scholarly journals Increased Elasticity Modulus of Polymeric Materials Is a Source of Surface Alterations in the Human Body

2021 ◽  
Vol 12 (2) ◽  
pp. 24
Author(s):  
Matthias Kapischke ◽  
Igor Erlichman ◽  
Alexandra Pries
Keyword(s):  
Elasticity Modulus ◽  
Polymeric Materials ◽  
Urea Solution ◽  
Sterically Hindered Phenols ◽  
Hernia Surgery ◽  
Nmr Studies ◽  
Alloplastic Materials ◽  
Before And After ◽  
Radical Reduction ◽  
Hindered Phenols

The introduction of alloplastic materials (meshes) in hernia surgery has improved patient outcome by a radical reduction of hernia recurrence rate, but discussion about the biocompatibility of these implanted materials continues since observations of surface alterations of polypropylene and other alloplastic materials were published. This study intends to investigate if additives supplemented to alloplastic mesh materials merge into the solution and become analyzable. Four polypropylene and one polyester alloplastic material were incubated in different media for three weeks: distilled water, saline solution, urea solution, formalin, and hydrogen peroxide. No swelling or other changes were observed. Infrared spectroscopy scanning of incubated alloplastic materials and NMR studies of extracted solutions were performed to investigate loss of plasticizers. The surface of the mesh materials did not show any alterations independent of the incubation medium. FT-IR spectra before and after incubation did not show any differences. NMR spectra showed leaching of different plasticizers (PEG, sterically hindered phenols, thioester), of which there was more for polypropylene less for polyester. This could be the reason for the loss of elasticity of the alloplastic materials with consecutive physically induced surface alterations. A mixture of chemical reactions (oxidative stress with additive leaching from polymer fiber) in connection with physical alterations (increased elasticity modulus by loss of plasticizers) seem to be a source of these PP and PE alterations.

Research changes in the properties of butadiene-nitrile rubber under various aging conditions

2021 ◽  
pp. 009524432110290
Author(s):  
Mariya L Davydova ◽  
Aytalina F Fedorova
Keyword(s):  
Accelerated Aging ◽  
Physical And Mechanical Properties ◽  
Exposure Period ◽  
Climatic Conditions ◽  
Nitrile Rubber ◽  
Sterically Hindered Phenols ◽  
Loading Mode ◽  
Hindered Phenols ◽  
The Republic ◽  
Butadiene Nitrile Rubber

This article represents the results of a study of changes in the properties of vulcanizates based on BNR-18 butadiene-nitrile rubber containing as stabilizers the experimental spatially hindered phenols Stafen, CO3, CO4, and industrial antioxidant 6PPD, after accelerated aging (100°C 96 h) and aging under full-scale exposure in extreme climatic conditions of the Republic of Sakha (Yakutia) during 2 years. In winter, the air temperature reached—48°C, in summer—+36.1°C. It is shown that the experimental sterically hindered phenols more effectively under natural exposure conditions. They are characterized by the most stability in terms of strength throughout the entire exposure period. Under conditions of accelerated aging, the vulcanizate containing the industrial antioxidant 6PPD is characterized by the greatest stability of physical and mechanical properties. According to the viscoelastic characteristics obtained in the dynamic loading mode, the contribution of the presented stabilizers in maintaining resistance to temperature and deformation effects compared with unstabilized rubber is confirmed.

scholarly journals Study of the Ultraviolet Effect and Thermal Analysis on Polypropylene Nonwoven Geotextile

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1080
Author(s):  
Clever Aparecido Valentin ◽  
Marcelo Kobelnik ◽  
Yara Barbosa Franco ◽  
Fernando Luiz Lavoie ◽  
Jefferson Lins da Silva ◽  
...  
Keyword(s):  
Uv Light ◽  
Polymeric Materials ◽  
Tensile Tests ◽  
Thermomechanical Analysis ◽  
Material Stiffness ◽  
Before And After ◽  
Electron Microscopy Analysis ◽  
Physical Tests ◽  
Nonwoven Geotextile

The use of polymeric materials such as geosynthetics in infrastructure works has been increasing over the last decades, as they bring down costs and provide long-term benefits. However, the aging of polymers raises the question of its long-term durability and for this reason researchers have been studying a sort of techniques to search for the required renewal time. This paper examined a commercial polypropylene (PP) nonwoven geotextile before and after 500 h and 1000 h exposure to ultraviolet (UV) light by performing laboratory accelerated ultraviolet-aging tests. The state of the polymeric material after UV exposure was studied through a wide set of tests, including mechanical and physical tests and thermoanalytical tests and scanning electron microscopy analysis. The calorimetric evaluations (DSC) showed distinct behaviors in sample melting points, attributed to the UV radiation effect on the aged samples. Furthermore, after exposure, the samples presented low thermal stability in the thermomechanical analysis (TMA), with a continuing decrease in their thicknesses. The tensile tests showed an increase in material stiffness after exposition. This study demonstrates that UV aging has effects on the properties of the polypropylene polymer.

SURFACE ROUGHNESS IMPROVEMENT OF PARTS MADE OF POLYMERIC MATERIALS OBTAINED BY MEANS OF ADDITIVE TECHNOLOGIES

2021 ◽  
Vol 2021 (7) ◽  
pp. 12-18
Author(s):  
Mikhail Kulikov ◽  
Maksim Larionov ◽  
Denis Gusev ◽  
Evgeniy Shevchuk
Keyword(s):  
Surface Quality ◽  
Polymeric Materials ◽  
Additive Technologies ◽  
Abrasive Tool ◽  
Technological Basis ◽  
Dry Processing ◽  
Investigation Methods ◽  
Before And After ◽  
Part Surface ◽  
Surface Layer Quality

In the paper there is under consideration an effort to achieve the roughness index of Ra <0.8 with the aid of soft abrasive tool use. As a result the purpose of this work became development of the technology for surface quality improvement of parts manufactured with the aid of additive technologies. The authors carried out a number of experiments with the samples manufactured with the aid of the method of FDM print. With the aid of 3D Ultra 3 printer of EnvisionTec company. The samples were made of ABS-plastic in the amount of 6 pieces. On each sample there were defects after printing which contributed to the deterioration of surface quality in products. By means of TR220 profilometer there was measured roughness before and after the experiment. There was carried out dry processing and with the use of SCL. As a result, dry processing resulted in worsening surface quality, heavy wear of an abrasive tool and grain contamination. Analyzing the data obtained from the profilometer in the experiment and SCL use a considerable improvement of the surface layer quality at minimum allowance is observed. Investigation methods: in the work basis there are experimental methods of investigation. The investigations are carried out with the use of a microscope and profilometer. Processing investigation results was carried out as a result of the comparison of the measuring data obtained. Work Novelty: there are defined conditions of soft abrasive tool operation and SCL impact upon Ra indices. The results obtained indicate a possibility of Ra improvement on a part surface which is achieved due to a combined shaping with the aid of additive technologies and further machining carried out on a single technological basis. The experience without SCL use has shown the overheating possibility the result of which is a meltback and plastic sticking both on the surface, and on abrasive grains of the cutter which is inadmissible and results in considerable worsening of Ra on the surface machined and cutter wear. In view of this the SCL use in finishing is promising, but to achieve better results SCL chemistry must be improved.

Evaluation of Process Wear of Selected Tool Steels for Injection Molds

2013 ◽  
Vol 739 ◽  
pp. 171-176 ◽  
Author(s):  
František Greškovič ◽  
Ľudmila Dulebová ◽  
Branislav Duleba ◽  
Janusz W. Sikora
Keyword(s):  
Adhesive Wear ◽  
Glass Fibers ◽  
Polymeric Materials ◽  
Tool Steels ◽  
Screw Extruder ◽  
Laboratory Equipment ◽  
Before And After ◽  
Twin Screw ◽  
Weight Decrease ◽  
Short Glass

The aim of this contribution is to test the suitability of selected types of tool steels used for manufacturing of injection molds. Experiments were realized by the simulation of adhesive wear using laboratory equipment Amsler, which allows the testing of grinding pairs. Evaluated grinding pairs consisted of tool steel and two types of roundels. Tested polymeric materials were based on pure PA6 and PBT filled with short glass fibers, prepared by mixing process in twin screw extruder. The wear of five types of tool steels were evaluated by weight decrease before and after the experiment, while changing the friction coefficient of grinding pairs, material of grinding pairs and sensing the roughness of steel before and after wear.

scholarly journals Damage Constitutive Model and Mechanical Performance Deterioration of Concrete under Sulfate Environment

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Peng Liu ◽  
Ying Chen ◽  
Zhiwu Yu ◽  
Zhaohui Lu
Keyword(s):  
Mechanical Properties ◽  
Bearing Capacity ◽  
Elasticity Modulus ◽  
Mechanical Performance ◽  
Sulfate Solution ◽  
Concrete Surface ◽  
Ultimate Bearing Capacity ◽  
Stress Strain ◽  
Before And After ◽  
Relationship Model

The effects of erosion mode, erosion age, and concentration of sulfate solution on mechanical properties of concrete were investigated. The dimensionless relationship model of the stress-strain of concrete on the basis of randomness was proposed. The variation of the elasticity modulus and Poisson’s ratio of the concrete surface attacked by sulfate was studied, and a novel method of using a superficial parameter to characterize the performance change of the concrete surface was recommended. The results showed that the dimensionless relationship model of stress-strain of concrete could be used to represent the variations of mechanical properties of concrete. The differences of load-displacement of concrete before and after sulfate attack were reflected as the change of curve’s slope and ultimate bearing capacity, and the slope of a straight section of the lateral and longitudinal strain curves of concrete surface also varied. The increment rates of ultimate bearing capacity of concrete attacked by 1% and saturated sulfate solution were about 30% and 10%, respectively. However, the decreasing ratio of the ultimate bearing capacity of concrete attacked by saturated sulfate solution was approximately 25%. The damage factor of the elasticity modulus of the concrete surface of C20 and C40 was 0.185 and −0.19, respectively. The obtained results could provide a support for investigating the variations of stress-strain relationship and mechanical performance of concrete under a sulfate environment.

Bi-functional sterically hindered phenol lipid-based delivery systems as potential multi-target agents against Alzheimer's disease via an intranasal route

Nanoscale ◽  
2020 ◽  
Vol 12 (25) ◽  
pp. 13757-13770
Author(s):  
Evgenia A. Burilova ◽  
Tatiana N. Pashirova ◽  
Irina V. Zueva ◽  
Elmira M. Gibadullina ◽  
Sofya V. Lushchekina ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Intranasal Administration ◽  
Delivery Systems ◽  
Sterically Hindered Phenols ◽  
Intranasal Route ◽  
Sterically Hindered Phenol ◽  
Hindered Phenols ◽  
Hindered Phenol ◽  
Sterically Hindered

New lipid-based nanomaterials based on sterically hindered phenols were developed as potential drugs against Alzheimer's disease via intranasal administration.

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