In order to obtain satisfactory film quality for blown film, in addition to have a suitable blown film machine, a suitable formula is also required. The main effects that the blown film formula needs to achieve are: good tensile strength, good film stretch rate, good film tearing strength, and strong hand feeling. These are the four main functions that the blown film formula must achieve. The key skills of the formula: 1. Understand the resin density 2. Understand the resin melt index 3. Understand the density of the comprehensive formula, so that you can know the performance of the formula. The basic principle of ingredients: as far as possible to reduce costs while meeting customer needs. There are several main points to reduce costs, namely: 1. Add filler to increase weight, 2. Add recycled materials to replace new materials. But pay attention to the four prerequisites, otherwise the customer will run away, and the gain will not be worth the loss! Shanghai Duxia Industry and Trade Co., Ltd. now introduces some common blown film formulas and explains them for free, hoping to help our downstream customers. LDPE new material LLDPE LDPE recycled material
Shanghai Duxia Industry and Trade Co., Ltd. has compiled the basic operating points of the film blowing machine. This article mainly explains the operating points of the film blowing temperature, film blowing speed, inflation ratio, traction ratio, and die gap. 1. The temperature of the film blowing machine. Heating up the blown film temperature is the first step in stable operation. Put a few pellets of the raw material to be processed near the vent hole of the die and heat it until it melts by finger pressure. Generally, the die head is divided into two or three temperature zones, and the temperature at the end near the discharge port is slightly lower than the temperature in the other zones. The setting temperature depends on the raw material: LDPE≈140~160°;HDPE≈210~180°;PP≈230°In many cases, the raw material used for film blowing is not a single resin raw material but a mixture of many raw materials, so the temperature is based on On-site observation can be adjusted to the appropriate film temperature.The basic method of heating the main engine: For example, the low-pressure heating method: Zone 1 180 Zone 2 190 Zone 3 190 Zone 4 195 Zone 5 180 Among
Features of metallocene polyethylene film Metallocene polyethylene refers to a polyethylene material prepared by reaction with a metallocene catalyst, referred to as metallocene (mPE). Compared with the LLDPE made by ordinary Ziegler-Natta catalyst, mPE has a relatively narrow molecular weight distribution and a more uniform composition distribution, so the produced film has high strength and good uniformity in longitudinal and transverse strength. Due to the narrow molecular weight distribution and very low content of low-molecular substances, it has good anti-chemical extraction and anti-pollution properties, and the film has low viscosity; at the same time, it does not contain ultra-high molecular substances, so there are fewer crystal points. mPE film has excellent physical and mechanical properties, such as puncture resistance, impact resistance, high tensile force, and good tearing characteristics. The mPE film has good heat sealing performance, low sealing temperature, wide heat sealing temperature range, low melting point peak, shortened heat sealing time, good sealing performance, and greatly reduced leakage and fracture. In addition, mPE film also has moisture resistance, gas barrier, oxidation resistance, oil resistance, freeze resistance, cooking resistance, chemical corrosion resistance, non-toxic, tasteless, and does not affect the nutritional content of food, which is required for food packaging. It
With the development of industrial automation in the packaging field, it has a great impact on traditional packaging forms. This time we will discuss the application and performance characteristics of heavy-duty packaging bags. Heavy-duty packaging bags generally refer to polyethylene bags of 20kg or more, and the most common packaging is 25kg resin raw materials. Due to the heavy weight of the packaging, there are high requirements for the performance of the polyethylene film. The thickness of the film is in a wide range, possibly 130-180 microns, depending on the choice of material. The use of higher strength metallocene materials can be made thinner. In addition, the development of multilayer extrusion technology, such as the 5-layer structure, will further improve the performance of the film. The die head of the blown film machine for heavy packaging bags is 180 mm, which is relatively small, so it is a challenge to the multilayer extrusion technology. Impact performance In the process of transportation and unloading, the bag will inevitably experience falling or being dropped, which requires high impact resistance and withstands huge impact force instantly. Usually laboratory tests are measured by the impact strength of falling darts. Generally speaking, the higher the
Shanghai Duxia Industry and Trade Co., Ltd. will unify the calculation methods of some common blown film terms and formulas such as die temperature control, blow-up ratio, corona and other principles in the blown film process, for new entry into blown film Friends in the industry refer to this as an introductory knowledge. 1. Temperature control of extruder and die head The temperature control of the extruder and die head has a certain relationship according to the different blown film machines and the principle of the melt index and density of the particles. The data parameters provided below are only shown as examples, and the actual temperature control requires specific analysis. Hump temperature control. Temperature setting: 150℃, 160℃, 175℃, 175℃, 165℃. Linear control. The temperature of each section is set between 170-180℃. If the temperature is too high, the film will become brittle, the longitudinal tensile strength will decrease, there will be periodic fluctuations in the transverse direction, and film instability may occur; if it is too low, the extrusion will be difficult. 2. Inflation ratio (a) and traction ratio (b) The blow-up ratio is the ratio of
Whether the film thickness is uniform is an important indicator for testing the quality of film products. Uneven film not only affects the tensile strength and barrier properties of the film, but also causes cracks on the roll surface after the film is curled, and the film at the cracks The formation of permanent deformation will also affect the subsequent processing of the film, such as uneven film surface, slack and sagging of the film, which will further affect the subsequent lamination, printing, aluminizing, bag making, etc., resulting in changes in the uniformity of the cast film thickness and equipment, Materials and processes are all related. 1. The cause of equipment The molding process of cast film is that the resin raw material is melted and plasticized by an extruder, and then extruded from the die through the slit of the flat die. Under the action of the fixed edge, air knife, and vacuum box device, the melt is tightly attached to On the casting roll (also known as the quench roll), the melt is stretched and cooled in the longitudinal direction under the traction and cooling of the casting roll to form a film. After
HDPE, LDPE, LLDPE are plastic particles commonly used in blown films. Today we mainly introduce LDPE to you. LDPE is a low-density polyethylene, which is obtained by catalyzing the polymerization of ethylene monomer by a free radical initiator and does not contain other comonomers. The characteristic of its molecule is that the degree of branching is quite high, and it has a large number of long branched chains. Due to the entanglement of the molecular chains, it has poor toughness, cannot be stretched by a large proportion, and has low impact resistance. At the same time, due to its high degree of branching, it has high melt strength, which plays a considerable role in stabilizing the bubble. Because the molecule is unwound during the shearing process, it has obvious shear thinning characteristics, and the melt viscosity is greatly reduced during high shear, which brings good extrusion processing performance, which is lower Melt pressure, lower melt temperature and motor load. Due to the above characteristics of LDPE, it can be used flexibly in the design of blown film formulations in order to achieve the required performance. There are mainly the following aspects: 1. Improve processing
In the plastic film bag making process, heat sealing temperature, heat sealing pressure and heat sealing time are the three main process parameters of bag making. On the bag making machine, the heat sealing temperature is directly displayed by the thermometer, the heat sealing time can be indirectly calculated by means of the bag making speed and heat sealing ratio, and the heat sealing pressure is mainly evaluated by the operator’s experience. On the bag making machine, these three parameters are mutually restricted and affect each other. Under the premise of constant pressure, when the bag-making processing speed is increased, the heat sealing temperature must be increased accordingly. Under the premise of constant speed, when the heat-sealing pressure is increased, the heat-sealing temperature should be reduced accordingly; when the heat-sealing ratio is increased, it means that the heat-sealing time is prolonged, and the heat-sealing temperature should be reduced accordingly; The gap between the bolts means that the heat-sealing pressure is increasing and the heat-sealing time is prolonged. Therefore, the heat-sealing temperature should be reduced accordingly! In other words, accelerating the bag making speed will shorten the heat sealing
As we all know, the development and application of agricultural film technology is inseparable from “users”, “producers” and “equipment providers”. The producers of agricultural film have always played an important role in the whole process. On the one hand, in order to expand market share, try to provide downstream users with high-quality and multi-variety products; on the other hand, in order to pursue competitiveness, equipment is required The provider provides high-tech production equipment. In recent years, with the continuous development of product application fields and the intensification of market competition, this relationship is also quietly changing. Users, equipment providers, and producers are no longer just a unilateral trading relationship. It is a relationship of mutual cooperation and common development. The user’s needs are directly fed back to the equipment provider, or the equipment provider directly obtains the information needed to produce the equipment from the user. For example, in recent years, the development and application of multifunctional films such as PO coating films and photo-ecological films. Only through close cooperation between the three, not only can the equipment be stable and reliable, and the scope of application can be wide, but the product development cycle is greatly shortened.
Heavy-duty packaging bags generally refer to polyethylene bags with a weight of 20kg or more, and the most common package is 25kg resin raw materials. Due to the heavy weight of the packaging, there are high requirements on the performance of the polyethylene film. The thickness of the film has a wide range, which may be 130-180 microns, mainly depending on the choice of material. It can be made thinner by using stronger metallocene materials. In addition, the development of multi-layer extrusion technology, such as the 5-layer structure, will further improve the performance of the film. The die head of the blown film machine for heavy packaging bags is 180 mm, which is relatively small, so it is a challenge to the multilayer extrusion technology. Impact performance of heavy bags In the process of transportation and unloading, the bag will inevitably experience falling or being dropped, which requires high impact resistance and can withstand huge impact in an instant. Usually the laboratory test is measured by the impact strength of the falling dart. Generally speaking, the higher the impact strength of the falling dart, the better its drop resistance. But it is not entirely correct, because the
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