Sorghum Fiber Research Articles

Utilization of sweet sorghum fiber to reinforce fly ash-based geopolymer

Geopolymer has been of great research interest as a material for sustainable development. As ordinary Portland cement, however, geopolymer exhibits brittle behavior with low tensile strength, ductility, and fracture toughness. This paper investigates the reinforcement of fly ash-based geopolymer with alkali-pretreated sweet sorghum fiber. The sweet sorghum fiber comes from the bagasse (residue), a waste after the juice is extracted from sweet sorghum stalks for ethanol production. Specifically, the unit weight of fly ash-based geopolymer specimens containing different contents of sweet sorghum fibers was measured. Unconfined compression, splitting tensile, and flexural tests were conducted to investigate the effect of incorporated sweet sorghum fiber on the mechanical properties of fly ash-based geopolymer. Scanning electron microscopy imaging was also performed to study the microstructure of the sweet sorghum fiber–geopolymer composite. The results indicate that the unit weight of the sweet sorghum fiber–geopolymer composite decreases with higher fiber content. Although the inclusion of sweet sorghum fiber slightly decreases the unconfined compressive strength, the splitting tensile, and flexural strengths as well as the post-peak toughness increase with the fiber content up to 2 % and then start to decrease. The splitting tensile tests also clearly show the transition from the brittle failure of the plain geopolymer specimen to the “ductile” failure of the geopolymer specimen containing sweet sorghum fiber.

Effects of Natural Fiber Surface Modification on Mechanical Properties of Poly(lactic acid) (PLA)/Sweet Sorghum Fiber Composites

We describe how poly(lactic acid)/sweet sorghum fiber composites were made by melt compounding and compression molding. Four different kinds of surface treating agents (amino silicone oil (ASO), silane coupling agent (SCA), emulsified wax (EW) and titanate coupling agent (TCA)) were used to modify the natural fiber surface to reduce hydrophilicity. Fourier Transform Infrared Spectroscopy and X-Ray Photoelectron Spectroscopy data indicated that the SSF surfaces were successfully covered by treating agents. And the hydrophilic property of modified fiber characterized by the contact angle measurements. With the test of mechanical properties, PLA/TCA-F composite showed the maximum flexural strength, 60 MPa, which is 63% than that of the control. Fourier Transform Infrared Spectroscopy data indicated that the chemical reaction between TCA-F and PLA matrix played a prominent role in the high mechanical properties of PLA/TCA-F composites.

Studies of different kinds of fiber pretreating on the properties of PLA/sweet sorghum fiber composites

AbstractIn this article, truly degradable composites were prepared using sweet sorghum fibers which are residue of ethanol fermentation industry as reinforcement and renewable resource‐based biodegradable polyester, poly(L‐lactide) (PLLA) as matrix, they were fabricated by melt‐blending. The effect of different kinds of pretreatments (dilute sulfuric acid pretreatment, mild alkaline/oxidative pretreatment, steam explosion pretreatment) on mechanical properties of composites were investigated. Besides the composition of untreated and treated fibers as determined by Van soest method, Fourier transformed infrared (FTIR) spectroscopic and scanning electron microscopic (SEM) were also used to study the change of sweet sorghum fibers before and after pretreatments. Mechanical properties testing indicated that tensile strength and impact strength of PLLA/treated fibers were improved except the dilute sulfuric acid pretreated fibers reinforced PLA composite. The mild alkaline/oxidative pretreated fiber reinforced PLA composite showed highest tensile strength of 46.12 MPa and impact strength of 8.02 kJ/m2 which was 15.5 and 33% higher than that of the control. The SEM of impact fracture surface and DMTA test were carried out to investigate the interfacial morphology and interfacial adhesion between the fiber and matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Dilute Ammonia Pretreatment of Sorghum and Its Effectiveness on Enzyme Hydrolysis and Ethanol Fermentation

A new pretreatment technology using dilute ammonium hydroxide was evaluated for ethanol production on sorghum. Sorghum fibers, ammonia, and water at a ratio of 1:0.14:8 were heated to 160 degrees C and held for 1 h under 140-160 psi pressure. Approximately, 44% lignin and 35% hemicellulose were removed during the process. Hydrolysis of untreated and dilute ammonia pretreated fibers was carried out at 10% dry solids at an enzyme concentration of 60 FPU Spezyme CP and 64 CBU Novozyme 188/g glucan. Cellulose digestibility was higher (84%) for ammonia pretreated sorghum as compared to untreated sorghum (38%). Fermentations with Saccharomyces cerevisiae D(5)A resulted in 24 g ethanol /100 g dry biomass for dilute ammonia pretreated sorghum and 9 g ethanol /100 g dry biomass for untreated sorghum.

Ethanol production from sorghum by a dilute ammonia pretreatment

Sorghum fibers were pretreated with ammonium hydroxide and the effectiveness of the pretreatment evaluated by enzyme hydrolysis and ethanol production. The treatment was carried out by mixing sorghum fibers, ammonia, and water at a ratio of 1:0.14:8 at 160 degrees C for 1 h under 140-160 psi pressure. Approximately 44% lignin and 35% hemicellulose were removed during the process. Untreated and dilute-ammonia-treated fibers at 10% dry solids were hydrolyzed using combinations of commercially available enzymes, Spezyme CP and Novozyme 188. Enzyme combinations were tested at full strength (60 FPU Spezyme CP and 64 CBU Novozyme 188/g glucan) and at half strength (30 FPU Spezyme CP and 32 CBU Novozyme 188/g glucan). Biomass enzyme hydrolysis was conducted for 24 h. Saccharomyces cerevisiae D(5)A was added post hydrolysis for conversion of glucose to ethanol. Theoretical cellulose yields for treated biomass were 84% and 73%, and hemicellulose yields were 73% and 55% for full strength and half strength, respectively. Average cellulose yield was 38% and hemicellulose yield was 14.5% for untreated biomass. Ethanol yields were 25 g/100 g dry biomass and 21 g/100 g dry biomass for full strength and half strength enzyme concentrations, respectively. Controls averaged 10 g ethanol/100 g dry biomass.

Structure and Properties of Natural Cellulose Fibers Obtained from Sorghum Leaves and Stems

For the first time, sorghum leaves and stems have been used to produce natural cellulose fibers with properties suitable for composite, textile, and other high-value fibrous applications. The leaf and stems fibers produced are multicellular and have similar cellulose contents. The breaking tenacity and elongation of the fibers are similar to that of natural cellulose fibers such as kenaf and cornstalk fibers. However, the sorghum fibers have a modulus of about 113 g/denier (15 GPa) similar to the modulus of cornstalk fibers but higher than that of cotton and cornhusk fibers. At least 7 million tons of natural cellulose fibers can be produced by using the sorghum stems and leaves available as byproducts every year. Using the sorghum byproducts as a source for cellulose fibers will help to add value to the sorghum crops and also make the fiber industry more sustainable.

Fermentation of dietary fibre in the intestinal tract of rats — a comparison of flours with different extraction rates from six cereals

The fermentation of dietary fibre in wheat, rye, barley, sorghum, rice and maize was investigated in balance experiments with rats. Two different extraction rates, 100% and approximately 65%, were investigated for each cereal grain. In the case of maize, whole maize, and dehulled maize that had been ground and sieved so that it contained mainly endosperm, were investigated. Except for sorghum, dietary fibre in low-extraction flours was fermented to a greater extent than that in whole-grain flours. The sugar monomer compositions of the fibres at low and high extraction rates were similar for wheat and rye, but their susceptibilities to fermentation by bacterial enzymes were quite different. This indicates that a high proportion of soluble fibre and a low content of lignin improves the fermentability of the fibre. Further, barley, rice and sorghum fibre in refined flours, all of which consisted mainly of non-lignified glucans, were fermented more extensively when the proportion of soluble fibre was high. Addition of cellulose to diets containing wheat flour did not change the susceptibility of the wheat fibre to bacterial fermentation. Starch was demonstrated in faeces from rats fed wheat, sorghum and whole-grain rye flours. This starch represented 17–61 % of the total faecal glucan, but constituted less than 1% of the starch intake.

Utilising Woody Fibre from Agricultural Crops

SUMMARY The pulping and papermaking properties of some non-wood crops are reviewed and compared with conventional pulpwood species. Pulping trials have been made on Australian grown kenaf (Hibiscus cannabinus) and elephant grass (Pennisetum purpurum). In northern Australia under suitable conditions both give high yields of fibre per hectare. Kenaf can be separated by simple mechanical treatments into bark and woody fractions. Pulps prepared from the bark resemble softwood pulps in their general papermaking properties. The kenaf wood and the elephant grass pulps are short fibred and are more like hardwood plups. The draining properties of all these pulps are poorer than those of conventional wood pulps. The possibilities of using the stem and leaf material from grain sorghum, cassava stems and abaca fibre are also considered.