Coupling of Nanocavitation With Cyclic Deformation Behavior of High-Density Polyethylene Below the Yield Point

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Kamel Hizoum ◽  
Yves Rémond ◽  
Stanislav Patlazhan
Keyword(s):  
Yield Point ◽  
High Density Polyethylene ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
High Density ◽  
Model Parameters ◽  
Mechanical Modeling ◽  
Lower Stress ◽  
Structure Sensitive ◽  
The Common

The peculiarities of viscoelastic behavior of high-density polyethylene (HDPE) subjected to the uniaxial cyclic tensions and retractions below the yield point are studied. This required using three different deformation programs including (i) the successive increase in strain maximum of each cycle, (ii) the controlled upper and lower stress boundaries, and (iii) the fixed strain at the backtracking points. The experimental data are analyzed in a framework of the modified structure-sensitive model (Oshmyan et al., 2006, “Principles of Structural–Mechanical Modeling of Polymers and Composites,” Polym. Sci. Ser. A, 48, pp. 1004–1013) of semicrystalline polymers. It is supposed that increase in the interlamellar nanovoid volume fraction results in speeding-up the plastic flow rate while decreasing cavitation rate. Consequently, a proper fitting of the stress–strain cyclic diagrams is obtained for the applied deformation programs within the common set of model parameters. This makes it possible to reveal evolution of nanovoid volume fraction in HDPE during cyclic deformations.

Effect of bark flour on viscoelastic behavior of high density polyethylene

2010 ◽  
Vol 45 (9) ◽  
pp. 1007-1016 ◽  
Author(s):  
Kamini Sewda ◽  
S.N. Maiti
Keyword(s):  
Storage Modulus ◽  
High Density Polyethylene ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Peak Shift ◽  
High Density ◽  
Mechanical Restraint ◽  
Higher Temperature ◽  
Tan Δ ◽  
Damping Peak

The dynamic mechanical behavior of high density polyethylene (HDPE) in HDPE/bark flour (BF) composites on varying the volume fraction (Φf) of BF (filler) from 0 to 0.26 has been studied. The storage modulus decreases with increase in BF content up to Φf = 0.07, which is attributed to a pseudolubricating effect by the filler. The storage modulus for the composites at Φ f = 0.20 is higher than HDPE in all other temperature zones due to enhanced mechanical restraint by the dispersed phase. At Φf = 0.07, the loss moduli were either marginally lower or similar to that of HDPE, which is due to the ball-bearing effect of the filler as well as decrease in the crystallinity of HDPE. Above Φf = 0.07, the loss moduli were higher than HDPE. The α-relaxation region of the damping peak shifted toward the higher temperature side with increase in BF content. In the presence of the coupling agent, maleic anhydride-grafted HDPE (HDPE-g-MAH), the storage modulus values were marginally lower than those of the HDPE/BF systems. In the HDPE/BF/HDPE—g—MAH composites, the variations of the loss moduli were similar but values lower than those of the HDPE/BF systems. Damping peak shift in the α-region toward higher temperature was more than those of the HDPE/BF systems, which may be due to the hindrance to the relaxation due to an enhanced phase interaction. The values of tan δ were higher than the rule of mixture for both the composites.

Time-dependent uniaxial piezoresistive behavior of high-density polyethylene/short carbon fiber conductive composites

2004 ◽  
Vol 19 (9) ◽  
pp. 2625-2634 ◽  
Author(s):  
Q. Zheng ◽  
J.F. Zhou ◽  
Y.H. Song
Keyword(s):  
Carbon Fiber ◽  
High Density Polyethylene ◽  
Volume Fraction ◽  
High Density ◽  
Constant Stress ◽  
Time Dependent ◽  
Short Carbon Fiber ◽  
Conductive Composites ◽  
Short Carbon ◽  
Resistance Relaxation

Short carbon fiber (SCF) filled high-density polyethylene conductive composites were studied in terms of time-dependent piezoresistive behaviors. The time-dependent change of resistance under constant stress or strain was found to be the succession of the previous pressure-dependent piezoresistance. Depending on the filler volume fraction and the level of the constant stress or strain, resistance creep and resistance relaxation with different directions were observed. An empirical expression similar to the Burgers equation could be applied to fit the data for both the resistance creep and the resistance relaxation. The fitted relaxation time as a function of pressure showed that there exist two competing processes controlling the piezoresistive behavior and its time dependence. Mechanical creep and stress relaxation of the composites were also studied, and a comparison with the time-dependent resistance implied that there is a conducting percolation network attributed to the physical contacts between SCF and a mechanical network formed by the molecular entanglement or physical crosslinking of the polymer matrix and the interaction between the filler and the matrix. It is believed that the two networks dominate the electrical and the mechanical behaviors, respectively.

Thermal Conductivity of Aluminum Particle Filled High Density Polyethylene Composites – Particle Size Effect

2015 ◽  
Vol 1114 ◽  
pp. 44-49 ◽  
Author(s):  
Tuba Evgin ◽  
Ismail Hakkı Tavman
Keyword(s):  
Thermal Conductivity ◽  
High Density Polyethylene ◽  
Volume Fraction ◽  
Aluminum Particle ◽  
Particle Size Effect ◽  
High Density ◽  
Particle Sizes ◽  
Melt Mixing ◽  
Transient Plane Source ◽  
Thermal Analyzer

The aim of the experimental study is to determine thermal conductivity of composites as a function of volume fraction and size of aluminum (Al) particles. High density polyethylene (HDPE) were filled with Al particles that have different particle sizes, 80 nm and 40-80 μm. Nanocomposites were prepared by the melt-mixing technique at various volume fractions (up to 33%). Thermal conductivity of polymer composites has been measured by C-Therm thermal analyzer depending on the modified transient plane source technique. Thermal conductivity of HDPE/Al composites increases by increasing volume fraction of Al in HDPE matrix. It is found that size of Al particles hasn’t significant effect on thermal conductivity, thermal conductivity of HDPE/Al (80 nm) is close to thermal conductivity of HDPE/Al (40-80 μm).

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