Bahadır Coşkun 030070008 (10th Week)

Heat Stabilizers: (16.04.2011 17:19)

Function:
Used to prevent oxidation of plastics by heat, especially during processing but also in application: widely used in PVC compounds. Heat stabilizers act by stopping oxidation, or by attacking the decomposed products of oxidation.

Properties affected:
Stability during processing: resistance to thermal breakdown of component under mechanical stress or loading: retention of colour transparency.

Materials:
Metallic salts: lead: combinations of barium, cadmium, zinc: organotin compounds. Hindered phenolics, secondary aromatic amines (primary anti-oxidants). Phospites/phosphonites, thioethers, soya-based epoxies (secondary anti-oxidants). Synergistic combinations of these.


(Murphy J.,Additives for plastics handbook, 2001, p.93 table 8.1)

Automatic Workpart Positioning: (16.04.2011 18:04)

many machining centers have more than three axes . One of the additional axes is often designed as a rotary table to position the part at some specified angle relative to the spindle. The rotary table permits the cutter to perform machining on four sides of the part in a single setup.
(Groover M.P., Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 2010, p.531)

Polyurethane : (17.04.2011 03:18)

Polyurethanes (PUs) are prepared from polyols and isocyanates.24,25 The isocyanate groups react with the hydroxyl groups on the polyol to form a urethane bond. The polyol can be a low-molecular-weight polyether or polyester. The isocyanate can be aliphatic or aromatic and in the preparation of linear PU is typically difunctional. However, isocyanates with greater functionality are used in preparing rigid foam PUs. The family of PU resins is very complex because of the enormous variation in the compositional features of the polyols and isocyanates. This variety results in a large number of polymer structures and performance profiles. Indeed, PUs can be rigid solids or soft and elastomeric or a have a foam (cellular) structure.

(Kutz M., Mechanical engineers' handbook: Materials and mechanical design, p. 350)

The Unified Numbering System (UNS) for Metals and Alloys (17.04.2011 03:18)

In nOrth America, the accepted designations for copper and copper alloys are now part of the unified Numbering System (UNS) for Metals and Alloys (Ref 1), which is managed jointly by American Society for testing and Materials (ASTM) and the Society of Automotive Engineers (SAE) International Under the UNS system, coppers and copper alloys are desigrated by five-digit numbers preceded by the letter "C". The five-digit codes are based on and supersede, an older three-digit system developed by the U.S. copper and brass industry. The older system was administered by the Copper Development Association (CDA) and alloys are still sometimes identified by their "CDA numbers" The UNS designations are simply two-digit extensions of the CDA numbers to accommodate new compositions.
In the UNS system from C10000 through C79999 demote wrought alloys, while cast alloy designations range from C80000 through C99999. As shown in Table1, within these two categories, the compositions are grouped into distinct families of coppers and copper alloys, including the six major branches-coppers, high alloy coppers, brases, bronzes, copper nickels, and nickel silvers.

(Davis R.J.,Copper and copper alloys, 2001, p.14)