Research progress on degumming technology of hemp fibers
Hemp,a type of natural lignocellulosic fiber,exhibits high tensile strength,specific modulus,favorable biodegradability,inherent antimicrobial properties,and dermatological comfort,rendering it a pivotal source of cellulose fibers in the realms of biocomposite materials,automotive engineering,and textile manufacturing.Nonetheless,prior to the transformation of hemp into high-value fiber,it necessitates meticulous degumming to segregate cellulose from non-cellulosic constituents.Degumming methodologies in China encompass predominantly chemical,physical,and biological approaches;yet,in view of considerations pertaining to cost-effectiveness,degumming efficiency,and environmental impact,a hybridized approach is commonly adopted.This amalgamated methodology is steered towards eco-friendliness,environmental conservation,and resource efficiency.Degumming constitutes the inaugural procedure in hemp fiber extraction,with its quality being pivotal for fiber isolation,thereby significantly influencing subsequent processing and product attributes,including fiber spinnability,yarn characteristics,final product quality,and serviceability.Early-stage degumming of hemp primarily relied on biological methods,encompassing pond retting,stack fermentation,and green stem desiccation.However,due to prolonged degumming durations,inconsistent outcomes,susceptibility to environmental and anthropogenic influences,and challenges associated with industrial scalability,biological degumming methods encountered limitations.Consequently,chemical,physical,and hybridized degumming methodologies emerged,substantially enhancing degumming control and efficiency.Chemical degumming,the most prevalent approach,offers outstanding degumming efficacy and rapid processing.Alkali treatment represents the predominant chemical degumming technique,while organic solvent degumming facilitates recycling advantages.Ongoing scientific and technological advancements have spurred the proliferation of diverse chemical degumming methods,including electrolysis-induced oxidizing plasma oxidation,electrochemical techniques,the Fenton process,and ionic liquid-based treatments.Chemical degumming markedly augments cellulose-non-cellulose segregation,exhibiting a bleaching effect on hemp fiber,thereby enhancing fiber aesthetics.However,due to associated environmental pollution concerns,extensive research endeavors have focused on pretreatment methodologies,acid-base concentrations,additive incorporation,and gum treatment sequences,fostering advancements in the cannabis industry.Physical degumming is also regarded as a viable method,comprising mechanical,flash detonation,ultrasonic,micro wave,and supercritical CO2 fluid techniques.These methods leverage external force or pressure application to induce fiber-gum separation by reducing interfacial forces.However,standalone physical degumming often proves inadequate and is typically employed as adjunctive pre-treatment or post-treatment in combination with other methodologies.Biological degumming encompasses microbial and enzymatic approaches.Microbial degumming necessitates meticulous strain selection to facilitate enzyme production for gum hydrolysis.However,stringent culture environment control is imperative to optimize microbial growth.Enzymatic degumming,an extension of microbial degumming,entails mixing enzyme solutions with hemp fibers to facilitate gum decomposition.This method allows for both single-enzyme and complex-enzyme degumming;however,stringent reaction condition control is essential to maximize enzymatic efficacy throughout the degumming process.To improve the degumming efficiency and ensure the quality of hemp fibers,a single degumming method obviously cannot meet the demand,so a combination of a variety of degumming methods is employed nowadays.It is necessary to continue to explore the impact of pretreatment,additives,etc,on the degumming efficiency and fiber quality.To reduce environmental pollution and energy consumption,the cultivation of strains and the extraction of enzyme solution in biological degumming still need to be further studied,and the combination of biological degumming and other degumming methods still needs to be paid attention to,which will be the key to the future development of hemp degumming.
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