An investigation of the long term chemical stability and physical performance of PMD-citronellal acetal compared with dibutyl phthalate and BIS(2-ethylhexyl) terephthalate as plasticisers in selected cosmetic formulations
- Authors: Marx, Amor
- Date: 2019
- Subjects: Plastics -- Additives , Chemistry, Technical , Cosmetics
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/42574 , vital:36669
- Description: Plasticisers are used by cosmetic manufacturers to improve the film forming abilities of a product and increase flexibility of the film formed on the skin or hair surface, as is desired, for example, in nail lacquers and lip coats. In recent years authorities have banned several plasticisers in cosmetic products (mainly phthalates) since these substances may pose a wide range of health risks and can be harmful to the environment. It is, therefore, necessary to find alternative, safe plasticisers, preferably of natural origin e.g. bio-plasticisers which can replace the toxic phthalates and still impart the same desirable properties to the cosmetic products in which they are used. In this study, the novel bio-plasticiser para-menthane-3,8-diol-citronellal acetal (PMD-citronellal acetal) was selected to compare its stability properties and plasticising behaviour with well-known non-phthalate bis(2-ethylhexyl) terephthalate (DEHT) and the problematic dibutyl phthalate (DBP). The objectives were to determine if the novel bio-plasticiser PMD-citronellal acetal plasticising properties and chemical stability are similar or better than DEHT and DBP within two cosmetic formulations, viz. a nail lacquer and a lip coat formulation, after being incubated at elevated temperature (40 ˚C) over a three month period. The results showed that flexibility for all plasticised formulations remained stable at room temperature (21 ˚C) and elevated temperature (40 ˚C). Adhesion performance of DEHT and PMD-citronellal acetal nail lacquer formulations outperformed DBP nail lacquer formulations. Elevated temperature and storage time had no influence on the organoleptic properties of any plasticised formulation. PMD-citronellal acetal plasticised lip coat and nail lacquer formulations outperformed both DEHT and DBP nail formulations with regard to hardness. Fourier Transform Infrared Spectrometry (FTIR) studies revealed that neat DPB, DEHT and Acetal were chemically stable at room temperature and elevated temperature over a three month incubation period. Furthermore, the three plasticised nail lacquer and lip coat formulations remained chemical stable over the three month incubation period at elevated temperature. Chemical stability of the nail lacquer formulations was further evaluated by means of leaching tests using Solid Phase Extraction [1] and Ultra-Performance Liquid Chromatography (UPLC) at two temperatures (31 and 50 °C) and three time intervals (24, 48 and 72 hours). No leaching out of the nail lacquer formulation for Acetal and DEHT could be detected. It was observed that trace amounts of DBP leached from the nail lacquer formulation at 50 °C. DBP leaching decreased over time and was found to be statistically significant over the studied period. It can be concluded that PMD-citronellal acetal can be selected as bio-plasticiser which exhibits similar properties to DEHT based on the performance stability and non-leaching criteria, and can be used as an alternative plasticiser to the toxic DBP in cosmetic formulations.
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- Date Issued: 2019
A possible mechanism for enzymic depilation of skins
- Authors: Brady, Dean
- Date: 1989
- Subjects: Chemistry, Technical , Tanning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3877 , http://hdl.handle.net/10962/d1001611
- Description: Streptomyces fradiae is a bacterium which has been previously found to produce extracellular enzymes which are capable of wool degradation and skin depilation. Streptomyces fradiae 3739 and other strains of Streptomyces were found in this study to be able to degrade a keratin source (wool) to a considerable degree. However according to the evidence of SEM micrographs presented here the highly keratinised spindle cells of the paracortex are fairly resistant to protease attack, and it is the cementation material which binds these cells together which is initially degraded by the proteases. A large degree of correlation was found with the strains of Streptomyces studied, between the ability of the individual strains to degrade wool and the ability of their extracellular proteases to reduce the depilation load of sheepskins. With further analysis S. fradiae 3739 was found to produce at least one amylase and four or more proteases. The proteases as a group had maximal proteolytic activity in the 8.0-9.0 pH unit range, and were considerably thermostabilised by the inclusion of calcium ions into the reaction solution. The protease group was found to cause depilation of merino sheepskins. For comparative purposes a protease produced by a strain of Proteus vulgaris isolated from a staling hide with hair slip (natural depilation) was studied. The protease activity was maximal in the alkaline region between 8.0-9.0 pH units. Tbe protease appeared to be a single enzyme with a molecular mass of approximately 44 000 daltons. The protease was maximally active at 40°C, although it was only thermostable to 30°C. The enzyme was ineffectual as a depilant except when the skin was pre-treated with a strong alkali, preferably including sodium sulphite in the protease preparation. One of the most important differences between the extracellular proteases of S. fradiae and P. vulgaris was that the former were greater in variety and caused a greater decrease in the depilation load of sheepskins than the latter. Further research with mixtures of commercial proteases provided evidence that a synergistic depilatory effect occurs when proteases of complementary bond specificities are used in conjunction in enzymic depilatory preparations. Some form of strong alkali treatment of skins was found to be necessary to produce leather of the prerequisite quality when the skin was depilated by proteases, otherwise the skin was found to be depleted and stiff. Calcium hydroxide alone was found to be inadequate for this task, probably owing to the fact that it is less alkaline than the lime-sulphide mixture. The calcium hydroxide (lime) must therefore be used in conjunction with sodium hydroxide (which makes the solution as alkaline as that of the lime-sulphide solution) to produce leather comparable to that produced by the lime sulphide treatment. A combination of the information provided by the present research and that gleaned from the relevent literature allows for the construction of a model to represent the possible mechanism of enzymic depilation of skins, in which depilation is caused by the disruption of the basement membrane at the dermal-epidermal junction by the degradation of its constituent molecular components by general proteases, resulting in the removal of the epidermis and its associated wool or hair
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- Date Issued: 1989