Preparation And Performance Of Continuous Glass Fiber Reinforced Polypropylene Composites

The glass fiber reinforced thermoplastic composites have not only excellent mechanical property and good recyclability,but also the prominent competitive advantage of low price.Thus,the glass fiber reinforced thermoplastic composites have become an indispensable basic supporting material in production and life.Among the glass fiber reinforced thermoplastic composites,unidirectional continuous glass fiber reinforced polypropylene prepreg tapes possess the strongest mechanical properties because the glass fibers consist in a continuous form and are arranged parallelly to each other.Therefore,the unidirectional prepreg tapes as a semi-finished composite have showed the best development potential and are widely used in automotive panel,airplane floor and high-strength pipeline.At present,the unidirectional continuous glass fiber reinforced polypropylene prepreg tapes are basically produced by melt impregnation technology at home and abroad.This technology not only accurately controls the glass fiber content of the composites,but also has a short molding cycle and enables large-scale continuous production.However,the characteristics of high viscosity and low liquidity for the polypropylene melt result in the poor impregnation of glass fiber,and even the poor compatibility between resin and glass fiber,which limit the widespread application of the unidirectional prepreg tapes.Based on the above problems,2,5-dimethy 1-2,5-bis(tetra-butyl-peroxy)hexane embedded polypropylene named MB-CR PP(Peroxide Master Batch-Controlled Rheology PP)was selected as chain scission agent to overcome the drawback of low melt flow and high viscosity of polypropylene melt.On the other hand,on the basis of the traditional technology to improve interfacial compatibility of the composite by coating glass fiber with silane coupling agent,maleic anhydride grafted polypropylene(PP-g-MAH)was selected as the compatilizer to enhance the interfacial bonding strength of composites.The experimental results showed that the glass fibers could be completely impregnated by the introduction of the moderate MB-CR PP to improve the liquidity of polypropylene.Besides,the introduction of PP-g-MAH could distinctly improve the interfacial bonding strength of the composites,which drastically enhanced the mechanical property of composites.This paper not only provides theoretical support for the application of unidirectional continuous glass fiber reinforced polypropylene prepreg tapes,but also offers new insight to the development of other continuous glass fiber reinforced thermoplastic composites.The main research contents are as follows:MB-CR PP was selected as the chain scission agent to prepare high fluidity polypropylene particles by the controlled rheology method.The mechanical property,flow property,molecular weight and its distribution,rheological property and crystallization property of polypropylene before and after modification were systematically measured by melt flow indexer,universal testing machine,gel permeation chromatograph,capillary rheometer and differential scanning calorimeter.The experimental results showed that molecular weight of polypropylene decreased and its distribution became narrow with the increase of MB-CR PP.Meanwhile,the fluidity of polypropylene was drastically enhanced,but the mechanical property slightly decreased.Besides,the shear stress and shear viscosity of polypropylene dramatically decreased,but its crystallinity almost had no changes with increasing MB-CR PP.Unidirectional continuous glass fiber reinforced polypropylene prepreg tapes were prepared by melt impregnation process with prepared high fluidity polypropylene and PP-g-MAH,and then the unidirectional prepreg tapes were used to obtain laminated plates by hot-pressing method.The effects of the fluidity of polypropylene,glass fiber content and thermo-oxidative aging on the morphology,mechanical property and bonding strength of the continuous glass fiber reinforced polypropylene composites were investigated.The experimental results showed that the mechanical property of the composites which were prepared with higher fluidity polypropylene modified by MB-CR PP could be improved to some extent because of the complete impregnation of glass fiber and the decrease of composite porosity.When the content of MB-CR PP in the resin system was 0.4 wt%,the mechanical properties of the composites reached the optimized status.In addition,on the basis of ensuring the complete impregnation of glass fiber,the increase of glass fiber content could improve mechanical property of the composite.When the glass fiber content exceeded 65 wt%,the resin was difficult to fully impregnate the glass fiber,and the appearance and performance of the composite were also significantly deteriorated.More importantly,the thermal aging would lead to the damage of the composite structure and the significant decrease of the mechanical property,so the long-term application of composite in high temperature environment should be avoided.PP-g-MAH with different grafting rates was used as a compatibilizer for continuous glass fiber reinforced polypropylene composites.The effects of different grafting rates of PP-g-MAH and the amount of compatibilizer on the properties of the composite were investigated.The results indicated that the interfacial bonding strength of the composite was improved distinctly through increasing the grafting ratio of maleic anhydride or the dosage of compatibilizer,and thus the mechanical property of the composite was enhanced drastically.However,the increase of grafting ratio of maleic anhydride or dosage of compatibilizer would sharply increase the cost of composite.Taken the cost and product performance into consideration,about 1%grafting ratio of maleic anhydride and about 2.5 wt%compatibilizer were selected.