Strukturiranje polipropilenske matrice u kompozitu

Binarni kompoziti izotaktnog polipropilena (iPP) s talkom i wollastonitom modificirani s različitim elastomerima: (poli(stiren-bbutadien-b-stiren) (SBS), poli(stiren-b-etilen-co-propilen) (SEP), poli(stiren-b-etilen-co-butilen-b-stiren) (SEBS), SEBS kopolimer cijepljen s maleinskim anhidridom (SEBS-g-MA), etilen/propilen/dienski kaučuk (EPDM) i metalocenski kopolimeri polipropilena (mEPR)) pri definiranim različitim omjerima sadržaja proučavani su pomoću različitih mikroskopskih metoda (optička, SEM, TEM), rendgenskom difrakcijom pri velikom kutu (WAXD) i diferencijalnom pretražnom kalorimetrijom (DSC). Kompleksna istraživanja odnosa struktura-svojstvo uspoređivanjem ternarnih iPP kompozita sa sastavnim binarnim kompozitima i binarnim mješavinama pokazala su da različiti čimbenici djeluju na (re)strukturiranje kristalaste polipropilenske matrice tijekom kristalizacije i očvršćivanja (solidifikacije) tijekom priprave ploča izravnim prešanjem. Strukturna istraživanja usmjerena su na određivanja čimbenika koji utječu na rast kristalita i sferolita, faznu strukturu iPP kristalita, stupanj kristalnosti, orijentaciju čestica punila i iPP kristalita, faznu morfologiju čestica i sustava kompozita i sastavnih mješavina polipropilena. U međuigri ovih čimbenika koji sudjeluju u strukturiranju iPP matrice mogu se prepoznati slijedeći utjecajni faktori: (i) nukleacija sitnim dispergiranim česticama polimera i punila, (ii) orijentacija iPP kristalita i čestica punila, (iii) migracija/prijenos iPP lanaca iz otočića taljevine u rastuće lamele tijekom očvršćivanja, (iv) uklapanje (enkapsulacija) dispergiranih čestica i punila koja vodi do morfologije jezgra-ljuska, (v) steričkih faktora smetnji koje generiraju čestice punila i dispergirane čestice elastomera pri sferolitizaciji iPP matrice i (vi) moguća djelomična kokristalizacija u područjima iPP/metalocenski kopolimer polipropilena (iPP/mEPR).
Binary isotactic polypropylene (iPP) composites with talc and wollastonite were modified with different elastomers: poly(styrene-bbutadiene-b-styrene) (SBS), poly(styrene-b-ethylene-co-propylene) (SEP), poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS), SEBS grafted with maleic anhydride (SEBS-g-MA), ethylene/propylene/diene terpolymer (EPDM), and propylene-based metallocene (mEPR) at different content ratios and studied by different microscopic techniques (optical, SEM, TEM), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Complex investigations of the structure-property relationships by comparison of ternary iPP composites with constitutive binary composites and binary blends showed that different factors affect (re)structuring of the semicrystalline polypropylene matrix during its crystallization and solidification during preparation by compression moulding. Structural investigations were focused on determination of influencing factors in crystallite and spherulite growth, phase structure of the iPP crystallites, degree of crystallinity, orientation of filler particles and iPP crystallite, structuring/spherulitization of the iPP matrix, and phase morphology of particles and polypropylene composite and constitutive blend systems. From the interplay of different factors in structuring of the iPP matrix the following influencing factors could be recognized: (i) nucleation by tiny dispersed particles of polymers and filler particles, (ii) orientation of the iPP crystallite and filler particles, (iii) migration/transferring of the iPP chains from melt islands to growing lamellae during solidification, (iv) encapsulation of dispersed/filler particles leading to core-shell morphology, (v) steric hindrance factors generated by filler and dispersed elastomer particles in the spherulitization of the iPP matrix, and (vi) possible partly co-crystallization in the iPP/propylene-based metallocene copolymer (iPP/mEPR) regions.