Effect of Viscosity Stabilizer on the Properties and Structure of Raw Constant Viscosity Rubber

2012 ◽  
Vol 557-559 ◽  
pp. 947-951
Author(s):  
Yong Zhou Wang ◽  
Ping Yue Wang ◽  
Bei Long Zhang ◽  
Hong Hai Huang ◽  
Li Ding ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Low Frequency ◽  
Hydroxylamine Hydrochloride ◽  
Dynamic Mechanical Properties ◽  
Linear Viscoelastic ◽  
Strain Sweep ◽  
Constant Viscosity

The properties of raw constant viscosity natural rubber were measured using a rubber processing analyzer. The results show that the rubber processing analyzer can characterize well the effect of viscosity stabilizer on the dynamic mechanical properties of raw constant viscosity rubber by applied strain sweep or frequency sweep. In linear viscoelastic region, the increment of the dynamic torque S’ of the constant viscosity natural rubber prepared with hydroxylamine hydrochloride decreases with the increase in the level of hydroxylamine hydrochloride . In the range of low frequency, the increment of the dynamic modulus G’ of constant viscosity natural rubber prepared with hydroxylamine hydrochloride is obvious lower than those of natural rubber and constant viscosity natural rubber prepared with aniline. G’ of the constant viscosity natural rubber prepared with aniline is just only a little higher than that of natural rubber. Hydroxylamine hydrochloride and aniline can decrease the molecular weight of rubber, and change the molecular weight distribution. The dynamical properties of constant viscosity natural rubber are dependent on the molecular weight and the molecular weight distribution.

Long-Chain Branching and Mechanism Controlling Molecular Weight in Hevea Rubber

1999 ◽  
Vol 72 (4) ◽  
pp. 712-720 ◽  
Author(s):  
Jitladda Tangpakdee Sakdapipanich ◽  
Tippawan Kowitteerawut ◽  
Krisda Suchiva ◽  
Yasuyuki Tanaka
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Branch Points ◽  
Long Chain Branching ◽  
Linear Character ◽  
Close Relationship ◽  
Deproteinized Natural Rubber ◽  
Long Chain

Abstract The linear character of transesterified deproteinized natural rubber (DPNR-TE) was confirmed by the analysis of terminal groups with NMR and viscometric analyses. The branch content of DPNR rubber from fresh latex was found to range from 0.3 to 1.3 and 0.7 to 3.2, based on tri- and tetra-functionalities, respectively. The plot between the number of branch-points and molecular weight (MW) can be divided into three fractions: (A) the rubber fractions in MW ranging from 2.4×105 to 1.9×106; (B) between 1.9×105 and 2.4×105; and (C) those of MW less than 1.9×105. The fraction (A) showed the number of branch-points per a branched molecule (m) higher than that of fractions (B) and (C). This plot is superimposable with the bimodal molecular-weight distribution (MWD) of Hevea rubber, showing a good coinciding of peak-tops at the high and low MW fractions. It seems likely that there is a close relationship between the number of branch-point and bimodal MWD of natural rubber.

Viscoelastic Characterization of Long Branching and Gel in Butadiene-Acrylonitrile Copolymer Elastomers

1980 ◽  
Vol 53 (1) ◽  
pp. 14-26 ◽  
Author(s):  
N. Nakajima ◽  
E. R. Harrell
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
General Rule ◽  
The Other ◽  
Model Systems ◽  
Newtonian Flow ◽  
Long Chain Branching ◽  
Linear Viscoelastic ◽  
Definition Of

Abstract Difficulties in relating long-chain branching to processability may be attributable to two causes: one is the definition, pertinent to processability, of what long branches are and the other is a method of determining long branching which is free from interference by other material variables, such as molecular weight distribution, gel, and “short” branches. Measurements of the dilute solution properties are tedious, time-consuming, and require skill for precision. In addition, the requirement for filtering the solution practically obliterates the result, regardless of how precise the measurement may be, because elastomers, as a general rule, have or are suspected to have an insoluble gel fraction. Recent advances in viscoelastic studies of model polymers show that the branches must be 2–3 times longer than the “entanglement coupling” distance in order to exhibit enhancement of viscosity in the Newtonian flow. Whereas Newtonian flow provides a precise definition of the long branches, it is not accessible for most of the elastomers. In the observed time scale, the linear viscoelastic properties as well as the steady-state viscosities are affected not only by branches but also by gels and molecular weight distribution. When these material variables are changed one at a time in the properly designed model systems, their effects are separately observable. On the other hand with a sample of unknown background, the effect of long branching is usually inseparable from those of other variables.

The Structure of Neoprene. I. The Molecular-Weight Distribution of Neoprene Type GN

1949 ◽  
Vol 22 (3) ◽  
pp. 680-689
Author(s):  
W. E. Mochel ◽  
J. B. Nichols ◽  
C. J. Mighton
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Osmotic Pressure ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Distribution Curve ◽  
Pressure Measurements ◽  
Dilute Solution ◽  
Molecular Weights ◽  
Good Agreement

Abstract Polychloroprene rubber (Neoprene Type GN) was fractionated by partial precipitation from dilute solution in benzene and the fractions were examined both osmotically and viscometrically in benzene solutions. The molecular-weight distribution curve for Neoprene Type GN based on osmotic pressure measurements shows a pronounced maximum at 100,000, but has a long extension to molecular weights of over one million, indicating the presence of branched or cross-linked material which is still soluble. The uniformity is somewhat less than that of sol natural rubber, while in shape the Neoprene distribution curve resembles more closely that of peptized natural rubber than fresh sol rubber. Observed variations in the slopes of the π/c vs. c and the ηsp/c vs. c curves also indicate the presence in solution of complex, branched and (or) cross-linked molecules. Calibration of the intrinsic viscosity-molecular weight relationship by osmotic pressure measurements gave good agreement with the equation: [η]=KMa, where K=1.46×10−4 and a=0.73.

Effect of Microwave Drying on Structure and Properties of Natural Rubber

2012 ◽  
Vol 538-541 ◽  
pp. 2409-2412 ◽  
Author(s):  
Mei Chen ◽  
Fu Quan Zhang ◽  
Yong Zhou Wang ◽  
Mao Fang Huang
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Morphological Structure ◽  
Microwave Drying ◽  
Structure And Properties ◽  
Hot Air ◽  
Oxidative Resistance

The morphological structure and properties of wet natural rubber (NR) granulates dried by microwave were studied, which compared with wet NR granulates dried by hot-air. The results show that the molecular weight of NR dried by microwave is higher than that of NR dried by hot-air, and the molecular weight distribution of NR dried by microwave is narrower than that of NR dried by hot-air. The wet NR granules dried by microwave are rough on surfaces and the cutting traces produced during the processing remained on surfaces; whereas the wet NR granules dried by hot-air are smooth on surfaces resulted from melt adhered, and the cutting traces disappeared; the thermal-oxidative resistance of NR vulcanizates dried by microwave improved significantly.

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