Optimization Of Test Method For Polymerization Degree Of Ramie Cellulose

The degree of polymerization of ramie cellulose is a physical and chemical index indicating the degree of cellulose damage,which can objectively and quantitatively reflect the value of the degree of cellulose damage in spinning,weaving and dyeing process.At present,the test method used in China is GB/T 5888-1986"Determination of polymerization degree of ramie cellulose".It plays an active role in regulating the production,purchase and processing of ramie fiber and controlling the quality level of ramie fiber.However,it has been more than 30 years since its promulgation and implementation,and has not been revised for a long time.The original standard has exposed certain defects and deficiencies,including the old model of experimental equipment and non-standard test conditions.In order to solve these problems,this paper tries to improve the accuracy,stability and repeatability of the test results of cellulose polymerization degree,and provides theoretical basis and complete test data for revising GB/T 5888-1986 standard.（1）In view of the poor solubility of cellulose in the current GB/T 5888-1986 standard,the solubility and polymerization degree of hramie after traditional alkali degumming were tested by single factor experiment and orthogonal experiment respectively.The relationship between solubility and polymerization degree of 40mg hemp cellulose and dissolution time,dissolution temperature and Cu²⁺concentration was studied.The solubility increased with the increase of dissolution time,dissolution temperature and Cu²⁺concentration,and the degree of polymerization decreased with the increase of dissolution time.After comprehensive consideration,the optimal dissolution process was obtained as follows:dissolution time 30min,dissolution temperature 25℃,Cu²⁺concentration 0.4（0.5）mol/L.On the basis of this process,its solubility can reach 100%,and the test results of polymerization degree are least affected by time.（2）Improve the test method in view of the current GB/T 5888-1986 standard,the viscometer is too old,the sampling site is too arbitrary,the sampling size is unclear and other problems.In the end,Nordic standard viscometer was adopted instead of Austenimeter as a new measuring instrument,mid-section sampling method was adopted instead of random sampling method,and the sample size of crushed sample was 20～35 mesh sieve（0.5～1mm）instead of the sample size of chopped sample below 1mm.It can effectively improve the accuracy,stability and repeatability of ramie cellulose polymerization degree test.Finally,the influence of lipid wax content on the degree of polymerization was also investigated.When removing lipid wax,the degree of polymerization of cellulose decreased,and the removal of lipid wax must be carried out before obtaining accurate degree of polymerization data.（3）The traditional method and the improved method were used to test the degree of polymerization of four ramie fibers and two hemp fibers after traditional alkali degumming,hydrogen peroxide sustained-release alkali degumming and TEMPO degumming respectively,and the stability of the test data was compared to determine the optimal method for the degree of polymerization of hemp fibers.The degree of polymerization can also be used as an indicator to evaluate the quality of cellulose after degumming of bast fiber.Generally speaking,the quality of cellulose after traditional alkali degumming of bast fiber is the best,while the test results of cellulose after hydrogen peroxide sustained-release alkali degumming and TEMPO degumming are generally the same.Combined with hemp composition analysis,the method of characterization of Yuan Ma china-africa the percentage of the fiber composition of cellulose,and adopts the theory for the first time the concept of degree of polymerization and the measured degree of polymerization,to explore Yuan Ma polymerization degree and refined dried-jute the relationship between the degree of polymerization,using fiber damage percentage to determine Yuan Ma come unglued after the quality of cellulose.