Specific Plastics

Diphenylamine test Suspend 0.1 g diphenylamine in 30 ml water and then add carefully 100 ml concentrated sulfuric acid. (Note The acid should be added slowly.) Add a drop of the fresh reagent to the plastic sample on a plate a dark blue coloration indicates cellulose nitrate. 

If the result is negative, test for bound formaldehyde. Heat a small sample of the plastic with 2 ml concentrated sulfuric acid and a few crystals of chromotropic acid for 10 min at 60-70°C. A deep violet coloration indicates formaldehyde. Cellulose nitrate, polyvinyl acetate, polyvinylbutyral, and cellulose acetate give a red coloration these materials, however, are not included in this part of the analytical procedure. 

If the formaldehyde test is positive, heat a sample of the plastic with a 10% glycolic solution of potassium hydroxide (dissolve 10 g KOH in approximately 95 ml ethylene glycol). A smell of ammonia (confirmed by blue color of moist red litmus paper) indicates urea resins. Melamine resins do not 

Thiourea resins are identified by the simultaneous presence of nitrogen and sulfur. (For identification of the individual elements, see Section 6.2.13.) 

If the formaldehyde test is negative, cover a sample with nonaqueous sodium carbonate in a test tube and heat the tube until the material melts. 

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Nippon Shokubai and U.K. Seung are producing a fluorescent polymer claimed to be made from a co-condensation of ben2oguanamine and formaldehyde. Fine highly thermoset particles are manufactured in solution and later dried. It is useful in a wide range of appHcations, specifically plastics, and markets where bleed is a problem. 

AppHcation of an adhesion-promoting paint before metal spraying improves the coating. Color-coded paints, which indicate compatibiHty with specific plastics, can be appHed at 20 times the rate of grit blasting, typically at 0.025-mm dry film thickness. The main test and control method is cross-hatch adhesion. Among the most common plastics coated with such paints are polycarbonate, poly(phenylene ether), polystyrene, ABS, poly(vinyl chloride), polyethylene, polyester, and polyetherimide. 

Permeability. The low density of plastics is an advantage in many situations but the relatively loose packing of the molecules means that gases and liquids can permeate through the plastic. This can be important in many applications such as packaging or fuel tanks. It is not possible to generalise about the performance of plastics relative to each other or in respect to the performance of a specific plastic in contact with different liquids and gases. 

What this discussion identifies is that each material (specific plastic, specific steel, specific wood, etc.) behaves certain ways. If a product can be made from a specific steel rather than a specific plastic, that is the material to use. However, unfortunately for steel and other materials, plastics continue to expand its use where these other materials are not competitive propertywise and/or cost-wise. 

Basics Creep data can be very useful to the designer. In the interest of sound design-procedure, the necessary long-term creep information should be obtained on the perspective specific plastic, under the conditions of product usage (Chapter 5, MECHANICAL PROPERTY, Long-Term Stress Relaxation/Creep). In addition to the creep data, a stress-strain diagram under similar conditions should be obtained. The combined information will provide the basis for calculating the predictability of the plastic performance. 

Fig. 2-53 Example of the influence of tensile stress-strain curves subjected to an environment that influences the ductility of a specific plastic.

Identification To the nonplastic user and even certain plastic users, identification of over 35,000 plastics tends to be either misleading or confusing even though this situation should never exist. As explained in this book, certain specific plastics meet certain product requirements. 

Sheet forming processes, such as vacuum forming, do have effects on the product. The designer should be aware that these will affect the performance of one s product and one should learn how to modify the design to minimize any deleterious effects. Probably the most serious problem encountered in formed film or sheet products results from the fact that the materials are made from film or sheet at temperatures well below the melt softening point of the plastic, usually near the heat distortion temperature for the material. Forming under these condition when the draw down ratio is exceeded for a specific plastic can result in over stretched orientation of the material, the production of frozen-in stresses, poor product reproducibil-... 

Section 5 discusses options for chemical recycling of specific plastics waste ... 

Apart from MPW and PVC, several feedstock recycling processes have been developed for some specific plastics. In this respect, the most important plastics are ... 

DSM and Allied Signal have developed carpet identification equipment that can identify specific plastics. Particularly carpet made of nylon 6 (or nylon 66) fibres are separated, cut into pieces, isolated, and converted by polycondensation into their monomeric components. The monomers can then be reused in the production of nylon. DSM and Allied Signal opened the world s first large scale carpet recycling plant in Augusta, Georgia, US in November 1999. This plant has a capacity of 90,000 tpa nylon 6 carpet waste (109). 

The last example of chemical recycling of a specific plastic is the recycling of nylon from carpets. The RECAM (recycling of carpet materials) project is one... 

It is a well-known fact that specific plastic materials like flexible PVC, Polyurethane or Silicone may be easily attacked by microorganisms leading to discoloration or mechanical failures.14 This susceptibility to microbial attack is mainly attributed to the plasticiser content of the material as well as other ingredients such as stabiliser or antioxidants.5,6 The predominant organisms on the surface of those plastics are fungi and actinomycetes and it is said that by the action of their extracellular enzymes other organisms such as bacteria may be able to grow on the material.7... 

Inserts are often dedicated to specific plastic materials neat thermoplastics, neat and filled thermosets, reinforced plastics, composites, structural foams. .. 

Aseptically prepared collection plates are placed in the sampling apparatus. Petri dishes used must be sterilized prior to filling. Verify the adequacy of petri dish dimensions so that the operational characteristics are maintained according to the manufacturers specifications. Plastic petri dishes are not recommended because static changes are likely to be present in plastic that will reduce the collection efficiency. 

Plastic clay is used in, for example, the manufacture of bricks and roof tiles. Each product requires a specific clay with a specific plasticity. In the chapter on clay and in the section on moulding (chapter 9, Ceramic in General) the subject was already discussed. 

Soler-Llavina GJ, Sabatini BL (2006) Synapse-specific plasticity and compartmentalized signaling in cerebellar stellate cells. Nat Neurosci 9(6) 798-806 Stanton PK, Bramham C, Scharfman H (eds) (2005) Synaptic plasticity and transsynaptic signaling. Spinger, New York pp. 457-68... 

The following are various plastic families and their respective specific plastics that are included in the Chemical Resistance Chart. The boldfaced uppercase letters correspond to the plastics in the chart. These acronyms are generally accepted, but are not universal. 

Lubricity and Abrasion Resistance. Specific plastic materials offer outstanding self-lubricating performance and abrasion resistance. 

When designing and/or fabricating a product a specific plastic is used. A type from a plastic producer and/or requirements for a plastic identifies it. The same named, such as low density polyethylene, from two different companies usually has slightly different properties and processing characteristics. Data throughout this book which identifies a... 

As a construction material, plastics provide practically unlimited benefits to the fabrication of products, but unfortunately, as with other materials, no one specific plastic exhibits all these positive characteristics. The successful application of their strengths and an understanding of their weaknesses (limitations) will allow to produce useful products. With any material (plastic, steel, etc.) products fail not because of its disadvantage(s). They failed because someone did not perform their selection in the proper manner and/or incorrectly processed the plastic. 

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