scholarly journals Tunable Crystalline Phases in UV-Curable PEG-Grafted Ladder-Structured Silsesquioxane/Polyimide Composites

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2295 ◽  
Author(s):  
Ryung Il Kim ◽  
Ju Ho Shin ◽  
Jong Suk Lee ◽  
Jung-Hyun Lee ◽  
Albert S. Lee ◽  
...  
Keyword(s):  
Polymer Composites ◽  
Surface Properties ◽  
Weight Ratio ◽  
Hybrid Polymer ◽  
Water Contact ◽  
Uv Curable ◽  
Wide Range ◽  
Drastic Increase ◽  
Polyimide Composites ◽  
Crystalline Polyethylene

A series of UV-curable hybrid composite blends containing a carboxylic acid functionalized polyimidewith varying amounts of high molecular weight (~1 K) PEG-grafted ladder-structured polysilsesquioxanes copolymerized with methacryl groups were fabricated and their structural, thermal, mechanical, and surface properties characterized. At a composite weight ratio of polyimide above 50 wt.%, a stark shift from amorphous to crystalline polyethylene glycol (PEG) phases were observed, accompanied by a drastic increase in both surface moduli and brittleness index. Moreover, fabricated composites were shown to have a wide range water contact angle, 9.8°–73.8°, attesting to the tunable surface properties of these amphiphilic hybrid polymer composites. The enhanced mechanical properties, combined with the utility of tunable surface hydrophilicity allows for the possible use of these hybrid polymer composites to be utilized as photosensitive polyimide negative photoresists for a myriad of semiconductor patterning processes.

The Wetting of Insect Cuticles by Water

1955 ◽  
Vol 32 (3) ◽  
pp. 591-617 ◽  
Author(s):  
M. W. HOLDGATE
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Surface Properties ◽  
Surface Composition ◽  
Contact Angles ◽  
Aquatic Species ◽  
Water Contact ◽  
Calliphora Erythrocephala ◽  
Wetting Properties ◽  
Wide Range

1. The water contact angles of insects show a wide range of variation, which is broadly correlated with surface roughness and with habitat. 2. The contact angles of species inhabiting stored products or carrion are greatly modified by contamination. This produces large variations between apparently similar individuals. 3. In terrestrial insects surface roughness increases the contact angles to very large apparent values. Detailed analyses of its effect have been made in the pupa of Tenebrio molitor and the adult Calliphora erythrocephala. In some aquatic insects surface roughness leads to a reduction in the contact angles; this has been studied in the nymph of Anax imperator. 4. Prolonged immersion in water causes a lowering of the contact angles of all the insects examined, and the low angles of many aquatic species may therefore be the direct effect of their environment. In some aquatic species there is evidence of the active maintenance of a large contact angle during life. 5. Changes in contact angle accompany processes of cuticle secretion and will occur at any moult if changes in roughness or habitat take place. 6. The observed variations of surface properties can be explained without assuming any variation in the chemical composition of the cuticle surface. Wetting properties are of little value as indicators of cuticle surface composition. 7. The biological aspects of insect surface properties are briefly discussed.

Investigations on Machinability and Machining Characteristics of Hybrid Polymer

2014 ◽  
Vol 592-594 ◽  
pp. 461-466 ◽  
Author(s):  
J. Revanthkumar ◽  
Rama Kishore G. Babu ◽  
M. Thirupathi Reddy ◽  
G. Venkatachalam ◽  
A.K. Jeevanantham
Keyword(s):  
Surface Roughness ◽  
Polymer Composites ◽  
Volume Fraction ◽  
Cutting Speed ◽  
Weight Ratio ◽  
Dimensional Accuracy ◽  
Surface Characteristics ◽  
Depth Of Cut ◽  
Hybrid Polymer ◽  
Cashew Nut Shell Liquid

One of the interests in machining is to attain better surface roughness with dimensional accuracy. Polymer composites has been continuously dispatching the conventional materials. Polymer based composites have superior mechanical strength and stiffness such as strength-to-weight ratio, high stiffness-to-weight ratio. Polymer composites are the one which are produced closer to the required shape and further machining is often necessary to achieve the expected surface characteristics. This study targets the machining of hybrid polymer, made in the form of round rod, using general purpose resin and cashew nut shell liquid with varying proportions of CSNL by volume fraction up to 30%. Machining is carried out and the study includes the influence of the various process parameters such as cutting speed and feed with depth of cut kept constant and their importance in deciding the surface roughness. Surface roughness was measured after machining under specified measuring conditions using Talysurf.

Laser-Induced Nanocarbon Formation for Tuning Surface Properties of Commercial Polymers

2020 ◽  
Author(s):  
Moataz Abdulhafez ◽  
Angela J. McComb ◽  
Mostafa Bedewy
Keyword(s):  
Contact Angle ◽  
Surface Properties ◽  
Surface Characterization ◽  
Surface Engineering ◽  
Surface Hydrophobicity ◽  
Contact Angles ◽  
Structure Property ◽  
Water Contact ◽  
Wide Range ◽  
Commercial Polymers

Abstract The growth of laser-induced nanocarbons, referred to here are LINC for short, directly on polymeric surfaces is a promising route toward surface engineering of commercial polymers. This paper aims to demonstrate how this new approach can enable achieving varied surface properties based on tuning the nanostructured morphology of the formed graphitic material on commercial polyimide (Kapton) films. We elucidate the effects of tuning laser processing parameters on the achieved nanoscale morphology and the resulting surface hydrophobicity or hydrophilicity. Our results show that by varying lasing power, rastering speed, laser spot size, and line-to-line gap sizes, a wide range of water contact angles are possible, i.e. from below 20° to above 110°. Combining water contact angle measurements from an optical tensiometer with LINC surface characterization using optical microscopy, electron microscopy, and Raman spectroscopy enables building the process-structure-property relationship. Our findings reveal that both the value of contact angle and the anisotropic wetting behavior of LINC on polyimide are dependent on their hierarchical surface nanostructure which ranges for isotropic nanoporous morphology to fibrous morphology. Results also show that increasing gap sizes lead to an increase in contact angles and thus an increase in the hydrophobicity of the surface. Hence, our work highlight the potential of this approach for manufacturing flexible devices with tailored surfaces.

scholarly journals Wide-Range Magnetoelectric Response on Hybrid Polymer Composites Based on Filler Type and Content

Polymers ◽  
2017 ◽  
Vol 9 (12) ◽  
pp. 62 ◽  
Author(s):  
Pedro Martins ◽  
Marco Silva ◽  
Silvia Reis ◽  
Nélson Pereira ◽  
Harvey Amorín ◽  
...  
Keyword(s):  
Polymer Composites ◽  
Hybrid Polymer ◽  
Wide Range ◽  
Magnetoelectric Response

Hybrid polymer composite materials. Part 2. Preparation technology

2020 ◽  
pp. 8-13
Keyword(s):  
Composite Materials ◽  
Impact Toughness ◽  
Polymer Composites ◽  
The Other ◽  
Polymer Materials ◽  
Hybrid Polymer ◽  
Preparation Technology ◽  
Advantages And Disadvantages ◽  
Hybrid Polymer Composite ◽  
The One

The main methods (pressing and winding) of the processing of hybrid polymer composites to obtain items were examined. Advantages and disadvantages of the methods were noted. Good combinations of different-module fibers (carbon, glass, boron, organic) in hybrid polymer materials are described, which allow one to prepare materials with high compression strength on the one hand, and to increase fracture energy of samples and impact toughness on the other hand.

scholarly journals On the Effectiveness of Oxygen Plasma and Alkali Surface Treatments to Modify the Properties of Polylactic Acid Scaffolds

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1643
Author(s):  
Ricardo Donate ◽  
María Elena Alemán-Domínguez ◽  
Mario Monzón
Keyword(s):  
Surface Properties ◽  
Enzymatic Degradation ◽  
Oxygen Plasma ◽  
Physicochemical Characterization ◽  
Surface Treatments ◽  
Carboxyl Groups ◽  
Scanning Calorimetry ◽  
Water Contact ◽  
Angle Measurements ◽  
3D Printed

Surface modification of 3D-printed PLA structures is a major issue in terms of increasing the biofunctionality and expanding the tissue engineering applications of these parts. In this paper, different exposure times were used for low-pressure oxygen plasma applied to PLA 3D-printed scaffolds. Alkali surface treatments were also evaluated, aiming to compare the modifications introduced on the surface properties by each strategy. Surface-treated samples were characterized through the quantification of carboxyl groups, energy-dispersive X-ray spectroscopy, water contact angle measurements, and differential scanning calorimetry analysis. The change in the surface properties was studied over a two-week period. In addition, an enzymatic degradation analysis was carried out to evaluate the effect of the surface treatments on the degradation profile of the 3D structures. The physicochemical characterization results suggest different mechanism pathways for each type of treatment. Alkali-treated scaffolds showed a higher concentration of carboxyl groups on their surface, which enhanced the enzymatic degradation rate, but were also proven to be more aggressive towards 3D-printed structures. In contrast, the application of the plasma treatments led to an increased hydrophilicity of the PLA surface without affecting the bulk properties. However, the changes on the properties were less steady over time.

scholarly journals Loading Effect of Sol-Gel Derived Barium Hexaferrite on Magnetic Polymer Composites

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 558
Author(s):  
Thanida Charoensuk ◽  
Wannisa Thongsamrit ◽  
Chesta Ruttanapun ◽  
Pongsakorn Jantaratana ◽  
Chitnarong Sirisathitkul
Keyword(s):  
Polymer Composites ◽  
Sol Gel ◽  
Weight Ratio ◽  
Barium Hexaferrite ◽  
Acrylonitrile Butadiene Styrene ◽  
Combustion Method ◽  
Casting Method ◽  
Auto Combustion ◽  
Solution Casting Method ◽  
Butadiene Styrene

Solution–processing methods were investigated as viable alternatives to produce the polymer-bonded barium hexaferrite (BaM). BaM powders were first synthesized by using the sol-gel auto-combustion method. While the ignition period in two synthesis batches varied, the morphology of hexagonal microplates and nanorods, as well as magnetic properties, were reproduced. To prepare magnetic polymer composites, these BaM powders were then incorporated into the acrylonitrile-butadiene-styrene (ABS) matrix with a weight ratio of 80:20, 70:30, and 60:40 by using the solution casting method. Magnetizations were linearly decreased with a reduction in ferrite loading. Compared to the BaM loose powders and pressed pellet, both remanent and saturation magnetizations were lower and gave rise to comparable values of the squareness. The squareness around 0.5 of BaM samples and their composites revealed the isotropic alignment. Interestingly, the coercivity was significantly increased from 1727–1776 Oe in loose BaM powders to 1874–2052 Oe for the BaM-ABS composites. These composites have potential to be implemented in the additive manufacturing of rare-earth-free magnets.

scholarly journals Sequential Laser–Mechanical Drilling of Thick Carbon Fibre Reinforced Polymer Composites (CFRP) for Industrial Applications

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2136
Author(s):  
Sharizal Ahmad Sobri ◽  
Robert Heinemann ◽  
David Whitehead
Keyword(s):  
Carbon Fibre ◽  
Polymer Composites ◽  
Weight Ratio ◽  
High Strength ◽  
Industrial Applications ◽  
Fibre Laser ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Thrust And Torque

Carbon fibre reinforced polymer composites (CFRPs) can be costly to manufacture, but they are typically used anywhere a high strength-to-weight ratio and a high steadiness (rigidity) are needed in many industrial applications, particularly in aerospace. Drilling composites with a laser tends to be a feasible method since one of the composite phases is often in the form of a polymer, and polymers in general have a very high absorption coefficient for infrared radiation. The feasibility of sequential laser–mechanical drilling for a thick CFRP is discussed in this article. A 1 kW fibre laser was chosen as a pre-drilling instrument (or initial stage), and mechanical drilling was the final step. The sequential drilling method dropped the overall thrust and torque by an average of 61%, which greatly increased the productivity and reduced the mechanical stress on the cutting tool while also increasing the lifespan of the bit. The sequential drilling (i.e., laser 8 mm and mechanical 8 mm) for both drill bits (i.e., 2- and 3-flute uncoated tungsten carbide) and the laser pre-drilling techniques has demonstrated the highest delamination factor (SFDSR) ratios. A new laser–mechanical sequence drilling technique is thus established, assessed, and tested when thick CFRP composites are drilled.

scholarly journals The Influence of Valve-Pump Weight Ratios on the Dynamic Response of Leaking Valve-Pump Parallel Control Hydraulic Systems

2018 ◽  
Vol 8 (7) ◽  
pp. 1201 ◽  
Author(s):  
Haigang Ding ◽  
Jiyun Zhao ◽  
Gang Cheng ◽  
Steve Wright ◽  
Yufeng Yao
Keyword(s):  
Dynamic Response ◽  
Hydraulic System ◽  
Weight Ratio ◽  
Open Loop ◽  
Hydraulic Systems ◽  
Variable Speed ◽  
Weight Factors ◽  
Wide Range ◽  
Parallel Control ◽  
Valve Control

A new leaking valve-pump parallel control (LVPC) oil hydraulic system is proposed to improve the performance of dynamic response of present variable speed pump control (VSPC) system, which is an oil hydraulic control system with saving energy. In the LVPC, a control valve is operating at leaking status, together with a variable speed pump, to regulate the system flow of hydraulic oil simultaneously. Therefore, the degree of valve control and pump control can be adjusted by regulating the valve-pump weight ratio. The LVPC system design, mathematical model development, system parameter and control performance analysis are carried out systematically followed by an experimental for validation process. Results have shown that after introducing the valve control, the total leakage coefficient increases significantly over a wide range with the operating point and this further increases damping ratios and reduces the velocity stiffness. As the valve-pump weight ratio determines the flow distribution between the valve and the pump and the weight factors of the valve and/or the pump controls determines the response speed of the LVPC system, thus if the weight factors are constrained properly, the LVPC system will eventually have a large synthetic open-loop gain and it will respond faster than the VSPC system. The LVPC will enrich the control schemes of oil hydraulic system and has potential value in application requiring of fast response.

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