scholarly journals Viscoelastic, Thermal, and Mechanical Properties of Melt-Processed Poly (ε-Caprolactone) (PCL)/Hydroxyapatite (HAP) Composites

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 104
Author(s):  
Mpho Phillip Motloung ◽  
Tladi Gideon Mofokeng ◽  
Suprakas Sinha Ray
Keyword(s):  
Mechanical Properties ◽  
Morphological Analysis ◽  
Specific Property ◽  
Complex Viscosity ◽  
Elongation At Break ◽  
Degradation Temperature ◽  
Extrusion Processing ◽  
Low Concentrations ◽  
Novel Material ◽  
High Concentrations

Poly (ε-caprolactone) (PCL)/hydroxyapatite (HAP) composites represent a novel material with desired properties for various applications. In this work, PCL/HAP composites at low loadings were developed through melt-extrusion processing. The effects of HAP loading on viscoelastic, thermal, structural, and mechanical properties of PCL were examined. The morphological analysis revealed better dispersion of HAP at low loadings, while aggregation was noticed at high concentrations. The complex viscosity of the prepared composites increased with increasing concentration of HAP. In addition, a significant decrease in crystallinity was observed upon increase in HAP loading. However, the elongation at break increased with increasing the concentration of HAP, probably due to a decrease in crystallinity. The onset thermal degradation temperature of PCL was enhanced at low concentrations of HAP, whereas a decrease was observed at high loading. Overall, different degrees of HAP dispersion resulted into specific property improvement.

Compatibilization of natural rubber–polypropylene thermoplastic elastomer blend

2019 ◽  
Vol 52 (8) ◽  
pp. 728-746 ◽  
Author(s):  
Abderrahmane Belhaoues ◽  
Samia Benmesli ◽  
Farid Riahi
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Morphological Analysis ◽  
Thermoplastic Elastomer ◽  
Homogeneous Distribution ◽  
Molten State ◽  
Rotor Speed ◽  
Elongation At Break ◽  
Compatibilizing Agent ◽  
Elastomer Blend

The effects of the addition of epoxidized natural rubber/maleic anhydride-grafted polypropylene blend as a compatibilizing agent (CA) on the properties of natural rubber (NR)/polypropylene (PP) thermoplastic elastomer blend were studied. The blends were prepared in the molten state at 180°C using a Brabender Plasticorder at a rotor speed of 60 r min−1. Evidence of compatibilization was obtained from the Brabender plastograms and from the mechanical properties results as well as the morphological analysis. It was found that the addition of the CA at different contents resulted in an increase of the tensile strength and Young’s modulus and a decrease of the elongation at break. It was also found that the melting temperature remained unchanged, the % crystallinity decreased, but the thermal stability was not affected. The morphology revealed a more homogeneous distribution of the dispersed PP phase for the CA-containing systems compared to the control NR/PP blend. These effects were attributed to the interactions that developed with the blend constituents through the functional groups of the CA.

scholarly journals Morphology, Rheological and Mechanical Properties of Isotropic and Anisotropic PP/rPET/GnP Nanocomposite Samples

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3058
Author(s):  
Francesco Paolo La Mantia ◽  
Vincenzo Titone ◽  
Alessandro Milazzo ◽  
Manuela Ceraulo ◽  
Luigi Botta
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Morphological Analysis ◽  
Capillary Viscometer ◽  
Melt Mixing ◽  
Elongation At Break ◽  
Recycled Polyethylene ◽  
Fibrillar Morphology ◽  
High Deformability ◽  
Poor Adhesion

The effect of graphene nanoplatelets (GnPs) on the morphology, rheological, and mechanical properties of isotropic and anisotropic polypropylene (PP)/recycled polyethylene terephthalate (rPET)-based nanocomposite are reported. All the samples were prepared by melt mixing. PP/rPET and PP/rPET/GnP isotropic sheets were prepared by compression molding, whereas the anisotropic fibers were spun using a drawing module of a capillary viscometer. The results obtained showed that the viscosity of the blend is reduced by the presence of GnP due to the lubricating effect of the graphene platelets. However, the Cox–Merz rule is not respected. Compared to the PP/rPET blend, the GnP led to a slight increase in the elastic modulus. However, it causes a slight decrease in elongation at break. Morphological analysis revealed a poor adhesion between the PP and PET phases. Moreover, GnPs distribute around the droplets of the PET phase with a honey-like appearance. Finally, the effect of the orientation on both systems gives rise not only to fibers with higher modulus values, but also with high deformability and a fibrillar morphology of the dispersed PET phase. A fragile-ductile transition driven by the orientation was observed in both systems.

scholarly journals EDIBLE WHEAT GLUTEN FILMS: DEVELOPMENT, MECHANICAL AND BARRIER PROPERTIES AND APPLICATION TO STRAWBERRIES ( Fragaria Ananassa)

2002 ◽  
Vol 20 (2) ◽  
Author(s):  
PATRICIA S. TANADA-PALMU ◽  
CARLOS GROSSO
Keyword(s):  
Mechanical Properties ◽  
Water Solubility ◽  
Oxygen Permeability ◽  
Wheat Gluten ◽  
Barrier Properties ◽  
Fragaria Ananassa ◽  
Percent Elongation ◽  
Elongation At Break ◽  
Ph Values ◽  
Low Concentrations

Filmes de glúten de trigo foram preparados em diferentes valores de pH e concentrações de glúten, etanol e glicerol. Seus efeitos sobre permeabilidade ao vapor de água e oxigênio, solubilidade em água, força de tensão e porcentagem de elongação foram avaliados usando-se a Metodologia de Superfície de Resposta. Menor permeabilidade ao oxigênio foi observada em menores concentrações de glicerol, glúten e etanol. As propriedades mecânicas foram principalmente afetadas pelas concentrações de glúten e glicerol e o filme mais resistente foi obtido quando maior concentração de glúten e menor de glicerol foram utilizadas. Coberturas de glúten de trigo aplicadas em morangos frescos reduziram as perdas de firmeza e de peso durante a estocagem em comparação com controle não revestido. Abstract Films from wheat gluten were prepared with different pH values and concentrations of gluten, ethanol and glycerol. Their effects on oxygen and water vapor permeabilities, water solubility, tensile strength and percent elongation at break were evaluated using Response Surface Methodology. The lowest oxygen permeability would be expected at low concentrations of glycerol, gluten and ethanol. The mechanical properties were mainly affected by gluten and glycerol concentrations and the most resistant film was obtained at high gluten and low glycerol concentrations. Wheat gluten coating applied to fresh strawberries reduced weight and firmness losses during storage as compared to uncoated controls.

scholarly journals Use of eco-benign periwinkle shell particle for making composites and study their effect on the thermal and mechanical properties of novel HDPE composites

2021 ◽  
Author(s):  
Abbas Saifee Valsadwala ◽  
Sriram Sriniva ◽  
Surya Rajan Balachandran ◽  
Shamshath Begum ◽  
Asit Baran Samui ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Evaluation Method ◽  
Flexural Modulus ◽  
Particle Sizes ◽  
Elongation At Break ◽  
Degradation Temperature ◽  
Extension Evaluation ◽  
Stiffening Effect ◽  
Shell Powder ◽  
Periwinkle Shell

Abstract In this investigation, the shell powder of Littorina littorea commonly called periwinkle was used as an eco-benign filler in High-Density Polyethylene (HDPE) to form periwinkle/HDPE composites (PHPC). Understanding the effect of different particle sizes of periwinkle shell powder (PSP) and optimizing their influence on PHPC is the main scope of work. Periwinkle shell (PS) particle sizes from <53 μm to 150 μm were chosen as reinforcement. The different PSP size like <53 μm, 53 μm, 75 μm, 90 μm, 105 μm and 150 μm chosen in this study were named as PHPCL53, PHPC53, PHPC75, PHPC90, PHPC105, and PHPC150 respectively. The composites were fabricated by incorporating 1 weight % of PSP into HDPE matrix using compression molding technique and then subjected to morphological, thermal, and mechanical characterizations. Morphology studies using scanning electron microscope (SEM) confirms 150 μm PSP had best dispersion whereas 75 μm PSP resulted with agglomeration. PSP had little influence on the thermal stability of HDPE except for PHPC150 which showed rise in degradation temperature when compared to the neat sample. Mechanical properties such as hardness, Young’s modulus, impact strength, and flexural modulus were enhanced by the addition of PSP. Whereas, a decrease was noted in elongation at break (%) and flexural strength of PHPC indicating the stiffening effect of filler on HDPE. In order to understand the particle size influence better, the extension evaluation method (EEM) was performed for all samples and PHPC150 was found to be the best performing among all particle sizes.

Effect of N-Phenyl-p-Phenylenediamine Modified Vegetable Oils on Properties of ENR/PP Thermoplastic Vulcanizates: A Comparative Study

2013 ◽  
Vol 844 ◽  
pp. 162-165 ◽  
Author(s):  
Chesidi Hayichelaeh ◽  
Watcharawoot Wangwon ◽  
Charoen Nakason ◽  
Anoma Thitithammawong
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Vegetable Oils ◽  
Palm Oil ◽  
Complex Viscosity ◽  
Dynamic Mechanical Properties ◽  
Elongation At Break ◽  
Thermoplastic Vulcanizates ◽  
Tan Δ

This research focuses on feasibility study of using n-phenyl-p-phenylenediamine modified vegetable oils as processing oil in the blend formulation of epoxidized natural rubber (ENR) /polypropylene (PP) thermoplastic vulcanizates (TPVs). Effect of n-phenyl-p-phenylene-diamine modified vegetable oils on tensile and dynamic mechanical properties of the ENR/PP TPVs was investigated. For a comparison purpose, vegetable oils, epoxidized vegetable oils, and white oil were selected and also used in our experiment. Results show that all types of oils used in this study did not give the TPVs with significantly different values of tensile strength. The TPVs with petrochemical based white oil obviously provided the best elongation at break and tension set. However, by using n-phenyl-p-phenylenediamine modified palm oil (pA-m-EPO) the ENR/PP TPVs showed superior elastomeric properties (higher storage modulus together with lower tension set, tan δ and complex viscosity) than those of other TPVs. This means that the pA-m-EPO performed good compatibility with the TPV and had good distribution in the ENR molecules.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

The Action of an Aniline Derivative (AN 162) on Blood Coagulation and on Platelets

1971 ◽  
Vol 26 (01) ◽  
pp. 145-166
Author(s):  
E Deutsch ◽  
K Lechner ◽  
K Moser ◽  
L Stockinger
Keyword(s):  
Blood Coagulation ◽  
Citric Acid Cycle ◽  
Second Phase ◽  
Aniline Derivative ◽  
Acid Cycle ◽  
Enhancing Effect ◽  
Low Concentrations ◽  
Dual Action ◽  
High Concentrations ◽  
Induced Aggregation

Summary1. The aniline derivative AN 162, Donau Pharmazie, Linz, Austria, has a dual action on the blood coagulation: an anticoagulant and an coagulation enhancing effect.2. The anticoagulant action may only be demonstrated with high concentrations (over 1 X 10”3 M related to plasma) preferentially in PPP. It is partially caused by an inhibition of the endogenous way of generation of the prothrombin converting principle. In addition it is suggested that it interferes with the fibrinogen-fibrin reaction in a manner not yet understood.3. The coagulant action is caused by a greater availability of platelet constituents at low concentrations of AN 162 (over 1 × 10-4 M) and by the induction of a release reaction at higher concentrations. The platelet factors 3 and 4, serotonin, adenine, and acid phosphatase are released.4. AN 162 inhibits platelet aggregation. This inhibition can be demonstrated by the PAT of Breddin and in the stirred aggregation test of Born. It is more effective to inhibit the collagen-induced and the second phase of the adrenaline-induced aggregation than the ADP induced one. The platelet retention (test of Hellem) is also reduced.5. The action of AN 162 on the platelets is caused by a damage of the platelet membrane which becomes permeabel for both, soluble platelet constitutents and granula.6. AN 162 interferes with the energy metabolism of the platelets. It causes a loss of ATP, and inhibits the key-enzymes of glycolysis, citric acid cycle, fatty acid oxydation and glutathione reduction.7. AN 162 inhibits the growth of fibroblasts without influence on mitosis.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

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