Extraction Process of Color Powder and Cotton Screen Printing with Natural Dyes from Longan Leaf Powder

Area of Science:

• Textile Chemistry
• Sustainable Materials
• Agricultural Waste Valorization

Background:

• Longan leaves are abundant agricultural waste in Thailand.
• Conventional textile dyeing contributes to chemical pollution.
• There is a need for sustainable and biodegradable textile dyes.

Purpose of the Study:

• To develop a natural powdered dye from longan leaves for screen printing on cotton fabric.
• To optimize the dyeing process for enhanced color strength and fastness.
• To evaluate the environmental benefits of using longan leaf dye.

Main Methods:

• Longan leaves were processed into a powdered dye using boiling, filtration, drying with maltodextrin, and grinding.
• The dye was mixed with starch paste and applied to cotton fabric via screen printing at varying temperatures and times.
• Postmordanting with alum and ferrous sulfate, with or without tannic acid pretreatment, was performed.
• Fourier-transform infrared spectroscopy (FTIR) analysis confirmed functional groups.
• Color strength (K/S), lightness (L*), and colorfastness were evaluated.

Main Results:

• A reddish-brown powdered dye with a particle size of 15.381 μm and a yield of 20.53% was obtained.
• Higher dye ratios and temperatures increased color strength (K/S = 1.21).
• Tannic acid pretreatment, especially with ferrous sulfate, significantly enhanced mordant binding, yielding a dark blackish-brown tone (K/S = 6.56).
• Excellent colorfastness ratings were achieved for washing (5) and dry cleaning (5), and good ratings for water (4-4.5) and perspiration (4-4.5).

Conclusions:

• Longan leaf dye is a viable, sustainable alternative for eco-conscious textile screen printing.
• The process utilizes agricultural waste, reduces chemical pollution, and offers good color performance.
• Further research could explore cost optimization and broader application of this natural dye.