"New biodegradable polymers from renewable sources. High molecular weight poly(ester carbonate)s from succinic acid and 1,3-propanediol"

High molecular weight poly(ester carbonate)s have been prepared by a two-step chain-extension reaction performed on oligomeric \u3b1,\u3c9-dihydroxy-terminated poly(1,3-propylene succinate) in turn obtained by thermal polycondensation of excess 1,3-propanediol with succinic acid. The new polymers have a biodegradable backbone and derive from renewable sources. Therefore, they have a potential as environment-friendly materials

New biodegradable polymers from renewable sources:polyester-carbonates based on 1,3-propylene-co-1,4-cyclohexanedimethylene succinate

\u3b1,\u3c9-Dihydroxy-terminated copolymeric oligomers of a 1,3-propylene/1,4-cyclohexanedimethylene succinate structure were obtained by the thermal polycondensation of 1,3-propanediol/1,4-cyclohexanedimethanol/succinic acid mixtures. They were subsequently chain-extended via phosgene synthesis to high molecular weight aliphatic/alicyclic copolyester-carbonates. These new polymers, besides having a biodegradable backbone, originate from two monomers, namely, 1,3-propanediol and succinic acid, which can be obtained by renewable sources. Therefore, they have a potential as environmentally friendly materials. All synthesized materials were characterized in reference to their molecular structure by 1H NMR and 13C NMR. Their molecular weights and molecular weight distributions were determined by size exclusion chromatography, and their main thermal properties were measured by DSC. Spectroscopic characterizations were in full agreement with the proposed structures. 1,4-Cyclohexanedimethanol was used as a diol comonomer to improve the overall thermal properties of poly(1,3-propylene succinate). The results of the characterization performed show that the initial expectations were only partially satisfied

Biodegradable polymers from renewable sources: rheological characterization of hemicellulose-based hydrogels

Hemicellulose-based hydrogels were prepared by radical polymerization of 2-hydroxyethyl methacrylate or poly(ethylene glycol) dimethacrylate with oligomeric hydrosoluble hemicellulose modified with well-defined amounts of methacrylic functions. The polymerization reaction was carried out in water at 40 \ub0C using a redox initiator system. The hydrogels were in general elastic, soft, and easily swellable in water. Their viscoelastic properties were determined by oscillatory shear measurements on 2 mm thick hydrogels under a slight compression to avoid slip, over the frequency range 10-1 to 102. The rheological characterization indicated that the elastic response of the hydrogels was stronger than the viscous response, leading to the conclusion that the hydrogel systems displayed a predominantly solidlike behavior. The curves showed an increase in shear storage modulus with increasing cross-linking density. The nature of the synthetic comonomer in the hemicellulose-based hydrogels also influenced the shear storage modulus. Comparison of hemicellulosebased hydrogels with pure poly(2-hydroxyethyl methacrylate) hydrogels showed that their behaviors were rather similar, demonstrating that the synthetic procedure made it possible to prepare hemicellulose-based hydrogels with properties similar to those of pure poly(2-hydroxyethyl methacrylate) hydrogels

Economic Evaluation of Isolation of Hemicelluloses From Process Streams From Thermomechanical Pulping of Spruce

Hemicelluloses, which are abundant in nature and have potential use in a wide variety of applications, may make an important contribution in helping relieve society of its dependence on petrochemicals. However, cost-efficient methods for the isolation of hemicelluloses are required. This article presents an economic evaluation of a full-scale process to isolate hemicelluloses from process water from a thermomechanical pulp mill. Experimental data obtained in laboratory scale were used for the scale up of the process by computer simulation. The isolation method consisted of two process steps. The suspended matter in the process water was removed by microfiltration and thereafter the hemicelluloses were concentrated by ultrafiltration, and at the same time, separated from smaller molecules and ions in the process water. The isolated hemicelluloses were intended for the production of oxygen barriers for food packaging, an application for which they have been shown to have suitable properties. The solution produced contained 30 g hemicelluloses/L with a purity (defined as the ratio between the hemicelluloses and the total solids) of approx 80%. The evaluation was performed for a plant with a daily production of 4 metric tonnes (0 of hemicelluloses, which is the estimated future need of barrier films at Tetra Pak (Lund, Sweden.). The production cost was calculated to be EURO 670/t of hemicelluloses. This is approx 9 times lower than the price of ethylene vinyl alcohol, which is produced by petrochemicals and is currently used as an oxygen barrier in fiber-based packaging materials. This indicates that it is possible to produce oxygen barriers made of hemicelluloses at a price that is competitive with the materials used today

Comparison of diafiltration and size-exclusion chromatography to recover hemicelluloses from process water from thermomechanical pulping of spruce

Hemicelluloses constitute one of the most abundant renewable resources on earth. To increase their utilization, the isolation of hemicelluloses from industrial biomass side-streams would be beneficial. A method was investigated to isolate hemicelluloses from process water from a thermomechanical pulp mill. The method consists of three steps: removal of solids by microfiltration, preconcentration of the hemicelluloses by ultrafiltration, and purification by either size-exclusion chromatography (SEC) or diafiltration. The purpose of the final purification step is to separate hemicelluloses from small oligosaccharides, monosaccharides, and salts. The ratio between galactose, glucose, and mannose in oligo- and polysaccharides after preconcentration was 0.8: 1: 2.8, which is similar to that found in galactoglucomannan. Continuous diafiltration was performed using a composite fluoro polymer membrane with cutoff of 1000 Da. After diafiltration with four diavolumes the purity of the hemicelluloses was 77% (gram oligo- and polysaccharides/gram total dissolved solids) and the recovery was 87%. Purification by SEC was performed with 5, 20, and 40% sample loadings, respectively and a flow rate of 12 or 25 mL/min (9 or 19 cm/h). The purity of hemicelluloses after SEC was approx 82%, and the recovery was above 99%. The optimal sample load and flow rate were 20% and 25 mL/min, respectively. The process water from thermomechanical pulping of spruce is inexpensive. Thus, the recovery of hemicelluloses is not of main importance. If the purity of 77%, obtained with diafiltration, is sufficient for the utilization of the hemicelluloses, diafiltration probably offers a less expensive alternative in this application

Starch and plant storage polysaccharides

The major polysaccharides from plants include starch, mannans, and xylans. These have multiple levels of structure: with starch, for example, which is a highly branched glucose polymer, one goes from the individual chains (branches), to the whole branched molecule, to crystalline and amorphous structural features, growth rings, granules. and then the whole grain. Mannans and xylans have a chemical composition as an additional structural feature. Methods of characterizing these structures are discussed and the effects of various structural features on functional properties are examined. Chemical and enzymatic modifications change these structures, and thus can be used to give improved functional properties. The characterization of the resulting structural features is essential in guiding property optimization