Plastics chemical structure

Plastics Chemical structure a LDPE (-CH2CH2-) - (branched) HDPE (-CH2CH2-) - (linear) PET (-C6H6COOCH2 CH20C0-) - PP PVC -(-CHCH3CH2CH CH3CH2-) - (CH2CHC1CH2CHC1-) ... 

Although it is very difficult and probably of little value to produce an adequate definition of the word plastics , it is profitable to consider the chemical structure of known plastics materials and try to see if they have any features in common. 

In commercial plastics materials there are a comparatively limited number of chemical structures to be found and it is possible to make some general observations about chemical reactivity in the following tabulated list of examples ... 

No attempt will be made here to relate the toxicity of plastics materials to chemical structure. Nevertheless this is a topic about which a few words must be said in a book of this nature. 

In spite of their rather complicated chemical structure, which consequently involves rather expensive production costs, the bis-phenol A polycarbonates have achieved an important place amongst the speeiality plastics materials. 

After a brief historical review in Chapter 1 the following five chapters provide a short summary of the general methods of preparation of plastics materials and follow on by showing how properties are related to chemical structure. These particular chapters are largely qualitative in nature and are aimed not so much at the theoretical physical chemist but rather at the polymer technologist and the organic chemist who will require this knowledge in the practice of polymer and compound formulation. 

The chemical structures of the plasticizers are related to the properties they impart to polymers. 

Degradation Deleterious change in a plastic s chemical structure. 

Adhesion is usually controlled by means of various finishing agents. Mikhalsky noted in [260] that reactions between such agents and thermoplastics are hindered for a number of reasons, one reason being that the chemical structure of the polymer is formed before the treated filler is added. In the majority of cases thermoplastics do not contain reactive groups, if perhaps only at the ends of macromolecules where they enjoy little mobility. The probability of contact between the reactive groups of the agent and the plastic. 

Typically, large-scale gas filling makes the main characteristics of foam plastics — coefficients of heat and temperature conductivity, dielectric permeability, and the tangent of the dielectric loss angle — totally independent of the chemical structure of the original polymer [1],... 

To maximize control in setting tolerances there is usually a minimum and a maximum limit on thickness, based on the process to be used such as those in Tables 3-6 to 3-9. Each plastic has its own range that depends on its chemical structure, composition (additives, etc.), and melt-processing characteristics. Any dimensions and tolerances are theoretically possible, but they could result in requiring special processing equipment, which usually becomes expensive. There are of course products that require and use special equipment such as polycarbonate compact discs (CDs) to meet extremely tight tolerances. 

Tables 7-5 to 7-7 show that there are different orders of magnitude between plastics and metals. Depending on the application, plastics may be formulated and processed to exhibit a single property or a designed combination of electrical, mechanical, chemical, thermal, optical, aging properties, and others. The chemical structure of polymers and the various additives they incorporate provide compounds to meet many different performance requirements.

Vulcanization A process in which rubber or TS plastic (elastomer) undergoes a change in its chemical structure brought about by the irreversible process of reacting the materials with sulfur and/or other suitable agents. These cross-linking action results in property changes such as decreased plastic flow, re-... 

Ic. Cross-Linking of Polymer Chains.—Formation of chemical bonds between linear polymer molecules, commonly referred to as cross-linking, also may lead to the formation of infinite networks. Vulcanization of rubber is the most prominent example of a process of this sort. Through the action of sulfur, accelerators, and other ingredients present in the vulcanization recipe, sulfide cross-linkages are created by a mechanism not fully understood (see Chap. XI). Vulcanized rubbers, being typical network structures, are insoluble in all solvents which do not disrupt the chemical structure, and they do not undergo appreciable plastic, or viscous, flow. 

Sorption is defined as the bonding of a solute to a plastic. It is a physicochemical phenomenon related to the properties of the plastic and the chemical structure of the drug or other soluble components of the preparation. Interactions of this type can be determined by measuring the loss of the solute to the plastic at equilibrium under constant temperature conditions [11]. 

This book focuses on the relationships between the chemical structure and the related physical characteristics of plastics, which determine appropriate material selection, design, and processing of plastic parts. The book also contains an in-depth presentation of the structure-property relationships of a wide range of plastics, including thermoplastics, thermosets, elastomers, and blends. 

Three Ciba HALS stabilisers are currently approved for use in plastic food-contact materials in Europe (Directive 2002/72/EC, Plastic materials and articles used in contact with food.) These are Chimassorb 944, Tinuvin 622 and Chimassorb 2020. Their chemical structures are given in Figures 31-33, respectively. 

Most plastic materials are used because they have desirable mechanical properties at an economical cost. For this reason, the mechanical properties may be considered the most important of all the physical and chemical properties of high polymers for most applications. Thus everyone working with such materials needs at least an elementary knowledge of their mechanical behavior and how this behavior can be modified by the numerous structural factors that can be varied in polymers. High polymers, a few of which have their chemical structure shown in Appendix I, have the widest variety and range of mechanical properties of all known materials. Polymers vary from liquids and soft rubbers to very hard and rigid solids. 

Fig. 18a. 11. Chemical structures of commonly used plasticizers in membranes of ion-selective electrodes. DOS, dioctyl sebacate NPOE, nitrophenyl octyl ether.

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