Mechanical and rheological properties of carbon black filled polyethylene

The mechanical and rheological properties of high density polyethylene filled with carbon black have been examined. Two sources of carbon black (one commercial and other obtained from a pyrolysis process) and various treatments have been studied. The rheological measurements in the melt state has been performed on a Rheometrics stress rheometer and a capillary rheometer. These materials possess outstanding hardness and toughness showing great potential for structural application. Comparison of carbon black from two sources showed that the carbon from the pyrolysis process has a good potential as a reinforcing agent. It was found that surface treatment reduces the particle-particle interactions and improves the filler dispersion. The relationship between the yield stresses, filler percentage, surface modification by the coupling agents and mechanical properties is discussed.     

Mechanical and thermal properties of exfoliated graphite nanoplatelets reinforced polyethylene terephthalate/polypropylene composites

Exfoliated graphite nanoplatelets (GNP) reinforced composites materials based on blend of poly(ethylene terephthalate) (PET) and polypropylene (PP) were prepared by melt extrusion followed by injection molding. 10 parts per hundred resin (phr) styrene‐ethylene‐butylene‐styrene‐g‐maleic anhydride was added to the base formulation PET/PP (70/30) as a compatibilizer. PET/PP/GNP composites 0–5 phr were prepared and characterized using field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and Fourier transform infrared (FTIR) spectroscopy analysis. The morphological studies revealed a homogenous dispersion of GNPs in PET/PP blends up to 3 phr loading after which agglomeration occurred. Flexural strength was enhanced by 80% at 3 phr GNPs loading which was the highest value obtained. Interestingly, the highest value for the impact strength was also recorded at 3 phr loading. The thermal stability of the composites were generally improved at all filler loading with the highest at 3 phr. From the overall results, it is clear that the optimum concentration of GNPs in the PET/PP/GNP system in terms of both mechanical and thermal properties was 3 phr loading. Although, the mechanical and thermal properties of the composites were improved, the FTIR analysis did not reveal any chemical interaction between GNP and the polymer matrix. POLYM. COMPOS., 35:2029–2035, 2014. © 2014 Society of Plastics Engineers     

Mechanical and thermal properties of coal gasification fine slag reinforced low density polyethylene composites

Coal gasification fine slag (CGFS) was processed via a grading technique. The CGFS products (CGFS‐S1, CGFS‐S2, CGFS‐S3) with different sizes were obtained. Effects of particle size and unburned carbon on tensile properties of filled low density polyethylene (LDPE) were studied within the CGFS weight fractions ranging from 10 to 50 wt %. The tensile strength was found to increase with decreasing CGFS size, and the tensile properties exhibited good performance, owing to unburned carbon. The tensile strength of the composites increased with increasing CGFS‐S3 weight fraction. The analysis of mathematical model and SEM revealed that the firm improvement of tensile strength resulted from the strong interactions between LDPE polymer chains and CGFS‐S3 particles, and good dispersion of CGFS‐S3 in resin. Thermogravimetric analysis proved obvious reinforcement in thermal‐oxidative stability by incorporation of CGFS‐S3. The degree of crystallinity of LDPE/CGFS‐S3 showed the first increased and then decreased variation tendency. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46203.     

氯磺化聚乙烯流变性能研究

研究氯磺化聚乙烯(CSM)的流变性能，特别是剪切速率、剪切应力和温度对CSM熔体表观粘度的影响。试验结果表明，CSM熔体在试验温度范围内为假塑性流体，随温度的升高其非牛顿性减弱；CSM熔体的表观粘度随表观剪切速率和剪切应力的增大以及温度的升高而降低；剪切应力对CSM的粘流活化能影响不大。     

Anomalous rheological properties of polyethylene molecular composites

The effect of molecular weight on the rheological properties in the molten state has been studied for binary blends of high‐density polyethylene obtained by the Zieglar–Natta catalyst and low‐density polyethylene produced in an autoclave process. The blends composed of high‐density polyethylene with a high molecular weight and low‐density polyethylene show a higher drawdown force than the individual pure components, whereas the blends of high‐density polyethylene with a low molecular weight and low‐density polyethylene do not exhibit anomalous behavior. The pronounced drawdown force for the former blend system is attributed to the viscous enhancement in the linear viscoelastic region as well as the nonlinear strain‐hardening behavior in the elongational viscosity. POLYM. ENG. SCI. 46:1284–1291, 2006. © 2006 Society of Plastics Engineers     

Mechanical and rheological properties of poly(butadiene-acrylonitrile) rubber compounds reinforced with cellulosic material

The usefulness of waste (mainly cellulosic) materials as a reinforcement for acrylonitrile-butadiene rubber (NBR) compounds is shown in this work. The materials tested are: henequen, pine, coconut, sugarcane husks, lignin, and wood sawdust. Their performance is compared with that of commercial reinforcement materials (santocel and solka), using the same copolymer composition without reinforcement as a reference compound. Uniform particle size is achieved by milling and screening. For some of the materials, 6 mm fibers and polymerfiber coupling agent are also tested. Reinforced copolymer formulations are prepared by milling. Optimum curing times are determined with a torsion rheometer. Mechanical and rheological tests (stress-strain behavior, tear resistance, hardness, interfacial strength, storage modulus, and loss tangent), show promising results for some materials, especially when looking for a reinforced product with low dissipation energy.     

Mechanical properties of unidirectional continuous fiber self‐reinforced polyethylene graded laminates

The aim of this study is to prepare of self‐reinforced polyethylene graded composite laminates (SrPEGCL) by adopting both concepts of “graded” and “self‐reinforced” and analyze their mechanical properties under tensile loading. Three different kinds of fiber volume fractions were employed to prepare continuous fiber unidirectional symmetry SrPEGCL with two graded directions. Tensile experiments were carried out to investigate tensile properties of SrPE composites in longitudinal, transverse, and 45‐bias direction. The microscopic failure mechanism of SrPEGCL were studied and observed by Scanning Electron Microscope (SEM). Laminate stress analysis with ply‐by‐ply discount method was adopted to investigate the damage mechanism using failure criteria and parallel spring model. Observations and conclusions about the effect of graded structure and graded direction on mechanical properties of SrPEGCL under tensile loading were discussed. Compared to common self‐reinforced polyethylene composites, SrPEGCL with the same or even less overall fiber volume fraction exhibited 10–20% higher tensile strength under longitudinal, transverse and 45‐bias loading direction, while graded direction had an effect on the mechanical strength of SrPEGCL as well. POLYM. COMPOS., 36:128–137, 2015. © 2014 Society of Plastics Engineers     

Mechanical properties and foaming behavior of cellulose fiber reinforced high‐density polyethylene composites

This article investigates the effects of fiber length and maleated polymers on the mechanical properties and foaming behavior of cellulose fiber reinforced high‐density polyethylene composites. The results from the mechanical tests suggested that long fibers provided higher flexural and impact properties than short fibers. In addition, the maleated high‐density polyethylene increased flexural strength significantly, while the maleated thermoplastic elastormers increased notched Izod impact strength dramatically. On the other hand, the results from the extrusion foaming indicated that the composites with long and short fibers demonstrated similar cell morphology, i.e., a similar average cell size and cell size distribution. However, the addition of maleated high‐density polyethylene caused an increase of the average cell size and cell size distribution in the composites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Dynamic and steady-state rheological properties of linear-low-density polyethylene melt

Linear-low-density polyethylene (LLDPE) is steadily gaining importance in a wide variety of applications due to its excellent performance characteristics in the final product. The rheological properties of LLDPE in the dynamic and steady state are of great pragmatic importance and these have been studied in the present work. A correlation between the dynamic and steady-state rheological properties has been attempted and good agreement has been found.     

Mechanical properties of crosslinked polyethylene

The mechanical properties of crosslinked polyethylene were studied in an extended range of test conditions in order to determine the recommended service conditions for articles made of crosslinked polyethylene. On the other hand, this study can clarify the advantages of crosslinked polyethylene against the unmodified polymer. In fact, the results referred in the literature concerning the changes of mechanical properties of polyethylene introduced by crosslinking are contradictory and cannot clearly distinguish the two types of polymer. The above study concluded that tensile tests at elevated temperatures (above 70°C) with low stresses (about 0.5 MPa) can clearly describe the effect of crosslinking on the mechanical properties of LDPE, i.e., an improvement at least for deformation and service life.     

纤维级高密度聚乙烯流变性能的研究

采用RH2000毛细管流变仪,考察了6种不同相对分子质量(M_w)及其分布指数(MWD)的纤维级高密度聚乙烯(HDPE)的流变性能。结果表明:6种HDPE的非牛顿指数(n)为0.56～0.75,均小于1,其熔体为典型的非牛顿流体,MWD较大的HDPE对剪切速率(■)变化比较敏感,宜采用MWD较小的物料用于纺丝;■为8 032 s~(-1)时,HDPE的黏流活化能较小,基本保持在15 kJ/mol左右,高■下HDPE对温度的敏感程度较小,■对黏度(η_a)的调控占主导地位;随着HDPE的M_w的增大,结构黏度指数(△η)随之增大,其中4种HDPE的△η较小,分别为0.446,0.446,0.446,0.501,预示其可纺性较好,有利于皮芯复合短纤维的成形加工。     

Mechanical and rheological properties of multicomponent polypropylene blends

Polypropylene (PP) compositions containing CaCO₃ filler, EPDM (ethylene-propylene-ethylidenenorbornene) elastomer, and a non-reactive surfactant were investigated in the mixing chamber of a plastograph. Rheological properties were determined from the registered torque (M) vs. time and temperature (T) vs. time curves, while tensile characteristics of the blends were measured on compression molded plates. The homogenization process can be followed with the aid of 1 n M vs. 1/T diagrams. In the first few minutes of the mixing, beside homogenization, a significant breaking down of the elastomer takes place, and the size of the particles attains an equilibrium value. Dispersion time increases with increasing amount of EPDM and surface active-agent. Morphological investigations indicate the presence of a continuous PP phase containing dispersed CaCO₃ and elastomer particles. The rheological and tensile characteristics are seemingly determined by the total amount of additives, which imply that the elastomer and the filler has the same effect on the properties of the composite. Separation of the effects proved, however, that the effect of the two components are dissimilar, the filler exerts a larger influence on the investigated properties.     

Morphology and rheological properties of polypropylene-linear low density polyethylene blends

The dynamic shear viscosity and the morphology of polypropylene homopolymer and copolymer blended with linear low density polyethylene are studied. A maximum in the dynamic shear viscosity vs. blend composition is reported for the polypropylene copolymer, linear low density polyethylene system. The increasing dynamic shear viscosity is in accordance with the occurrence of a morphology of polyethylene inclusions in rubber surrounded by a polypropylene matrix. Comparing calculations of the dynamic shear viscosities—based on a shell model with interlayer—and experimental results supports this view.     

Mechanical,rheological, and crystallinity properties of polylactic acid/polyethylene glycol-polydimethylsiloxane copolymer blends by melt blending

Polylactic acid (PLA) is high in strength and modulus, but its applications are limited partly due to its inherent brittleness. It is difficult to keep the toughness and transparency of modified PLA without damaging its tensile strength and crystallinity. To improve the properties of PLA, polyethylene glycol-polydimethylsiloxane copolymer (PEG-PDMS) was incorporated to PLA via melt blending. By incorporating only 5 wt% of PEG-PDMS into PLA matrix, the elongation at break of the blends increased from 6% to 58% and the tensile strength was found to be 48.8 MPa. Differential scanning calorimetry demonstrated that the crystallinity of PLA/5%PEG-PDMS blends reached 33.5%. At the same time, the energy storage modulus (G) and complex viscosity (η*) of the blends had been improved. UV–vis test showed the light transmittance of the PLA/5%PEG-PDMS blends was slightly decreased. The toughened materials are sufficient to cope with the challenges brought by complex environments, achieving an efficient toughening effect.     

Mechanical and flow properties of high-density polyethylene/low-density polyethylene blends

The recycling of plastic waste is of particular interest in large urban areas where municipal waste represents a large ecological problem. To achieve their objective (consumer products from plastic waste), formulators of a recycling program have to understand the implications of working with mixtures of different resins. Furthermore, in a multiphase system, the thermomechanical history experienced by the resins during processing represents an important link between operating conditions, resin properties, and final product performance. High-density polyethylene/low-density polyethylene (HDPE/LDPE) blends (10, 20, 35, 50, 65, 80, and 90 percent by weight HDPE) were melt blended in an internal mixer. A complete rheological characterization was performed on each blend. The resulting blends were extruded under different processing conditions. The extruded sheets were further characterized to determine their mechanical properties, The experimental results show important differences in the mechanical properties (transverse and longitudinal) of the sheets obtained from the blends. These differences are explained on the basis of the processing conditions (thermomechanical history) and the rheological properties of the molten blends.     

Time-dependent properties of graphene nanoplatelets reinforced high-density polyethylene

The deformation of polymers at constant applied stress is one of their major drawbacks, limiting their use in advanced applications. The study of this property using classical techniques requires extensive testing over long periods of time. It is well known that reinforced polymers show improved behavior over time compared to their neat counterparts. In this study, the effect of adding different amounts of graphene nanoplatelets (GNPs) on the time-dependent properties of high-density polyethylene (HDPE) is investigated using short-term creep tests and load/unload recovery tests. The results are discussed in terms of the test profile and the influence of loading history. Viscoplasticity/viscoelasticity analysis is performed using Zapas model and by comparing creep, creep compliance and pure viscoelasticity curves. The results show that the reinforcement of 15 wt% GNP have the most significant effect on the time-dependent behavior, reducing the strain by more than 50%. The creep compliance curves show that nano-reinforced HDPE behaves nonlinearly viscoelastically even at very low stresses. In addition to demonstrating the effect of nano-reinforcement, the discussion of the results concludes that the influence of loading history can be quite significant and should not be neglected in the design and evaluation of material behavior.     

Mechanical,rheological, and electrical properties of multiwalled carbon nanotube reinforced ASA/Na‐ionomer blend

Varying amounts of multiwalled carbon nanotubes (MWCNTs) was melt‐extruded with the acrylonitrile‐styrene‐acrylate (ASA)/Na‐ionomer blend, and mechanical, rheological, and electrical properties were studied Optical micrographs show good dispersion level at low MWCNT content and network formation at higher nanotubes percentage. DC conductivity model data shows percolation threshold reached at 1% MWCNT content and after percolation, two‐dimensional network structure was formed. The “peak and valley” type surface topology of matrix may be responsible for low percolation threshold limit. The polymer/nanotubes interactions at low MWCNT content increased the mechanical strengths, which were reduced by the network structure and agglomerates of nanotubes at higher nanotubes content. The MWCNTs interacted differently with the architecturally complex polymer chains and controlled chain dynamics accordingly. The Carreau‐Yasuda model was found fit to viscosity data and the model parameters data suggest the zero shear viscosity is function of MWCNTs content but the infinite shear viscosity is independent of nanoparticles content. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42516.     

Mechanical properties and morphology of high-density polyethylene/linear low-density polyethylene blend

The binary blend of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) in the range of composition from 100% HDPE to 100% LLDPE has been investigated for tensile and flexural properties and the morphology in the deformed state on tensile fracture. Tensile properties (initial modulus, yield stress, and elongation-at-yield, ultimate tensile strength and elongation-at-break, and work of yield and work of rupture) and flexural properties (flexural modulus and flexural yield stress) are studied as a function of blend composition. Behavior, in terms of these properties, is distinguishable in three zones of blend composition, viz. (i) HDPE-rich blend, (ii) LLDPE-rich blend, and (iii) the middle zone. In zones (i) and (ii), the variations of these properties are more or less linear, whereas in the middle region [i.e., zone (iii)], there is a reversal of trends in variation or sometimes a behavior opposite to the expected one. The results are explained on the basis of the effects of cocrystallization and the presence of octene-containing segments in the amorphous phase. Scanning electron micrographs of the tensile fracture surfaces are presented to illustrate the occurrence of transverse bands interconnecting the fibrils.     

Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

This is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42869.