The Effect of the Vulcanizing System on Cure and Mechanical Properties of Nbr/Epdm Blends

2001 ◽  
Vol 9 (7) ◽  
pp. 459-468 ◽  
Author(s):  
Marcia G. Oliveira ◽  
Bluma G. Soares
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Glass Transition ◽  
Crosslink Density ◽  
Mechanical Performance ◽  
The Other ◽  
Glass Transition Temperatures ◽  
Sulphur Concentration ◽  
Curing Characteristics ◽  
Accelerator System

The effect of the curing system and curing parameters, mechanical properties, ageing resistance, and crosslink density of NBR/EPDM blends has been investigated. The curing characteristics of the blends were affected by the accelerator type and the sulphur concentration. The sulphur/benzothiazyl-disulphide (S/MBTS) vulcanizing system offered the best scorch safety, whereas those single and binary accelerator systems based on tetramethyl thiuram disulphide (TMTD) provided faster cure. The MBTS single accelerator system was able to crosslink the EPDM phase better and consequently displayed better mechanical performance than the other systems based on tetramethyl thiuram disulphide (TMTD). Higher thermal stability was also achieved in blends containing higher levels of sulphur, probably because of increased crosslinking in the EPDM phase. The results of dynamic mechanical investigations showed differences in the glass transition temperatures, which increased with increasing of the sulphur content in both S/MBTS and S/MBTS/TMTD vulcanizing systems. Formulations based on S/TMTD single accelerator systems gave the lowest values of Tg, and the amount of sulphur did not affect this property.

Diene Termonomer Type and EPDM Properties

1972 ◽  
Vol 45 (5) ◽  
pp. 1334-1347 ◽  
Author(s):  
K. C. Baranwal ◽  
G. A. Lindsay
Keyword(s):  
Thermal Stability ◽  
Thermogravimetric Analysis ◽  
Aging Temperature ◽  
Crosslink Density ◽  
Oxidative Degradation ◽  
Lower Proportion ◽  
The Other ◽  
Almost All ◽  
Accelerator System ◽  
Crosslink Densities

Abstract The objective of this work was to study the effects of the type of diene termonomer on properties, especially thermal stability and aging, of EPDM polymers. Five different EPDM polymers using ethylidene norbornene (ENB), butadiene (BD), dicyclopentadiene (DCPD), methyltetrahydroindene (MTHI), and 1,4-hexadiene (HD) as termonomers were made at equimolar unsaturation. The same sulfur/accelerator system was used for curing these polymers. In both gum and filled vulcanizates ENB-EPDM is the fastest curing. In gum stocks HD-EPDM is the slowest curing, but is faster than DCPD-EPDM in filled stocks. These polymers, except for BD-EPDM, have about the same initial crosslink densities. Crosslink density and crosslink type analyses indicate that butadiene units in BD-EPDM chains are blocked. For HD-EPDM, both in gum and filled vulcanizates, 50 per cent of original crosslinks are monosulfidic. The other four EPDM vulcanizates have a lower proportion of monosulfidic crosslinks. At 350° F aging temperature, both ENB and HD polymers have ∼65 per cent monosulfidic crosslinks and about the same energy-to-break values (Eb). However, the higher original monosulfidic crosslink content of HD-EPDM does not seem to offer any better aging than for other polymers. DCPD-EPDM at 350° F aging temperature has the same monosulfidic content but increases further at 550° F aging temperature. At 550° F aging temperature almost all the crosslinks are monosulfidic for these EPDM polymers but the total crosslink densities and Eb are very low presumably due to oxidative degradation. Thermogravimetric analysis in N2 shows that these vulcanizates decompose in 800-935° F temperature range. In air, this range is 750-935° F.

scholarly journals Molecular dynamic simulation of performance of modified BAMO/AMMO copolymers and their effects on mechanical properties of energetic materials

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ke Wang ◽  
Huan Li ◽  
Jun-qiang Li ◽  
Hui-xiang Xu ◽  
Chao Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Diffusion Coefficient ◽  
Glass Transition ◽  
Molecular Dynamic ◽  
Energetic Materials ◽  
Molecular Dynamic Method ◽  
Dynamic Method ◽  
Mechanical Performance ◽  
Amino Group ◽  
Glass Transition Temperatures

Abstract Based on molecular dynamic method, densities, mechanical behavior and mechanical performance of P(BAMO/ AMMO) (Polymer 1) and two novel modified P(BAMO/AMMO) (Polymer 2: containing amino group, Polymer 3: containing nitro group), and their effects on mechanical properties of four energetic materials are investigated, the main results are as follow: Polymer 2 (1.235 g/cm3, 240 ± 5 K) and Polymer 3: 1.281 g/cm3, 181 ± 3 K) possess higher densities and lower glass transition temperatures than Polymer 1 (1.229 g/cm3, 247 ± 4 K). The modification makes Polymer 1 difficult to expand, improves its mechanical properties, but has few effect on its diffusion coefficient at same temperature and state. In addition, three binders are compatible with TNT, HMX and CL-20, and may react with DNTF. All polymers particularly improve rigidity of four energetic materials, and enhance their ductility except Polymer 2 on TNT. The ability of Polymer 2 and Polymer 3 improving rigidity (except Polymer 3 on HMX) and ductility of TNT and HMX is inferior to that of Polymer 1, but it is contrary for CL-20 and DNTF (except Polymer 2 on rigidity of DNTF). Moreover, Polymer 2-based interfacial crystals exhibit higher rigidity than Polymer 3-based interfacial crystals.

Comparative study of transparent polyimides derived from bis(ether anhydride)s and bis(ester anhydride)s using 2,2′-bis(trifluoromethyl)biphenyl-4,4′-diamine

2016 ◽  
Vol 29 (2) ◽  
pp. 218-226 ◽  
Author(s):  
Yu Zhou ◽  
Guofei Chen ◽  
Wei Wang ◽  
Liping Song ◽  
Xingzhong Fang
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Tensile Strength ◽  
Glass Transition ◽  
Comparative Study ◽  
Step Method ◽  
Glass Transition Temperatures ◽  
Step Procedure ◽  
One Step ◽  
Solution Polycondensation

Two series of polyimides (PIs) derived from bis(ether anhydride)s and bis(ester anhydride)s using 2,2′-bis(trifluoromethyl)biphenyl-4,4′-diamine were synthesized via solution polycondensation. The poly(ether imide)s could be formed by the conventional one-step method, while the poly(ester imide)s were only afforded by the two-step procedure. The resulting PIs had glass transition temperatures ( Tgs) in the range of 224–320°C and exhibited good mechanical properties with tensile strength in the range of 80.5–96.5 MPa, tensile moduli 2.7–6.9 GPa, and elongations at break 1.5–17.3%. It was found that the PIs derived from bis(ether anhydride)s showed higher thermal stability, better solubility, and transparency but lower Tg and higher water absorption compared with bis(ester anhydride)-based PIs due to the different ether and ester linkages.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Reverse Plasticity in Nanoindentation

2007 ◽  
Vol 1049 ◽  
Author(s):  
Yongjiang Huang ◽  
Nursiani Indah Tjahyono ◽  
Jun Shen ◽  
Yu Lung Chiu
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Glass Transition ◽  
Single Crystal ◽  
Metallic Glasses ◽  
Deformation Mechanisms ◽  
Glass Transition Temperatures ◽  
Loading Rates ◽  
Nanoindentation Experiment ◽  
Properties Of Materials

AbstractThis paper summarises our recent cyclic nanoindentation experiment studies on a range of materials including single crystal and nanocrystalline copper, single crystal aluminium and bulk metallic glasses with different glass transition temperatures. The unloading and reloading processes of the nanoindentation curves have been analysed. The reverse plasticity will be discussed in the context of plastic deformation mechanisms involved. The effect of loading rates on the mechanical properties of materials upon cyclic loading will also be discussed.

Glass Transition Temperature, Mechanical Properties of Rice and their Relationships with Milling Quality

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Kobra Tajaddodi Talab ◽  
Mohd. Nordin Ibrahim ◽  
Sergey Spotar ◽  
Rosnita A. Talib ◽  
Kharidah Muhammad
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Moisture Content ◽  
Bending Strength ◽  
Bending Test ◽  
Transition Line ◽  
Transition Temperatures ◽  
Drying Process ◽  
Glass Transition Temperatures ◽  
Grain Moisture

Abstract Glass transition temperatures (Tg) of MR219 rice variety were measured by differential scanning calorimeter (DSC). State diagram was developed and used to evaluate drying process in this study. Glass transition temperatures range of 9.65- 61.79°C were observed for gains with moisture content of 26.8 – 7.4% (w.b.). For mechanical properties and milling test, statistical analysis was performed by using a two factor experiment in completely randomized design (CRD). Two selected factors were drying temperatures at 5 levels (40, 45, 50, 55, and 60°C) and final moisture content (FMC) at 4 levels (10-10.5, 11-11.5, 12-12.5 and 13-13.5%). Three–point bending test was applied to measure the mechanical properties of rice kernel. Generally, bending strength, apparent modulus of elasticity and fracture energy of brown rice kernel increased with decreasing the grain moisture content. Maximum bending strength was 35.69 and 33.64 MPa for 55, and 60°C, respectively. All samples that were dried at 55 and 60°C experienced to go through the glass transition line after reaching their temperature to the room temperature at the end of drying process. The effect of drying temperature, paddy FMC and their interactions on whole kernel percentage (WKP) and mechanical properties were significant (α = 0.05). An inverse relationship was observed between WKP and the percentage of strong kernels for all treatments.

Thermal Stability of Bulk Metallic Glasses. Influence on Mechanical Properties

1998 ◽  
Vol 554 ◽  
Author(s):  
J. M. Pelletier ◽  
Y. Jacquemard ◽  
J. Perez ◽  
R. Perrier de la Bathie
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Glass Transition ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Atomic Mobility ◽  
Heating Rates ◽  
Characteristic Temperatures ◽  
Shear Elastic Modulus ◽  
Thermal Stability Of

AbstractTwo Zr-base bulk metallic glasses were investigated in the present work. DSC experiments were performed at different heating rates (dT/dt). Evolution of the characteristic temperatures, glass transition and onset of crystallisation, were determined as a function of dT/dt. Evolution of shear elastic modulus and internal friction are measured as a function of temperature and resulting microstructural evolution; these evolutions are related to variation of the atomic mobility.

Sulfonated Polystyrene Ionomers Neutralized with Mixtures of Various Cations Studied by Dynamic Mechanical and Small-Angle X-Ray Scattering Techniques

2003 ◽  
Vol 778 ◽  
Author(s):  
Ho Seung Jeon ◽  
Ju-Myung Song ◽  
Joon-Seop Kim
Keyword(s):  
Glass Transition ◽  
Dynamic Mechanical Properties ◽  
The Other ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Dynamic Mechanical ◽  
The Matrix ◽  
Cluster Phase ◽  
The One ◽  
Zinc Cations

AbstractThe effects of the addition of mixed cations, i.e. Na+/Cs+, Ba2+/Cs+, and Ba2+/Zn2+, to the acid form sulfonated styrene copolymers on their dynamic mechanical properties and morphology were investigated. It was found that the matrix glass transition temperatures did not change with the ratio of the one cation to the other. As expected, however, the ratio of one cation to the other in the mixed cations affected cluster glass transition temperatures significantly. It was also found that the activation energies for the glass transitions for the matrix phase remained constant, while those for the cluster phase changed with the ratio of the two cations. In addition, the position of the SAXS peak was found to be affected by the type of cations. From the results obtained above, the decrease in the cluster Tg with increasing the amount of cesium and zinc cations in Na/Cs, Ba/ Cs, and Ba/Zn mixtures, were explained on the basis of the considerations of the size, charge, and type of cations, which alter the degree of clustering as well as ion-hopping mechanism.

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