at 50 and 30 °C. TEM pictures of a failed sample during the test conducted at 50 °C indicate that EVA particles can stop crack propagation.
9.
High density polyethylene (HDPE), calcium carbonate (CaCO3), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder.
The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect
of EVA loading on the melting temperature (T
m) and the crystallization temperature (T
C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO3 was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading
of CaCO3, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO3 blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and
interfacial interaction between CaCO3 with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of
the CaCO3 by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO3/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques. 相似文献
10.
11.
B.N. Ravi Kumar B. Suresha R.R.N. Sailaja M. Venkataramareddy 《Polymer Composites》2010,31(3):426-433
The article presents the results of experimental investigation on three‐body abrasive wear behavior of nanoclay‐filled EVA/LDPE (NC‐EVA/LDPE) composites. NC‐EVA/LDPE composites with and without compatibilizer were prepared by Brabender Co‐Twin extruder (Make: CMEI, Model: 16CME, SPL) and poly(ethylene‐co‐glycidyl methacrylate) was used as the compatibilizer. The mechanical properties were evaluated using Universal testing machine. In three‐body wear tests, silica sand particles of size 200–250 μm were used as dry and loose abrasives. Three‐body abrasive wear studies were carried out using dry sand/rubber wheel abrasion test rig. The effect of abrading distance on the abrasive wear behavior of neat EVA, EVA/LDPE, and NC‐EVA/LDPE composites was reported. The results showed that the wear volume loss is increased with increase in abrading distance and the specific wear rate decreased with increase in abrading distance. However, the presence of nanoclay filler in EVA/LDPE composite showed a promising trend. Abrasive wear volume of the composites was correlated with mechanical properties such as hardness, tensile strength, and percentage elongation. However, higher weight percentage of LDPE in EVA increased the wear rate. The results indicate that NC‐EVA/LDPE with compatibilizer composite exhibits good abrasive wear resistance compared with NC‐EVA/LDPE without compatibilizer. Attempts to explain these differing trends are made in this work by analyzing the features observed on the worn surface samples by employing scanning electron microscopy (SEM). POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers 相似文献
12.
Electron beam processing of LDPE/EVA/PCR ternary blends: radiation sensitivity evaluation and physico-mechanical characterization 总被引:1,自引:1,他引:0
Kumar A. Dubey Yatender K. Bhardwaj Chandrashekhar V. Chaudhari Kuppa S. S. Sarma Narender K. Goel Sunil Sabharwal 《Journal of Polymer Research》2011,18(1):95-103
LDPE/EVA/PCR blends having fixed percentage of PCR were prepared by melt mixing and irradiated to different radiation doses
using electron beam. Gel fraction and crosslinking density of the blends were found to increase with increase in EVA content
in the formulation, suggesting higher radiation sensitivity of EVA. The heat of mixing and polymer-polymer interaction parameter
indicated better miscibility between EVA/PCR than between LDPE/PCR and LDPE/EVA. Dynamic mechanical properties of the blends
were found to significantly vary with the variation in the EVA fraction in the blends. In the composition range studied the
storage modulus decreased from 3.8 × 108 to ∼1 × 108 Pa at strain amplitude of 5 × 10−6 m. The experimentally obtained data deviated significantly from both the series as well as parallel model. The bulk density
showed a positive deviation from additive rule. The X-ray diffraction pattern of the blends revealed reduction in the crystallinity
of LDPE on blend formation. DSC thermograms of blends did not indicate any significant shift in the melting peaks, indicating
immiscibility of LDPE and EVA domains in the presence of PCR. 相似文献
13.
Xiaohu Zhang Hongmei Yang Yihu Song Qiang Zheng 《Polymer Engineering and Science》2014,54(12):2848-2858
High density polyethylene (HDPE)/ethylene‐vinyl acetate copolymer (EVA) blends with selective crosslinking the EVA phase were prepared and the crystallization, rheological, and mechanical behaviors were studied. Selective crosslinking of EVA component could greatly improve both tensile and impact strengths of the HDPE‐rich blends and influence melting enthalpy at different annealing temperature in successive self‐nucleation and annealing procedure. Dynamic mechanical analysis reveals that glass transition temperatures of both the HDPE and EVA components are lowered upon blending and are raised upon crosslinking. The uncrosslinked HDPE/EVA blends are unstable in the melt and show increment in storage modulus (G′) and decay in loss tangent (tanδ) with annealing time associated with phase coarsening. However, morphology of selectively crosslinked blends in the melt state is highly unstable, characterized by a fast migration of uncrosslinked HDPE component out of the crosslinked EVA phase to the surface resulting in a rapid decay in G′ and an increment in tanδ at the early stage of annealing. POLYM. ENG. SCI., 54:2848–2858, 2014. © 2014 Society of Plastics Engineers 相似文献
14.
In this paper, the tensile deformation and fracture toughness of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends, obtained by dynamic packing injection moulding, have been comprehensively investigated in different directions of rectangle samples, including longitudinal, latitudinal and oblique directions relative to the flow direction. Two kinds of EVA were used with VA content 16 wt% (16EVA) and 33 wt% (33EVA) to control the interfacial interactions. The results indicate that molecular orientation and interfacial interaction play very important roles to determine the tensile behaviour and fracture toughness. Biaxial‐reinforcement of tensile strength was seen for HDPE/16EVA blends but only uniaxial‐reinforcement was observed for HDPE/33EVA blends. The difference is caused by the different interfacial interactions as highlighted by the peel test, scanning electron microscopy (SEM) observation as well as theoretical evaluation. Very high impact strength, decreasing with increasing EVA content, was observed when the fracture propagation is perpendicular to the shear flow direction, while a low impact strength, increasing slightly increasing with EVA content, was seen when the fracture propagation is parallel to the shear flow. The fracture of oblique samples is always along the flow direction instead of along the impact direction or tensile direction. The tensile behaviour and fracture toughness are discussed on the basis of the formation of transcrystalline zones, orientation of EVA particles and matrix toughness of HDPE in different directions. Copyright © 2004 Society of Chemical Industry 相似文献
15.
Attempts were made to trace the effect of organoclay (OC) on the rheological and mechanical behaviors of the low density polyethylene (LDPE)/ethylene‐vinyl acetate (EVA) blends. To do this effectively, in addition to LDPE/EVA/OC system, pure LDPE and LDPE/EVA blends were also examined as model systems. The rheological behavior was determined by the capillary rheometer. Morphological characterization was also carried out using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and theoretical approach based on interfacial energies. Shear viscosity, tensile strength and elastic modulus of LDPE/EVA were found to decrease by increasing the EVA content, while for LDPE/EVA/OC ternary nanocomposites, such properties showed an increase by increasing the content of EVA. Such behavior was explained by the morphological characteristic of the system in which OC was mainly intercalated/exfoliated in the EVA phase. This morphological characteristic was corroborated by the XRD, TEM and interfacial energies data. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers 相似文献
16.
研究了PA6/HDPE、PA6/HDPE/EVA共混物的密度、热性能和力学性能。PA6/HDPE/EVA三元共混物的力学性能比PA6/HDPE二元共混物有明显提高。对于拉伸强度,EVA的最佳含量在2~4份。冲击强度随EVA含量的增加而提高,EVA的含量小于5份时,对共混物的硬度几乎没有影响。 相似文献
17.
A method concerning with the simultaneous reinforcing and toughening of polypropylene (PP) was reported. Dynamical cure of the epoxy resin with 2‐ethylene‐4‐methane‐imidazole (EMI‐2,4) was successfully applied in the PP/maleic anhydride‐grafted ethylene‐vinyl acetate copolymer (MAH‐g‐EVA), and the obtained blends named as dynamically cured PP/MAH‐g‐EVA/epoxy blends. The stiffness and toughness of the blends are in a good balance, and the smaller size of epoxy particle in the PP/MAH‐g‐EVA/epoxy blends shows that MAH‐g‐EVA was also used as a compatibilizer. The structure of the dynamically cured PP/MAH‐g‐EVA/epoxy blends is the embedding of the epoxy particles by the MAH‐g‐EVA. The cured epoxy particles as organic filler increases the stiffness of the PP/MAH‐g‐EVA blends, and the improvement in the toughness is attributed to the embedded structure. The tensile strength and flexural modulus of the blends increase with increasing the epoxy resin content, and the impact strength reaches a maximum of 258 J/m at the epoxy resin content of 10 wt %. DSC analysis shows that the epoxy particles in the dynamically cured PP/MAH‐g‐EVA/epoxy blends could have contained embedded MAH‐g‐EVA, decreasing the nucleating effect of the epoxy resin. Thermogravimetric results show the addition of epoxy resin could improve the thermal stability of PP, the dynamically cured PP/MAH‐g‐EVA/epoxy stability compared with the pure PP. Wide‐angle x‐ray diffraction analysis shows that the dynamical cure and compatibilization do not disturb the crystalline structure of PP in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
18.
Eduardo Ramírez‐Vargas Saúl Sánchez‐Valdes Octavio Parra‐Tabla Sergio Castañeda‐Gutiérrez Juan Méndez‐Nonell Luis Francisco Ramos‐deValle Adriana López‐León Roberto Lujan‐Acosta 《应用聚合物科学杂志》2012,123(2):1125-1136
The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d001 signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
19.
Biju John K.T. Varughese Zachariah Oommen Sabu Thomas 《Polymer Engineering and Science》2010,50(4):665-676
The melt rheological behavior of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends has been examined with reference to the effect of blend ratio, shear stress, and temperature. The HDPE/EVA blends exhibit pseudoplastic behavior, and the observed rheological behavior of the blends was correlated with the extrudate morphology. The experimental values of the viscosity were compared with the theoretical models. The effect of maleic‐ and phenolic‐modified PE compatibilizers on the viscosity of H70 blend was analyzed and found that compatibilization did not significantly increase the viscosity. The effect of dynamic vulcanization and temperature on the viscosity was also analyzed. The activation energy of the system decreased with increase in EVA content in the system. The phase continuity and phase inversion points of the blends were theoretically predicted and compared with the experimental values. The melt flow index (MFI) values of the blends were also determined and found that the MFI values decreased with increase in EVA content in the system. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers 相似文献
20.
《塑料、橡胶和复合材料》2013,42(8):357-363
AbstractThe effect of molecular structure of polyethylene (PE) [low density PE (LDPE), linear LDPE and high density PE] and silane/peroxide concentration on the grafting level and gel content in silane crosslinking process has been studied. The effect of incorporation of ethylene vinyl acetate (EVA) copolymer on the rate of crosslinking and thermal properties of PEs has been reported. The order of gel content was LDPE>linear LDPE>high density PE. With the incorporation of EVA, the rate of crosslinking increased. The degree of crystallinity did not change with crosslinking significantly. However, the shape of melting and crystallisation peaks changed, and two regions due to gel and sol parts were formed. In EVA/PE blends, two melting points were observed for both crosslinked and uncrosslinked samples. The SEM images showed the droplet matrix morphology with the EVA as the dispersed phase, especially for EVA/LDPE blend. The EVA/PE blends failed in hot set test, while the origin of PEs passed the hot set test successfully. 相似文献