Study on the Performance of Continuous Glass Fiber Mat

 

Most domestic insulation felt boards are made of chopped glass fiber mats coated with unsaturated polyester to form a cured sheet, which is then made by molding or lamination. The entire production process is inefficient, and the chopped mats are prone to displacement during the pressing process, which affects the profile production rate. The continuous glass fiber mats produced by the domestic two-step method are not resistant to solvents and cannot enter the glue tank. They are not suitable for the impregnation process and can only be molded into boards using a process similar to hand lay-up.

 

The continuous glass fiber mats produced by the one-step method use solvent-resistant binders to ensure that the Continuous Mats pass through the glue tank smoothly. However, there are few reports on the use of continuous glass fiber mats impregnated with resin to prepare insulation profiles at home and abroad. This study uses a pultrusion process to prepare continuous glass fiber mat (CFM) reinforced unsaturated polyester (UP) insulation (CMF/UP) profiles, and studies the effect of the binder content of continuous glass fiber mats on the performance of CFM/UP profiles, providing a reference for insulation material manufacturers to produce felt boards.

 

Sample Preparation

Unsaturated polyester resin, initiator, release agent and modified aluminum hydroxide were added to the mixing tank in a certain mass ratio, and stirred at a speed of 100 r/min for 15 min to make the materials fully dispersed.

 

The resin mixture was placed in the rubber tank, and the continuous glass fiber mat was arranged according to the predetermined layer design and impregnated with resin. The CMF/UP profile with a size of 300 mm×5 mm was prepared using the Nanjing Haoli HLYLJ-25T FRP profile pulling equipment. The three-stage mold temperature was set to 140, 160, and 150℃ respectively, and the pulling rate was about 200 mm/min. The standard test specimens were processed using the Nantong Precision Instrument HF-1224CNC milling machine.

 

Results and Discussion

Effect of glass fiber content on mechanical properties of CFM/UP profiles

Figures 1 to 3 show the effect of glass fiber content on tensile strength, flexural strength and impact strength of CFM/UP profiles. As can be seen from Figures 1 to 3, the transverse and longitudinal mechanical properties of CFM/UP profiles increase with the increase of glass fiber content.

Figure 1 Effect of glass fiber content on tensile strength of CFM/UP profiles

 

Figure 2 Effect of glass fiber content on flexural strength of CFM/UP profiles

 

 

Figure 3 Effect of glass fiber content on impact strength of CFM/UP profiles

 

Effect of glass fiber content on the compactness of CFM/UP profiles

Figure 4 shows the cross-sectional morphology of CFM/UP profiles with different glass fiber contents. As can be seen from Figure 4, when 38% glass fiber is filled (7 layers of Continuous Mat), obvious cavities can be seen in the profile; when 40% glass fiber is filled (8 layers of Continuous Mat), there are small defects in the cross section; when 43% (9 layers of mat) and 46% (10 layers of mat) glass fiber are filled, no defects are seen in the cross section, and the interior of the CFM/UP profile is basically dense.

 

Figure 4 Cross-sectional morphology of CFM/UP profiles with different glass fiber contents

 

Effect of binder content on the bending strength of CFM/UP profiles

Continuous felt with a gram weight of 450 g/m2 was filled with unsaturated polyester resin and the mass fraction of glass fiber was 46% to prepare CFM/UP profiles. The effects of the binder content and temperature of the continuous felt on the bending strength of the CFM/UP profiles were investigated. The results are shown in Figure 5. As can be seen from Figure 5, at room temperature, the bending strength of the CFM/UP profile increases with the increase of the binder content. This is because at room temperature, the increase in the tensile breaking strength of the continuous felt plays a role in enhancing the rigidity of the bending strength of the profile.

 

 

Figure 5 Effect of binder content and temperature on bending strength of CFM/UP profile

 

Performance test of CFM/UP profile

CFM/UP profile with a binder mass fraction of 5% and a glass fiber mass fraction of 46% was selected for mechanical and electrical performance testing, and compared with the performance data of UPGM203 grade in GB/T 1303.7-2009, as shown in Table 1. As can be seen from Table 1, the mechanical and electrical performance data of CFM/UP profiles meet the requirements of GB/T 1303.7-2009, indicating that the continuous felt reinforced unsaturated polyester profile produced by pultrusion is suitable for use as electrical insulation material.

 

Conclusions

The mechanical properties of CFM/UP profiles increase with the increase of glass fiber content. When the fiber filling mass fraction is 46% and the binder mass fraction is 5%, the bending strength of CFM/UP profiles is the best. The mechanical and electrical properties of CFM/UP profiles meet the requirements of GB/T 1303.7-2009.