The resin matrix of thermoplastic composites involves general and special engineering plastics, and PPS is a typical representative of special engineering plastics, commonly known as "plastic gold". The performance advantages include the following aspects: excellent heat resistance, good mechanical properties, corrosion resistance, and self-flammability up to UL94 V-0 level. Because PPS has the above performance advantages, and compared with other high-performance thermoplastic engineering plastics, it has the characteristics of easy processing and low cost, so it has become an excellent resin matrix for manufacturing composite materials.

PPS plus short glass fiber (SGF) composite material has the advantages of high strength, high heat resistance, flame retardant, easy processing, low cost, etc. .

PPS lengthened glass fiber (LGF) composite material has the advantages of high toughness, low warpage, fatigue resistance, good product appearance, etc. It can be used for impellers, pump casings, joints, valves, chemical pump impellers and casings, cooling water impellers and Shells, home appliance parts, etc.

So what are the specific differences in the properties of short glass fiber (SGF) and long glass fiber (LGF) reinforced PPS composites?

In this paper, the comprehensive properties of PPS/SGF (short glass fiber) composites and PPS/LGF (long glass fiber) composites are compared. Among them, PPS/LGF composites are prepared by melt impregnation process and PPS/SGF composites are prepared by melt blending. The reason for adopting the melt impregnation process in the twin-screw granulation process is to realize the impregnation of the fiber bundles in the impregnation mold without causing damage to the fibers. Finally, through the data comparison of the mechanical properties of the two, it can provide technical support for the application-side scientific and technological personnel when selecting materials.

Mechanical property analysis

The reinforcing fibers added in the resin matrix can form a supporting skeleton. When the composite material is subjected to external force, the reinforcing fibers can effectively bear the role of external loads; at the same time, it can absorb energy through fracture, deformation, etc., and improve the mechanical properties of the resin. The graphs below show the tensile and flexural properties of PPS/SGF and PPS/LGF composites with different glass fiber contents, respectively.

It can be seen that the tensile strength and flexural strength of the composite material are gradually increased by increasing the amount of glass fiber added. The main reason is that when the glass fiber content increases, more glass fibers in the composite material are subjected to external forces. At the same time, due to the increase in the number of glass fibers, the resin matrix between the glass fibers becomes thinner, which is more conducive to the glass fiber reinforced frame. Therefore, the increase of the glass fiber content makes the composite material more stress transferred from the resin to the glass fiber under the external load, which effectively improves the tensile and bending properties of the composite material.

The tensile and flexural properties of PPS/LGF composites are higher than those of PPS/SGF composites. When the mass fraction of glass fiber is 30%, the tensile strengths of PPS/SGF and PPS/LGF composites are 110MPa and 122MPa, respectively; The flexural strengths are 175MPa and 208MPa, respectively; the flexural elastic moduli are 8GPa and 9GPa, respectively.

The tensile strength, flexural strength and flexural elastic modulus of the PPS/LGF composites were increased by 11.0%, 18.9% and 11.3%, respectively, compared with the PPS/SGF composites. The length retention rate of glass fiber in the PPS/LGF composite material is higher. Under the same glass fiber content, the composite material has stronger load resistance and better mechanical properties.

It can be seen that when the glass fiber content is low, the impact strength of the composite material decreases. Defects exist in the form of a decrease in the overall impact strength of the composite.

The above-mentioned defects refer to the tip of the glass fiber or the tip of the crack; the failure induction point of the thermoplastic composite material is the tip of the glass fiber or the tip of the crack, and from this point it spreads until the composite material is completely destroyed. When the glass fiber content is small, the glass fiber tip is added to the composite material. At this time, because the effect of the glass fiber tip on the fracture of the composite material is greater than the effect of the glass fiber reinforcement, the impact performance will decrease to a certain extent.

With the increase of glass fiber content, the glass fiber in the composite material can form an effective spatial network, and the reinforcing effect is greater than that of the glass fiber tip. The overall performance of the material, while in the PPS/LGF system, the length of the glass fiber is longer, the space network is denser, the bearing capacity of the reinforced glass fiber is stronger, and its impact strength is also better. When the glass fiber mass fraction is 30%, the impact strength of PPS/LGF is 19.4% higher than that of PPS/SGF, from 31kJ/m2 to 37kJ/m2, and the notched impact strength is increased by 54.5% (from 7.7kJ/m2 to 11.9kJ/m2 ).

Thermal Properties Analysis of PPS/SGF and PPS/LGF Composites

The results show that the introduction of glass fiber greatly improves the heat resistance of the composites. When the mass fraction of glass fiber is 30%, the thermal deformation temperatures of PPS/SGF composites and PPS/LGF composites reach 250 °C and 275 °C, respectively. , the thermal deformation temperature of PPS/LGF composites is 10% higher than that of PPS/SGF composites. The main reason is that the introduction of glass fiber forms a network skeleton of reinforcing fibers inside the composite material, which greatly improves the heat resistance of the composite material. The glass fiber size in PPS/LGF is longer, and the advantage of improving heat resistance is more obvious.

Section Analysis of PPS/SGF and PPS/LGF Composites

It can be seen that the glass fiber is better dispersed in the resin, and with the increase of the glass fiber content, the construction of the reinforcing fiber network inside the composite material is more perfect; this is also the main reason why the overall mechanical properties of the composite material increase with the increase of the glass fiber content. Compared with PPS/SGF and PPS/LGF composites, the glass fiber retention rate in PPS/LGF composites is higher, which is the main reason for the better mechanical properties of PPS/LGF composites.

In conclusion, the tensile strength, flexural strength, flexural modulus of elasticity, notched impact strength and unnotched impact strength of PPS/LGF composites are all higher than those of PPS/SGF composites. The thermal deformation temperature of the 30% glass fiber reinforced PPS/SGF composite reaches 250℃, and the thermal deformation temperature of the PPS/LGF composite reaches 275℃.

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