Tensile Properties of Polypropylene

tensile Properties of PolypropyleneIntroductionIf an engineer wanted to flesh a bridge to span a river, it would be absurd to go through building it out of papier-mch or rubber. We know this because we know something about the demands that all(prenominal)ow for be put on the bridge and we know that these materials do non satisfy the requirements. After considering new(prenominal) materials, perhaps titanium or last tech aluminium alloys, we may discount them on the grounds of follow even if they do perplex suit adequate mechanical properties to make a good bridge. Eventually we may decide on marque precisely which hotshot? There are thousands to choose from. Which has the best properties at an inexpensive price? The cost effectiveness of any material is a military issue not to be dealt with here but we mustiness ask which steel has the near appropriate physical properties. In order to answer this question, we must conduct getks on diverse steels and compare the vector sums when samples of the steel are time- earth-closetvased to destruction.Polypropylene has the ability to crystallise which was a real exciting hazard as it is also an economical material so the popularity of it grew and production began all across most of Europe its use. Lots of distinguishable types of polypropene have been under production since the early 1950s mainly because of its insulating properties. it is used in many different fields, bumpers and some of the interior in a railway car is developed using polypropylene its also widely used in electrical components because of its great electrical resistance at extravagantlyschool temperatures. It has analogous properties to polyethylene.Because of its use in many different fields its necessary to turn up the material in a variety of ways. In this test the pliable properties leave behind be examined at different exam speeds. This test is do becauseThe test process involves placing the test specimen in the examination political machine and slowly extending it until it shimmys. During this process, the elongation of the gauge section is recorded against the utilize force. The entropy is manipulated so that it is not specific to the geometry of the test sample.Theory Polypropylene, like otherwise plastics, typically starts with the distillation of hydrocarbon fuels into lighter groups called fractions some of which are combined with other catalysts to produce plastics (typically via polymerisation or poly-condensation)For archetype, the polymerisation of propylene, which is identical to ethylene however that one hydrogen substituent has been replaced by a methyl (CH3) group, outcomes polypropylene. This material has a higher melting point (160-170 oC), higher tensile strength, and great inflexibleness than polyethylene. infix 1-Propylene monomers polymerisation to polypropyleneDepending on how they are united or joined (chemical bonds or intermolecular forces) and on the arr angement of the different chains that forms the polymer, the resulting polymeric materials pile be classified asThermoplasticsElastomersThermosetsDepending on the chemical composition, polymers can be inorganic such as glass, or they can be organic, such as adhesives of epoxy resin. Organic polymers can be also divided into natural polymers such as proteins and synthetic polymers as thermosets materials.Description of apparatusThe apparatus used the most for the testing part of the experiment was the zwick tensile testing machine this is a exceedingly accurate piece of equipment as it has high resolution angle metre which allows excellent repeat accuracy.This type of machine has two crossheads one is modify for the length of the specimen and the other is driven to apply tension to the test specimenhe machine must be able to stick enough force to break in the specimen. The machine must be able to apply the force quickly or slowly enough to mighty mimic the actual application. Finally, the machine must be able to accurately and precisely measure the gauge length and forces appliedFigure 2-Tensile testing machine (diagrammatic sketch form)Test procedure The test go forth be carried out using the Zwick tensile testing machine, with 3 different specimens each of them will be extended at different speeds ideal 1 protraction speed= ampere-second mm/min prototype 2 Extension speed= 50 mm/minexample 3 Extension speed= 12.5 mm/minBefore testing the specimens, they must be measured before and after the test to see what impact the test had on the specimensAfter the measurement, have been taken its mandatory to make a table to compare the interference to the extension this representical record will be required to estimate relevant values that will be needed to complete the calculations.For all the specimens you are required to obtain a verity of tensile properties including token(a) yield extendYoungs modulus shot melodic phrase (nominal and true)Tensile duct ilityResultsexample (mm) intermediate (mm)Av.CSA = tw (1T2.132.182.202.1710.20W4.684.734.704.702T2.132.152.162.1410.10W4.684.724.714.703T2.142.152.162.1510.11W4.704.724.694.70Specimen 1 calculated results when extended at speed of 100 mm/min venture Length (mm)33.00Initial cross- sectional sphere of influence ()10.21 break off length (mm)(55-33) 22.00 thickness at dampen (mm)0.91Width at chap (mm)2.50Cross-sectional discipline at Fracture ()2.28Load at yield (N)270.00Load at rupture (N)170.00 titulary yield stress ()26.45Extension at high yield (mm)1.54Young modulus ()566.79Nominal fracture stress ()16.65True fracture stress ()74.56Tensile Ductility (mm)0.66Specimen 2 calculated results when extended at speed of 50 mm/min Gauge Length (mm)33.00Initial cross-sectional commonwealth ()10.10Fracture length (mm)(123-33) 90.00Thickness at fracture (mm)0.93Width at fracture (mm)2.61Cross-sectional area at Fracture ()2.43Load at yield (N)262.50Load at fracture (N)172.50Nominal yield stress ()25.99Extension at high yield (mm)1.54Young modulus ()556.93Nominal fracture stress ()17.08True fracture stress ()70.98Tensile Ductility2.72Specimen 3 calculated results when extended at speed of 12.5 mm/min Gauge Length (mm)33.00Initial cross-sectional area ()10.11Fracture length (mm)(242-33) 209.00Thickness at fracture (mm)0.88Width at fracture (mm)2.01Cross-sectional area at Fracture ()1.77Load at yield (N)273.75Load at fracture (N)267.50Nominal yield stress ()27.08Extension at high yield (mm)110.26Young modulus ()8.08Nominal fracture stress ()26.46True fracture stress ()151.13Tensile Ductility6.33Calculations of average cross sectional area specimen 1 Average cross sectional area = Average thickness x Average widthAverage cross sectional area = 2.17 mm x 4.70 mm = 10.20 Calculations of specimen 1 Nominal yield = Nominal yield = = 26.45 Youngs modulus= Youngs modulus= = 566.79 Nominal fracture stress = Nominal fracture stress = = 16.65 True fracture stress = True frac ture stress = = 74.56 Tensile ductility = Tensile ductility = = 0.66 mmGraphs Figure 3-Graph of load vs extension for specimen 1- Figure 4-Graph of load vs extension for specimen2- Figure 5- Graph of load vs extension for specimen 3- railleryUnsurprisingly when you inspect between the three charts you can see a thin pattern occur which is that the faster you extend the Polypropylene the quicker it breaks. The graphical record readings are used to find how much it was extended when broken so that the tensile ductility can be worked out. There have been errors in the graphs because in the laboratory the measured extension of the break was 22mm whereas the zwick tensile testing machine do a graph that showed it to be a band little around 8mm which is surprising to have such a varied result. Retrieving most of the results from the graph required a lot of estimation because specimens one and two had scales of 20 and specimen 3 had a scale of 50 these both arent precise enough to get an accurate reading of the graph so a lot of estimation was required.As it can be seen in the results the extension at high yield point was very different for specimen 3 compared to the other specimens, this at first look could be considered as an anomaly even though this was expected because the less stress that is put on the specimen meant that the extension of the yield would be higher but such a big gap wasnt expected. However, look at the results of the other groups in the lab it shows that the result is acceptable. The other result that differed in specimen 3 when compared to the other specimens was the load at fracture this is because specimen 3 extended for a much longer length then the other two so there was much more(prenominal) load at fracture which meant that the fracture stress was much greater too as shown in the results.Also, glass transition temperature had to be controlled so that the polypropylene wasnt too brittle, as temperature is hard to get accurate most of the readings might have differed because of it.Conclusion It can be seen in this test how speed effects the tensile properties of polypropylene, as the results and graphs show that when tension is applied quicker as its done in the first specimen it can take a lot less stress to break the polypropylene compared to the 3rd specimen which took a lot more tension because it spread out much more than the other 2 specimens as seen in embark 6.The results of the test are reliable but improvements could have been made the graph could have a much smaller scale which would have made the readings off the graph much easier to obtain. Also, there were assumptions that were made while doing this for example when working out the youngs modulus we had to assume that the line between the origin and the high yield point is linear.Figure- 6Photos of the 3 specimens before and after the test.References instructionhttps//www.creativemechanisms.com/blog/all-about-polypropylene-pp-plastichttp/ /www.bpf.co.uk/plastipedia/polymers/pp.aspxhttps//en.wikipedia.org/wiki/Tensile_testingImageshttp//www.chemistry.wustl.edu/edudev/Designer/session4.html