CA1092765A - Silicone rubber enclosure element and method of using - Google Patents
Silicone rubber enclosure element and method of usingInfo
- Publication number
- CA1092765A CA1092765A CA268,283A CA268283A CA1092765A CA 1092765 A CA1092765 A CA 1092765A CA 268283 A CA268283 A CA 268283A CA 1092765 A CA1092765 A CA 1092765A
- Authority
- CA
- Canada
- Prior art keywords
- silicone rubber
- enclosure element
- fluorocarbon
- enclosure
- trichlorotrifluoroethane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/02—Chemical treatment or coating of shaped articles made of macromolecular substances with solvents, e.g. swelling agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C61/00—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor
- B29C61/003—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor characterised by the choice of material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C63/00—Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2083/00—Use of polymers having silicon, with or without sulfur, nitrogen, oxygen, or carbon only, in the main chain, as moulding material
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2383/04—Polysiloxanes
Abstract
TITLE: SILICONE RUBBER ENCLOSURE ELEMENT AND METHOD OF USING
ABSTRACT OF THE DISCLOSURE
A silicone rubber enclosure element and method of using in which the enclosure element, such as a length of tubing formed of silicone rubber, such as methyl vinyl polysiloxane and/or trifluoropropylmethyl vinyl polysiloxane, is treated with a fluorocarbon, such as trichlorotrifluoroethane, to effect expanding the inner diameter of the enclosure element about 50%.
After the enclosure element is mounted about a supporting structure while in the expanded form, the fluorocarbon is allowed to evaporate at room temperature and cause the silicone element to shrink about the supporting structure, forming a secure connection, as the element returns to substantially its original dimensions.
ABSTRACT OF THE DISCLOSURE
A silicone rubber enclosure element and method of using in which the enclosure element, such as a length of tubing formed of silicone rubber, such as methyl vinyl polysiloxane and/or trifluoropropylmethyl vinyl polysiloxane, is treated with a fluorocarbon, such as trichlorotrifluoroethane, to effect expanding the inner diameter of the enclosure element about 50%.
After the enclosure element is mounted about a supporting structure while in the expanded form, the fluorocarbon is allowed to evaporate at room temperature and cause the silicone element to shrink about the supporting structure, forming a secure connection, as the element returns to substantially its original dimensions.
Description
109;~765 S P E C I F I C A T I O N
This application relates generally to ways and means of connecting an elastomeric article with a supporting surface and more particularly to a silicone rubber article and method of securing a silicone rubber article, such as a length of tubing, to a supporting surface by first contacting the silicone rubber article with an improved expanding agent which effects expansion and thereafter causing shrinking of the article to substantially its original dimensions without adversely affect-ing the desirable properties of the silicone rubber.
Silicone rubber tubing and other shaped articlesformed of a silicone rubber composition are widely used in thermal and electrical insulation systems and are particularly useful, because of their outstanding chemical and physical properties. In many applications it is desirable to have the silicone rubber article fit securely over and connect the ad-jacent ends of two tubular members. Commonly, this is achieved through the use of heat shrink technology after the tubular article is mechanically expanded to an oversized shape. In this oversized shape the article can be placed over the end of a tubular member or over the end of any like supporting -~
structure, and, thereafter the silicone article is shrunk by heat treatment to substantially its original unexpanded dimen-sions. In so doing, the article will tend to conform securely to and form a sealing engagement with the supporting structure.
Heretofore, methods have been devised for using various swelling agents to effect dilating or swelling tubes or rings formed of an elastomeric material, such as polyvinyl chloride elastomers. The expansion and contraction of the prior art elastomeric materials have been effected by the swelling agents being absorbed into the elastomeric material and extracting at .. .... .
109~765 least a portion of one or more of the organic components, such as a plasticizer, contained in the elastomeric material.
When it is desirable that the elastomeric article be highly resistant to heat, howeYer, the inclusion of a plasticizer or other extractable organic material in the elastomer is undesirable, because the residual organic material causes a significant reduction in the heat resistance of the elastomeric article.
It is therefore an object of the present in~ention to pro~ide an improYed method of securing an enclosure element formed of a silicone rubber about a supporting structure which aYoids mechanically stressing and heating the silicone rubber ele~ents to e~fect expansion and contraction of the silicone ,~
rubber element. The applicant's inYenti~e method aYoids haYing an extractable organic compound present in the silicone rubber ele~entt and proYîdes a secure connection between the silicone rub~er element and the supporting structure more rapidly and safely than methods heretofore deyised. The -present inYention further proYides a silicone rubber element, such as silicone r~her tuhing, in a form suitable for immediately fitting about a supporting structure without requiring supplemental stressing or heating equipment for expanding or shrinking the silicone element.
In one aspect, the inYention pertains to a method of securing a silicone rubber enclosure element about a supportin~ structure which includes enclosing within a sealable conta~ner an enclosure element formed essentially of silicone 109;~765 rubber having an inner dimension which is normally smaller than an outer dimension of the supportive structure and a quantity of a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure which is suffic-ient to impregnate the element throughout and maintain the container filled with excess fluorocarbon chemical to effect expansion of the inner dimension of the enclosure element in excess of the outer dimension of the supportive structure and maintain the element in expanded form while sealably enclosed within the container. The element is removed from the container in the vicinity of the supportive structure and mounted while in the expanded form over the outer dimension -`
of the supportive structure. Thereafter the fluorocarbon i8 allowed to evaporate from the element at ambient temperature and pressure to effect shrinking thereof and form a secure engagement about the supportive structure.
The invention also comprehends a silicone rubber enclosure element adapted to form a water proof connection between electrical conductors and between pipes comprising a tubular section formed essentially of silicone rubber which is impregnated throughout with a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure. The inner dimension of the tubular section is expanded in excess of the normal unexpanded dimension thereof while impregnated and the tubular section returns to its normal unexpanded dimension when the fluorocarbon chemical evaporates on exposure of the element to ambient temperature and pressure and forming the water proof connection.
Other aspects of the present invention will be apparent ~0~;~7tjS
to those skilled in the art from the following detailed descrip-tion and accompanying claims.
It has been found that an enclosure element formed of silicone rubber can be effectively expanded and shrunk so as to achieve the objects of the present invention by a method which comprises treating a silicone rubber article in the form of a tJbing or like shaped article with an expanding agent comprised essentially of a fluorocarbon compound and, after mounting the expanded silicone rubber article about a supporting structure the outer dimensions of which are slightly larger than the original inner dimension of the unexpanded silicone rubber article, allowing the fluorocarbon compound to separate from the silicone rubber article at ambient temperature and pressure so that the expanded silicone rubber article returns to substan-tially its original dimensions and forms a secure engagement with the supporting structure.
The silicones or organo siloxane elastomeric materials which can be used in the present invention are based on a silicon~oxygen structure to which various organic radicals are attached, and the three fundamental types of organosiloxanes (oils, rubber, and resins) may be considered as being built from three unit structures which have been called M, D, and T
units as follows:
R R R
l l t R- Si- O - - Si- O - - O -Si- O -R R R
M unit D unit T unit As will be evident, the M unit is monofunctional, the D unit is difunctional and the T unit is trifunctional. In the formation of silicone or organosiloxane polymers, the M units can be used 1(39;~765 only for dimers or as end units or chain stoppers. Linear polymers can be produced from the D units with M units as the terminating groups. Cross-linked polymers can be produced from the T units. Therefore, the three general types of organo-siloxane materials referred to above can be considered as having the following arrangement of M, D and T units:
Silicone oils: M(D)XM, where x is a small number Silicone rubber: M(D)XM, where x is a very large number Silicone resins: UDT combinations.
These silicone molecules are tailored to achieve specific properties. For example, the R group in a dimethyl poly-siloxane polymer can be replaced or substituted with phenyl and/or vinyl or trifluoropropyl groups to achieve significant variations in properties. Silicone rubber compositions which are suitable for use in the present invention include but are not limited to methyl vinyl polysiloxane, phenyl vinyl methyl polysiloxane, and trifluoropropylmethyl vinyl polysiloxane.
The polysiloxane rubber compositions can be combined to provide special properties to the enclosure element.
The silicone elastomeric rubber material can be provided in the form of a tube, ring or other enclosed form and can be extruded in such forms by conventional apparatus and procedures.
The silicone rubber elastomers can have but are not required to have minor amounts of other conventional additives admixed therewith, such as inert fillers, coloring agents, or vulcanizing agents.
The outstanding properties which distinguish the silicone rubber materials from other elastomers is their great resistance to extremely high and low temperatures. Thus, a silicone rubber element can be exposed to temperatures up to 200C for
This application relates generally to ways and means of connecting an elastomeric article with a supporting surface and more particularly to a silicone rubber article and method of securing a silicone rubber article, such as a length of tubing, to a supporting surface by first contacting the silicone rubber article with an improved expanding agent which effects expansion and thereafter causing shrinking of the article to substantially its original dimensions without adversely affect-ing the desirable properties of the silicone rubber.
Silicone rubber tubing and other shaped articlesformed of a silicone rubber composition are widely used in thermal and electrical insulation systems and are particularly useful, because of their outstanding chemical and physical properties. In many applications it is desirable to have the silicone rubber article fit securely over and connect the ad-jacent ends of two tubular members. Commonly, this is achieved through the use of heat shrink technology after the tubular article is mechanically expanded to an oversized shape. In this oversized shape the article can be placed over the end of a tubular member or over the end of any like supporting -~
structure, and, thereafter the silicone article is shrunk by heat treatment to substantially its original unexpanded dimen-sions. In so doing, the article will tend to conform securely to and form a sealing engagement with the supporting structure.
Heretofore, methods have been devised for using various swelling agents to effect dilating or swelling tubes or rings formed of an elastomeric material, such as polyvinyl chloride elastomers. The expansion and contraction of the prior art elastomeric materials have been effected by the swelling agents being absorbed into the elastomeric material and extracting at .. .... .
109~765 least a portion of one or more of the organic components, such as a plasticizer, contained in the elastomeric material.
When it is desirable that the elastomeric article be highly resistant to heat, howeYer, the inclusion of a plasticizer or other extractable organic material in the elastomer is undesirable, because the residual organic material causes a significant reduction in the heat resistance of the elastomeric article.
It is therefore an object of the present in~ention to pro~ide an improYed method of securing an enclosure element formed of a silicone rubber about a supporting structure which aYoids mechanically stressing and heating the silicone rubber ele~ents to e~fect expansion and contraction of the silicone ,~
rubber element. The applicant's inYenti~e method aYoids haYing an extractable organic compound present in the silicone rubber ele~entt and proYîdes a secure connection between the silicone rub~er element and the supporting structure more rapidly and safely than methods heretofore deyised. The -present inYention further proYides a silicone rubber element, such as silicone r~her tuhing, in a form suitable for immediately fitting about a supporting structure without requiring supplemental stressing or heating equipment for expanding or shrinking the silicone element.
In one aspect, the inYention pertains to a method of securing a silicone rubber enclosure element about a supportin~ structure which includes enclosing within a sealable conta~ner an enclosure element formed essentially of silicone 109;~765 rubber having an inner dimension which is normally smaller than an outer dimension of the supportive structure and a quantity of a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure which is suffic-ient to impregnate the element throughout and maintain the container filled with excess fluorocarbon chemical to effect expansion of the inner dimension of the enclosure element in excess of the outer dimension of the supportive structure and maintain the element in expanded form while sealably enclosed within the container. The element is removed from the container in the vicinity of the supportive structure and mounted while in the expanded form over the outer dimension -`
of the supportive structure. Thereafter the fluorocarbon i8 allowed to evaporate from the element at ambient temperature and pressure to effect shrinking thereof and form a secure engagement about the supportive structure.
The invention also comprehends a silicone rubber enclosure element adapted to form a water proof connection between electrical conductors and between pipes comprising a tubular section formed essentially of silicone rubber which is impregnated throughout with a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure. The inner dimension of the tubular section is expanded in excess of the normal unexpanded dimension thereof while impregnated and the tubular section returns to its normal unexpanded dimension when the fluorocarbon chemical evaporates on exposure of the element to ambient temperature and pressure and forming the water proof connection.
Other aspects of the present invention will be apparent ~0~;~7tjS
to those skilled in the art from the following detailed descrip-tion and accompanying claims.
It has been found that an enclosure element formed of silicone rubber can be effectively expanded and shrunk so as to achieve the objects of the present invention by a method which comprises treating a silicone rubber article in the form of a tJbing or like shaped article with an expanding agent comprised essentially of a fluorocarbon compound and, after mounting the expanded silicone rubber article about a supporting structure the outer dimensions of which are slightly larger than the original inner dimension of the unexpanded silicone rubber article, allowing the fluorocarbon compound to separate from the silicone rubber article at ambient temperature and pressure so that the expanded silicone rubber article returns to substan-tially its original dimensions and forms a secure engagement with the supporting structure.
The silicones or organo siloxane elastomeric materials which can be used in the present invention are based on a silicon~oxygen structure to which various organic radicals are attached, and the three fundamental types of organosiloxanes (oils, rubber, and resins) may be considered as being built from three unit structures which have been called M, D, and T
units as follows:
R R R
l l t R- Si- O - - Si- O - - O -Si- O -R R R
M unit D unit T unit As will be evident, the M unit is monofunctional, the D unit is difunctional and the T unit is trifunctional. In the formation of silicone or organosiloxane polymers, the M units can be used 1(39;~765 only for dimers or as end units or chain stoppers. Linear polymers can be produced from the D units with M units as the terminating groups. Cross-linked polymers can be produced from the T units. Therefore, the three general types of organo-siloxane materials referred to above can be considered as having the following arrangement of M, D and T units:
Silicone oils: M(D)XM, where x is a small number Silicone rubber: M(D)XM, where x is a very large number Silicone resins: UDT combinations.
These silicone molecules are tailored to achieve specific properties. For example, the R group in a dimethyl poly-siloxane polymer can be replaced or substituted with phenyl and/or vinyl or trifluoropropyl groups to achieve significant variations in properties. Silicone rubber compositions which are suitable for use in the present invention include but are not limited to methyl vinyl polysiloxane, phenyl vinyl methyl polysiloxane, and trifluoropropylmethyl vinyl polysiloxane.
The polysiloxane rubber compositions can be combined to provide special properties to the enclosure element.
The silicone elastomeric rubber material can be provided in the form of a tube, ring or other enclosed form and can be extruded in such forms by conventional apparatus and procedures.
The silicone rubber elastomers can have but are not required to have minor amounts of other conventional additives admixed therewith, such as inert fillers, coloring agents, or vulcanizing agents.
The outstanding properties which distinguish the silicone rubber materials from other elastomers is their great resistance to extremely high and low temperatures. Thus, a silicone rubber element can be exposed to temperatures up to 200C for
2 to 5 years without losing its resilience and dielectric , strength. The silicone rubber elastomers also exhibit excellent resistance to both ozone and corona. The volume resistivity ranges between 10 to 14 to 10 to 16 ohm - cm and the dielectric strength ranging between 400 - 700 volts/mil. When ignited, the silicones do not form objectionable acids, such as HCl, HCN, or SO2 .
While silicone rubber compositions are generally resistant to solvents~ such as alcohol and acetone and to many chlorinated hydrocarbons, it has been discovered that very signi-ficant expansion and contraction of a silicone rubber articlecan be effected when the silicone rubber article formed of a silicone rubber, such as methyl vinyl polysiloxane rubber, tri-fluoropropylmethyl vinyl polysiloxane rubber or both, is treated with a fluorocarbon compound, such as trichlorotrifluoroethane, without requiring the presence of an organic plasticizer and without loss of any of the desirable characteristics of the silicone rubber, such as prolonged stability at elevation tem-peratures up to 260C and at temperatures as low as -100C, non-flammability, high degree of electrical stability, and good resistance to dielectric fatigue.
The expanding or swelling agent used for treating the silicone rubber element is selected from the group of fluoro-carbon chemicals ~commonly sold under the trade name FREON, a trademark of the E. I. duPont de Nemours Company but not limited to the fluorocarbons sold by duPont). The fluorocarbon chemical used in the present invention is preferably liquid at the tem-peratures normally encountered when using the silicone rubber elements but should not have a high boiling point, since the compound should have a high rate of vaporization characterized by a relatively high vapor pressure and a low heat of vaporiza-tion. In addition the fluorocarbon chemical should be radially - . .......................... ~
;. . :, ~ : .:
109~7~;5 absorbed by the si~cone rubber material. The fluorocarbon chemical, trichlorotrifluoroethane, satisfies all of the fore-going physical and chemical requirements and, in addition has the desirable characteristics of exhibiting low toxicity with an OSHA threshold limit of 1000 p.p.m., has excellent resistance to both ozone and corona and is non-flammable. Trichlorotri-fluoroethane is chemically non-reactive with most other materials and does not present a disposal problem. Among the group of fluorocarbons suitable for use in the present invention but are not limited thereto are trichloromonofluoromethane, tri-chlorotrifluoroethane and trichlorodifluoroethane~
In practicing the present invention a silicone rubber enclosure element, such as a length of tubing, is preferably treated with the fluorocarbon dilating agent by immersing the silicone rubber enclosure element in a liquid fluorocarbon for a period sufficient to cause the silicone rubber enclosure ele-ment to expand approximately 50% in excess of its original inner diameter when the element is in the form of a ring or tube. The maximum swelling of the silicone rubber enclosure element when treated with the fluorocarbon liquid is essentially complete in 2-4 hours. It is preferable to pretreat the silicone rubber enclosure element by sealably enclosing the element in a container along with sufficient fluorocarbon liquid to effect maximum expansion of the silicone rubber element and provide a slight excess of 1uorocarbon vapor within the container so that the silicone rubber element will remain in the expanded form until the container is opened. The expanded silicone rubber element can be kept in the sealed container for an in-definite period. When opened, the silicone rubber element is ready for immediate use and, after mounting the expanded silicone rubber element about a supporting structure having an outer .: - . '; .
.
7~i5 diameter slightly larger than the original inner diameter of the silicone rubber element, the silicone rubber element begins to shrink as the fluorocarbon chemical evaporates, forming a secure frictional engagement about the supporting structure when the silicone rubber element shrinks to its original dimensions.
The method of expanding and retracting a silicone rubber enclosure element, such as a ring or tubing, has numerous applications and is particularly adapted for forming waterproof connections between electrical conductors or pipes, in the space and aircraft industry, and in the automotive industry.
In one useful embodiment of the present invention a tube formed of methyl vinyl polysiloxane rubber sold under the trademark "9ilastic", Medical Grade Elastic Tubing by Dow Corning and having as original dimensions an inner diameter (I.D.) of 0.435 inches, a wall thickness of 0.037 inches and a length of 3 inches was impregnated throughout by treating with 3.25 ml.
of trichlorotrifluoroethane in a sealed oontainer. After 24 hours the inside diameter of the tubing increased to 0.600 inches, and the length to 3.875 inches. On opening the sealed container and exposing the dilated tubing to atmospheric pressure for 105 minutes at 21C (70F), the tubing recovered substantially to the original dimensions (actual recovered dimensions were 0.436 inches I.D., 3 inches length, 0.034 inches wall thickness).
In a preferred embodiment of the present invention, slabs formed o~ methyl vinyl polysiloxane rubber sold under the trademark "Electrisil SE9095A-03" by General Electric and having cut ring dimensions of 1.0" outside diameter and 0.8" inside diameter with a thickness of 0.085" was impregnated throughout by treating with an excess of trichlorotrifluoroethane in a sealed container. After 24 hours the ring increased to 1.3"
outside diameter, 1.05" inside diameter, and 0.115" thickness.
lO9Z765 On opening the sealed container and exposing the dilated rings to atmospheric pressure for 105 minutes at 21C(70F), the rings recovered to its approximate original dimensions (the actual recovered dimensions were 1.0" outside diameter, 0.8"
inside diameter, and 0.085" thickness).
In another embodiment of the present invention, a trifluoropropyl methyl vinyl polysiloxane rubber strip having a length of 2. a~ and width of 0.44" was impregnated throughout by treating with an excess of trichlorotrifluoroethane in a lQ sealed container. After 24 hours the length of material increased to 2.25" and the width to 0.5". On opening the sealed container and exposing the dilated strips to atmospheric pressure for 105 minutes at 21C(70F), the strip recovered to its approximate original dimensions (the actual recovered dimensions were 2.0"
long and 0.44" wide).
Similar results are obtained with other grades of methyl vinyl polysiloxane rubber materials and fluorocarbon expanding agents.
_g_ , . . . : , .-. . , ~ . . . - ~ . .
While silicone rubber compositions are generally resistant to solvents~ such as alcohol and acetone and to many chlorinated hydrocarbons, it has been discovered that very signi-ficant expansion and contraction of a silicone rubber articlecan be effected when the silicone rubber article formed of a silicone rubber, such as methyl vinyl polysiloxane rubber, tri-fluoropropylmethyl vinyl polysiloxane rubber or both, is treated with a fluorocarbon compound, such as trichlorotrifluoroethane, without requiring the presence of an organic plasticizer and without loss of any of the desirable characteristics of the silicone rubber, such as prolonged stability at elevation tem-peratures up to 260C and at temperatures as low as -100C, non-flammability, high degree of electrical stability, and good resistance to dielectric fatigue.
The expanding or swelling agent used for treating the silicone rubber element is selected from the group of fluoro-carbon chemicals ~commonly sold under the trade name FREON, a trademark of the E. I. duPont de Nemours Company but not limited to the fluorocarbons sold by duPont). The fluorocarbon chemical used in the present invention is preferably liquid at the tem-peratures normally encountered when using the silicone rubber elements but should not have a high boiling point, since the compound should have a high rate of vaporization characterized by a relatively high vapor pressure and a low heat of vaporiza-tion. In addition the fluorocarbon chemical should be radially - . .......................... ~
;. . :, ~ : .:
109~7~;5 absorbed by the si~cone rubber material. The fluorocarbon chemical, trichlorotrifluoroethane, satisfies all of the fore-going physical and chemical requirements and, in addition has the desirable characteristics of exhibiting low toxicity with an OSHA threshold limit of 1000 p.p.m., has excellent resistance to both ozone and corona and is non-flammable. Trichlorotri-fluoroethane is chemically non-reactive with most other materials and does not present a disposal problem. Among the group of fluorocarbons suitable for use in the present invention but are not limited thereto are trichloromonofluoromethane, tri-chlorotrifluoroethane and trichlorodifluoroethane~
In practicing the present invention a silicone rubber enclosure element, such as a length of tubing, is preferably treated with the fluorocarbon dilating agent by immersing the silicone rubber enclosure element in a liquid fluorocarbon for a period sufficient to cause the silicone rubber enclosure ele-ment to expand approximately 50% in excess of its original inner diameter when the element is in the form of a ring or tube. The maximum swelling of the silicone rubber enclosure element when treated with the fluorocarbon liquid is essentially complete in 2-4 hours. It is preferable to pretreat the silicone rubber enclosure element by sealably enclosing the element in a container along with sufficient fluorocarbon liquid to effect maximum expansion of the silicone rubber element and provide a slight excess of 1uorocarbon vapor within the container so that the silicone rubber element will remain in the expanded form until the container is opened. The expanded silicone rubber element can be kept in the sealed container for an in-definite period. When opened, the silicone rubber element is ready for immediate use and, after mounting the expanded silicone rubber element about a supporting structure having an outer .: - . '; .
.
7~i5 diameter slightly larger than the original inner diameter of the silicone rubber element, the silicone rubber element begins to shrink as the fluorocarbon chemical evaporates, forming a secure frictional engagement about the supporting structure when the silicone rubber element shrinks to its original dimensions.
The method of expanding and retracting a silicone rubber enclosure element, such as a ring or tubing, has numerous applications and is particularly adapted for forming waterproof connections between electrical conductors or pipes, in the space and aircraft industry, and in the automotive industry.
In one useful embodiment of the present invention a tube formed of methyl vinyl polysiloxane rubber sold under the trademark "9ilastic", Medical Grade Elastic Tubing by Dow Corning and having as original dimensions an inner diameter (I.D.) of 0.435 inches, a wall thickness of 0.037 inches and a length of 3 inches was impregnated throughout by treating with 3.25 ml.
of trichlorotrifluoroethane in a sealed oontainer. After 24 hours the inside diameter of the tubing increased to 0.600 inches, and the length to 3.875 inches. On opening the sealed container and exposing the dilated tubing to atmospheric pressure for 105 minutes at 21C (70F), the tubing recovered substantially to the original dimensions (actual recovered dimensions were 0.436 inches I.D., 3 inches length, 0.034 inches wall thickness).
In a preferred embodiment of the present invention, slabs formed o~ methyl vinyl polysiloxane rubber sold under the trademark "Electrisil SE9095A-03" by General Electric and having cut ring dimensions of 1.0" outside diameter and 0.8" inside diameter with a thickness of 0.085" was impregnated throughout by treating with an excess of trichlorotrifluoroethane in a sealed container. After 24 hours the ring increased to 1.3"
outside diameter, 1.05" inside diameter, and 0.115" thickness.
lO9Z765 On opening the sealed container and exposing the dilated rings to atmospheric pressure for 105 minutes at 21C(70F), the rings recovered to its approximate original dimensions (the actual recovered dimensions were 1.0" outside diameter, 0.8"
inside diameter, and 0.085" thickness).
In another embodiment of the present invention, a trifluoropropyl methyl vinyl polysiloxane rubber strip having a length of 2. a~ and width of 0.44" was impregnated throughout by treating with an excess of trichlorotrifluoroethane in a lQ sealed container. After 24 hours the length of material increased to 2.25" and the width to 0.5". On opening the sealed container and exposing the dilated strips to atmospheric pressure for 105 minutes at 21C(70F), the strip recovered to its approximate original dimensions (the actual recovered dimensions were 2.0"
long and 0.44" wide).
Similar results are obtained with other grades of methyl vinyl polysiloxane rubber materials and fluorocarbon expanding agents.
_g_ , . . . : , .-. . , ~ . . . - ~ . .
Claims (12)
1. A method of securing a silicone rubber enclosure element about a supporting structure which comprises;
enclosing within a sealable container an enclosure element formed essentially of silicone rubber having an inner dimension which is normally smaller than ah outer dimension of said supportive structure and a quantity of a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure which is sufficient to impregnate said element throughout and maintain said container filled with excess fluorocarbon chemical to effect expansion of said inner dimension of said enclosure element in excess of said outer dimension of said supportive structure and maint-ain said element in expanded form while sealably enclosed within said container, removing said element from said container in the vicinity of said supportive structure and mounting said element while in said expanded form over said outer dimension of the supportive structure, and thereafter allowing said fluorocarbon to evaporate from said element at ambient temperature and pressure to effect shrinking thereof and forming a secure engagement about said supportive structure.
enclosing within a sealable container an enclosure element formed essentially of silicone rubber having an inner dimension which is normally smaller than ah outer dimension of said supportive structure and a quantity of a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure which is sufficient to impregnate said element throughout and maintain said container filled with excess fluorocarbon chemical to effect expansion of said inner dimension of said enclosure element in excess of said outer dimension of said supportive structure and maint-ain said element in expanded form while sealably enclosed within said container, removing said element from said container in the vicinity of said supportive structure and mounting said element while in said expanded form over said outer dimension of the supportive structure, and thereafter allowing said fluorocarbon to evaporate from said element at ambient temperature and pressure to effect shrinking thereof and forming a secure engagement about said supportive structure.
2. A method according to Claim 1, wherein the silicone rubber is taken from the group consisting of methyl vinyl polysiloxane, phenyl vinyl methyl polysiloxane, trifluoro-propylmethyl vinyl polysiloxane, and combinations thereof.
3. A method according to Claim 1 or Claim 2, wherein the fluorocarbon chemical is taken from the group consisting of trichlorotrifluoroethane, tetrachlorodifluorothane, trichloromonofluoromethane, and combinations thereof.
4. A method according to Claim 1, wherein the silicone rubber comprises methyl vinyl polysiloxane and the fluorocarbon chemical is trichlorotrifluoroethane.
5. A method according to Claim 1 or Claim 2, wherein the fluorocarbon is trichlorotrifluoroethane.
6. A method according to Claim 1, Claim 2 or Claim 4, wherein the silicone rubber is essentially free of extractable organic compounds.
7. A silicone rubber enclosure element adapted to form a water proof connection between electrical conductors and between pipes comprising a tubular section formed essentially of silicone rubber which is impregnated throughout with a liquid fluorocarbon chemical having a high vapor pressure at ambient temperature and pressure;
whereby the inner dimension of said tubular section is expanded in excess of the normal unexpanded dimension thereof while impregnated and said tubular section returning to its normal unexpanded dimension when said fluorocarbon chemical evaporates on exposure of said element to ambient temperature and pressure and forming said water proof connection.
whereby the inner dimension of said tubular section is expanded in excess of the normal unexpanded dimension thereof while impregnated and said tubular section returning to its normal unexpanded dimension when said fluorocarbon chemical evaporates on exposure of said element to ambient temperature and pressure and forming said water proof connection.
8. A silicone rubber enclosure element according to Claim 7, wherein the silicone rubber is taken from the group consisting of methyl vinyl polysiloxane, phenyl vinyl methyl polysiloxane, trifluoropropylmethyl vinyl poly-siloxane, and combinations thereof.
9. A silicone rubber enclosure element according to Claim 7 or Claim 8, wherein the enclosure element is impregnated with a fluorocarbon chemical taken from the group consisting of trichlorotrifluoroethane, tetrachlorodifluoroethane, trichloromonofluoromethane, and combinations thereof.
10. A silicone rubber enclosure element according to Claim 7, wherein the enclosure element is formed of methyl vinyl polysiloxane and is impregnated with trichlorotri-fluoroethane.
11. A silicone rubber enclosure element according to Claim 7 or Claim 8, wherein the enclosure element is impregnated with trichlorotrifluoroethane.
12. A silicone rubber element according to Claim 7, Claim 8 or Claim 10, wherein the silicone rubber is essential-ly free of extractable organic compounds.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US74566476A | 1976-11-29 | 1976-11-29 | |
| US745,664 | 1976-11-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1092765A true CA1092765A (en) | 1981-01-06 |
Family
ID=24997704
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA268,283A Expired CA1092765A (en) | 1976-11-29 | 1976-12-20 | Silicone rubber enclosure element and method of using |
Country Status (6)
| Country | Link |
|---|---|
| JP (2) | JPS5369281A (en) |
| CA (1) | CA1092765A (en) |
| DE (1) | DE2704598A1 (en) |
| FR (1) | FR2372370A1 (en) |
| GB (1) | GB1562645A (en) |
| NL (1) | NL7614589A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6053058B2 (en) * | 1979-06-18 | 1985-11-22 | 信越化学工業株式会社 | Method for fixing a silicone rubber molded body to a support |
| FR2601522B1 (en) * | 1986-07-11 | 1990-05-11 | Bernier Raymond | MOLDED MEMBER FOR PROTECTING AND INSULATING ELECTRICAL CONDUCTORS AND METHOD FOR SETTING IT UP BY RETRACTION AT AMBIENT TEMPERATURE |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3262625A (en) * | 1963-04-12 | 1966-07-26 | Monsanto Co | Insulating surfaces |
| BE754618A (en) * | 1969-08-13 | 1971-02-10 | Cables De Lyon Geoffroy Delore | WELDING PROCESS, WITH THERMAL SHRINKABLE THERMAL SCREEN, FOR ELECTRIC CABLE SHEATH |
| CA960074A (en) * | 1971-08-11 | 1974-12-31 | David J. Lando | Method of improving adhesive properties of a surface comprising a cured epoxy |
| US4035534A (en) * | 1972-09-01 | 1977-07-12 | Raychem Corporation | Heat-shrinkable laminate |
| FR2315158A1 (en) * | 1975-06-16 | 1977-01-14 | Raychem Corp | SLEEVE, ITS MANUFACTURING PROCESS AND ITS APPLICATION TO COVERING A SUBSTRATE |
-
1976
- 1976-12-20 CA CA268,283A patent/CA1092765A/en not_active Expired
- 1976-12-30 NL NL7614589A patent/NL7614589A/en not_active Application Discontinuation
-
1977
- 1977-01-12 JP JP283077A patent/JPS5369281A/en active Granted
- 1977-02-04 DE DE19772704598 patent/DE2704598A1/en active Pending
- 1977-03-25 GB GB1278877A patent/GB1562645A/en not_active Expired
- 1977-06-14 FR FR7718182A patent/FR2372370A1/fr active Pending
-
1980
- 1980-10-31 JP JP15456480A patent/JPS5699650A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5369281A (en) | 1978-06-20 |
| FR2372370A1 (en) | 1978-06-23 |
| JPS5654218B2 (en) | 1981-12-24 |
| JPS5699650A (en) | 1981-08-11 |
| NL7614589A (en) | 1978-05-31 |
| DE2704598A1 (en) | 1978-06-01 |
| JPS5616743B2 (en) | 1981-04-17 |
| GB1562645A (en) | 1980-03-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |