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Preparation of Reactive Compatilizers and Their Compatibilizing Study in Polypropylene/Polystyrene Blends

Author: LiHao
Tutor: ZhangXianMing
School: Zhejiang University of Technology
Course: Materials Processing Engineering
Keywords: polypropylene grafting styrene copolymer isocyanate amine polyporpylene reactive compatibilizing
CLC: TQ320.1
Type: Master's thesis
Year: 2014
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Abstract

Blending two or more existing polymer to obtain complementary material of physicalproperties is a simple and universal method in polymer industry. However, most of the polymersare so thermodynamically immiscible that it’s difficult to obtain polymer blends with excellentmechanical properties via simple mechanical mixing. Therefore, adding or in-situ formingcompatibility agent during the blending process is essential to reduce the interfacial tension toimprove the compatibility of blends. In this aspect, the reactive compatibility attains moreconcern as the polymer in-situ forming graft, block or cross-linked copolymer in blendingprocess.Both isocyanate and amine groups with obvious and very active, which can be used asreactive compatibilizing agent to compatibilize the blends of incompatible polymers. In thispaper isocyanate and amine functionalized polypropylene (PP) and polystyrene (PS) wereprepared as reactive compatibility for PP/PS blends system. Besides, the different reactionconditions which affect the performance were studied to provide reference of reactivecompatibilizing agent and the PP/PS blends compatibilization.Firstly, the monomer of3-isopropenyl-α,α-dimethylbenzene isocyanate (TMI) containingisocyanate functional group and the amine protected monomer{1-Methyl-1[3-(1-methylethylenyl)phenyl]ethyl}-carbamic acid1,1-dimethylethyl ester(TMITBC) were introduced onto PP to form modified polymer and the property of functionalpolymer in different reaction conditions were studied. It reflected that isocyanate functionalgroup was successfully grafted onto PP backbone, and St could greatly improve the graftingdegree of TMI reducing the degradation of PP. To be specific, as the increase of TMI、St content,the grafting degree of PP was firstly improved and then declined; As the content of DCPincreasing, the grafting degree was firstly increased and then got to stability; with the increase ofTMI and St contents, the viscosity of the PP was increasing, while increasing the DCP contentswould reduce that. Compared with pure PP, modified PP has the higher crystallizationtemperature and the lower melting temperature. The study about amine functionalized polypropylene reflected that amine functionalized polypropylene was obtained after thedeprotection, followed TMITBC successfully grafted onto PP backbone. The monomer contentinfluenced the grafting degree of PP as the contents of TMITBC increasing, the grafting degreeof PP was firstly improved and then was declined. With the increase of TMITBC contents, theviscosity of the PP was increasing, and then decreased again.Secondly, using the same monomer TMI/TMITBC with styrene react in autoclave to formcopolymer, prepared reactive compatibilizer of functionalized polystyrene which containsisocyanate and amine groups. Fourier transform infrared spectroscopy (FTIR) and nuclearmagnetic resonance spectroscopy (1H-NMR) spectroscopies used to analyze the component ofthe synthesized copolymer confirmed desired product obtained by the reaction between styreneand monomers. Gel permeation chromatography (GPC) with FTIR analysis of the compositiondistribution of the product showed that the percentage of the copolymerization product increasedwith the increase of monomer content, and each molecular chain had more functional groups.The rheology analysisre flected that polymer had higher storage modulus (G), loss modulus (G)and complex viscosity (*).Through the synthesized polypropylene and polystyrene based compatibilizer used forPP/PS blend compatibility study, the compatibility effect was confirmed by morphology,rheological properties, dynamic thermal performance, melt and crystallize properties. Thecross-section morphology of SEM showed that the addition of reactive compatibilizer greatlyimproved the compatibility of PP/PS blend compared with the non-compatibilizer blends; anddispersed particles became smaller and finer, showing a certain degree of compatibility.Rheological analysis found that G, G,*have significant improvements in the presence ofcompatibilizer, revealing the improvement of viscous and elastic after the addition ofcompatibility, as well as the workability. DMA analysis showed that PP and PS wereuncompatibility system, and compatibilizer could effectively improve the compatibility of blendswhich might have excellent comprehensive performance. DSC results indicated thatcompatibilizer blends affected slightly the crystal and melt property of PP, with unconspicuouseffect on processing performance.

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