Polymers and Plastics in Biomedical Applications Essay

polymers are increasingly being used to fabricate biomedical materials for tissue engineering and wound treatment applications, as well as for drug delivery. For tissue engineering and wound treatment applications, the mechanical properties of the polymeric material have to be matched to the specific application. An example of tissue engineering is the use of bioresorbable polymeric orthopedic materials for bone regeneration applications. The degradable material supports the growth and adhesion of new bone cells (chondrocytes) and is porous so as to provide a large, continuous surface for cell proliferation throughout the matrix. The degradable material serves to maintain mechanical integrity while the bone heals itself.Polymers and Plastics in Biomedical Applications Essay.  The materials are designed to degrade in a time suitable for the particular application, but may be on the order of six months to twenty-four months.

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An example of an external wound treatment application is artificial skin, where the polymeric material provides protection as new growth develops. Other materials are used internally to separate organs after surgical procedures. In tissue engineering and wound treatment applications the mechanical properties of the materials have to meet requirements specific to the application. In this experiment you will determine how the tensile properties of films of plasticized biopolymers depend on the chemical formulation of the material. Such applications are based on the polymer materials being degradable as well as biocompatible. Other applications might require materials that are biocompatible and nondegradable, such as long-term polyethylene implants.

POLYMERS

Polymers can be synthetic or biological. Synthetic polymers are almost always made from nonrenewable fossil feedstocks, mainly petroleum. Examples are polyethylene, polystyrene, poly(vinyl chloride), and polypropylene, all of which are polyolefins. Poly(ethylene terephthalate) [PET] is a synthetic polyester. None of the above-named polymers are degradable, the main reason being that the polymer backbones contain only carbon-carbon single bonds. Examples of biodegradable polymers derived from petroleum are poly(vinyl alcohol) [a polyalcohol], poly(ethylene glycol)[a polyether], and the polyesters polycaprolactone and poly(glycolic acid). Polymers and Plastics in Biomedical Applications Essay. Polymers with heteroatoms in their backbones are generally biodegradable, although there are exceptions.

Biological polymers (biopolymers) are found in nature; they are intrinsically biodegradable. Abundant biopolymers include plant polysaccharides such as starch (composed of amylose and amylopectin), cellulose, agarose, and carrageenan, and animal polysaccharides such as chitin and the glycosaminoglycans. Abundant proteins include gelatin(denatured/hydrolyzed collagen), casein, keratin, and fibroin.

Poly(lactic acid) (PLA) is an example of a synthetic commercial polymer in which the monomer, lactic acid, is produced in large amounts through fermentation; the polymer is then synthesized by conventional methods. PLA is biodegradable.

MECHANICAL PROPERTIES

In implant and wound healing applications, the mechanical properties of the materials are of critical importance. In this experiment you will carry out tensile tests—tests in which specimens are placed between two clamps (grips) and drawn. The instrument measures and displays the force being applied (the load) and the resulting increase in the length of the sample (elongation, also called extension).

From the dimensions of the film specimen (width and thickness), the instrument software calculates and displays the tensile stress (), equal to the load (F) per unit area of cross section (A = width x thickness).

It also calculates the (tensile) strain (), equal to the elongation (extension) divided by the original length of that portion of the specimen being measured (called the gage length). [In our experiment, the gage length is simply the separation of the grips securing the specimen.] The instrument will display percent elongation, which is the strain multiplied by 100. Polymers and Plastics in Biomedical Applications Essay.

As the tensile test proceeds, the instrument generates and displays a tensile stress-strain curve, which is a diagram that displays values of tensile stress (in MPa) plotted against tensile strain (%). The test continues until the specimen breaks. From the stress-strain curve, the software determines, and reports the following results in table form:

(1) Tensile strength at break (or ultimate strength), which is the tensile stress at break.
(2) Elongation at break, as a percentage.
(3) Young’s modulus (also known as elastic modulus or modulus of elasticity or sometimes simply as modulus).

It is calculated as the initial slope of the stress-strain curve, which is usually observed to be linear with plastic films. This initial region reflects the elastic deformation of the specimen, in which the stress varies linearly with strain, analogous to Hooke’s law for the expansion of a spring. Beyond the linear region, the behavior is termed viscous; polymers and plastics are said to be viscoelastic materials. Modulus is a measure of the “stiffness” of the polymer or plastic.

Table 1. Typical tensile properties of materials

Material t.s.(MPa) elong.(%) modulus(MPa)
polyethylene, low density 10 620 166
polycaprolactone 26 600-1000 435
polypropylene 36 – 1380
poly(lactic acid),
biaxially oriented film 110/145 160/100 3310/3860
keratin(human hair) 526 46 6700
copper, annealed 240 30 100,000-130,000
steel 380-700 – 200,000-250,000
glass 2160-4830 – 50,000-70,000
Encyclopedia of Chemistry, 4th ed.; Handbook of Physics, 2nd ed.

EXPERIMENTAL PROCEDURE

1. FILM CASTING

Prepare the following cast films of plasticized biopolymers.

Sample 1 Place 32 mL of 2%(v/v) aqueous glycerol solution in a 200 mL beaker. Add 88 mL water and 2.40 g starch and 4.8 g agar. Heat with stirring to approximately 85-95 °C or until the polymer is in solution; do not boil. Slowly pour the solution into the big petri dish on a flat level surface. Try to remove all imperfections (bubbles) from the surface.

Sample 2. Repeat using 32 mL glycerol solution, 88 mL water, and 1.20 g starch and 3.6 g agar.

Sample 3. Repeat using 48 mL glycerol solution, 72 mL water, and 1.20 g starch and 3.0 g agar. Polymers and Plastics in Biomedical Applications Essay.

Sample 4. Repeat using 48 mL glycerol solution, 72 mL water, and 2.40 g starch and 3.5 g agar.

Allow the solutions to set for approximately one hour then place the petri dish in the drying oven. Label all petri dishes.

2. FILM CONDITIONING

After the agar films have been in the drying oven for about 24 hours, remove the petri dishes from the oven and place them in the large relative-humidity conditioning box (maintained at approximately 50% relative humidity) for 24-48 hours.

3. PREPARING TEST SPECIMENS

After conditioning, the films are ready to have test specimens prepared from them. Working with one sample at a time, remove the petri dish from the conditioning box. Slowly and carefully remove the film from the petri dish by first peeling one corner and then applying fairly equal pressure to the entire width of the film as it comes off the petri dish lengthwise.

Place the sample on a piece of cardboard. Using the 1/4″ wide aluminum template as a straight edge, and the cutting knife, cut a rectangle approximately 3.5″ x 3″ from the center of the film, so as not to include any edges, as they are often not as uniform in thickness as the center. Polymers and Plastics in Biomedical Applications Essay.
Align the sample on the cardboard as follows:

Place the 1/4″ wide aluminum template vertically near one of the edges. Using the cutting tool, cut on both sides of the template to produce a specimen 3.5″ long and 1/4″ wide. Cut as cleanly as possible so as not to notch or tear the specimen. Cut six or seven additional strips, but do not use the second cut of the previous specimen as the first edge of the next; make two new cuts to produce each specimen.

Place the cut specimens on a piece of filter paper and transfer them into the dessicator located next to the Instron instrument. Similarly prepare specimens from the other three film samples.

4. MEASURING MECHANICAL PROPERTIES OF TEST SPECIMENS

During the laboratory you will measure the mechanical properties of the fours cast films. Measure at least five specimens for each of the four film samples. As you remove each specimen from the dessicator, you will be measuring the thickness of the specimen with a digital caliper.

5. OPERATING THE INSTRON TESTING INSTRUMENT

Refer instrument manual.

6. LABORATORY REPORT

1. Express the compositions of the four film samples in terms of the weight percent of each component to two significant figures (excluding water); i.e. % agar, % glycerol (the density of glycerol is 1.26) and, if present, % starch.

2. Prepare a summary table of results showing the mean values of tensile strength (Mpa) (to 3 sig. figs.) and its standard deviation, elongation (%) (to 2 sig. figs.) and its standard deviation, and elastic modulus (MPa) (to 3 sig.figs.) and its standard deviation. [ASTM specifies these numbers of significant figures; a smaller number of significant figures would otherwise be justified given the observed standard deviations.]

3. For the three agar-glycerol films what correlation do you observe between the effect of glycerol on one property and its effect on the others? Prepare a graph for each of the properties showing variation with composition. In Excel you can show a standard error for each point separately by using a separate data series for each point. Do not show a trend line and do not attempt to connect the data points.

Plastic has benefited our society in a number of ways. In fact, plastic has helped aeronautics technology take giant steps forward over the past 50 years, including advancements in satellites, shuttles, aircraft, and missiles. As a result, civilian air travel has improved, as well as military air power and space exploration. In addition, the building and construction, electronics, packaging, and transportation industries have all benefited greatly from plastic.

Plastics are a subset of materials known as Polymers. These are composed of large molecules formed by joining many smaller molecules together (monomers). Other kinds of polymers are fibres, elastomers, surface coating and biopolymers, such as cellulose, proteins and nucleic acids. Plastics owe their name to their ability to be shaped to form articles of practical value by various conversion and forming processes. These are some peculiar properties of plastics materials, which make them unique so that products can literally be tailor-made out of these materials. In fact, plastics have permeated every facet of human life viz. agriculture and water consumption, building construction, communication, small and bulk packaging, education, medicine, transportation, defence, consumer durables to name a few. One of the reasons for great popularity of plastics is due to tremendous range of properties exhibited by them because of their ease of processing.

Hence, the demand for plastics has been increasing in modern living. Since last six decades, the Plastic Industry has grown worldwide with present consumption of more than 130 MMTPA. The Polymer/Plastic growth worldwide has been steady around 6% per annum which is much higher than the GDP growth rate of 3.3%. The higher growth sectors or demand drivers for plastic consumption are consumer and bulk packaging, plastic culture, building construction, electrical and electronics, automotive, consumer goods, medical, telecommunication, furniture and household applications. The output value of commodity, engineering and high performance polymers was US$115 billion, accounting for about 7% of total chemical output value globally .In India, however, the consumption of major plastics is only 3% of global consumption i.e. 4 million tons annually. This is very low as compared to global levels.

Plastics have a very strong correlation with economic growth. The Central Statistical Organisation (CSO) and NCAER have analysed various industry sectors for the input-output matrix to study the effect of growth of various sectors on GDP growth. Out of 115 sectors analysed, the Plastic Resin and Synthetic Fibres sectors rank a high 37. The importance of this sector can be gauged from the fact that one unit increase in the output value for the plastics sector reflects an increase of 2.38 units in the economy. Polymers and Plastics in Biomedical Applications Essay. Over the years the demand elasticity of polymer growth in comparison with GDP growth has been about 2.4 which is in line with the NCAER study. The growth of Plastic consumption worldwide as well as in India is inevitable and desirable, because multiple advantages that these materials provide. Some examples are given below as illustrations.

Plastics help improve quality of life: The Internet, globalisation, increased speed of communication, faster means of transportation, the advance of surgical medicine all these would not be possible without plastics. Continuous technological innovation by the plastics industry means that even more efficient, lightweight and adaptable forms of plastics are being developed for an increasing range of uses. It is these advances that allow plastics to play an important role in the pursuit of sustainable development, by bringing innovative solutions to the full range of challenges facing society. Preserve land, water and forest resources: Plastics have been providing help to tackle the worlds water distribution crisis, with affordable, easily constructed piping providing solutions to clean water shortages for 5.5 million people in Asia, the Middle East and Africa. Also the use of plastics drastically reduced the use of traditional usage of wood and other forest products thus resulting in reduction of deforestation.

Enable efficient use of non-renewable energy resources: It is estimated that the use of plastics as a whole actually saves more oil than is needed for their manufacture. At end-of-life, plastics can be a valuable alternative energy source in their own right. Plastics recycling continue to increase in world while energy recovery is a responsible use of our oil resources, diverting waste from landfill and helping to preserve fossil fuels. Tapping the sun and wind is already bringing clean and efficient energy to people world-wide and is greatly facilitated by the use of plastics that constitute major parts of the cells and turbines. Possess a more favourable cost-benefit ratio: Continuous improvements in the material itself and recovery technologies mean that, in the future, packaging will become even lighter and more resource-efficient. The recently introduced Smart Card largely made of plastics is a sign of things to come. Polymers and Plastics in Biomedical Applications Essay.

Has a very versatile range of applications: Plastics have proved to have a wide range of applications in a large number of fields and their applications are increasing due to advantage of low cost, high durability and easy availability. Plastics are treated as versatile materials since the properties of these materials can be tailored to meet specific demands by varying molecular weight, molecular weight distribution and side chain branching. Further making copolymers and polymer blends and alloys provide on mechanism for providing a synergism in properties and tailor making materials for specific applications. Plastics, therefore, clearly form a material of choice in a large number of commercial applications. The demand of Plastics will be further driven by: Population growth and urbanisation, Opening of rural markets, Explosive Indian middle class, Effective Media Network, Increased Purchasing Power, Higher Disposable Incomes, Successful Marketing, Brand Awareness and Rising Aspirations.

The Importance of Plastics in Medical Field Technology

Perhaps the greatest technological advancements in human society have evolved through the medical professions. Over the years technology has prolonged the average life span of an adult human by offering preventative vaccines, diagnostic tools, and comprehensive treatments. But smaller advancements ” such as the materials and tools used by medical professionals on a daily basis ” are often overlooked. Plastic is a prime example of a technology that fails to receive the credit it is due for changing the way medicine is practiced and creating a better experience for all involved. Early medical instruments were made of metals prone to rusting and inaccuracy.Polymers and Plastics in Biomedical Applications Essay.  Large and far from precise, these tools were difficult to sterilize and likely contributed to a wealth of infections when used between patients.

Even today, some medical instruments are made of stainless steel. Though the metal is easier to sterilize than its antique iron counterpart, surgical steel is still not designed to be flexible and has limitations in size and weight. Plastics, however, can be moulded to any shape or size. They are easily sterilized and more flexible than metal, allowing for greater manoeuvrability and precision. The cost of producing a plastic tool is much less than a stainless steel model, allowing a hospital or doctors office to adjust their budget for other technologies such as digital imaging software. But the use of plastics in the medical field is not confined solely to medical tools.

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An increasing amount of hospital devices are now being manufactured from plastic, enabling maximum cleanliness and efficiency. Additionally, plastics are the leading component in most replacement limbs, providing advancements in prosthetics that could never be accomplished with aluminium or other materials. As medical professionals continue to utilize plastics in their day-to-day practice, the material is quickly evolving to meet the needs of an industry that survives due to the ingenuity of technological advancements.

Plastic is one of the most used materials in todays world because of its properties as lightweight and durable material. Its popularity, however, is also its curse. We are using more plastic products than ever before and filling our landfills with plastic waste that does not biodegrade for centuries. Plastic recycling, however, is one of the easiest ways for you to be environmentally friendly, and recycling and lengthening the lifespan of plastic products are important for the health of our planet. Hydrocarbons form all or part of many of the materials we use in our society. Plastic is so useful because the polymer chains can be manipulated to serve practically any purpose. Flexible, soft and hard. They are insulating to electricity. The list is endless, and yes, I am passionate about plastic. Polymers and Plastics in Biomedical Applications Essay.