Ultrasonic Devulcanization of Precipitated Silica-Filled Silicone Rubber

2001 ◽  
Vol 74 (2) ◽  
pp. 303-316 ◽  
Author(s):  
Sang E. Shim ◽  
A. I. Isayev
Keyword(s):  
Mechanical Properties ◽  
Silicone Rubber ◽  
Crosslink Density ◽  
Performance Characteristics ◽  
Processing Conditions ◽  
Precipitated Silica ◽  
Filled Rubber ◽  
Filled Rubbers ◽  
Silicone Rubbers ◽  
Considerable Enhancement

Abstract This investigation involves the recycling of precipitated silica-filled silicone rubber using a continuous ultrasonic reactor. The processing conditions utilized in devulcanization of the filled systems were similar to those in our previous work on unfilled systems. Significant differences were observed in devulcanization of unfilled and filled systems. A decrease in gel fraction and crosslink density was sufficient for devulcanized silica-filled silicone rubber to be reprocessed and revulcanized. The cure behavior of silicone rubber and the mechanical properties of virgin, and revulcanized rubber were measured. Results showed that unfilled silicone rubbers gave no change in vulcanizate mechanical properties after revulcanization. However, in the filled rubbers there was a decrease in the mechanical properties of revulcanizates. In order to achieve an improvement in the properties, devulcanized filled rubbers were blended with virgin filled rubber in various proportions. The obtained results indicated a considerable enhancement of the performance characteristics of these blend vulcanizates.

Network Scission Processes in Peroxide Cured Methylvinyl Silicone Rubber

1967 ◽  
Vol 40 (2) ◽  
pp. 629-634
Author(s):  
D. K. Thomas
Keyword(s):  
Silicone Rubber ◽  
Elevated Temperatures ◽  
Main Chain ◽  
Methyl Groups ◽  
Chain Polymer ◽  
Filled Rubber ◽  
Oxidative Reactions ◽  
Silica Filler ◽  
Silicone Rubbers ◽  
Hydrolysis Of

Abstract In what appeared to be a complex system it transpires that network scission in methylvinyl silicone rubbers at temperatures below 250° C is due largely to hydrolytic reactions in the main chain polymer. At temperatures of 250° C and above there are indications that a significant amount of scission arises from oxidative reactions in the crosslinks, and that this reaction is catalyzed by acidic residues in the rubber. There is no indication that acidic byproducts of the vulcanization reaction catalyze the hydrolysis of siloxane bonds in the polymer. In conventional heat aging tests in which the rubber remains in an unstrained condition the effects of hydrolysis will only be observed if the concentration of water in the system is allowed to rise. Under these circumstances softening will occur because of a shift in the position of equilibrium in the reaction ∼Si—O—Si—O∼ + H2O→∼Si—OH+ HO—Si—O∼ On aging the material in a well ventilated situation the effects of hydrolysis are not seen and the silicone rubber becomes brittle after long exposure at high temperature. This embrittlement must result from additional crosslinking caused by oxidative reactions in the methyl groups of the main chain polymer. When the rubber is used in compression or tension, hydrolytic scission will affect performance, and in applications of this sort it is important to dry the rubber before use and prevent access of moisture to the component during use. With filled rubber the silica filler is a further source of moisture and drying needs to be carried out at elevated temperatures immediately before use. In order to improve the confined heat aging performance of silicone rubber an alternative filler to fine silica is needed which does not have the same affinity for water. It may be, however, that ability to reinforce silicone rubber and affinity for water are inseparable.

Superior Mechanical Properties of Ultrasonically Recycled EPDM Rubber

2003 ◽  
Vol 76 (1) ◽  
pp. 253-270 ◽  
Author(s):  
Jushik Yun ◽  
A. I. Isayev
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Power Consumption ◽  
Crosslink Density ◽  
Dynamic Properties ◽  
Extensive Study ◽  
Processing Conditions ◽  
Elongation At Break ◽  
Epdm Rubber ◽  
Superior Mechanical Properties

Abstract This paper describes the results of an extensive study involving the continuous ultrasonic devulcanization of unfilled EPDM rubber. Die pressure and ultrasound power consumption were measured as a function of processing conditions. The mechanical properties of aged and fresh revulcanized EPDM rubber were measured. Gel fraction, crosslink density, and dynamic properties were also determined for the virgin vulcanizate, the ultrasonically devulcanized rubber, and the revulcanized rubber. Additionally, the cure behavior of virgin and devulcanized EPDM rubber was investigated. The tensile strength of revulcanized EPDM rubber was found to be much higher than that of the virgin vulcanizate with the elongation at break being practically intact. A mechanism explaining the increase in mechanical properties of revulcanized rubbers was proposed.

Silica Properties/Rubber Performance Correlation. Carbon Black-Filled Rubber Compounds

1994 ◽  
Vol 67 (2) ◽  
pp. 217-236 ◽  
Author(s):  
Timothy A. Okel ◽  
Walter H. Waddell
Keyword(s):  
Carbon Black ◽  
Physical Properties ◽  
Surface Area ◽  
Performance Characteristics ◽  
Rubber Compound ◽  
The Road ◽  
Precipitated Silica ◽  
Filled Rubber ◽  
Rubber Compounds ◽  
As Stress

Abstract The effectiveness of predicting rubber performance based on measured silica physical properties in silica- and carbon black-filled compounds is presented for three rubber formulations: an off-the-road tire tread, a wire coat stock and a V-belt. Correlation and regression analyses were performed using SAS software for sixteen physical properties of thirteen precipitated silicas, and sixteen rubber compound performance characteristics of the three compounds. Silica physical properties studied include various measurements of surface area and structure, particle size, pH and impurities. Rubber performance characteristics studied include cure properties and physical properties such as stress/strain, tear strength, cut growth resistance, abrasion resistance and heat build-up. The present study confirms that silica surface area is the single best predictor of the effect that varying silica physical properties have on the physical performance of cured, carbon black-filled rubber compounds containing precipitated silica. Silica structure, as measured by DBP absorption and nitrogen or mercury pore volume, is a secondary predictor of certain rubber physical properties. The confidence limits of the predictions is dependent upon the concentration of precipitated silica used in the carbon black-filled rubber compound.

Superior Mechanical Properties of Reclaimed SBR with Bimodal Network

1997 ◽  
Vol 70 (2) ◽  
pp. 194-201 ◽  
Author(s):  
A. I. Isayev ◽  
S. H. Kim ◽  
V. Yu Levin
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Crosslink Density ◽  
Processing Conditions ◽  
Elongation At Break ◽  
Gel Fraction ◽  
Superior Mechanical Properties

Abstract The correlation between the mechanical properties of revulcanized SBR, total and polysulfidic crosslink density, gel fraction of original vulcanizate, ultrasonically devulcanized, and revulcanized rubber is described. Under some processing conditions the tensile strength of revulcanized SBR is found to be much higher than that of the original vulcanizate with elongation at break being practically intact. A model explaining the increase in mechanical properties of revulcanized rubber is proposed.

Dynamic Mechanical Properties of Precipitated Silica Filled Rubber: Influence of Morphology and Coupling Agent

2003 ◽  
Vol 76 (1) ◽  
pp. 145-159 ◽  
Author(s):  
Laurence Ladouce-Stelandre ◽  
Yves Bomal ◽  
Lionel Flandin ◽  
Dominique Labarre
Keyword(s):  
Mechanical Properties ◽  
Dynamic Mechanical Properties ◽  
Mathematical Treatment ◽  
Interface Agents ◽  
Payne Effect ◽  
Dynamic Mechanical ◽  
Precipitated Silica ◽  
Vulcanized Rubber ◽  
Filled Rubber ◽  
Help Giving

Abstract Composites that incorporate precipitated silica into a vulcanized rubber were investigated for dynamic mechanical properties. Comparing different types of filler, it was found that the mean distance between particles did not alter Payne effect. On the contrary, the amount and morphology of the fillers played a major role on the macroscopic properties. The nature and amount of coupling or covering agents was also found to be an important parameter. A direct relationship between length and efficiency of interface agents was evidenced: longer silanes were more effective than shorter once independently from a covalent bounding to rubber. The set of studied parameters affecting Payne effect can be reduced to only two independents variables: the total amount of silica-rubber interface (a function of the amount of filler and its BET surface) and the quantity and nature of interface agent. From these data an attempt to relate the rubber to filler cohesion to Payne effect is proposed as well as a molecular mechanism derived from Maier and Göritz model. A mathematical treatment of the proposed mechanisms is currently being investigated that might help giving further insights on novel ways to further reduce Payne effect.

Influences of Manufacturing Technology on the Mechanical Properties of Silicone Rubber Structures

2007 ◽  
Vol 537-538 ◽  
pp. 663-670
Author(s):  
József Keskeny ◽  
Antal Huba
Keyword(s):  
Mechanical Properties ◽  
Health Care ◽  
Silicone Rubber ◽  
High Purity ◽  
Fatigue Tests ◽  
Manufacturing Technology ◽  
Medical Materials ◽  
The Difference ◽  
Manufacturing Technologies ◽  
Silicone Rubbers

The paper presents the results of investigations made to clear how the different manufacturing technologies of silicone rubber structures affect the mechanical properties of the products. The problem is not obvious since there are numerous devices produced especially for the health care. We also controlled extreme high purity silicone rubbers and compared the results with data measured on simple industrial silicone rubbers. The aim was to see the difference between expensive medical materials and normal ones to simplify the fatigue tests and to decrease the costs of other mechanical investigations.

Application of Silicone TQ Resin Reinforced RTV Silicone Rubber in Architecture

2012 ◽  
Vol 529 ◽  
pp. 492-496
Author(s):  
Yang Li ◽  
Wen Juan Gu ◽  
Da Yu Yang
Keyword(s):  
Mechanical Properties ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Silicone Rubber ◽  
Tensile Testing ◽  
Room Temperature ◽  
Sol Gel ◽  
Thermal Stabilities ◽  
Silicone Rubbers ◽  
Rtv Silicone Rubber

A kind of silicone TQ resin was first synthesized with Dodecyltrimethoxysilane (WD10) and tetraethoxysilane (TEOS) by sol-gel method. And the RTV (Room Temperature Vulcanized) silicone rubbers using as-synthesized TQ silicone resins as filler were prepared. Thermal degradation and mechanical properties of these RTV silicone rubbers were studied by means of thermogravimetric analysis and tensile testing. The experimental results showed that both mechanical properties and thermal stabilities of RTV silicone rubbers were significantly improved by using the as-synthesized TQ silicone resins as filler. The RTV silicone rubber can be used to make the molds of architectural components ornamentation. The aim is not only to repair architectural components with decoration, but also for further study and research of ancient architectural conservation.

Basic Study of Continuous Ultrasonic Devulcanization of Unfilled Silicone Rubber

1999 ◽  
Vol 72 (1) ◽  
pp. 152-164 ◽  
Author(s):  
B. Diao ◽  
A. I. Isayev ◽  
V. Y. Levin
Keyword(s):  
Mechanical Properties ◽  
Silicone Rubber ◽  
Structural Characteristics ◽  
Density Measurement ◽  
Gel Permeation Chromatography ◽  
Processing Conditions ◽  
Basic Study ◽  
Gel Permeation ◽  
Branched Structure ◽  
Better Than

Abstract The present paper describes a basic study of the devulcanization of unfilled model silicone rubber vulcanizates using a continuous ultrasonic reactor. The devulcanization was conducted under several processing conditions. Cure behavior, rheological properties, structural characteristics of the devulcanized rubber, and mechanical properties of revulcanized rubbers were studied. Gel fraction and crosslink density measurement indicate that the rubber is partially devulcanized. The gel permeation chromatography (GPC) results imply that the creation of a branched structure in the network is a possibility after devulcanization. Under the optimal devulcanization condition, the mechanical properties of revulcanized rubber are better than those of the virgin rubber. Devulcanized silicone rubber was also blended with the virgin one. The blends show the same tensile strength and modulus as the virgin rubber but higher elongation.

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