Effect of poly (ethylene-co-vinyl acetate) grade on water resistance and mechanical properties of particleboard

Three-layer particleboard was prepared in the laboratory using a similar composition and processing condition to those used in the plant production of particleboard. Poly(ethylene-co-vinyl acetate) (EVA) was mixed with natural rubber-wood particles in the core layer to reduce the water resistance of the particleboard. The properties of three EVA grades with vinyl acetate contents of 19%, 22%, and 28% were melt indexes of 530, 1.8, and 6.8 g/10 min, melting temperatures of 84, 86, and 75 °C, and molecular weights of 29000, 68000, and 61000 g/mol, respectively. The addition of 5% EVA significantly decreased the thickness swelling and water absorption properties of the particleboard. The mechanical properties of the particleboard that were determined were the modulus of rupture, modulus of elasticity, internal bond strength, and screw holding force. A statistical analysis of the data showed that the addition of 5% EVA did not deteriorate the mechanical properties. EVA22 seemed to be the optimal grade

Biodegradation of a blended starch/natural rubber foam biopolymer and rubber gloves by Streptomyces coelicolor CH13

Background: The growing problem of environmental pollution caused by synthetic plastics has led to the search for alternative materials such as biodegradable plastics. Of the biopolymers presently under development, starch/natural rubber is one promising alternative. Several species of bacteria and fungi are capable of degrading natural rubber and many can degrade starch. Results: Streptomyces coelicolor CH13 was isolated from soil according to its ability to produce translucent halos on a mineral salts medium, MSM, supplemented with natural rubber and to degrade starch. Scanning electron microscope studies showed that it colonized the surfaces of strips of a new starch/natural rubber biopolymer and rubber gloves and caused degradation by forming holes, and surface degradation. Starch was completely removed and polyisoprene chains were broken down to produce aldehyde and/or carbonyl groups. After 6 weeks of cultivation with strips of the polymers in MSM, S. coelicolor CH13 reduced the weight of the starch/NR biopolymer by 92% and that of the rubber gloves by 14.3%. Conclusions: This study indicated that this bacterium causes the biodegradation of the new biopolymer and natural rubber and confirms that this new biopolymer can be degraded in the environment and would be suitable as a \u2018green plastic\u2019 derived from natural sources

Synthesis and characteristics of α-carboxylic, ω-hydroxyl natural rubber toughened poly(lactic acid)

This work presented the synthesis of α-carboxyl, ω-hydroxyl natural rubber (CHNR) for use as an alternative toughening agent for poly(lactic acid) (PLA). The proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FTIR) analyses verified the chemical structure of CHNR consisting of the hydroxyl and carboxyl end groups. The molecular weights of CHNR were set from 5000 to 15 000 g·mol–1 which were determined by gel permeation chromatography (GPC) and 1H-NMR. The PLA and CHNR were prepared by reactive blending using a twinscrew extruder. It was found that the reaction between PLA and CHNR proceeded through transesterification without a catalyst. The formation of copolymer (PLA-co-CHNR) at the interface of PLA and CHNR increased the interfacial adhesion between the two phases. Differential scanning calorimetry (DSC) analysis revealed that CHNR was more compatible with PLA than natural rubber (NR). The compatibilization affected the blend morphology by reducing the interfacial tension. It resulted in a reduction of rubber particle size. The CHNR with a molecular weight of 5000 g·mol–1 showed the greatest improvement in the toughness and ductility of PLA

Synthèse et étude des propriétés d un polyuréthane biosourcé obtenu du caoutchouc naturel et du poly( -caprolactone)

L objectif de ce travail de thèse était la synthèse d un nouveau matériau polyuréthane biorsourcé composé par du caoutchouc naturel modifié chimiquement et par du poly( -caprolactone), (PCL), en présence ou absence d isocyanates. Des oligoisoprènes téléchéliques hydroxylés (HTNR) ont été obtenus après époxidation du caoutchouc naturel et réduction des oligomères carbonyles. Plusieurs paramètres ont été étudiés comme la nature et la quantité relative de diisocyanate, le rapport molaire entre diisocyanate et diol (NCO:OH), l influence de la masse molaire des diols HTNR et PCL, le pourcentage de 1,4-butane diol (BDO, extenseur de chaîne), et le rapport molaire entre les diols HTNR:PCL. Trois types de diisocyanate ont été employés : isophorone diisocyanate (IPDI), toluène-2,4-diisocyanate (TDI) et hexaméthylène diisocyanate (HDI). Masses molaires différentes ont été utilisées pour les diols HTNR et PCL: 1700, 2800 et 2900 g/mol pour HTNR et 530 et 2000 g/mol pour PCL. Le rapport molaire entre NCO:OH était entre 0,75:1,00 2,85:1,00. Les PU ont été préparés par la méthode one shot et les structures chimiques des HTNR et PU ont été identifiées par 1H-NMR et FTIR. La résistance à la traction et à la rupture ont été étudiées. La caractérisation a été conduite par DSC, DMTA, ATG et spectroscopie Raman. Une étude préliminaire a montré que la masse molaire du PU augmentait avec le rapport NCO:OH et le temps de réaction, et que le chloroforme n était pas un bon solvant pour obtenir des films. Le tetrahydrofurane était le solvant le plus approprié et il a été utilisé par la suite pour toutes les polymérisations. Le rapport NCO:OH = 1,25:1,00 s est révélé optimal pour obtenir des films. L analyse FTIR a permis de vérifier la présence de liaisons uréthane, de points de réticulation et de branchements. Le polyuréthane a montré des propriétés mécaniques excellentes dépendantes de la composition chimique. Si on exclue l utilisation de PCL2000 et de HDI, le comportement à la traction était caractéristique des élastomères. Les PU étaient amorphes sauf lorsque le HDI a été employé. Duos ce cos été obtenais un PU semi cristallin. Cette cristallinité augmente le module de Young, la résistance à la rupture, la dureté et la stabilité thermique du PU. Pour ce PU ont observé une séparation de phase entre les segments du PCL et du HTNR. Les chaînes plus longues et plus flexibles du HTNR et leur non polarité sont responsables de la diminution des propriétés mécaniques et des températures de transition. Le materiae pane d un comportement élastomère a un comportement plastique pour un rapport NCO:OH élevé (2,85 :1,00). Le dégréé de réticulation élevé a été retenu comme la cause pour laquelle il n y avait pas de séparation de phase entre les segments souples et durs. La liaison hydrogène entre le diol PCL et le segment hard a généré des Tg élevées. Les spectres Raman ont montré la formation de la liaison uréthane du PU contenant différents diisocyanates. La synthèse de PU sans diisocyanate a été obtenue grâce à une réaction de polyaddition entre des carbonates cycliques téléchéliques dérivés du PCL et du caoutchouc naturel, et la 1,4-butylène diamine. Les structures contenant des carbonates cycliques ont été obtenues grâce à la modification des groupes OH sur le HTNR et le PCL à groupes carboxyle, utilisant l anhydride succinique, et a la réaction successive avec le glycérol carbonate.The aim of this research work was to prepare a novel bio-based polyurethane (PU) composed by chemically modified natural rubber (NR) and poly( -caprolactone) diol (PCL), with and without isocyanate. Hydroxyl telechelic natural rubber (HTNR) was synthesized via epoxidized and carbonyl telechelic natural rubber. The parameters studied included type and relative amount of diisocyanate, molar ratio between diisocyante and diol (NCO:OH), molecular weight of HTNR and PCL diol, 1,4-butane diol (BDO, chain extender) content and molar ratio between HTNR:PCL diols. Three types of diisocyanate were employed: isophorone diisocyanate (IPDI), toluene-2,4-diisocyanate (TDI) and hexamethylene diisocyanate (HDI). The number average molecular weights of HTNR and PCL diol were selected: 1700, 2800 and 2900 g/mol for HTNR and 530 and 2000 g/mol for PCL diol. The NCO:OH molar ratio was in the range 0.75:1.00 2.85:1.00. PU was prepared by one-shot method. The chemical structure of HTNR, PCL and PU were identified by 1H-NMR FTIR and Raman spectroscopy. Tensile properties and tear resistance of PU were investigated. Characterization of mechanical and thermal properties was carried out using DSC, DMTA and TGA. A preliminary study showed that the molecular weight of PU increased with increasing NCO:OH molar ratio and reaction time, and chloroform was not a good solvent for polymer casting. Tetrahydrofuran was an appropriate solvent as it allowed film formation and it was used in all the other experiments. The NCO:OH molar ratio of 1.25:1.00 was suitable for preparing good PU films. FTIR analysis verified the presence of urethane linkages and crosslinking or chain branching. PU demonstrated excellent mechanical properties, which depended on the chemical composition. Excluding the use of PCL2000 and HDI, the tensile behavior seemed to have typical elastomeric characteristics. PU became amorphous except in the case of HDI, which was able to crystallize leading to the crystalline PU. The crystallinity increased the Young s modulus, the tear strength, the hardness and the thermal stability of PU. PU showed a phase separation between the PCL and HTNR segments. The longer and more flexible chain and non-polarity of HTNR were responsible of a decrease of the mechanical properties and transition temperatures. The very high molar ratio of NCO:OH (2.85:1.00) changed the tensile characteristics from an elastomer to a plastic. The high crosslinking was attributed to there being no phase separation between the hard and the soft segment. Hydrogen bonding between the PCL diol and the hard segment produced a high Tg. Raman spectra were able to identify the urethane linkage of PU containing different diisocyanates by showing the relative absorbance peaks. Synthesis of PU without isocyanate was successfully obtained via a polyaddition polymerization between a cyclic carbonate telechelic PCL/NR and 1,4-butylenediamine. The cyclic carbonate telechelic NR and cyclic carbonate telechelic PCL were prepared via the modification of the hydroxyl end groups of HTNR and PCL diols to carboxylic acid end groups by reacting with succinic anhydride. Then, the carboxylic acid end groups were changed to the cyclic carbonate end groups by using glycerol carbonate.LE MANS-BU Sciences (721812109) / SudocSudocFranceF

Effects of different epoxidation methods of soybean oil on the characteristics of acrylated epoxidized soybean oil-co-poly(methyl methacrylate) copolymer

The effect of the type of epoxidation processes of soybean oil on the characteristics of epoxidized soybean oils(ESOs), acrylated epoxidized soybean oils (AESOs), and acrylated epoxidized soybean oil – poly(methyl metacrylate) copolymers (AESO-co-PMMA) has been investigated. Two epoxidation processes were used: an in situ chemical epoxidation using hydrogen peroxide and formic acid, and a chemo-enzymatic epoxidation using 2 enzymes: Novozyme® 435 (CALB) and a homemade lipase/acyltransferase (CpLIP2). ESOs containing different numbers of epoxide groups/molecule were synthesized. A commercial ESO (Vikoflex® 7170) was employed and it had the highest number of epoxide groups. Acrylation of ESOs was carried out using acrylic acid, and copolymerized with a methyl methacrylate monomer. The chemo-enzymatic epoxidation produced high acid value, particularly from the CpLIP2 (!46–48%) and indicated the formation of epoxidized free fatty acids. In contrast, the ESO synthesized from the chemical epoxidation showed a very low acid value, < 0.6%. The AESOs synthesized from the CALB-based ESO and the chemical-based ESO showed a similar number of acrylate groups/molecule while that from the CpLIP2-based ESO showed a very low number of acrylate groups because the carboxylic groups from the epoxidized free fatty acids impeded the acrylation reaction. The lower the number of acrylate groups the lower was the crosslink density, the Tg, and the gel content in the AESO-co-PMMA copolymer