Abstract
The purpose of the present paper was to test the validity of the nonlinear regression method for calculating the non-isothermal crystallization rate constant of the Nakamura's model of a rotational molding grade LLDPE directly from non-isothermal crystallization experiments carried out in a single cell DSC. Cooling rates of 50, 40, 30, 20, 10 and 5 oC/min were used with samples of 3.0 mg under nitrogen atmosphere. Here, good agreement was observed between the experimental relative crystallinity curves and the simulated ones using the calculated parameters by nonlinear regression. It shows that this method can be used to determine the Nakamura's non isothermal rate constant for using in simulation of the cooling phase of rotational molding. In this paper it was used 10-3, 10-4 and 10-14 as the initial crystallinity in the Nakamura's model. However the best average results for all cooling rates was obtained when 10-4 was used. Average spherulitic dimensions of LLDPE studied in this paper did not change significantly with different cooling conditions.
Highlights
IntroductionThe nonlinear regression method can be used for obtaining the parameters of kinetic crystallization models, such as Nakamura’s [1,2], Kamal and Chu’s [3], Dietz [4] and Malkin’s [5], directly from the nonisothermal crystallization data obtained by Differential Scanning Calorimeters
One of the difficulties for incorporation of the crystallization phenomenon in softwares for simulation of polymer processing is the necessity of easy and reliable methods for determining the parameters of a given kinetic model chosen to describe the crystallization process.The nonlinear regression method can be used for obtaining the parameters of kinetic crystallization models, such as Nakamura’s [1,2], Kamal and Chu’s [3], Dietz [4] and Malkin’s [5], directly from the nonisothermal crystallization data obtained by Differential Scanning Calorimeters
The purpose of the present paper was to test the validity of the nonlinear regression method for calculating the non-isothermal crystallization rate constant of the Nakamura’s model of a rotational molding grade Linear Low Density Polyethylene (LLDPE) directly from non-isothermal crystallization experiments carried out in a single cell DSC
Summary
The nonlinear regression method can be used for obtaining the parameters of kinetic crystallization models, such as Nakamura’s [1,2], Kamal and Chu’s [3], Dietz [4] and Malkin’s [5], directly from the nonisothermal crystallization data obtained by Differential Scanning Calorimeters. Results of this method are usually considered good. The most common material used in the process is polyethylene (PE), and in this class stands Linear Low Density Polyethylene (LLDPE) [9] This polymer is semicrystalline and its crystallization during the cooling phase of rotational molding affects both properties and processing conditions
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