29 сентября, 2015 
Pokraskin POM is widely known as ‘acetal’ and a well-known trade name is ‘Delrin’, manufactured by DuPont. This is a popular engineering plastic to replace parts that might otherwise be manufactured from metals. It is generally easy to machine and therefore makes for a good engineering plastic for small batch production or prototype applications.
Acetal is a highly crystalline polymer with good abrasion resistance, low water absorption and favourable frictional and wear properties. It exhibits high physical strength as well as excellent creep and impact resistance.
Applications include bearings, gears and conveyor belt links but also chemical pumps and, due to its resilience and recovery, it is also used for clips and snap-fit connections.
|
Table 2.12 Adhesive shear strengths |
(acetal) |
|
|
Adhesive type |
Description |
Shear strength (N/mm2) |
|
Cyanoacrylate |
Standard ethyl |
1.4 |
|
Toughened |
0.7 |
|
|
Ethyl + primer |
11.7 |
|
|
Two-part acrylic |
MMA |
1.4 |
|
Polyolefin bonder |
2.4 |
|
|
Epoxy |
‘5-minute’ epoxy |
1.7 |
|
Standard epoxy |
2.1 |
|
|
Silicone |
Alkoxy silicone |
0.3 |
|
UV acrylic |
Visible light cure |
1.7 |
|
Notes: All shear strengths are given as guidelines only and may vary considerably depending on grade of plastic, fillers, surface finish, etc. Recycling information = thermoplastic & |
Like PEEK, this material is also difficult to bond (Table 2.12) with engineering adhesives and usually requires some form of surface treatment to give a good bond.
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