Properties of PBT-GF30 Material

The part considered in the research was of the housing type, being produced from PBT-GF30 material (70% polybutylene terephthalate +30% fiberglass). This material was produced by Shanghai Langqi Plastic Materials Co., Shanghai, China, under the trade name DSM Arnite^® TV4 261. This part was obtained by injection molding, and the following technological parameters were taken into account: mold temperature (85 °C); melt temperature (223 °C), injection pressure (125 MPa); residence time (6.5 min).

PBT-GF30 is a thermoplastic, semi-crystalline plastic of the polyester family, which crystallizes very slowly and is, therefore, in an amorphous-transparent or crystalline-opaque state, depending on the processing method. It is distinguished by its high strength, rigidity and dimensional stability under heat, as well as by its very high dimensional stability and low creep. In addition, PBT exhibits, like polyesters in general, very good friction and wear properties. Unlike PET, PBT has better impact resistance, especially in cold temperatures. The properties of PBT-GF30 are optimized in different areas compared to PBT. The properties of PBT-GF30 are as follows: high strength and rigidity; dimensional stability; low creep; very good friction and wear resistance; good impact resistance; very low thermal expansion; good chemical resistance to acids; very good electrical properties; very low water absorption; and being easy to bond and weld.

Regarding the distribution of the fiber length in such a composite material, this can be established by considering the weighted average fiber length (L_w):

It was found that the weighted average fiber length (L_w) for the raw material equals 327 μm, with an average length of 254 μm and a median length of 233 μm. The properties of the PBT-GF30 composite are presented in Table 1.

Properties of the PBT-GF30.

From the PBT-GF30 material, we produced a carcass-type part that had large variations in section and that had to behave very well under shear stresses. This type of stress was considered because it was applied to the part during use, at a force that caused shear stresses in the material from which it was produced. A sketch of this type of part is shown in Figure 1.

Shape and dimensions of the housing part. Optimized geometric parameters: R-radius of connection between the walls of the part; α—the angle of inclination of the part’s walls; K = S1/S—the ratio between the thickness of the part’s walls.