Crack Analysis of Unfilled Natural Rubber Using Infrared Microspectroscopy

1997 ◽  
Vol 70 (2) ◽  
pp. 271-282 ◽  
Author(s):  
Lori Neumeister ◽  
J. L. Koenig
Keyword(s):  
Molecular Structure ◽  
Natural Rubber ◽  
Bulk Material ◽  
Crack Tip ◽  
Resistant Material ◽  
Crack Analysis ◽  
Infrared Microspectroscopy ◽  
Orientation Effects ◽  
Transmission And Reflection

Abstract The characterization and analysis of the crack tip region of unfilled natural rubber is crucial in developing a fatigue resistant material. Therefore, the molecular structure and orientation of the material in the crack tip region has been compared to the bulk. Cracks formed by different methods were evaluated using both transmission and reflection techniques of infrared microspectroscopy. The material around the crack tip and crack edges shows much higher absorbances than the bulk material for stressed rubber. This is due to a higher concentration of material and residual orientation effects. For unstressed material the crack tip region exhibits identical characteristics to the bulk material.

Crack analysis of unfilled natural rubber using infrared microspectroscopy

1996 ◽  
Vol 54 ◽  
pp. 256-257
Author(s):  
L. A. Neumeister ◽  
J. L. Koenig
Keyword(s):  
Natural Rubber ◽  
Cross Section ◽  
Crack Tip ◽  
Molecular Structures ◽  
Attenuated Total Reflectance ◽  
Spectroscopic Methods ◽  
Total Reflectance ◽  
Infrared Microspectroscopy ◽  
Molecular Scale

Several spectroscopic methods are available for characterizing the crack tip region of natural rubber on the molecular scale to develop a material with fatigue resistant properties. Attenuated total reflectance or ATR-IR has been used to characterize the structure of many different polymers, including rubbers. Transmission has also been well established as a viable technique for the molecular characterization of transparent materials including thin films of unfilled natural rubber.Unfilled natural rubber was stretched to 629% elongation until cracks appeared in the surface. A cross section of the sample containing a crack was then microtomed at -85°C into slices approximately 0.5 µm thick. Similarly, samples were cut with a razor and microtomed under the same conditions. The crack tip region was mapped using the IRμs™/SIRM Molecular Microanalysis System. The map consisted often spectra taken in the x and y directions as shown in Figure 1. The same region was analyzed for orientation of molecular structures. Points were selected along the crack tip, crack edges, and the bulk. Dichroic ratios of all prominent peaks were calculated. ATR was used to verify the results of the mapping experiments for both stressed and unstressed material.

Modeling of Oxygen Diffusion Along Grain Boundaries in a Nickel-Based Superalloy

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
L. G. Zhao
Keyword(s):  
Finite Element ◽  
Oxygen Diffusion ◽  
Bulk Material ◽  
Hydrostatic Stress ◽  
High Stress ◽  
Great Influence ◽  
Crack Tip ◽  
Oxygen Diffusivity ◽  
Nickel Based Superalloy ◽  
Pressure Factor

Finite element analyses of oxygen diffusion at the grain level have been carried out for a polycrystalline nickel-based superalloy, aiming to quantify the oxidation damage under surface oxidation conditions at high temperature. Grain microstructures were considered explicitly in the finite element model where the grain boundary was taken as the primary path for oxygen diffusion. The model has been used to simulate natural diffusion of oxygen at temperatures between 650∘C and 800∘C, which are controlled by the parabolic oxidation rate and oxygen diffusivity. To study the effects of mechanical stress on oxygen diffusion, a sequentially coupled deformation-diffusion analysis was carried out for a generic specimen geometry under creep loading condition using a submodeling technique. The material constitutive behavior was described by a crystal plasticity model at the grain level and a unified viscoplasticity model at the global level, respectively. The stress-assisted oxygen diffusion was driven by the gradient of hydrostatic stress in terms of pressure factor. Heterogeneous deformation presented at the grain level imposes a great influence on oxygen diffusion at 750∘C and above, leading to further penetration of oxygen into the bulk material. Increased load level and temperature enhance oxygen concentration and penetration within the material. At 700∘C and below, mechanical loading seems to have negligible influence on the oxygen penetration because of the extremely low values of oxygen diffusivity and pressure factor. In the case of an existing surface microcrack, oxygen tends to accumulate around the crack tip due to the high stress level presented near the crack tip, leading to localized material embrittlement and promotion of rapid crack propagation.

Relaxation Processes in Vulcanized Rubber. II. Secondary Relaxation Due to Network Breakdown

1963 ◽  
Vol 36 (2) ◽  
pp. 389-398 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Molecular Structure ◽  
Experimental Study ◽  
Natural Rubber ◽  
Relaxation Process ◽  
Relaxation Processes ◽  
Secondary Relaxation ◽  
Oxidative Deterioration ◽  
Vulcanized Rubber ◽  
Oxidation Inhibitors ◽  
Natural Rubber Vulcanizates

Abstract An experimental study is described of a “secondary” relaxation process in stretched vulcanizates, which becomes dominant after long periods at normal temperatures. It is shown to be affected markedly by the temperature, the atmosphere in which the test is conducted, and the presence of oxidation inhibitors. It is therefore attributed to oxidative deterioration of the molecular structure. In some vulcanizates, however, a similar or even greater relaxation is found to occur in vacuo, and this is attributed to the failure of specific crosslink structures. The extent of recovery on releasing the extended testpieces has also been investigated for a number of natural rubber vulcanizates.

Rheological Behavior Characterization of Natural Rubber Containing Different Gel

2014 ◽  
Vol 970 ◽  
pp. 320-323 ◽  
Author(s):  
Saengchao Thongseenuch ◽  
Wirach Taweepreda ◽  
Krisda Suchiva
Keyword(s):  
Molecular Structure ◽  
Natural Rubber ◽  
Rheological Behavior ◽  
Loss Modulus ◽  
Natural Rubber Latex ◽  
Gel Structure ◽  
Gel Content ◽  
Molecular Weights ◽  
Branching Points

This research, natural rubber containing different gel contents were prepared by deproteinization and saponification treatment from high ammonium natural rubber latex. Deproteinization natural rubber was further treated as acetone extraction and then transesterification. It was founded that gel content and molecular weights of treated natural rubber were decreased and almost absented for transesterification treatment. Rheological respond on small amplitude oscillating shear (SAOS) and large amplitude oscillating shear (LAOS) deformation of treated natural rubber were captured by using rubber process analyzer (RPA 2000). Firs harmonic rheological properties, storage modulus, G and loss modulus, G decreased as gel content and molecular weight decreased. It was believed that gels, explicitly branching points, were destroyed after the natural rubber was deproteinized, transesterification, or saponification according to the molecular structure of natural rubber presumed by Tanaka et al, which functional groups contain protein and fatty acid are participated in branching to forming gel structure. It was concluded that gel content as the same as molecular structure of natural rubber could be characterized as rheological behavior.

scholarly journals Microstructure and Lamellae Phase of Raw Natural Rubber via Spontaneous Coagulation Assisted by Sugars

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4306
Author(s):  
Wanna Bai ◽  
Jie Guan ◽  
Huan Liu ◽  
Shihong Cheng ◽  
Fuchun Zhao ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Biological Activity ◽  
Natural Rubber ◽  
Excellent Performance ◽  
Brown Sugar ◽  
Degree Of Crystallization ◽  
Traditional Process ◽  
Acid Coagulation ◽  
Environmental Challenge

Natural rubber (NR) as a renewable biopolymer is often produced by acid coagulation of fresh natural latex collected from Hevea brasiliensis. However, this traditional process is facing a huge economic and environmental challenge. Compared with the acid coagulation, spontaneous or microorganism coagulation is an ecofriendly way to obtain NR with excellent performance. To clarify the influence of different sugars on NR quality, several sugars were used to assist the coagulation process. Influence of different sugars on microstructure and cold crystallization were examined by 1H NMR, DSC, etc. The results indicated that sugars exhibit different biological activity on terminal components of fresh field latex and can influence the resultant molecular structure and basic properties. Brown sugar exhibits higher metabolic activity and is inclined to decompose the protein and phospholipids crosslinking compared with other sugars. The larger molecular weight of sugar molecule is beneficial for the formation of the stable α lamellae phase and higher overall degree of crystallization.

X-Ray Analysis of the Molecular Structure of Rubbers. X-Ray Diffraction of Amorphous Rubber

1952 ◽  
Vol 25 (2) ◽  
pp. 258-264 ◽  
Author(s):  
V. I. Kasatochkin ◽  
B. V. Lukin
Keyword(s):  
Molecular Structure ◽  
Natural Rubber ◽  
Crystalline Phase ◽  
X Ray Diffraction ◽  
Amorphous Halo ◽  
Crystallization Property ◽  
X Ray ◽  
Synthetic Rubber ◽  
Continuous Background ◽  
Diffraction Patterns

Abstract The potentialities of x-ray analysis of the molecular structure of rubbers can be widely extended by measuring the intensities of the amorphous halo and continuous background of scattering in the diffraction patterns of unstretched test-specimens. This method can be applied to the study of the effect of repeated stretching of rubbers. Questions pertaining to the fatigue of rubbers have immense importance now in the performance of rubber products. The methods of determining the crystallization of natural rubber and of measuring the intensity of the amorphous halo for synthetic rubber were employed for investigating the changes of the molecular structure of rubber due to repeated stretching. The crystallization of raw smoked-sheet rubber decreased as a result of fatigue; a similar phenomenon was observed for its vulcanizates. The vulcanizates which were stretched less than 300 per cent lost their crystallization property altogether after fatigue, and, at greater elongations, the content of the crystalline phase greatly decreased (see Figure 1).

Sign in / Sign up

Export Citation Format

Share Document