Gökhan Malakçı-030070802- 13th Week

Polystyrene (PE) 07.05.2011 10:34 am

There are several polymers, copolymers, and terpolymers based on the monomer styrene (CgHg), of which polystyrene (PS) is used in the highest volume. It is a linear homopolymer with amorphous structure that is generally noted for its brittleness. PS is transparent, easily colored, and readily molded, but degrades at elevated tempera­tures and dissolves in various solvents. Because of its brittleness, some PS grades contain 5% to 15% rubber and the term high-impact polystyrene (HIPS) is used for these types. They have-higher toughness, but transparency and tensile strength are reduced. In addi­tion to injection molding applications (e.g., molded toys, housewares), polystyrene also finds uses in packaging in the form of PS foams.

(P.Groover, Fundamentals of Modern Manufacturing ,page 162)







Acrylics 07.05.2011 10:30 am

The acrylics are polymers derived from acrylic acid (C3H4O2) and compounds _: originating from it. The most important thermoplastic in the acrylics group is polymethyl-methacrylate (PMMA) or Plexiglas (Rohm & Haas's trade name for PMMA). It is an amorphous linear polymer. Its outstanding property is excellent transparency, which makes it competitive with glass in optical appli­cations, Examples include automotive tail-light lenses, optical instruments, and aircraft windows. Its limitation when compared with glass is a much lower scratch resistance. Other uses of PMMA include floor waxes and emulsion latex paints. Another important use of acrylics is in fibers for textiles; polyacrylonitrile (PAN) is an example that goes by the more familiar trade names Orion (DuPont) and Acrilan (Monsanto).

(P.Groover, Fundamentals of Modern Manufacturing ,page 158-159)











Bezier Surface 05.05.2011 15:13

This is a synthetic surface similar to the bezier curve ans is obtained by the transformation of a bezier curve.It permits twists and kinks in the surface.The surface does not pass through all the data points.A Bezier surface is defined by a twoo-dimensional set of control poins Pi,j where i is in the range of 0 and m, and j is in the range of 0 and n.Thus, in this case , we have m+1 rows and n+1 columns of control points and the control point on the ith row and jth column is denoted by Pi,j.Note that have (m+1)(n+1) control points.




( Alavala,Cad/Cam: Concepts And Applications,page 207)


Bicubic Surface 05.05.2011 15:25


The Bezier bicubic surface patch uses the basis matrix:

The vector coefficients are given by a 4 × 4 matrix of position vectors for sixteen points forming a characteristic polyhedron. Fig. 6.31 shows the characteristic polyhedron for a Bezier surface. The four corner points R (0,0), R (3,0), R (3,3) and R (0,3) lie at the corners of the surface patch itself whereas remaining points do not lie on the patch. The four points along each edge of the polyhedron define the four edge curves of the patch. The four interior points determine the cross derivatives at the corner and cross slopes along the nearest edges to them.



(P.Radhakrishnan,CAD/CAM/CIM,page 165-166)