Characterization of the Aging Behavior of Microorganism Coagulated Natural Rubber

2011 ◽  
Vol 287-290 ◽  
pp. 1517-1520 ◽  
Author(s):  
Wen Jie Luo ◽  
Si Dong Li ◽  
Shuang Quan Liao ◽  
Lin Fang ◽  
Zhi Fen Wang
Keyword(s):  
Relaxation Time ◽  
Shear Rate ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Complex Viscosity ◽  
Damping Factor ◽  
Aging Behavior ◽  
Frequency Sweep ◽  
Strain Sweep

The characterization of the aging behavior of raw natural rubber (NR) coagulated by microorganisms (NR-m) was performed on a rubber processing analyzer (RPA) by tests of frequency sweep, strain sweep and stress relaxation, respectively. With the prolongation of the aging time, the storage modulus (G'), storage torque (S'), complex viscosity (η*) and stress relaxation time of raw NR-m decreased while the damping factor (tanδ) were increased. As the oscillation frequency was increasing, the G' rose gradually but the tanδ decreased. The η*diminished over the whole range of frequency shear rate (γƒ) values. Its change remained all almost the same at low strain shear rate (γs) but began to decrease sharply when the rate reached a higher value. The S' soared up in the region of less than 10°, but began to slow down after that point.

scholarly journals Rheological Characterization of Alginate Based Hydrogels for Tissue Engineering

MRS Advances ◽  
2017 ◽  
Vol 2 (24) ◽  
pp. 1309-1314 ◽  
Author(s):  
Pengfei Duan ◽  
Nehir Kandemir ◽  
Jiajun Wang ◽  
Jinju Chen
Keyword(s):  
Mechanical Properties ◽  
Drug Delivery ◽  
Tissue Engineering ◽  
Drug Delivery Systems ◽  
Rheological Characteristics ◽  
Scaffold Material ◽  
Rheological Characterization ◽  
Frequency Sweep ◽  
Strain Sweep

ABSTRACTHydrogels have been widely used in many applications from tissue engineering to drug delivery systems. For both tissue engineering and drug delivery, the mechanical properties are important because they would affect cell-materials interactions and injectability of drugs encapsulated in hydrogel carriers. Therefore, it is important to study the mechanical properties of these hydrogels, particularly at physiological temperature (37°C). This study adopted strain sweep and frequency sweep rotational rheological tests to investigate the rheological characteristics of various tissue engineering relevant hydrogels with different concentrations at 37°C. These hydrogels include alginate, RGD-alginate, and copolymerized collagen/alginate/fibrin. It has revealed that the addition of RGD has negligible effect on the elastic modulus and viscosity of alginate. Alginate gels have demonstrated shear thinning behavior which indicates that they are suitable candidates as carriers for cells or drug delivery. The addition of collagen and fibrin would reinforce the mechanical properties of alginate which makes it a strong scaffold material.

Compatibilization of NR/EVA blends by natural rubber grafted poly(dimethyl(methacryloyloxymethyl)phosphonate) compatibilizer

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Punyanich. Intharapat ◽  
Daniel Derouet ◽  
Frédéric Gohier ◽  
Charoen Nakason
Keyword(s):  
Natural Rubber ◽  
Complex Viscosity ◽  
Dynamic Mechanical Properties ◽  
Continuous Phase ◽  
Morphological Properties ◽  
Elastic Response ◽  
Damping Factor ◽  
Phase System ◽  
Dynamic Mechanical ◽  
Loading Level

AbstractGraft copolymer of natural rubber (NR) and poly(dimethyl (methacryloyloxymethyl) phosphonate (PDMMMP) (i.e., NR-g-PDMMMP) was prepared and used as a blend compatibilizer in 50/50 NR/EVA simple blends. Influence of various loading levels of NR-g-PDMMMP (i.e., 0, 1, 3, 5, 7, 9, 12 and 15 wt% of NR) on rheological, dynamic, mechanical and morphological properties was investigated. The results showed that the best compatibilization effect was observed in the blend with a loading level of NR-g-PDMMMP at 7 wt%. That is, the highest complex viscosity, tensile strength, elongation at break as well as the lowest values of tension set and tan δ value (i.e., damping factor) were observed. This indicates the highest mechanical strength and the supreme elastic response of the material. Morphological properties of 50/50 NR/EVA blends with any loading levels of NR-g-PDMMMP compatibilizer showed co-continuous phase system. However, in the NR/EVA blend with NR-g-PDMMMP at a loading level of 7 wt%, the finest phase morphology was observed. The 50/50 NR/EVA blend with lower and higher loading amounts of NR-g-PDMMMP compatibilizer exhibited inferior dynamic, mechanical properties as well as larger phase morphologies.

Characterization the Relationship between Rheology Behavior and Moleculer Weight of Natural Rubber with Different Protein Content

2011 ◽  
Vol 337 ◽  
pp. 285-288
Author(s):  
Tian Ming Gao ◽  
Rui Hong Xie ◽  
Pu Wang Li ◽  
Mao Fang Huang
Keyword(s):  
Molecular Weight ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Gel Permeation Chromatography ◽  
Complex Viscosity ◽  
Low Protein ◽  
Nonlinear Viscoelastic ◽  
Gel Permeation ◽  
Linear Viscoelastic ◽  
The Relationship

Test of the rheology behavior for low protein natural rubber(LPNR) were carried out with rubber processing analyzer(RPA), and molecular weight were carried out with gel permeation chromatography(GPC). The results showed that molecular of LPNR is lower than natural rubber(NR), The complex viscosity(n*) of NR is higher than LPNR. The stress relaxation indicate that time of LPNR is faster than NR, it illuminate that LPNR has lower molecular weight than NR, and processing performance have distinct discrepancy between NR and LPNR. The torque(S’) with strain rising indicated that one linear viscoelastic region and one nonlinear viscoelastic region in whole range, and LPNR has lower S’ than NR.

Characterization of the aging behavior of raw epoxidized natural rubber with a rubber processing analyzer

2006 ◽  
Vol 100 (2) ◽  
pp. 1277-1281 ◽  
Author(s):  
Ping-Yue Wang ◽  
Hong-Lian Qian ◽  
Chun-Liang Yang ◽  
Ying-Chen
Keyword(s):  
Natural Rubber ◽  
Epoxidized Natural Rubber ◽  
Aging Behavior

Study on Rheological Characterization of Uncured Natural Rubber with Different Initial Moisture Contents Dried by Microwave

2014 ◽  
Vol 998-999 ◽  
pp. 383-386
Author(s):  
Fu Quan Zhang ◽  
Yong Zhou Wang ◽  
Mei Chen ◽  
Mao Fang Huang ◽  
Ri Zhong Zeng
Keyword(s):  
Natural Rubber ◽  
Viscoelastic Behavior ◽  
Sweep Frequency ◽  
Rheological Characterization ◽  
Moisture Contents ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Strain Sweep ◽  
Viscous Torque

In this work, the rheological behavior of uncured natural rubber with different initial moisture contents dried by microwave was studied using RPA under frequency sweep and strain sweep modes. It can be seen from the results that the variation trend of viscous torque S`` versus sweep frequency kept with the trend of elastic torque S` versus sweep frequency. Moreover, the viscous torque S`` values were lower than those for elastic torque S`, a good linear relation curve was obtained by plotting elastic torque S` versus sweep frequency. The curve of storage shear modulus G` versus sweep strain presented a linear relationship, showed a linear viscoelastic behavior of uncured natural rubber with different initial moisture contents. This may be explained by the degradation of molecular chains of natural rubber and the van der waals forces between them.

scholarly journals Effects of Long and Short Relaxation Times of Particle Interactions in Dense and Slow Granular Flows

2003 ◽  
Author(s):  
Duan Z. Zhang ◽  
Rick M. Rauenzahn
Keyword(s):  
Relaxation Time ◽  
Shear Rate ◽  
Stress Relaxation ◽  
Granular Medium ◽  
Volume Fraction ◽  
Particle Interaction ◽  
Interaction Networks ◽  
Particle Interactions ◽  
Particle Volume ◽  
Shear Rates

The rheological properties and the duration of particle interactions in a dense granular media are closely related to the formation of particle interaction networks. The behavior of particle interaction networks depends not only on the particle volume fractions but also on friction between particles. For examples, for frictionless particles, a particle interaction network may not form at particle volume fraction greater than 0.62, the random dense packing volume fraction for monodisperse spheres. Without network formation, particle interactions are short in time and mostly binary. Under this condition, the granular medium can be modeled as a viscous fluid with variable viscosity as in kinetic theory. Formation of particle interaction networks dramatically increases particle interaction time and results in a phase transition in the constitutive relations of the granular medium. Then, the stress relaxation time is inversely proportional to the macroscopic shear rate in simple shear flows, and the granular medium can be modeled as a viscoelastic material with a stress relaxation time depending on the macroscopic shear rate. For small shear rates, the stresses in the granular medium are independent of macroscopic shear rates in simple shear flows. Thus, as the shear rate approaches zero, the relaxation time approaches infinity, and the shear stress approaches a finite value, the yield stress, instead of zero. We also studied the relaxation behavior of the stress tensor under time-dependent shear rates. The dynamics of the particle interaction network leads to a nonlinear behavior of stress relaxation not exhibited by ordinary viscoelastic materials, such as polymeric fluids.

scholarly journals RHEOMETRIC AND DYNAMIC MECHANICAL ANALYSIS OF COMPLEX NATURAL RUBBER BASED COMPOSITES

2017 ◽  
Vol 37 (1) ◽  
Author(s):  
Aleksandra Ivanoska-Dacikj ◽  
Gordana Bogoeva-Gaceva ◽  
Sven Wießner ◽  
Gert Heinrich
Keyword(s):  
Natural Rubber ◽  
Dynamic Mechanical Analysis ◽  
Mechanical Analysis ◽  
Linear Strain ◽  
Dynamic Mechanical ◽  
Cluster Aggregation ◽  
Cure Time ◽  
Strain Sweep ◽  
Dominant Frequencies

This work describes the preparation and characterization of complex natural rubber (NR) based composites containing hybrid nano- and conventional fillers intended for base seismic application. Thorough rheometric and dy-namic mechanical analyses in strain sweep mode at 2 Hz and 10 Hz (two frequencies laying in the range 0 – 15 Hz in which most of the earthquakes have the dominant frequencies) were performed on complex natural rubber (NR) based composites containing hybrid nanofiller (carbon nanotubes, expanded montmorillonite) and different amounts of con-ventional fillers like carbon black (CB) and silica. The rheometric studies showed that the influence of the combina-tion of the different fillers on curing parameters is quite complex, but mainly the introduction of the fillers reduces the scorch and optimum cure time of the compounds. The dynamic mechanical analysis showed a pronounced non-linear strain dependence of the storage modulus and a remarkable increase of the loss factor tanδ for all composites, espe-cially for those containing high CB content, compared to the NR-gum. To describe this strain-dependency of the stor-age modulus the cluster-cluster aggregation (CCA) model was used. The values of the fitting parameters ΔE’0, γc, and E’∞ calculated by this model show that they are affected by the type of the fillers present in the NR matrix and also by the applied frequency.

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