At present, the materials of plastic waterproof junction boxes are mainly ABS and polycarbonate engineering plastics. The following is a brief introduction to the properties of the two resins:
1、 ABS
ABS resin is an amorphous polymer formed by copolymerization of acrylonitrile (23% - 41%), butadiene (10-30%) and styrene (29% - 60%), referred to as ABS for short. Its performance is as follows:
（1）.  ABS is non-toxic and tasteless, and its appearance is ivory translucent, or transparent particles or powder. The density is 1.08-1.18/cm3, the search rate is 0.4% - 0.9%, the moisture absorption is less than 1%, the melting temperature is 217-237 ℃, and the thermal decomposition temperature is more than 250 ℃.
（2）.  ABS is hard and tough, with good rigidity, low temperature impact resistance, creep, dimensional stability and wear resistance; The linear expansion coefficient is very small, the molding shrinkage is small, and the surface gloss is excellent.
（3）.  ABS has good electrical insulation performance and is hardly affected by temperature, humidity and frequency. It can be used in most environments.
（4.）. The thermal deformation temperature of ABS is 93-118 ℃, and the product can be increased by about 10 ℃ after annealing treatment. It can be used in the temperature range of - 40 ℃ - 100 ℃, and can still show certain toughness at - 40 ℃.
（5）.  ABS is flammable, with yellow flame, black smoke and special odor, but it does not drip.
（6）. ABS is not subject to water. Affected by inorganic salts, alkalis and various acids, but dissolved in ketones, aldehydes and chlorinated hydrocarbons, stress cracking will occur due to the erosion of glacial acetic acid and vegetable oil; ABS has poor weather resistance and is easy to be degraded under the action of ultraviolet light; After half a year outdoors, the impact strength will decrease significantly.
（7）. ABS has strong adsorption and is an excellent material for plastic electroplating. It has good compatibility with polar resin and can change the performance of PVC.
2、 Polycarbonate (PC)
Polycarbonate is a kind of linear polymer with alternating carbonate groups in macromolecular chain, which has excellent properties.
(1) PC is a transparent or white hard and tough thermoplastic resin with good flame retardancy. When burning, the flame is yellow, melted and foamed, giving off the odor of flowers and fruits, and self extinguishing when leaving the fire.
(2) PC is a highly transparent resin, with a light transmittance of 85% - 90%, a refractive index of 1.589, close to PMMA (organic glass), suitable for lens materials.
(3) PC has rigid and tough mechanical properties, and its impact resistance is very excellent among thermoplastic materials, more than 3 times higher than PA and POM, and close to the level of PF and up FRP; The tensile strength, bending strength and dimensional stability are good, and the stress cracking resistance is poor, and the notch sensitivity is high.
(4) The thermal performance of PC is excellent, and the product can be used in the temperature range of - 60-125 ℃; The thermal deformation temperature is about 130-140 ℃, the embrittlement temperature is about - 100 ℃, and the melting point is about 220-230 ℃; Good electrical insulation performance; The volume resistance is 5 × 1016Ω. Cm, worse than PE, PS and polytetrafluoroethylene; Thermal conductivity and linear expansion coefficient are small.
(5) PC has stable chemical resistance and is resistant to dilute acid, water, oil, aliphatic hydrocarbon, salt and oxidant at room temperature; Not resistant to hot water above 60 ℃; PC is dissolved in dichloromethane, chlorobenzene and dioxane.