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Review of common rubber factory problems and published causes and solutions--part II.



Part I appeared in the August issue.

Extrusion

The following are some common problems associated with the extrusion process.

Die swell

Controlling die swell during extrusion is important in order to maintain good dimensional stability dimensional stability,
n See stability, dimensional.
 of the extrudate. The extent of die swell is very dependant on Adj. 1. dependant on - determined by conditions or circumstances that follow; "arms sales contingent on the approval of congress"
contingent on, contingent upon, dependant upon, dependent on, dependent upon, depending on, contingent
 the applied shear rate Shear rate is a measure of the rate of shear deformation:



For the simple shear case, it is just a gradient of velocity in a flowing material.
. If a higher shear rate is applied to a rubber compound during extrusion, the amount of resulting die swell will usually be greater. The amount of shear rate applied to a rubber compound is determined by the geometry of the die and the screw speed of the extruder. If the screw speed is reduced, the resulting die swell should also decrease (refs. 78 and 79).

Also, if the die land length is increased, then the level of die swell will decrease (ref. 80). The total work history and state of mix have a large effect on the degree of die swelling that the compound will experience (refs. 81 and 82). In addition, compounds based on higher loadings of carbon black (ref. 83) or higher structured carbon black (ref. 84) tend to display less die swell during extrusions. Furthermore, compounds based on less nervy rubber (discussed earlier), tend to impart less die swell to the compound.

Extrusion rate (melt fracture)

There is always a limiting factor A factor or condition that, either temporarily or permanently, impedes mission accomplishment. Illustrative examples are transportation network deficiencies, lack of in-place facilities, malpositioned forces or materiel, extreme climatic conditions, distance, transit or overflight rights,  (or factors) that limits the rate of extrusion (output) and the rate of production. For example, too fast an extrusion rate will cause a greater amount of viscous viscous /vis·cous/ (vis´kus) sticky or gummy; having a high degree of viscosity.

vis·cous
adj.
1. Having relatively high resistance to flow.

2. Viscid.
 heating that ultimately the cooling system cooling system: see air conditioning; internal-combustion engine; refrigeration.
cooling system

Apparatus used to keep the temperature of a structure or device from exceeding limits imposed by needs of safety and efficiency.
 will not be able to handle (ref. 85). Too high a temperature rise will lead to scorch and the corresponding appearance problems. Another limiting factor can be melt fracture. Melt fracture occurs when the rubber compound is extruded above its critical shear stress shear stress
n.
See shear.



shear stress

A form of stress that subjects an object to which force is applied to skew, tending to cause shear strain.
, where appearance problems begin (ref. 86). Still another limiting factor can occur with strain crystallizing polymers, such as compounds based on natural rubber or polychloroprene. When compounds based on strain crystallizing rubbers are extruded at a rate which is above the critical shear stress for these elastomers, then strain induced crystallization Crystallization

The formation of a solid from a solution, melt, vapor, or a different solid phase. Crystallization from solution is an important industrial operation because of the large number of materials marketed as crystalline particles.
 begins and appearance problems result (ref. 87).

Many times certain equipment changes can be implemented to improve extrusion output without hurting appearance. For example, using a high mastication mastication /mas·ti·ca·tion/ (mas?ti-ka´shun) chewing; the biting and grinding of food.
mastication
(mas´tikā´sh
 screw (ref. 88), using a longer extruder barrel length (ref. 89), using a gear pump A Gear pump uses the meshing of gears to pump fluid by displacement. They are one of the most common types of pumps for hydraulic fluid power applications. Gear pumps however are also widely used in chemical installations to pump fluid with a certain viscosity.  at the extruder head (ref. 90) or considering a pin barrel extruder (ref. 91) may improve extrusion output.

Of course, there are compounding techniques that have been used to improve extrusion outputs. Some of these techniques include: using a fast extruding grade of carbon black (low surface area) (ref. 92), using an appropriate processing aid (ref. 93) or selecting a faster extrusion grade raw elastomer elastomer (ĭlăs`təmər), substance having to some extent the elastic properties of natural rubber. The term is sometimes used technically to distinguish synthetic rubbers and rubberlike plastics from natural rubber.  (refs. 94 and 95), to name a few. In addition, using some of the new "ultra-clean" carbon blacks can also prevent appearance problems (ref. 96).

Appearance (surface smoothness of extrudate)

Appearance problems (roughness of the extrudate surface) can result in quality rejects by the customer, leading to high external failure costs. Thus, these appearance problems should be avoided.

As discussed earlier, one method of avoiding extrudate surface appearance problems is to keep the rate of extrusion significantly below the critical shear stress to avoid any melt fracture problems (ref. 97). Also, consider using an extruder with a longer barrel, which can improve the surface appearance of the extrudate (ref. 98). Extrudate appearance can also be improved by straining the compound with a gear extruder or "gear pump" (ref. 99). Torn edges can be reduced by using specially heated dies (ref. 100). Also, consider using a "high mastication screw" and modify the factory standard operating procedure standard operating procedure Medtalk A technique, method or therapy performed 'by the book,' using a standard protocol meeting internally or externally defined criteria; a formal, written procedure that describes how specific lab operations are to be performed.  to avoid "starving" the extruder (ref. 101). Reportedly, a Multi-Cut Transfermix cold-feed mixer-extruder provides extrudates with excellent appearance (ref. 102). (However, this solution will require some capital expenditure.)

From a compounding perspective, compounds which are designed to contain an optimal level of a high structure, low surface area, carbon black usually imparts a good surface appearance to their extrudates (ref. 103). In addition, compounding additives, such as certain processing aids (ref. 104), vulcanized vul·ca·nize  
tr.v. vul·ca·nized, vul·ca·niz·ing, vul·ca·niz·es
To improve the strength, resiliency, and freedom from stickiness and odor of (rubber, for example) by combining with sulfur or other additives in the presence of heat
 vegetable oil (ref. 105), talc (ref. 106) and certain liquid rubbers (ref. 107) have been reported to improve the appearance of the extrudate when used properly in the rubber compound. Also, in certain situations, small amounts of gelledrubber are claimed to improve the appearance of the extruded compound (ref. 108). Sometimes, the wise use of recycled rubber can reportedly improve appearance (ref. 109). Lastly, it is important to avoid excessively long bin storage times for mixed stock in order to minimize the formation of bound rubber content, thus preventing an increase in the yield stress which can lead to melt fracture and appearance problems (ref. 110).

Shear thinning A pseudoplastic material is one in which viscosity decreases with increasing rate of shear (also termed shear thinning). This property is found in certain complex solutions, such as ketchup, whipped cream, blood, paint, and nail polish.  

A rubber compound is non-Newtonian in that its viscosity will decrease with an increase in applied shear rate (a faster extruder screw speed). Another term for shear thinning is pseudoplasticity (ref. 111). However, different rubber compounds display different shear thinning profiles. Some rubber compounds display steeper drops in viscosity with a given rise in applied shear rate (faster screw speed) compared to other compounds which drop their viscosity less rapidly.

From a compounding perspective, it has been determined that the base elastomer(s) has a great effect on determining the degree of shear thinning that the compound will possess (refs. 112 and 113). The type and amount of filler loading used in a rubber compound has a large effect on the compound's shear thinning profile, as well (ref. 114).

Calendering calendering, a finishing process by which paper, plastics, rubber, or textiles are pressed into sheets and smoothed, glazed, polished, or given a moiré or embossed surface.  

The following are some common factory problems associated with calendering:

Blisters

The occurrence of blisters while calendering presents a quality problem (ref. 115). The following actions might be considered to reduce or eliminate blisters.

To reduce blisters, make sure that all raw elastomers and compounding ingredients are free of moisture and other volatiles (ref. 116). When milling, use a small friction ratio, reduce the gauge thickness of the rubber feed to the mill nip, and maintain a minimum milling rolling bank (ref. 117).

It has been reported that there are fewer blisters when calendering AEM AEM Applied and Environmental Microbiology (journal)
AEM Association of Equipment Manufacturers
AEM Academic Emergency Medicine (journal)
AEM Agnico-Eagle Mines Limited
AEM Advanced Engine Management
 terpolymers instead of the AEM copolymer copolymer: see polymer.  (ref. 118). Reportedly, butyl rubber butyl rubber: see rubber.  compounds can pose a special problem in forming blisters (ref. 119).

Calender CALENDER. An almanac. Julius Caesar ordained that the Roman year should consist of 365 days, except every fourth year, which should contain 366, the additional day to be reckoned by counting the twenty-fourth day of February (which was the 6th of the calends of March) twice.  release

Poor calender release of the rubber stock can cause significant quality problems in the factory. The following are some reported ideas to avoid some of these factory problems.

Try to keep calendar roll temperatures optimal for good release. Also, adding a small amount of low molecular weight, atactic atactic

pertaining to or characterized by ataxia; marked by incoordination or irregularity.
 polyethylene wax will usually promote better calender release (ref. 120). With polychloroprene compounds, the addition of a small amount of cis-polybutadiene rubber to the compound should also promote better calender release (ref. 121). In addition, it is reported that compounds based on star branched halobutyls will also display an improvement in calender release (ref. 122).

Molding

Molding is a very important factory process in producing various rubber products. The following discusses some of the various problems associated with molding operations.

Mold release

Achieving good mold release after the cure is very important. Poor mold release can hurt productivity levels and can sometimes cause quality problems. The following are some ideas to be considered to improve mold release.

One possible method of improving mold release is to pretreat pre·treat  
tr.v. pre·treat·ed, pre·treat·ing, pre·treats
To treat (wood or fabric, for example) beforehand.



pre·treat
 the mold with a Teflon coating (ref. 123). Sometimes silicone sprays and other mold release agents are applied directly to the mold surface; but these types of agents can destroy rubber-to-metal or rubber-to-rubber adhesion if used improperly (refs. 124 and 125). Also, it is not uncommon for compounding release agent ingredients, such as low molecular weight polyethylene, to be used with compounds based on polychloroprene or some other elastomer bases (ref. 126). It might also be mentioned that there may be a trend in the rubber industry to try to move away from the sacrificial sac·ri·fi·cial  
adj.
Of, relating to, or concerned with a sacrifice: a sacrificial offering.



sac
 agents and use more of the semi-permanent agents (ref. 127).

Compounds based on fluoroelastomers will many times contain a small part loading of carnauba wax carnauba wax

Very hard wax obtained from fronds of the carnauba tree, Copernicia cerifera, a fan palm of Brazil. During the regular dry seasons in Brazil, where it is called the tree of life, the carnauba palm protects its fanlike fronds from loss of moisture by secreting a
 to improve mold release properties (ref. 128). Also, sometimes increasing the stearic acid stearic acid /ste·a·ric ac·id/ (ste-ar´ik) a saturated 18-carbon fatty acid occurring in most fats and oils, particularly of tropical plants and land animals; used pharmaceutically as a tablet and capsule lubricant and as an emulsifying  level in compounds based on polyacrylates can improve these compounds' mold release characteristics (ref. 129).

Mold fouling

Fouling or buildup build·up also build-up  
n.
1. The act or process of amassing or increasing: a military buildup; a buildup of tension during the strike.

2.
 on the mold surface from repetitive curing of rubber parts can cause major problems. Sometimes, high mold fouling can cause excess fouled material to transfer onto the surface of the molded part, which can cause appearance problems or other quality defects. Also, high mold fouling can cause interference with heat transfer and impart an irregular surface to the cured rubber part (ref. 130). Many times, various cleaning procedures with solid particle blasting must be performed to remove mold fouling residues (ref. 131). These procedures are time consuming and costly. The following are suggestions on some ways to help prevent or reduce the occurrence of mold fouling problems.

Formulating rubber stocks to have better cured hot tear resistance (ref. 132), to have less cured bloom (ref. 133), and/or coating the mold surface with Telfon (ref. 134) are three ways to help reduce mold fouling. Sometimes curing at a lower cure temperature for a longer cure time or just using curing molds made of a better grade of steel may also reduce mold fouling (ref. 135). Even the selection of the base elastomer for the compound can greatly influence the tendency of the rubber compound to foul the mold during curing. For example, compounds based on natural rubber can have a high propensity to foul molds, while compounds based on polybutadiene might have less propensity to foul the same molds (ref. 136).

In addition, compounds that contain lower oil loadings might impart less mold fouling (ref. 137). Also, reportedly, using ultra-low structured carbon blacks instead of processing aids can reduce mold fouling (ref. 138).

To avoid mold fouling, consider avoiding certain mold release agents, which make fouling worse. On the other hand, consider using certain special compounding additives such as PPA-790, which might reduce mold fouling in certain situations (ref. 139).

Non-fills

Ironically, non-fills as a quality problem in injection molding injection molding
n.
A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold.
 and other molding operations is one of the most frequently occurring problems in production, but has the fewest references in the literature. Reducing the frequency of occurrence of this quality problem is usually related to better control of the uncured elastic and viscous quality of the rubber compound in question (ref. 140).

Porosity

Porosity, or bubbles forming in a rubber compound, is a common quality problem, which can be very expensive and cause the generation of much scrap. If a compound is cured under a sufficient pressure for a long enough time, many times porosity can be avoided (ref. 141). However, this is not always possible, so other steps must be taken to prevent porosity problems.

Determining where the "blow point" occurs during the curing process and establishing a proper cure time accordingly represent one way of minimizing porosity (ref. 142). Also, step-down cures in an autoclave autoclave

Vessel, usually of steel, able to withstand high temperatures and pressures. The chemical industry uses various types of autoclaves in manufacturing dyes and in other chemical reactions requiring high pressures.
 are another way to minimize porosity in the cured rubber product (ref. 143).

There is a window between under-mixing and over-mixing to minimize porosity formation for a given compound. All efforts should be exercised to minimize the presence of moisture and other volatiles in raw rubber(s) and compounding ingredients. Also, sufficient steps should be taken after mixing to eliminate moisture. Careful selection of extruder temperatures and prudent use of press bumping are important steps to consider, as well (ref. 144).

Shrinkage of cured parts

Controlling the degree of shrinkage of a rubber part after demolding can be critical in meeting customer specifications (ref. 145).

From a compounding perspective, using formulations that contain higher filler loadings will usually reduce the degree of compound shrinkage that occurs after cure (mold shrinkage) (refs. 146-149). Also, minimizing compounding ingredients with volatility is important (ref. 150). Even using devolatilized rubber can reduce shrinkage (ref. 151).

Backrinding

This is a common molding defect, caused by the expansion of the cured rubber on opening the mold, resulting in a rupture or tearing at the part line. This can be a very costly quality problem.

Some simple solutions are to cure the part at a lower temperature (ref. 152) for a longer time or cool the mold after the cure is complete in order to lower the internal pressure to prevent backrinding (ref. 153). However, either of these solutions would be very costly in production output.

A more drastic step is to change the mold design (refs. 154 and 155). However, this too can also be a costly correction.

Taking steps to preheat pre·heat  
tr.v. pre·heat·ed, pre·heat·ing, pre·heats
To heat (an oven, for example) beforehand.



pre·heater n.
 the preform pre·form  
tr.v. pre·formed, pre·form·ing, pre·forms
1. To shape or form beforehand.

2. To determine the shape or form of beforehand.

n.
1.
, or making compounding changes to increase the scorch safety time, or improving the compound's tear resistance can also help eliminate backrinding (refs. 156 and 157).

Conclusion

The review just presented touches on some of the major factory problems encountered by the rubber industry. This review has discussed, in general, some possible experimental ideas to consider in trying to solve these problems. By conducting Design of Experiments in the laboratory and later in the factory, as well, one can fine tune a possible solution to reduce or eliminate certain quality defects, while still testing to make sure you have not created another quality problem(s) somewhere else. One must keep in mind that any change made might possibly affect many other aspects of the process or product quality, for better or for worse. Therefore, all these aspects must be thoroughly investigated in order to make sure that no new quality problems are created.

References

(78.) J. Leblanc, "Factors affecting the extrudate swell and melt fracture phenomena of rubber compounds," Rubber Chemistry and Technology, vol. 54, p. 905, Nov.-Dec. 1981.

(79.) R. Kannabrian, "Application of flow behavior to design of rubber extrusion dies," Rubber Chemistry and Technology, vol. 59, p. 142, March-April 1986.

(80.) ibid ref. 68, Section 5. 7, "Extrusion: Reducing die swell."

(81.) ibid ref. 16.

(82.) F. Myers and W. Newell, "Use of power integrator and dynamic stress relaxometer to shorten mix cycles and establish scale-up criteria for internal mixer," Rubber Chemistry and Technology, vol., 51, p. 180, May-June 1978.

(83.) ibid ref. 16.

(84.) ibid ref. 16, p. 321.

(85.) P. Johnson, "Developments in extrusion science and technology," Rubber Chemistry and Technology, vol. 56, p. 575, July-Aug. 1983.

(86.) J. LeBlanc, "Factors affecting the extrudate swell and melt fracture phenomena of rubber compounds," Rubber Chemistry and Technology, vol. 54, p. 905, Nov.-Dec. 1981.

(87.) V. Folt, R.W. Smith and C.E. Wilkes, "Crystallization of cispolyisoprenes in a capillary capillary (kăp`əlĕr'ē), microscopic blood vessel, smallest unit of the circulatory system. Capillaries form a network of tiny tubes throughout the body, connecting arterioles (smallest arteries) and venules (smallest veins).  rheometer rhe·om·e·ter
n.
An instrument for measuring the flow of viscous liquids, such as blood.
," Rubber Chemistry and Technology, vol. 44, p. 1, March 1971.

(88.) J. Stevenson and J. Dick, Rubber Extrusion Technology Short Course, Section VI.C. 7 and III.B. 7, University of Wisconsin at Milwaukee, Feb. 12-14, 2003.

(89.) G. Colbert, "Time uniformity of extrudate melt temperature," Rubber World, vol. 202, p. 27, July 1990.

(90.) F. Eckenberg and G. Folie folie /fo·lie/ (fo-le´) [Fr.] psychosis; insanity.

folie à deux  (ah-ddbobr´ 
, "Continuous production of rubber profiles--state of extrusion line technology," paper no. 43, Rubber Division, ACS (Asynchronous Communications Server) See network access server. , October 17-19, 1995.

(91.) K.C. Shin and J.L. White, "Basic studies of extrusion of rubber compounds in a pin barrel extruder," Rubber Chemistry and Technology, vol. 66, p. 121, March-April 1993.

(92.) ibid ref. 16.

(93.) C. Stone, Chapter 14, "Ester plasticizers plasticizers

mostly triaryl phosphates, such as tricresyl, triphenyl phosphates, which are poisonous. See also triorthocresyl phosphate.
 and processing additives," Rubber Technology, Compounding and Testing for Performance, edited by J. Dick, Hanser Publishers', 2001, pp. 375-376.

(94.) S. Brignac and H. Young, "EPDM EPDM Ethylene-Propylene-Diene-Monomer
EPDM Enterprise Product Data Management
EPDM Ethylene Propylene Dimonomer (industrial/commercial piping/plumbing components)
EPDM Engineering Product Data Management
 with better low-temperature performance," Rubber & Plastics News, August 11, 1997, p. 14.

(95.) S.D. Brignac and C. Smith, "New ultra-low viscosity EPDM," Rubber World, vol. 215-1, p. 49, Oct. 1996. 96. ibid ref. 44.

(97.) ibid ref. 78.

(98.) G. Colbert, "Time uniformity of extrudate melt temperature," Rubber World, vol. 202-4, p.27, July 1990.

(99.) ibid ref. 88, Section II.A.4.

(100.) J.F. Stevenson, "Die design for rubber extrusion," Rubber World, vol. 228, p. 23, May 2003.

(101.) ibid ref. 88, Section VI.B.1 and VI.B.6.

(102.) Paul Meyer
This article is about Paul Meyer the French philologist, and not Paul Meyer the clarinetist.


Marie-Paul-Hyacinthe Meyer (January 17, 1840 - September 7, 1917), was a French philologist.
, "Practical applications of the short, adjustable MCT See Microsoft certification.  cold-feed mixer-extruder," Rubber World, vol. 202-4, p. 23, July 1990.

(103.) ibid ref. 16, pp. 308-321.

(104.) ibid ref. 93.

(105.) S. Botros, F. El-Mohsen and E. Meinecke, "Effect of brown vulcanized vegetable oil on ozone resistance, aging and flow properties of rubber compounds," Rubber Chemistry and Technology, vol. 60-1, p.159, March-April, 1987.

(106.) W. Waddell and L. Evans, "Precipitated silica and non-black fillers," Rubber Technology, Compounding and Testing for Performance, edited by J. Dick, Hanser Publishers, 2001, p. 328.

(107.) "A comparative evaluation of Hycar nitrile nitrile: see rubber.  polymers," Manual HM-1 Revised, B.F. Goodrich Chemical Co.

(108.) ibid ref. 68, Section 5.8.

(109.) Bill Klingensmith, "Recycling, production and use of reprocessed rubbers," Rubber World, vol. 203-6, p. 16, March 1991.

(110.) S. Schaa and A. Coran, "The rheology and processability of tire compounds," Rubber Chemistry and Technology, vol. 73, p. 225, May-June 2000.

(111.) L.A. Utracki, "The shear and elongation elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the planet as measured from the earth.  flow of polymer melts containing anisometric filler particles, part 1,"Rubber Chemistry. and Technology, vol. 57, p. 507, July-August 1984.

(112.) J.S. Dick, "Comparison of shear thinning behavior using capillary and rotorless shear rheometry," Rubber World, vol. 225-4, p. 23, January 2002.

(113.) D. Parikh, M. Hughes, M. Laughner, L. Meiske and R. Vara, "Next generation of ethylene ethylene (ĕth`əlēn') or ethene (ĕth`ēn), H2C=CH2, a gaseous unsaturated hydrocarbon. It is the simplest alkene.  elastomers," presented at Rubber Division, ACS, meeting, Fall, 2000.

(114.) J. Dick and H. Pawlowski, "Application of the rubber process analyzer in characterizing the effects of silica on uncured and cured compound properties," ITEC ITEC Instituto de Tecnologia em Informática e Informação do Estado de Alagoas
ITEC International Therapy Examination Council (UK)
ITEC Internet Technology
ITEC Institute for Tropical Ecology and Conservation
ITEC Instructional Technologies
 '96 Select (by Rubber and Plastics News), September 1997.

(115.) Don Bauman, "'Improving calendering operations," Rubber World, vol. 200-4, p. 23, July 1989.

(116.) A. Kasner and E. Meinecke, "Porosity in rubber: A review," Rubber Chemistry and Technology, vol. 69, p. 424, July-Aug. 1996.

(117.) ibid ref. 64, Processing Problem No. 6.

(118.) T. Dobel, Chapter 8, "Specialty elastomers," Rubber Technology, Compounding and Testing for Performance, edited by J. Dick, Hanser Publishers, 2001, p. 224.

(119.) M. Chase, "'Roll coverings past, present and future," presented at Rubber Roller Group meeting, New Orleans New Orleans (ôr`lēənz –lənz, ôrlēnz`), city (2006 pop. 187,525), coextensive with Orleans parish, SE La., between the Mississippi River and Lake Pontchartrain, 107 mi (172 km) by water from the river mouth; founded , May 15-17, 1996, p. 8.

(120.) ibid ref. 80.

(121.) ibid ref. 80.

(122.) ibid ref. 50.

(123.) J. Sommer Sommer is a surname, from the German and Danish word for the season "summer".

It may refer to:
  • Alfred Sommer (ophthalmologist) (born 1943), American academic
  • António de Sommer Champalimaud
  • Barbara Sommer (born 1948), German politician (CDU)
, Elastomer Molding Technology, Elastech, Hudson, OH, 2003, p. 282.

(124.) Hans-Herwig Bertram, "Mold release agents in the rubber industry," Rubber Chemistry and Technology, vol. 36, p. 1,148, Oct.-Nov. 1963.

(125.) D. McCarthy, D. Moon, S. Lytle and M. Dyer, "Understanding water-based mold releasants," Rubber World, vol. 213-2, p. 19, Nov. 1995.

(126.) J.C. Bament, "A guide to grades, compounding and processing Neoprene neoprene: see rubber.
neoprene

Any of a class of elastomers (rubberlike synthetic organic compounds of high molecular weight) made by polymerization of the monomer 2-chloro-1,3-butadiene and vulcanized (cross-linked, like rubber), by sulfur,
 synthetic rubber synthetic rubber: see rubber. ," Du Pont Du Pont (dpŏnt), family notable in U.S. industrial history. The Du Pont family's importance began when Eleuthère Irénée Du Pont established a gunpowder mill on the , p. 24.

(127.) D.L. Martin and S.J. Hillman Hillman was a famous British automobile marque, manufactured by the Rootes Group. It was based in Ryton-on-Dunsmore, near Coventry, England, from 1907 to 1976. Before 1907 the company had built bicycles. , "Troubleshooting problems with mold releases," Rubber World, vol. 208-5, p. 32, August 1993.

(128.) ibid ref. 123, p. 276.

(129.) P. Manley and C. Smith, Chapter 8, "Specialty elastomers," Rubber Technology, Compounding and Testing for Performance, edited by J. Dick, Hanser Publishers, 2001, p. 206.

(130.) Ben van Baarle, "Mold fouling during rubber vulcanization vulcanization (vŭl'kənəzā`shən), treatment of rubber to give it certain qualities, e.g., strength, elasticity, and resistance to solvents, and to render it impervious to moderate heat and cold. ," Rubber World, vol. 225-3, p. 34, December 2001.

(131.) F.C. Young, "Removing fouling residue from molds in-the-press with solid C[O.sub.2] pellet blasting," Rubber World, vol. 227-3, p. 39. December 2002.

(132.) ibid ref. 123, p. 270.

(133.) ibid ref. 123, p. 271. (134.) ibid ref. 123, p. 282.

(135.) ibid ref. 123, pp. 271-272.

(136.) ibid ref. 123, pp. 271-274.

(137.) ibid ref. 16, p. 311.

(138.) S. Bussolari and S. Laube, "A new Cabot carbon black for improved performance in peroxide cured injection molded compounds," paper no. 98 presented at Rubber Division, ACS, Meeting, Fall 2000.

(139.) ibid ref. 123, pp. 280-282.

(140.) ibid ref. 6.

(141.) J.R. Halladay, Chapter 8, "Specialty elastomers," Rubber Technology, Compounding and Testing for Performance, edited by J. Dick, Hanser Publishers, 2001, p. 237.

(142.) ibid ref. 116.

(143.) ibid ref. 68, Section 5.1.

(144.) ibid ref. 116.

(145.) William Andrew, Handbook of molded part shrinkage and warpage, Plastics Design Library, Norwich, NY, 2003.

(146.) J.R. Beatty, "Effect of composition on shrinkage of mold cured elastomeric compounds," Rubber Chemistry and Technology, vol. 51, p. 1,044, Nov.-Dec. 1978.

(147.) ibid ref. 107.

(148.) ibid ref. 68, Sect. 5.17.

(149.) "Treated wollastonites," <www.rtvanderbilt.com>.

(150.) ibid ref. 146.

(151.) ibid ref. 116.

(152.) ibid ref. 123, p. 280, p. 15.

(153.) R.M. Murray and D.C. Thompson, The Neoprenes, DuPont Inc., 1963, p.15.

(154.) ibid ref. 153.

(155.) ibid ref. 123, p. 280, p. 80.

(156.) ibid ref. 153.

(157.) ibid ref. 123, p. 280, pp. 81-90.

by John S. Dick

Alpha Technologies
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Author:Dick, John S.
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