What Is a Polymer

Plastic products are based on polymers, materials which are omnipresent in nature (cellulose, proteins) or in synthetic form (textiles, adhesives). In contrast to metals and other construction materials, polymers are organic materials with properties that depend strongly upon the environment in which they exist. A prerequisite to fully understand the life cycle of a plastic product is to examine the structure and nature of polymers. 

Polymers are giant molecules, or macromolecules, constructed from smaller repeating chemical units, or monomers. Polyethylene, for instance, is composed of macromolecules created by chemically joining many thousands ethylene monomers, and is represented by the formula (CH2)n- 

In contrast to thermoplastics, the polymerisation process for thermosets leads to the creation of a single giant three-dimensionally crosslinked molecule. The crosslinking process is generally irreversible and the resulting material will thus not melt upon subsequent heating. Examples of thermosets are unsaturated polyesters (UP), epoxies and polyurethanes (PUR). 

Natural and S5mthetic rubbers are also three-dimensional crosslinked networks of macromolecules. An example is styrene-butadiene rubber (SBR), obtained by linking SBS molecules with sulphur. 

The basic properties of some common polymers are given in Table 2.1. 

The ultra-high molecular weight polyethylene used in orthopedic applications is a type of polymer generally classified as a linear homopolymer. Our first task is to explain what is meant by all of these terms. Before proceeding to a definition of UHMWPE, one needs to first understand what constitutes a linear homopolymer. 

The principal feature of a polymer that distinguishes it from other materials, such as metals and ceramics, is its molecular size. In a metallic alloy or ceramic. 

The molecular chain architecture of a polymer also imparts many unique attributes, including temperature dependence and rate dependence. Some of these unique properties are further illustrated in the specific case of UHMWPE in subsequent sections of this chapter. For further background on general polymer concepts, the reader is referred to textbooks by Rodriguez (1989) and Young (1983). 

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What Is a Polymer, Anyway Call In the Special Forces... 

What Is a Polymer, Anyway Call in the Special Forces Hermann Staudinger and Herman Mark Who s the Fatherf Wallace Carothers and the First Synthetic Fiber From Globs to Fiber Chain-Growth Polymers... 

A (a) What is a polymer (b) What is the term for the smaller molecule that serves as the repeating unit making up a polymer (c) What are typical molecular weights of polymers (d) Name three polymers commonly found in the classroom and give their use or function. 

What is a polymer What is the difference between a polymer... 

What is a polymer Several answers can be given, but, for the moment, the most common and generally accepted definition is a system formed by an assembly of macromolecules—that is, a system of molecular entities with large dimension, which are obtained by the covalent linking of a large number of constitutional repeat units, more commonly called monomeric units. The macromolecular structures corresponding to this definition have molecular dimensions (characterized by their molar mass) much larger than those of the simple molecules. This, in turn, provides the polymer considered with properties of practical application—in particular, in the field of materials. 

What is a polymer This was a controversial question just before synthetic polymers were prepared for the first time, not to speak of "conducting polymers." The character of macromolecules was the topic of fimdamental discussions in the first half of the 20th century—one of the most fascinating scientific debates in the history of chemistry. After Hermann Staudinger s concept of covalent bonds between the building blocks of macromolecules was accepted by the scientific community, the tremendous scientific and industrial development of synthetic polymers got a new and even more expansive dimension. 

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