Velta Tupureina

Improvement of the deformative characteristics of poly-β-hydroxybutyrate by plasticization

Plasticized systems of poly-β-hydroxybutyrate (PHB) are studied, where low-molecular compounds traditionally used for this purpose for various systems, i.e., dioctyl sebacate, dibutyl sebacate, polyethylene glycol, Laprol 503, and Laprol 5003, are used as plasticizers. All of them are nontoxic and biodegradable compounds with a similar molecular weight and comparable polarity of molecules. The main purpose of this study is to improve the deformability of PHB taking into account the structural changes in plasticized PHBs. The plasticizers chosen are completely compatible with the polymer and form a monophase system up to a plasticizer content of 15–20%. An increase in the plasticizer content allows us to increase efficiently the deformability of the polymer (the relative breaking elongation of PHB at room temperature grows up to 250–300%). At the same time, the system becomes considerably weaker and therefore there is no point in increasing the concentration of plasticizers by more than 20 wt.%. According to the data obtained from DSC measurements, the ratio between the amorphous and crystalline regions of PHB in the presence of plasticizers mentioned remains practically constant. The changes in the elastic properties of PHB/low-molecular plasticizer systems are mainly due to efficient weakening of intermolecular interactions in the amorphous regions of the polymer. A slight decrease in the crystalline order of PHB is of secondary importance.

Biodegradable materials from plasticized PHB biomass

Biodegradation rate in different environments as well as deformation characteristics of poly-β-hydroxybutyrate (PHB), PHB biomass and of plasticized systems thereof have been investigated. Polyethylene glycol (PEG) and oxypropylated glycerine or laprol (LAP) were selected as plasticizers. Increase of the content of plasticizer from 5 to 50 % gave rise of the elongation at break from 4 to 25 % for LAP and from 2 to 9 % for PEG, respectively. No significant changes of strength were recorded. It remained comparatively small - around 2.5 MPa. PHB, biomass and the PHB composition containing 10 % PEG completely decomposed in soil during 30 days. PHB containing 33 % of biologically stable LAP additives lost half of its mass at the same period. Structural changes of plasticized biomass are also shown.

Preparation and Structural Properties of Free Films from Rapeseed Oil-Based Rigid Polyurethane-Montmorillonite Nanocomposites

The preparation of free standing films of biobased rigid polyurethanes (PU) from rapeseed oil (RO) and diethanolamine (DEA) polyol and its modification with organomontmorillonite (OMMT) nanoparticles are described. Heat enthalpy of the interaction during in situ mixing of RO/DEA polyol and OMMT is measured in isothermal profile. The Fourier transform infrared spectral analysis (FTIR-ATR) is used to determine the urethane group concentration and hydrogen bonds formation in PU and PU/OMMT nanocomposites. X-ray diffraction shows the formation of intercalated and exfoliated structures of OMMT. The glass-transition temperature is used to demonstrate the formation for the intercalated and exfoliated nanocomposites of an interphase with a possible compact structure and the altered polymer chain mobility. The prepared PU/OMMT nanocomposites are also characterized by the enhanced thermal degradation characteristics upon heating in air atmosphere.

The investigation of sensing mechanism of ethanol vapour in polymer-nanostructured carbon composite

Polymer-nanostructured carbon composites (PNCC) using three different polymers as composite matrix materials (polyvinylacetate (PVAc), polyethylene glycol (PEG) and ethylene-vinylacetate copolymer (EVA)) have been developed. High structure carbon black Printex XE2 (Degussa AG) was used as a composites filler. Ethanol vapour sensor-effect of composites was determined as a change of electrical resistance as the composite was held in ethanol vapour for 30 seconds. Reversibility of electrical resistance of PNCC, response stability and repeatability have been measured and compared. The electrical resistance response of EVA-nanostructured carbon composite (EVA-NCC) to ethanol vapour as a function of vinylacetate content in the copolymer has been evaluated. Promising ethanol vapour sensor-effect has been observed for PEG-NCC followed by PVAc-NCC and EVA-NCC.

Characterization of various kinds of paper as reinforcement for biodegradable polymer composites

Some structural characteristics and properties of a diverse paper selection were studied with the aim to create biodegradable polymer composites for packaging materials. Paper in such composites would serve as a reinforcement and biodegradable polymer as a matrix. Tensile and tear properties of the tested papers depended not only on paper density (or void content) but also on some other paper structure features. As polymers for composite production are applied from solution, the impact of solvent on the mechanical properties of paper was investigated.

Synthesis and properties of hydrophilic segmented poly(urethanes) based on poly(ethylene glycols) and glycerol monostearate

Poly(urethanes) having the structure of comb-shaped copolymers were synthesized from glycerol monostearate, poly(ethylene glycols) with M n = 300–6000, and 1,6-hexamethylene diisocyanate. Effects of the molecular mass of segments and of the contents of soft segments and side chains on both the glass transition temperature of the soft segment and on the melting point and the enthalpy of melting of crystalline phases involving soft segments and side chains were studied by DSC and IR spectroscopy. The resulting comb-shaped copolymers were shown to exhibit thermoplastic and hydrophilic behavior. It was demonstrated that the ultimate tensile strength, yield stress, and Young’s modulus of copolymer films increase with an increase in the molecular masses of soft and hard segments with their ratio maintained constant.

Microencapsulation of mildronate in biodegradable and non-biodegradable polymers.

Abstract The extremely high hygroscopicity (solubility in water ≥2 g/ml) of the pharmaceutical preparation mildronate defines specific requirements to both packaging material and storage conditions. To overcome the above mentioned inconveniences, microencapsulated form of mildronate was developed using polystyrene (PS) and poly (lactic acid) (PLA) as watertight coating materials. Drug/polymer interaction as well as influence of the microencapsulation process variables on microparticle properties was studied in detail. Water-in-oil-in-water double emulsion technique was adapted and applied for the preparation of PS/mildronate microparticles with total drug load up to 77 %wt and PLA/mildronate microparticles with total drug load up to 80 %wt. The repeatability of the microencapsulation process was ±4% and the encapsulation efficiency of the active ingredient reached 60 %wt. The drug release kinetics from the obtained microparticles was evaluated and it was found that drug release in vivo could be successfully sustained if polystyrene matrix has been used.

Influence of Nanoclay Additive on Mechanical Properties of Bio-Based Polyurethane Nanocomposites

This paper is about investigation of the bio-based polyurethanes from the rapeseed oil polyols and their modification with montmorillonite nanoparticles. The results of hardness and tensile properties investigation of polyurethane / montmorillonite nanocomposites are presented.

Development of Poly(vinyl alcohol) Based Systems for Wound Dressings

Poly(vinyl alcohol) hydrogels are of special interest for the application in medicine (mainly for therapeutic systems) due to their biocompatibility and excellent ability to absorb water. The water absorption of different gels prepared by freezing/thawing method was studied in the presented work.

Biodegradable Flax Fiber Reinforced Eco-Composites

Formation process of flax fiber reinforced biocomposites based on waterborne matrix systems from modified polymers - polyhydroxybutyrate, poly (vinyl alcohol) was developed by suspension casting technique. Two kind of flax fiber as reinforcement was employed Latvian variety Vega-2 and flax combing. The correlation between matrix composition, fiber origin, content and mechanical characteristics, water vapour absorption and biodegradability was established. Optimal characteristics of elaborated eco-composites were obtained by use of flax combing with fiber content ~ 30 wt. %.