Effect of Initial Molecular Weight of a Rubber on the Strength and Fatigue of Its Vulcanizates

1957 ◽  
Vol 30 (1) ◽  
pp. 54-60
Author(s):  
G. M. Bartenev ◽  
A. S. Novikov ◽  
F. A. Galil-Ogly
Keyword(s):  
Molecular Weight ◽  
Dynamic Testing ◽  
Three Dimensional ◽  
Maximum Load ◽  
Testing Conditions ◽  
Maximum Deformation ◽  
Molecular Weights ◽  
Permanent Set ◽  
Dimensional Network ◽  
Equilibrium Modulus

Abstract (1) With decrease of the original molecular weight of rubber, there is a parallel decrease of the durability of its vulcanizates when they contain the same percentage of combined sulfur. On the other hand, this decrease of durability with decrease of the original molecular weight is only slight for vulcanizates having the same equilibrium modulus, i.e., the same density of crosslinks in the three-dimensional network. (2) In dynamic testing which involves repeated stretching, the durability depends on the testing conditions when the vulcanizates contain the same percentage of combined sulfur and at the same time when either the original molecular weight of the rubber is low or the equilibrium modulus is small. On the contrary, when the original molecular weight or the modulus is high, the durability does not depend on the testing conditions. When vulcanizates have the same equilibrium modulus, their durability depends on the original molecular weight. In this latter case the durability increases with increase of the molecular weight, independent of the testing conditions (given maximum load, given maximum deformation, etc.), and reaches a practically constant value at high molecular weights. (3) The fundamental influence of the original molecular weight on the strength and dynamic durability of vulcanizates containing the same percentage of combined sulfur is manifest in the retardation of the formation of a spatial network in low-molecular rubbers when vulcanized. With rubber of low original molecular weight, vulcanization leads to the formation of a thin space network and consequently a large number of molecular chain ends outside the network. For this reason, vulcanizates of low-molecular rubbers when tested are characterized by high permanent set.

scholarly journals Penetration Efficiency of Antitumor Agents in Ovarian Cancer Spheroids: The Case of Recombinant Targeted Toxin DARPin-LoPE and the Chemotherapy Drug, Doxorubicin

Pharmaceutics ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 219 ◽  
Author(s):  
Evgeniya Sokolova ◽  
Olga Kutova ◽  
Alena Grishina ◽  
Anton Pospelov ◽  
Evgeniy Guryev ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Antitumor Agents ◽  
Three Dimensional ◽  
Growth Factor Receptor ◽  
Ovarian Adenocarcinoma ◽  
Chemotherapy Drug ◽  
Molecular Weights ◽  
Epidermal Growth ◽  
Cancer Spheroids ◽  
Targeted Toxin

The efficiency of delivering a therapeutic agent into a tumor is among the crucial factors determining the prospects for its clinical use. This problem is particularly acute in the case of targeted antitumor agents since many of them are high-molecular-weight compounds. In this work, the penetration of therapeutic agents of two distinct molecular weights into the spheroids of ovarian adenocarcinoma overexpressing human epidermal growth factor receptor 2 (HER2) was studied. It was shown that the low-molecular-weight chemotherapy drug, doxorubicin (~0.5 kDa), effectively penetrates through almost the entire depth of a 300 to 400 μm spheroid, while the penetration depth of the HER2-specific recombinant targeted toxin, DARPin-LoPE (~42 kDa), is only a few surface layers of cells and does not exceed 70 μm. The low penetration of the targeted toxin into spheroid was shown along with a significant decrease in its efficiency against the three-dimensional tumor spheroid as compared with the two-dimensional monolayer culture. The approaches to increasing the accumulation of agents in the tumor are presented and prospects of their use in order to improve the effectiveness of therapy are discussed.

Physical Properties of Fractions of GR-S and Their Vulcanizates

1949 ◽  
Vol 22 (2) ◽  
pp. 494-517 ◽  
Author(s):  
John A. Yanko
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Large Scale ◽  
Average Molecular Weight ◽  
Three Dimensional ◽  
Reduced Pressure ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
Straight Line ◽  
The Relationship

Abstract A large-scale precise fractionation of GR-S (X-55) was carried out at 25° C, using a fractional precipitation technique. Nine fractions, each weighing approximately 150 grams and comprising about 11 per cent by weight of the original unfractionated sample, were obtained, with number-average molecular weights varying from 4000 to 1,650,000. High molecular fractions undergo gelation rapidly, even when dried in the absence of light at reduced pressure, and the higher the molecular weight of the fraction, the greater the amount of gel formed. Compared to unfractionated butadiene-styrene copolymers of similar gel contents, the gel portions of the higher molecular fractions had unusually high swelling indices, indicating qualitatively that the average molecular weights between points of effective cross-linking in the three-dimensional gel structure were higher than those found in the past in unfractionated samples of similar gel contents. Through the concentration range studied, the intrinsic viscosity values varied as a straight-line function of the concentration terms for all the fractions. However, the negative slopes of these lines increased as the molecular weight of the fraction increased, demonstrating the greater dependence of the intrinsic viscosity values of the higher molecular fractions on the concentration variable. The relationship between number-average molecular weight, as determined by osmometric measurements, and limiting intrinsic viscosity of the GR-S fractions is given by the equation: [η]0=5.4×10−4 M0.66, which is similar to that obtained by French and Ewart. The μi values calculated from the equation of Huggins were essentially the same (0.35) through the molecular range 12,400 to 723,000.

Effect of Primary Molecular Weight on the Dynamic Properties of Cured Rubber

1959 ◽  
Vol 32 (3) ◽  
pp. 651-661
Author(s):  
E. V. Kuvshinskiĭ ◽  
M. M. Fomicheva
Keyword(s):  
Molecular Weight ◽  
Dynamic Modulus ◽  
Room Temperature ◽  
Dynamic Properties ◽  
Molecular Weights ◽  
Vulcanized Rubber ◽  
Equilibrium Modulus ◽  
Modulus Of Resilience ◽  
Molecular Weight Fractions ◽  
Butadiene Styrene

Abstract 1. Studied were the moduli of resilience and rebound elasticity of the vulcanized rubbers made from fractions of butadiene-styrene rubber “SKS-30-A” at temperatures of 20, 60, and 100° C in the region of molecular weights from 45,000 to 620,000 with various degrees of vulcanization (with variation in the pseudoequilibrium modulus from 5 to 70 kg/cm2). 2. The dynamic modulus of resilience is little dependent on the molecular weight of the original rubber both at room temperature and at higher temperatures. 3. At higher temperatures the elasticity of vulcanized rubber is mainly determined by the degree of vulcanization, the measure of which is the pseudo-equilibrium modulus, and is little dependent on the initial molecular weight. At low temperatures (20° C) elasticity increases with the degree of vulcanization, but it increases at different rates for vulcanized rubbers made from fractions with different molecular weights. At 20° C the increase in the degree of vulcanization increases the elasticity of vulcanized rubbers made from low-molecular fractions (45,000) to a lower degree than of those made from high molecular weight fractions (above 133,000). 4. The value of the maximum elasticity of vulcanized rubbers obtained from rubbers of the same molecular weight is not dependent on the type of accelerator used.

Effect of the Molecular Weight of Rubber on the Kinetics of Vulcanization and on the Formation of a Spatial Network

1954 ◽  
Vol 27 (4) ◽  
pp. 925-929 ◽  
Author(s):  
A. S. Novikov ◽  
G. M. Bartenev ◽  
F. A. Galil-Ogly
Keyword(s):  
Molecular Weight ◽  
Sodium Sulfide ◽  
Scientific Literature ◽  
Hydraulic Press ◽  
Butadiene Rubber ◽  
Spatial Network ◽  
Molecular Weights ◽  
Equilibrium Modulus ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization

Abstract From scientific literature it is known that the rate of vulcanization and the mechanical properties of rubbers depend on the value of the initial molecular weight of the rubber. However, the cause of the slow vulcanization of olw molecular rubbers and the effect of the molecular weight of the rubber on the formation of a spatial network and the structure of the vulcanizate remain unclear. In the present work the kinetics of vulcanization of separate fractions of butadiene rubber SKS-30A of molecular weight from 100,000 to 1,170,000 was studied by measurements of the equilibrium modulus and the proportion of combined sulfur. The SKS-30A rubber was divided into five fractions of molecular weights: I 1,170,000; II 700,000; III 500,000; IV 140,000; and V 100,000. The molecular weights were calculated from viscometric data according to the formula previously established for this rubber by the authors: [η]=2.96×10−4 M0.71. In order to keep the molecular weight of the rubber constant, sheets for vulcanization were prepared from a dispersion of the ingredients in a benzene-rubber solution. The composition of the mixture was the same for all the fractions, i.e., 100 parts by weight of rubber, 3 parts of sulfur, 1 part of mercapto-benzothiazole, 5 parts of zinc oxide, 2 parts of stearic acid, and 1 part of phenyl-β-naphthylamine. The sheets were vulcanized in a hydraulic press at 143° C for various periods. The amount of sulfur combined with the rubber was determined by Bolotnikov's method, specially adapted to small batches of vulcanizate. The rubber specimens, weighing 0.2–0.3 gram, were extracted in 50 cc. of sodium sulfide, and titrated with 0.01N iodine solution.

scholarly journals Fluorescent Characteristics and Metal Binding Properties of Different Molecular Weight Fractions in Stratified Extracellular Polymeric Substances of Activated Sludge

Separations ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 120
Author(s):  
Jingwen Lian ◽  
Yang Yang ◽  
Weiyi Qiu ◽  
Lijie Huang ◽  
Chuanhua Wang ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Molecular Weight ◽  
Activated Sludge ◽  
Metal Binding ◽  
Extracellular Polymeric Substances ◽  
Three Dimensional ◽  
Fluorescence Analysis ◽  
Quenching Effect ◽  
Molecular Weights ◽  
Different Molecular Weight

The combination of heavy metals and extracellular polymeric substances (EPSs) affects the distribution of heavy metals in microbial aggregates, soil, and aquatic systems. This paper aimed to explore the binding mechanisms of EPSs of different molecular weights in activated sludge with heavy metals. We extracted the stratification components of activated sludge EPSs and divided the components into five fractions of different molecular weight ranges. In the three-dimensional fluorescence analysis of each fraction, the EPSs of activated sludge had two peaks, peak A (representing low-excitation tryptophan) and peak B (representing high-excitation tryptophan), and static quenching was the main reason for the fluorescence quenching between the compounds attributable to peak A in activated sludge EPSs and Pb2+ and Cu2+. Further exploration suggested that the EPSs of activated sludge interacted with Cd2+, Pb2+, Cu2+, and Zn2+ to form new substances. The quenching effect of the EPSs with the highest molecular weight (100 kDa–0.7 μm) was more significant, and the binding ability was more stable. This study implies that the application of EPSs from activated sludge is promising. While effectively binding heavy metals, it can also reduce the volume of the excess activated sludge.

scholarly journals Shershnev coefficient is a basic characteristic of the structure of a crystallizing network polymer

2021 ◽  
pp. 4-5
Author(s):  
V. V. Kovriga ◽  
T. F. Oreshenkova ◽  
I. N. Pyatin
Keyword(s):  
Molecular Weight ◽  
Basic Characteristic ◽  
Network Polymer ◽  
Molecular Weights ◽  
Equilibrium Modulus

The values of molecular weight between nodes in cross-linked polyethylene obtained by the method of swelling and the method of determining the equilibrium modulus are considered. It has been shown that it is not possible to achieve uniform values of molecular weight between mesh points using these two methods. The ratio between the molecular weights located between the nodes of the network, it is proposed to call the "Shershnev coefficient".

Growth-Packed PPT-A Fiber for the Replacement of Native Asbestos

1989 ◽  
Vol 174 ◽  
Author(s):  
Han Sik Yoon
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Three Dimensional ◽  
Catalytic Amount ◽  
High Heat ◽  
Similar Process ◽  
Dimensional Network ◽  
One Step ◽  
Ultra High Molecular Weight ◽  
Lower Production

AbstractA now type of crystal that can be defined as a “gel crystal” was first made with oligomeric poly-p-phenyleneterephthalainide (PPT-A), associating a large amount of dimethylacetamide (DMAc) liquid molecules, in which catalytic amount of heterocyclic tertiary amine, coupled with alkali metal cations or phosphoric triamidos are incorporated. Under mechanical orientation of the growing PPT-A, before gelation of the reaction “mixture, a hark agar-like gel crystal is formed. It shows a strong optical birefrin,- gence with four clear extinction positions under crossed polarizers when the gel was sectioned either along the direction of PPT-A orientation or perpendicular to it. When the gel formed without orientation it exhibitil speckled birefringence due to a large number of tiny spherulitic crystallites. The degree of crystalline order was similar to that of lyotropic, nematic liquid crystals when evaluated from X-ray diffractograins. The same type of gel crystals with extinction positions were observed in animal and vegetable tissues. It is assumed that the gel crystal has a threedimensionally ordered molecular network structure in which oligo-PPT-A's are arranged end-to-end in parallel lines. The lines are connected laterally, to form sheets, by DMAc bridges that are linear associations of DMAc molecules, which are connected to the oligo-PPT–A at the CONH groups. PPT-A molecular growth and self-ordering occurs within this gel crystal. A similar process gives rise to wool, cotton and ol.her fibrous biological materials.The high molecular weight PPT-A fiber thus grown in the gel crystal is constructed with numerous unit fibrils which connect themselves in a three-dimensional network, that resembles native flax or ranie fibers. The molecular growth of PPT-A in the gel crystal reaches ultra high molecular weight that can rarely be attained in ordinary solvent polyinerization. The gel state of PPT-A fibrils are initially formed spontaneously by selfsubdivision of the gel crystal after the molecular growth of PPT-A. Solid fibrils and fibers are finally fortoed by removing DMAc. The PPT-A gel fibrils thus formed resemble closely “the nascent fibril” of cellulose, and the microstructure and morphology of PPT-A fibrils are consequently very similar to those of native cellulose. The thickness of PPT-A fibrils can readily be controlled by the temperature in the gel crystal before fibril formation. The direction of the fibrils depends on the initial orientation of oligo-PPT-A's immediately before the formation of the gel crystal.This growth-packed PPT-A fibril, that can be produced by a one step chemical reaction, is considered as a good candidate for the replacemerit of native asbestos, because of the lower production cost, microfibrillation property, and inherently high heat-resistance.

scholarly journals A fluorous sodium l-prolinate derivative as low molecular weight gelator for perfluorocarbons

2020 ◽  
Vol 56 (61) ◽  
pp. 8655-8658
Author(s):  
Redouane Beniazza ◽  
Natalia Bayo ◽  
Damien Jardel ◽  
Ruben Rust ◽  
Bosi Mao ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Three Dimensional ◽  
Low Molecular Weight ◽  
Left Handed ◽  
Dimensional Network ◽  
Low Molecular Weight Gelator

The fluorous sodium l-prolinate 1 self-assembles in perfluorocarbons to form a three-dimensional network of left-handed nano-helices resulting in solvent gelation.

Influence of Molecular Weight on the Non-Isothermal Melt Crystallization of Biodegradable Poly(D-Lactide)

2017 ◽  
Vol 751 ◽  
pp. 221-229
Author(s):  
Wanich Limwanich ◽  
Sawarot Phetsuk ◽  
Puttinan Meepowpan ◽  
Nawee Kungwan ◽  
Winita Punyodom
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Thermal Property ◽  
Three Dimensional ◽  
Crystallization Rate ◽  
Melt Crystallization ◽  
Kinetics Analysis ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
Biodegradable Poly

The influence of molecular weight of poly (D-lactide) (PDL) on the melt crystallization was successfully investigated by non-isothermal differential scanning calorimetry (DSC) technique. The synthesized PDLs with three different number average molecular weights (Mn) of 2.39×105 (PDL1), 1.09×105 (PDL2) and 0.61×105 (PDL3) were utilized in this study. From DSC kinetics analysis, it was found that the rate of PDLs crystallization increased with increasing cooling rate. Furthermore, the crystallization rate of PDLs was dependent on molecular weight and determined to be in the following order: PDL3 > PDL2 > PDL1. The crystallization mechanism was analyzed by the Avrami, Ozawa and Liu models. The mechanism of all PDLs crystallization was nucleation with three dimensional growths. Furthermore, the molecular weight of PDLs affected not only the crystallization rate but also the thermal property. As the molecular weight of PDLs increased, the melting temperature (Tm) increased but the heat of melting (∆Hm) decreased.

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