Manuel F. Valero

Polyurethane adhesive system from castor oil modified by a transesterification reaction

This study reports the preparation of polyurethane adhesives using polyols obtained from castor oil modified by a transesterification reaction with pentaerythritol. The physical properties of the polyols such as hydroxyl value have been determined and the infrared (IR) spectroscopic analysis of the polyols is reported. The polyols were reacted with aliphatic isocyanate (isophorone diisocyanate) to form polyurethane coatings (NCO/OH ratio = 1). The effect of varied pentaerythritol content in the polyols on the physical properties of polyurethane coatings on wood and steel panels was determined. The characterization of polyurethane coatings carried out by IR spectroscopic analysis and the physicomechanical properties such as hardness, adhesion properties, solvent resistance and chemical resistant determination were reported.

Preparation and Properties of Polyurethanes based on Castor Oil Chemically Modified with Yucca Starch Glycoside

We present novel polyurethanes from renewable materials of castor oil and starch. Castor oil is transesterified with pentaerythritol in order to obtain a wide range of polyols. Yucca starch is converted into glycoside through transglycosylation reactions with ethylene glycol and glycerol. The glycosides from starch are then chemically incorporated to the castor oil polyols by a second transesterification reaction to generate a sequence of polyol-glycosides with a high level of polyhydroxyl content. These products are characterized by the hydroxyl value, viscosity, and specific gravity as a function of the glycoside type content and the kind of castor oil polyol prepared. MALDI TOF mass spectroscopy is used to find the mass fraction of glycosides and polyol-glycosides. Polyurethanes are synthesized from the polyol-glycosides by reaction with isophorone diisocyanate, under different NCO/OH molar ratios. The polymer characterization is accomplished by Fourier transform infrared analysis, tensile stress—strain tests, Shore A hardness, thermogravimetric analysis, chemical resistance to solvents, scanning electron microscopy, and dynamic-mechanical thermal analysis.

Polyurethanes sintetized of polyols obtained from castor oil modified by transesterification with pentaerythritol

Castor oil was reacted by transesterification with various percentages in mass of pentaerythritol to obtain different esters of pentaerythritol. Alternatively, glycerol was also used instead of pentaerythritol for the same reaction in order to establish comparative reference products. The products of the reactions were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy in order to detect and quantify (in terms of the molecular mass and structural information) the components of the products obtained. Analysis for hydroxyl value, acid value, viscosity and specific gravity were used to complete the characterization of the polyols obtained and also of the original castor oil. The polymer characterization was accomplished by tensile stress-strain tests, Shore A hardness, thermogravimetric analysis and chemical resistance to solvents.

Microbial degradation, cytotoxicity and antibacterial activity of polyurethanes based on modified castor oil and polycaprolactone

Abstract The objective of this study was to assess the effects of type of polyol and concentration of polycaprolactone (PCL) in polyurethanes (PUs) on microbial degradability, cytotoxicity, biological properties and antibacterial activity to establish whether these materials may have biomedical applications. Chemically modified and unmodified castor oil, PCL and isophorone diisocyanate in a 1:1 ratio of NCO/OH were used. PUs were characterized by stress/strain fracture tests and hardness (ASTM D 676-59). Hydrophilic character was determined by contact angle trials and morphology was evaluated by scanning electron microscopy. Degradability with Escherichia coli and Pseudomonas aeruginosa was evaluated by measuring variations in the weight of the polymers. Cytotoxicity was evaluated using the ISO 10993-5 (MTT) method with mouse embryonic fibroblasts L-929 (ATCC® CCL-1) in direct contact with the PUs and with NIH/3T3 cells (ATCC® CRL-1658) in indirect contact with the PUs. Antimicrobial activity against E. coli and P. aeruginosa was determined. PUs derived from castor oil modified (P0 and P1) have higher mechanical properties than PUs obtained from castor oil unmodified (CO). The viability of L-929 mouse fibroblasts in contact with polymers was greater than 70%. An assessment of NIH/3T3 cells in indirect contact with PUs revealed no-toxic degradation products. Finally, the antibacterial effect of the PUs decreased by 77% for E. coli and 56% for P. aeruginosa after 24 h. These results indicate that PUs synthesized with PCL have biocidal activity against Gram-negative bacteria and do not induce cytotoxic responses, indicating the potential use of these materials in the biomedical field.

Polyurethane elastomers-based modified castor oil and poly(ε-caprolactone) for surface-coating applications Synthesis, characterization, and in vitro degradation

Polyurethanes (Pus) were synthesized from castor oil and modified through transesterification by pentaerythritol, poly(ε-caprolactone)diol (PCL), and isophorone diisocyanate to form PU coatings. The ratio of NCO/OH groups used was 1:1. The effect of varying the PCL content on the physical properties of wood panel PU coatings was determined. The PU coatings were characterized using Fourier transform infrared spectroscopic analysis, and the physicochemical properties, such as tensile strength, elongation at the break, shore A hardness, and the results of a lap shear test, were reported. Thermal properties of the PU coatings were evaluated using differential scanning calorimetry and thermogravimetric analysis. In vitro PU degradation was related to the hard segment structure and polymer hydrophilicity.

Effect of the incorporation of chitosan on the physico-chemical, mechanical properties and biological activity on a mixture of polycaprolactone and polyurethanes obtained from castor oil.

In the present study, polyurethane materials were obtained from castor oil, polycaprolactone and isophorone diisocyanate by incorporating different concentrations of chitosan (0.5, 1.0 and 2.0% w/w) as an additive to improve the mechanical properties and the biological activity of polyurethanes. The polyurethanes were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, stress/strain fracture tests and swelling analysis, and the hydrophilic character of the surface was determined by contact angle trials. The objectives of the study were to evaluate the effect of the incorporation of chitosan on the changes of the physico-chemical and mechanical properties and the in vitro biological activity of the polyurethanes. It was found that the incorporation of chitosan enhances the ultimate tensile strength of the polyurethanes and does not affect the strain at fracture in polyurethanes with 5% w/w of polycaprolactone and concentrations of chitosan ranging from 0 to 2% w/w. In addition, PCL5-Q-PU formulations and their degradation products did not affect cell viability of L929 mouse fibroblast and 3T3, respectively. Polyurethane formulations showed antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria. The results of this study have highlighted the potential biomedical application of this polyurethanes related to soft and cardiovascular tissues.

Determinación de la densidad de entrecruzamiento de poliuretanos obtenidos a partir de aceite de ricino modificado por transesterificación

Two series of polyols were obtained from castor oil modified by transesterification with various amounts of pentaerythritol and glycerol. The resultant polyol properties were characterized as a function of the hydroxyl functionality. Polyurethane elastomers (PU) were synthesized from the two series of polyols obtained. The crosslink density of those polyurethanes was determined by swelling tests data adjusted to the Flory-Rehners equation and according to the elasticity theory. The variation of the crosslink density of polyurethanes was studied by following the hydroxyl value of the modified polyol utilized in the synthesis and based on the average structure of each polyurethane repeating unit, as determined by the method of matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI TOF MS). The results show that the PU obtained through castor oil modified with pentaerythritol had a higher crosslink density than PU obtained from unmodified castor oil and from PU prepared by transesterification reaction of castor oil with glycerol. PU based on polyols with the higher hydroxyl functionality presented the higher crosslink density.

Polyurethane-Polystyrene Simultaneous Interpenetrating Networks from Modified Castor Oil

A series of simultaneous interpenetrating polymer networks (SINs) based on pentaerythritol modified castor oil polyurethane and polystyrene were studied. Miscibility, phase continuity and phase separation are studied by dynamic mechanical thermal analysis (DMTA). The patterns of extent of the phase separation and the characteristics of the interpenetration reached as a function of the components were deduced. The modulus-composition relationship has been analyzed for the synthesized SINs using theoretical equations based on mechanical models. Most of these models assume perfect adhesion between the homogeneous isotropic phases and the inclusions in the matrix are spherical. The IPNs follow the Budiansky model, which predicts a phase inversion at intermediate compositions.

Polyurethanes from modified castor oil and chitosan: Synthesis, characterization, in vitro degradation, and cytotoxicity

Polyurethanes (PUs) from castor oil (CO), modified CO (MCO) by transesterification reaction, isophorone diisocyanate (IPDI) in an NCO/OH ratio equal to 1, and chitosan (CS) were synthesized to assess their potential as biomaterials. PUs were characterized by Fourier transform infrared spectroscopy, hydroxyl value (ASTM D1957), thermogravimetric analysis, Shore A hardness (ASTM D2240), and scanning electronic microscopy (SEM). Also, contact angle, water retention and in vitro degradation in PBS, and cell viability on fibroblast were performed. The hydroxyl value confirms CO modification, and IR analysis confirms urethane bond formation. The thermal assay does not show new degradation stages and polyol with a high functionality had better hardness performance due to the increase in cross-linking. The micrograph shows micro-phase separation of both polymers. The contact angle shows the hydrophobic surface with an angle over 65°, and the CS and polyol type do not affect swelling and in vitro degradation due to phase separation between both polymers. The cell viability was over 70% in all cases, and solid polymers and degradation products involve non-cytotoxic effects on the samples. The results suggest a potential for these formulations in the biomedical field.

Poliuretanos obtenidos a partir de aceite de higuerilla modificado y poli-isocianatos de lisina: síntesis, propiedades mecánicas y térmicas y degradación in vitro

Biodegradable polyurethanes (PUR) were prepared from polyols derived from castor oil by transesterification of pentaerythritol-modified castor oil and lysine polyisocyanates (LDI and LTI). The polyurethanes obtained were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). The mechanical behavior of the polyurethanes was measured by Shore A hardness and tensile testing (stress-strain curves). The biodegradable nature of the material was determined by contact angle, water absorption tests, and in vitro degradation in PBS solution. This study aims to examine the effect of the structure and functionality of diisocyanate on the mechanical properties and in vitro degradation of the material. The results were compared with homologous materials obtained from isophorone diisocyanate (IPDI) used in previous works. The objective was to evaluate candidate materials that can be potentially used in tissue engineering.