Hard plastic

Resins vary from soft, elastic, film-forming materials to hard plastics. 

These cellulose esters form tough, strong, stiff, hard plastics with almost unlimited color possibilities. Articles made from these plastics have a high gloss and are suitable for use in contact with food. 

Barcol Indenter. The Barcol hardness tester is a hand-held, spring-loaded instmment with a steel indenter developed for use on hard plastics and soft metals (ASTM D2583) (2). In use the indenter is forced into the sample surface and a hardness number is read direcdy off the integral dial indicator caUbrated on a 0 to 100 scale. Barcol hardness numbers do not relate to nor can they be converted to other hardness scales. The Barcol instmment is caUbrated at each use by indenting an aluminum ahoy standard disk suppHed with it. The Barcol test is relatively insensitive to surface condition but may be affected by test sample size and thickness. 

The modulus term in this equation can be obtained in the same way as in the previous example. However, the difference in this case is the term V. For elastic materials this is called Poissons Ratio and is the ratio of the transverse strain to the axial strain (See Appendix C). For any particular metal this is a constant, generally in the range 0.28 to 0.35. For plastics V is not a constant. It is dependent on time, temperature, stress, etc and so it is often given the alternative names of Creep Contraction Ratio or Lateral Strain Ratio. There is very little published information on the creep contraction ratio for plastics but generally it varies from about 0.33 for hard plastics (such as acrylic) to almost 0.5 for elastomers. Some typical values are given in Table 2.1 but do remember that these may change in specific loading situations. 

Tests for indention under load are performed basically like the ASTM measure the hardness of other materials, such as metals and ceramics. There are at least four popular hardness scales in use. Shore A and Shore D is for soft to relatively hard plastics and elastomers. Barcol is used from the mid-range of Shore D to above it as well as RPs. Rockwell M is used for very hard plastics (Chapter 5, MECHANICAL PROPERTY, Hardness),... 

Styrene-butadiene-styrene (SBS) block copolymers are adequate raw materials to produce thermoplastic mbbers (TRs). SBS contains butadiene—soft and elastic—and styrene— hard and tough—domains. Because the styrene domains act as cross-links, vulcanization is not necessary to provide dimensional stability. TRs generally contain polystyrene (to impart hardness), plasticizers, fillers, and antioxidants processing oils can also be added. Due to their nature, TR soles show low surface energy, and to reach proper adhesion a surface modification is always needed. 

Every year, Americans use over one billion sharp objects to administer healthcare in their homes. These sharp objects include lancets, needles, and syringes. If not disposed of in puncture-resistant containers, they can injure sanitation workers. Sharp objects should be disposed of in hard plastic or metal containers with secure lids. The containers should be clearly marked and be puncture resistant. 

Continue with Subheading 3., step 18 in the method. The positive reaction product with this chromogen will be red, with the nuclei a light blue. Rather than dehydrating the specimens in ethanol and xylene, allow them to dry, add 1 drop of Crystal/Mount (Biomeda Corp, Foster City, CA) to the specimen and bake them in a 60°C oven for 30 min. This preparation is permanent and can be cover-slipped with Permount if needed. The Crystal/Mount will form a hard plastic coating on the slide, but it can be damaged by smudging. 

The resins used are polymers and copolymers of the esters of acrylic and methacrylic acids. They range in physical properties from soft elastomers to hard plastics, and are used in cementitious compounds in much the same manner as SBR latex. Acrylics are reported to have better UV stability than SBR latex and therefore remain flexible under exterior exposure conditions longer than SBR latex [88]. 

The development of plastics accompanied synthetic fibers. The first synthetic plastic with the trade name Celluloid was made in 1870 from a form of nitrocellulose called pyroxylin, the same substance used to produce the first rayon. Celluloid was developed in part to meet the demand for expensive billiard balls, which at the end of the nineteenth century were produced from ivory obtained from elephant tusks. John Wesley Hyatt (1837-1920) combined pyroxylin with ether and alcohol to produce a hard substance called collodion. Hyatt s collodion, like Bernigaut s original rayon, was unstable and potentially explosive. He solved this problem by adding camphor to the collodion to produce a stable hard plastic he called Celluloid. 

The products with low crosslink density are elastomers, but infusible, hard plastics are obtained when these polymers are crosslinkcd with large amounts of sulfur (40%). 

This polymer is a hard plastic that occurs naturally as gutta-percha or balata. Since the trans isomer packs better than the cis isomer, it has a higher specific gravity, a higher degree of crystallinity, and a higher melting point (67 C) than the ds isomer of polyisoprene. The chemical and the solvent resistance of the trans polymer are simitar to those of the ds polymer. 

The step 3 product (9 mmol), 2-hydroxyethyl methacrylate (4.8 mmol), and tetrapro-poxy zirconium (35 mg) were blended together and the solution cast into molds then UV-cured to give clear, hard plastic parts. 

Formaldehyde has hundreds of uses. Its largest use is in the production of synthetic resins. Many formaldehyde resins are hard plastics used in molding and laminates. Formaldehyde resins are used to treat textiles to make them wrinkle-free. It is also used to produce adhesives, which are used extensively in the production of plywood and particleboard. Other common uses are as disinfectants, fungicides, and preservatives. Formalin has been the traditional embalming fluid used in the mortuary industry for the last century. Formaldehyde is also used in papermaking, textile production, and fertilizers. 

Improvement of the mechanical properties of elastomers is usually reached by their reinforcement with fillers. Traditionally, carbon black, silica, metal oxides, some salts and rigid polymers are used. The elastic modulus, tensile strength, and swelling resistence are well increased by such reinforcement. A new approach is based on block copolymerization yielding thermoelastoplastics, i.e. block copolymers with soft (rubbery) and hard (plastic) blocks. The mutual feature of filled rubbers and the thermoelastoplastics is their heterogeneous structure u0). 

Immulon 2 hard plastic 96-well microtiter plates (Dynatech Ltd.)... 

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