The Photo-Oxidation of Polypropylene Monofilaments

The elongation-at-break of highly-oriented polypropylene monofilaments is much less affected by photo-oxidation build-up than undrawn or partially-oriented filaments. This appears to result from the very poor lateral cohesion of the fibril bundles in the highly-oriented filament, limiting restructuring and cracking to a thin surface layer. For less-oriented samples photo-oxidation-induced restructuring of the surface layer results in deep cracks that can propagate under stress, greatly embrittling the sample. Areas of filaments cold drawn by, for example, bending or stretching deteriorate very rapidly on uv irradiation as a result of strain-induced chromophore formation, and fracture occurs first at these points. Oxidation-product levels (either hydroperoxide or carbonyl) are shown to be an unreliable index of the extent of deterioration of mechanical properties resulting from uv exposure.

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Effect of Organic Modifier Types on the Physical–Mechanical Properties and Overall Migration of Post-Consumer Polypropylene/Clay Nanocomposites for Food Packaging

Polymers ◽

10.3390/polym13091502 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1502

Author(s):

Eliezer Velásquez ◽

Sebastián Espinoza ◽

Ximena Valenzuela ◽

Luan Garrido ◽

María José Galotto ◽

...

Keyword(s):

Mechanical Properties ◽

Food Packaging ◽

Clay Nanocomposites ◽

Organic Modifier ◽

Thermal And Mechanical Properties ◽

Chemical Safety ◽

Elongation At Break ◽

Fatty Food ◽

Recycled Plastics ◽

Thermal Stability Of

The deterioration of the physical–mechanical properties and loss of the chemical safety of plastics after consumption are topics of concern for food packaging applications. Incorporating nanoclays is an alternative to improve the performance of recycled plastics. However, properties and overall migration from polymer/clay nanocomposites to food require to be evaluated case-by-case. This work aimed to investigate the effect of organic modifier types of clays on the structural, thermal and mechanical properties and the overall migration of nanocomposites based on 50/50 virgin and recycled post-consumer polypropylene blend (VPP/RPP) and organoclays for food packaging applications. The clay with the most hydrophobic organic modifier caused higher thermal stability of the nanocomposites and greater intercalation of polypropylene between clay mineral layers but increased the overall migration to a fatty food simulant. This migration value was higher from the 50/50 VPP/RPP film than from VPP. Nonetheless, clays reduced the migration and even more when the clay had greater hydrophilicity because of lower interactions between the nanocomposite and the fatty simulant. Conversely, nanocomposites and VPP/RPP control films exhibited low migration values in the acid and non-acid food simulants. Regarding tensile parameters, elongation at break values of PP film significantly increased with RPP addition, but the incorporation of organoclays reduced its ductility to values closer to the VPP.

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Analysis of Different Complex Multilayer PACVD Coatings on Nanostructured WC-Co Cemented Carbide

Coatings ◽

10.3390/coatings11070823 ◽

2021 ◽

Vol 11 (7) ◽

pp. 823

Author(s):

Danko Ćorić ◽

Mateja Šnajdar Musa ◽

Matija Sakoman ◽

Željko Alar

Keyword(s):

Mechanical Properties ◽

Surface Layer ◽

Base Material ◽

Single Layer ◽

Production Costs ◽

Structural Defects ◽

Cemented Carbides ◽

Material System ◽

Tin Coating ◽

Ticn Coating

The development of cemented carbides nowadays is aimed at the application and sintering of ultrafine and nano-sized powders for the production of a variety of components where excellent mechanical properties and high wear resistance are required for use in high temperature and corrosive environment conditions. The most efficient way of increasing the tribological properties along with achieving high corrosion resistance is coating. Using surface processes (modification and/or coating), it is possible to form a surface layer/base material system with properties that can meet modern expectations with acceptable production costs. Three coating systems were developed on WC cemented carbides substrate with the addition of 10 wt.% Co using the plasma-assisted chemical vapor deposition (PACVD) method: single-layer TiN coating, harder multilayer gradient TiCN coating composed of TiN and TiCN layers, and the hardest multilayer TiBN coating composed of TiN and TiB2. Physical and mechanical properties of coated and uncoated samples were investigated by means of quantitative depth profile (QDP) analysis, nanoindentation, surface layer characterization (XRD analysis), and coating adhesion evaluation using the scratch test. The results confirm the possibility of obtaining nanostructured cemented carbides of homogeneous structure without structural defects such as eta phase or unbound carbon providing increase in hardness and fracture toughness. The lowest adhesion was detected for the single-layer TiN coating, while coatings with a complex architecture (TiCN, TiBN) showed improved adhesion.

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Signal Amplification in an Optical and Dielectric Biosensor Employing Liquid Crystal-Photopolymer Composite as the Sensing Medium

Biosensors ◽

10.3390/bios11030081 ◽

2021 ◽

Vol 11 (3) ◽

pp. 81

Author(s):

Hassanein Shaban ◽

Shih-Chun Yen ◽

Mon-Juan Lee ◽

Wei Lee

Keyword(s):

Dielectric Constant ◽

Liquid Crystal ◽

Uv Irradiation ◽

Signal Amplification ◽

Limit Of Detection ◽

Optical Signal ◽

Uv Exposure ◽

Dielectric Anisotropy ◽

Optical Texture ◽

Potential Development

An optical and dielectric biosensor based on a liquid crystal (LC)–photopolymer composite was established in this study for the detection and quantitation of bovine serum albumin (BSA). When the nematic LC E7 was doped with 4-wt.% NOA65, a photo-curable prepolymer, and photopolymerized by UV irradiation at 20 mW/cm2 for 300 s, the limit of detection determined by image analysis of the LC optical texture and dielectric spectroscopic measurements was 3400 and 88 pg/mL for BSA, respectively, which were lower than those detected with E7 alone (10 μg/mL BSA). The photopolymerized NOA65, but not the prepolymer prior to UV exposure, contributed to the enhanced optical signal, and UV irradiation of pristine E7 in the absence of NOA65 had no effect on the optical texture. The effective tilt angle θ, calculated from the real-part dielectric constant ε’, decreased with increasing BSA concentration, providing strong evidence for the correlation of photopolymerized NOA65 to the intensified disruption in the vertically oriented LC molecules to enhance the optical and dielectric signals of BSA. The optical and dielectric anisotropy of LCs and the photo-curable dopant facilitate novel quantitative and signal amplification approaches to potential development of LC-based biosensors.

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Low-Temperature Mechanical Properties of High-Density and Low-Density Polyethylene and Their Blends

Polymers ◽

10.3390/polym13111821 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1821

Author(s):

Ildar I. Salakhov ◽

Nadim M. Shaidullin ◽

Anatoly E. Chalykh ◽

Mikhail A. Matsko ◽

Alexey V. Shapagin ◽

...

Keyword(s):

Mechanical Properties ◽

Low Temperature ◽

Impact Strength ◽

Relative Elongation ◽

High Density ◽

Low Density Polyethylene ◽

Low Density ◽

Elongation At Break ◽

Subzero Temperatures ◽

Izod Impact

Low-temperature properties of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and their blends were studied. The analyzed low-temperature mechanical properties involve the deformation resistance and impact strength characteristics. HDPE is a bimodal ethylene/1-hexene copolymer; LDPE is a branched ethylene homopolymer containing short-chain branches of different length; LLDPE is a binary ethylene/1-butene copolymer and an ethylene/1-butene/1-hexene terpolymer. The samples of copolymers and their blends were studied by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), 13С NMR spectroscopy, and dynamic mechanical analysis (DMA) using testing machines equipped with a cryochamber. It is proposed that such parameters as “relative elongation at break at −45 °C” and “Izod impact strength at −40 °C” are used instead of the ductile-to-brittle transition temperature to assess frost resistance properties because these parameters are more sensitive to deformation and impact at subzero temperatures for HDPE. LLDPE is shown to exhibit higher relative elongation at break at −45 °C and Izod impact strength at −20 ÷ 60 °C compared to those of LDPE. LLDPE terpolymer added to HDPE (at a content ≥ 25 wt.%) simultaneously increases flow properties and improves tensile properties of the blend at −45 °C. Changes in low-temperature properties as a function of molecular weight, MWD, crystallinity, and branch content were determined for HDPE, LLDPE, and their blends. The DMA data prove the resulting dependences. The reported findings allow one to understand and predict mechanical properties in the HDPE–LLDPE systems at subzero temperatures.

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The Structure and Mechanical Properties of Hemp Fibers-Reinforced Poly(ε-Caprolactone) Composites Modified by Electron Beam Irradiation

Applied Sciences ◽

10.3390/app11125317 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5317

Author(s):

Rafał Malinowski ◽

Aneta Raszkowska-Kaczor ◽

Krzysztof Moraczewski ◽

Wojciech Głuszewski ◽

Volodymyr Krasinskyi ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Electron Beam ◽

Impact Strength ◽

Flexural Modulus ◽

Natural Fibers ◽

High Energy ◽

Electron Radiation ◽

Elongation At Break ◽

Hemp Fibers

The need for the development of new biodegradable materials and modification of the properties the current ones possess has essentially increased in recent years. The aim of this study was the comparison of changes occurring in poly(ε-caprolactone) (PCL) due to its modification by high-energy electron beam derived from a linear electron accelerator, as well as the addition of natural fibers in the form of cut hemp fibers. Changes to the fibers structure in the obtained composites and the geometrical surface structure of sample fractures with the use of scanning electron microscopy were investigated. Moreover, the mechanical properties were examined, including tensile strength, elongation at break, flexural modulus and impact strength of the modified PCL. It was found that PCL, modified with hemp fibers and/or electron radiation, exhibited enhanced flexural modulus but the elongation at break and impact strength decreased. Depending on the electron radiation dose and the hemp fibers content, tensile strength decreased or increased. It was also found that hemp fibers caused greater changes to the mechanical properties of PCL than electron radiation. The prepared composites exhibited uniform distribution of the dispersed phase in the polymer matrix and adequate adhesion at the interface between the two components.

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Effect of Moisture Content on the Processing and Mechanical Properties of a Biodegradable Polyester

Polymers ◽

10.3390/polym13101616 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1616

Author(s):

Vincenzo Titone ◽

Antonio Correnti ◽

Francesco Paolo La Mantia

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Moisture Content ◽

Mechanical Testing ◽

Hydrolytic Degradation ◽

Slight Reduction ◽

Biodegradable Polyester ◽

Molding Process ◽

Elongation At Break ◽

Effect Of Moisture

This work is focused on the influence of moisture content on the processing and mechanical properties of a biodegradable polyester used for applications in injection molding. The pellets of the biodegradable polyester were exposed under different relative humidity conditions at a constant temperature before being compression molded. The compression-molded specimens were again placed under the above conditions before the mechanical testing. With all these samples, it is possible to determine the effect of moisture content on the processing and mechanical properties separately, as well as the combined effect of moisture content on the mechanical properties. The results obtained showed that the amount of absorbed water—both before processing and before mechanical testing—causes an increase in elongation at break and a slight reduction of the elastic modulus and tensile strength. These changes have been associated with possible hydrolytic degradation during the compression molding process and, in particular, with the plasticizing action of the moisture absorbed by the specimens.

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Multicriteria Optimization of the Mechanical Properties in Laminated Seams

Materials ◽

10.3390/ma14112989 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2989

Author(s):

Halina Szafranska ◽

Ryszard Korycki

Keyword(s):

Mechanical Properties ◽

Optimization Problems ◽

Comprehensive Evaluation ◽

Relative Elongation ◽

Weighted Average ◽

Bending Rigidity ◽

Elongation At Break ◽

Lamination Process ◽

Weighted Optimization ◽

Generalized Utility

In order to ensure a comprehensive evaluation of laminated seams in working clothing, a series of research was carried out to determine the correlation between the parameters of the seam lamination process (i.e., the temperature, the time, the pressure) and the mechanical properties of laminated seams. The mechanical properties were defined by means of the maximum breaking force, the relative elongation at break and the total bending rigidity. The mechanical indexes were accepted as the measure of durability and stability of laminated seams. The correlation between the lamination process parameters and the final properties of the tested seams in working clothing was proposed using a three-factor plan 33. Finally, the single-criteria optimization was introduced and the objective functional is the generalized utility function U. Instead of three independent optimization problems, the single problem was applied, and the global objective function was a weighted average of partial criteria with the assumed weight values. The problem of multicriteria weighted optimization was solved using the determined weights and the ranges of acceptable/unacceptable values.

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Hyperbranched polyamide modified graphene oxide-reinforced polyurethane nanocomposites with enhanced mechanical properties

RSC Advances ◽

10.1039/d1ra00654a ◽

2021 ◽

Vol 11 (24) ◽

pp. 14484-14494

Author(s):

Yahao Liu ◽

Jian Zheng ◽

Xiao Zhang ◽

Yongqiang Du ◽

Guibo Yu ◽

...

Keyword(s):

Mechanical Properties ◽

Graphene Oxide ◽

High Performance ◽

Cross Linking ◽

Elongation At Break ◽

Modified Graphene Oxide ◽

High Performance Composite ◽

Modified Graphene ◽

Polyurethane Nanocomposites ◽

Hyperbranched Polyamide

We successfully modified graphene oxide with amino-terminated hyperbranched polyamide (HGO), and obtained a high-performance composite with enhanced strength and elongation at break via cross-linking hydroxyl-terminated polybutadiene chains with HGO.

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Mechanical Properties and Biocompatibility of Urethane Acrylate-Based 3D-Printed Denture Base Resin

Polymers ◽

10.3390/polym13050822 ◽

2021 ◽

Vol 13 (5) ◽

pp. 822

Author(s):

Jy-Jiunn Tzeng ◽

Tzu-Sen Yang ◽

Wei-Fang Lee ◽

Hsuan Chen ◽

Hung-Ming Chang

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Flexural Modulus ◽

Measurement Data ◽

Uv Exposure ◽

Control Group ◽

Urethane Acrylate ◽

Shore Hardness ◽

Digital Light Processing ◽

Denture Base

In this study, five urethane acrylates (UAs), namely aliphatic urethane hexa-acrylate (87A), aromatic urethane hexa-acrylate (88A), aliphatic UA (588), aliphatic urethane triacrylate diluted in 15% HDD (594), and high-functional aliphatic UA (5812), were selected to formulate five UA-based photopolymer resins for digital light processing (DLP)-based 3D printing. Each UA (40 wt%) was added and blended homogenously with ethoxylated pentaerythritol tetraacrylate (40 wt%), isobornyl acrylate (12 wt%), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (3 wt%), and a pink acrylic (5 wt%). Each UA-based resin specimen was designed using CAD software and fabricated using a DLP 3D printer to specific dimensions. Characteristics, mechanical properties, and cytotoxicity levels of these designed UA-based resins were investigated and compared with a commercial 3D printing denture base acrylic resin (BB base) control group at different UV exposure times. Shore hardness-measurement data and MTT assays were analyzed using a one-way analysis of variance with Bonferroni’s post hoc test, whereas viscosity, maximum strength, and modulus were analyzed using the Kruskal–Wallis test (α = 0.05). UA-based photopolymer resins with tunable mechanical properties were successfully prepared by replacing the UA materials and the UV exposure times. After 15 min of UV exposure, the 5812 and 594 groups exhibited higher viscosities, whereas the 88A and 87A groups exhibited lower viscosities compared with the BB base group. Maximum flexural strength, flexural modulus, and Shore hardness values also revealed significant differences among materials (p < 0.001). Based on MTT assay results, the UA-based photopolymer resins were nontoxic. In the present study, mechanical properties of the designed photopolymer resins could be adjusted by changing the UA or UV exposure time, suggesting that aliphatic urethane acrylate has good potential for use in the design of printable resins for DLP-type 3D printing in dental applications.

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Effect of Castor Oil Impregnation on the Physical and Mechanical Properties of Bacterial Cellulose

Polymers from Renewable Resources ◽

10.1177/204124791200300102 ◽

2012 ◽

Vol 3 (1) ◽

pp. 13-26

Author(s):

Myrtha Karina ◽

Lucia Indrarti ◽

Rike Yudianti ◽

Indriyati

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Bacterial Cellulose ◽

Young’S Modulus ◽

Castor Oil ◽

Young's Modulus ◽

Physical And Mechanical Properties ◽

Scanning Electron Micrographs ◽

Elongation At Break ◽

Acetone Water

The effect of castor oil on the physical and mechanical properties of bacterial cellulose is described. Bacterial cellulose (BC) was impregnated with 0.5–2% (w/v) castor oil (CO) in acetone–water, providing BCCO films. Scanning electron micrographs revealed that the castor oil penetrated the pores of the bacterial cellulose, resulting in a smoother morphology and enhanced hydrophilicity. Castor oil caused a slight change in crystallinity indices and resulted in reduced tensile strength and Young's modulus but increased elongation at break. A significant reduction in tensile strength and Young's modulus was achieved in BCCO films with 2% castor oil, and there was an improvement in elongation at break and hydrophilicity. Impregnation with castor oil, a biodegradable and safe plasticiser, resulted in less rigid and more ductile composites.

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