Fatty Acid Degradation
Chemical reactions involving the interaction of atmospheric oxygen with the double bonds of oily substances on a textile surface can lead to yellowing and unpleasant odors. The process of unsaturated triglyceride oxidation is a common cause of spoilage in textiles and leather goods that contain residual natural fats or processing oils. If these oils are not properly removed during scouring or if they are added back during softening, they can react over time to form peroxides and aldehydes.
This degradation is accelerated by exposure to heat, light, and metal catalysts like copper or iron. Manufacturers must select stable, saturated oils for their finishing processes to prevent the deterioration of the fabric quality during storage and use.
Oxidative Sequence
The reaction begins with the formation of free radicals when the oil is exposed to an initiator like UV light or heat. During the progression of unsaturated triglyceride oxidation, these radicals react with oxygen to create hydroperoxides which then break down into various volatile compounds. This chemical shift is often visible as a persistent yellow stain that cannot be removed by standard laundering.
In severe cases, the oxidation process can generate enough heat to cause spontaneous combustion in piles of oily rags or tightly packed fabric rolls. This is a significant safety hazard in textile mills and industrial laundries where large quantities of materials are handled. Technicians use the peroxide value and the iodine value to measure the susceptibility of an oil to this type of degradation.
Fiber Yellowing
Preventing the discoloration and odor associated with oil breakdown is a requirement for maintaining the aesthetic and commercial value of premium textile products. When a brand experiences problems with unsaturated triglyceride oxidation, it often points to a failure in the cleaning process at the mill. If the natural oils in cotton or wool are not completely emulsified and rinsed away, they remain on the fiber surface and begin to oxidize as soon as the goods are packed.
This problem is particularly common in white or light colored fabrics where the yellowing is most noticeable. Retailers may find that a shipment of garments has developed a rancid smell or visible stains after sitting in a warehouse for several months. By using antioxidants and ensuring thorough scouring, manufacturers can eliminate this risk and provide a more stable product.
Chemical Boundary
The scope of this oxidation process is limited to unsaturated fats and does not affect fully saturated oils or pure mineral oils. While unsaturated triglyceride oxidation is a major concern for natural fibers, it is less of an issue for synthetic textiles that do not contain natural fats. However, the spin finishes and knitting oils used on synthetics must still be monitored for stability.
The rate of the reaction is highly dependent on the storage environment, with high humidity and temperature significantly increasing the speed of the breakdown. Designers must consider these factors when selecting finishes for products that may be stored for long periods. This chemical understanding is fundamental for ensuring the long term quality of high value textile goods.
