Definition of backpack March or go out in the back of the clothing package. Material diversification, leather, plastic, polyester, canvas, nylon, cotton bags and other fashionable texture. At the same time, in more and more flaunt the personality of the period, simplicity, retro, cartoon and other styles, from different sides to cater to fashion people, publicity personality needs. Luggage style from the traditional business bag, school bag, purse, extended to small sachet etc.. Material technology Because the backpack in a special environment, the backpack materials and processes put forward higher requirements. All the position of the knapsack force is sewn back to the needle and sewn in three times, so that the force position is firm and durable. The buckle and other components of the backpack can be frozen, smashed and deformed at 120 degrees centigrade without damage. Backpacks are mainly 420D, Oxford nylon, 1000D nylon, 600D or 1000Dpolyester (polyester), or 1000D, CORDURA and other materials. 1000D material has high density and is very wearable and is suitable for use in the field. CORDURA is a famous high quality wearable nylon roving fabric developed by DuPont Co. The wear resistance of this material is much higher than that of ordinary nylon or polyester, and it is light in weight. More than 90% of the world's most famous brand backpacks are made of this famous nylon material. These materials can withstand 0.5m~2m water pressure, so that the object in the package to keep dry. Some materials also have anti tear function, once punctured, the gap will not tear open to enlarge. Development status As everyone's living and consumption standards continue to rise, a variety of backpacks become indispensable accessories around people. We all request that the bags and bags products be strengthened not only in practicality, but also in decoration. China bags is a big country of production, China has been formed in Guangdong Huadu, Fujian Quanzhou, Zhejiang Pinghu and Hebei Baigou four PVC bag manufacturing base. There is a huge demand space in the international luggage market, which has directly promoted the export growth of Chinese luggage and bags, and made the export of bags steady growth and good momentum. In 2007, the export value of China's luggage was 10 billion 810 million US dollars, up 24.21% over the same period, and the number of exports was 7 billion 779 million, an increase of 21.56%. Category use According to the different backpack capacity, the backpack can generally be divided into large and medium-sized categories Large Backpack Capacity of more than 50 liters, suitable for medium and long distance travel and more professional adventure. For example, when you want to go to places like Tibet You should undoubtedly choose a large backpack with a capacity of more than 50 litres when traveling or exploring mountains. In some short trips if you need a large backpack also need camping in the wild, because only it can hold your camping tents, sleeping bags and pads. Large backpacks, depending on the use of different, can be divided into climbing bags and long-distance travel backpack. The mountaineering bag usually has a long and thin bag, so the bag can be divided into two layers through the narrow topography, and the middle part is separated by a zipper interlayer, so that when the goods are taken away, it is very convenient. The sides and the top of the backpack can be provided with tents and mats outside, and the volume of the backpack is virtually increased. There axe backpack sets, can be used for bundling axes, with the poles. The most noteworthy is the back structure of these bags, the bag has light Aluminum Alloy support package body frame, the back of the shape is designed according to the principle of human body engineering, the strap is wide and thick, shape according with the human physiological curve of "S" type design, and prevent the straps to both sides of the chest belt sideslip make the wearer feel very comfortable. And these backpacks all have a strong, generous and comfortable belt, and the height of the straps can be adjusted. The user can conveniently adjust the strap to the height suitable for himself according to the figure of the user. Generally, the bottom of the backpack is positioned above the hips, so that more than half of the weight of the backpack is transferred to the waist, thereby greatly reducing the shoulder burden and reducing shoulder damage due to long-term weight-bearing. Long distance travel backpack bag structure is similar to mountaineering bags, but the bag body more generous, and is equipped with many side bags, so that the object classification system is placed, long-distance travel backpack front usually can be opened to take items is very convenient. The volume of medium backpack in general 30~50 litres, use these packs more widely, 2~4 days of field trips, travel between the city and some long-distance travel non camping self-help, medium-sized backpack is appropriate. Carry on clothes and some daily necessities can hold. The style and variety of medium-sized backpacks are more varied. Some backpacks add side pockets, which are more conducive to repacking. The back structures of these backpacks are about the same as those of large backpacks. The capacity of a small backpack is below 30 litres. These backpacks are mostly used in the city. Of course, they are also suitable for 1~2 day outings.