scholarly journals Molecular Structure of Natural Rubber and Its Characteristics Based on Recent Evidence

10.5772/29820 ◽  
2012 ◽  
Author(s):  
Jitladda T. ◽  
Porntip Rojruthai
Keyword(s):  
Molecular Structure ◽  
Natural Rubber

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).

Crystallization of Cis-Polyisoprenes in a Capillary Rheometer. II. The Effects of Experimental Parameters and Molecular Structure

1971 ◽  
Vol 44 (1) ◽  
pp. 12-28 ◽  
Author(s):  
V. L. Folt
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Natural Rubber ◽  
Crystallization Process ◽  
Complex Function ◽  
Capillary Rheometer ◽  
Optimum Conditions ◽  
Experimental Parameters ◽  
Static Conditions

Abstract Cis-polyisoprenes are readily crystallized under the pressure and orientation forces existing in a capillary rheometer. The ease at which crystallization can be effected is a complex function of the interrelationships existing among the temperature, the molecular weight, stereoregularity, and the dimensions of the capillary. For a given cis-polyisoprene and capillary, crystallization occurs more readily as the molecular weight is increased. Decreasing the diameter of the capillary and/or increasing the length of the capillary enhances the ease at which a given cis-polyisoprene can be crystallized. Using the optimum conditions presently available, natural rubber has been crystallized at 146° C. The ease at which crystallization is effected decreases drastically as the cis-1,4 content of the polyisoprene is reduced. Trans-1,4 and 3,4 are similarly effective in retarding the crystallization process and their effects are proportional to their concentrations in the molecular chains. However, polyisoprenes which will not crystallize under static conditions at −20° C are readily crystallized in the capillary rheometer at much higher temperatures.

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.

Permeability of Elastic Polymers to Hydrogen

1941 ◽  
Vol 14 (2) ◽  
pp. 444-448
Author(s):  
Theron P. Sager
Keyword(s):  
Molecular Structure ◽  
Natural Rubber ◽  
Activation Energies ◽  
Energy Requirements ◽  
Synthetic Materials ◽  
Lower Permeability ◽  
Increasing Temperature

Abstract The permeabilities to hydrogen of natural rubber, Perbunan, Neoprene G, Vistanex, Thiokol DX, and Pliofilm diminished in the order mentioned. The increase in rate of permeation with increasing temperature was exponential in all cases. Values for the activation energies or permeability for hydrogen were found to be 6,800 calories per mole for natural rubber and 8,400 to 9,500 calories per mole for the synthetic materials. The greater magnitude of the energy requirements of the latter indicates that their lower permeability may be attributed to differences in their molecular structure.

Molecular Structure and Properties of Polybutadiene Rubbers

1964 ◽  
Vol 37 (2) ◽  
pp. 408-433 ◽  
Author(s):  
H. Blümel
Keyword(s):  
Molecular Structure ◽  
Natural Rubber ◽  
Structural Characteristics ◽  
Molecular Structures ◽  
Structure And Properties ◽  
Technological Properties ◽  
Starting Point ◽  
Mixing Behavior ◽  
Basic Characteristics ◽  
The One

Abstract A discussion of the development, present day applications, and the advantages of polybutadienes are presented. The variations of an over-all concept in products obtained through different preparations and having various molecular structures as well as differing service and technological properties were made the starting point for the present investigations. Section 2 provides a review of the basic characteristics of the most important processes for preparing polybutadiene and the associated structural or compositional characteristics. Fourteen typical polybutadienes encompassing the entire range of polybutadienes are compared to cold rubber and natural rubber with respect to their most importance analytical and polymer values corresponding to their arrangement into preparation groups. The correlations between the technological properties of the raw rubbers, of the compounds, including the mixing behavior, and the vulcanizates on the one hand and the molecular structure composition of the rubbers upon which they are based, on the other, are discussed using detailed synopses in Sections 3 and 4. In doing this, it was important to see the principal features of the different polybutadienes compared to one another, effects of the structural characteristics and of additives on the properties of the raw rubbers, compounds, and vulcanizates, as well as the differences encountered as compared to polymers which are considered most important for use in blends (cold SBR and natural rubber). Finally, in Section 5, in summary form, the effects were treated of the individually appearing structural and compositional factors in the initial polymers on the service and technological properties of the raw rubbers, compounds, and vulcanizates.

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