New Developments in Dynamically Cured PP—EPDM Blends

2001 ◽  
Vol 74 (2) ◽  
pp. 211-220 ◽  
Author(s):  
Miguel A. López-Manchado ◽  
Miguel Arroyo ◽  
José M. Kenny
Keyword(s):  
Mechanical Properties ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Dynamic Vulcanization ◽  
New Developments ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Ethylene Propylene Diene Terpolymer ◽  
Vulcanization Process

Abstract Different procedures for preparing thermoplastic vulcanizates (TPVs), based on isotactic polypropylene (iPP) and ethylene—propylene—diene terpolymer rubber (EPDM), are used and analyzed in this work. In order to determine the effect of the vulcanization method on material properties, a rheological study, dynamic-mechanical analysis, mechanical properties and morphological study have been carried out. In all cases, the sulfur is used as crosslinking agent of the elastomeric phase. It has been shown that the dynamically cured blends (referred in the work as V2 and V3) present better properties in relation to those statically cured (V1) and uncrosslinked (V). Thus, the elastic ability, mechanical properties and rheological characteristics of these systems sensibly increase when the samples are dynamically vulcanized. Morphological analysis performed by scanning electron microscopy (SEM) is clearly in agreement with the analyzed properties, showing a better dispersion between both polymeric chains, when the blends are dynamically cured. These results seem to indicate that the dynamic vulcanization process gives rise to the formation of a thermally stable three-dimensional network, and as a consequence of it, a sensible increase of the properties is obtained.

Mechanochemical Devulcanization of Vulcanized Gum Natural Rubber

2005 ◽  
Vol 21 (3) ◽  
pp. 183-199
Author(s):  
G.K. Jana ◽  
C.K. Das
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Three Dimensional ◽  
Elongation At Break ◽  
Tear Strength ◽  
Vulcanized Rubber ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Cure Time

De-vulcanization of vulcanized elastomers represents a great challenge because of their three-dimensional network structure. Sulfur-cured gum natural rubbers containing three different sulfur/accelerator ratios were de-vulcanized by thio-acids. The process was carried out at 90 °C for 10 minutes in an open two-roll cracker-cum-mixing mill. Two concentrations of de-vulcanizing agent were tried in order to study the cleavage of the sulfidic bonds. The mechanical properties of the re-vulcanized rubber (like tensile strength, modulus, tear strength and elongation at break) were improved with increasing concentrations of de-vulcanizing agent, because the crosslink density increased. A decrease in scorch time and in optimum cure time and an increase in the state of cure were observed when vulcanized rubber was treated with high amounts of de-vulcanizing agent. The temperature of onset of degradation was also increased with increasing concentration of thio-acid. DMA analysis revealed that the storage modulus increased on re-vulcanization. From IR spectroscopy it was observed that oxidation of the main polymeric chains did not occur at the time of high temperature milling. Over 80% retention of the original mechanical properties (like tensile strength, modulus, tear strength and elongation at break) of the vulcanized natural rubber was achieved by this mechanochemical process.

Use of Benzene-1,3-Bis(Sulfonyl)Azide as Crosslinking Agent of TPVs Based on EPDM Rubber—Polyolefin Blends

2001 ◽  
Vol 74 (2) ◽  
pp. 198-210 ◽  
Author(s):  
Miguel A. López Manchado ◽  
José M. Kenny†
Keyword(s):  
Crosslinking Agent ◽  
Thermal Characterization ◽  
Chain Scission ◽  
Dynamic Vulcanization ◽  
Polyolefin Blends ◽  
Thermoplastic Matrix ◽  
Sulfonyl Azide ◽  
Preliminary Study ◽  
Ethylene Propylene Diene Terpolymer ◽  
Vulcanization Process

Abstract The use of innovative crosslinking agents for the preparation of thermoplastic vulcanizates (TPVs) is investigated. In this preliminary study, the most common TPV systems, based on polypropylene (iPP) and ethylene—propylene—diene terpolymer rubber (EPDM) blends, are studied. Among typical vulcanization agents, only the peroxides are able to crosslink saturated elastomers, however, they present the disadvantage that give rise to chain scission of the thermoplastic matrix. For this reason, the main goal of the present study is to investigate a new vulcanization agent for elastomeric matrices, which also permit the dynamic vulcanization process in their blends with polyolefins. This agent is based on a diazide derivative, benzene-1,3-bis(sulfonyl)azide that, for the specific behavior of the sulfonyl azide group, allows its interaction with the carbon—hydrogen bonds of the elastomeric phase and of the polyolefin. The study includes the dynamic vulcanization of PP—EPDM blends and their rheological, mechanical and thermal characterization. A comparison with traditional TPVs prepared with sulfur as vulcanization agent is also presented.

Development of a Collagen/Clay Nanocomposite Biomaterial

2012 ◽  
Vol 706-709 ◽  
pp. 461-466 ◽  
Author(s):  
Alejandra Reyna-Valencia ◽  
P. Chevallier ◽  
D. Mantovani
Keyword(s):  
Mechanical Properties ◽  
Aqueous Media ◽  
Three Dimensional ◽  
Clay Particles ◽  
Network Characteristics ◽  
Polymer Molecules ◽  
Nanocomposite Hydrogels ◽  
Clay Concentration ◽  
Dimensional Network ◽  
Collagen Hydrogels

Collagen hydrogels are widely used as three-dimensional scaffolds for cells and tissue in culture environments. These materials, which consist of crosslinked biopolymer (protein-based) networks in aqueous media, are particularly suitable for recreating part of the extra-cellular matrix, but their poor mechanical properties represent a major limitation. One strategy to enhance the strength of this kind of hydrogels might be to incorporate clay nanoscopic particles. In fact, it has been observed that the charged surface of clay nanosheets can interact with certain functional groups belonging to polymer molecules, yielding stronger networks. Moreover, clay particles are recognized to be biocompatible. In the present work, the gelation process and the resulting morphological and mechanical properties of collagen/laponite clay nanocomposite hydrogels were invastigated. Upon gelation, the biopolymer molecules assemble into nanoscale fibrils, which bundle into fibers and entangle into a three-dimensional network. The network characteristics depend on tunable parameters such as pH and clay concentration.

scholarly journals catena-Poly[potassium-di-μ-aqua-μ-4-(5-tetrazolio)pyridine]

2009 ◽  
Vol 65 (6) ◽  
pp. m671-m671
Author(s):  
Li-Jing Cui
Keyword(s):  
Hydrothermal Reaction ◽  
Three Dimensional ◽  
Organic Ligand ◽  
Water Molecules ◽  
Coordination Environment ◽  
Dimensional Network ◽  
Centroid Distance ◽  
Distorted Octahedral ◽  
Polymeric Chains ◽  
Distorted Octahedral Coordination Environment

The title compound, [K(C6H4N5)(H2O)2]n, was synthesized by hydrothermal reaction of KOH with 4-(5-tetrazolio)pyridine. The K atom has a distorted octahedral coordination environment and is coordinated by two axial N atoms from the organic ligand and by four water molecules in the equatorial plane. The molecules as a whole are located on crystallographic mirror planes; the K atom is also located on an inversion center. Both the water molecules and the organic ligands act as bridges to link symmetrically the adjacent K atoms into polymeric chains parallel to thecaxis. O—H...N hydrogen bonds involving the water O atoms and aromatic π–π interactions [centroid–centroid distance 3.80 (2) Å] between the pyridine and tetrazole rings build up an infinite three-dimensional network.

scholarly journals catena-Poly[[aquabis(4-formylbenzoato-κ2O1,O1′)cadmium]-μ-pyrazine-κ2N:N′]

2014 ◽  
Vol 70 (2) ◽  
pp. m37-m38 ◽  
Author(s):  
Fatih Çelik ◽  
Nefise Dilek ◽  
Nagihan Çaylak Delibaş ◽  
Hacali Necefoğlu ◽  
Tuncer Hökelek
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Benzene Ring ◽  
Three Dimensional ◽  
Dihedral Angles ◽  
Carboxylate Group ◽  
Bidentate Ligands ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Benzene Rings

The polymeric title compound, [Cd(C8H5O3)2(C4H4N2)(H2O)]n, contains two 4-formylbenzoate (FB) anions, one pyrazine molecule and one coordinating water molecule; the FB anions act as bidentate ligands. The O atom, the aldehyde H atom and the benzene ring of one of the FB anions are disordered over two positions. The O atoms were freely refined [refined occupancy ratio 0.79 (2):0.21 (2)], while the aldehyde H atoms and the benzene ring atoms were refined with fixed occupancy ratios of 0.8:0.2 and 0.5:0.5, respectively. In the ordered FB anion, the carboxylate group is twisted away from the attached benzene ring (A) by 22.7 (8)°. In the disordered FB anion, the corresponding angles are 15.6 (10) and 11.4 (11)° for ringsBandB′, respectively. Benzene ringsAandBare oriented at a dihedral angle of 24.2 (7),AandB′ at 43.0 (8)°. The pyrazine ring makes dihedral angles of 67.5 (4), 89.6 (7) and 86.2 (7)°, respectively, with benzene ringsA,BandB′. The pyrazine ligands bridge the CdIIcations, forming polymeric chains running along theb-axis direction. In the crystal, O—Hwater... Ocarboxylatehydrogen bonds link adjacent chains into layers parallel to thebcplane. These layers are linkedviaC—Hpyrazine... Oformylhydrogen bonds, forming a three-dimensional network. π–π interactions [centroid–centroid distances = 3.870 (11)–3.951 (5) Å] further stabilize the crystal structure. There is also a weak C—H...π interaction present.

Proanthocyanidin as a crosslinking agent for fibrin, collagen hydrogels and their composites with decellularized Wharton’s-jelly-extract for tissue engineering applications

2020 ◽  
Vol 35 (6) ◽  
pp. 554-571
Author(s):  
Elham Hasanzadeh ◽  
Narges Mahmoodi ◽  
Arefeh Basiri ◽  
Faezeh Esmaeili Ranjbar ◽  
Zahra Hassannejad ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Biomedical Application ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Wharton’S Jelly ◽  
The Body ◽  
Grape Seeds ◽  
Wharton's Jelly ◽  
Collagen Hydrogels

In tissue engineering, natural hydrogel scaffolds gained considerable attention due to their biocompatibility and similarity to macromolecular-based components in the body. However, their low mechanical strength and high degradation degree limit their biomedical application. By varying the composition of hydrogels, their biochemical and mechanical properties can be improved. In this study, the stability of fibrin and collagen hydrogels and their composites with decellularized Wharton’s jelly extract (DEWJ) was improved using proanthocyanidin (PA) as a cross-linker, extracted from grape seeds. The cytocompatibility, physicochemical and mechanical properties of the hydrogels were evaluated. Human endometrial stem cells (hEnSCs) were seeded on the hydrogels and their attachment, morphology, and proliferation were investigated using a scanning electron and optical microscopy. Our results showed that hydrogels containing DEWJ along with PA enhance cell proliferation and showed higher mechanical properties compared with the fibrin and collagen hydrogel. The results present the potential utility of these hydrogels in tissue engineering and for application in three-dimensional culture.

scholarly journals Effect of Ethylenediaminetetraacetic Acid on Unsaturated Poly(Butylene Adipate-Co-Butylene Itaconate) Copolyester with Low-Melting Point and Controllable Hardness

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 611 ◽  
Author(s):  
Chin-Wen Chen ◽  
Te-Sheng Hsu ◽  
Syang-Peng Rwei
Keyword(s):  
Melting Point ◽  
Textile Industry ◽  
Ethylenediaminetetraacetic Acid ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Uv Curing ◽  
Plastic Properties ◽  
Smart Textile ◽  
Dimensional Network

A series of copolyesters, poly(butylene adipate-co-butylene itaconate) (PBABI), was synthesized using melt polycondensation from adipic acid (AA), itaconic acid (IA), 1,4-butanediol (1,4-BDO), and ethylenediaminetetraacetic acid (EDTA). 1H-NMR, FT-IR, GPC, DSC, TGA, DMA, XRD, Shore D, and tensile test were used to systematically characterize the structural and composition/physical properties of the copolyesters. It was found that the melting point (Tm) and crystallization temperature (Tc) of the copolyesters were, respectively, between 21.1 to 57.5 °C and −6.7 to 29.5 °C. The glass transition (Tg) and the initial thermal decomposition (Td-5%) temperatures of the PBABI copolyesters were observed to be between −53.6 to −55.8 °C and 313.6 and 342.1 °C at varying ratios of butylene adipate (BA) and butylene itaconate (IA), respectively. The XRD feature peak was identified at the 2θ values of 21.61°, 22.31°, and 23.96° for the crystal lattice of (110), (020), and (021), respectively. Interestingly, Shore D at various IA ratios had high values (between 51.3 to 62), which indicated that the PBABI had soft plastic properties. The Young’s modulus and elongation at break, at different IA concentrations, were measured to be at 0.77–128.65 MPa and 71.04–531.76%, respectively, which could be attributed to a close and compact three-dimensional network structure formed by EDTA as a crosslinking agent. There was a significant bell-shaped trend in a BA/BI ratio of 8/2, at different EDTA concentrations—the ∆Hm increased while the EDTA concentration increased from 0.001 to 0.05 mole% and then decreased at an EDTA ratio of 0.2 mole%. Since the PBABI copolymers have applications in the textile industry, these polymers have been adopted to reinforce 3D air-permeable polyester-based smart textile. This kind of composite not only possesses the advantage of lower weight and breathable properties for textiles, but also offers customizable, strong levels of hardness, after UV curing of the PBABI copolyesters, making its potential in vitro orthopedic support as the “plaster of the future”.

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