scholarly journals Synthesis of Disentangled Ultra-High Molecular Weight Polyethylene: Influence of Reaction Medium on Material Properties

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Giuseppe Forte ◽  
Sara Ronca
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Catalyst Activity ◽  
Reaction Medium ◽  
High Strength ◽  
Catalytic Performance ◽  
Lower Amount ◽  
Processing Route ◽  
Molecular Characteristics ◽  
Ultra High Molecular Weight

The polymerization of ethylene to Ultra-High Molecular Weight Polyethylene (UHMWPE) in certain reaction conditions allows synthesis of nascent powders with a considerably lower amount of entanglements: the material obtained is of great interest from both academic and industrial viewpoints. From an academic point of view, it is interesting to follow the evolution of the metastable melt state with the progressive entanglements formation. Industrially, it is valuable to have a solvent-free processing route for the production of high modulus, high strength tapes. Since the polymer synthesis is performed in the presence of a solvent, it is interesting to investigate the influence that the reaction medium can have on the catalyst activity, resultant molecular characteristics, and polymer morphology at the macroscopic as wells as microscopic level. In this paper, we present the effect that two typical polymerization solvents, toluene and heptane, and mixtures of them, have on the catalytic performance and on the polymer properties. The observations are that an unexpected increase of catalyst activity, accompanied by a significant improvement in mechanical properties, is found when using a carefully chosen mixture of solvents. A tentative explanation is given on the basis of the presented results.

scholarly journals The nanostructuring of ultra-high-molecular-weight polyethylene in thermal and mechanical fields as revealed by DSC

2021 ◽  
Vol 2103 (1) ◽  
pp. 012095
Author(s):  
L P Myasnikova ◽  
A K Borisov ◽  
Yu M Boiko ◽  
A P Borsenko ◽  
V F Drobot’ko ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Melting Temperature ◽  
Mechanical Characteristics ◽  
Thickness Distribution ◽  
High Strength ◽  
High Modulus ◽  
Know How ◽  
First Time ◽  
Ultra High Molecular Weight

Abstract The ultra-high-molecular-weight polyethylene reactor powders are widely used for the actively developing solvent-free method for producing high-strength high-modulus PE filaments, which includes the compaction and sintering of a powder followed by orientational hardening. To find an appropriate regime of the technological process, it is important to know how the nanostructure changes when transforming from a powder to a precursor for hardening. Nanocrystalline lamellae are characteristics of the powder structure. For the first time, the DSC technique was used to follow changes in the thickness distribution of lamellae in ultra-high-molecular-weight polyethylene reactor powder on its way to a precursor for orientation hardening. It was found that the percentage of thick (>15 nm) and thin (10 nm) lamellae in compacted samples and those sintered at temperatures lower than the melting temperature of PE (140°C) remains nearly the same. However, significant changes in the content of lamellae of different thicknesses were observed in the samples sintered at 145°C with subsequent cooling under different conditions. The influence of the lamellae thickness distribution in precursors on the mechanical characteristics of oriented filaments was discussed.

The radiation effect on thermal conductivity of high strength ultra-high-molecular-weight polyethylene fiber by γ-rays

2006 ◽  
Vol 101 (4) ◽  
pp. 2619-2626 ◽  
Author(s):  
Atsuhiko Yamanaka ◽  
Yoshinobu Izumi ◽  
Tooru Kitagawa ◽  
Takaya Terada ◽  
Hideki Sugihara ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Radiation Effect ◽  
High Strength ◽  
Polyethylene Fiber ◽  
Γ Rays ◽  
Ultra High Molecular Weight

Twist-film gel spinning of large-diameter high-performance ultra-high molecular weight polyethylene monofilaments

2016 ◽  
Vol 87 (19) ◽  
pp. 2323-2336 ◽  
Author(s):  
Xudong Fang ◽  
Jing Shi ◽  
Tom Wyatt ◽  
Donggang Yao
Keyword(s):  
Molecular Weight ◽  
Solvent Extraction ◽  
High Molecular Weight ◽  
High Performance ◽  
Large Diameter ◽  
High Strength ◽  
Gel Spinning ◽  
Solvent Removal ◽  
Spinning Process ◽  
Ultra High Molecular Weight

A twist-film gel spinning process was developed for large-diameter high-performance ultra-high molecular weight polyethylene (UHMWPE) monofilaments. By using polybutene as a spin-solvent, film twisting was demonstrated to be an effective method for solvent removal; approximately 70% of solvent contained in the gel film can be removed simply by film twisting. This mechanical solvent removal process also makes conventional solvent extraction proceed significantly faster. Besides improved solvent extraction efficiency, large-diameter high-strength UHMWPE monofilaments (with diameters of about 80 µm and strength exceeding 3.2 GPa) can be produced with this process, which is difficult to achieve using conventional processes. The capability of making large-diameter high-strength monofilaments may allow new products of UHMWPE to be developed in a number of high-performance applications.

Achievement of strictly linear ultra-high molecular weight polyethylene with narrow dispersity by dint of nitro-enhanced 2,6-bis(imino)pyridylchromium chloride complexes

2019 ◽  
Vol 43 (28) ◽  
pp. 11307-11315 ◽  
Author(s):  
Chuanbing Huang ◽  
Arumugam Vignesh ◽  
Chantsalnyam Bariashir ◽  
Yanping Ma ◽  
Yang Sun ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Catalytic Performance ◽  
Steric Effects ◽  
Chromium Complexes ◽  
Reaction Parameters ◽  
Chloride Complexes ◽  
Ultra High Molecular Weight

The influence of reaction parameters and the electronic/steric effects of chromium complexes on the catalytic performance was investigated in detail.

scholarly journals An investigation of the mechanical and biological properties of nylon coated ultra-high-molecular-weight polyethylene.

2021 ◽  
Author(s):  
Dariush Firouzi
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
High Strength ◽  
Areal Density ◽  
Biological Properties ◽  
Sem Analysis ◽  
Body Armor ◽  
Sem Images ◽  
Biological Compatibility ◽  
Ultra High Molecular Weight

In spite of considerable improvements in the manufacturing of body armor using lightweight and high-strength fibres, demands for lighter and more flexible products capable of providing sufficient protection against various types of threats has not waned. Among high strength fibres, ultra high molecular weight polyethylene (UHMWPE) possesses superior mechanical and physical properties. Nevertheless, the use of UHMWPE fabric with a shear thickening fluid (STF) materials for the manufacture advanced liquid body armors has been unsuccessful as this polymer is inherently inert and cannot bond or readily interact with other materials. To address these challenges, this research thesis focused on the development of a new method to increase the performance of UHMWPE fibre/fabric for high impact applications and improve its capability to bond with silica-based STF materials. A novel coating technique was developed using a nylon solution with UHMWPE fibre which results in a strong interlocking mechanism and the creation of a uniform coating without adding extra thickness to the fibre. Standard penetration tests showed considerable improvement in puncture/stab resistance of a nylon coated UHMWPE fabric compared with the uncoated fabric (with equivalent areal density) in terms of energy absorption, which was also explained by the scanning electron microscope (SEM) images of ruptured areas. In order to further improve the penetration resistance of UHMWPE fabric, a dispersion of fumed silica particles in polyethylene glycol (PEG) was synthesized exclusively via a novel sequential ultrasonication technique to incorporate with a multilayer stack of UHMWPE fabric. A complete set of rheological measurements, zeta potential and SEM analysis were done to study the viscoelastic characteristics and tune the stability of the synthesized STF samples. Evidence of the improved adhesion of STF materials to UHMWPE fibres coated with nylon from the SEM images was observed. Finally, while the evidence of improved mechanical properties of nylon coated UHMWPE were provided (e.g. higher creep resistance and toughness), its potential application for the manufacturing of medical devices was also explored. As a result, from the preliminary cytotoxicity and osteolysis assessments, it was shown that the biological compatibility of UHMWPE was improved when it was coated with nylon.

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