In the thermoplastics industry, a purging compound is a compound specifically designed to efficiently clean thermoplastic processing machinery of leftover resin and other contaminants that build up on interior processing surface. Purging compounds most commonly use a resin base which allows them to be loaded and processed similarly to resin when performing the purging process. Effective purging compounds are designed to work on a variety of machinery, over a substantial range of temperatures, and with a wide range of materials. Purging compounds are designed to require the least amount of material and time to effectively purge leftover resin and contaminants. This has allowed purging compounds to replace existing costly and time-consuming methods of cleaning thermoplastic processing machinery used in modern plastics manufacturing. Purging compounds are a cost effective and time efficient method to maximize the uptime of your machinery while minimizing wasted resin and defective plastic parts.
Types of Purging Compounds
Purging compounds can be separated into two main types based on their mechanism of action. Some modern purging compounds, such as those in our Purge Right™ series, use a combination of mechanical and chemical interaction to most effectively purge processing surfaces.
- Mechanical Purging Compounds – Mechanical purging compounds primarily
force to purge contaminants from processing surfaces. utilize shearing compounds can also utilize differences in material viscosity Mechanical purging with residual resin and other contaminates to purge them or bond surfaces. Many mechanical purging compounds are abrasive from processing they are expected to wear processing surfaces during their which means . As purging compound manufacturers work towards providing the cleaning action solutions for purging many non-abrasive mechanical most cost-effective are now available. These non-abrasive purging compounds purging compounds wear of processing surfaces, but this wear is within the range still cause would be expected to experience from normal operation. the machinery
- Chemical Purging Compounds – Chemical purging compounds operate by utilizing
chemicals to break down bonds between the various heat activated processing surfaces. Chemical purging compounds often require a contaminants and of “soak” time, commonly between 5 and 30 minutes, to short period purge contaminates. While almost all mechanical most effectively purging compoundsare solid you can expect to find both solid and liquid chemical purgingcompounds.
Uses for Purging Compound
- Clearing Residual Plastic Material Between Batches – The most common usage of purging compound is to remove remnant
between batches of resin. When processing resin for plastic material not all of the resin ingested by the hopper makes it all thermoplastic manufacturing the waythrough processing and can carry color and other properties into subsequentbatches of plastic parts. Purging compound can produce clean articlesfree of discoloration and other properties from previous resin in aslittle as a few cycles.
- Clearing Contaminants – When doing a lengthy production run with many
loads ofthe same batch of resin you may need to utilize purging compound to resolvecontaminant buildup. Contaminants build up on the processing surfacesof thermoplastic machinery as a result of the chemical changes in material which does not fully pass through the system as plastic it continuesto heat up. Purging compound can clear these deposits of contaminantssuch as carbon buildup in addition to cleaning any plastic material. Keeping your processing surfaces free of contaminant will keep blackspots and other defects that result from the buildup of contaminant outof your plastic parts.
- Contaminant Prevention – Depending on the operating specifications of
your machineryand the resin materials you work with you may find the need to clearmachinery of any leftover resin or contaminant before or after shutdown. When residual plastic and contaminants are left to cool after machineoperation, they can harden and become difficult to remove. Once thishardening has occurred this can increase the difficulty of resolving buildupthrough the use of purging compounds. The hardened contaminants canalso lead to a reduced lifespan of parts and can require disassembly andmaintenance of the machinery for a full cleaning.
Thermoplastic Machinery that Utilize Purging Compound
- Injection Molding– Injection molding is the least
restrictive thermoplasticmanufacturing process and can be easily adapted for use with awide variety of parts of varying complexity and size. Injection molding oftenutilizes molds with multiple parts creating many narrow channels betweenthose parts known as runners. These narrow runners can quickly fillwith contaminateand become a bottleneck requiring disassembly and maintenance. Regular use of purging compound keeps narrow channels free of removes the need for maintenance just to clean these problem areas. contaminateand
- Hot Runners – Hot runners are injection molds that utilize a
to feed multiple injection nozzles that equally heatmanifold distribute plasticmaterial to different areas of a mold. The plastic material is heatedto a high temperature in the heat manifold to aid in even distributioneven during quick cycles and then quickly cooled once injectedinto the mold. This combination of having higher temperature plasticmaterial, multiple points of injection, and accelerated cooling allowfor quick cycle times to be obtained. This thermoplastic manufacturingprocess is particularly effective with more complex molds as itallows the plastic material to evenly distribute within the mold variouscavities.
- Blow Molding– The blow molding process injects plastic
material intoa mold with a single large cavity while also maintaining an interior cavitywithin the plastic material. This internal cavity is then filled withair forcing the plastic material into the shape of the mold. Though theyare most commonly used to create plastic containers such as bottles and barrelsany object with a significant cavity can be a candidate for blow molding.
- Extrusion – Extrusion is used to produce linearly uniform parts with a
continuous profile. Extrusion can produce parts with complex cross-sections, and workswell with brittle, hard materials. Purging compounds effectively cleanscrews, heads, and barrels without the need for costly disassembly.
Benefits of Purging Compound Usage
Purging compounds were formulated primarily as an efficient alternative to existing methods of cleaning thermoplastic processing machinery. Before purging compounds were introduced into the market the next batch of virgin resin or reground plastic, also known as regrind, was most commonly used to clear any residual plastic material left in the machinery from the previous batch of resin. When a new batch of resin was introduced plastic parts were visibly checked for defects and discoloration until the machinery was thought to be sufficiently cleared of the previous resin. This method is very wasteful of otherwise useable resin and results in considerable downtime while still requiring machine operation. This method also does little to prevent any buildup of contaminants that form as a byproduct of processing such as carbon deposits. These byproducts would eventually require disassembling and cleaning the machinery to properly maintain them.
- Ease of Use – Modern purging compounds have been widely
adopted becauseof their ease of use. We provide products that easily fit into yourexisting workflow and work with existing equipment without modification. Most purging compound usea resin base, so their use differs littlefrom how you would normally load and process resin. As they are so easyto use purging compounds are able to seamlessly integrate with your existing productionprocedures.
- Increase Machine Uptime – Using purging compounds greatly reduces
machine downtimecompared to using virgin resin or regrind by reducing the time requiredfor effective cleaning. When cleaning out residual plastic materialbetween batches the reduction in time is significant. Though exacttiming varies due to variables such as machine capacity, material properties, processing temperature, and intervalbetween cleanings you can expectpurging compound to take between 5 and 15 minutes to effectively clearremaining plastic material and contaminate buildup. Purging compounds alsosignificantly reduce downtime by allowing contaminants to be cleared withoutrequiring disassembly and maintenance. Our customers typically see anoverall reduction in machine downtime of 60% – 80%.
- Cost Savings – If you are currently using virgin resin or
regrind toclear machinery purging compound can offer a cost-effective solution foryour business. Though the cost of purging compound may be more expensiveby weight then virgin resin and is often more expensive then regrindutilizing purging compound is still an overall cost savings. When comparingthe amount of purging compound needed to effectively clear plasticmaterial to the amount of virgin resin or regrind needed purging compoundoffers a costsavings. The real cost benefit of purging compoundsbecomes apparent when you consider the cost savings that however result fromthe clearing of contaminates. Every time you run purging compound throughyour machinery you will be clearing contaminants that would otherwiserequire disassembly and cleaning which can have significant costsdue to labor and machine downtime. Additionally, many parts can see anincrease in lifespan due to being more consistently cleaned which resultsin further cost savings.
- Cleaning Efficacy – In addition to their advantages in cost and
speed purgingcompounds also do a far more complete job of clearing thermoplasticmachinery than existing methods. Though using virgin resin orregrind will eventually clear much of the remnant plastic material from aprevious batch it does little to clear contaminants that build up over time. Using virgin resin or regrind also simply replaces existing plastic materialwith remnantplastic material of the current batch. Purging compoundscan effectively clear contaminants in addition to completely clearingplastic material and not just replacing the existing material withnew remnants.
- Reduction of Defective Product – Contamination may pose a risk to the long-term
life ofyour machinery and components – but the more common concern is in plasticpart contamination. Black specks and streaks are common reasons to rejectplastic parts. When using dated methods of clearing machinery of contaminants, they are thought to be an unavoidable part of the process. In addition to visual defectsresidual plastic material and other contaminantscan cause structural weakening of parts due to effects such asthe uneven filling of mold cavities. These structural weaknesses can causeissues with your product that are hard to verify from visual inspectionand require extensive and costly testing. With regular use of purgingcompound during long production runs in addition to purging between batchesof resin you can significantly reduce these defects in most applications. Our customers have generally experienced a 40% – 50% reduction in scrap produced as a result of defectiveproduct.
Choosing the Right Purging Compound
If you are considering seeing if purging compound is right for your business the first step is to find the right purging compound for your unique application. We make this easy as our Purge Right ™ line of compounds is designed to cover the widest variety of machinery, operating temperatures, and materials that we can without sacrificing quality. We are happy to work with you from helping you choose the right product for your business to formulating new compounds that fit your unique needs. If you don’t see a compound that fits your exact needs, or you have any questions please send an email to [email protected] or fill in the contact form at the bottom of this page.
- Purge Right ™ PR-5000 – Our most popular product that includes both
mechanical andchemical cleaning agents. PR-5000 utilizes four distinct allowing it to cover a temperature range of 340F to 610F. PR-5000 can be used effectively for injection molding with hot runner manifolds, blow molding and all types of extrusion processes. chemical agents
- Purge Right ™ PR-6000 – This compound offers all the benefits and ease of
use ofour PR-5000 compound but with an added agent for additional mechanical cleaning. This product works great for applications that need cleaning power like heavy colorant using liquid colors, some additional like screws and barrels, and complex molds with difficult worn components problem areas. to reach
- Purge Clear ™ PRC-7000 – Formulated specifically to work
using clear resin. PRC-7000 uses a water carrier for the with applications most effectivemeans of preventing cloudiness, black specs, or hazing in your clearproducts.
- Purge Clear ™ PRC-8000 – The second in our Purge Clear™ line of products has
the samegreat performance of our PRC-7000™ compound withan acrylic carrier. Developed specificallyfor use with machinery that processes clear acrylic such as headlightenclosures.