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《38 Women’s Day》

 

International Women’s Day is celebrated on March 8th every year. It is a globally recognized and respected day. Dating back to March 8, 1909, the United States Chicago labor women’s strike march rally, women’s Day has gone through more than a hundred years of history. Even in China, Women’s Day has been around for a long time since the Republic of China, when all kinds of new ideas, ideas and things were introduced together. So, do you know the origin of Women’s Day is what?

 

 

38 Women’s Day is also known as international Working Women’s Day. Internationally, the full name of Women’s Day is “United Nations Day of Women’s Rights and interests and International Peace”, is the world’s women strive for peace, equality, development of the festival. Over the past century, women in various countries have made unremitting efforts to fight for their rights.

On March 8, 1909, women workers in Chicago, Illinois, and workers in the national textile and clothing industry held a huge strike and demonstration, demanding an increase in wages, the implementation of the 8-hour working day and the right to vote. This was the first organized mass struggle of working women in history, which fully demonstrated the strength of working women. The struggle received widespread sympathy and warm response from women in the whole country and even other countries in the world, and finally won the victory.

 

 

Before the First World War, the shadow of war hung over the world, and imperialists tried to carve up colonies. In August 1910, the second International Socialist Women’s Congress was held in Copenhagen, the capital of Denmark. The meeting was attended by representatives of 17 countries. The main issues discussed at the meeting were to oppose imperialist military expansion and war preparation and safeguard world peace. They also discussed the protection of women’s and children’s rights, the fight for the 8-hour workday and women’s suffrage. Clara Zetkin, the famous German socialist revolutionist and outstanding communist fighter who led the meeting, proposed that March 8 every year be the world women’s Struggle Day, which was unanimously supported by the delegates. Since then, “38” women’s Day has become the world’s women to fight for rights and liberation of the holiday.

 

 

Clara Zetkin

March 8, 1911 was the first International Working Women’s Day.

Our country started in 1922 to commemorate the March Eighth.

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Rubber dry rubber series – natural rubber

 

Directory

1 Current Situation of Chinese Natural Rubber

2 Ingredients in NR

3 The Structure of Natural Rubber

4. Nature of NR

 

Natural rubber

1, the current situation of Chinese natural rubber

As everyone in the industry knows, NR mainly comes from Southeast Asia. Do you know why our country can’t produce NR rubber by itself?

As far as I know, there are mainly the following reasons: (1) Climate: the growing environment of NR can only be located at 18° south to 18° north latitude, and the southernmost part of China is at 19° north latitude. Therefore, Hainan is the main NR production base in China, but the planting area is very limited. The output in 2020 is only about 600,000 tons, and the self-sufficiency rate is only 13%. ② Backward production technology: The production line of China’s NR in Hainan is still the same as that of 10 years ago, with low production efficiency and a large amount of labor. As a result, China’s NR produced by itself cannot compete with Southeast Asian countries in terms of production capacity and quality. Meanwhile, the cost of China’s NR produced by itself is at least 1000-2000 yuan more expensive than that of Southeast Asian countries. The price fluctuation of NR is too big, especially the impact of this epidemic.

Now this situation, our country will face a lot of strategic problems, as we all know, fighter aircraft, large aircraft tires due to a large load, the strength of the requirements are particularly high, must use NR, but also must be NR in the highest strength of the cigarette glue, but our country is no way to supply to meet the requirements of the cigarette glue, completely rely on imports, This is a difficult place, so the country has been trying to change the living conditions of NR, hoping to change the cold tolerance of rubber trees by genetic means, so that rubber trees can be planted in more places in China. Of course, this technology is really difficult, our teachers in Beihua have done a lot of work, but no breakthrough has been made. At present, the main research in the academic world is dandelion, and this northernization has made a breakthrough. At present, the northernization has made tires by using dandelion. However, there is a particularly big problem that the NR latex that can be extracted from dandelion is too little, which cannot be realized in industrialization. What our teachers are doing now is to change the roots of dandelions through genetic technology, hoping to grow roots as big as turnip, so as to increase the yield of NR produced by dandelions.

 

 

2. Components of NR

It can be seen that NR has about 5-8% rubber components, and these non-rubber components will directly affect the final characteristics of NR.

 

3. Structure of natural rubber

The structure of NR is much more complex than that of polycis-isoprene, which is why isoprene rubber does not have the same properties as NR rubber. As can be seen from the figure, in addition to the main intermediate cis-isoprene, the molecular weight of natural rubber also contains two end-groups, -α and w’. The research results show that the α-end group is formed by the combination of phosphate ester group and phospholipid, and the w’ end group is formed by the combination of several trans-isoprene and some special proteins, which combines with the above structure. Here are two of the most important features of NR:

① The molecular weight is huge, can reach millions of levels, processing is difficult, gel content is high, need to plasticizer

The reason for the huge molecular weight is that natural rubber α-terminal group forms gel network through hydrogen bond or intermolecular force

 

 

4. Properties of NR

The main characteristics of NR have been clearly explained above, and I will summarize them briefly as follows:

The raw rubber green has high strength, good extrusion and calendering performance, smooth extrusion surface and low shrinkage rate

② Elasticity: natural rubber has medium elasticity, BR>NR>IIR, which is mainly considered from steric hindrance

③ Strength: NR has the best tensile property and excellent strength in general rubber

(4) Processing properties: large molecular weight, high viscosity of raw rubber Mooney, need to plasticize to further processing

⑤ Low temperature resistance: medium to high: glass transition temperature is about -70℃

⑥ Solvent resistance: if a material does not react with the solvent and is not miscible, the material is resistant to the solvent performance, and NR is non-polar rubber, non-polar gasoline, diesel, variable pressure oil, resistance to polar solvents: water, ethanol

⑦ Chemical reactivity: NR rubber has very high chemical reactivity, so the aging resistance of NR is poor, it must be anti-aging treatment; At the same time, the high chemical reactivity of NR can also be used to prepare epoxidized NR and hydrogenated NR. For the two special NR, there are still many ways to write an article on the chemical modification of rubber later.

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