| Owing to the impact of mechanical force, mechanical-chemical grafting method of molten polymer makes long chains break and generate free radicals which graft with polar group. Hence this method can be employed to produce master batch for hot melt adhesive industrially. This paper, integrating the strong shear impact of chemical reactor in screw type and the design principles of chemical reactor in millstone type, develops a chemical reactor with strong shear force(authorization patent No. ZL201520406380.9). Based on the midpoint fracture theory and molten theory of polymer, numerical modeling is applied to simulate the effects of structure changes in screw and cylinder on motion trail of molten polymer in the flow field of the reactor and on shear force fluctuation along this trial. Consequently, the optimal value of the structure to reactor’s core components named screw and cylinder can be obtained according to the simulation result. The optimal value of screw edge width to the chemical reactor with strong shear force is 6mm. The optimal value of this facility’s spiral edge corner section and the cylinder groove depth are 45 ° and 1mm respectively.In order to predict the product of the polymer after crossing the apparatus and the process of chain scission in strong shear force field, four regions termed delivery zone, stretching zone, strong-shear zone and multi-act zone respectively are introduced, on the basis of the midpoint fracture theory and extrusion theory, to describe the reaction’s flow field conveniently. Through the finite element simulation by POLYFLOW and molecular dynamics simulations by Materials Studio, a new chain scission theory, which is developed by molten theory of polymer and midpoint chain scission theory, is applied to study the impact of temperature and revolving speed on the process of chain scission and predict the molecular weight distribution of polymer after breaking. In this way, the calculation method of the number average molecular weight to a given molecular weight polymer, can be worked out taking revolving speed and temperature into consideration. And this can be employed as a theoretical guidance for the experimental results or production process of our chemical reactor with strong shear force.Prototype is manufactured according to the parameters of optimally structural scheme. Regarding temperature as a variable, shear experiments of GPPS152 P is conducted at 180℃,210 ℃, 230 ℃, 260 ℃ respectively. Besides, the chemical reactors’ revolving speed is set as 50 r / min. MFR of GPPS152 P,undergoing shear at revolving speed of 50 r / min and shearing temperature 230 ℃,increases 26.7%,measured by melt flow rate instrument. A new measurement termed MFR-molecular weight conversion method based on Hagen-poiseuille Law and Fox-Flory theory is developed in this paper. Molecular weight of the sample is reduced by 7%, calculated by this method. It indicates that the chemical reactor has good shear effect on PS152 P. Regarding revolving speed as variable, the reactor’s shear temperature set as 230 ℃, measurement is implemented according to the methods described above to study the molecular weight changes of GPPS152 P after crossing different shear velocity field. It can be concluded that the increase of revolving speed is beneficial to obtain narrow molecular weight distribution products.GPC test is applied to measure the molecular weight of GPPS152 P raw materials and other samples selected in terms of MFR-Molecular weight conversion method, such as sample obtained at shear temperature of 180 ℃ and revolving speed 50 r / min, sample at 230 ℃ with the revolving speed of 20 r / min and 80 r / min respectively. Taking the MFR change of each sample obtained in various shear temperature and revolving speed into consideration, it can be concluded that the shear speed increasement is conducive to molecule weight decreasement of the sample after shearing and the molecular weight distribution becoming narrower. In addition, when the shearing temperature decreases, chain scission effect is obvious. It causes Number average molecular weight becoming smaller, which results in distribution broadening. Finally, the molecular weight of GPPS152 P samples, crossing the force fields of 180℃, under revolving speed of 100r/min, four times is measured by GPC test. Molecular weight is reduced by 13%.The chemical reactor apparatus in this paper is developed to make chain scission of polymer happen which can provide free radicals for polymers’ grafting. Both the simulation and experimental result indicate that the device has a good performance in mixing. All phenomena demonstrate that the facility can not only provide mechanical stress that induces graft of polymer; it is also conductive to complete the reaction of graft. In addition, POLYFLOW and Material Studio software are employed to study the process of chain scission to molten polymer and estimate the molecular weight distribution after shearing in theory. A new equivalent method is applied to converts macroscopic force field into micro force field exerting on single polymer chain. Furthermore, the molecular weight distribution of polymer can also be estimated by this method. Hence this method, corrected by experimental result, can be a guideline to produce a given master batch which is employed in graft by this chemical reactor with strong shear force or similar structures to extrusion apparatus. |
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