In the production process of plastic woven bag manufacturers, the breaking force of woven bag wire drawing is one of the important links in the strength control of woven bags. How to control the breaking force of wire drawing, it is necessary to control the ratio of raw materials, the cooling forming of the diaphragm and the tensile strength of the wire drawing. Different equipment and environments may have different control methods. According to the theory of plastic weaving, below, plastic woven bag manufacturers will briefly talk about how to control the tensile strength:
1. The ratio of raw materials
Plastic woven bag manufacturers filled master batch is one of the main ingredients of raw material ratio, the role is to improve the physical properties of wire drawing and reduce costs. As the filling amount of the filler masterbatch increases, the tensile strength of the wire drawing will gradually decrease. Because the main component of the filler masterbatch is calcium carbonate, there is no tension. After adding a small amount of the filler masterbatch, it is dispersed in the gaps of the polyolefin polymer chain and has little effect on the tensile strength of the wire drawing. At this time, the wire drawing rigidity is improved. When the addition amount exceeds 20% to 25%, the filled masterbatch occupies the position of the polymer chain due to excess and hinders the elastic deformation of the polymer, so that the polymer chain cannot be fully stretched along the longitudinal external force, affecting the polymer chain The tensile orientation effect, the strength and rigidity of the wire drawing are significantly reduced. The drawing breaking force is less than 0.32N/tex, which cannot meet the requirements of the national standard GB/T8946. In the actual production process, the addition amount of filler masterbatch is more suitable in the range of 8%~12%.
2. Cooling of the diaphragm
The water tank is an integral part of the wire drawing machine. The temperature of the cooling water in the water tank affects the physical properties of the diaphragm after cooling and forming, and is also the main factor affecting the strength of the wire drawing. This is because polypropylene is a crystalline polymer material, and its crystal forms are various. During the natural cooling process, quite large α-type spherulites are often formed, which is difficult to stretch and stretch, which is not conducive to wire drawing. In the case of rapid cooling in the water tank, it is easy to form a crystal structure, the arrangement of the molecular chain of the crystal is poor, and the structure is loose, so it is easy to stretch the orientation.
From the perspective of crystallinity, when the water temperature is too low, the molecular chains of the incubation crystals have not been arranged in a timely and orderly manner and become a crystal array, so they lose their ability to move and their crystallinity decreases. When cooling slowly, the crystallinity increases. The tensile strength is greatly improved as the crystallinity increases. This is because the greater the crystallinity, the greater the force required to destroy the dense crystal structure, and its intracrystalline slip is more difficult than the amorphous crystal structure. However, rapid cooling will cause the crystallization rate to be too fast and delicate. If the water temperature is too high, the cooling will be slow, the growth of the crystal nucleus will be too large, and the tensile strength will be reduced. In the actual production process, the following two phenomena are often encountered: the cooling water temperature is too low, the film is brittle, and it is easy to crack. The wire breakage rate is high, and the diaphragm is stiff. When there are wrinkles, it is easy to break the wire through the splitting cutter; when the temperature of the cooling water is high, the membrane is soft and easy to flatten. If the temperature of the cooling water continues to rise, the crystals grow too large, and slubby filaments are likely to appear after stretching. From a comprehensive point of view, the cooling water temperature is preferably between 40 ℃ ~ 60 ℃. In the long-term production process of Shandong Pingo Packaging, the thickness of the wire drawing is between 0.035mm and 0.065mm, and the cooling water temperature is set at about 40°C. In the process of processing woven bags with a thickness of 0.029mm, a fineness of 70tex, and a width of 2.78mm, new polypropylene materials are used to produce wire drawing. Due to the low thickness requirements, the processing is difficult. When the cooling water was 40°C initially, the strength of the drawn wire after cooling was low, and some wire breakage occurred during stretching. When the temperature of the cooling water rose to 55°C, the strength of the drawn wire was improved, and the problem of broken wire was solved. The strength of the bag cloth has been strengthened.
In the production process of plastic woven bag manufacturers, the stretching of the drawing is to heat the drawing after cooling and setting to above the glass transition temperature and below the softening point, so that the polymer molecular chains are arranged in an orderly manner along the stretching direction to a large extent. To increase the attractive force between the molecular chains and improve the breaking force of the wire drawing. Therefore, the effective way to control the drawing and breaking force is to set an appropriate stretching ratio. The greater the stretching ratio, the higher the breaking force of the wire drawing. The size of the drawing multiple is determined by the breaking force and elongation at break. When the draw ratio is 5 times, the drawing breaking force is about 0.32N/tex. Generally, the manufacturer sets the draw ratio to 4-7 times. Our factory produces wire drawing of woven bags. Its process index thickness is 0.1mm and the linear density is 150tex. As a flat woven bag with special requirements, the tensile strength of the base fabric of the woven bag drawing needs to reach 1470N/50mm. Our factory will draw multiples Set to 7 times, after drawing, the tensile strength is 0.48N/tex (elongation at break 21%), the tensile strength of the woven bag base fabric is 1920N/50rpan, which is far greater than the national standard, fully guaranteeing the weaving The safety of bag filling.
The stretching ratio in the actual production of plastic woven bag manufacturers is constant, and the two indicators of breaking force and elongation at break are controlled by adjusting the drawing temperature of the wire drawing. In the case of a certain stretching ratio and stretching rate, the lower the stretching temperature, the better the degree of orientation. The tensile strength after orientation decreases with increasing temperature, but the decrease is not large. When the tensile temperature increases, although the tensile strength decreases, the elongation at break increases faster. When the stretching temperature decreases, the tensile strength increases faster, but the elongation at break decreases more.