scholarly journals Investigation of MWCNT Reinforcement on the Strain Hardening Behavior of Ultrahigh Molecular Weight Polyethylene

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Hassan Mahfuz ◽  
Mujibur R. Khan ◽  
Theodora Leventouri ◽  
Efthymios Liarokapis
Keyword(s):  
Molecular Weight ◽  
Strain Hardening ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Repeated Loading ◽  
Dramatic Improvement ◽  
Scanning Calorimetry ◽  
Multiwalled Carbon ◽  
Hardening Behavior ◽  
Ultrahigh Molecular Weight ◽  
Strain Hardening Behavior

We have investigated strain hardening behavior of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with 2.0 wt% loading of multiwalled carbon nanotubes (MWCNTs). A solution spinning process was used to produce neat and MWCNT-reinforced filaments of UHMWPE. Tensile tests of filaments showed 62% and 114% improvement in strength and modulus, respectively. Strain hardening tests on filaments revealed spectacular contribution by MWCNTs in enhancing strength and modulus by more than one order of magnitude. SEM micrographs showed sufficient coating of nanotube surface with the polymer that promoted interface adhesion. This intimate interfacial interaction enforced alignment of nanotubes during repeated loading-unloading sequences and allowed effective load transfer to nanotubes. Close interaction between UHMWPE and nanotubes was further evidenced by Raman spectral distribution as a positive shift in the D-band suggesting compressive stress on nanotubes by lateral compression of polymer. Nanotubes thus deformed induced the desired strain hardening ability in the UHMWPE filament. Differential scanning calorimetry (DSC) tests indicated around 15% increase in crystallinity after strain hardening—which together with nanotube alignment resulted in such dramatic improvement in properties.

Correlation between Resilient Modulus and Plastic Deformation for Cohesive Subgrade Soil under Repeated Loading

2008 ◽  
Vol 2053 (1) ◽  
pp. 72-79 ◽  
Author(s):  
Shu-Rong Yang ◽  
Wei-Hsing Huang ◽  
Chi-Chou Liao
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Strain Hardening ◽  
Resilient Modulus ◽  
Cohesive Soil ◽  
Repeated Loading ◽  
Hardening Behavior ◽  
Subgrade Soil ◽  
Stress Levels ◽  
Strain Hardening Behavior

Pavement performance is related to resilient modulus and plastic deformation of pavement materials, which in turn are affected by environmental conditions and traffic loading. A series of triaxial tests was conducted on a residual lateritic soil for 10,000 load repetitions, with some specimens subjected to 100,000 load repetitions, to characterize the behavior of cohesive subgrades under repeated loading, including resilient modulus and plastic deformation. The shakedown concept was used to describe the accumulated plastic deformation and the strain-hardening and softening behavior. Experimental results show that the resilient modulus of cohesive subgrades exhibits strain-hardening behavior under low stress levels. In the meantime, the rate of plastic strain accumulation becomes diminutive. Soil under this condition is in a stable state. Conversely, under high stress levels, cohesive soil tends to soften after a specific number of load applications and accumulates excessive plastic strain and leads to an unstable state. To predict the plastic strain of subgrade soil under repetitive loading, regression models incorporating the strain-hardening behavior for a cohesive soil were used.

Preparation and thermal property of ultrahigh molecular weight polyethylene composites filled by calcium carbonate modified with long chain

2018 ◽  
Vol 33 (4) ◽  
pp. 464-476 ◽  
Author(s):  
Zexiong Wu ◽  
Zishou Zhang ◽  
Kancheng Mai
Keyword(s):  
Molecular Weight ◽  
Calcium Carbonate ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Melting Behavior ◽  
Scanning Calorimetry ◽  
Ultrahigh Molecular Weight ◽  
Novel Method ◽  
Uhmwpe Composites ◽  
Crystallization And Melting Behavior ◽  
Excellent Property

Ultrahigh molecular weight polyethylene (UHMWPE) is an excellent property polymer, but its poor processability due to high melt viscosity limits the more wide-ranging application. To improve the processability of UHMWPE composites filled by calcium carbonate (CaCO3), a novel method is reported to modify CaCO3. PE wax coated on the surface of CaCO3 (PEW@CaCO3) can be prepared by acrylic acid–modified CaCO3 (AA-CaCO3) and PE wax. The crystallization and melting behavior of UHMWPE and its composites filled by CaCO3, AA-CaCO3, and PEW@CaCO3 was compared by differential scanning calorimetry. The processability of UHMWPE composites was characterized by torque rheometer. The effect of CaCO3, AA-CaCO3, and PEW@CaCO3 on the crystallization and processability of UHMWPE was discussed.

scholarly journals Wear-Resistant Ultrahigh-Molecular-Weight Polyethylene-Based Nano- and Microcomposites for Implants

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
S. V. Panin ◽  
L. A. Kornienko ◽  
N. Sonjaitham ◽  
M. V. Tchaikina ◽  
V. P. Sergeev ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Wear Resistance ◽  
Surface Treatment ◽  
Bulk Material ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
High Energy ◽  
Hydroxyapatite Nanoparticles ◽  
Scanning Calorimetry ◽  
Tribotechnical Properties ◽  
Ultrahigh Molecular Weight

The influence of modification by hydroxyapatite (HA) nano- and microparticles on tribotechnical properties of ultrahigh-molecular-weight polyethylene (UHMWPE) was investigated to develop polymer implants for endoprosthesis. It was shown that modification of UHMWPE by hydroxyapatite nanoparticles within range of 0.1–0.5 wt.% results in increase of wear resistance at dry sliding by 3 times. On the other hand adding of 20 wt.% of micron size HA gives rise to the same effect. The effect of increasing wear resistance is not substantially changed at surface treatment of the nano- and microcomposites by N+ion beams as compared with nonirradiated blends. Preliminary joint mechanical activation of UHMWPE powder and fillers results in more uniform distribution of nanofillers in the matrix and, as a result, formation of more ordered structure. Structure within bulk material and surface layers was studied by means of optical profilometry, scanning electron microscopy, infrared spectroscopy, and differential scanning calorimetry. It is shown that adding of hydroxyapatite nanoparticles and high-energy surface treatment of the composite by N+ion implantation improve tribotechnical properties of UHMWPE due to formation of chemical bonds in the composite (crosslinking) and ordering of permolecular structure.

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