The glass transition temperature of natural rubber

1985 ◽  
Vol 30 (4) ◽  
pp. 929-941 ◽  
Author(s):  
M. J. R. Loadman
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Natural Rubber

Elastomer Structures and ‘Cold Crystallization’

1979 ◽  
Vol 52 (1) ◽  
pp. 207-212 ◽  
Author(s):  
M. Bruzzone ◽  
E. Sorta
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Natural Rubber ◽  
Crystallization Rate ◽  
Cold Crystallization ◽  
Structural Defects ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Abstract In a great number of applications an ideal elastomer should satisfy, to a certain extent, both of the following requirements: (1) nearly instantaneous crystallization upon application of strain (strain induced crystallization) and (2) slow or no crystallization when cooled at the temperature of maximum crystallization rate (cold induced crystallization). A noteworthy case of (2) is elastomer crystallization in a strained state. The connection between the points (1) and (2) has not been clearly understood up to now, but it is known that some crystallizable elastomers fulfil the requirements of both (1) and (2) better than others. From an experimental point of view, cold induced crystallization kinetics are substantially easier to measure than those of very fast strain induced crystallization. The phenomenon of cold induced crystallization in natural rubber, NR, has been known since the very beginning of elastomer technology and the tendency of natural rubber to crystallize by cooling has been overcome by crosslinking it with sulphur (vulcanization) without impairing its ability to crystallize by stretching (Goodyear, 1836). The synthesis of cis-polyisoprenes (IR) and cis-polybutadiene (BR) of different microstructural purity (different cis content) gave the possibility of changing the crystallization rate. It has also been reported that the very fast cold crystallization of trans-polypentenamer (TPA) could be reduced by lowering the trans content. The same fact had been observed earlier for trans-polychloroprene. There is a general agreement in postulating that the reduction of the crystallization rate, obtained either by cross-linking or by chain regularity reduction, can be linked with the lowering of the melting point. In both cases the low level of structural defects introduced in the chains does not affect the glass transition temperature in such a way as to vary the crystallization rate. The aim of this paper is to emphasize the importance of the variations of the glass transition temperature and melting point on the elastomeric cold crystallization rate and the way these may be used in planning new elastomer structures.

Formation and Evolution of Chemical-Physical Complex Network during Vulcanization in Carbon Black Filled Natural Rubber (NR)

2016 ◽  
Vol 717 ◽  
pp. 27-31
Author(s):  
Guang Shui Yu ◽  
Ji Wen Liu ◽  
Jun Mei Cheng ◽  
Chong Sun
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Carbon Black ◽  
Natural Rubber ◽  
Complex Network ◽  
Cross Linking ◽  
Weight Percentage ◽  
Critical Content ◽  
Formation And Evolution

The formation and evolution of chemical-physical complex network during vulcanization in carbon black (CB) filled NR was investigated in this work. The results showed that the cross-linking density increased with increase of CB content. The variation of torque during vulcanization was attributed to crosslinks of macromolecular chains. The critical content of CB for the forming of CB network was between 30phr and 40phr (weight percentage). The CB content did not affect the glass transition temperature (Tg) obviously.

scholarly journals Glass Transition Temperature and Microhardness of Compatible and Incompatible Elastomer/Plastomer Blends

1970 ◽  
Vol 33 (1) ◽  
pp. 15-24 ◽  
Author(s):  
MF Mina ◽  
GH Michler ◽  
FJ Balta Calleja
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Natural Rubber ◽  
Methyl Methacrylate ◽  
Core Shell ◽  
Scanning Calorimetry ◽  
Rubber Toughened ◽  
Shell Particles

Glass transition temperature (Tg) of core-shell particles-toughened poly(methyl- methacrylate) (CSPTPMMA) and natural rubber-toughened PMMA (NRTPMMA), which are basically the PMMA/elastomer blends with different concentrations of elastomer heterogeneously distributed in the samples, was investigated by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and microindentation technique (MT). Microhardness (H) of the samples was measured using MT. Core-shell particles (CSP) with a rubbery shell and natural rubber (NR) were used as reinforcing materials for the production of compatible and incompatible blends, respectively. Results reveal a good correlation of the glass transition temperature (Tg) obtained from DSC and DMA, and that deduced from MT.  The H-value of each sample is compared with its Tg-value. Increase of Tg with the increase of H, which is a general behavior of polymers, is not maintained in the both blends investigated. Contrary to expectation, H is shown to decrease with increasing glass transition temperature in case of CSP-toughened compatible blends while it decreases with the decrease of Tg-value only in case of NR-modified incompatible blends for lower NR concentration (<1 wt%) and does not depend on Tg for rubber content higher than 1 wt%.  Keywords: Glass transition temperature, microhardness, rubber-toughened poly(methyl -methacrylate), core-shell particle, differential scanning calorimetry DOI: 10.3329/jbas.v33i1.2946 Journal of Bangladesh Academy of Sciences, Vol. 33, No. 1, 15-24, 2009

Studies of Rubber Abrasion

1979 ◽  
Vol 52 (5) ◽  
pp. 1008-1018 ◽  
Author(s):  
E. Southern ◽  
A. G. Thomas
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Natural Rubber ◽  
Crack Growth ◽  
General Model ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Abrasion Rate ◽  
Rate Of Movement

Abstract The general model proposed, which assumes that crack growth plays an important part in the abrasion process when abrasion patterns are produced, is supported by evidence from the behavior of noncrystallizing rubbers. In particular, the rate of movement of the pattern across the surface is closely related to the crack growth behavior. Natural rubber behaves under abrasion conditions as if it were prevented from exhibiting its usual crystallization-enhanced strength. An important factor determining the abrasion rate, in addition to the crack growth behavior, is the angle at which the hypothetical cracks at the pattern base grow. What determines this angle is not yet clear, but it appears to be closely related to the geometry of the pattern, and it seems likely, from a study of this geometry, that much of the loss of rubber occurs from the steeply raked face of the pattern. The pattern spacing, as well as depending on the abrading force, also appears to be influenced by the test temperature and the glass transition temperature of the rubber, suggesting that viscoelastic considerations are important.

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