Andrés E. Ciolino

Enhancement of thermoplastic starch final properties by blending with poly(ɛ-caprolactone).

Final properties of two thermoplastic corn starch matrices were improved by adding poly(ɛ-caprolactone), PCL, at 2.5, 5, and 10% w/w. One of the thermoplastic starch matrices was processed using water and glycerol as plasticizers (SG) and the other one was plasticized with a mixture of glycerol and sodium alginate (SGA). Blends were suitably processed by melt mixing and further injected. Films obtained by thermo-compression were flexible and easy to handle. Microstructure studies (SEM and FTIR) revealed a nice distribution of PCL within both matrices and also a good starch-PCL compatibility, attributed to the lower polyester concentration. The crystalline character of PCL was the responsible of the increment in the degree of crystallinity of starch matrices, determined by XRD. Moreover, it was demonstrated by TGA that PCL incorporation did not affect the thermal stability of these starch-based materials. In addition, a shift of Tg values of both glycerol and starch-rich phases to lower values was determined by DSC and DMA tests, attributed to the PCL plasticizing action. Besides, PCL blocking effect to visible and UV radiations was evident by the incremented opacity and the UV-barrier capacity of the starch films. Finally, water vapor permeability and water solubility values were reduced by PCL incorporation.

Thermoplastic starch plasticized with alginate–glycerol mixtures: Melt-processing evaluation and film properties

Corn starch melt-processing in the presence of a commonly used plasticizer mixture (water/glycerol) and a non-conventional alternative (alginate/glycerol) was evaluated. All assayed formulations were successfully processed by melt-mixing and injected in circular probes. It was determined that all samples presented a typical viscoelastic behavior, observing a decrease in storage and loss modulus with water and alginate concentration, which facilitated samples processability. Concerning to thermal stability, it was not affected neither for water nor alginate presence. From injected probes, flexible films were obtained by thermo-compression. Films with the highest assayed water content presented a sticky appearance, whereas those containing alginate were non-tacky. Plasticizing action of water and alginate was evidenced by the occurrence of homogeneous fracture surfaces, without the presence of unmelted starch granules. Besides, the shift of glass transition temperature to lower values also corroborated the plasticizing effect of both additives. In conclusion, obtained results demonstrated the well-plasticizing action of sodium alginate on starch matrix, turning this additive into a promissory alternative to replace water during melt-processing of thermoplastic corn-starch.

Influence of amorphous block on the thermal behavior of well-defined block copolymers based on ε-caprolactone

In this work, we studied the thermal characterization of block copolymers based on ε-caprolactone. The copolymers were obtained by anionic polymerization techniques, using different co-monomers such as styrene (S) and dimethylsiloxane (DMS). Synthesized copolymers were characterized by H-nuclear magnetic resonance, size exclusion chromatography, and Fourier transform infrared spectroscopy. Isothermal crystallization was performed by differential scanning calorimetry (DSC), and Avrami’s theory was employed in order to obtain kinetics parameters of interest, such as the half-life for the crystallization process (t1/2), the bulk crystallization constant (k), and the Avrami’s exponent (n). The spherulitic growth was measured by polarized optical microscopy in order to determine the crystallization behavior. Poly(ε-caprolactone) block (PCL) crystallization was analyzed by considering the physico-chemical characteristics of the neighboring block, PS or PDMS. The chemical nature of the neighbor block in the PCL-based copolymer affects the kinetics parameters of Avrami’s equation, as can be deduced by comparing the values obtained for pure PCL and the studied block copolymers. On the other hand, the apparent thermal degradation activation energies Ead for PCL and block copolymers were determined by Ozawa’s method. The incorporation of PDMS instead of PS improves the stability of the resulting copolymer, as it was observed by thermogravimetric analysis.

Modified Starches Used as Additives in Enhanced Oil Recovery (EOR)

Enhanced oil recovery (EOR) implementation arises as a supplementary technology to conventional ones, optimizing the not-easily recoverable oil phase. Estimation of oil remnant in reservoirs approaches to seven billion of barrels, after primary and secondary recoveries. One of the EOR strategies implies the use of displacing fluids, such as water-soluble polymers, which are pumped into the reservoir forcing the oil to flow toward the production wells. Thus, the state of the art related to the use of different starch derivatives in EOR is included in this chapter. Besides, diverse synthesis methodologies of the modified starches are presented, analyzing the optimal conditions of each reaction. Particularly, the synthesis of cationic starches is reported since they are the most used in EOR. Modification degree and physicochemical properties of the derivatives are included. Rheological and flow properties of displacing fluids are also discussed as a function of starch concentration.

Mild microwave-assisted synthesis of aluminum-pillared bentonites

Two types of bentonites were modified using a cleaner method to prepare aluminum-pillared clays. This methodology involved a purifying stage, an intercalation process, and a microwave irradiation step at low energy power. Structural changes induced by pillaring process were demonstrated by thermal behavior, as well as morphological characterization. The effect of pillaring process on thermal stability of clays was studied, and the mass lost associated with the dehydroxylation of the octahedral clay sheets was not detected for modified bentonites. In addition, an analysis of their chemical composition and crystalline structure was also performed. Concerning industrial applications of these bentonites, two potential uses were proposed: (1) as reinforcement of different polymers matrices such as thermoplastic starch (TPS), high-density polyethylene (HDPE), and poly (styrene-b-butadiene-b-styrene), SBS; and (2) as removal agent for cadmium (Cd) species present in wastewaters. Bentonite particles reinforced thermoplastic starch matrix and increased ultraviolet barrier capacity of HDPE composites. Besides, bentonites improved the mechanical performance and modified barrier properties of SBS. Regarding effluents purification, an adequate Cd adsorption from aqueous solutions was observed (77%), proving their feasibility to be used as non-conventional removal agents.

Anionic Ring Opening Polymerization of ε-Caprolactone Initiated by Lithium Silanolates

Ring-opening homo- and co-polymerization reactions of ϵ-caprolactone were performed by employing anionic polymerization (high vacuum techniques) and lithium silanolates (LS) as initiators. LS were obtained by reaction between hexamethyl(cyclotrisiloxane) and sec-Bu–Li+, or from living poly(dimethylsiloxanyl)lithium chains. The results indicated that LS are efficient initiators for the ring-opening polymerization of ϵ-caprolactone, providing the respective homogeneous polymers in good yields.

Tailor-Made, Linear, and “Comb-Like” Polyester-Based Copolymers: Synthesis, Characterization, and Thermal Behavior of Potential 3D-Printing/Electrospinning Candidates

Tailor-made, linear, and “comb-like” poly(e-caprolactone)-based copolymers were synthesized by employing a combination of controlled polymerization techniques. Poly(dimethylsiloxane-block-e-caprolactone) copolymers (SCL#) were synthesized by a combination of anionic and ring-opening polymerization (ROP), whereas “comb-like” poly(hydroxyethylmethacrylate-co-(hydroxyethylmethacrylate-graft-e-caprolactone)-block-e-caprolactone) (HEMACL#) were synthesized through simultaneous ROP and reversible addition fragmentation chain transfer (RAFT) polymerization. Copolymers were characterized by hydrogen nuclear magnetic resonance (1H-NMR), size exclusion chromatography (SEC), and Fourier transform infrared (FTIR) spectroscopy. All polymers exhibited narrow molar masses distributions ( ), and their thermal properties were analyzed by isothermal crystallization kinetics (Avrami’s theory, by using differential scanning calorimetry (DSC)) and by employing modulated thermogravimetric analysis (MTGA). The macromolecular structure exerts a noticeable effect on the PCL block behavior when compared to the PCL homopolymer, at least for the temperature range studied (16–24°C): less differences in thermal properties were observed for linear block copolymers, whereas for “comb-like” graft copolymers their final crystallization capacity strongly depends on the presence of branches. For both sets of copolymers, the decrease in the resulting melting temperatures and the increase in the half-life crystallization time values might be useful processing parameters, particularly if these copolymers are planned for using as an alternative source of 3D printing or electrospinning materials.

Bismuth (III) sulfide as additive: towards better lubricity without toxicity

Purpose The purpose of this study is to design a fluid formulation with good lubricant properties by using an environmentally friendly additive for: high and low contact pressure conditions and steel/steel and polymer/steel systems. Design/methodology/approach Bismuth (III) sulfide (Bi2S3, “green chemistry” synthesis) is added to a commercial vinyl-terminated silicone fluid (PDMS-Vi) to obtain different weight-per cent mixtures. Tribological performance of formulations is studied from Reichert’s tests (steel/steel system) and block on ring tests (polymer/steel). The results are compared with formulations prepared with commercial bismuth (III) sulfide (Bi2S3), molybdenum (IV) sulfide (MoS2) and graphite. Findings An orthorhombic crystal lattice (XRD ) and a high-purity product (XRF) are evidenced for synthesized Bi2S3. Lubricant properties increase when the weight-per cent of the synthesized Bi2S3 increases in formulations. The wear area decreases up to 90 per cent according to Reichert’s tests. The synthesized Bi2S3 shows a better tribological behavior when compared to commercial Bi2S3, MoS2 and graphite. Originality/value Replacement of lead derivatives by an environmentally friendly lubricant in extreme pressure (EP) formulations and excellent performance compared to commercially used additives are achieved.

A Straightforward Methodology for the Synthesis of α,ω-Telechelic Poly(dimethylsiloxane)s

In this work we report the synthesis of α,ω-telechelic poly(dimethylsiloxane)s (α,ω-PDMS) by employing a novel bifunctional initiator obtained from a commercially available siloxane precursor, diglycidylether-terminated poly(dimethylsiloxane) (PDMS-DGE). The synthetic strategy was easily followed by different colour changes, and involved the high-vacuum reaction of sec-Bu−Li+ with 1,1′-diphenylethylene (DPE) to afford the addition adduct (bright red) that was subsequently reacted with PDMS-DGE, promoting the nuclephilic ring-opening from epoxide-end chains. The resulting bifunctional initiator (light green) was then employed to polymerize hexamethyl(cyclotrisiloxane) monomer (D3) by using conventional anionic polymerization (from light green to pale yellow). From suitable terminating agents, silane (–SiH), vinyl (–CH=CH2), hydroxy (–OH), and even methacryloyl α,ω-PDMS were obtained. 1H NMR and FT-IR analyses confirmed the presence of the targeted functional groups in the resulting polymers. However, a careful siliconization procedure should be performed over glass surfaces during the fractionation of chlorosilane ampoules in order to avoid the presence of silanol moieties that decrease end-capping efficiency. This fact was observed not only from NMR but also from size exclusion chromatography (SEC) analyses, since narrow molar masses distributions (1.15 ≤ Mw/Mn ≤ 1.3) and a good control over the resulting molar masses were observed.