Mechanical Properties and Structure of Melamine Formaldehyde/Poly(Vinyl Alcohol) Molecular Composites

1989 ◽  
Vol 171 ◽  
Author(s):  
Kecheng Gong ◽  
Xinghua Zhang
Keyword(s):  
Mechanical Properties ◽  
Composite Structure ◽  
Vinyl Alcohol ◽  
Impact Resistance ◽  
Poly Vinyl Alcohol ◽  
Melamine Formaldehyde ◽  
Two Component System ◽  
Transmission Electron ◽  
Molecular Composites ◽  
The Impact

ABSTRACTThe mechanical properties and structure of melamine formaldehyde (MF)/poly(vinyl alcohol) (PVA) composites were studied in this paper. When PVA content was less than a certain value(about 20 weight %), both flexible strength and impact resistance were improved obviously. While the impact resistance improvement remained the previous trend the flexible strength didn't increase so rapidly as before when the PVA content was more than 20%. The morphology and reactivity of the prepolymer powder and the morphology of the finished specimens were investigated by means of microscope, infrared spectrum and transmission electron microscope(TEM). The results indicated that molecular composite structure was formed in this two-component system. The well-distributed PVA in this system was beneficial to the formation of the molecular composite structure. That could explain the effects of PVA on the mechanical properties and showed that the molecular composite structure are favourable for making full use of the macromolecular potentiality.

Influence of adding poly(vinyl alcohol) fibres to poly(methyl methacrylate) matrix on the fracture behaviour of fibrereinforced composites

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Vladimir Pavelka ◽  
Josef Jancar ◽  
Eva Nezbedova
Keyword(s):  
Methyl Methacrylate ◽  
Vinyl Alcohol ◽  
Fibre Composite ◽  
Impact Resistance ◽  
Charpy Impact ◽  
Critical Stress Intensity Factor ◽  
Poly Vinyl Alcohol ◽  
Special Focus ◽  
Poly Methyl Methacrylate ◽  
The Impact

AbstractThis paper reports on the relationship between structure and mechanical properties of poly(methyl methacrylate) (PMMA) reinforced with randomly oriented short poly(vinyl alcohol) (PVA) fibres. Special focus was on the effect of fibre content on the impact resistance of PMMA/PVA composites. Instrumented Charpy impact tests were carried out to characterize the impact resistance of PMMA/PVA composites. Linear elastics fracture mechanics was used to determine the dynamic critical strain energy release rate (GId) and the critical stress intensity factor (KId). Fracture surfaces were observed using scanning electron microscopy (SEM). Dynamic mechanical analysis was carried out to describe the viscoelastic response of the material. Finally, the behaviour of PMMA/PVA composites was interpreted using current short-fibre composite models. It was shown that a small amount of added PVA fibres (0.42 - 1.68 vol.-%) led to an increase of elastic modulus and yield stress under impact conditions. GId was also slightly increased, but KId remained unchanged. Good agreement was found between SEM observations and fracture toughness measured under impact loading.

scholarly journals The orthotropic viscoelastic characterisation of sub-zero 3D-printed poly(vinyl alcohol) cryogel

MRS Advances ◽  
2021 ◽  
Author(s):  
J. P. Crolla ◽  
M. M. Britton ◽  
D. M. Espino ◽  
L. E. J. Thomas-Seale
Keyword(s):  
Mechanical Properties ◽  
Vinyl Alcohol ◽  
Complex Geometry ◽  
Processing Parameters ◽  
Poly Vinyl Alcohol ◽  
Additive Manufacture ◽  
Storage And Loss Moduli ◽  
3D Printed ◽  
Orthotropic Properties ◽  
The Impact

Abstract Poly(vinyl alcohol) cryogel (PVA) is a versatile biomaterial used to replicate the biomechanics of tissues. Additive manufacture (AM) at sub-zero (°C) temperatures enables the manufacture of PVA with complex geometry; however, the effect of processing parameters on the mechanical properties of PVA has not been evaluated. The aim of this study is to understand the impact of print nozzle diameter and orientation on the viscoelastic mechanical properties of PVA. Samples of sub-zero AM PVA, with different filament thicknesses, were tested under tension relative to the print direction, to calculate the storage and loss moduli. As the nozzle size was decreased, AM PVA exhibited more pronounced orthotropic properties; the smallest size showed a 33% decrease in storage moduli when tested perpendicular to the print direction, as opposed to parallel. This study has demonstrated the ability of sub-zero AM to tailor the orthotropic properties of PVA. Graphic abstract

Preparation of poly(vinyl alcohol)/silica nanocomposties by sol-gel method

e-Polymers ◽  
2013 ◽  
Vol 13 (1) ◽  
Author(s):  
Yan-Na Zhao
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Silica Nanoparticles ◽  
Vinyl Alcohol ◽  
Sol Gel ◽  
Average Diameter ◽  
Poly Vinyl Alcohol ◽  
Hybrid Membranes ◽  
Transmission Electron ◽  
Size And Morphology

Abstract The poly(vinyl alcohol)/silica nano-composities hybrid membranes were prepared by co-hydrolysis and co-condensation of γ-glycidyloxypropyl trimethoxysilane (GPTMS) and tetraethoxysilane (TEOS) in poly(vinyl alcohol)(PVA) aqueous solution. The mechanical properties of hybrid membranes was studied, the result indicated that the well dispersion of nanoparticles was beneficial to the enhancement of the mechanical properties, and GPTMS could increase the miscibility of the polymer and SiO2. The membranes were characterized by scanning eletron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDS), 29Si CP/MAS solid-state nuclear magnatic resonance (NMR). The EDS of poly(vinyl alcohol)/silica nano-composities showed that Si element had been grafted onto the chain of PVA. The 29Si CP/MAS solidstate NMR spectra, 13C CP/MAS Solid-state NMR spectrum and EDS confirmed that silica had been introduced into the chain of PVA. Latex particle size and morphology was observed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The TEM and DLS indicated that silica nanoparticles well and regularly dispersed in PVA solution and the average diameter of silica nanoparticles dispersed in PVA solution was about 58 nm.

Effect of combined drink cans and steel fibers on the impact resistance and mechanical properties of concrete

2020 ◽  
Vol 14 (2) ◽  
pp. 6734-6742
Author(s):  
A. Syamsir ◽  
S. M. Mubin ◽  
N. M. Nor ◽  
V. Anggraini ◽  
S. Nagappan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Impact Resistance ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Indirect Tensile ◽  
The Impact

This study investigated the combine effect of 0.2 % drink cans and steel fibers with volume fractions of 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3% to the mechanical properties and impact resistance of concrete. Hooked-end steel fiber with 30 mm and 0.75 mm length and diameter, respectively was selected for this study.  The drinks cans fiber were twisted manually in order to increase friction between fiber and concrete. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the strength performance of concrete, especially the compressive strength, flexural strength and indirect tensile strength. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the compressive strength, flexural strength and indirect tensile strength by 2.3, 7, and 2 times as compare to batch 1, respectively. Moreover, the impact resistance of fiber reinforced concrete has increase by 7 times as compared to non-fiber concretes. Moreover, the impact resistance of fiber reinforced concrete consistently gave better results as compared to non-fiber concretes. The fiber reinforced concrete turned more ductile as the dosage of fibers was increased and ductility started to decrease slightly after optimum fiber dosage was reached. It was found that concrete with combination of 2% steel and 0.2% drink cans fibers showed the highest compressive, split tensile, flexural as well as impact strength.    

scholarly journals Effect of SWCNT-Tuball Paper on the Lightning Strike Protection of CFRPs and Their Selected Mechanical Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3140
Author(s):  
Kamil Dydek ◽  
Anna Boczkowska ◽  
Rafał Kozera ◽  
Paweł Durałek ◽  
Łukasz Sarniak ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Copper Foil ◽  
Impact Resistance ◽  
Mechanical Analysis ◽  
Lightning Strike ◽  
Single Wall Carbon Nanotubes ◽  
Carbon Fibre Reinforced Polymer ◽  
The Impact

The main aim of this work was the investigation of the possibility of replacing the heavy metallic meshes applied onto the composite structure in airplanes for lightning strike protection with a thin film of Tuball single-wall carbon nanotubes in the form of ultra-light, conductive paper. The Tuball paper studied contained 75 wt% or 90 wt% of carbon nanotubes and was applied on the top of carbon fibre reinforced polymer before fabrication of flat panels. First, the electrical conductivity, impact resistance and thermo-mechanical properties of modified laminates were measured and compared with the reference values. Then, flat panels with selected Tuball paper, expanded copper foil and reference panels were fabricated for lightning strike tests. The effectiveness of lightning strike protection was evaluated by using the ultrasonic phased-array technique. It was found that the introduction of Tuball paper on the laminates surface improved both the surface and the volume electrical conductivity by 8800% and 300%, respectively. The impact resistance was tested in two directions, perpendicular and parallel to the carbon fibres, and the values increased by 9.8% and 44%, respectively. The dynamic thermo-mechanical analysis showed higher stiffness and a slight increase in glass transition temperature of the modified laminates. Ultrasonic investigation after lightning strike tests showed that the effectiveness of Tuball paper is comparable to expanded copper foil.

scholarly journals Novel Hydrogels of Chitosan and Poly (vinyl alcohol) Reinforced with Inorganic Particles of Bioactive Glass

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 691
Author(s):  
O. Sánchez-Aguinagalde ◽  
Ainhoa Lejardi ◽  
Emilio Meaurio ◽  
Rebeca Hernández ◽  
Carmen Mijangos ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Drug Release ◽  
Bioactive Glass ◽  
Vinyl Alcohol ◽  
Release Kinetics ◽  
The Body ◽  
Poly Vinyl Alcohol ◽  
X Ray Diffraction ◽  
Inorganic Particles ◽  
Release Studies

Chitosan (CS) and poly (vinyl alcohol) (PVA) hydrogels, a polymeric system that shows a broad potential in biomedical applications, were developed. Despite the advantages they present, their mechanical properties are insufficient to support the loads that appear on the body. Thus, it was proposed to reinforce these gels with inorganic glass particles (BG) in order to improve mechanical properties and bioactivity and to see how this reinforcement affects levofloxacin drug release kinetics. Scanning electron microscopy (SEM), X-ray diffraction (XRD), swelling tests, rheology and drug release studies characterized the resulting hydrogels. The experimental results verified the bioactivity of these gels, showed an improvement of the mechanical properties and proved that the added bioactive glass does affect the release kinetics.

scholarly journals Fabrication of Hybrid Nanofibers from Biopolymers and Poly (Vinyl Alcohol)/Poly (ε-Caprolactone) for Wound Dressing Applications

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2104
Author(s):  
Sibusiso Alven ◽  
Blessing Atim Aderibigbe
Keyword(s):  
Mechanical Properties ◽  
Wound Healing ◽  
Vinyl Alcohol ◽  
Wound Dressing ◽  
Chronic Wounds ◽  
Cellular Adhesion ◽  
Wound Dressings ◽  
Poly Vinyl Alcohol ◽  
High Porosity ◽  
Hybrid Nanofibers

The management of chronic wounds is challenging. The factors that impede wound healing include malnutrition, diseases (such as diabetes, cancer), and bacterial infection. Most of the presently utilized wound dressing materials suffer from severe limitations, including poor antibacterial and mechanical properties. Wound dressings formulated from the combination of biopolymers and synthetic polymers (i.e., poly (vinyl alcohol) or poly (ε-caprolactone) display interesting properties, including good biocompatibility, improved biodegradation, good mechanical properties and antimicrobial effects, promote tissue regeneration, etc. Formulation of these wound dressings via electrospinning technique is cost-effective, useful for uniform and continuous nanofibers with controllable pore structure, high porosity, excellent swelling capacity, good gaseous exchange, excellent cellular adhesion, and show a good capability to provide moisture and warmth environment for the accelerated wound healing process. Based on the above-mentioned outstanding properties of nanofibers and the unique properties of hybrid wound dressings prepared from poly (vinyl alcohol) and poly (ε-caprolactone), this review reports the in vitro and in vivo outcomes of the reported hybrid nanofibers.

scholarly journals Effects of equal channel angular pressing and heat treatments on the microstructures and mechanical properties of selective laser melted and cast AlSi10Mg alloys

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Przemysław Snopiński ◽  
Mariusz Król ◽  
Marek Pagáč ◽  
Jana Petrů ◽  
Jiří Hajnyš ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Equal Channel Angular Pressing ◽  
Heat Treatments ◽  
Electron Backscattered Diffraction ◽  
Angular Pressing ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Before And After ◽  
The Impact

AbstractThis study investigated the impact of the equal channel angular pressing (ECAP) combined with heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys fabricated via selective laser melting (SLM) and gravity casting. Special attention was directed towards determining the effect of post-fabrication heat treatments on the microstructural evolution of AlSi10Mg alloy fabricated using two different routes. Three initial alloy conditions were considered prior to ECAP deformation: (1) as-cast in solution treated (T4) condition, (2) SLM in T4 condition, (3) SLM subjected to low-temperature annealing. Light microscopy, transmission electron microscopy, X-ray diffraction line broadening analysis, and electron backscattered diffraction analysis were used to characterize the microstructures before and after ECAP. The results indicated that SLM followed by low-temperature annealing led to superior mechanical properties, relative to the two other conditions. Microscopic analyses revealed that the partial-cellular structure contributed to strong work hardening. This behavior enhanced the material’s strength because of the enhanced accumulation of geometrically necessary dislocations during ECAP deformation.

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