Abstract
Experimental and mathematical modeling analyses were used for controlling melt free-radical grafting of vinylic monomers on polyolefins and, thereby, reducing the disturbance of undesired cross-linking of polyolefins. Response surface, desirability function, and artificial intelligence methodologies were blended to modeling/optimization of grafting reaction in terms of vinylic monomer content, peroxide initiator concentration, and melt-processing time. An in-house code was developed based on artificial neural network that learns and mimics processing torque and grafting of glycidyl methacrylate (GMA) typical vinylic monomer on high-density polyethylene (HDPE). Application of response surface and desirability function enabled concurrent optimization of processing torque and GMA grafting on HDPE, through which we quantified for the first time competition between parallel reactions taking place during melt processing: (i) desirable grafting of GMA on HDPE; (ii) undesirable cross-linking of HDPE. The proposed robust mathematical modeling approach can precisely learn the behavior of grafting reaction of vinylic monomers on polyolefins and be placed into practice in finding exact operating condition needed for efficient grafting of reactive monomers on polyolefins.
Highlights
Studies reveal that melt free-radical grafting of glycidyl methacrylate (GMA) on high-density polyethylene (HDPE) is associated with by-side reactions, which are presented in Scheme 2.[17,20,22] Grafting takes place right after decomposition of DCP initiator
Optimization should be performed in a manner to enable distinguishing the contribution of GMA grafting to final torque, with comparatively lesser amount of energy needed to be overcome by mixer rotors
The literature lacks a clear basis for understanding the contribution of processing and material parameters to overall degree of grafting, what is typically featured by a rise in the processing torque monitored by the blending machine
Summary
Polyolefins (POs) such as polyethylene (PE) and polypropylene (PP) have received an increasing demand among thermoplastic family of polymers thanks to their comparatively low price and reasonable mechanical and processing properties.[1,2,3] The lack of polar groups in the POs, entails some obvious shortcomings including poor adhesion, low paintability, and poor compatibility with polar polymers.[4,5] Theoretical and experimental studies confirmed that morphological, mechanical, rheological, and thermal properties of PO-based blends can be improved by material and processing parameters.[6,7,8,9,10,11] It was shown that the use of appropriate compatibilizer precursors enhances degree of interfacial adhesion in immiscible polymer blends, thereby enhances ultimate properties.[12,13,14,15,16] The challenging point still is finding a proper precursor which delivers sufficient interfacial adhesion and fulfills the requirements of practical applications. Different models including linear and partial (or full) quadratic were examined to obtain the best approximating function over the range of variables This provided a rough estimation of the contribution of GMA grafting reaction to the amount of final processing torque. Hybridizing the capabilities of RSM, ANN, and GA approaches, we provide for the first time a pattern on the competition between grafting reaction of GMA on HDPE and cross-linking of HDPE in the presence of DCP This mathematical framework can be applied in melt production of PO-g-MM compatibilizers of similar families. Time schedule applied in melt grafting of GMA on HDPE
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