Study on Microwave Curing of Unsaturated Polyester Resin and Its Composites Containing Calcium Carbonate

Abstract

Microwave curing technology has been widely used in resin and its composite materials. In order to study its effect for curing unsaturated polyester resin (UPR) composites containing calcium carbonate (CaCO3) filler, this paper first investigated the influence of microwave power and microwave irradiation time on the curing characteristics of UPR. Then, CaCO3 particles were added to the UPR to investigate the microwave curing effect of the UPR composites containing the CaCO3. The results showed that microwave irradiation could heat the UPR sample evenly, and rapidly cause the chain growth reaction, thus greatly shortening the curing time. The curing degree and products of the samples after microwave curing were consistent with that of the thermal curing. The addition of CaCO3 particles could increase the heating rate of the UPR composites, which would accelerate the curing rate of the UPR. However, higher microwave power could lead to pore defects inside the UPR composites with higher CaCO3 content, resulting in a lower strength. Thus, the compactness of the samples should be improved by reducing the microwave power and prolonging the microwave treatment time.

Effect of inorganic particles gradation on the properties of high‐filled unsaturated polyester resin/CaCO3 composites

“…66 The reason is that most of the C=C of UP monomers are involved in the cross-linking reaction and styrene volatilization during the curing process of UPR. 15 As shown in Table 2, the β of the G-x-Mid (X = 1,2,3,4) increased sequentially. This result suggests that the conversion of UPR precursors can be improved as the dispersion of uncured domains decreases caused by CaCO 3 gradation optimization.…”

“…One is that the high bulk density makes the whole system trap a large amount of gas styrene, air. 15 The second reason is the low bulk density, which leads to the lack of material compactness. The results indicate that both the gradation and the bulk density of the filler affect the morphology of the high-filled UPR/CaCO 3 composites.…”

“…65 Figure 5F shows the FTIR spectra of the uncured UPR and cured G-x-Mid (X = 1,2,3,4) composites. The uncured UPR has two distinctive characteristic peaks at 992 cm À1 and 912 cm À1 due to the stretching vibrations generated by the C=C bond of UPR and styrene, 15,41 respectively. The FTIR spectra of the cured G-x-Mid (X = 1,2,3,4) are not different.…”

“…The filling amount of CaCO 3 in common composites such as filled masterbatch is 75%-85%, 14 while in artificial stone, it is as high as 80%-90%. 15 When the CaCO 3 filling amount is 50 wt% or over in UPR/CaCO 3 composites, it belongs to the highfilled composite. 16,17 However, an increase in the filler filling amount leads to an increase in the viscosity of the whole composite system, which is unfavorable to the infiltration of the resin into the filler.…”

“…21,22,29 Therefore, the gradation of inorganic fillers (e.g., CaCO 3 ) with high proportion has a huge role in improving the properties of composites, such as stiffness, dimensional stability, and heat resistance, when compared to the influence of UPR and processing properties. 15 The mechanical properties of the composites are closely related to their macroscopic defect morphology, the particle size distribution of the filler, and the contact state of the microscopic interfaces between the fillers. [30][31][32][33] The results show that the thermoplastics filled with CaCO 3 with different particle size distributions have lower melting crystallization temperature and lower melting viscosity than the composites filled with a single particle size, which improves the machining and mechanical properties of the composites significantly.…”