PVA Polyvinyl acetate
|Molar mass||86.09 g/mol/unit|
|Density||1.19 g/cm3 (25 °C)|
|Boiling point||112 °C (234 °F; 385 K)|
As an emulsion in water, PVAc emulsions are used as adhesives for porous materials, particularly for wood, paper, and cloth, and as a consolidant for porous building stone, in particular sandstone. Uses:
The stiff homopolymer PVAc, but mostly the more soft copolymer, a combination of vinyl acetate and ethylene, vinyl acetate ethylene (VAE), is used also in paper coatings, paint and other industrial coatings, as binder in nonwovens inglass fibers. sanitary napkins, filter paper and in textile finishing.
Polyvinyl acetate is also the raw material to make other polymers like:
Biaxially-oriented polyethylene terephthalate
Also known as: Mylar, Melinex, Hostaphan
The manufacturing process begins with a film of moltenpolyethylene terephthalate (PET) being extruded onto a chill roll, which quenches it into the amorphous state. It is then biaxially oriented by drawing. The most common way of doing this is the sequential process, in which the film is first drawn in the machine direction using heated rollers and subsequently drawn in the transverse direction, i.e. orthogonally to the direction of travel, in a heated oven. It is also possible to draw the film in both directions simultaneously, although the equipment required for this is somewhat more elaborate. Draw ratios are typically around 3 to 4 in each direction.
Once the drawing is completed, the film is "heat set" or crystallized under tension in the oven at temperatures typically above 200 °C (392 °F). The heat setting step prevents the film from shrinking back to its original unstretched shape and locks in the molecular orientation in the film plane. The orientation of the polymer chains is responsible for the high strength and stiffness of biaxially oriented PET film, which has a typical Young's modulus of about 4 GPa. Another important consequence of the molecular orientation is that it induces the formation of many crystal nuclei. The crystallites that grow rapidly reach the boundary of the neighboring crystallite and remain smaller than the wavelength of visible light. As a result, biaxially oriented PET film has excellent clarity, despite its semicrystalline structure.
If it were produced without any additives, the surface of the film would be so smooth that layers would adhere strongly to one another when the film is wound up, similar to the sticking of clean glass plates when stacked. To make handling possible, microscopic inert inorganic particles are usually embedded in the PET to roughen the surface of the film.
Biaxially oriented PET film can be metallized by vapor deposition of a thin film of evaporated aluminium, gold, or other metal onto it. The result is much less permeable to gases (important in food packaging) and reflects up to 99% of light, including much of the infrared spectrum. For some applications like food packaging, the aluminized boPET film can be laminated with a layer of polyethylene, which provides sealability and improves puncture resistance. The polyethylene side of such a laminate appears dull and the PET side shiny.
Other coatings, such as conductive indium tin oxide (ITO), can be applied to boPET film by sputter deposition.
Flexible packaging and food contact applications, covering over paper, insulating material, solar marine and aviation applications, science, electronic and acoustic applications, graphic arts, balloons
|Molar mass||2.500 – 2.500.000 g·mol−1|
|Appearance||white to light yellow, hygroscopic,
|Melting point||150 to 180 °C (302-356 °F; 423-453 K)
PVP is used in many technical applications:
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids, such as Nomex and Technora.
When Kevlar is spun, the resulting fiber has a tensile strength of about 3,620 MPa, and a relative density of 1.44. The polymer owes its high strength to the many inter-chain bonds. These inter-molecular hydrogen bonds form between the carbonyl groups and NH centers. Additional strength is derived from aromatic stacking interactions between adjacent strands. These interactions have a greater influence on Kevlar than the van der Waals interactions and chain length that typically influence the properties of other synthetic polymers and fibers such as Dyneema. The presence of salts and certain other impurities, especially calcium, could interfere with the strand interactions and care is taken to avoid inclusion in its production. Kevlar's structure consists of relatively rigid molecules which tend to form mostly planar sheet-like structures rather like silk protein.
Kevlar maintains its strength and resilience down to cryogenic temperatures (−196 °C); in fact, it is slightly stronger at low temperatures. At higher temperatures the tensile strength is immediately reduced by about 10–20%, and after some hours the strength progressively reduces further. For example, at 160 °C (320 °F) about 10% reduction in strength occurs after 500 hours. At 260 °C (500 °F) 50% strength reduction occurs after 70 hours.
Protection - cryogenics, armor, personal protection
Sports - personal protection, equipment, shoes
Music - audio equipment, bowed-string instruments, drumheads, woodwind reeds
Other - fire dancing, frying pans, rope, cable, sheath, electricity generation, building construction, brakes, expansion joints and hoses, particle physics, smartphones, marine current turbine and wind turbine
Properties (Rigid PVC vs. Flexible PVC)
|Thermal conductivity [W/(m·K)]||0.14–0.28||0.14–0.17|
|Yield strength [psi]||4500–8700||1450–3600|
|Young's modulus [psi]||490,000|
|Flexural strength (yield) [psi]||10,500|
|Compression strength [psi]||9500|
|Coefficient of thermal expansion (linear) [mm/(mm °C)]||5×10−5|
|Vicat B [°C]||65–100||Not recommended|
|Resistivity [Ω m]||1016||1012–1015|
|Surface resistivity [Ω]||1013–1014||1011–1012|
-unplasticized poly(vinyl chloride) (uPVC) for construction, signs, clothing and furniture, healthcare, plasticizers
|Melting point||115–135 °C (239–275 °F; 388– 408 K) (239–275 °F)|
Used as insulating material for medium and high voltage cable insulation,
for hot water pipes and molded parts in electrical engineering, plant engineering and in automotive industry
Also known as Teflon
|Melting point||600 K
|Thermal conductivity||0.25 W/(m·K)|
PTFE (Teflon) is best known for its use in coating non-stick frying pans and other cookware, as it is hydrophobic and possesses fairly high heat resistance.
PTFE is a versatile material that is found in many niche applications:
info to come