Research Of The Screw Assemble And The Processing Technics For Glass-fiber Reinfoced Modification

Glass fiber (GF) reinforced thermoplastic plastic is a kind ofcost-effective composite with high strength and light weight characteristics.This composite has been used widely in many industrial applications, and alsohas an enormous development space and a bright future. The fiber content,residual fiber length, fiber dispersion state, and interface bonding strengthbetween fiber and polymer play a very important role in improving products'properties. These factors are depending on the system component ratio, theprocessing equipments and the processing techniques. This research includesthree aspects: the system formula, the screw assemblies and the processingtechniques. Two reinforcing systems were used as following: glass fiberreinforced polyamide-66(PA66) and glass fiber reinforced polyphenyleneoxide (PPO). The effect of each factor on the residual fiber length, fiberdispersion in the matrix, and mechanical properties of the composite werestudied.1. The effect of the fiber content on the residual fiber length and themechanical properties of the composite was studied, and the optimal mass fractions of glass fiber for the two systems were determined:30%for PA66system,20~23%for PPO system. The reasonable flexibilizers for each systemand its best adding percent were determined: the POE-g-MAH was used forGF/PA66system,and the ratio of POE-g-MAH and PA66was1:6; the highimpact polystyrene (HIPS) was used for GF/PPO system,and the ratio ofHIPS and PPO was55:45. The thesis also studied the effect of thecompatilizer on the interface between fiber and matrix, and the mechanicalproperties of the composite: Maleic anhydride grafted polypropylene(PP-g-MAH) was chosen for GF/PA66system and the maleic anhydridegrafted polyphenylene oxide (PPO-g-MAH) for GF/PPO system. The dateshowed that using the compatilizer could effectively improve the interfacebonding strength and the mechanical properties.2. In this thesis, different screw assemblies for the screw mixing zone weredesigned to study the effect of screw configurations on the residual fiberlength, the fiber dispersion in the matrix, and the mechanical properties of thecomposite. The change rules of the fiber length and length distribution in theextruding direction were studied by sampling along the screw axis. The resultsshowed that decreasing the shear strength of the screw configuration properlyafter the GF adding could increase the fiber length to a certain extent.However, it would not good for the fiber dispersion in the matrix if the shearstrength was too weak; the reverse combing mixer elements ZME could offernot only a strong distributive mixing ability, but also a relatively weak shear strength, which was conducive to increasing the fiber length, and good forfiber dispersion and materials mixing; arranging the mixing elementsseparately and separating every two of them with conveying elements couldimprove the delivery capacity and conduce to keep the fiber length. Thechanging rules of the fiber length and the length distribution along the screwwere also found: the glass fibers were chopped and scattered after they wereadding to the extruder. Along the screw axis, the fiber length graduallyreduced and the length distribution gradually turned to be narrow; the fiberlength and the length distribution index decreased greater when GF goingthrough the shearing and mixing elements.3. In this paper,the processing techniques and the process parameters werealso studied. The experiments showed that changing the feeding speed and thescrew speed was the general method to control the fiber content. The effect ofprocessing temperature on the residual fiber length and the mechanicalproperties of the composite was also studied, and the optimal processingtemperatures were determined: the optimum temperature was275℃for bothsystems. The effect of different technological conditions was also analyzed.The dates showed that the worse exhausting condition would cause thereduction of the mechanical properties; preheating the fiber before adding tothe extruder would get the better soaking effect and the longer fiber length, sothat the mechanical properties would be improved.4. The differences and similarities between the two systems were studied by analyzing the experimental dates. It was showed that for the matrix withhigher viscosity, the optimal fiber content was lower,the residual fiber lengthwas shorter,and the fiber dispersion condition was worse.