| |
Images of plastic samples with 10%
plasticizer under 40x magnification:
Results:
The data from the flexibility test should
perhaps be the one to place the greatest emphasis on, as flexibility is
the primary reason for the wide-use of DEHP as a PVC plasticizer,
despite its toxic and carcinogenic properties. For this graph, an
increase in deflection indicates an increase in flexibility of the
sample. For samples with safflower oil, DEHP, and sunflower oil, there
is a general trend upwards. These three show plasticizing effects
because the deflection of their samples increases as their
concentration increases.
However, there appears to
be a general trend downwards for propylene glycol and peanut oil.
Samples with peanut oil performed worse than samples without any
plasticizers to begin with. This indicates that peanut oil as a
plasticizer can be detrimental in flexibility performance of plastic
films. The same applies to propylene glycol in all samples except the
20% concentration. As expected, DEHP samples outperformed the rest
overall. However, safflower oil appears to be a viable alternative
because its graph is closest to that of DEHP. Samples of 20% safflower
oil even performed better than those of DEHP. Therefore, safflower oil
should be considered as a suitable replacement for DEHP.
For this
graph, an increase in absorbance indicates a decrease in clarity. A
transparent object would give a reading close to zero, whereas an
opaque object would generate a reading close to two. There appears to
be two trends. For the DEHP and peanut oil samples, clarity decreased
as plasticizer concentration increased. In general, for films
plasticized with sunflower oil, safflower oil, and propylene glycol,
clarity increased as plasticizer concentration increased. For safflower
oil and propylene glycol samples in particular, there seem to be
bell-curve behaviour. Their graphs peak at 20% concentration, which
show that this particular concentration imparts the least clarity to
the films. As expected, the conventional DEHP plasticizer seemed to
retain the most clarity. The organic peanut oil alternative produced a
nearly opaque film, hence its high readings in absorbance. The
performance of safflower oil as a plasticizer is closest to that of
DEHP. Additionally, samples with safflower oil and propylene glycol
were very close in clarity to DEHP ones in 40% concentration. The
difference was merely 0.12998 AU and 0.13771 AU. Therefore in terms of
effects on clarity, safflower oil appears to be the best alternative in
place of DEHP.
From the formula of
flexural stress, E (Elastic Modulus) is calculated for each sample. The
lower the number is for E, the more elastic the material is. The graph
indicates that films with DEHP are the most elastic overall, with
safflower oil films closely behind. In addition, peanut oil and
propylene glycol are not suitable replacements for DEHP because they
have the lowest elastic moduli and these are even higher than films
without plasticizers to begin with.
For
samples with DEHP, peanut oil and, sunflower oil, the general trend was
that an increase in plasticizer concentration resulted in an increase
in compression percentage. As expected, DEHP was most effective in
making films compressible. Its advantage becomes most apparent in
samples of 40% concentration. However, both propylene glycol and
safflower oil outperformed DEHP in terms of compressibility in samples
of 10% plasticizer concentration. Samples with propylene glycol come
very close to those with DEHP in the 20% concentration, and hence
should be considered as an appropriate alternative in products
requiring plasticizer concentrations close to this amount. Sunflower
oil performed the worst in compression tests, giving the lowest
percentages. Safflower oil is closest to DEHP in terms of plasticizing
effect in compression and can be considered the best alternative out of
the four.
Discussion
In our experiment, we chose to test four
aspects of plastic performance: clarity, compression, flexibility, and
elasticity. When examining our results, we’d like to place the most
emphasis on flexibility, as this is primarily what DEHP is used to
supplement. The clarity data is likely of the least importance, as
while some PVC products, such as medical tubing do need some degree of
transparency, this is not DEHP’s primary function. We decided to test
for compression, as PVC is being used with increasing frequency in the
area of construction.
While it was hardly surprising that DEHP should have the best overall
performance in the four tests we performed, we were pleasantly
surprised by how effective safflower oil was. We find these results
very encouraging, as safflower oil now poses as a potential organic
plasticizer for PVC plastics. It is cheap, accessible, safe for human
use, and environmentally friendly. If safflower oil were used as the
plastic’s primary plasticizers, this would increase the plastic’s
biodegradability, and also safety in the areas of production, use, and
disposal. The current, commercially used DEHP primary plasticizers is
toxic and when used in medical tubing and in baby teething rings, have
the potential to leach and put human health at risk.
The test area which safflower oil seemed to lack most in was clarity.
In relation to this, we must caution to note that our experiment dealt
only with primary plasticizers, when plastics are commercially
manufactured with dozens of plasticizers. If safflower oil were to be
used commercially, a secondary plasticizers could likely enhance
clarity.
The two samples that seemed to have poorest overall performance were
peanut oil and propylene glycol. One point of interest, however, was
that propylene glycol seemed to peak at the 20% concentration in each
of its tests. Peanut oil’s comparatively low performance can perhaps be
explained by the fact that of the three vegetable oils tested, it had
the lowest number of poly unsaturated fatty acids. Interestingly
enough, safflower oil, the best performer, had the most.
Statistical Analysis
For statistical analysis, please
click here. |
