The lumen inside a mature, dead fibre cells is very small when viewed in cross section.
Fibres are removed from the stems by retting, which has various ways. These include field retting and water retting. The fibre may also be removed practically, by just removing it using the hand. This is the cheapest and quickest method, with no produced harmful waste. Yet, it is the most inaccurate way of retting, since the first two methods happen over a period of time. In water retting, the plant stems are submerged in water and kept there for about 20 days in order to loosen up with fibres from other components in the stem. Field retting is when the cut crop left outside, letting bacteria approach it. The bacteria attack the pectin and lignin, which frees the cellulose fibres. Once retting is complete, stems are removed when washed then taken to mechanical process. This includes the beating of it to remove soft tissue, and then dried so that only the fibres remain.
Apparatus:
- Pampas grass and celery
- Bucket/ Bowl
- Rubber gloves
- Paper towels
- Eye protection
- Clamp stand with clamps
- Masses measuring grams
- Weight holder
- Corks
- Tiles
Method:
Peel the pampas grass to remove the fibre which is the central pith, leaving the outside cuticle and epidermal layer. The fibre is made up of the vascular tissue; they contain both the xylem vessels and the sclerenchyma fibres. This has to be done the same for the celery plant, also. The fibres which are white string-like have to be peeled off the celery. Clamp the fibres at each end using corks and a tile to hold the fibre in place. Apply a force in the centre using suspended masses, which will be the weights. The mass (or force) required to break the fibres gives a measure of tensile strength. The more masses which are added, the more strength the plant fibre has. This therefore shows to what extent it could be used for production. Testing the strength has to be repeated three times for each plant fibre, to increase reliability/validity of the data. This also reduced any systematic or random errors. When testing the fibres, the fibre has to be straight when held by the clamps. Therefore, tensile strength measurements will be more accurate, then a bent fibre holding the weights with all its mass.
Diagram of Procedure:
Fair Test/ Reliability:
In order for reliable results, the procedure for each fibre has to be repeated at least three times. This will produce more valid results, since the fibre has been tested out a few times. Although this method isn’t completely accurate, it is quick. The reason it is not completely accurate is because the weights aren’t precise enough for a real result. For instance, if a fibre holds 100g and you put another 20g on, the result cannot exactly be 100g. It may range from 100-120g. Therefore, the weighing result isn’t completely accurate. Another inaccuracy is the clamping. The more weights added to the fibre, the more likely the fibre will release from the clamp. In result, the experiment is more likely showing what weight the clamp can withstand, not how much weight the fibre can. For scientific purposes, this method is highly unreliable. Yet for a school purpose, it still proves the strength of various plant fibres.
Results:
In result, the pampas withstood more tensile strength than the celery fibre. For all three trials, the celery fibre held a weight of 100g. Therefore, this fibre isn’t that good and reliable for commercial uses. This is why it’s not used for products. Instead, its uses include a vegetable for eating, and nutritional medicine for weight – loss diets. On the other hand, the pampas has a very high tensile strength. Out of the three tests, only one had 700g while the other two were 800g. This may be because the first fibre was poorly peeled off; leading to quicker breakage. A fibre obtained from the leaves is used for making paper. The leaves are harvested in the autumn; they are cut into usable pieces and soaked for 24 hours in clear water. They are then cooked for 2 hours with lye and then beaten in a blender. The fibre makes a yellow paper. Therefore, higher tensile strength gives pampas grass more usage than celery.
Safety/ Risk Assessment:
When using the pampas grass, there are barbs which may ‘sting’ when touched. Although there will be no major injuries, there may be a risk of getting a minor cut. Handling the grass when removing the fibre should the in order not to cut the skin. Pampas grass may even be a possible allergen to some people, therefore know your allergen history before doing the experiment. When using the weights, be careful not to place them near the edge of the table. Since they will eventually fall once the fibre can no longer withstand the weight, they could fall on the foot. This will lead to pain if there were large amounts of weights. Other than the listed safety measures, there is no other including no ethical issues of this procedure.
Improvement:
In order to improve the results, more trials have to be carried out. When doing the tests, the fibre has to be exactly the same as the fibre used before. This includes appearance, weight, if it’s not rigid and broken, length. If different fibres were used of measuring the same plant, the results wouldn’t be as precise. The weights have also need to be changed, in smaller amounts. This is not only in 20g, 30g etc., but also in 2g, 5g, etc. When putting the weight on the fibre, the same amount of time has to pass between, with no pauses. Also, there could be another test to carry out on how much weight can the fibre withstand in a measured amount of time. This can be by putting a specific weight and measuring how long until the fibre breaks. Yet, this can take a long amount of time.