Chemorheological Study of Vulcanized Rubbers under Mechanical Stress

1972 ◽  
Vol 45 (4) ◽  
pp. 1074-1081 ◽  
Author(s):  
T. Kusano ◽  
Y. Suzuki ◽  
K. Murakami
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Mechanical Stress ◽  
Crosslink Density ◽  
Room Temperature ◽  
Mechanical Stimulus ◽  
Nitrogen Atmosphere

Abstract Below the glass transition temperature, the cleavage of molecular chains of extended vulcanized rubbers will occur. The crosslink density of vulcanized rubbers, which were placed at room temperature for about 4 h in a nitrogen atmosphere, increased about 17 per cent after extension of 200 per cent at −76° C. This may be due to the recombination of cleft chains, and this can be shown by the Maxwellian type of curves resulting from a plot of crosslink density as a function of forced strain. The decreasing proportion of crosslink density in the presence of radical acceptors in the rubbers and the increasing crosslink density in the absence of radical acceptors, because of recombination of cleft chains, was ascribed to the recombination of unstable chains produced by the added mechanical stimulus.

Silk Polymer Coating with Low Dielectric Constant and High Thermal Stability for Ulsi Interlayer Dielectric

1997 ◽  
Vol 476 ◽  
Author(s):  
P. H. Townsend ◽  
S. J. Martin ◽  
J. Godschalx ◽  
D. R. Romer ◽  
D. W. Smith ◽  
...  
Keyword(s):  
Thin Film ◽  
Dielectric Constant ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Integrated Circuits ◽  
Room Temperature ◽  
Polymer Network ◽  
Flow Characteristics ◽  
Interlayer Dielectric

AbstractA novel polymer has been developed for use as a thin film dielectric in the interconnect structure of high density integrated circuits. The coating is applied to the substrate as an oligomeric solution, SiLK*, using conventional spin coating equipment and produces highly uniform films after curing at 400 °C to 450 °C. The oligomeric solution, with a viscosity of ca. 30 cPs, is readily handled on standard thin film coating equipment. Polymerization does not require a catalyst. There is no water evolved during the polymerization. The resulting polymer network is an aromatic hydrocarbon with an isotropie structure and contains no fluorine.The properties of the cured films are designed to permit integration with current ILD processes. In particular, the rate of weight-loss during isothermal exposures at 450 °C is ca. 0.7 wt.%/hour. The dielectric constant of cured SiLK has been measured at 2.65. The refractive index in both the in-plane and out-of-plane directions is 1.63. The flow characteristics of SiLK lead to broad topographic planarization and permit the filling of gaps at least as narrow as 0.1 μm. The glass transition temperature for the fully cured film is greater than 490 °C. The coefficient of thermal expansivity is 66 ppm/°C below the glass transition temperature. The stress in fully cured films on Si wafers is ca. 60 MPa at room temperature. The fracture toughness measured on thin films is 0.62 MPa m ½. Thin coatings absorb less than 0.25 wt.% water when exposed to 80% relative humidity at room temperature.

The Effect of Thermal History on Porcelain Expansion Behavior

1989 ◽  
Vol 68 (9) ◽  
pp. 1313-1315 ◽  
Author(s):  
C.W. Fairhurst ◽  
D.T. Hashinger ◽  
S.W. Twiggs
Keyword(s):  
Thermal Expansion ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Heating Rate ◽  
Room Temperature ◽  
Heating Rates ◽  
Thermal Expansion Data ◽  
Temperature Range ◽  
Expansion Behavior

Porcelain-fused-to-metal restorations are fired several hundred degrees above the glass-transition temperature and cooled rapidly through the glass-transition temperature range. Thermal expansion data from room temperature to above the glass-transition temperature range are important for the thermal expansion of the porcelain to be matched to the alloy. The effect of heating rate during measurement of thermal expansion was determined for NBS SRM 710 glass and four commercial opaque and body porcelain products. Thermal expansion data were obtained at heating rates of from 3 to 30°C/min after the porcelain was cooled at the same rate. By use of the Moynihan equation (where Tg systematically increases in temperature with an increase in cooling/heating rate), the glass-transition temperatures (Tg) derived from these data were shown to be related to the heating rate.

A carbon nanotube–epoxy interface improved damping below the glass transition temperature

RSC Advances ◽  
2016 ◽  
Vol 6 (25) ◽  
pp. 21271-21276 ◽  
Author(s):  
Yung-Chi Chu ◽  
Ming-Hsiao Weng ◽  
Wen-Yi Lin ◽  
Hsin-Jung Tsai ◽  
Wen-Kuang Hsu
Keyword(s):  
Glass Transition ◽  
Carbon Nanotube ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Room Temperature ◽  
Viscous Drag

Composites made from fibers and epoxy display a low viscous drag and are rarely used as mechanical dampers at room temperature.

scholarly journals The Effect of Glass-cracking during Cooling in Liquid Nitrogen on Viability of Mint Shoot Tips

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 874D-874
Author(s):  
L.E. Towill
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Liquid Nitrogen ◽  
Plant Species ◽  
Room Temperature ◽  
Shoot Formation ◽  
Shoot Tips ◽  
Vitrification Solution

Cryopreservation using vitrification has been reported for several plant species. Shoot tips and vitrification solution were placed in semen straws and immersed in liquid nitrogen (LN). Cracking of the external glass occurred, but may be avoided by annealing slightly below the glass transition temperature before immersion. A varying percentage still cracked with some vitrification solutions. Rapid warming also can cause cracking. There is concern that cracking may reduce viability. Shoot tips from Mentha species were used to examine this problem. Glass cracking during either cooling or warming did not produce visible damage to shoot tips. Viability of shoot tips from tubes that cracked during cooling was not different from those that did not crack; however, shoot formation was slightly reduced. Cracking upon warming did not reduce viability nor shoot formation. Very slow warming reduced viability, but warming in either water or air (room temperature) gave higher levels of survival.

scholarly journals Brewer’s spent yeast as wall material for microencapsulation of food compounds

2019 ◽  
Author(s):  
Rafaela Polessi Saturno ◽  
Miriam Dupas Hubinger ◽  
Gabriela Vollet Marson
Keyword(s):  
Ascorbic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Room Temperature ◽  
Core Material ◽  
Wall Material ◽  
Operational Conditions ◽  
Particle Stability ◽  
Brewer’S Spent Yeast

The brewer's spent yeast hydrolyzed precipitate was used as wall material for microencapsulation of ascorbic acid by the spray drying technique. The wall material had its centesimal composition determined as well as some physicochemical aspects: surface charge, surface tension and glass transition temperature, in order to study the behavior of the material after being atomized and to identify the most suitable core material. Operational conditions were also studied in the spray dryer. After microencapsulation, a 64% yield and a microencapsulation efficiency of 100% were achieved. Microparticle analyses showed low values of water activity and high glass transition temperature, indicating absence of microbiological activity and great particle stability at room temperature, respectively, suggesting that this wall material is suitable for protecting the ascorbic acid.

Looking at Rubber Adhesion

1979 ◽  
Vol 52 (1) ◽  
pp. 23-42 ◽  
Author(s):  
A. D. Roberts
Keyword(s):  
Surface Roughness ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Surface Energy ◽  
Crosslink Density ◽  
Central Theme ◽  
Rubber Compound ◽  
Rate Dependent ◽  
Peel Adhesion

Abstract Rubber has been employed in contact with a variety of surfaces for decades, yet the adhesional mechanisms involved are not fully understood. This article describes fundamental investigations carried out over the last decade. Emphasis is placed upon the use of optical techniques for looking directly at the contact area rubber makes with another surface. The interpretation is based upon a rate-dependent surface energy approach. In this way it is possible to predict the level of peel adhesion between surfaces, for example, when a ball rolls on smooth rubber. Other examples treated in the same way are the time for detachment of a ball from a smooth rubber track under gravity, its resilience when bounced on the track, and its friction when slid over the track. The influence of surface roughness, electrostatic forces, surface bloom, and humidity are considered, together with rubber compound variables such as glass transition temperature, crosslink density, and fillers. The central theme is that the adhesional mechanisms all physically depend upon the product of surface properties and bulk viscoelasticity of the solids in contact.

Enhancement of the crosslink density, glass transition temperature, and strength of epoxy resin by using functionalized graphene oxide co-curing agents

2016 ◽  
Vol 7 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Jin Won Yu ◽  
Jin Jung ◽  
Yong-Mun Choi ◽  
Jae Hun Choi ◽  
Jaesang Yu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Graphene Oxide ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Epoxy Resin ◽  
Crosslink Density ◽  
Functionalized Graphene ◽  
Functionalized Graphene Oxide ◽  
Curing Agents

Epoxy nanocomposites are fabricated by using diamine-functionalized GO and exhibit high Tg, tensile strength, and crosslink density.

Effect of Crosslink Type on the Ultrasound Devulcanization of SBR Vulcanizates

1997 ◽  
Vol 70 (4) ◽  
pp. 641-649 ◽  
Author(s):  
V. Yu Levin ◽  
S. H. Kim ◽  
A. I. Isayev
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crosslink Density ◽  
Continuous Process ◽  
Ultrasound Irradiation ◽  
Processing Conditions ◽  
Power Ultrasound ◽  
High Power Ultrasound ◽  
Initial Fraction

Abstract Sulfur-cured non-reinforced SBR with different amounts of poly-, di- and monosulfidic crosslinks is devulcanized by high power ultrasound irradiation in a continuous process under various processing conditions. Total crosslink density, the proportion of polysulfidic crosslinks, gel fraction, and glass transition temperature are measured. The effect of the initial fraction of polysulfidic bonds on the devulcanization process is discussed.

scholarly journals Optimizing Viscoelastic Properties of Rubber Compounds for Ballistic Applications

2020 ◽  
Vol 10 (21) ◽  
pp. 7840
Author(s):  
Janis Karl ◽  
Franziska Kirsch ◽  
Norbert Faderl ◽  
Leonhard Perko ◽  
Teresa Fras
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Mechanical Stress ◽  
Mechanical Load ◽  
Superposition Principle ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Ballistic Impact ◽  
Dynamic Mechanical

Using interlayers of rubber adds a positive effect to the synergy of disruptor–absorber armors. Emerging from its viscoelasticity the material is able to transform mechanical stress into heat. The dynamic mechanical properties of elastomers depend on both ambient temperature and frequency of an applied mechanical load. The damping shows a maximum in the glass transition area. If the frequency of the glass transition is in the magnitude of the mechanical stress rate applied by ballistic impact, the elastomer will undergo the transition and thus show maximized damping. An ideal material for ballistic protection against small calibers is developed by making use of dynamic mechanical analysis and the time–temperature superposition principle. The material is later analyzed by ballistic experiments and compared to other nonideal rubbers with regard to glass transition temperature, hardness and damping. It is shown that by choosing a material correctly with certain glass transition temperature and hardness, the ballistic properties of a steel–rubber–aluminum armor can be enhanced. The chosen material (butyl rubber) with a hardness of 50 °ShA is able to enhance energy absorption during ballistic impact by around 8%, which is twice as good as other rubber with non-optimized properties.

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