Abstract : From the four major cotton areas, four storage locations were set up to test and statistically analyze the eight main quality indicators and their dynamic changes of lint samples during storage. After 1 year and a half of storage time, the average length of the upper half of the fiber, the breaking strength and the reflectivity showed a downward trend, and the length uniformity index, micronaire value, elongation at break and yellowness value increased, and the spinning was uniform. The trend of the sex index is still difficult to determine. In general, as the storage time increases, the grade or color grade of the lint decreases and the quality deteriorates. Different grades, different origins and different storage locations have a certain degree of influence on the trend of cotton quality indicators during storage.
Key words: cotton; storage; quality indicators; dynamic changes
In recent years, China's annual cotton consumption is more than 10 million tons, most of which have to be stored for a certain period of time, and some even reserve cotton that has been in stock for many years. Under natural conditions, cotton generally has problems such as poor color, reduced grade, reduced quality, and affected use value. Under the support of the AQSIQ public welfare industry research project, the research team and relevant units have carried out research on quality changes and control technologies during cotton storage. Using modern detection and analysis techniques, the main factors causing the decline of cotton grade and quality are discussed from the two aspects of cotton fiber's internal and external factors. Based on a large number of experiments and in-depth research, physical and chemical techniques are used to screen out Key measures and methods suitable for cotton storage, economy, practicality and safety. Establish technical methods and standards for monitoring cotton fiber associated with organisms and attachments during storage, and controlling cotton grade and quality degradation. This article focuses on the changes in the main physical properties of cotton samples during the one-and-a-half-year storage period and the results of the analysis.
1 , materials and methods
Locally produced 2~4 or 3~5 lint cotton was purchased from Weixian County, Hebei Province, Huanggang, Hubei, Shihezi and Korla.
There are 5 storage locations in Anyang, Weixian, Huanggang, Shihezi and Korla, which are naturally stored indoors and continuously record temperature and humidity. Anyang, Weixian, and Huanggang stored cotton samples of the above four origins at the same level as the quality label; Shihezi and Korla only stored local cotton samples.
From December 1st, 2010, sampling once every half month (stopping during the Spring Festival holiday), there are 42 samples in each of the 5 storage points (the first 3 times have some storage points are incomplete), unified collection Go to the Cotton Quality Supervision, Inspection and Testing Center of the Ministry of Agriculture in Anyang, and test the upper half of the sample (UHML), length uniformity (UI), fracture specific strength (STR), and micronaire by high-capacity fiber detector (HVI). Value (MIC), Elongation at Break (ELONG), Reflectance (Rd), Yellowness (+b), Spinning Uniformity Index (SCI), 8 physical properties, simultaneous determination of sugar, tannin, wax, Chemical components such as pectin and pigment.
Data processing and statistical analysis were performed using EXCEL and DPS (Data Processing System).
2 , results and analysis
2.1 Main quality indicators change with storage time
From December 1, 2010 to June 1, 2012, the storage time of the test cotton was one and a half years, and a total of 36 samples were taken. The detection results of the eight physical property indexes of all the samples sampled were averaged, and the changes of the cotton fiber quality indexes with the storage time were reflected in the form of a bar graph, as shown in Fig. 1 to Fig. 8.
From the test data, during the storage period of one and a half years, the average length, length uniformity index, micronaire value and spinning uniformity index of the upper half did not change much, and the fracture specific strength and reflectivity showed a downward trend and fracture extension. The long rate and the yellowness value are increasing. The trend of the last four indicators reflects the decline in the grade or color grade of lint as the storage time increases, and the quality deteriorates.
2.2 Influence of storage location on main quality of cotton
The three storage points in Anyang, Huanggang and Weixian have the same number of samples, the same source and the same quality label, so the data of sampling and testing are comparable. The results show that the storage location has little effect on quality changes.
2.3 Changes in the main quality of cotton of different grades during storage
Based on the grade 3, 4 and 5 cotton produced by Huanggang stored in Anyang, the changes of main fiber quality indexes of different grades of cotton during storage were analyzed and compared. From the current trend, the fracture specific strength of grade 3 and grade 4 cotton is faster than that of grade 5 cotton, while the trend of yellowness rise is that grades 3 and 4 rise faster than grade 5. This result means that higher grade cotton is more susceptible to color and strength.
2.4 Changes in main quality of cotton during storage in different producing areas
　　 The DPS software was used to compare the changes of main quality indexes of cotton in different producing areas during storage. The results of the difference analysis of elongation at break, breaking strength, reflectivity and yellowness are shown in Table 1 - Table 4. The data show that the change of elongation at break of cotton stored in Korla and Shihezi is extremely different from that in Weixian County. The fracture strength of Korla storage cotton has reached a very significant difference in the other three areas. Huanggang, Weixian and Shihezi have also reached There is a significant difference; the reflectance change of Huanggang is extremely different from that of Korla and Shihezi; there is no significant difference in the yellowness of the four locations.
Table 1 Differences in the change of elongation at break during cotton storage in different producing areas
Place of origin | Korla | Shihezi | Huanggang | Wei County |
5% significant level | a | Ab | Bc | c |
1% extremely significant level | A | A | AB | B |
Table 2 Differences in the change of fracture specific strength during storage of cotton from different producing areas
Place of origin | Korla | Huanggang | Wei County | Shihezi |
5% significant level | a | b | c | c |
1% extremely significant level | A | B | C | C |
Table 3 Differences in reflectance changes during cotton storage in different producing areas
Place of origin | Korla | Shihezi | Wei County | Huanggang |
5% significant level | a | a | Ab | b |
1% extremely significant level | A | A | AB | B |
Table 4 Differences in yellowness variation during cotton storage in different producing areas
Place of origin | Wei County | Huanggang | Korla | Shihezi |
5% significant level | a | a | a | a |
1% extremely significant level | A | A | A | A |
　　 Note: The lowercase letters between the production areas in Table 1 - Table 4 indicate that the difference does not reach a significant level, the lowercase letters indicate that the difference reaches a significant level; the uppercase letters between the origins indicate that the difference does not reach a very significant level, and the uppercase letters indicate that the difference is reached. Extremely significant level.
　　 3 , discussion
　　 Among the eight major fiber quality indicators, the average length of the upper half, the length uniformity index, and the micronaire value did not change much, but from the sampling test of 42 packs of cotton during the one-and-a-half-year storage period, almost all of them were presented. The trend is that the length is shortened, the length uniformity index is increased, and the micronaire value is increased. If the storage time continues to increase, will this trend continue? Further verification of the detection and analysis of stored samples is pending.
　　 With the prolongation of storage time, the fracture strength is weakened, the reflectivity is decreased, and the yellowness value is relatively easy to understand, but what is the cause of the general increase in elongation at break, and whether the fracture strength is different from the elongation at break Inevitable negative correlation? It is also a question worthy of further discussion.
　　 The spinning uniformity index is a comprehensive index that reflects the spinnability of the fiber and the strength of the yarn. In general, the larger the SCI value, the better the yarn strength and spinnability. The empirical formula is: SCI=-414.67+2.9×Str-9.32×Mic+ 49.17×Len(in)+4.74×UI+0.65×Rd+0.36×(+b)[1], where Len(in) stands for inches The length of the representation. It can be seen that the spinning uniformity index is related to fiber length, length uniformity index, fracture specific strength, micronaire value, reflectance and yellowness. In the 42-pack cotton sampling test data, the spinning uniformity index increased and decreased in proportion. Therefore, the existing test data is also difficult to determine the tendency of storage time to affect the spinnability of cotton.
　　 Under indoor natural conditions, the changes in various quality indicators during cotton storage are slow. One and a half years of storage, sampling, testing and analysis are only a preliminary study. More complete results require more in-depth research to reveal .
　　 references:
[1] Yu Xiaoxin. Introduction to the HVI SPECTRUM Application Manual for Large Capacity Rapid Testers [J]. China Fiber Inspection, 2003 (6): 32-34.
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