Sanja Lučić Blagojević

Silane pre-treatment of calcium carbonate nanofillers for polyurethane composites

Abstract In this work we have investigated the effects of CaCO3 nanofiller pretreatment on the properties of polyurethane (PU) composites prepared by a mixing procedure. The aim was to enhance interactions at the matrix/filler interface and to improve the distribution of the filler in the polyurethane matrix. CaCO3 nanofiller was treated with two different functional trialkoxysilanes, viz. γ-aminopropyltriethoxysilane (AMPTES) and γ-glycidoxypropyltrimethoxysilane (GPTMS). Fourier transform IR spectroscopy of the pre-treated CaCO3 surface indicates that AMPTES formed a high-molecular-weight ladder-type structure on the CaCO3 surface, while GPTMS was adsorbed in the form of a lower-molecular-weight oligomeric structure. Increased ultimate tensile strength and elongation were obtained for PU + CaCO3 nanocomposites with silane pre-treated filler. This can be explained as the consequence of better stress transfer through the composite, observed on scanning electron micrographs, due to an improved adhesion between PU matrix and silane-treated fillers. The reinforcement effect is more pronounced for PU composites with aminosilane-treated CaCO3 filler in comparison to filler treated with glycidoxysilane.

Effect of preparation on morphology-properties relationships in SAN/EPDM/PCC composites

Mechanical and morphological properties of composites containing styrene—acrylonitrile (SAN) copolymer, ethylene— propylene—diene (EPDM) polymer, and different types of precipitated calcium carbonate (PCC) were investigated and their properties were analyzed in regard to PCC surface properties and the way of sample preparation (with or without use of a masterbatch (MB)). Contact angles of test liquids on PCC samples were measured in order to determine surface free energies of filler and to predict strength of filler—polymer interactions. Filler—polymer interactions play a significant role in determining preferential localization of the filler in the composite. The tensile and impact strength results of the composites without the MB show much higher values than composites prepared with the MB. Significant decrease of tensile strength is observed for the samples prepared with the MB due to change in morphology, which is elongated dispersed EPDM particles in SAN matrix, compared to the samples prepared without the MB that have droplet morphology.

Utjecaj modifikacije višestjenih ugljikovih nanocjevčica na svojstva poliuretana: II. Mehanička svojstva, električna provodnost i toplinska postojanost

Za razliku od jednostjenih ugljikovih nanocjevčica (SWCNT) koje se sastoje od jednog grafenskog sloja smotanog u cilindar, višestjene ugljikove nanocjevčice (MWCNT) izgrađene su od više smotanih grafenskih slojeva. Ugljikove nanocjevčice, zbog iznimnih mehaničkih, toplinskih i električnih svojstava, predstavljaju skupinu nanopunila koja mogu znatno poboljšati svojstva polimera.2,3 Međutim zbog nanodimenzija i van der Waalsovih međudjelovanja između pojedinačnih ugljikovih nanocjevčica izrazito su sklone agregiranju,2 što predstavlja problem u postizanju jednolike raspodjele u polimernoj matrici. Modifikacija površine ugljikovih nanocjevčica predstavlja značajan smjer u savladavanju tog problema.4

Utjecaj modifikacije višestjenih ugljikovih nanocjevčica na svojstva poliuretana: I. Morfologija i toplinska svojstva

Poliuretanski elastomeri su blok-kopolimeri, koji se sastoje od krutog i fleksibilnog segmenta. Zbog razlike u polarnosti odnosno termodinamičke nekompatibilnosti, ti segmenti se razdvajaju u meku i tvrdu fazu. Zahvaljujući strukturi, poliuretanski elastomeri imaju superiorna svojstva povezana s visokom tvrdoćom s obzirom na modul, visokom otpornošću na abraziju, izvrsnim mehaničkim svojstvima te biokompatibilnosti i stoga imaju iznimno široku primjenu u području adheziva, optoelektronike, biotehnologije i brojnim drugim.1,2

Pre-treatment of CaCO3 nanofiller by irradiation in the presence of vinyl monomers for the preparation of poly(vinyl acetate) composites

Abstract Poly(vinyl acetate) (PVAc) composites were prepared by different approaches, namely (i) by mechanical mixing of untreated CaCO3 and PVAc, (ii) by mechanical mixing of CaCO3 pre-treated by irradiation polymerization in the presence of vinyl acetate, and (iii) by in situ emulsion polymerization of VAc in the presence of untreated CaCO3 nanofiller. The effects of nanoparticle pre-treatment and different approaches of preparation were correlated with changes in morphology and mechanical properties of PVAc composites using scanning electron microscopy and tensile tests. Untreated CaCO3 nanoparticles in the composite prepared by mechanical mixing provided strong interactions with the PVAc matrix. On the other hand, CaCO3 pre-treated nanoparticles decreased the interfacial interactions. For composites prepared by in situ polymerization a better dispersion of encapsulated nanoparticles was achieved and, as a result, a significant improvement of composite strength was observed. Interfacial interactions in nanocomposites can be changed by filler pre-treatment or by a suitable way of nanocomposite preparation.