Application of computed X-ray tomography scanning in the study of thermo-oxidative degradation of thick-walled filled natural rubber vulcanizates

1992 ◽  
Vol 44 (1) ◽  
pp. 83-94 ◽  
Author(s):  
H. Lavebratt ◽  
E. Östman ◽  
S. Persson ◽  
B. Stenberg
Keyword(s):  
Natural Rubber ◽  
Oxidative Degradation ◽  
X Ray ◽  
Natural Rubber Vulcanizates ◽  
Tomography Scanning ◽  
Thermo Oxidative Degradation

Thermo-Oxidative Degradation of Thick-Walled Rubber Materials Studied by IR-Technique and Computed X-Ray Tomography Scanning

1990 ◽  
Vol 63 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Bengt Mattson ◽  
Bengt Stenberg ◽  
Sture Persson ◽  
Erik Östman
Keyword(s):  
Oxidative Degradation ◽  
Attenuated Total Reflection ◽  
Low Permeability ◽  
Conventional System ◽  
X Ray ◽  
Oxidative Aging ◽  
Aging Properties ◽  
Thermal Stability Of ◽  
Tomography Scanning ◽  
Thermo Oxidative Degradation

Abstract Natural rubber cylinders vulcanized with two different systems, TMTD, which is an efficient vulcanizing system (EV system) and S/CBS, which is a conventional system, have been studied with respect to thermo-oxidative aging gradients, by the ATR-IR-technique (attenuated total-reflection infrared spectroscopy), computed x-ray tomography scanning and swelling. Observed aging processes are dominated by the formation of an oxidized layer whose low permeability to oxygen protects the interior of the material from oxidative aging processes as long as it is intact. The time to the formation of the oxidized layer is the major reason for the differences in the aging gradients. The oxidized layer is formed rapidly in the conventional system, whereas the formation is inhibited by dithiocarbamates in the EV system. Oxygen therefore diffuses into the EV materials, giving deeper oxidative aging than in the conventional materials at the same temperature. The conclusion drawn from the results of this study is that an earlier formation of an oxidized layer is advantageous with respect to thermo-oxidative aging of the bulk. Although it must be stated that, due to the better thermal stability of an EV system and to the poor mechanical properties of an oxidized layer, no objection is here raised to the accepted view that an EV system has superior aging properties.

KINETIC MODEL FOR THERMAL DEHYDROCHLORINATION OF CHLORINATED NATURAL RUBBER WITH DIFFERENT CHLORINE CONTENT

2014 ◽  
Vol 87 (2) ◽  
pp. 370-382
Author(s):  
Jing Chen ◽  
Lanzhen He ◽  
Yasheng Chen ◽  
Jieping Zhong ◽  
Canzhong He ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Oxidative Degradation ◽  
Storage Conditions ◽  
Chlorine Content ◽  
Heating Process ◽  
Lower Temperature ◽  
Novel Model ◽  
Derivative Thermogravimetry ◽  
Selection Of ◽  
Thermo Oxidative Degradation

ABSTRACT A novel model for calculating dehydrochlorination kinetics at a lower temperature of chlorinated natural rubber (CNR) is presented. It has been observed that dehydrochlorination is complex and involves three different stages. A model that accounts for dehydrochlorination at lower temperature is proposed. The kinetic parameters are obtained from dehydrochlorination experiments at 60–90 °C. The results of the kinetic calculation show that the apparent activation energy decreases with an increment of chlorine content. Higher chlorine content CNR makes it easier to remove hydrochloric acid when heated, but its dehydrochlorination rate affected by temperature is significantly less than that of the sample with a lower chlorine content. The thermogravimetric/derivative thermogravimetry results show that the beginning temperature of thermo-oxidative degradation rises with the increment of chlorine content. During the heating process, the higher chlorine content CNR is more stable than the lower one. The results suggest the storage conditions and basis for selection of appropriate temperature for the preparation of CNR from latex.

Influence of Crosslink Characteristics Induced by Aromatic-Based Antioxidants on the Swelling and Stress-Strain Behavior of Natural Rubber Vulcanizates

2003 ◽  
Vol 76 (2) ◽  
pp. 334-347 ◽  
Author(s):  
Tarek M. Madkour ◽  
Rasha A. Azzam
Keyword(s):  
Natural Rubber ◽  
Crosslinking Agent ◽  
Oxidative Degradation ◽  
Thermal Oxidative Degradation ◽  
Stress Strain ◽  
Strain Behavior ◽  
Strain Induced Crystallization ◽  
Elastomeric Chains ◽  
Natural Rubber Vulcanizates ◽  
Induced Crystallization

Abstract Stress-strain measurements were performed on dry and swollen natural rubber vulcanizates prepared using both sulfur as the crosslinking agent and aromatic-based bound antioxidants acting as a second crosslinking agent. The aromatic-based antioxidants were synthesized and analyzed spectroscopically in order to relate the final behavior of the vulcanizates to the nature of the crosslink characteristics. The anomalous upturn in the modulus values of these networks in response to the imposed stress was shown to persist in the dry as well as the swollen state. Since the swollen elastomeric chains cannot undergo a strain-induced crystallization, the abnormal upturns in the modulus values in an absence of a filler were explained on the basis of the limited extensibility of the short chains of networks prepared using two different crosslinking agents in line with earlier modeling predictions. Remarkably, the swelling experiments revealed the increase in the crosslink density of the networks in the early stages of the thermal oxidative degradation procedure indicating a post-cure of the chemically bound antioxidants to the elastomeric chains, which incidentally corresponds to a maximum in the modulus values of the networks. The rheological and other mechanical properties such as the hardness were shown not to have been affected as a result of the incorporation of the chemically bound antioxidants.

Effect of Types of Antioxidants on Thermal and Thermo-Oxidative Degradation of Epoxidized Natural Rubber

2014 ◽  
Vol 1004-1005 ◽  
pp. 245-248
Author(s):  
Chang Jin Yang ◽  
Yong Yue Luo ◽  
Bang Qian Chen ◽  
Kui Xu ◽  
Jie Ping Zhong ◽  
...  
Keyword(s):  
Thermogravimetric Analysis ◽  
Natural Rubber ◽  
Oxidative Degradation ◽  
Epoxidized Natural Rubber ◽  
Thermo Oxidative Degradation

Thermal and thermo-oxidative degradation of epoxidized natural rubber containing 25 mol % expoxidation (ENR25) with different four antioxidants were investigated by thermogravimetric analysis (TGA). The four antioxidants, viz., poly-2,2,4-trimethyl-1,2-dihydroqui- noline (RD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenedianine (4020), N-isopropyl-N'-phenyl- p-phenylenedi-amine (4010NA), and 2-mercaptobenzimidazole (MB) were used. The results indicate that the ENR25 vulcanizates with antioxidant 4020 or 4010NA is the optimal antioxidant for ENR25.

HXNBR Coating for Improving Aging Resistance of Natural Rubber Products

2006 ◽  
Vol 79 (4) ◽  
pp. 553-560 ◽  
Author(s):  
Rani Joseph
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Room Temperature ◽  
Oxidative Degradation ◽  
Thin Coating ◽  
Oil Resistance ◽  
Aging Resistance ◽  
Natural Rubber Vulcanizates ◽  
Good Heat ◽  
Accelerator System

Abstract HXNBR (Hydrogenated Carboxylated Nitrile Rubber) has very good heat ageing resistance and oil resistance. A novel accelerator system is designed to bring about the vulcanization of HXNBR at room temperature. The room temperature cured samples showed good mechanical properties equivalent to those of high (150 °C) temperature cured samples. Natural rubber vulcanizates are highly prone to oxidative and ozone degradation. The oil resistance of natural rubber vulcanizates is also very low. The oil resistance, ozone and oxidative degradation resistance of natural rubber vulcanizates are considerably improved by placing a thin coating of HXNBR over it.

The Degradation of Elastomers. 2. Oxidative Degradation of Natural Rubber Vulcanizates at Different Elongations and Temperatures. II

1959 ◽  
Vol 32 (3) ◽  
pp. 759-769 ◽  
Author(s):  
Karl-Heinz Hillmer ◽  
Walter Scheele
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Oxidative Degradation ◽  
Zero Order ◽  
Relaxation Rates ◽  
Good Qualitative Agreement ◽  
Kcal Mole ◽  
Pure Nitrogen ◽  
Natural Rubber Vulcanizates ◽  
Constant Activation Energy

Abstract The results of measurements of stress relaxation in natural rubber vulcanizates are reported. In the earlier work, the conditions were denned under which the drop in tension of a vulcanizate—after a pre-relaxation in pure nitrogen—follows a zero order law when tested in oxygen. The temperature dependence of the rate of relative tension relaxation was determined for 8 different vulcanizates. With a constant activation energy of about 29 kcal/mole, the vulcanizates differed in their relative relaxation rates at most by two powers of ten. Several general observations on the course of tension relaxation under different conditions were made on the grounds of experimental evidence. Good qualitative agreement was found with relations reported by Berry and Watson.

Accelerated liquefaction of vulcanized natural rubber by thermo-oxidative degradation

2021 ◽  
Author(s):  
Zhen Zhang ◽  
Yuxin Zhang ◽  
Jiayi Li ◽  
Adeel Ahmad Hassan ◽  
Shifeng Wang
Keyword(s):  
Natural Rubber ◽  
Oxidative Degradation ◽  
Thermo Oxidative Degradation
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