摘要:

Thiazole sulfenamides as well as thiocarbamyl sulfenamides in the presence of dibenzothiazyl disulfide (MBTS) form synergistic combinations of rubber accelerators that provide technologically important rubber vulcanizates. The present investigation explores the feasibility of using thiophosphoryl sulfenamide with MBTS as a binary system of mutually activated accelerators in the vulcanization of rubber. The cure characteristics of the NR compound containing various proportions of diisopropyl thiophosphoryl-N-oxydiethylene sulfenamide (DIPTOS) and MBTS have been investigated keeping the total concentrations of the accelerators at 6 mmol per 100 rubber. The results indicated mutual activity of the mixed accelerators and significant enhancement of torque, modulus, and tensile strength of the resulting vulcanizates. The general character of the reaction of thiophosphoryl sulfenamide and MBTS has been established by replacing DIPTOS by diisopropylthiophosphoryl-N-cyclopentamethylene sulfenamide (DIPTCS), in the investigation. The mutual activity consequent upon the interaction of the accelerators can be demonstrated through isolation and identification of the reaction products formed in the early part of cure using the HPLC technique, which is also extremely helpful in explaining the cure behavior of the different stocks used in the investigation. The study reveals that diisopropylthiophosphoryl-2-benzothiazole disulfide (DIBDS), formed (in situ) as a result of interaction of DIPTOS and MBTS, plays an active part in improving the physical properties of NR vulcanizates. From the chemical analyses of the vulcanizates it is evident that the network structure obtained with the binary system of accelerators is highly rich in monosulfidic linkages that render the vulcanizates resistant to aging at 100°C.

ISSN:0360-2559    

DOI:10.1080/03602558908054601

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The adsorption of polymers to particles modifies the interaction between particles and hence changes the properties of the dispersion. Many industrial dispersions have adsorbed polymers, which allows the formulation to be processed more easily and/or to have desired physical properties. In the last decade there have been considerable advances in quantifying the role played by adsorbed polymers. This paper discusses recent advances, both theoretical and experimental, on the forces between polymer-coated surfaces. The forces between adsorbed homopolymers in good and poor solvents are described. The forces between terminally attached polymers in good solvents reveal that much longer ranges and stronger forces are present for this configuration, explaining the empirical observation that block and graft copolymers are much better colloidal stabilizers than homopolymers. The effect of having an incomplete layer of adsorbed polymer and the forces between adsorbed polyelectrolytes are also discussed. It is by understanding these forces which exist between particles that the physical properties of dispersed materials (e.g., colloidal dispersions such as paints, PVC plastics, etc.) may be modified to produce products of the desired processing form.

ISSN:0360-2559    

DOI:10.1080/03602558908054602

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Thermo-oxidative aging of high-impact polystyrene sheets at 100°C was followed for a period of 1300 h. Four different types of samples were used, viz., virgin and recycled once, three, and five times. The samples exhibited systemic changes as a result of discoloration. The DTA of those samples indicates a rapid deterioration in thermal stability as well as deterioration in the optical properties.

ISSN:0360-2559    

DOI:10.1080/03602558908054603

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Stereoregularity of photopolymerized isoprene was determined by NMR spectroscopy and compared with the stereoregularity of polyisoprene which was prepared usingn-butyllithium catalyst. It was found that photopolymerization of isoprene gave a high percentage oftrans-1,4, while then-Buli catalyst gave a high percentage ofcis-1,4 structure.

ISSN:0360-2559    

DOI:10.1080/03602558908054604

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Three types of fibers from different origins were subjected to thermal degradation through thermogravimetry and differential thermal analysis. Activation energies of the samples were calculated from the kinetics of the weight loss. The differences between the obtained values are discussed on the basis of structure and composition differences.

ISSN:0360-2559    

DOI:10.1080/03602558908054605

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The application of mechanical energy on micro- and macromolecular solid bodies has as a result the formation of some new and energy-rich surfaces, strongly activated and able to develop reactions that are difficult to accomplish in other conditions. By vibratory milling of vinyl monomers in the presence of crystalline inorganic substances, grafted polymers are obtained which can be successfully used as filling materials in poly(vinyl chloride) processing. As a result of mechanical activation, the heterochain macromolecular compounds form new functional groups that are able to react with the judiciously selected micromolecular compounds by polycondensation reactions. This type of synthesis has also been extended to the carbochain polymers. By mechanodegradation, the latter ones form radicallic macromolecular fragments which can be stabilized with acceptors of the aromatic diamine type, leading to the obtainment of new polymers with special mechanical properties. The mechanochemical complexation was activated by vibratory milling, ultrasonic treatment, and cryolisis; the polyamides, cellulose, and polyesters were employed as macromolecular ligands: and the ions of Ti, V, Fe, Ni, and Mn were used as complexing centers. The vibratory milling of vinylic, acrylic, and dienic monomers, of the aromatic rings as well as of the nitriles, can activate their polymerization. The reaction takes place in the absence of any initiator, by a radical or ionic mechanism, as a function of the monomer chemical nature, the medium, and the gaseous atmosphere, respectively. The mechanochemically synthesized products are characterized by high thermostability, special resistance to the aggressive chemical agents, reduced solubility, paramagnetism, semiconductor properties, and high mechanical strength. The polymers obtained by mechanochemical polymerization present the capacity of initiating the acrylic monomer's polymerization and, as a consequence, they are able to act as macroinitiators. The mechanochemical synthesis is therefore a method for obtaining some macromolecular compounds having special properties which make them different from their analogues that are synthesized by classical methods.

ISSN:0360-2559    

DOI:10.1080/03602558908054606

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0360-2559    

DOI:10.1080/03602558908054600

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor