Liliana Rosu

FTIR and color change of the modified wood as a result of artificial light irradiation

The effect of UV-visible light irradiation on the changes in color and chemical composition of the surfaces of Abies alba L. (fir, a softwood), non-modified and chemically modified, was studied. Chemical modification of the wood was performed by reaction with succinic anhydride in xylene at different concentration values. The wood samples were irradiated in air using a rotative device equipped with a middle pressure mercury lamp. Analysis of the color changes in wood surfaces during photo-degradation was carried out by measuring CIELAB parameters. Fourier transform infrared spectroscopy was used to study chemical changes caused by light irradiation. Irradiation modified physical and chemical characteristics of wood surfaces and resulted in rapid color changes, degradation of lignin and increased content of chromophoric groups on the wood surfaces. Color changes (DeltaE(ab)) correlate well with degradation of lignin.

Thermal degradation of semi-interpenetrating polymer networks based on polyurethane and epoxy maleate of bisphenol A

Abstract Two polyurethane–epoxy maleate of bisphenol A semi-interpenetrating polymer networks were synthesized and their thermal behavior studied. The data obtained by thermogravimetry showed that the decomposition of the tested samples is complex, occurs in three steps, and depends on the degree of crosslinking. The main decomposition takes place between 290 and 480 °C, with weight losses between 62 and 66%. The apparent thermal stability of the sample synthesized with a low content of epoxy maleate of bisphenol-A (11.11 wt%) is lower compared with polyurethane, while the sample with high content of epoxy maleate of bisphenol-A (27.3 wt%) shows a higher stability.

POLYURETHANE-EPOXY MALEATE OF BISPHENOL A BLENDS

Blends of polyurethane with epoxy maleate of Bisphenol A were synthesized and their miscibility, the physico-mechanical properties, as well as the thermal behavior were studied. Differential scanning calorimetry (DSC) measurements showed a single composition-dependent glass transition temperature (Tg), and is evidence for a good miscibility of the studied systems. The variation of Tgs of the blends versus composition (Fox, Gordon-Taylor, and Schneider equations) showed the presence of some physical interactions between polyurethane and epoxy maleate polymers. Generally, the physico-mechanical properties of the blends are lower as than those of polyurethane. This suggests that epoxy maleate of Bisphenol A operates in a mixture with polyurethane only as a plasticizer. The thermal behavior of the studied blends showed no large differences to that of polyurethane.

Physico-chemical properties investigation of softwood surface after treatment with organic anhydride

AbstractWood originating from a softwood species was subjected to chemical treatment by reaction with succinic anhydride in N, N-dimethylformamide at different concentration values. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis were used to study changes that occurred on a softwood surface. The extent of chemical treatment on softwood was evaluated by determining the weight percent gain values. Thermal properties of modified softwood and the water absorption were also evaluated. The chemical treatment with succinic anhydride influenced the thermal stability of the softwood samples with increasing anhydride concentration levels.

Multicomponent Polymer Materials: Photodegradation Mechanism

The chapter follows two pathways into polymer photodegradation. The first one consists of an introduction into the obtaining of photodegradable polymers by inserting several photolabile entities, such as o-nitrobenzyl, coumarin-4-ylmethyl, p-hydroxyphenacyl or acetal, with emphasis on the o-nitrobenzyl group. The second and main pathway of the chapter encompasses literature studies related to photochemical decomposition mechanisms occurring in different types of multicomponent polymer systems. UV radiations, oxygen, temperature and humidity represent the main driving forces in polymer irreversible photochemical deterioration, occurring through radical intermediates (hydroperoxides, chromophore carbonyl groups or conjugated double bonds) as chained mechanisms.

Thermal Degradation of Thermosetting Blends

The chapter coalesces literature studies on recent advances concerning the thermal behavior of different thermosetting blends. The introduction debates the general issue concerning polymer blends, that being the occurrence of phase separation phenomena and lists a series of possibilities to overcome these undesired aspects. The introduction section also presents the most common polymers used as crosslinked scaffolds either individual or for different multicomponent polymeric materials. The subchapters that follow are focused on recent studies on the thermal stability and degradation of thermosetting blends, effect of reinforcement and nanofillers on the thermal stability of thermosetting blends and applications and future trends of thermosetting blends, dealing with the latest issues and trying to reveal solutions.

Theoretical Aspects Regarding Polymer Photochemistry

The chapter encompasses literature studies related to the basic photochemical decomposition processes occurring in polymers. Ultraviolet (UV) radiations from light, oxygen from air, temperature and humidity are the main factors producing chemical and/or physical irreversible damages in polymers. UVA radiations (λ = 315–400 nm) possess sufficiently high energy for generating most macromolecular chain bonds cleavage leading to initiation of important chemical modifications through radical intermediates such as oxides and hydroperoxides, chromophore carbonyl groups or conjugated double bonds. The presence of oxygen leads to occurrence of photo-oxidative processes through chained mechanisms.

Life-Time Prediction of Multicomponent Polymeric Materials

Since the continuous emerging of new technologies and outdoor applications of polymers and polymer based materials, and thus a dire need in increasing their lifetime service quality, the number of methods predicting aging has also experienced growth. Most of such methods are reported on natural and artificial aging and may be based on accelerated aging predictions, different damage models and empirical formulas. The present chapter is a systematization of literature studies focused on discovering new means for accurate linking of laboratory and field exposure results, which represent the actual and future main challenges in estimating and assessing quality and service lifetime of polymeric materials.

Synthesis and characterization of some composites with bioactive properties on the basis of vinyl ester resins

Abstract Vinyl ester resins are unsaturated polyesters, widely used as matrix for high performance composite materials. The paper presents the synthesis and characterization of some vinyl ester resin/hydroxyapatite bioactive compositions using an unsaturated copolyester based on turpentine oil as reactive diluent. The vinyl ester oligomer /unsaturated copolyester/hydroxyapatite structural complex was characterized from the morphological point of view, water absorbtion, density measurements and volume contraction. The water uptake is dependent on the concentration in vinyl ester resin. The increase of the vinyl ester resin content in the bioactive composite leads to the increase of the density, respectively to a significant decrease of the volume contraction