In order to meet the requirements of rotomolding technique, the raw material should have the following performance.
(1) Thermal stability.
The raw material should have thermal stability so that can prevent the reducing performance when material ground into powder. Most
rotomolding products will add antioxidant during manufacturing to decrease the negative impacts on material properties which result from the prolonged heating.
(2) Lower melt viscosity.
The general measurement for melt viscosity is melt mass flow rate (MFR), the unit is g / 10min. The polyethylene, which is often used in the rotomolding industry, its MFR is 2 ~ 8g / 10min (2.16kg, below 190 ℃ ). Moreover, the rotomolding products with complicated structure need material with higher MFR.
(3) Good impact strength.
It is a measurement to distinguish whether the rotomolding products can withstand the low temperature. Generally speaking, the material should maintain excellent impact strength even in the temperature of below 40 ℃.
(4) Higher ESC.
ESC stands for environmental stress cracking, which represents the ability when materials contact with cracking media for a long time. According to tests, the ESC value of rotomolding material should be more than 1000h.
(5) Sufficient bending strength and tensile strength.
Polyethylene has relatively lower strength, while the nylon and polycarbonate plastics have higher strength.
(6) Excellent flexibility and diathermancy.
The flexibility and diathermancy can make the material spread uniformly and rapidly during heating, while the poor flexibility of material will influence the appearance of finished products.
