Surface and thermomechanical characterization of polyurethane networks based on poly(dimethylsiloxane) and hyperbranched polyester

Two series of polyurethane (PU) networks based on Boltorn® hyperbranched polyester (HBP) and hydroxyethoxy propyl terminated poly(dimethylsiloxane) (EO-PDMS) or hydroxy propyl terminated poly(dimethylsiloxane) (HPPDMS), were synthesized. The effect of the type of soft PDMS segment on the properties of PUs was investigated by Fourier transform infrared spectroscopy (FTIR), contact angle measurements, surface free energy determination, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). The surface characterization of PUs showed existence of slightly amphiphilic character and it revealed that PUs based on HP-PDMS have lower surface free energy, more hydrophobic surface and better waterproof performances than PUs based on EO-PDMS. PUs based on HPPDMS had higher crosslinking density than PUs based on EO-PDMS. DSC and DMTA results revealed that these newlysynthesized PUs exhibit the glass transition temperatures of the soft and hard segments. DMTA, SEM and AFM results confirmed existence of microphase separated morphology. The results obtained in this work indicate that PU networks based on HBP and PDMS have improved surface and thermomechanical properties

Mechanical properties of composites based on unsaturated polyester resins obtained by chemical recycling of poly(ethylene terephthalate)

Composites based on unsaturated polyester (UPe) resins and fumed silica AEROSIL® RY 50, NY 50, RX 50 and NAX 50, as well as graphite, TiO2 or organically modified clay CLOISITE 30B were prepared in order to investigate the influence of reinforcing agents on the mechanical properties of composites. Unsaturated polyester resins were synthesized from maleic anhydride and products of glycolysis, obtained by depolymerization of poly(ethylene terephthalate) with dipropylene glycol (UPe1 resin) and triethylene glycol (UPe2 resin) in the presence of tetrabutyl titanate catalyst. The obtained unsaturated polyesters were characterized by FTIR spectroscopy, acid and hydroxyl values, and their mechanical properties were also examined. Significant increase of the tensile modulus, tensile strength and decrease of the elongation at break was observed for composites prepared after addition of 10 wt.% of graphite or 10 wt.% of TiO2 to the UPe resins, indicating strong interaction between matrix and filler particles. On the other hand, nanocomposites prepared using UPe2 and hydrophobically modified silica nanoparticles showed lower tensile strength and tensile modulus than polymer matrix. The presence of CLOISITE 30B had no significant influence on the mechanical properties of UPe1, while tensile strength and tensile modulus of UPe2 increased after adding 10 wt.% of clay.U ovom radu sintetisani su kompoziti na bazi nezasićenih poliestarskih (UPe) smola i SiO2 (AEROSIL®:RY 50, NY 50, RX 50 i NAX 50), grafita, TiO2 ili organski modifikovane gline CLOISITE 30B u cilju ispitivanja uticaja punioca na mehanička svojstva kompozita. Nezasićene poliestarske smole su sintetisane polazeći od anhidrida maleinske kiseline i proizvoda glikolize dobijenih depolimerizacijom poli(etilen-tereftalata) sa dipropilen glikolom (UPe1 smola) ili trietilen glikolom (UPe2 smola) u prisustvu katalizatora tetrabutil titanata. Sintetisane nezasićene poliestarske smole su ispitane primenom FTIR spektroskopije, određen im je kiselinski i hidroksilni broj i ispitana su njihova mehanička svojstva. Molarna masa srednja po brojnoj vrednosti sintetisanih nezasićenih poliestarskih smola je između 1620-1630 g mol-1. Moduli istezanja i zatezna čvrstoća kompozita pripremljenih dodavanjem 10 mas.% grafita ili TiO2 nezasićenim poliestarskim smolama su značajno porasli u odnosu na čiste poliestre, dok se izduženje pri kidanju smanjilo, što ukazuje na postojanje jakih interakcija između matrice i čestica punioca. Sa druge strane, nanokompoziti sintetisani korišćenjem UPe2 i modifikovanih nanočestica SiO2 su imali manju zateznu čvrstoću i module istezanja nego čista nezasićena poliestarska smola. Pokazano je da prisustvo gline CLOISITE 30B nema značajan uticaj na mehanička svojstva smole UPe1, dok su vrednosti modula istezanja i zatezne čvrstoće UPe2 porasle nakon dodavanja 10 mas.% gline

Characterization of the commercial hyperbranched polyesters

In this paper, properties of the commercially available Boltorn® hydroxy-functional aliphatic hyperbranched polyesters of the second, third and fourth pseudo generation, were investigated. Additionally, samples of the third and fourth pseudo generation were fractionated using the precipitation fractionation method to obtain three fractions of each sample, which were also investigated in this paper. According to the results obtained by GPC analysis, molar mass and polydispersity of the investigated Boltorn® hyperbranched polyesters increased with increase of the pseudo generation number. Value of the limiting viscosity number of the investigated samples, determined using the viscosity measurements of dilute solutions of these polymers in N-methyl-2-pyrrolidone, increased with the increase of the pseudo generation number. On the other hand, the value of the limiting viscosity number of the fractions decreased from the first up to the third fraction. The same trend was also observed for the values of the hydrodynamic diameter of parent samples and their fractions, determined by dynamic light scattering using N-methyl-2-pyrrolidone as solvent. The thermal properties of the investigated Boltorn® hyperbranched polyesters were determined by thermogravimetry in nitrogen atmosphere and it has been shown that thermal stability of these samples increased with increase of the pseudo generation number. End hydroxyl groups of the second and third pseudo generation samples were modified with β-alanine to obtain hyperbranched samples soluble in water. That was fully accomplished only for the Boltorn® hyperbranched polyester of the second pseudo generation. On the other hand, it was possible to dissolve the modified sample of the third pseudo generation in water only after adding a small amount of the NaOH.U ovom radu prikazani su rezultati ispitivanja tri uzorka Boltorn® hidroksi-funkcionalnih hiperrazgranatih alifatskih poliestara druge, treće i četvrte pseudo generacije, kao i frakcija uzoraka treće i četvrte pseudo generacije. Primenom GPC analize pokazano je da sa povećanjem broja pseudo generacije dolazi do rasta molarne mase ali i polidisperznosti ovih uzoraka. Vrednosti graničnog viskozitetnog broja i hidrodinamičkog prečnika ispitivanih poliestara, određenih u N-metil-2-pirolidonu kao rastvaraču, rastu sa povećanjem broja pseudo generacije, dok kod frakcija ove vrednosti opadaju od prve do treće frakcije. Na osnovu termogravimetrijskih rezultata konstantovano je da termička stabilnost ovih uzoraka raste sa povećanjem broja pseudo- generacije. Modifikovanjem krajnjih hidroksilnih grupa Boltorn® hiperrazgranatog poliestra druge pseudo generacije β-alaninom dobijen je uzorak rastvoran u vodi, dok se uzorak treće pseudo generacije, takođe modifikovan β-alaninom, rastvorio u vodi nakon dodavanja male količine NaOH

Micro- and Nanostructured IPNs based on Thermosetting Resins

Different components of interpenetrating polymer networks (IPNs) have different influence on their properties and their behavior in various applications, such as automotive dual curing applications. Dual curing systems, upon hardening, can give interpenetrating polymer networks (IPNs). UV-thermal dual-cure process that was used to obtain IPNs consisted of an UV curable acrylic component and a classic 2-pack urethane component. Novel acrylate-terminated hyperbranched polyester with high functionality HBP(A) was used as part of the acrylic component, which was cured by UV radiation. The urethane part of the IPNs was classical 2-pack polyurethane and it was crosslinked by heating.The aim was to explore the influence of thermosetting resin HBP(A) on IPN properties. First, the weight ratio of HBP(A) and a reactive diluent 2-ethyl hexyl acrylate (EHA) in the IPNs was varied from 100/0 to 25/75, while the urethane component remained the same in all the IPN samples. Then, the IPN with 50/50 weight ratio in acrylic component was used to investigate the influence of the reactive diluent in IPNs on their behavior, but also to see more clearly the role of the HBP(A) component. All the IPNs were also compared to a classical 2-pack polyurethane clear coat consisted of a hydroxyl functional acrylate copolymer (HA) and Desmodur®N3390.The IPNs were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The mechanical properties of the IPNs were also investigated.DMA showed that with increasing HBP(A) in the IPNs, the crosslink density increased, while the flexibility decreased. The data obtained by DMA and DSC showed a decrease of the Tg values with increasing amount of HBP(A). There were slight differences in the thermal stability of the IPNs

Structure and properties of chemically synthesized BiFeO3. Influence of fuel and complexing agent

Perovskite, single multiferroic bismuth ferrite was prepared by two chemical methods: auto-combustion and soft chemical route. Influence of different fuels and complexing agents and thermal treatment on purity of bismuth ferrite powders and density of bismuth ferrite ceramics were investigated. X-ray diffraction technique (XRD) indicated that optimal temperatures and times for calcination and sintering are 600 degrees C for 2 h and 800 degrees C for 1 h with quenching, respectively. Scanning electron microscopy (SEM) analysis showed that soft route synthesized samples formed softer agglomerates and smaller grains with less secondary phases. Powders and pellets were characterized by Brunauer Emmett Teller (BET) specific surface area analysis, particle size distribution, Fourier transform infrared spectroscopy (FT-IR), dilatometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), dielectric and magnetic measurements. Resistivity and origin of electrical resistance were studied by means of impedance measurements. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved