Processing Hypalon - inforubber.com

1 Technical Information Processing Hypalon This technical information presents some guidelinesfor consistent, satisfactory Processing of compoundsof Hypalon synthetic rubber . Processing Hypalon in arubber products plant may be defined as the entireseries of operations beginning with the arrival of theraw material on the receiving dock and continuinguntil the finished product is in the warehouse readyfor shipment. Since most dry compounding andprocessing is done with Hypalon 40, or one of itsviscosity variants, the bulk of the discussion is basedon these the exception of the coating grades, all types ofHypalon can be mixed in internal mixers and, forhighly loaded compounds, this is the only practicalmixing method. Most compounds are one-pass mixedusing the upside-down technique. When the mix iscomplete, the batch should be dropped on a sheet-offmill, quickly cooled, and stored in a cool, dry wide variety of compounds are extruded using bothcold and warm feed equipment.

2 Cold feed, long barrelextruders take compounded strip at ambient tempera-tures, whereas warm feed, short barrel extruders arefed strips of stock previously warmed on a volumes of compounded Hypalon are calen-dered into sheets for pond or landfill liners andsingle-ply roofing. Hypalon 45 is particularlysuitable for liners and roofing, while the generalpurpose polymers are preferred for other practices for compression, injection,and transfer molding are all similar, but the curesystem, acid acceptor, and process aid packagesshould be carefully selected based on the propertiesrequired and important machine/mold surface consid-erations. For good transfer molding, it may be neces-sary to prewarm the preforms. For reciprocatingscrew injection molding presses, it is desirable to usea lower viscosity compound to give the best feed andinject properties. The cure rate and machine condi-tions must be balanced for stock scorch versuscomplete mold and maleimide cured compounds of Hypaloncan be vulcanized in steam autoclaves, CV steamtunnels, air ovens, microwaves, and LCM cures are desired for continuous curing opera-tions to get maximum throughput.

3 When there is nopressure on the extrudate during cure, a high viscositypolymer, an effective desiccant, and a vacuumextruder should be used to eliminate porosity. Perox-ide cured compounds can be cured in steam auto-claves (if all the air is purged before curing starts) orCV steam tunnels, but peroxide compounds are notused in air or microwave ovens because of manner in which Processing of Hypalon 45 andHypalon 48 differs from that of Hypalon 40 is re-viewed in a section at the end of the bulletin. Hypalon20 and Hypalon 30 are normally processed as solventcoatings, and are discussed in other PrecautionsSafe HandlingHypalon synthetic rubber contains low levels ofcarbon tetrachloride (CCl4) and chloroform (CHCl3)as residues from manufacturing. Carbon tetrachlorideand chloroform are classified by The InternationalAgency for Research on Cancer (IARC), the NationalToxicology Program (NTP), and the AmericanConference of Governmental Industrial Hygienists(ACGIH) as substances for which there is limitedevidence of carcinogenicity to humans.

4 Under theOccupational Safety and Health Act (OSHA), expo-sures to carbon tetrachloride must be kept below thepermissible exposure limit of 10 ppm and chloroformmust be kept below the permissible exposure limit of50 ppm. When large quantities of raw polymer arestored or processed in enclosed areas with restrictedair exchange or ventilation, the air must be monitoredfor carbon tetrachloride and chloroform; and, ifnecessary, ventilation must be supplied to complywith OSHA additional information concerning this and otherpotential industrial health hazards when handlingHypalon , see DuPont Dow Elastomers technicalbulletin H-68551-01 Toxicity and Handling Guide, and The Material Safety Data Sheet (MSDS).Compounding IngredientsCompounding ingredients, including peroxides andlead-based curatives, used with Hypalon to preparefinished products, may present hazards in handlingand use. Before proceeding with any compoundingor Processing work, consult and follow label direc-tions and handling precautions from suppliers of DisposalAll grades of Hypalon raw polymer exceed theregulated maximum leachate level for carbon tetra-chloride in the Environmental Protection Agency(EPA) toxicity characteristic leaching procedure(TCLP test); therefore, discarded polymer should beconsidered a Resource Conservation and RecoveryAct (RCRA) hazardous waste by anyone who gener-ates more than 220 lb of total hazardous waste(includes waste from all sources) at a site in acalendar level of residual carbon tetrachloride in com-pounds is less than in Hypalon because of dilution byother ingredients in the compound.

5 Compoundingingredients, processes, and applications vary signifi-cantly, so you will need to reach your own conclu-sions as to whether waste generated by your processexceeds TCLP regulatory limits subject to contains no lead, but lead containing materi-als are sometimes compounded with it. If lead can beextracted from the compound in amounts that exceedthe regulatory limit of EPA s TCLP test, then thecompounded waste is a RCRA hazardous waste(Federal Register, 3/29/90, p11862; 40 CFR ),and must be handled as such. The amount of leadextracted in the TCLP test will depend on the amountand type of lead compound present, other compound-ing ingredients, and compounding and/or curingconditions. If you have any questions, please contactyour DuPont Dow Elastomers sales Characteristics of HypalonHypalon is the trademark assigned to a group of sulfurand peroxide curable elastomers that are based onchlorosulfonated and chlorinated polyethylene.

6 Thesepolymers are manufactured in such a manner as toproduce an elastomer with a completely saturatedbackbone and pendant groups suitable for variedapproaches to vulcanization. As a result of thisconfiguration, vulcanizates of Hypalon syntheticrubber are extremely resistant to attack by ozone,oxygen and weather. In addition, properly preparedvulcanizates of Hypalon are outstanding in resistanceto deterioration by heat, oils, and many chemicals andfluids. However, there are chemical and physicaldifferences between the various types which affectprocessibility and properties. The compounder mustselect the type that will best produce the desired endproduct within the constraints of each unique manu-facturing principle features of each type are summarized inFigure Polymer ProcessingCharacteristicsThermoplasticit yUncured Hypalon synthetic rubber is more thermo-plastic than other commonly used elastomers.

7 It isgenerally tougher at room temperature, but softensmore rapidly as temperature is increased by workingon a mill or in an internal mixer. Viscosity tempera-ture relationships for Hypalon 40 and SBR are shownin Figure low viscosity of Hypalon 40 at elevatedtemperatures permits extrusions that are low in dieswell, smooth at fast rates, and sharply softness under slightly warmed conditions(40 C [104 F]), makes building operations practical,giving good ply adhesion and knitting without the useof tackifiers. However, because of this same softness,immediate cooling of extrusions is necessary toprevent distortion. Also, variations in stock tempera-ture may cause variable extrusion rates and calen-dered sheet with uneven gauge and a rough of either very soft or very stiff compoundscan be improved by using one of the other grades ofHypalon. The high viscosities of Hypalon 4085, andHPG-6525 help eliminate trapped air and blisteringduring Processing and curing of highly extended orlow durometer stocks.

8 They also help minimizedistortion of these compounds after extrusion andduring open steam curing. The low viscosity of 40 Spermits easier Processing of stocks containing highlyreinforcing fillers or small amounts TypesforSolution ApplicationsHypalon 20 For flexible substratesGood 30 For rigid substratesHard, glossy oil 48 Hard, glossy oil better low-temperatureproperties thanHypalon 30. Hypalon 48 Better oil modulus. Higher hardness. Good uncured properties. Hypalon 45 Excellent uncuredproperties. Better low- temperature flexibilityHigher hardness. Bettertear strength. Better heatresistance. HPG-6525 For highly extendedcompounds, lowercost heat and low-temperatureperformance. Hypalon 4085 for highly extendedcompounds,lower 40 Basic general purpose typeGood oil resistanceGood heat resistanceGood low-temperatureproperties. Hypalon 40S(Soft) for lightlyplasticized com-pounds, higherdurometer 1.

9 Selection Guide for HypalonResistance to BreakdownHypalon does not break down in the sense thatnatural rubber and sulfur-modified Neoprene typesdo. These rubbers undergo an irreversible chemicalchange (a reduction in molecular weight) when theyare worked. The reduction of toughness andboardiness that occurs as Hypalon is milled is strictlytemperature related, , temporary and means that compounds of Hypalon can bereworked without significant change in processingbehavior, as long as scorch is not a factor. It alsomeans that Processing operations should be consistentfrom batch-to-batch, if constant temperatures of thermoplasticity and lack of breakdown,compounds based on Hypalon tend to be dry and nontacky at room temperature, but warmed stock givesgood flow, knitting, and ply viscosity relationships for the general purposetypes, Hypalon 4085, 40, and 40S, are shown inFigure 3, along with viscosity temperature curves forHypalon 45 and 48.

10 Note that Hypalon 45 and 48 aremore temperature sensitive than any of the generalpurpose Hypalon 40 3. Viscosity/Temperature Relationship ofHypalon PolymersEffects of Compounding on ProcessingThe following paragraphs deal with those aspects ofcompound design which affect the processability ofHypalon. Compounding for specific performancecharacteristics is discussed more completely in othertechnical bulletins on Polymer Selection & StorageThe plasticity or viscosity of compounds of Hypaloncan be controlled, in part, by selecting the rightviscosity grade. Hypalon 40S is used to reduce theviscosity of stiff compounds that have low amountsof plasticizer or contain high structure carbon 4085 adds uncured strength to soft com-pounds that contain large quantities of plasticizers orcompounds that are highly viscosity, Processing characteristics and cure rateof raw Hypalon do not change appreciably undertypical storage conditions.