氯丁橡胶加工配合指南（英）

Technical Information ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ A Guide to Grades, Compounding and Processing of Neoprene Rubber Inherent Properties of Neoprene Neoprene, the world’s first fully commercial synthetic elastomer, was introduced by DuPont in 1931. Since then it has established an enviable reputation for reliable service in many demanding applications. Based upon polychloroprene, alone or modified with sulphur and/or 2,3 dichloro 1,3-butadiene, Neoprene is a true multipurpose elastomer thanks to its balance of inher- ent properties, which include: • Outstanding physical toughness • Wider short- and long-term operating temperature range than general-purpose hydrocarbon elastomers • Resistance to hydrocarbon oils and heat (ASTM D2000/SAE J200 categories BC/BE) • Resistance to ozone, sun and weather • Better flame retardant/self extinguishing characteris- tics than exclusively hydrocarbon-based elastomers As with all elastomers, properties inherent in the base polymer can be enhanced or degraded by the com- pounding adopted. This concise guide will assist in the development of compounds with optimum service life which will process smoothly and economically. More detailed information on the available grades of Neoprene, processing and compounding for specific end-uses and specifications is available in a wide range of literature. Handling Precautions DuPont Dow Elastomers is unaware of any unusual health hazards associated with any Neoprene solid polymer. For all the solid polymers, routine industrial hygiene practices are recommended during handling and processing to avoid such conditions as dust buildup or static charges. For detailed information, read “Guide for Safety in Handling and FDA Status of Neoprene Solid Polymers,” and observe the precautions noted therein. Review current Material Safety Data Sheet (MSDS) for polymers and ingredients prior to first use and upon revisions. Before proceeding with any compounding work, consult and follow label directions and handling precautions from suppliers of all ingredients. Specify dust-free dispersions of all potentially hazard- ous ingredients. Ensure that local environmental and workplace handling requirements are met. Refer also to comments on specific compounding ingredients in the safe handling guide. Selection of Neoprene Type and Grade The various grades of Neoprene fall within three types, e.g., G, W and T. Within each type lies a series of grades that differ primarily in resistance to crystalli- zation and Mooney viscosity. Selection of type and grade is usually based upon a combination of four factors: Product performance Defined by the most important physical properties for optimum service life, e.g., tear and flex resis- tance (belts), compression set and stress relaxation resistance (seals, bearing pads), high and low temperature resistance (CVJ boots). Crystallization resistance As dictated by product operating temperatures and/ or processing needs. Mooney viscosity Suitable for the intended processing operations with the necessary form of compound. All DuPont Dow Elastomers grades of Neoprene have a viscosity measured using the ten pass method (N200.5700) and are measured ML 1+4 at 100°C. Building tack Ease of lamination in processing, where necessary. Basic characteristics of the three types are summa- rized in Table 1, with details following. Additional information may be found in individual product bulletins. Rev. 3, Jan. 2004 2 Types of Neoprene G-Types Characteristics that differentiate G-types derive from their manufacture by the copolymerization of chloro- prene with sulphur, stabilized or modified with thiuram disulfide. They have wider molecular weight distribu- tions than W- or T-types. As compared with W-types, Neoprene G-grades: • Can be mechanically or chemically peptized to a lower viscosity, hence can provide workable more highly loaded stocks with minimum plasticizer levels. Neoprene GW is essentially non-peptizable, which is the one notable exception. • Are more tacky and less nervy, with the exception of gel-containing polymers. These properties lend themselves to extrusion, frictioning, calendering and building operations, as in hose and belt manufacture, and minimize knitting and backgrinding problems in molding • Have more limited raw polymer storage stability • Fully compounded, are more susceptible to total heat history in processing and storage time (i.e., are more prone to viscosity increase and reduction of scorch time) • Do not normally require organic accelerators. • Have highest tear strength, especially GRT and GW • Impart highest flex fatigue resistance, higher elongation and resilience and a “snappier” feel to vulcanizates Characteristics of Individual Grades Medium crystallization speed Neoprene GNA-M1 A moderate viscosity and crystallization resistant polymer, thiuram disulphide stabilized and containing a staining secondary amine for improved polymer stability. Slow crystallizing Neoprene GW An optimized sulphur-modified polychloroprene with improved storage and mill breakdown resistance similar to W-types but without the need for organic accelerators. Tear strength, resilience and flex crack resistance are those of G-types. Heat resistance approaches thiourea cured W-grades. Compression set resistance lies between that of traditional G and W variants. Neoprene GRT A sulphur copolymer with good crystallization resis- tance. Has the best green tack of any Neoprene and is used extensively for frictioning, or where good building tack is required. W-Types As compared with Neoprene G-types, W-grades: • Are more stable in the raw state • Mix faster but cannot be mechanically or chemically peptized • Require organic accelerators. By selection of type and level, they offer greater latitude in processing safety and cure rate • Are less prone to mill sticking and collapse on extrusion • Offer superior vulcanizate heat and compression set resistance • Accept higher levels of filler for a given level of compression set or tensile strength, hence can yield more economical compounds • Can yield non-staining, non-tarnishing vulcanizates • Show improved color stability Table 1 Characteristics of Neoprene Types G W T Raw Polymer Limited storage stability Excellent storage stability Excellent storage stability Polymer and compounds Non-peptizable Least nerve, non-peptizable peptizable to varying degree Need acceleration Fast curing but safe processing Best extrusion, calendering performance Accelerators usually not necesary Need acceleration Highest tack Vulcanizates Best tear strength Best compression set resistance Properties similar to W-types Best flex Best heat aging Best resilience 3 Characteristics of Individual Grades Fast crystallizing Neoprene W A stabilized, rapid crystallizing chloroprene polymer with good raw stability. Accelerated with ethylene thiourea (ETU), provides excellent heat and compres- sion set resistance. Neoprene WM-1 Lower viscosity Neoprene W for improved processing in highly loaded compounds and lower processing temperatures. Neoprene WHV High viscosity Neoprene W for low cost, highly extended compounds or to raise the viscosity and green strength of lightly loaded or highly plasticized compounds. Neoprene WHV-100 Slightly lower in viscosity than WHV. Medium crystallization speed Neoprene WB Polychloroprene containing a high proportion of gel for exceptionally smooth processing and very low nerve. Used in blends, typically to 25%, Neoprene WB gives high quality calendered sheet and smooth, collapse- resistant extrusions with low die swell. Vulcanizates based upon WB resemble those from other W-types for heat, ozone, oil and compression set resistance but give lower tensile and tear strengths and flex crack/cut growth resistance with preferred W-type cure systems. Very slow crystallizing Neoprene WRT A copolymer offering the maximum crystallization resistance. It can require up to 50% more accelerator to achieve the cure rate of Neoprene W. Vulcanizates have rather lower tensile and tear strengths as com- pared with W. Neoprene WD A high viscosity, crystallization resistant analogue of WRT used where high levels of plasticizer would cause excessively soft compounds with that polymer. T-Types Neoprene T-types effectively combine the smooth processing of WB with the tensile properties of Neoprene W. The three grades are: Fast crystallizing Neoprene TW Generally analogous to W but providing faster mixing, smoother extrusion and calendering with slightly better crystallization resistance. Neoprene TW-100 Higher viscosity TW for greater extension without loss of processing advantages. Very slow crystallizing Neoprene TRT An analogue of WRT but with improved processing and crystallization resistance. At a Glance Polymer Selection Guide Tables 2, 3, 4 and 5 summarize basic details of the Neoprene types and grades. As previously indicated, there is a wide range of bulletins and data sheets covering the products themselves, compounding, processing and end-use performance. These should always be consulted prior to commencing work with Neoprene. Basic Principles Balanced compound based upon Neoprene G-, W-, or T-types will normally contain most of the classes of ingredients indicated in Table 5. Acid Acceptors High-Activity Magnesium Oxide (Magnesia) The primary function of the metal oxide is to neutralize trace hydrogen chloride that may be liberated by Neoprene during processing, vulcanization and heat aging or service. By removing the hydrogen chloride, it prevents auto catalytic decomposition hence greater stability. Magnesium oxide also takes part in the vulcanization (cross-linking) process. Use of 4 parts magnesium oxide and 5 parts zinc oxide generally results in a good balance of processing safety and cure rate and is typically used. Higher levels of magnesia may be desirable for high temperature molding, by injection. Lower levels of magnesia (2 pphr) may be used in some continuous vulcanization cure systems. Suitable grades of magnesium oxide are fine particle precipitated calcined types with a high surface activities measured by iodine number prefer- ably above 130. Surface activity indicates the ability of the oxide to absorb or react with hydrogen chloride, hence the higher the value, the greater the processing safety and vulcanizate properties, especially with G-types. Neoprene G-type Mooney Scorch times ranging from 54 down to 16 min for 10 pt rise at 121°C have been recorded, directly related to the activity of the magne- sium oxide incorporated. 4 Table 3 Neoprene W-Types Raw polymer Non-Peptizable Compounds Excellent storage stability Need accelerators Vulcanizates Excellent heat resistance Best compression set resistance Lower modulus Grades ML4 — 100°C Features W 40–49 General purpose (F) WM-1 34–41 Low viscosity W (F) WHV 106–125 Highest viscosity W (F) WHV-100 90–110 Lower viscosity WHV (F) WB 43–52 Gel-containing, smooth processing (M) WRT 41–51 Maximum crystallization resistance (VS) WD 100–120 High viscosity WRT (VS) (F) = Fast crystallizing (M) = Medium crystallization speed (S) = Slow crystallizing (VS) = Very slow crystallizing Table 4 Neoprene T-Types Polymer, Compounds and Vulcanizates Basic properties of W-Types with the smooth processing Least nerve Non-peptizable Grades ML4 — 100°C Features TW 42–52 Smoother processing than W (F) TW-100 82–99 Higher viscosity TW (F) TRT 42–52 Smoother processing than WRT (VS) (F) = Fast crystallizing (VS) = Very slow crystallizing Table 2 Neoprene G-Types Raw polymer Peptizable (except GW) Compounds Best tack Fast curing without accelerators Limited storage stability Vulcanizates High tear strength Best flex crack/cut growth resistance Moderate heat resistance Moderate set resistance Grades ML 1+4 at 100°C Features GNA-M1 42–54 Better raw polymer stability (M) GNA-MZ 47–59 GW* 28–49 Balanced blend of G & W properties, non-peptizable (S) GW-M1 28–38 GW-MZ 37–49 GRT* 30–52 High crystallization resistance/tack (S) GRT-M0 30–42 GRT-M1 34–46 GRT-M2 40–52 (M) = Medium crystallization speed (S) = Slow crystallization *These ranges are maximum for the type. Subgrades with narrower viscosity ranges are available. 5 Table 5 Compounding Ingredients for Neoprene Class Typical Acid Acceptor Metal oxides (1) High-activity magnesium oxide, MgO (2) Red lead, Pb3 O4 Vulcanizing Agent Zinc oxide Vulcanization Accelerator (1) Thioureas for W and T-types, sometimes G (2) Sulphur-based for W-types Vulcanization Retarder MBTS in G-Types, CBS, TMTD or MBTS in W-types Antioxidant Octylated diphenylamine Antiozonant Mixed diaryl-p-phenylene diamines with selected waxes, to 3 phr Fillers Carbon black; precipitated silica; calcium silicate; hydrated alumina; china clay Plasticizers Aromatic or naphthenic process oils; mono esters; polyester; chlorinated waxes Processing Aids Stearic acid; waxes; low molecular weight polyethylene; high-cis polybutadiene; special factices To prevent loss of surface activity in storage due to pick up of atmospheric moisture or carbon dioxide, purchase in hermetically sealed sachets is recom- mended, as offered by most suppliers of high activity rubber grade of magnesium oxide (Mooney scorch time at 121°C has been halved by exposure of magnesia to 50% relative humidity for 24 hr). Alternatively, there are a number of commercial dispersions, typically 75% active powder, that exhibit good storage stability. However, these may contain magnesia with a lower surface activity, hence care should be taken in demanding conditions. They may also contain surfactants that can impair water resistance. Red Lead For improved water resistance, a lead oxide, usually 20 parts of red lead Pb3O4, may replace the magnesia/zinc oxide combination. For health reasons, it should always be added as a dispersion, 90% in EPDM. Owing to more limited reactivity with hydrogen chloride, stabilization is less efficient hence use is confined to Neoprene W- or T-types with safe curing systems. Calcium Stearate This substance has a limited use as an acid acceptor. Replacement of 4 parts magnesium oxide by an equimolar quantity (5.4 parts) of calcium stearate can retard hardening on heat aging and may be useful where specifications call for hardness increase of 5 pt or less after 7 days at 100°C. Vulcanizing Agent A good rubber grade of zinc oxide should be specified to minimize differences in curing activity. Vulcanization Accelerators As previously indicated, Neoprene G-types do not normally require an organic accelerator to develop a good state of cure at acceptable rates. For faster cure, 0.5 parts active ethylene thiourea (ETU) added as a dispersion is suggested. Predictably, increased rate and state of cure, and reduced scorch resistance, are proportional to the amount added. All Neoprene W- and T-types require an organic accelerator. Table 6 lists the common systems in order of increas- ing cure rate and decreasing processing safety. The best balance of vulcanizate modulus, resilience, compression set and heat aging is normally given by ETU. Processing safety can be improved by adding CBS or TMTD in carbon black stocks, or MBTS with mineral fillers such as china clay. Where ETU is unacceptable even in dispersed form, use of Neoprene GW without accelerator may be considered where ultimate compression set resistance is not required. At 170–180°C cure is usually suffi- ciently fast even for injection molding. Alternative proprietary accelerators include dimethyl ammonium hydrogen isophthalate, Vanax CPA. This may require higher amounts for equivalent cure rate. Information on ETU-free alternatives are available on request. Other possibilities include the TMTM, DPG or DOTG/ sulphur systems where maximum resistance to heat or compression set above 70°C is not required. The best property balance is obtained using sulphur at 0.5–0.75 parts with accelerator levels at 0.75–1.0 part of each. Scorch resistance and bin storage stability are good. Addition of 0.3–0.5 parts ETU gives a fast cure 6 rate with processing safety. For continuous vulcanization up to 200°C or acceptable cure cycles at below-normal temperatures, up to 2 parts DETU or DPTU may be specified. Such stocks are impractically scorchy for normal processing. Heat history must be kept to a minimum and refrigerated storage is advised. Water resistant Neoprene compounds containing red lead normally employ 0.5–1.0 part each of TMTM and sulphur as cure system. Acidic filers promote poor scorch and bin storage stability. Preferred ingredients are furnace blacks or non-acidic clays. Although they give very low compression set and good processing safety, peroxide cures promote poor heat aging with Neoprene, even when high levels of efficient antioxidants are incorporated. They are rarely used. Table 6 Acceleration Systems for Neoprene W- and T-Types Ingredients Parts per 100 Neoprene Primary use A. Stocks containing 4 parts MgO, 5 parts ZnO TMTM 0.5–1.0 DOTG 0.5–1.0 Maximum processing safety Sulphur 1.0–1.5 ETU* 0.55–0.75 Mineral filler loading MBTS 0.5–1.0 ETU* 0.4–0.75 Carbon black loading TMTD or CBS 0.5–1.0 TMTM 0.5 DOTG 0.5 Medium to fast cure with moderate processing safety Sulphur 1.0 ETU* 0.2–0.4 ETU* 0.4–0.75 Maximum economy Optimum heat/compression set resistance Methylthiazolidinthion 0.4–1.5 Substitute for ETU (CRV or MTT) Sometimes inconsistent cure, use higher level for high carbon black loading. Tributyl thiourea* 3.0 Excellent set and ozone resistance, non-stain Trimethyl thiourea* 0.75–1.5 Excellent compression set resistance Epoxy resin 1.0–2.0 Salicylic acid 1.0–2.0 High elongation/tear strength Low discoloration under lead Diethylthiourea* 1.0–2.0 Fast high temperature cures (LCM) (DETU) Practical cures at lower temperatures DPTU* 1.0–2.0 As DETU (Thiocarbanilide) Dicumyl peroxide (40%)* 1.5–2.0 Excellent set resistance and processing safety N,N'-m-phenylenedimaleimide 1.5 (Poor heat aging with 4.0 magnesium oxide and 5 pphr zinc oxide) B. Stocks containing 20 parts red lead, Pb3O4*, no MgO or ZnO TMTM 0.5–1.0 Best water resistance Sulphur 0.5–1.0 Bin storage stability with alkaline fillers *Active ingredient level. To be used as a dispersion. Vulcanization Retarders In Neoprene G-types, up to 1 part MBTS is an effective retarder. It may also be added to allow processing of overaged polymer. MBTS, CBS or TMTD are effective retarders in Neoprene W- and T-types. Examples are given in Table 6. Antioxidants and Antiozonants Unlike unsaturated general purpose elastomers, Neoprene has inherent resistance to attack by oxygen, ozone, heat and light. However, long term optimum service performance requires the addition of an effec- tive antioxidant and antiozonant. Among possible antioxidants, octylated diphenylamine, 2–4 parts, is preferred as it imparts the best heat stability, has no effect upon scorch or bin storage and is relatively nonstaining. Ketone amine and quinoline 7 based types seriously affect scorch and bin storage and must be avoided. Effective antiozonants tend to adversely affect process- ing safety and to promote staining. Among para- phenylene diamine derivatives, mixed diaryl para- phenylene diamine has only a slight effect upon scorch and bin storage and gives the best balance of long term protection, being non-extractable in water and of low volatility. However, all PPD derivatives may cause migratory and contact staining of painted surfaces. Given the limited options for effective nonstaining antiozonants, it is suggested that a DuPont Dow Elastomers technical representative be consulted if one appears to be required. Reinforcing and Extending Fillers Carbon Blacks As with all elastomers, Neoprene requires the addition of appropriate reinforcing fillers to achieve the re- quired balance of processability, hardness and tensile or tear properties. The most widely used is c