A thermomechanical investigation of highly cold-drawn polycarbonate

A new technique detecting molecular motions in drawn polymers was applied to highly cold-drawn polycarbonate of bisphenol A. It is shown that the sample exhibits thermal shrinkage in three steps with the temperature increase up to above the glass transition temperature. The molecular relaxation at the highest temperature is due to the glass transition. The other two molecular motions at the lower temperature are those of main chain in the glassy state and they correspond to the molecular motions as revealed in dielectric measurement by Sacher.¹ By using the general theory of the thermal analysis by Ozawa,² the apparent activation energies of these molecular motions were obtained: for the highest temperature 110 kcal/mole, and for the lowest temperature, 33.5 kcal/mole. The impact strength and the cold workability of this polymer are also discussed in relation to these molecular motions.     

Oberflächenlipide und Lipidpolymere von Pflanzen

Surface Lipids and Lipid Polymers of Plants The protective skin of higher plants, or cuticle, consists of a lipid coating and the characteristic polymer lipids cutin and suberin. The lipid coating contains hydrocarbons, wax, triterpenes, sterols and sometimes aldehydes and ketones. Cutin, an estolid, unsoluble in water and organic solvents, is built up by hydroxylated fatty acids with 16 and 18 C-Atoms. Suberin is in its constitution very similar to cutin. Its characteristic compounds are hydroxylated dicarbonic acids. To the degradation of cutin and suberin by men and animals some references have been given.     

The molecular weight distribution and oligomers of sodium hydroxide hydrolyzed poly(ethylene terephthalate)

Methanolic sodium hydroxide reacted more quickly than aqueous sodium hydroxide with poly(ethylene terephthalate) (PET). Larger amounts of low molecular weight deposits were formed at the product surface after the former treatment, also indicating the severity of this attack. The molecular weight distribution, obtained by gel permeation chromatography for the product of methanolic NaOH hydrolysis, had a population with 2400 peak molecular weight, which was not present on the chromatograph of the aqueous sodium hydroxide hydrolyzed product. This population is hypothesized to have been crystalline material. Extraction and analysis by high performance liquid chromatography of the low molecular weight products on the surface and in the bulk of the hydrolyzed PET samples, in comparison to controls, revealed the presence of more oligomeric species after hydrolysis. Also, more oligomeric species were present in the bulk extract of the methanolic sodium hydroxide hydrolyzed sample than in the aqueous NaOH hydrolyzed product.     

Induction plasma synthesis of fullerenes and nanotubes using carbon black–nickel particles

The existence of fullerenes (as allotropes of carbon) was established in the mid-1980s and during the last 15–18 years, systematic efforts have been devoted to improve the methods of their synthesis, including plasma-based system methods. The work presented here is focused on the investigation of fullerenes synthesis, using a radio frequency plasma reactor. The main objectives were to explore the use of induction plasma technology for the synthesis in-continuo of carbon fullerenes and to predict their formation conditions through conduct of theoretical studies. Thus, a thermodynamic study was carried out to predict the equilibrium composition of fullerenes produced at several combinations of operating conditions. Additionally, a statistical factorial design experiment, employing four factors at two levels, was also developed, in order to study the influence of the system’s operating parameters on the eventual C₆₀ fullerene yield. The results obtained showed that the reactor pressure, the electrical power and the raw material feed rates all have an important effect on the synthesis of fullerenes. The highest C₆₀ concentration in the products was found to be about 7.7 wt.%. Various other carbon nanostructures, such as nanotubes and nano-onions, were also successfully produced.     

Photochemical oxidation of fatty acid esters with and without chlorophyll

1. It has been confirmed that the principal products formed in the oxidation of methyl oleate by oxygen under a variety of conditions are predominantlytrans hydroperoxides. However no inversion of the double bond occurs in unoxidized oleate. Hence the conversion ofcis totrans double bonds and peroxide formation occur together in the same molecules.
2. The autoxidation of methyl linoleate at low temperature yields predominantlycis,trans conjugated hydroperoxides. Autoxidation at 25°C., oxidation catalyzed by visible light, or ultraviolet light and copper soap catalyzed oxidation at temperatures appreciably above 0°C., lead to the formation primarily oftrans,trans conjugated hydroperoxides. The inversion of the second double bond in this case appears to be independent of the peroxide-forming reactions.
3. The photochlorophyll oxidation of methyl linoleate leads to the formation of some unconjugated hydroperoxides, some of which containtrans double bonds.
4. Under all of the conditions employed in the present investigation, the oxidation of methyl oleate and linoleate led primarily to the formation of monomeric peroxides which retained most of the unsaturation of the parent compound.

     

Elimination of the halphen response of cottonseed oils in conjunction with deodorization

Two simple but effective pilot-plant processes were developed to produce Halphen-negative cottonseed oil. Both involve treatment of the oil with cottonseed fatty acids in a conventional batch type of deodorizer in conjunction with deodorization. In one process, in which the acids were added to the oil, the cyclopropenoids were inactivated in as short a time as 5 min after the oil reached the maximum temperature of 450–455 F. In the other, in which the acids were generated in situ, the oil did not become Halphennegative until about an hour and 45 min after it reached maximum temperature. The excess acids produced by both methods were readily removed during conventional deodorization. In contrast, deodorization alone reduced the cyclopropenoid content of the oil to a low level (0.02%) but did not render it Halphen-negative even after 3 hr at maximum temperature. These new processes are directly applicable for use by refineries that have the batch type of deodorizers. For refineries that operate continuous or semicontinuous deodorizers, it should be relatively simple to design preheating vessels or heat exchangers to inactivate partially or completely the cyclopropenoids before deodorization. Presented at the AOCS Meeting, New Orleans, May 1967. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Influence of silicon on the growth of barrier-type anodic films on titanium

Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at ∼60 V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of ∼40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength.