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Issue 05/2015

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Fibers & Textiles

Fibers & Textiles Improved PLA twines for horticulture support For the growth of a large number of crops in horticulture support is used in the form of wires. These so called twines support the fruit and vegetable plants and should be able to carry a fully grown plant. Normally polypropylene twines are used in horticulture. A considerable disadvantage of polypropylene twines is the waste management after the harvest. The remaining of the plant including the polypropylene twines is discarded as waste; however, due to the mixed character it is impossible to qualify this waste as compost. Therefore, it is treated as normal waste and is incinerated or collected and transported to a landfill. Separating the twines from the plant waste is often too time consuming and therefore expensive. The incentive to develop a compostable twine is 2-fold: • It is cheaper for the grower to dispose his waste, separation is not necessary. • Plant waste and twines can be collected and composted, i. e., less landfill/incineration. There are already biodegradable alternatives available in the form of natural fibers (jute, sisal, flax, hemp); however, these twines tend to degrade too fast and loose their strength during cultivation and are therefore not suitable for the growth of all crops. The development of a compostable twine which can replace polypropylene twines is challenging. The twine should have enough tenacity for a period up to 12 months. Moreover, the twine should survive a high relative humidity, temperatures above 50 °C and should not be susceptible to preliminary degradation. Twines that are used outside should withstand direct sunlight (UV) as well. PLA is the most suitable raw material from an economic and technical point of view: it is relatively cheap, compostable and UV stable. However, PLA suffers from creep behavior: at a tension below break level it will elongate until a premature break occurs. This creep behavior is more pronounced at elevated temperatures and at higher relative humidities. The most challenging task was to develop a PLA twine without the creep behavior. Applied Polymer Innovations API (Emmen, The Netherlands) succeeded in this task. The customized melt spin process, is therefore patent pending. In the graph below the results of a stress test are shown: the newly developed GreenTwine performs 3 times better than other PLA based twines. GreenTwine is currently in the pilot phase and field tests in the USA, Mexico, Canada, Israel, Finland and The Netherlands are in progress. The twine is tested on peppers, eggplants, cucumber and tomatoes. After evaluation of the field tests Applied Polymer Innovations will launch the product on the market. MT Figure 1: GreenTwine with improved properties as compared to conventional types. Figure 2: Field test; GreenTwine as a support for tomatoes 100 90 80 70 Standard PLA yarn GreenTwine Creep (%) 60 50 40 30 20 Commercially available PLA based twine 10 0 0 5 10 Time (h) 15 20 14 bioplastics MAGAZINE [05/15] Vol. 10

Fibers & Textiles World’s first piezoelectric fabrics for wearable devices Kansai University (Osaka, Japan) and Teijin Limited (headquartered in Osaka and Tokyo, Japan) announced earlier this year that Professor Yoshiro Tajitsu, Faculty of Engineering Science, Kansai University, and Teijin have developed the world’s first polylactic acid (PLA) fiber- and carbon-fiberbased piezoelectric fabrics. The new piezoelectric fabrics combine Teijin’s polymer and textile technologies – a Teijin growth strategy to integrate key existing materials and businesses – with Prof. Tajitsu’s worldleading knowledge of piezoelectric materials. Development was supervised by Prof. Tajitsu at Kansai University, with technological cooperation provided by the Industrial Technology Center of Fukui Prefecture. The fabrics comprise a piezoelectric poly-L-lactic acid (PLLA) and carbon fiber electrode. Plain, twill and satin weave versions were produced for different applications: plain weave detects bending, satin weave detects twisting, and twill weave detects shear and three-dimensional motion, as well as bending and twisting. contains lead, applications are being increasingly limited by the EU directive that restricts the use of certain hazardous substances in electrical and electronic equipment. Polyvinylidene fluoride (PVDF) is a well-known piezoelectric polymer. However, it is limited to use in sensors and such, and it is not suited to industrial-level manufacturing because it requires poling treatment and exhibits pyroelectricity. In 2012, Kansai University and Teijin developed a flexible, transparent piezoelectric film by alternately laminating PLLA and optical isomer poly-D-lactic acid (PDLA). The all-new wearable piezoelectric fabric announced in January is the newest application of this technology. MT CAD data can immediately reflect the folding of a piezoelectric fabric. New piezoelectric fabrics (from left: plain weave, twill weave and satin weave) The sensing function, which can detect arbitrary displacement or directional changes, incorporates Teijin’s weaving and knitting technologies. The function allows fabric to be applied to the actuator or sensor to detect complicated movements, even three-dimensional movements. Kansai University and Teijin introduced the new piezoelectric fabric at the 1 st Wearable Expo (Tokyo, January 2015). Kansai University and Teijin will continue working on ideal weaves and knits for fabric applications that enable elaborate human actions to be monitored simply via clothing worn by people. Such applications are expected to contribute to the evolution of the Internet of Things (IoT) in fields ranging from elderly care to surgery, artisanal techniques to space exploration, and many others. Piezoelectricity is the ability of certain dielectric materials to generate an electric charge in response to mechanical stress. It also has the opposite effect – the application of electric voltage produces mechanical strain in the materials. Both of these effects can be measured, making piezoelectric materials effective for both sensors and actuators. Lead zirconate titanate (PZT) has practical piezoelectric applications in industry, but as a ceramic material it lacks transparency and flexibility. In addition, because PZT bioplastics MAGAZINE [05/15] Vol. 10 15

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