scholarly journals Optimisation of Compression Moulding Parameter for NR/EPDM Material

2020 ◽  
Vol 9 (1) ◽  
pp. 1705-1710
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Processing Parameters ◽  
Heating Time ◽  
Cross Link ◽  
Compression Moulding ◽  
Degradation Temperature ◽  
Link Density ◽  
Cross Link Density

Natural Rubber/Ethylene Propylene Diene Monomer (NR/EPDM) elastomeric has gaining popularity in the automotive industry owing to the fact in term of sustainability. With extensive studies and an increasing number of applications for future advancement, the need for an accurate and reliable guide in processing this type of elastomer has increased enormously. The present work deals with the study of compression moulding parameters (i.e. temperature, pressure, heating time and pressure time) and its effects against NR/EPDM elastomeric mechanical properties (i.e. ultimate tensile strength (UTS), cross-link density and eccentricity error) aim on establishing optimized processing parameters setup. The optimizations are achieved through the Response Surface Methodology (RSM) and mathematical model for each response is developed to access the relationship between the parameters. Adequacy of models is analysed statistically using analysis of variance (ANOVA) in the determination of significant input variables and possible interactions. Lastly, multi objectives optimization is performed through numerical optimization and predicted results are validated. Strong agreement between experimental and the selected solution are found in between 93% and 96%, thus validating the solution as an optimal run condition. The findings suggest that temperature and heating time is the main factor affecting ultimate tensile strength, whereas for cross-link density there is only one significant parameter which is temperature. UTS and cross-link density decrease with the increases of the temperature and heating time due to the degradation (temperature too high for NR/EPDM working temperature). Therefore, it is recommended to start the process below the NR/EPDM degradation point to avoid the scissoring rubber take place and subsequently improving the mechanical properties

scholarly journals Influence of pre-heating and ceramic thickness on physical properties of luting agents

2018 ◽  
Vol 16 (4) ◽  
pp. 252-259 ◽  
Author(s):  
Michele O Lima ◽  
Anderson Catelan ◽  
Giselle M Marchi ◽  
Débora ANL Lima ◽  
Luís RM Martins ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Physical Properties ◽  
Water Sorption ◽  
Knoop Hardness ◽  
Cross Link ◽  
Luting Agents ◽  
Link Density ◽  
Cross Link Density ◽  
Ceramic Thickness

Purpose: The objective of this in vitro study was to evaluate the influence of ceramic thickness and pre-heating of luting agents on their physical properties. Materials and methods: The materials RelyX Arc, RelyX Ultimate, RelyX Veneer, and Filtek Z350 Flow were handled at different temperatures (23°C or 54°C), inserted into matrix, and photoactivated through ceramic disks (0.75 mm or 1.5 mm). The following tests were performed ( n=8): degree of conversion, Knoop Hardness, cross-link density, water sorption, solubility, and ultimate tensile strength. Data were analyzed using three-way analysis of variance and Tukey’s test (α=0.05). Results: Regarding ceramic thickness, the thinnest ceramic resulted in higher values of Knoop Hardness ( p=0.027). The lowest temperature (23°C) resulted in a higher solubility ( p=0.0257), and water sorption ( p=0.0229) values. There was also statistical difference among the materials: RelyX Arc showed a higher degree of conversion and ultimate tensile strength, followed by RelyX Veneer, RelyX Ultimate, and Filtek Z350 Flow. For Knoop Hardness and cross-link density tests, RelyX Ultimate showed the highest values, followed by RelyX Arc, RelyX Veneer, and Filtek Z350 Flow. For water sorption and solubility, RelyX Veneer showed the highest values, followed by RelyX Arc, RelyX Ultimate, and Filtek Z350 Flow. Conclusion: Pre-heating interfered with water sorption and solubility, whereas ceramic thickness only affected Knoop Hardness; the physical properties of the materials are dependent on their composition.

Boron nitride for modification of rubber based on isoprene elastomer

2020 ◽  
pp. 105-112
Author(s):  
K. S. Zhansakova ◽  
E. N. Eremin ◽  
G. S. Russkikh ◽  
O. V. Kropotin
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Gradual Increase ◽  
Physical And Mechanical Properties ◽  
Curing Time ◽  
Cross Link ◽  
Start Time ◽  
Link Density ◽  
Cross Link Density ◽  
Isoprene Rubber

The work studies vulcanization characteristics of elastomers based on isoprene rubber filled with carbon black N330 and boron nitride (BN). The influence of the boron nitride (BN) concentration on technological, dynamic, physical and mechanical properties of elastomers has been researched. The application of boron nitride for producing rubber with good properties has been considered. With a gradual increase of the inert filler BN concentration up to 35%, a decrease in the curing rate by 33% and polymer cross-link density by 26% is observed. Moreover, the start time of vulcanization increases by almost 300%, the optimal curing time by 200%.

PEG Cross-Linked Alginate Hydrogels with Controlled Mechanical Properties

1998 ◽  
Vol 530 ◽  
Author(s):  
Petra Eiselt ◽  
Jon A. Rowley ◽  
David J. Mooney
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Molecular Weight ◽  
Elastic Modulus ◽  
Cell Transplantation ◽  
Cross Linking ◽  
Cross Link ◽  
Link Density ◽  
A Cell ◽  
Cross Link Density

AbstractReconstruction of tissues and organs utilizing cell transplantation offers an attractive approach for the treatment of patients suffering from organ failure or loss. Highly porous synthetic materials are often used to mimic the function of the extracellular matrix (ECM) in tissue engineering, and serve as a cell delivery vehicle for the formation of tissues in vivo. Alginate, a linear copolysaccharide composed of D-mannuronic acid (M) and L-guluronic acid (G) units is widely used as a cell transplantation matrix. Alginate is considered to be biocompatible, and hydrogels are formed in the presence of divalent cations such as Ca2+, Ba2+ and Sr2+. However, ionically cross-linked alginate gels continuously lose their mechanical properties over time with uncontrollable degradation behavior. We have modified alginate via covalent coupling of cross-linking molecules to expand and stabilize the mechanical property ranges of these gels. Several diamino PEG molecules of varying molecular weight (200, 400, 1000, 3400) were synthesized utilizing carbodiimide chemistry. Sodium alginate was covalently cross-linked with these cross-linking molecules, and mechanical properties of the resulting hydrogels were determined. The elastic modulus of the cross-linked alginates depended on the molecular weight of the cross-linking molecules, and ranged from 10-110 kPa. The theoretical cross-link density in the hydrogels was also varied from 3 to 47% (relative to the carboxylic groups in the alginate) and the mechanical properties were measured. The elastic modulus increased gradually and reached a maximum at a cross-link density of 15%. In summary, covalently coupled hydrogels can be synthesized which exhibit a wide range of mechanical properties, and these materials may be useful in a number of tissue engineering applications.

scholarly journals Application of Peroxide Curing Systems in Cross-Linking of Rubber Magnets Based on NBR and Barium Ferrite

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Ján Kruželák ◽  
Andrea Kvasničáková ◽  
Elena Medlenová ◽  
Rastislav Dosoudil ◽  
Ivan Hudec
Keyword(s):  
Mechanical Properties ◽  
Barium Ferrite ◽  
Cross Linking ◽  
Butadiene Rubber ◽  
Cross Link ◽  
System Composition ◽  
Peroxide Curing ◽  
Link Density ◽  
Cross Link Density ◽  
Curing Systems

Rubber magnetic composites were prepared by incorporation of barium ferrite in constant amount—50 phr into acrylonitrile-butadiene rubber. Dicumyl peroxide as the curing agent was used for cross-linking of rubber magnets alone, or in combination with four different types of co-agents. The main aim was to examine the influence of curing system composition on magnetic and physical-mechanical properties of composites. The cross-link density and the structure of the formed cross-links were investigated too. The results demonstrated that the type and amount of the co-agent had significant influence on cross-link density, which was reflected in typical change of physical-mechanical properties. The tensile strength increased with increasing amount of co-agents, which can be attributed to the improvement of adhesion and compatibility on the interphase filler-rubber due to the presence of co-agents. Magnetic characteristics were found not to be influenced by the curing system composition. The application of peroxide curing systems consisting of organic peroxide and co-agents leads to the preparation of rubber magnets with not only good magnetic properties but also with improved physical-mechanical properties, which could broaden the sphere of their application uses.

Effect of cross-link density and the healing efficiency of self-healing poly(2-hydroxyethyl methacrylate) hydrogel

e-Polymers ◽  
2014 ◽  
Vol 14 (4) ◽  
pp. 289-294 ◽  
Author(s):  
Najiyyah Abdullah Sirajuddin ◽  
Mohd Suzeren Md Jamil ◽  
Muhammad Azwani Shah Mat Lazim
Keyword(s):  
Tensile Strength ◽  
Self Healing ◽  
Hydroxyethyl Methacrylate ◽  
Cross Link ◽  
Healing Efficiency ◽  
Link Density ◽  
Cross Link Density ◽  
Cross Linker ◽  
Chain Slippage ◽  
Polymerization Method

AbstractIn this study, hydrogels of poly(2-hydroxyethyl methacrylate) with different cross-link density were prepared by the free-radical polymerization method. l-Cystine, which acts as a cross-linker, was prepared at different concentrations, ranging from 0.02 to 0.08 mol/l, to identify the concentration that provided the highest mechanical strength and healing efficacy. Healing of the hydrogels was achieved by heating above their glass transition temperature. Intermolecular diffusion of the dangling chain or chain slippage led to the healing of the gels. Results showed that 0.04 mol/l of l-cystine in poly(2-hydroxyethyl methacrylate) hydrogels provided the highest ultimate tensile strength (0.780 N/mm2) and healing recovery (92%). This healing capability was also observed using optical microscopy.

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