Year1
- 螺杆数：
- 多螺杆
The softening of amorphous polymers is completed within a relatively wide temperature range, and equidistant gradient screws are generally used. The melting temperature range of crystalline polymers is relatively narrow, and equidistant mutation screws are generally used.
In small extruders, such as & extruder screws use a full thread type with equidistant and unequal depths. The length and diameter of the screw are relatively small, and they are mainly used to extrude small-section insulation and sheathing layers. , the extrusion speed is faster. (The screw diameter is the outer diameter of the thread. The production capacity (extrusion volume) of the extruder is approximately proportional to the square of the screw diameter. When other conditions are the same, a slight increase in the screw diameter will cause a significant increase in the extrusion volume. Its impact is even greater than the impact of the increase in screw rotation speed on the extrusion volume.
The medium-sized screw adopts a full-thread type with equidistant and gradual thread depth. Its length-to-diameter ratio is larger than that of the small screw, and the pitch of the thread is Equally, from shallow to deep starting from the root. The thread at the end of the thread is deeper and the thread at the root is shallower. In this way, more plastic is extruded without affecting the strength of the screw. The extrusion speed is fast and the plastic plasticization is good. It is a general medium The ideal screw for small extruders to produce insulating and sheathing layers.
The diameter of large screws is generally above, such as & extruders. Large screws come in two types, one is equidistant and unequal depth, such as & extrusion The second screw of the plastic machine is divided into three sections, namely equidistant and equal depth, equidistant and unequal depth, and unequal interval and unequal depth. For example, an extruder has a compression ratio between ~ and an aspect ratio between: left and right. It is mainly used Suitable for producing large-section wire and cable insulation and sheathing layers 2. The main parameters of the screw The main parameters of the screw include diameter, aspect ratio, compression ratio, pitch, screw groove width, screw groove depth, helix angle, screw and barrel These parameters have a great influence on the extrusion process and performance.
The advantage of the two-stage method is that the two phases are more evenly dispersed.
Rubber and plastic blending equipment mainly includes high-temperature open mills , internal mixer, screw extruder and continuous mixer. Continuous mixer is divided into two types: internal mixing extrusion combined type and rotor screw combined type. High temperature open mixer and internal mixer are intermittent mixing equipment. , the screw extruder and the continuous mixer are continuous mixing equipment. The continuous mixer combines the advantages of the internal mixer and the screw extruder, has high production efficiency, and will become the most important blending equipment in the future.
The driving force of mechanical blending comes from the mechanical stirring and shearing provided. Mechanical blending is a system homogenization process under the action of mechanical force. It is generally believed that the homogenization process includes the physical mixing and dispersion of each component of the system, but in fact In addition to providing energy for the mixing and dispersion of the components, the mechanical force during the mechanical blending process also triggers mechanochemical reactions between the components. This reaction has an important impact on the combined properties of rubber and plastics.
Other considerations for rubber and plastic blending:
Although we understand the miscibility principle of rubber and plastic and the method of rubber and plastic blending, according to people's practice in the field of blending for many years, rubber and plastic blending still needs to be considered The following factors:
Viscosity. Viscosity is a representation of the average molecular weight of polymer materials. The smaller the viscosity, the smaller the mixing entropy, resulting in higher dispersion uniformity and smaller micro-domain size.
Polarity. Select When rubber and plastic are used together, the traditional approach is to give priority to polymers with similar polarities and avoid using two polymers with widely different polarities. However, with the emergence of compatibilization technology, this consideration can be alleviated.
Temperature. Temperature is particularly important for rubber and plastic blending, because plastic is in a crystalline state at room temperature. Only when the temperature reaches a certain level can the crystallization be released and blending can occur. As for the specific temperature value, it depends on the variety. For example, the melting temperature of C is ℃. Only when the plastic melts can it enter a good blending state, otherwise the effect will be very poor. Compatibilization technology fills the gap
. Solubility parameter. Each polymer material has a solubility parameter that reflects its intermolecular force. When blending two polymers, the difference in solubility parameter should be as small as possible, but larger than that, because the smaller the value, the better the blending effect. If the difference is too small, there will be no two phases, and the meaning of blending will be lost.
__Copy
WhatsApp
