Research on two-component polyurethane sealant for insulating glass

Insulating glass is a new type of building material that uses two (or three) pieces of glass and a high degree of airtightness composite adhesive to bond the glass pieces to the aluminum alloy frame. It has good heat insulation, sound insulation, and a beautiful appearance.

Insulating glass units usually use double sealant, that is, polyisobutylene glue is used as the first seal, and agricultural production system silica gel, polysulfide glue, or polyurethane glue is used as the second seal. In this paper, hydroxyl-terminated liquid polybutadiene and crude MDI are used as the main raw materials to prepare a two-component polyurethane sealant for insulating glass. Fillers, plasticizers, chain extenders, adhesion promoters, catalysts for sealing, and the effect of glue performance.

^{The two-component polyurethane sealant for insulating glass 1}

Experimental raw materials: 

Hydroxyl-terminated liquid polybutadiene, Poly bd®R45V, Crayville (Guangzhou) Chemical Co., Ltd.; 

Crude MDI, WANNATE®PM-200, Wanhua Chemical Group Co., Ltd.; 

Nano calcium carbonate, WINNOFIL® SPM, SOLVAY; 

Heavy calcium carbonate, OMY-2, Omiya (Shanghai) Investment Co., Ltd.; 

Plasticizer, DIDP, ExxonMobil Chemical; 

Chain extender, 1,4-butanediol (1,4 -BDO), Shanghai Tixiai; 

Adhesion promoter, Silquest® A-187, Momentive Advanced Materials (China) Co., Ltd.; 

Catalyst, ZJPC-0225, self-made.

(1) The influence of NCO/OH ratio on the performance of insulating glass sealant: Generally speaking, the closer the NCO/OH ratio is to 1, the closer the sealant is to the gel point, the faster the reaction cross-linking speed, but too fast The speed of crosslinking will affect the operating time of the polyurethane sealant. Therefore, it is very important to select the appropriate NCO/OH ratio for two-component polyurethane insulating glass glue. Choose different NCO/OH ratios to investigate the performance of a two-component polyurethane insulating glass sealant. The results are shown in Table 1 and shown in Figure 1.

^{Table 1 The influence of NCO/OH ratio on the performance of insulating glass sealant}

^{Figure 1 The situation after the cured rubber strip is cut open}

From the results in Table 1, it can be seen that when the NCO/OH ratio is below 1.19, the pot life of the two-component polyurethane glue sample is too short; when the NCO/OH ratio is above 1.34, the operating time of the two-component polyurethane glue sample In order to meet the construction requirements, when the NCO/OH ratio reached 1.80, a certain amount of bubbling appeared in the cured rubber strip as shown in Figure 1. Therefore, the ratio of NCO/OH between 1.34 and 1.64 is more appropriate. Taking into account the proportion error of the A and B components in the actual construction process, it is more appropriate to choose the NCO/OH ratio of about 1.5.

(2) The influence of chain extender content on the mechanical properties of insulating glass sealant: In the formulation of polyurethane glue, some compounds containing active hydrogen are often added to react with isocyanate-terminated prepolymers, thereby extending the molecular chain diffusion and improving The initial strength of polyurethane glue. The effect of 1,4-BDO on the performance of two-component polyurethane insulating glass glue was studied, and the results are shown in Table 2.

^{Table 2 The influence of chain extender content on various properties of insulating glass sealant}

It can be seen from Table 2 that the addition of a small amount of 1,4-BDO can reduce the amount of R45V used, increase the tensile strength of the sealant, and reduce the surface drying time of the sealant, but at the same time, it will reduce the operating time and breakage of the sealant. Elongation. Therefore, the more suitable ratio of 1,4-BDO chain extender in this article is 0.10%.

(3) The influence of the ratio of nano calcium carbonate to heavy calcium carbonate on the performance of the sealant: Nano calcium carbonate is mainly used to improve the thixotropy, strength, and toughness of the product, but the thickening is obvious, so it can only be partially added in the product, and Heavy calcium carbonate is mainly used to reinforce and act as a filler to reduce the cost of the formulation. 

Therefore, the selection of an appropriate ratio of nanometer calcium carbonate and heavy calcium carbonate plays a key role in the overall performance of the sealant. Table 3 lists the effects of different ratios of nano-calcium carbonate and heavy calcium carbonate on the performance of two-component polyurethane insulating glass sealants. From the results in Table 3, it can be seen that when the proportion of nano calcium carbonate is 20% and the proportion of heavy calcium carbonate is 30%, the sealant has poor thixotropic properties. At the same time, the high filler content will cause the glue to resist The aging performance is not good, so the more suitable ratio of nano-calcium carbonate in this article is 25%, and the ratio of heavy calcium carbonate is 25%.

^{Table 3 The influence of the content of nano calcium carbonate and heavy calcium carbonate on the performance of the sealant}

(4) The effect of catalyst content on the pot life and surface drying time of the sealant: The results are shown in Figure 2. It can be seen from Figure 2 that the two-component polyurethane sealant has a long pot life (86 min) without adding a catalyst, but the surface drying time of the same glue is correspondingly long, reaching about 260 min. Therefore, it will greatly affect the construction efficiency on site. From the research results of this article, the more suitable catalyst ZJPC-0225 is used in 0.1%～0.2%. Taking into account the error range of the formula during actual construction, the better catalyst content in this article is 0.15%.

^{Figure 2 The influence of catalyst content on the pot life and surface drying time of sealant}

(5) The effect of the amount of adhesion promoter added on the adhesive performance of the sealant: This article studies the effect of the content of the adhesion promoter on the adhesive performance of the sealant, and the results are shown in Figure 3. It can be seen from Figure 3 that the addition of the adhesion promoter greatly improves the interface adhesion of the two-component polyurethane insulating glass sealant. When the content of A-187 reaches 10%, the two-component polyurethane sealant sample can achieve a better bonding effect. Further increasing the content of A-187 will not reduce the interface adhesion of the two-component polyurethane sealant sample, but the sample appears sticky at this time. Therefore, the better adhesion promoter content in this experiment is 10%.

^{Figure 3 The effect of the amount of adhesion promoter added on the adhesive performance of the sealant}

Through a series of experiments, it is concluded that using hydroxyl-terminated liquid polybutadiene and crude MDI as the main raw materials, the effects of fillers, plasticizers, chain extenders, adhesion promoters, and catalysts on the performance of sealants have been studied. The study found that when the NCO/OH ratio in the two-component polyurethane sealant is 1.5, the hydroxyl-terminated liquid polybutadiene R45V content in the A component is 22.4%, and the chain extender 1,4-BDO content is 0.1%. The content of DIDP is 27.6%, the content of nanometer calcium carbonate SPM is 25%, the content of heavy calcium carbonate OMY-2 is 25%, the content of catalyst ZJPC-0225 is 0.15%, and the content of crude MDI PM-200 in component B is 55%. , When the plasticizer DIDP content is 35%, and the adhesion promoter A-187 content is 10%, the prepared two-component polyurethane sealant has better comprehensive performance and can meet the requirements of the second-layer insulating glass sealant.