Physicochemical properties of aerosol insecticides

According to the test methods in GB/T14449-1993, a comprehensive test was conducted on the product's storage resistance, leakage rate, droplet diameter and distribution, spray range and angle, and spray rate.

1. Container Storage Resistance and Leakage Rate: The contents of the aerosol can corrode the can, sealing cup, inner wall coating, sealing gasket, and valve. Corrosion often occurs inside the can, reducing the container's storage resistance and increasing leakage. This corrosion is exacerbated, especially in summer due to ambient temperature.

2. Droplet Diameter and Distribution: The droplet diameter is determined by factors such as the metering orifice size, actuator, nozzle structure and orifice size, and the ratio of pesticide to propellant. Droplet diameter and distribution are among the most important factors affecting aerosol product quality. In still indoor air, droplet diameter and distribution are closely related to insecticidal efficacy. Smaller droplets have better suspension and movement properties, resulting in a longer residence time in the air and better deposition and impact on the insect's surface. Generally, insecticidal aerosols with a droplet diameter between 30μm and 35μm are most effective. These droplets combine impact and residual effect, providing the best knockdown and lethality against flying pests. Droplets smaller than 0.5μm are ineffective because the droplets are too small and may simply drift past the insects without taking effect. For residual insecticidal aerosols, such as those used to kill ants and cockroaches, the droplet diameter should be between 50μm and 80μm to reduce droplet dispersion and evaporation. Uniform droplet distribution increases the chance of contact with pests and maximizes the effectiveness of the insecticidal active ingredient.

3. Spray Length and Angle: Spray length and angle are the main factors determining the spray pattern characteristics. Spray length is determined by nozzle orifice size, pressure, and propellant, while spray angle is determined by the internal orifice structure of the nozzle, such as straight-through orifices, reverse cone orifices, forward cone orifices, etc. Choosing the optimal spray pattern is crucial for aerosol sprays; too short a spray distance or too small a spray angle will affect the insecticidal effect.

4. Spray Rate: The spray rate is determined by the actuator nozzle orifice, valve core metering orifice, valve body gas phase bypass orifice, and valve body tail end orifice. For commonly used weakly flammable liquefied petroleum gas, the standard aerosol spray rate should be between 0.4 g/s and 0.5 g/s (25°C). An excessively high spray rate results in wasted pesticide solution, while an excessively low rate reduces the biological effectiveness.