Early Materials

It appears that clay may have been the first material to be treated and reworked by humans so as to produce new properties. This 

The first artificial materials were almost certainly fashioned after similar materials found in nature. For example, natural glass is formed when sand is heated to high temperatures, as when it is struck by lightning. One can imagine that early humans witnessed this phenomenon and decided to replicate that process themselves. By the fourth millennium b.c.e., Egyptian artisans had learned how to make glass heads and other objects, although the manufacture of useful objects, such as vases, apparently did not occur until about 1500 b.c.e. 

The first significant breakthrough in metallurgy occurred some time after the fourth millennium b.c.e. Metallurgy is the study of metals and the process by which they are extracted from the Earth and converted to useful objects, such as alloys. This event was the discovery of methods for the production of bronze, the first alloy. An alloy is a mixture of two or more elements (at least one of which is a metal) with properties different from those of the elements themselves. Bronze is made from copper and tin in a ratio of at least 9 parts copper to 1 part tin. The temperature required to convert the two elements into the alloy is relatively low (slightly more than the melting point of copper, 1,083°C) and could he attained in ovens available at the time. 

Early artisans knew nothing, of course, about the chemical process by which bronze was formed. The first step in that process is usually the conversion of copper and tin oxides to the pure metals. Carbon present in a fire (in the form of charcoal) is the reducing agent in this process  

The Bronze Age lasted until about 1200 b.c.e., when iron became the new metal of choice for the manufacture of objects. As with bronze, iron was probably produced accidentally in campfires long before it became widely popular. Iron ores occur commonly in nature, and they are reduced at relatively modest temperatures in reactions similar to those for copper and tin. For example  

---

Another impetus to expansion of this field was the advent of World War 11 and the development of the atomic bomb. The desired isotope of uranium, in the form of UF was prepared by a gaseous diffusion separation process of the mixed isotopes (see Fluorine). UF is extremely reactive and required contact with inert organic materials as process seals and greases. The wartime Manhattan Project successfully developed a family of stable materials for UF service. These early materials later evolved into the current fluorochemical and fluoropolymer materials industry. A detailed description of the fluorine research performed on the Manhattan Project has been pubUshed (2). 

Composite resins can be cured using a variety of methods. Intraoral curing can be done by chemical means, where amine—peroxide initiators are blended in the material to start the free-radical reaction. Visible light in the blue (470—490 nm) spectmm is used to intraoraHy cure systems containing amine—quin one initiators (247). Ultraviolet systems were used in some early materials but are no longer available (248). Laboratory curing of indirect restorations can be done by the above methods as well as the additional appHcation of heat and pressure (249,250). 

Very rapidly, a number of other anticoagulants, including the indanediones (4), (Structure 2), were developed as rodenticides. Warfarin first came into wide usage as a rodenticide in 1950 and virtually supplanted all other materials then in use. In the case of all these early materials, multiple bait applications were needed to control rodent populations which, while making the materials safer to use than the available acute poisons, curtailed their use in underdeveloped and less affluent countries because of the large quantities of bait that must be placed to destroy the populations of rodents. 

This chapter covers literature published since 1982 early materials are included here only where needed as a basis for describing further developments or where not previously mentioned in CHEC-1 <84CHEC-l(5)669>. The structural types surveyed here include 1,2,3-triazoles, benzotriazoles, their dihydro derivatives and carbocyclic fused compounds. Compounds with heterocyclic fused rings are not included. The nomenclature system was discussed in CHEC-T <84CHEC-I(5)670>. 

AT-(29-l>789]. This survey of the literature covers all forms of reference materials — books, periodicals reports — published thru April. 1958. It includes early material on basic physics props of materials... 

I must also acknowledge a core of dedicated secretaries, who over the years continually updated the early material for classroom use, particularly Mrs. Helen Eggleston and Mrs. Denise Junod. The author is especially indebted to Mrs. Nancy Qvale, who was responsible for the preparation of a major portion of the final manuscript for the first edition. 

Comparable to thiophene, pyrrole is a five-membered heterocycle, yet the ring nitrogen results in a molecule with distinctly different behavior and a far greater tendency to polymerize oxidatively. The first report of the synthesis of polypyrrole (PPy) 62 that alluded to its electrically conductive nature was published in 1968 [263]. This early material was obtained via electrochemical polymerization and was carried out in 0.1 N sulfuric acid to produce a black film. Since then, a number of improvements, which have resulted from in-depth solvent and electrolyte studies, have made the electrochemical synthesis of PPy the most widely employed method [264-266]. The properties of electrosynthesized PPy are quite sensitive to the electrochemical environment in which it is obtained. The use of various electrolytes yield materials with pronounced differences in conductivity, film morphology, and overall performance [267-270]. Furthermore, the water solubility of pyrrole allows aqueous electrochemistry [271], which is of prime importance for biological applications [272]. 

Materials reaching early Materials with adequate heat Materials with adequate heat flashover and low smoke and high smoke... 

Lunt, Shaw, and Schneller, in contributions of 13,7,6,7, and 1 pages, respectively. The present review is intended as an extension of the one published in this series in 1963." Early material has been included here briefly only where needed as a basis for describing further developments. Of these, the three most significant seem to be ring opening, a great expansion of physical chemistry, and the increased use of triazoles as starting materials for synthesis, topics which other reviews cover insufficiently. Time, temperature, and yields of reactions will be recorded to help the synthesis chemist. 

Early materials which showed changes In solubility upon UV exposure were Fish glue, asphalt, sugars, gelatins sensitized with... 

In conclusion it may be said that the vapor phase hydration of olefins under pressure to form alcohols does not appear promising because of the major difficulties involved, notwithstanding the rather favorable theoretical possibility. On the other hand, considerable evidence has been amassed and a number of patents issued to show that hydration of olefins in solution is a commercial possibility. This early material has been very carefully collected and summarized by Brooks. 3... 

A number of companies have tried to promote PET as a molding compound. In 1966, the first injection molding grades of PET were introduced however, these early materials were not very successful. The primary problem was that PET does not crystallize very rapidly a molded object composed of a crystallizable polymer caught in an amorphous or partially crystallized state would be rather useless. In service such a part could crystallize, shrink, distort, crack, or fall. The obvious solution was to use hot molds and hold the parts in the mold until the crystallization process was completed. Postannealing also permits continued crystallization. These approaches, especially with glass fiber incorporation, led to... 

As a result of CMU s IP focus, 21 of the 28 issued US patents, pins several active applications, protect the fundamental ATRP process or improvements in the fundamental process, (26,27,30,33-48) while only five of the twenty eight address novel polymer compositions. (28,29,36,49,50) Nevertheless, these early material-focused patents disclose a nnmber of materials that were not prepared by other CRP procednres until a later date. The difference in numbers is due to the fact that two issued patents are directed towards improvements in nitroxide mediated polymerization. (20,51) The first discloses an atom transfer radical addition reaction to form an alkoxyamine that has fonnd nse in ATRP kinetic studies, and the other focnses on rate enhancement of a NMP. 

Details and background on early materials research efforts have been published (3-7). A detailed discussion of present encapsulation materials will be published soon ( ). This report covers the application testing of developed materials and other requirements for successful vacuum lamination. 

---