Rigid polyurethane foam (RPUF) has excellent properties such as light weight, good thermal insulation, high specific strength, good vibration and sound damping, etc. Therefore, it has been widely used in the fields of building insulation, refrigerator, cold storage, etc. From the 1960s to the present, with the development of science and technology and the strengthening of human environmental awareness, the types of foaming agents for polyurethane foam have been increasing, and the common foaming agents include chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), hydrofluorocarbon (HFC), alkane (HC), water and hydrochlorofluoroolefin (HCFO).
The first generation blowing agent CFC-11 has been completely banned because it will destroy the ozone layer in the atmosphere. The second generation blowing agent HCFC-141b will still destroy the atmospheric ozone layer to a certain extent, will also face elimination, China will completely ban the use of HCFC-141b in 2030.3 The third generation blowing agent HFC, such as HFC-245fa, HFC-365mfc, etc., although it will not damage the ozone layer, but the global warming potential (GWP) is very high, as CO2 and alkanes have high thermal conductivity in the gas phase, so one of the most prominent disadvantages of water or alkane blowing agents is the poor adiabatic effect of foam products.
Trans-1-chloro-333-trifluoropropene (HCFO-1233zd(E)) is an excellent polyurethane blowing agent with zero ozone depletion value (ODP), low global warming potential (GWP), low gas-phase thermal conductivity, and non-toxic, which is recognized as one of the most promising alternatives in the industry for the fourth generation of blowing agents.
The results of thermal conductivity measurement show that the foam exhibits superior thermal insulation performance when the amount of HCFO-1233zd(E) is higher. In general, the thermal conductivity of foam is determined by the thermal conductivity of the gas inside the foam, the thermal conductivity of the bubble material, the radiative conductivity of the bubble at the bubble wall, and the convective thermal conductivity of the gas inside the bubble.
The diameter of common polyurethane foam bubble pore is negligible, while the radiation conduction coefficient of the bubble pore on the wall of the bubble pore is unavoidable and generally considered only when the density is less than 30 kg/m3, so the thermal insulation performance of the foam mainly depends on the thermal conductivity of the gas inside the foam and the thermal conductivity of the bubble pore material. m-K), which is much lower than the gas-phase thermal conductivity of carbon dioxide of 16.3 mW/(m-K). And HCFO-1233zd(E) has better compatibility with polyether polyol, excellent emulsification and nucleation performance when foaming, thus the foam pores are fine and the pore walls are thinner. At the same time,, plays a major role so the larger the amount of HCFO-1233zd(E). The smaller the thermal conductivity of the foam, the better the thermal insulation performance.
Comparison between HCFO-1233zd(E) and HCFO-1233zd(E)/water mixed blowing agent used in the production of rigid foam, it is known by the change of foam. When the blowing agent is all HCFO-1233zd(E), the distribution of bubble pores is more uniform, and the shape of bubble pores is mainly hexagonal. The pore size distribution is narrower than that of HCFO-1233zd(E)/water and all-water systems, which structurally explains the lower thermal conductivity of HCFO-1233zd(E) system than other systems. When the foaming agent contains water, the average size of foam pores becomes smaller and more uniform, but the shape of the pores has a small amount of pentagonal shape in addition to hexagonal shape. The pore size of the bubble pore of full water foaming foam is larger and the shape is different, and the foam products at this time have low strength and poor adiabatic performance.
Therefore, we will find that with the increase of HCFO-1233zd(E) dosage, the emulsion time decreases and the drawing time and curing time increases in the foaming process. the decrease of HCFO-1233zd(E) dosage, the compression strength of the foam shows a trend of increasing first and then decreasing. The thermal insulation performance of the foam increased with the increase of HCFO-1233zd(E) dosage.