Polypropylene may be subject to environmental stress cracking. The
occurrence is difficult to predict. It is dependent upon the process chemistry,
operating conditions, and quality of fabrication. In Table6.22 that gives the
compatibility of PP with selected corrodents, certain chemical/liner ratings
are identified by an “e” indicating that the liner in contactwith that specific
chemicalm ay be susceptible to ESC. Reference[ 1] provides am ore
comprehensive listing.
6.6.5P olyethylene
The maximum allowable temperature, at continuous contactt hat polyethylene (PE)can be used is 1208 F(498 C). PE is the least expensive of all the
plastic materials.
PE has awide range of corrosionresistance ranging from potable water to
corrosivew astes. It exhibits excellentr esistance to strong oxidizing
chemicals, alkalies, acids, and salt solutions.
Physical and mechanical properties differ by density and molecular
weight. The threemain classifications of density are low,medium,and high.
These specificg ravity ranges are 0.91–0.925, 0.925–0.940,a nd 0.940–0.965.
These grades are sometimes referred to as types 1, 11,a nd 111.
Industryp ractice breaks the molecular weight of polyethylenes into four
distinct classifications:
Medium molecular weight: less than 100,000
High molecular weight: 110,000–250,000
Extra high molecular weight: 250,000–1,500,000
Ultra high molecular weight: 1,500,000 and higher
Usually,t he ultra high molecular weight material has am olecular
weight of at least 3.1 million.
The two varieties of polyethylene used, for corrosive applicationsa re
EHMW and UHMW.
The key properties of these two varietiesa re:
Good abrasion resistance
Excellent impact resistance
Light weight
Easily heat fused
High tensile strength
Low moisture absorption
Nontoxic
Nonstaining
Corrosion resistant
Corrosion of Linings and Coatings
362
CAT8247—CHAPTER 6—6/10/2006—12:30—SRIDHAR—XML MODEL B–pp. 287–402
occurrence is difficult to predict. It is dependent upon the process chemistry,
operating conditions, and quality of fabrication. In Table6.22 that gives the
compatibility of PP with selected corrodents, certain chemical/liner ratings
are identified by an “e” indicating that the liner in contactwith that specific
chemicalm ay be susceptible to ESC. Reference[ 1] provides am ore
comprehensive listing.
6.6.5P olyethylene
The maximum allowable temperature, at continuous contactt hat polyethylene (PE)can be used is 1208 F(498 C). PE is the least expensive of all the
plastic materials.
PE has awide range of corrosionresistance ranging from potable water to
corrosivew astes. It exhibits excellentr esistance to strong oxidizing
chemicals, alkalies, acids, and salt solutions.
Physical and mechanical properties differ by density and molecular
weight. The threemain classifications of density are low,medium,and high.
These specificg ravity ranges are 0.91–0.925, 0.925–0.940,a nd 0.940–0.965.
These grades are sometimes referred to as types 1, 11,a nd 111.
Industryp ractice breaks the molecular weight of polyethylenes into four
distinct classifications:
Medium molecular weight: less than 100,000
High molecular weight: 110,000–250,000
Extra high molecular weight: 250,000–1,500,000
Ultra high molecular weight: 1,500,000 and higher
Usually,t he ultra high molecular weight material has am olecular
weight of at least 3.1 million.
The two varieties of polyethylene used, for corrosive applicationsa re
EHMW and UHMW.
The key properties of these two varietiesa re:
Good abrasion resistance
Excellent impact resistance
Light weight
Easily heat fused
High tensile strength
Low moisture absorption
Nontoxic
Nonstaining
Corrosion resistant
Corrosion of Linings and Coatings
362
CAT8247—CHAPTER 6—6/10/2006—12:30—SRIDHAR—XML MODEL B–pp. 287–402