Crystalline Polymers
Highly crystalline polymers are rigid, high melting, and less affected by solvent penetration. Crystallinity makes a polymers strong, but also lowers their impact resistance. As an example, samples of polyethylene prepared under high pressure (5000 atm) have high crystallinities (95 – 99%) but are extremely brittle.
Small molecules and ions form a three-dimensional lattice with an extended regular structure that makes large crystals possible.
We usually describe such lattices with a unit cell – the smallest repeating unit in the lattice . In the case of NaCl, the unit cell is said to be face-centered cubic.
Polymer molecules are very large so it might seem that they could not pack together regularly and form a crystal. It now is known that regular polymers may form lamellar (plate-like) crystals with a thickness of 10 to 20 nm in which the parallel chains are perpendicular to the face of the crystals.
Pros
- Good Strength
- Good High Temperature Performance
- Good Flexibility
- Good Chemical Resistance
Cons
- High Shrinkage. Warp
- Poor Impact
- Good Creep Resistance
- Smaller Processing Window
- Good Memory (For Living Hinges)
- Not Usually Solvent Bondable or Paintable
PAL is committed to promoting sustainability and Environmental Leadership. Concern for the environment and promoting a broader sustainability agenda are integrated in PAL’s decision making and we promote sustainability awareness in the community of Santa Ana by adopting several initiatives aimed to reduce PAL’s environmental impact and raise awareness.
We believe that environmental awareness is not about being fanatical. What we are really talking about is balance, logic and a reconnection with the world in which we live. There is so much unnecessary waste that we generate in this world, there are so many unhealthy ingredients that we digest. There are so many things that we do not need or want, that get in our way! We want to empower our staff by creating awareness and by demonstrating best practice to the extent possible.
Specifications
| Polymer Family | Advantages | Disadvantages | Some Typical Applications |
|---|---|---|---|
| PEEK | Extreme chemical resistance, Wear, Stength | High cost | Wear plates, Semiconductor |
| LCP | Very fast flowing | Hot Water | Electronic/Electric connectors |
| PPS | Inherently FR, High Temperature | Nitric acid | Electronics, Reflectors |
| PPA | Low water absorption, Good strength | Phenols, Some acids | Electronics, Industrial, Cooling systems |
| PET | Appearance, Stiffness, Creep resistance | Sterilization, Hot water | Engine components, Appliance housings |
| PBT | Appearance, Moldability, Chemical resistance | Sterilization, Hot water | Connectors, Relays, Housings |
| NYLON | Fatigue resistance, Scuff resistance | Sodium Hydroxide, Salts | Cable ties, Velcro, Auto |
| POM | Snap-fits, Wear, Critical tolerances | Fumes, Tool corrosion | Clips, Knobs, Gears |
| PMP | Transparency, Chemical resistance | UV exposure, Chlorine | Labware, Cookware |
| PP | Living hinges, Flexible, Chemical resistant | Nitric acid, Warp, Low temperature | Consumer, Disposables |
| HDPE | Semi-rigid, Low temperature impact, Chemical resistance | Nitric acid, Acetone | Lids, Handles, Containers |
| LLDPE | Flexible, Low temperature impact, Chemical resistance | Nitric acid, Acetone | Lids, Handles, Containers |
| LDPE | Very Flexible, Low temperature impact, Chemical resistance | Nitric acid, Acetone | Lids, Handles, Containers |
