Wheat straw fibres

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

Avella, M., Rota, G., Martuscelli, E., Raimo, M., Sadocco, P. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and wheat straw fibre composites thermal, mechanical properties and biodegradation behaviour. J. Mater. Sci. 35, 829-836 (2000)... 

Sain M, Panthapulakkal S (2006) Bioprocess preparation of wheat straw fibres and their characterization. Ind Crops Prod 23 1-8... 

AgroResin is a biodegradable packaging material from by-products of the palm oil industry. It can also be made from agricultural fibres, such as wheat straw. It is compatible with existing moulded pulp manufacturing processes. AgroResin has received Din-Certco certification for products made of compostable materials (DIN EN 13432 2000-12). 

Straw fibres Examples include rice, wheat and com straws. 

Alemdar and Sain [86] extracted Cellulose nanofibres of wheat straw and soy hulls, by a chemi-mechanical technique. They analysed the morphology and physical properties of the nanofibres by scanning and transmission electron microscopy. The wheat straw nanofibres have diameters in the range of 10-80 nm and lengths of a few thousand nanometres, and the soy hull nanofibres have diameters in the range of 20-120 nm and shorter lengths than the wheat straw nanofibres. Fig. 1.21a and b shows the TEM pictures of the wheat straw and soy hull nanofibres. The image shows the separation of the nanofibres from the micro-sized fibres. The thermal properties of the nanofibres were studied by the TGA technique and found that the... 

Hornsby PR, Hinrichsen E, Tarverdi K (1997) Preparation and properties of polypropylene composites reinforced with wheat and flax straw fibres. J Mater Sci 32 1009-1015... 

The twin-screw extruder has proved to be a versatile tool for continuous treatment of vegetable matter, either for food or non-food applications. Trials for the direct alkaline extraction of xylans from wheat bran in a twin-screw extruder were unsuccessful. Bran impregnation with sodium hydroxide in the twin-screw extruder was very efficient, but it was necessaiy to make the separation between the hemicellulosic gel and the lignocellulosic matrix in another apparatus and remained difficult without a dilution to a L/S ratio of 50. Bran and straw co-extrusion was therefore investigated to be able to reduce the L/S ratio. Straw fibres form a dynamic plug in the restrictive elements of the screw profile just after the filtration zone. The pressure induced in the extruder sheath by the cellulosic fibres enabled the liquid/solid separation. 

There is evidence to suggest that the intense action created inside the chamber of a high-speed mixer is sufficient to cause compaction and agglomeration of finely divided fillers [93], or damage to shear sensitive additives,such as glass fibres or naturally occurring fillers derived from wheat straw [128]. 

As a result of past research on PHAs and the commercial development of PHB and PHBV, it is perhaps not surprising that these polymers have also been examined for use in biodegradable composites. Examples of reinforcing fibres used with PHAs have included wood (Reinsch and Kelley, 1997 Peterson et al, 2002), wheat straw (Avella et al, 2000a, 2000b), pineapple leaf fibres (Luo and Netravali, 1999) and jute (Khan et al, 1999) amongst others. 

Wheat bran and sodium hydroxide were blended at room temperature in a separate reactor one hour before each experiment. Tlie initial L/S ratio was seven and the mixture was stirred for five minutes. The L/S ratio was increased to ten just before the introduction of the mixture into the twin screw extruder with a Nemo excentric-screw pump. Straw was introduced in the extruder s first section with a screw feeder. Straw was mixed with the alkaline dough in the first zone of the barrel through the neutral pitch element and the reverse-pitch screw element successively. The washing water was injected downstream from this zone, and the mixture was conveyed through the second reverse pitch located just downstream from the filtration module. The filtrate was collected and kept in a cold room before further processing, while the refined cellulosic fibres were gathered at the barrel outlet. 

Starch and sugar crops like wheat and sugar beet, as well as bioethanol, can be used to produce carbohydrates for use in the manufacture of plastics, adhesives and surface coatings. Oilseed crops such as oilseed rape and sunflowers can, as well as biodiesel, produce lubricants, surfactants and slip agents. The main fibre crops such as flax, hemp and cereal straw can be used for making paper, textiles, insulation material and bio-composites for the car industry. 

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