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Nitrogen Welding - Polypropylene Repair:
Standard Operating Procedure
Many automotive and truck bumpers, side panels and fuel tanks are made of polypropylene (PP) blends and are best repaired using the nitrogen welding process.
This SOP will guide you through the repair process using Polyvance’s Nitro Fuzer plastic welder, polypropylene welding rod, and 2000 Flex Filler epoxy filler.
STEP 1: ALIGN DAMAGE
Use 6485 2” aluminum body tape on the outer surface to align the damaged area. The outer surface should be as close to original as possible to minimize the need for filler, so if there are any dents or deformations, remove them with heat and pressure first.
STEP 2: CLEAN BACK OF PART
Spray a heavy, wet coat of 1001-4 Eco Prep or 1000 Super Prep on the backside. Let the solution sit for a few seconds and wipe dry with a clean paper towel.
STEP 3: SAND BACKSIDE
Sand the backside with 50 grit sandpaper to roughen the surface and to remove any paint overspray. Keep the speed low to avoid melting and smearing the plastic.
STEP 4: WELD BACKSIDE
Using R02-05 polypropylene wide ribbon and the nitrogen welder, weld the ribbon to the backside using the nitrogen welding process. Melt the base material and the bottom surface of the rod while applying a steady downward pressure to the rod. Let the weld cool.
STEP 5: GRIND FRONTSIDE
Peel the aluminum tape off the front. Using the 6122 carbide burr in an air die grinder, grind out a channel about 1/2” wide along the crack.
STEP 6: WELD FRONTSIDE
Using the R02-06 polypropylene thick ribbon, weld the ribbon into the v-groove on the front side. The R02-06 profile will provide the best strength on thick plastics; on thinner plastics use the R02-04 or R02-01 rod profiles.
STEP 7: SAND SMOOTH
After letting the weld cool completely, sand the rod on the front flush with 80 grit in a DA sander.
STEP 8: APPLY ADHESION PROMOTER AND FILLER
Spray 1050 or 1051 Plastic Magic Adhesion Promoter over any raw plastic areas exposed; allow 15 minutes for the solvents to evaporate. Mix and apply 2000 Flex Filler epoxy filler over the area to fill any low spots. Sand with 80 grit and progress to 320 grit prior to applying 3041 or 3043 All Seasons Waterborne Primer Surfacer.