STATE OF RESEARCH REGARDING LENPUR WOOD FIBRE TO CLARIFY THE MECHANISM WITH REGARDS TO PERSPIRATION
LENPUR fibre performs an anti-odour action which is probably due to its particular structure or to the active components present in the wood of the four kinds of pine tree used in its preparation.
The first part of research was based on the following phases:
- Carrying out exhaustive bibliographical research on active components present in pine trees in the same family and their chemical characteristics;
- Analysis of the fibre using spectroscopy in order to emphasize particular chemical characteristics;
- Solvent extraction tests to extract any soluble substances and characterize them;
- Aqueous extraction tests using a variety of water solutions to verify the eventually ability of LENPUR to release active molecules that are able to interact with the ingredients of perspiration and deactivate them through chemical reaction.
As no information was available regarding the type of pine used in the production of LENPUR fibre, a sample of wood was provided for structural analysis. The results of analysis determined that the wood belonged to the Pinaceae family and the species could be the following:
- Pinus .……….
- Pinus. ……….
- Pinus. ………
- Pinus ……….
Bibliographic research was performed for these species that illustrated the possible, natural substances present in the wood. These substances could remain in the LENPUR fibre, and could be responsible for the deodorizing ability demonstrated in garments made with it. However, no results are available regarding the chemical composition and the structure of the wood.
The first phase of research was aimed at confirming the structural data available from IR studies, performed previously, using spectroscopic and chemical techniques. Confocal microscopic analysis was performed; however, it did not yield useful information regarding the structural differences in LENPUR and other cellulose fibres.
Carbon-hydrogen analysis was performed with the objective of obtaining an in-depth chemical characterization. This testing established that fibre is composed of carbon, hydrogen, and oxygen thus ruling out the presence of other elements such as nitrogen and halogens. This result was confirmed by further SEM analysis.
Based on these results, it was hypothesized that the deodorising action could be related to presence of natural substances, for example of terpenic nature, with double bonds able to easily react with components of perspiration (ex. α-pinene); or the structure of the fibre is characterized by elements that are present in larger quantities than in wood, like lignin, that are able to firmly bond these components by hydrogen bonding or other very firm bonds.
It was presumed that the harsh chemical treatment that LENPUR fibre undergoes during spinning would extract any natural substances, such as the non-structural components of wood, so these substances would not remain in the yarn. In any case, it was determined that it would be useful to verify this by performing release testing on the fibre with possible reactive substances. Comparative extraction was performed on Modal, Viscose and Lenpur fibres with a low polarity solvent (CH2CL2) and with a polar solvent (CH3OH, C2H5OH). The extracts were analysed by NMR and did not highlight the presence of particular substances in any of the fibres. This result confirms that volatile components present in the pinewood used for producing LENPUR fibre are removed during the fibre preparation process and successive spinning operations. Evidently the difference between Lenpur and other fibres must be of a structural nature dependant on the wood raw material.
Research was therefore turned to the examination of the adsorbent ability of substrates, examined using structurally defined molecules with different chemical and chemical-physical characteristics. Two active ingredients, Ketoconazole and Acetaminophen (or Paracetamol) were selected for testing purposes. The former has a complex structure, higher molecular weight, quite high lipofilicity, although it contains highly electronegative atoms with doublet electrons available for the formation of hydrogen bridges or electrostatic interaction with hydroxyfunctional groups present in cellulose or in lignin. Acetaminophen is a smaller, aromatic, molecule with a significantly lower molecular weight, characterized by a phenolic acid group and, on the whole, more polar than Ketoconazole.
Considering that the adsorbent properties demonstrated by LENPUR are seen in finished fabrics used for making clothing, the adsorbent tests were performed on white fabric made using the previously analyzed fibres.
Known weights of fabric were soaked in a 0.2% Ketoconazole in ethanol solution for 1 hour. After that time, they were removed from the solution and the excess solution was allowed to drip off and the fabric was air dried. The samples were then extracted using methanol. The active ingredients in the extract solution and in the remaining saturating solution after the experiment were determined by HPLC.
A second extraction was performed using the same method in order to have another measured parameter of absorbance power of the fibres. The results are shown in Table I.
Lenpur shows a trend of ability to bond with Ketoconazole that is similar to Viscose having a high absorbency value demonstrated by the total amount released in the two extractions.
Testing with Acetaminophen was then performed under the same experimental conditions. The data is shown in Table II.
All of the previously tested fibres showed a greater ability of bonding with Acetaminophen which is characterized by a lower molecular weight and by a greater polarity that permits it to better penetrate into their structure and remaining more strongly bonded. The greatest absorbency ability is shown by LENPUR demonstrated by the very low extraction concentration accompanied by a low concentration in the remaining solution. Evidently, LENPUR is able to establish stronger bonds with substrate demonstrating how different it is compared to the other fibres.