Synthesis and properties of composites of starch and chemically modified natural rubber

A means is developed for forming polysaccharide-based composites with useful material properties through use of unmodified and chemically modified natural rubber latex (NRL). Starch was used as a model for polysaccharides. The NRL was modified by grafting with dimethylaminoethyl methacrylate (DMAEMA) to form a latex with cationic water-soluble polymeric “hairs” of polyDMAEMA, which should form hydrogen bonds with starch. Starch solutions, containing 20% glycerol as a film-forming aid, and the modified NRL were mixed and films allowed to form. The unmodified latex acted only as filler in the starch films, but with modified NRL, the mechanical properties of the films were significantly altered. The elastic modulus was greatly decreased and strain at break greatly increased. The glass transition temperature increased from –48°C to –32°C, suggesting significant compatibilization. Freeze-fracture TEM micrographs indicate strong interactions between the surface of the modified NRL and starch. The polyDMAEMA chains are more hydrophilic than the starch, and the addition of grafted latex results in a 20° drop of the water contact angle of the formed film, and a 25% increase of the water absorption compared to the native starch; with unmodified NRL, the opposite effect was observed

Thermo-mechanical processing of sugar beet pulp. I. Twin-screw extrusion process

Sugar beet pulp (SBP) is the raffinate of sugar extraction. Composed of empty vegetal cells, three quarters of it consist of polysaccharides. As it is cheap and produced in great quantities SBP is a potential raw material for industrial applications other than cattle feeding. Twin-screw extrusion modified its structure and destructuring level depended on the specific mechanical energy provided (SME). By gradually increasing this energy, the rate of soluble matter increased, cell structure was progressively destroyed and SBP rheological behaviour was modified. For an SME of 745 W h kg-1, SBP examined through a scanning electron microscope showed a structure similar to that of a composite formed by a continued matrix consisting mainly of pectin and hemicelluloses filled with cellulose microfibres. Plasticized SBP was then formed by injection-molding. Thus treated, SBP becomes a cheap alternative to the use of thermoplastic starch for the production of biodegradable materials

Thermo-mechanical processing of sugar beet pulp. II. Thermal and rheological properties of thermoplastic SBP

Thermoplastic properties of extruded sugar beet pulp (SBP) are closely linked to water–polymer relationships. DSC analyses of water evaporation, water fusion and biopolymer relaxation according to SBP moisture content gave a more accurate estimation of SBP hydration steps than classical water adsorption isotherm. Three moisture contents (8%, 26%, 41% db) were then defined as limits of the different hydration behaviours. Melt viscosity measurements of SBP showed its shear thinning behaviour and the measured apparent viscosity is in the same range as thermoplastic starch viscosity. Using only water as plasticizer, to one temperature corresponded one moisture content to reach the optimal flowing properties: 110°C/35%, 120°C/25% and 130°C/20%. This "plasticization" temperature has been estimated through DSC measurements of large amounts of moistened SBP in pressure-resistant pans. This new kind of DSC measurement revealed a new sample mass dependent second order transition between 140 and 180°C, which temperature is linearly linked to the sample mass

Thermo-mechanical processing of sugar beet pulp. III. Study of extruded films improvement with various plasticizers and cross-linkers

Thermoplastic sugar beet pulp (thermo-mechanical processing was discussed in previous studies) was formed into film strips by extrusion. Film tensile properties are discussed according to the molecular structure of external plasticizer. Sorbitol, fructose and adipic acid have a marked antiplasticizing effect, while urea and xylitol gave higher ultimate tensile stress than glycerol for a comparable strain at break. Xylitol can be considered as the best plasticizer with UTS and EL of, respectively, 4.9 MPa and 11.3% and water absorption (85%RH, 25°C) was less than 25%. Glycidyl methacrylate was directly used in the extrusion process as cross-linker. In high humidity atmosphere (97%RH, 25°C), film water absorption was then kept under 40% while the tensile properties were improved of 50% and with a 30 minute UV post-treatment the mass gain in absorption was even less than 30% after 5 days

Relevance of lab-scale conical twin-screw extruder for thermoplastic STARCH/PLA blends rheology study

During the last decade, thermoplastic starch (TPS) has been studied more and more, alone and in blends. One key property of TPS is its viscosity. A lab-scale conical twin-screw extruder has been used to process polymers or blends of polymers at a small scale (7 cm3), and to measure their viscosity by pressure loss in a backflow channel. TPS has been tested at different temperatures (100-180°C) and for a 100-900s-1 shear rate range. One surprising result is the viscosity evolution of starch/glycerol blends (supposed to have become TPS before the rheology measurements) with temperature. An increase is observed between 120 and 140°C and then it decreases between 140 and 160°C. Therefore plasticization may happen only from 140°C. Blends of TPS with PLA and with different additives have also been studied. The additives are introduced in a second time, ten minutes after the TPS/PLA blend recirculation. Their influence on the blend viscosity is instantaneous. A viscosity increase after the additive introduction can be a clue for an improvement of the blend compatibilisation, as observed with CMC. Thanks to this micro-compounder, viscosity and behaviour of polymers can be evaluated easily even for TPS which needs shear to flow. Moreover, the solidified sample collected in the backflow channel at the end of the experiment can be used to test different properties like mechanical or thermal (DMTA, DSC) ones. Using this kind of lab-scale extruder represents then a good opportunity for preview screening studies

Characterization of Non-Derivatized Cellulose Samples by Size Exclusion Chromatography in Tetrabutylammonium Fluoride/Dimethylsulfoxide (TBAF/DMSO)

International audienceThis paper deals with the use of tetrabutylammonium fluoride/dimethylsulfoxide (TBAF/DMSO) to characterize the molar mass distribution of non-derivatized cellulosic samples by size exclusion chromatography (SEC). Different cellulose samples with various average degree of polymerization (DP) were first solubilized in this solvent system, with increasing TBAF rates, and then analyzed by SEC coupled to a refractive index detector (RID), using DMSO as mobile phase. The Molar Masses (MM) obtained by conventional calibration were then discussed and compared with suppliers’ data and MM determined by viscosimetry measurements. By this non-classic method, molar mass of low DP samples (Avicel® and cotton fibers) have been determined. For high DP samples (α-cellulose and Vitacel®), dissolution with TBAF concentration of 10 mg/mL involved elution of cellulose aggregates in the exclusion volume, related to an incomplete dissolution or the dilution of TBAF molecules in elution solvent, preventing the correct evaluation of their molar mass

Matériau composite à base de matière naturelle lignocellulosique

L'invention concerne un matériau composite à base de particules d'une matière naturelle lignocellulosique, notamment de bois. Ces particules sont dispersées dans une matrice d'un polymère thermoplastique choisi parmi les polyamides et les copolymères à blocs comprenant au moins un bloc polyamide. Un procédé de préparation de ce matériau composite comprend le mélange desdites particules et dudit polymère thermoplastique et la mise en forme de ce mélange

The properties of cellulose insulation applied via the wet spray process

Cellulose fibre insulation is a sustainable thermal insulation material made out of recycled paper. It can be installed in open walled cavities using the wet spray method. The isotherm of loose cellulose insulation fibres was determined using dynamic vapour sorption to study their relationship with water. The types of water within the fibres, known as bound and unbound water was studied via a differential scanning calorimetry method. Wet spray cellulose samples were produced with varying water content and subjected to compression, and thermal conductivity testing. Results showed that density, modulus of elasticity, and thermal conductivity all increased with water dosage. The increase in these properties was higher when the material was sprayed with water than when it was dry compacted. These are factors which need to be considered for when applying wet-spray cellulose fibre insulation, in order to ensure the properties of the material are consisten

Influence of flax fibers on network formation of DGEBA/DETA matrix

Natural fibers and particularly flax fibers have a great potential to replace glass fibers in composite materials. However, the interaction between these fibers and thermoset matrices remains unclear and results in a weak interface affecting the mechanical properties of the composite. This study was carried out to investigate the impact of natural fibers on the chemical reaction between the resin and the hardener, studying the interaction of fibers with each component separately to understand more precisely the phenomena involved. The results show that the contact with the fibers involves a change of the matrix properties that has been attributed to the water absorbed on their surface. On the one hand, water could modify amine functions of the hardener leading to a decrease of 40°C of matrix glass transition temperature (Tg). This issue could be corrected by adding a 16% excess of hardener. On the other hand, the water added to the resin could also accelerate the epoxide/amine reaction increasing slightly the Tg of the matrix and also generating weaker distinct networks of lower Tg by post-modification of the hardener. Therefore, the control of the water content in flax fibers is a crucial parameter for composite manufacturing

A review on the properties of cellulose fibre insulation

The building sector is constantly innovating in its use of materials with regards to sustainability. There is a need to use cost effective, environmentally friendly materials and technologies which lessen the impact of a construction in terms of its use of non-renewable resources and energy consumption. Cellulose fibre insulation is an eco-friendly thermal insulation material made from recycled paper fibres. It offers good thermal properties and has a low embodied energy. However due to lack of expertise in its application and properties, cellulose insulation is not widely used in comparison to more traditional insulation materials. The present paper reviews the available research on cellulose fibre insulation, its manufacture, installation, and performance. The paper focuses the physical properties of cellulose insulation, the environmental factors that affect these properties, and possible means of future innovation