Understand the PP inside your machine first, then choose the purging method that matches the machine, the color, and what the next job needs in quality
Bottle caps, transparent boxes and impact-resistant parts are all called PP, but their formulations and flow behavior differ. Choosing a PP purging compound therefore means looking at material, temperature, flow path and the problem at the machine together
Polypropylene (PP) is a semi-crystalline polyolefin thermoplastic — lightweight and highly formulable. But the word PP on a raw-material bag still cannot tell you how well that resin flows, how clear it is, or how much impact it takes
Non-reinforced PP grades are usually close to 0.9 g/cm3 in density, but fillers change both weight and properties. Integral hinges (living hinges) need a grade chosen and designed for repeated folding — not a property guaranteed for every PP part
Example grades and uses: Borealis PP datasheet · PP caps and hinges
Melt point describes the change of state; in-machine temperatures must suit processing; part service temperature depends on grade, time, load and conditions. So never conclude that every PP grade can go in the microwave or take the same sterilization
Chemical resistance must also be checked against chemical type, concentration, temperature and exposure time from the resin maker
HOMOPOLYMER
Mostly propylene polymer, usually picked for stiffness and dimensional stability — with impact resistance at service temperature checked alongside
Example jobs: Caps, general containers, woven tape, film and fiber per grade
Injection grades and tape grades can differ hugely in MFR, so one cannot substitute from the PP-H name alone
RANDOM COPOLYMER
Distributed comonomer tunes clarity, flexibility and melt behavior — for jobs balancing looks with mechanical properties
Example jobs: Transparent containers, packaging, and some pipe grades
PP-R for pipe and random PP for transparent boxes are different use-grades; clarity further depends on clarifier, thickness and cooling
IMPACT COPOLYMER
Has an impact-absorbing phase dispersed in the PP, usually called heterophasic or impact copolymer (block copolymer appears in the market)
Example jobs: Crates, tanks, auto parts and load-bearing parts
Check toughness at target temperature, MFR and stiffness together — impact does not make every grade equal
Read grade-by-process selection criteria: LyondellBasell — Material Selection: Polypropylene
Always separate PP type from color and color formulation first. Natural pellets may be dry-blended with masterbatch at the plant, or ordered as pre-colored compound — so the same color job can carry different formulations and requirements
Used as a coloring base or where clarity is wanted. Leftover old color and slight residue show easily — especially when switching from dark or reinforced jobs
Found in containers and parts with tight shade control. The next job may show streaks or specks clearly, so set color acceptance criteria before purging starts
Fits jobs needing dark color by design, e.g. crates or appliance parts. When moving to white or transparent, track color bleeding from the flow path — never judge from the first purge alone
For brand colors or product looks. Check masterbatch carrier, dispersion and part color criteria. There are colorants made for transparent PP too
Color does not certify food contact, medical grade or UV resistance — check the actual resin and color-formulation documents. Clarity and crystallization still shift with additives — Read about clarifiers, nucleators and PP colors from Milliken
Virgin is fresh material; recycled spans many sources and reprocessing routes; regrind is ground runners or parts reused. Record ratio, source, color and filler. Never judge quality or recycle status from black or grey color alone
If black specks hit several machines running the same material lot, check the regrind lot and masterbatch first. If the source still feeds the system, purging the barrel alone will not fix it permanently
Pick the resin grade from end-part properties together with in-machine behavior. Changing PP type or formulation usually means adjusting process conditions too, even when the material is still called PP
INJECTION MOLDING
High MFR often helps fill thin parts, but toughness and part geometry count too. Shrinkage and warpage involve crystallization, reinforcement, in-mold flow and cooling
So the PP type name alone cannot say which grade is fastest — nucleated formulations change crystallization speed; e.g. random PP designed for fast crystallization
Injection purging compound and machine-matched selection →EXTRUSION
Pipe, profile, film, sheet and fiber differ in needs. Jobs that must hold melt shape usually pick grades with suitable melt strength — not high MFR hoping for more output
Fiber is the exception to split out: meltblown PP runs very high MFR grades, so low-MFR-for-fiber never covers everything
Extruder and flow-path purging guide →Maker examples: Borealis — crystallization-tuned random PP · ExxonMobil — PP for meltblown · Milliken — nucleation vs cooling and shrinkage
MFR is the mass of melt flowing through the tester under set conditions, usually reported in g/10 min — not viscosity itself. Match test method, temperature and test weight before comparing. MFR screens grades but never fully replaces flow behavior in screw and mold
Faster filling does not always mean shorter total cycle time — cooling time, holding pressure and part ejection count too
Record the old job filler type and loading, check the flow path for leftover material or old color, and set next-part criteria (specks, surface, clarity). Reinforcement in PP and Glass Fiber in purging compound are different things — check the TDS on both sides
Picture switching from black PP to transparent containers: fresh material is in the hopper, but old color still sits in screw channels, the check ring, the nozzle and the flow path. Feeding new PP does not mean every section is clean at once
ASACLEAN purges old color or resin sitting in the system and cleans residue within each grade capability, and plans shutdown/sealing where the grade supports it. The goal is back to passing parts — measuring time, purging compound used and real scrap
For easy formulation switches the old method may suffice — compare against the site baseline. If color changes run long or residue returns, design a trial to see where purging compound helps — Understand residue purging vs material chasing
Moving from high-temp resin down to PP: sequence the material chase and adjust temperatures — never drop temperature or feed purging compound expecting it to be safe by itself. Read the high-to-low resin change guide and have technicians confirm against the actual resin manual
Black specks may come from old flow-path residue — but also from contaminated material or regrind, dust, or mold vents. Purging compound may be the main fix, a helper, or not the root-cause fix at all
Check black-speck causes before picking a grade →If residue returns fast, check root cause and usage method together — never step up grade strength on symptoms alone
This section points at which grade to consider first — before real use, re-check machine, site temperature and flow-path limits
UP / newUP / CP run in the range 170–300°C This is the purging compound range — not a production-temperature recommendation for every PP
Check injection / extrusion and Hot Runner; blow or other machine types need technician assessment of the real process
Color change, transparent jobs, or cost? For specks or heavy residue, diagnose the cause first
Consider first for color or material changes in general PP — a PP-specific grade that PP itself purges out easily
ASACLEAN UP details →Consider first when entering transparent or unreinforced PP and controlling purging-compound residue
ASACLEAN newUP details →The cost-side option for PP — but test that quality, time and usage fit the job; never judge on price per kilo alone
ASACLEAN CP details →All three support Hot Runner per TDS terms and allow shutdown/sealing. Entering transparent PP, changing filler formulation, or heavy residue may need different purge sequencing
Open Grade Explorer for PP and check further terms →UP / newUP / CP need at least 0.5 mm passage. Verify actual gates and clearance, plus TDS temperature and residence terms, before use
Above 280°C, max 30 min residence. Never use sealing capability as an excuse to ignore this limit
Hot Runner purging guide →Look at old → new color, shot weight vs barrel capacity, dead spots, plus back pressure and screw speed. Adjust per machine spec and TDS method — no single setting fits every machine
Back pressure and screw speed settings during purging →Grade data references the UP, newUP and CP TDS — open each grade page for limits and the full document
Shutdown reads Scheduled purging and sealing For cost assessment use the purging-compound savings calculator with real site figures
Sometimes — but only counts if parts pass real criteria. If color hangs or scrap stays high, compare purging compound against the old method in a controlled trial.
newUP is the starting point for low-residue PP, but old contamination, machine, temperature and flow-path limits must be checked first — some jobs need carbon cleaning before the low-residue chase step.
No — color is formulation; homopolymer, random and impact describe polymer structure. Read the grade code and datasheet to identify the material.
Baseline your current method first: time used, resin discarded, shots until pass. Then look at old–new color pair, shot weight vs barrel capacity, flow-path dead spots, and back-pressure/screw-speed settings — then trial purging compound under controlled conditions and compare against baseline.
Describe the old and next job so we can see it — technicians will check where purging compound fits, what to measure for value, and quote on actual usage