Determination of Degree of Crosslinking in Natural Rubber Vulcanizates. Part V. Effect of Network Flaws Due to Free Chain Ends

1961 ◽  
Vol 34 (1) ◽  
pp. 301-308
Author(s):  
L. Mullins ◽  
A. G. Thomas
Keyword(s):  
Natural Rubber ◽  
Natural Rubber Vulcanizates

Structural Characterization of Filled Vulcanizates Part 1. Determination of the Concentration of Chemical Crosslinks in Natural Rubber Vulcanizates Containing High Abrasion Furnace Black

1967 ◽  
Vol 40 (3) ◽  
pp. 866-882 ◽  
Author(s):  
M. Porter
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Volume Fraction ◽  
Exponential Relationship ◽  
Furnace Black ◽  
Simple Linear Relationship ◽  
Chemical Crosslinks ◽  
Natural Rubber Vulcanizates

Abstract The degree to which HAF black restricts the swelling of natural rubber vulcanizates in n-decane has been determined using a vulcanizing system in which the stoichiometry of crosslinking is unaffected by the carbon black. The dependence of the degree of restriction, as measured by the ratio of the volume fractions of rubber in the filled and unfilled vulcanizates swollen to equilibrium, on the concentration of carbon black follows an exponential relationship previously proposed by Lorenz and Parks. This is found to be equivalent to a simple linear relationship between the apparent and actual crosslink concentrations: napparent/nactual=1+Kϕ, where K is a constant characteristic of the filler and φ is its volume fraction in the vulcanizate. The relation has been used to determine actual crosslink concentrations in filled natural rubber vulcanizates. HAF black is found to cause increases of up to 25 per cent in the yield of polymer to polymer crosslinks in conventional sulfur vulcanizing systems, accompanied by changes in rate of cure and of crosslink reversion. All these are small compared with the effect of the filler on many physical properties.

Determination of Degree of Crosslinking in Natural Rubber Vulcanizates. Part I

1957 ◽  
Vol 30 (1) ◽  
pp. 1-10 ◽  
Author(s):  
L. Mullins
Keyword(s):  
Natural Rubber ◽  
Empirical Relationship ◽  
Interaction Constant ◽  
Empirical Correction ◽  
Equilibrium Volume ◽  
Self Consistent ◽  
Volume Swelling ◽  
Natural Rubber Vulcanizates ◽  
The Relationship

Abstract This paper examines the relationship between the stress-strain properties of highly swollen natural rubber vulcanizates and their equilibrium volume swelling. It is shown that the empirical relationship obtained can be described equally well by either the Flory-Huggins equation or the Flory Modification of this equation, and values of the interaction constant µ for natural rubber in decane are determined. Observed differences in the values of µ obtained for sulfur and peroxide vulcanizates are interpreted in terms of the diluent effect of nonrubber constituents in the former. The effect of the initial molecular weight of the unmasticated rubber on these physical properties is examined and an empirical correction making allowance for chain segments terminated by a crosslink at only one end is obtained. The correction is larger than that derived by previous workers and possible sources of the observed differences are discussed. It is considered that internally self-consistent estimates of the degree of crosslinking of natural rubber vulcanizates may be obtained using the methods developed.

PREPARATION AND CHARACTERIZATION OF BROMINATED NATURAL RUBBER APPLIED IN SILICA-FILLED NATURAL RUBBER VULCANIZATES

2016 ◽  
Vol 89 (3) ◽  
pp. 406-418 ◽  
Author(s):  
Nuchanart Onchoy ◽  
Pranee Phinyocheep
Keyword(s):  
Natural Rubber ◽  
Bromine Atom ◽  
Proton Nuclear Magnetic Resonance ◽  
Strong Emission ◽  
X Ray ◽  
Rubber Compounds ◽  
Silica Filler ◽  
Natural Rubber Vulcanizates

ABSTRACT Functionalization of NR with a bromine atom was developed and explored for its application in a silica-reinforced NR system. Two possible pathways were investigated: the direct addition of a bromine atom using N-bromosuccinimide (NBS) with FeCl2 as a catalyst in the latex phase (NR–Br); and an indirect method using a ring opening of epoxidized natural rubber (ENR) with 2-bromopropionic acid (ENR–Br). The chemical structure, including determination of the bromine contents, was analyzed with proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. The occurrence of bromine in NR–Br was confirmed using scanning electron microscopy with energy dispersive x-ray spectroscopy. Strong emission peaks for Br Kα at 1.5 eV was evidenced. Moreover, glass transition temperature of modified NRs increased after bromination. Two types of brominated NR, that is, NR–Br and ENR–Br containing 2 and 4 mol% of bromine function, respectively, were used in a range of 1–5 phr in the silica-reinforced NR system with silica loading of 10 and 30 phr. Both cure and mechanical properties of the rubber compounds were investigated. The incorporation of the bromine function in NR of both ENR–Br and NR–Br enhanced the cure reactivity of the NR–silica vulcanization system. The modified NRs may have a role as a coupling agent between the NR and the silica filler.

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