Films of polyamides were exposed to heat, ultraviolet radiant energy, and different atmospheric conditions. The degradation products were collected in some cases and analyzed by mass spectrometric techniques. The unexposed and exposed specimens were examined by the following techniques to obtain information concerning the changes in chemical and physical structure of the polymer: infrared absorption, ultraviolet absorption , viscosity of solutions, measurement of dielectric constant and dissipation factor, photomicrography, X-ray diffraction, electron microscopy, electron diffraction, and effect of organic liquids. In addition, pyrolysis studies were made and some physical properties were determined. The results of the investigation show clearly that no single method gives a complete picture but that the results from several of the methods give an insight into the mechanism of degradation of poly ami des.Polyamide molecules are relatively unaffected by exposure to moderate temperature (60 0 C). However, loss of water and other volatile materials may cause changes in physcial properties. The effects of exposure to ultraviolet radiant energy are more pronounced, and degradation of the polyamide molecule occurs with accompanying loss of water and other volatile materials that act as plasticizers.The results of this inves tigation show that the general course of the degradation of polyamides is as follows :1. The polymer mol ecules break at the C -N bond of the peptide group creating smaller polymer molecules with the same unit of chemical structure. The fragments broken out are evolved as carbon dioxide, carbon monoxide, water, and hydrocarbons.2. The degree of crystallinity or local order changes, including alterations in hydrocarbon packing, dipole rearrangement, and hydrogen bridging.3. The amount of strongly bound water and/or organic liquids changes. These materials are probably bound by hydrogen bridging to the oxygen of the peptide group. They act as plasticizers for the polyamides. r. IntroductionOne of the major problems facing the plastics industry is the degradation of some plastics when exposed to certain service conditions. This problem has been investigated extensively by accelerated tests involving one or more physical properties. While empirical investigations of this type give information of value, they yield little or no information on the basic changes in the material. As a result, the value of the information now aVi),ilable is not only limited, but in too many instances the information cannot be used to predict behavior in actual service [1).1 The physical changes observed during degradation may result from (1) changes in the chemical structure of the plastic material, and (2) loss or changes in the compounding ingredients. The logical method of attack is to determine the specific chemical reactions involved in the degradation of the plastic and how these reactions are affected by the intensity of the conditions encountered.The degradation of the plastic type of polyamides was investigated as p...

Modification of the iodine-rJkali method is recommended, based on the observation that alkali added slowly to a solution of an aldose sugar containing a small amount of iodine will tend not to form sodium iodate, but to react very rapidly with the sugar, viz:By addition of the iodine and alkali successively in small portions, the concentration of sugar relative to the iodine-alkali or sodium hypoiodite is kept at a level favoring the sugar oxidation reaction. The formation of iodate, therefore, indicates the complete oxidation of the aldose to the monobasic acid. By this procedure only 2 ml excess of tenth normal iodine is necessary. This eliminates the 100 to 200 per cent excess iodine required by other methods, which has been found to cause overoxidation. The determination can be carried out in 10 minutes. Iodate formation, moreover, takes place more rapidly than the very slow oxidation of ketoses and nonreducing sugars. The oxidation of the nonaldehydic sugars consumes iodine and alkali in approximately the 4:5 ratio

to extrapolate the data in order to obtain the correct initial specific rotation of +89.4°in water for alpha larabinose. The observation of the final specific rotation, +105.1°, provided a check on the purity of the preparation.Table II Mutarotation of Alpha Z-Arabinose Calcium Chloride Tetrahydrate in Water Concn. 4.000%; temp., 20.0 * 0.5°m e after In., min.

The action of 75 percent sulphuric acid on methylisopropylcarbinol at 80°C results in the formation of 2 isomeric decenes, namely, 3,4,5,5-tetramethylhexene-2 and 3,5,5-trimethylheptene-2. The theory proposed by Whitmore for the polymerization of olefins does not explain the formation of the above products without the postulation of a complicated rearrangement. A theory is proposed for the polymerization of olefins, based on the apparent activation of the olefin molecule, causing it to behave as 2 fragments which then add to the double bond of another olefin molecule in the usual manner. This behavior is analogous to the addition of RMgX to a carbonyl group =C = to yield =C(R)-OMgX. From a consideration of the relative calorie strengths of bonds, it is predicted that a CC bond would be broken more readily than a C-H bond during the addition of the activated olefin molecule to another olefin molecule; thus the products to be expected differ markedly in many cases from those predicted on the basis of a labile hydrogen mechanism. This activation theory for the polymerization of olefins furnishes a simple mechanism for the diisoamylenes studied and for the formation of the known di-and triisobutylenes from isobutylene.

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