Long fiber reinforced polypropylene composites (LFT-PP) have good mechanical properties, as well as low temperature resistance and fatigue resistance. Compared with thermoset sheet molding compounds (SMC), LFT-PP has the advantages of repeatable processing and recycling. Compared with short fiber reinforced polypropylene composites (SGFPP), LFT-PP has higher strength and toughness. Compared with fiber mat reinforced polypropylene composite (GMT-PP), it has good flow properties and is easier to be molded. LFTPP is widely used in transportation, chemical, construction and other fields, especially in the automotive industry, and is widely used to replace fiber felt (GMT).
LFT PP in-line mixing process and melt pack for LFTPP pellets Compared with the coating process production, more attention has been paid. Online mixing process Continuous rovings made of polypropylene (PP) and glass fiber (GF) Disperse GF in extruders and mix with PP to produce
LFT PP's GF length can be maintained above 10 mm, with good Mechanical properties. On-line mixing process, simple equipment, simple raw materials, low cost, flexible process, low investment, etc.
Performance Testing:
◆Tensile property: measured according to ISO527-2001, tensile modulus test speed is 2 mm / min, tensile strength test speed is 5mm / min; flexural property: according to IS0178-2001, flexural modulus test speed is 2mm / min, the test speed of bending strength is 5mm / min. Cantilever beam notched impact performance: determined according to ISO180-2000.
◆Fiber mass fraction w (GF): Test specimens were calcined in a muffle furnace at 600 ° C for 4 h.W (GF) was calculated from the mass of the splines before and after calcination and the residual fiber mass.
◆Fiber length: A 60mmx60mm rectangular plate was cut and fired in a muffle furnace at 600 ° for 4 hours, and the residual fibers were dispersed on a black plastic plate. The fiber length distribution was obtained using a semi-automatic image analysis method, and then the fiber weight average length Lw and number average were calculated. Length Ln.
In conclusion：
1) Generally the fiber length in SGF-PP is less than 0.5 mm. GMT-PP uses continuous fiber felt as a reinforcing material, in which the fiber length is considered infinite. The fiber length of LFT-PP is between 7 and 10 mm, which is between SGF-PP and GMT-PP. When the amount of fiber is low, the fiber length is basically unchanged. When the amount of fiber is high, the fiber length is reduced due to the interaction between fibers.
2) The strength performance of GFPP is closely related to the fiber length. As the fiber length increases, the strength performance increases. The tensile strength increased from SGF-PP, LFT-PP and GMT-PP in this order. Due to the interlayer defects of GMT-PP and poor impregnation of the fiber, the bending strength is reduced, which is between SGF-PP and LFT-PP.
3) The relationship between the modulus properties of GF PP and fiber length is small. The tensile modulus of SGF-PP, CMT-PP and LFTPP are not significantly different. CMT PP has lower flexural strength due to interlayer defects and poor fiber impregnation, which is lower than SGF PP and LFT-PP.
4) SGFPP has the lowest impact strength, while GMT-PP and LFT-PP have similar impact strength.
