Upper use temperature

The upper use temperature for annealed ware is below the temperature at which the glass begins to soften and flow (about Pa-s or 10 P). The maximum use temperature of tempered ware is even lower, because of the phenomenon of stress release through viscous flow. Glass used to its extreme limit is vulnerable to thermal shock, and tests should be made before adapting final designs to any use. Table 4 Hsts the normal and extreme temperature limits for annealed and tempered glass. These data ate approximate and assume that the product is not subject to stresses from thermal shock. 

Harden s (27) market survey of the growth of polyolefin foams production and sales shows that 114 x 10 kg of PE was used to make PE foam in 2001. The growth rate for the next 6 years was predicted as 5-6% per year, due to recovery in the US economy and to penetration of the automotive sector. In North America, 50% of the demand was for uncrosslinked foam, 24% for crosslinked PE foams, 15% for EPP, 6% for PP foams, 3% for EVA foams and 2% for polyethylene bead (EPE) foam. As protective packaging is the largest PE foam use sector, PE foam competes with a number of other packaging materials. Substitution of bead foam products (EPP, EPE, ARCEL copolymer) by extruded non-crosslinked PE foams, produced by the metallocene process was expected on the grounds of reduced costs. Compared with EPS foams the polyolefin foams have a lower yield stress for a given density. Compared with PU foams, the upper use temperature of polyolefin foams tends to be lower. Eor both these reasons, these foams are likely to coexist. 

Radical copolymerization of styrene with lCM-0% acrylonitrile yields styrene-acrylonitrile (SAN) polymers. Acrylonitrile, by increasing the intermolecular forces, imparts solvent resistance, improved tensile strength, and raises the upper use temperature of polystyrene although impact resistance is only slightly improved. SAN finds applications in houseware... 

Chlorinated poly (vinyl chloride) (CPVC) has increased Tg compared to PVC, and this increases its upper use temperature. Applications include hot- and cold-water pipe as well as pipe for the handling of industrial chemical liquids. Chlorinated polyethylene (CPE) finds use as roofing and other vapor barrier membranes, as pond liners, and as an additive to improve the impact strength of PVC. 

Matrix Material Process Temperature (°C) Upper Use Temperature (°C)... 

Table 7.4 Manufacturers Recommended Upper Use Temperatures for Selected Polymeric Materials...

In addition to not offering properties expected for phase pure SiC, the original Yajima process suffers from other drawbacks that include a multistep precursor synthesis and the inability to self-cure. Finally, the presence of oxygen limits the upper use temperature for both Nicalon and Tyranno fibers to ca 1200 °C because above this temperature CO and SiO gases evolve, generating defects (large crystallites, pores and voids) that contribute to substantial decreases in mechanical properties. 

Determination of the lower and upper useful temperatures of the polyurethane... 

The mechanical properties of PTFE at room temperature are similar to those of medium-density polyethylene, i.e., relatively soft with high elongation, and remaining useful over a wide range of temperatures, from cryogenic (just above absolute zero) to 260°C (500°F) its recommended upper use temperature.28 Stress-strain curves are strongly affected by the temperature however, even at 260°C (500°F) the tensile strength is about 6.5 MPa (942 psi).29... 

Perfluoroelastomers (ASTM designation FFKM) are essentially copolymers of two perfluorinated monomers, TFE and PMVE with a CSM, which is essential for cross-linking. Perfluoroelastomers can be cured by ionizing radiation without any additives. The advantage of radiation cured FFKM is the absence of any additives, so that the product is very pure. The disadvantage is the relatively low upper-use temperature of the cured material, typically 150°C, which limits the material to special sealing applications only [32]. 

---