Silvia Patachia

Study of the compatibility in the poly (vinyl-chloride) -poly (vinyl-alcohol) system

SummaryAlthough poly (vinyl-chloride) — PVC — and poly (vinyl-alcohol) — PVA —mixtures are used in practice for coatings, containers, fibers, few studies are encounterd concerning their compatibility (7, 8).This paper establishes both the optimum compatibility ratio and the thermal behaviour of the mixtures.The compatibility study in solid state was realised using the methodes: optical microscopy, thermogravimetry, DSC, inverse gaschromatography and IR spectroscopy.

Effect of TiO2 Addition on the Properties of Macro Defect Free Cement-Polymer Composites

Macro-defect free (MDF) cement is a cement-polymer composite with superior flexural strength although produced by mixing cement with small amounts of polymer and water. Special production technique and the crosslinking occurred between cement and polymer are important factors for obtaining such high strengths. However, MDFs lose considerable strength when exposed to water. The objective of this study was to explore the effects of TiO2 addition on flexural strength and water sensitivity of MDF. In this study, MDF cements were produced by adding up to 4 % TiO2 by weight of cement. Biaxial flexural test as well as Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) tests were conducted in order to investigate the effect of TiO2 addition. TiO2 addition improved the water resistance of MDF cements in some batches, especially with 2 % addition possibly due to the CPVA–O–Ti–O–CPVA bond and this cross-linking mechanism together with CPVA–O–Al–O–CPVA bonds cause a more stable polymer network.

Long-Chain Alkylimidazolium Ionic Liquid Functionalization of Cellulose Nanofibers and Their Embedding in HDPE Matrix

This paper presents a possible alternative to traditional cellulose nanofibers functionalization, by treatment of the material at low temperatures (25–35°C) with electron-beam irradiated 1-hexyl-3-methylimidazolium chloride ionic liquid. The treatment promotes decreasing the crystallinity of the cellulose with up to 45% and possible imidazolium moieties grafting to cellulose, as demonstrated from FTIR, XRD, and elemental analysis. The grafting determines water vapors uptake values with 50–70% lower and water vapors uptake rate with 50% lower than those of reference cellulose nanofibers. The grafting determined also improved adhesion of the cellulose nanofibers to HDPE, thus contributing to the obtaining of polymer matrix composites with improved properties.

Effect of Epoxy Resin Addition on the Moisture Sensitivity of Macro Defect Free Polymer-Cement Composites

Macro-defect-free (MDF) cements are cement-polymer composites and were developed by Birchall et al. three decades ago. The composites are produced by mixing small amounts of polymer and water with cement. However, they have a different production method than that of cement pastes, which was inspired by rubber production. Mixtures of cement, polymer and water are processed by using a two-roll mill. The composites are known with their high flexural strengths. Unfortunately, there are not any known commercial products using MDF cements because of their poor durability under moisture. In this study, MDF cements were prepared by using poly(vinyl alcohol--vinyl acetate) PVA, calcium aluminate cements and two different types of epoxy resins. Epoxy resins were a diglycidyl ether of bisphenol A and a mixture of a diglycidyl ethers of bisphenol A and F. Durability performance was compared with respect to biaxial flexural strengths, contact angle and atomic force microscopy (AFM) for the specimens stored in water.

Biocomposites obtained from wood saw dust using ionic liquids

Abstract The paper presents a new method of wood composites obtaining, as a potential alternative to traditional non-ecological processes involving the use of phenol-based resins. The novelty of the method consists in using only two components, namely wood and an alkylimidazolium chloride ionic liquid. A fraction of wood sawdust dissolves in the ionic liquid, and by water addition it precipitates, acting as a natural binder for the remaining wood particles. FTIR and XRD spectroscopy analysis confirmed the presence of the dominating amorphous cellulose II anomer in the structure of the wood composites. By comparing to the reference, the obtained composites present lower wettability and higher resistance to compression

State of the art of macro-defect-free composites

Macro-defect-free (MDF) composites, developed and patented by scientists from Imperial Chemical Industries in the early 1980s, are very high strength cement–polymer composites. The preparation of MDF composites is different from the production of conventional cement paste in that high shearing with a roller mill as well as moderate pressure (about 5xa0MPa) and moderate temperature (about 80–100xa0°C) are applied during the production. Very low water/cement ratio (w/c) levels are achieved (as low as 0.10) in this composite, much lower than in other cement-based materials. Of the many unique properties exhibited by MDF composites, surely the most remarkable is their high flexural strength. This is generally attributed to their low porosity and to cross-linking reactions between cement and polymer. MDF composites may reach a flexural strength of 200–300xa0MPa levels, whereas ordinary cement pastes have generally around 5–10xa0MPa. However, serious durability problems are observed in MDF composites, particularly their significant reductions in strength when immersed in water. Comprehensive information about MDF composite research will help in understanding the reasons behind the high strength, microstructure and water sensitivity of MDF composites. This review summarizes the materials, production methods, properties, microstructure, hydration reactions, durability and potential application areas of MDF composites as published since 1981.

New Method of Wood Impregnation with Inorganic Compounds Using Ethyl Methylimidazolium Chloride as Carrier

In this paper, a novel method for wood surface impregnation with inorganic compounds, such as titanium dioxide, wolfram trioxide, and calcium metasilicate, using an alkylimidazolium ionic liquid as solvent-carrier is presented. The aforementioned compounds are able to diffuse into the wood surface and form an even coating that provides higher dimensional stability in wood as well as higher Brinell hardness as compared to non-impregnated materials. The main advantage of the proposed method of impregnation is the use of an eco-friendly ionic liquid, avoiding volatile organic compounds. In addition, the process saves time and energy, as it is faster and requires considerably lower temperatures (40°C as compared to 100–200°C with conventional processes of impregnation).

EFFICIENCY OF THE POLY (VINYL ALCOHOL) (PVA) HYDROGELS AS SOIL CONDITIONER, DETERMINED BY MONITORING THE CAPSICUM SP. L. GROWTH

This study revealed that the poly (vinyl alcohol) hydrogel [PVA] inserted into the soil prolonged its ionic activity. To prove the influence of the PVA hydrogels on the plants growth, Capsicum annuum L. has been used as model plant to monitor the photosynthesis, respiration processes and also the morphological parameters. PVA hydrogels determined the intensification of all physiological processes of the plant. It could be concluded that PVA hydrogel is an ecological material able to influence the soil quality by controlled release of initially absorbed water, improving the plants quality.