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Istražen je utjecaj strukture stiren-butadien (SB) blok kopolimera kao kompatibilizatora na morfologiju i mehanička svojstva mješavina polistirena (PS) i polibutadiena (PB). Anionskom polimerizacijom [1] pripremljeni su SB blok kopolimeri: diblok, S-B ; triblok, S-B-S ; pentablok, S-B-S-B-S, kao i mješavina dibloka i tribloka. Mješavine PS/PB/SB dobivene su ekstrudiranjem. Maseni omjer PS/PB u svim mješavinama bio je 4/1, a blok kopolimeri su dodani u količini od 5 mas.%. Pretražna elektronska mikroskopija (SEM) zajedno s analizom slika (IA) i malokutna rendgenska difrakcija (SAXS) upotrijebljene su za određivanje strukture mješavina, dok su mehanička svojstva mjerena standardnim metodama Zwick i Charpy uređajima. Morfologija (veličina disperziranih čestica, raspodjela veličine čestica i pravilnost fazne strukture) i mehanička svojstva (rastezna žilavost i zarezna udarna žilavost) izabrane su kao ocjena efikasnosti upotrebljenih blok kopolimera kao kompatibilizatora. SEM mikrofotografija PS/PB mješavine bez kompatibilizatora pokazuje praznine, koje odgovaraju ekstrahiranoj PB fazi u PS matrici. Usporedba SEM mikrofotografija PS/PB/SB mješavina i PS/PB mješavine ukazuje na smanjenje veličina praznina. Analizom mikrofotografija utvrđeno je da nekompatibilizirana PS/PB mješavina ima najveću veličinu čestica PB faze u PS matrici, dok kompatibilizirane mješavine pokazuju smanjenje veličini čestica PB faze i užu raspodjelu veličine čestica u odnosu na PS/PB mješavinu. SAXS krivulje svih ispitanih mješavina pokazuju heterogene sustave i nemaju maksimum koji bi odgovarao stvaranju uređenih blok kopolimera. Rastezna žilavost i ukupna energija loma PS/PB mješavina povećava se dodatkom kompatibilizatora. Na osnovi dobivenih rezultata utvrđena je najbolja kompatibilnost u PS/PB mješavini sa SBS blok kopolimerom.

The mechanical properties of the blends of immiscible polymers can be improved by addition of compatibilizers such as block copolymers (BC) having their blocks compatible with the pertinent polymers. These copolymers are localized at the polymer interface, reduce the interfacial tension and so provide a finer morphology of the blend. The copolymers, anchored through their blocks in polymers, suppress their separation and improve interphase adhesion. Strength of these crossings depends on the structure of the copolymer, above all on the length and number of blocks. Meanwhile the role of block length follows from its ability to entanglement formation [1, 2], opinions on effect of the number of blocks differentiates [3, 4]. A theory of interfacial crossings formed by copolymers with various numbers of blocks has been formulated [5, 6]. The theory predicts the multiblocks are more efficient than diblocks. Nevertheless, clear experimental evidence of the theory has not been brought up to now. Therefore an attempt has been made to compare morphology and selected properties of the polymer blends compatibilized with the copolymers of different block number and the same block length. According to compatibilization efficiency of various copolymers the different character of crossings has been judged. Because besides influence of molecular characteristics of a compatibilizer the effect of mixing condition as well as structure and ratio of the components play important role, we tried to limit interference factors followed these facts. A set of the model of linear styrene-butadiene (S-B) block copolymers – S-B, S-B-S and S-B-S-B-S were prepared by anionic polymerization [3] and then blended with polystyrene (PS) and polybutadiene (PB) in an extruder. Weight ratio of PS/PB in all blends was 4/1 and amount of the copolymer was 5wt %. Scanning electron microscopy (SEM) with image analysis (IM) and small-angle X-ray scattering (SAXS) were used for determination of the blend structure, the mechanical properties were measured by standardized methods using Instron, Zwick and Charpy Testers. Morphology (the size of dispersed particles, particle size distribution and phase structure regularity) and stress-transfer induced characteristics (tensile strength, elongation, tensile impact strength and notch impact strength) were chosen as criteria of the compatibilization efficiency of the BCs used. The authors appreciate the financial support of the Grant Agency of the Czech Republic.