Investigation on solidification behaviour of high-density polyethylene during thin-walled injection moulding: correlation between crystallisation kinetics and thermal gradient field

The influence of temperature fields on the crystallisation kinetics of high-density polyethylene during injection moulding was disclosed in this work. The dimensionless X = 0.4 along the part thickness was a critical location, within which the heat transfer of polymer was primarily affected by thermal conduction. When X > 0.4, the decay in temperature tended to become stable with limited variation in t1/2−1 value (an indicator of average crystallisation rate). The experimental results indicated that the crystallisation rate was proportional to the cooling speed, regardless of the cooling conditions utilised. The sequence of relative crystallinity was in consistence with that of secondary temperature difference. The present study will be of practical significance to further investigation on the ‘processing–structure–property’ relationship for polymeric materials.