The two-head thread can be extruded mainly, and the hea […]
The two-head thread can be extruded mainly, and the heating is uniform and short, self-cleaning performance. Good (common) • d, three-thread thread, flexible choice of material pressure and temperature distribution at the machine angle, stable fiber, good surface renewal effect, but low output. • “M” series: tooth shape, Mainly to disturb the flow, can accelerate the material to homogenize. The stronger the mixing. - But pay attention to the high shear destructiveness when using it. (Representation, such as "M80" in domestic and Taiwan, SME45/45 in "WP", ZB45/3/11 in "BERSTDRFF") 4. Screw arrangement and temperature setting of each section of the screw • 1. Physical change characteristics and temperature setting principle of plastic: • (1) Physical change characteristics of plastic: • A non-crystalline plastic • Three physical states with increasing temperature Features such as: • Highly viscous viscous flow • Tg Tf Td • (Glass temperature) (melting temperature) (decomposition temperature) • Its melting is carried out under shear flow causing viscous dissipation • B crystalline plastic, • with The temperature rises gradually with two physical properties, and the changes are sudden, such as: • Tm Td • (melting temperature) (decomposition temperature) The melting experience: solid bed formation, cracking, formation of a large number of particles floating in the melt, After gradually melting. (2) Temperature setting principle: • The melting point of each component of the blended alloy and its ratio: based on the melting point of the blending component, the melting point of the continuous phase is adjusted. • 2 plastic thermal properties, such as melting endothermic exotherm, thermal degradation process and thermal oxidation is difficult. • 3 flow characteristics and morphological changes in the melting point of each component of plastic. • For example, PC/ABS (6:4), PC: melting point of about 230 degrees, decomposition point of about 350 degrees; ABS: melting point of 180~190 degrees, decomposition point of 245-290 degrees - so PC / ABS processing temperature 230- 250 degrees - taking into account other additives, such as compatibilizers, thermal stability of lubricants, etc. (3) Sources of elevated material temperature: • 1, shearing of the screw and friction between the material particles to generate heat - most . • 2, the heat transfer of the cylinder. (2) Screw arrangement and temperature setting of each section
The role of the screw combination: 1 conveying material 2 provides shearing—the energy required to obtain physical and chemical changes in the processed material to disperse and distribute the components. 3 Construction pressure • Material particle melting process analysis: • Free polymer transport and preheating – full or partially filled with solid plugs – solid friction, dissipation and solid-state “island” structure generation – solid sparse “island "Structure - molding extrusion. Screw arrangement segmentation and temperature setting: • 1. Conveying section • A. The screw arrangement ideas are: • a deep groove forward thread • b medium groove large lead forward thread, and the groove volume changes greatly Small, that is, the thread lead is gradually changed from large to small. • B, temperature setting ideas • a should not be too high, affecting the material transported and sheared in this section; should not be too low, the screw is too stressed or stuck • b is generally slightly closer to melting, arranged in a gradient. 2. Melting section • A. Screw arrangement: . The purpose of the material in this section is to: obtain the energy required for physical changes and partial chemical changes of the processed materials, so that the distribution between the components is uniform and preliminary dispersed, so that the components are homogenized and the viscosity is close.
It is generally required that the material is subjected to large shear and heat transfer of the barrel to melt it. Generally, the kneading block, the shearing element or the reverse thread are arranged, and attention is paid to the phase arrangement. • B, temperature setting • a glass fiber system, the temperature is too low, the resin is semi-melted, and the glass fiber is poorly coated in the latter stage; the temperature is too high, the resin flow is increased, the tempering and shearing action is small, and even high temperature degradation occurs. , the setting principle: • 1, according to different base materials and glass fiber content; • 2, minus the heat input from the screw shear, slightly higher than the melting point of the base material; • 3, the latter part of the melting section (ie glass fiber Add to the mouth) melt flow conditions. • b filling system, (providing strong shear to make the filler fully dispersed), the melting section is 10~20 °C higher than the melting point of the base material (as much as possible), so that the material is fully melted and evenly distributed. • c flame retardant system (protective flame retardant), the temperature is low, especially white material, as low as possible.
