The design of fast-drying and high-performance polycyanate curing agents has an effect on the performance of adipose polycyclic coatings

The 100% solid or VERY low VOC adipose polysaccharina coating system is widely concerned by its high reactivity, which makes it widely used, and can be filmed in low temperature and high humidity environments and has a relatively wide application window. However, depending on the scenario, these systems may need to be improved for their viscosity (for 100% solid-containing systems) and mixed life. This paper explains how to achieve the above goal with the help of suitable polycyanate structure. Special emphasis will be placed on the importance of a specific dual-function isocyanate polymer and how this material will improve the overall performance of the protective coating.
Introduction
In the late 1980s, polydonate resins were introduced as active thinners to increase the steroid content of polyols in two-part high-solid polysorbent coatings. Over the past two decades, these systems have gained widespread attention in different applications because of their unique characteristics. In conjunction with adipose polycyanate, these systems can be used to design fast-dry coating formulations with high film thickness (up to 300 m dry film thickness) and low VOC or even zero VOC, mainly for flooring and other protective applications. Its high film thickness and fast curing can greatly improve the construction efficiency (fewer coating channels) and shorten the shipping cycle.
industry is very interested in such systems, many resin manufacturers have provided this poly-winter arginate resin. Recently, alternative products such as polycarbonate resins have also been introduced into the polyurethane coating market.
Typical adipose polycycline systems are based on a 100% solid system of beramine and midazolam and react extremely fast, and their gel time is only a few seconds, as they react very highly with the isocyanate cells of pre-polyester. A two-tank spray system is required to obtain dry film thickness of several millimeters using these systems.
reactions between serotonin and hydroxyl/isocyanate, the amine-based/isocyanate reacts very quickly, does not require any catalyst to accelerate curing, and can be cured at very low temperatures. Due to the spatial resistance effect of the mid-amine group used, polycytone resin is much less responsitive than traditional polycyanate group. The obstruction formed by the mid-amine-based group in the resin structure controls the reaction activity between the reaction pair and the isocyanate-based group, so that the resin with different reaction activity can be designed. However, these coating systems cure significantly faster than traditional catalytic adipose bi-component polyurethane systems. Ambient humidity can be used as a catalyst for the reaction between polytinol and isocyanate, and can accelerate the post-curing effect of the paint film.
the low viscosity bit resistance amino, can be formulated with low VOC or zero VOC coating formula. Depending on the formulation, these systems can be coated by traditional application techniques such as spraying, roller coating or brushing. Typically, these coating systems can be cross-linked to conventional lipid HDI or IPDI polycyanate crosslinkers.
the application and final performance of the coating formulation is adjustable. There are two ways, one is through the selection of bit-resistive resin, and the other is through the cross-linking polycyanate structure. The regulation of the amine resin system basically determines its reactivity. In this study, we used two different polycyclycline resins that have different reactions to isocyanate. The performance of the membrane produced by it has been studied by different lipid (poly) isocyanate structures.
test
raw materials and preparations
the raw materials used in this study (polycyanate and polycyndysteine resins) are described in Tables 1 and 2 respectively. Tolonate ™ X FLO 100 is a local bio-based, very low viscosity fatty HDI-based polymer. In our study, it was used as a "reactive thinner" in other conventional diocetam or trimer polycyanates.
these resins, the ratio of isocyanate root NCO to amine-based NH is set to 1.0 to study the rheumine properties of the system. Table 3 describes the protective white paint preparation (A) used in this study. Tolonate HDT-LV2 and Tolonate X FLO 100 are used as crosslinkers using
(B). The solid content of isocyanate is regulated, and butyl acetate contains 70% solid content. On steel plates pre-coated with primers, the dry film spray (DFT) thickness of protective paint is approximately 60 m and the total DFT is approximately 100 m.
assessment of viscosity changes and evaluation of the mechanical properties of coating
rheumor experiments using mcR302 rheometers with 25mm board/plate geometry provided by Anton Paar. Measurements are made at temperatures of 25 and 40 degrees Celsius. The temperature is controlled by the Perseed plate and the upper Pert furnace to ensure that the temperature is evenly distributed. Airflow is controlled by dry air that flows continuously. The measurement is immediately following the mixing of the A and B parts and the filling of the measuring device, with a delay of approximately 2-3 minutes between the material mixing and filling the measuring device. The cross-linking reaction of the system and the process of gradually forming a three-dimensional coating film between polymers are monitored by a small amplitude dynamic oscillation time scanner. Multi-wavelength experiments are performed at the base frequency of 0.1rad s-1 and its harmonics (2,4,7,10,20,40,70,100,200 and 400) and are measured every 100 seconds. Determining deformation in a linear viscous elastic region (LVR) requires a constant strain amplitude of 1%.
evaluation of reaction dynamics
Over time, consumption from the reaction of isocyanate root (NCO) and amino groups can be measured by the change of isoic acid root NCO at its peak in the Fourier transformation spectrum. The Fourier transform spectrum can be observed using the ATR mode Bruker Tensor 27 FTIR spectrometer.
the mixed life evaluation
The determination of the mixed life period is determined by measuring the flow time of the DIN 4 s viscosity cup after the flow time is doubled in accordance with ISO9514.
the drying time assessment
the drying time is calculated using the Erichsen Coatmaster 509 MC drying time recorder, which measures a 150 m thick coated wet film.
evaluation of paint film adhesion
the evaluation of paint film adhesion is based on ISO2409 standard, the use of a cross-section method to test the adhesion of the paint.
coating film stress assessment
paint film stress assessment, is in the 2A typeLENETA card (254×140mm) with 150 m coating film around the length of the rod 220mm paint film (in the black and white card area). The coating film is evaluated for film drying and storage under controlled standard conditions of 23 degrees C and 50% r.h, and is evaluated by the bending/curvature of the card. The bending radius R can be measured directly, or the curvature radius R can be derived from the distance from one end of the paint film with A length of L to the other (see Figure 1), resulting in the bending constant of the paint film.
coating film flexibility assessment
paint film flexibility assessment, is in accordance with ASTM D522 standards, by measuring the film in the conical shaft bending test of crack resistance to evaluate the flexibility of the paint film.
impact assessment and reverse
are assessed in accordance with ISO 6272.
chemical resistance assessment
is evaluated by the substances listed in Table 4 through the ASTM D 1308 standard coverage point test. The chemical point test has an evaluation rating of 0-5. 0 represents no change in the paint film, 5 represents the paint film has been destroyed.
UV stability assessment
the coating system is tested in the UVB-313 test cycle in accordance with the accelerated ASTM G53 standard UV stability test.
corrosion resistance assessment
the corrosion resistance of the coating system during the 28-day salt spray test cycle, according to ASTM B 117.
contact angle measurement
the contact angle between the membrane of the polydonate resin-based crosslinking system and the softened water to determine the surface pressure of the polymer film.
results and discussion of the effects of
reactive thinners on viscosity and cross-linking dynamics
Tolonate X FLO 100 is much lower than normal HDI-based polycycyanate viscosity, which is reduced in viscosity due to increased reactive dilution doses.
more interesting is the effect of polycyanate compositions on the viscosity of the mixture formed by resinSA and polycyanate B (Figure 2), as well as the dynamic reaction of the system A-B (Figure 3).
the reaction system is mixed with A-B, the viscosity of the reaction system increases rapidly and develops exponentially over time (see Figure 4). As a result, the initial viscosity of the mixture cannot be properly measured. However, by re-using the exponential model, we can determine the viscosity of the substance at t-0, taking into account the time it takes to fill the mixed sample and open the measuring procedure. Figure 2 shows the test results of several polycycline resins and polycyanate mixtures. Depending on the target application, the decrease in viscosity of the initial mixture is already evident when the active thinner is at a weight fraction of 20% or 40%.
NCO conversion is not dependent on polycyanate compositions. This conversion is aimed at a different HDI-based isocyanate mixture, which, contrary to a specific polysephonate resin, is mixed with a fixed chemical metering ratio (NCO / NH=1).
, however, in a specific chemical measurement ratio, active thinners have an effect on the density of isocyanate ernogenic groups per unit volume in the
system (see Figure 5a). Because of the same weight and density of mixed polycyanate, its weight and density will change with the mixture ratio of HDI-based isocyanate and reactive thinners.
the average official energy of both polysephate and polycyanate. Because refrative thinners with a ernocity of close to 2 mainly contribute to chain growth, they do not lead to an increase in branch chains (its officiality≥3) (see Figure 5b).
time, the two results of mixing polycycyanate trimers with or active thinners can affect the cross-linking structure of polymer lacquer film. As shown in the figure, the chemical reaction between isocyanate group and zhongamide group will not be changed by the ratio of HDI-based isocyanate to reactive thinner. However, the density of isocyanate erythrocytes per unit volume is reduced to the average energy of polycyanate, which will affect the branching degree and the final crosslink density of the entire crosslinking network. As a result, the viscosity before the system gel point is reached will be affected, and the active period will also be affected.
of the cross-linking system will only occur if the reaction system has the ability to build an infinite network. Flory and Stockmayer 5-7 statistically consider a branch coefficient a, which describes the probability that a particular functional group of a branch cell passes through a dual-functional unit chain to another branch cell; Assuming that all functional groups containing two reactive molecular groups A and B have the same reactive effect, and that the B functional unit is a dual functional group, the branching coefficient can be written as:
, the branching coefficient becomes:
When the a critical value is reached, the infinite network (gel) is formed, at which point the critical value of a can already be calculated by Flory and Stockmayer:
where f is the function of the branch group.
This allows us to calculate the critical branch coefficient of the current system, where
where pi represents the probability that the function cluster i has already reacted, and r is the ratio of the function group A (both reactive and unresponsive) belonging to the branch unit to the total number of A groups in the mixture. r is the initial ratio of Group A to Group B in the mixture, and the relationship between probability pi is as follows: pB-rpA.
When the mixture of reactive groups is in a chemical measurement ratio (r-1), and the functional groups A and B correspond to the midamine group and isocyanate groups respectively as a function of the average functionality of different HDI trimers and active thinner mixtures. As shown in Figure 6.
In addition, as can be seen from equivalents 1 and 2, the critical conversion rate for forming a gel can be calculated as a function of the average functionality of ratio r and polycyanate blends:
In our case, the critical conversion rate required to form the gel shown in Figure 7 depends only on the average functionality of the polychyanate blend and the ratio r between the number of NCO groups as part of the branch unit and the total number of NCO groups.
based on the time dependence of the measured conversion p (Figure 3), the time required to reach the critical conversion pc required to form a gel in a particular system can be estimated (Figure 8).
it can be estimated that the active thinner in the polycyanate mixture has a potential effect on the system gel time, as shown in Figure 9.
As mentioned earlier, over time, the development of viscosity can be approximated by exponential equations in the early stages of the crosslinking process, allowing the formulator to determine the time constant based on it and then evaluate the time necessary to double the viscosity.
10 shows the increased viscosity of the active thinner in the polycyanate blend. The results show that in a very low concentration (20%) hardener system, regardless of the resin composition used, the presence of reactive thinners will have an effect on the system activity period during coating.
can monitor the aggregation of the network and the time-forming of the gel by using the method of dynamic phonology measurement. When elastic mods (G') become more important than viscous mods (G'''), the system can be considered close to its gel point. But to know the exact gel point of the system, it is possible to have the angle between the modules independent of the frequency 8. The exact gel point cannot be determined under the current circumstances, but we can guess at the intersection of G'(t) and G'(t).
has probably determined the gel point based on fast-dry polydonate resins and HDI-based polycyanate mixtures (mixtures containing or free of active thinners). As shown in Figure 11, polyseocyanate blends containing 20 wt% reactive thinners can reach gel points over time compared to those that do not contain 20 wt% reactive thinners. This measurement compares cumulative gel time with the help of Fourier and Komeier models.
a reactive thinner