You must read a lot about the car lightweight, long fiberglass and PP and nylon ye, and who launched the new glass fiber products and articles. Monotonously stressed 'why use? How to use? Where? "No one mentioned the most primitive things - how to prepare these materials? Xiao Bian finished just feel 'the body was emptied', the car on the use of those parts of plastic, but also how the hype To talk about
So, Xiaobian today and we talk about how to ensure that the equipment and technology in the resin matrix in the effective length of the matrix? As for how to apply, for what products are all words. Borrow all comics people like to say In a word, that is 'return to the original, do not forget the original heart'!
First, the best length of glass fiber in the resin matrix
Glass fiber in the resin matrix length is too short, only play the role of filler, can not enhance the role (like a few hundred dollars a ton of CaCO3 the same effect, loss of you); too long, although the enhanced effect Significant, but the impact of glass fiber in the resin matrix dispersion, molding processing performance and product performance.
Therefore, it is generally believed that the desired length of the glass fiber in the matrix of the thermoplastic tree should be five times its critical length The critical length refers to the stress value of the glass fiber in the fiber reinforced thermoplastic for a given diameter reaching its impact fracture The minimum length required. Popular is that you go to the mall to buy pants, pants length is generally not just to the ankle, but a few centimeters long, to prevent shrinking overnight into a pants is a concept. As the saying goes, 'do not advance less'.
Comparison of Performance of Long / Short Glass Fiber Modified
Because in the glass fiber reinforced plastic, the length of the glass fiber can only reach a certain length in order to pass the stress, play a role in enhancing the material, otherwise it is high-grade CaCO3. But not like martial arts novels like 'inch long, one inch', but one The optimum length. In addition, even if the best length value is found, it can not guarantee 100% of the effective length of the glass in the product because the processed equipment and process have a significant effect on the final effective length of the glass For example, the next Xiaobian told everyone how to ensure that the effective length of the glass in the equipment and technology.
Second, the impact of glass fiber in the effective length of the factors in the plastic
1, equipment factors
(1) screw configuration and barrel configuration
The general objectives of the twin-screw configuration and barrel configuration for the preparation of fiberglass are: (1) to prevent the degradation of the matrix resin, so that the glass fiber can be uniformly dispersed in the matrix resin; (2) to ensure that each fiber is the largest polymer melt The degree of wetting; ③ cut the fiber to the best length to ensure that the mixture to achieve the greatest enhancement effect; ④ extrusion process of volatile matter can row clean.
⑴ glass fiber into the screw configuration: glass fiber into the groove should be used in a large lead, so that the polymer filled with grooves to flow out enough space to accommodate fiberglass.In addition, in order to avoid the mouth of the polymer blocked , The short glass fiber is introduced into the original thread, and the long glass fiber can be imported with at least one pair of kneading discs.
⑵ glass fiber cutting and dispersion:
① glass fiber inlet downstream of the screw configuration should be conducive to the growth of fiber length and homogenization.With long glass fiber is no head, after adding the screw must be cut into a certain length and mix well with the melt, the mixing section should be Mixed by the original composition of the composition, or thin kneading plate, tooth-shaped mixed original.
② short glass fiber, mainly by the polymer melt to wet the fiber and dispersed, so the mixing section may have a thin kneading disc composed of kneading block or in the corrugated slotted original thread or tooth plate original composition.
③ high viscosity polymer or high glass fiber content (> 40%) of the screw configuration than the low viscosity polymer or glass fiber content of the screw configuration to provide a slight degree of shear to ensure that the glass will not be excessive break The
(2) the setting of the exhaust section
Because some of the glass fiber is pretreated, such as long glass fiber in the twisted fiber is treated by paraffin emulsion impregnating agent, and untwisted fiber is treated with a reinforcing agent. At a certain temperature, the glass fiber is After the melt is mixed, the impregnating agent and the reinforcing agent on the glass fiber are changed into the hair component after the high temperature, and the exhaust section should be excluded.The exhaust section should be located downstream of the glass fiber inlet, In the upstream of the exhaust section, the original sealing screw should be provided to prevent the particles from being pumped out under vacuum pump, such as reverse thread original or reverse kneading block.
(3) the last section of the screw (homogenization and pressure section)
In order to make the mixture extruded die granulation, a small lead should be used to feed the original thread in order to establish the extrusion pressure. In the exhaust port and the last section of the screw, sometimes set the original plate, the fiber were To ensure uniform distribution of glass.
2, process factors
(1) the addition of glass fiber
The addition of long glass fiber and short glass fiber uses a different method.
① short glass fiber is generally added by metering device, but when the length of the chopped glass is greater than 6mm, can be used vibration metering device, the polymer and fiberglass premix together, otherwise it will cause the separation of fiber and resin In order to increase the production, the side feeding device can be added by the side feeding port.
② long glass is easier to join, do not need special feeding device, as long as the hanging up the long glass fiber into the twin screw feeding port can be.
(2) where the glass fiber is added
In general, the polymer is added at the first (main) feed port and, after its melting, the glass fiber is added at the downstream feed port, i.e., the subsequent feed is used. Since the subsequent addition, the glass is added to the molten polymer In the material, the melt and fiber mixed, the fiber wrapped up, play a protective role in lubricating to reduce the fiber and resin mixing process of excessive break, is conducive to the dispersion of glass in the melt and distribution.
summary: Xiaobian cited these factors is only part of the more critical factors in the glass fiber modification, especially long glass fiber modified plastic process, the impact of the effective length of glass fiber a lot of factors, so the final product performance from the Feedback, technology, equipment and recipe is appropriate. Technology is always boring, but do a line, love a line, have fun!