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Elastomeric cyclic olefin copolymers.

Cyclic olefin copolymer (COC) is a relatively new commercial polymer. Four commercial sources of cyclic olefin resin are available under the Topas, Apel, Zeonor and Zeonex, and Arton brand names, supplied by Topas Advanced Polymers, Mitsui Chemicals, Zeon Chemical and Japan Synthetic Rubber, respectively. Topas COC is a random copolymer of ethylene and norbornene. Norbornene is synthesized via the Diels-Alder reaction of ethylene and cyclopentadiene. Polymerization of ethylene and norbornene using metallocene catalysts produces cyclic olefin copolymer. Bulky cyclic rings randomly distributed in an ethylenic backbone prevent crystallization of the ethylene units, creating an amorphous morphology.

Topas COC grades are distinguished by glass transition temperature and molecular weight. The glass transition temperature (Tg) depends on the mole percent of norbornene. The typical commercial Tg range is between 33[degrees]C and 170[degrees]C. COC has many key property attributes, including, but not limited to, exceptional moisture and aroma barrier, chemical resistance, transparency, purity, stiffness and strength (ref. 1).

Elastomeric cyclic olefin copolymer (E-140) is an expansion of the Topas COC product technology platform. E-140 is a largely amorphous polymer with low level crystallinity. E-140 is a random copolymer without hard or soft segments or dispersed rubber phase morphologies. Toughness and impact resistance combined with excellent barrier, transparency, low dielectric and high purity enables E-140 to compete favorably with existing elastomers.

Regulatory compliance

E-140 has high purity and enjoys broad regulatory compliance. E-140 complies with FDA Food Contact Notification (FCN) #1104 for many U.S. food contact applications. E-140 can be used in the manufacture of food contact articles that will be in contact with aqueous, acidic, low alcohol (up to 15%) and dry foods under conditions such as hot filled or pasteurized above 150[degrees]F (65[degrees]C) through frozen storage with no thermal treatment in the container.

Monomers and additives are listed in the EU Plastics Regulation 10/2011/EC (PIM-Plastic Implementation Measure). The product is listed in FDA Drug Master File #12132 and Device Master File #1043. It meets EU and U.S. Pharmacopeia for PE and PP. E-140 has passed USP Class VI and ISO 10993 protocols, including cytotoxicity studies. The product has been added to Health Canada's listing of acceptable polymers for use in food packaging applications. E-140 is not recommended or supported for use in implant applications.

E-140 is an extremely pure and simple polymer formulated and manufactured without controversial ingredients. E-140 does not use in its process or formulations plasticizers, including phthalates; RoHS substances; bisphenol A; CONEG heavy metals, including lead, cadmium, chromium VI and mercury; vinyl chloride monomer or polymer; halogens including chlorine and fluorine; fluorochemicals or fluoropolymers, including PFOA; flame retardants, including brominated compounds; California Proposition 65 substances; SARA 313 substances; ozone-depleting chemicals; and natural rubber or latex compounds.

Material properties (refs. 2-8)

In addition to its unmatched purity, E-140 offers many valuable features and benefits, namely oxygen and moisture barrier, good tensile properties, low specific gravity, excellent optical properties and low dielectric properties.

Barrier properties are clearly an advantageous feature of E-140. Specifically, oxygen and water vapor permeability are superior to many elastomers. Rigid cyclic olefin copolymers (COC) are not noted for their oxygen barrier property relative to widely used polyamide and ethylene vinyl alcohol. However, COC is better than polyolefins. As shown in table 1, oxygen permeability of linear low density polyethylene (Attane 4201) is 279 cc-mm/[m.sup.2] day atm measured at 23[degrees]C; 50% RH (ASTM D3985 and related protocols), about ten times higher than 24 cc-mm/[m.sup.2] day atm for COC (Topas 8007). E-140 is higher, 118 cc-mm/[m.sup.2] day atm. This value is similar to those of copolyester elastomers, 37 cc-mm/[m.sup.2] day atm (Riteflex 663) and 130 cc-mm/[m.sup.2] day atm (Ecdel 9966). Yet, E-140 has superior oxygen permeability relative to many other elastomers. Oxygen permeability of TPV (Santoprene 201-87), polybutadiene TPE (JSR RB830), SEBS (Kraton G-1652) and SIS (Kraton D-1101) is 434, 550, 1,095 and 1,717 cc-mm/[m.sup.2] day atm, respectively.

Rigid COC has noteworthy moisture vapor barrier, not matched by most thermoplastic materials. As shown in table 2, water vapor permeability of linear low density polyethylene (Attane 4201) is 0.5 g-mm/[m.sup.2] day measured at 38[degrees]C; 90% RH (ASTM F1249 and related protocols), about five times higher than 0.09 g-mm/[m.sup.2] day for COC (Topas 8007). Water vapor permeability of E-140, 0.4 g-mm/[m.sup.2] day, is not as low as COC. This value is similar to TPV (Santoprene 201 87), 0.2 g-mm/[m.sup.2] day. As with oxygen permeability, E-140 has superior moisture barrier relative to many elastomers. Water vapor permeability of polybutadiene TPE (JSR RB830), copolyester elastomer (Ecdel 9966), SIS (Kraton D-1101) and ether type TPU (Estane 58237) is 10, 19, 257 (23[degrees]C) and 550 g-mm/[m.sup.2] day, respectively.

E-140 has many useful mechanical properties summarized in table 3. As with many polyolefins, E-140 specific gravity is less than 1.0 g/cc. At 0.94 g/cc, E-140 is similar to the olefin based TPV (Santoprene 201-87), 0.96 g/cc; but much lower than 1.01 g/cc for SBS (Styrolux 684D) and 1.13 g/cc for copolyester elastomer (Ecdel 9966). Yield advantage can be significant for low density elastomers. Water absorption is very low, barely detectable for E-140, which is not a surprise given its low water permeability. Performance and dimensional stability of E-140 is expected to be unchanged in high humidity and water saturated environments. E-140 is very tough and durable. Total energy to failure, as measured by instrumented dart impact (ASTM D3763), for E-140 and SBS (Styrolux 684D) is 33 and 16 ft.-lb., respectively. E-140 is transparent. Total haze of 5-mil blown film is about 1.3%, similar to that of copolyester elastomer (Ecdel 9966) and SBS (Styrolux 684D). Low haze can be achieved in thicker, 2-3 mm, injection molded articles, but tool finish and quality influence results. Tensile properties of E-140, specifically tensile strength and elongation at break, are similar to TPV (Santoprene 201-87), SBS (Styrolux 684D) and copolyester elastomer (Ecdel 9966). However, like most elastomers, these properties are strain rate dependent. Tensile strength at break and hardness map show the tensile strength and durometer A and D hardness relationship for generic elastomeric type, including TPU, TPV, TPO and TPS. Ultimate tensile strength of E-140 is rate dependent. At slower 50 mm/minute strain rate, tensile strength about doubles due to strain hardening. At 500 mm/minute, strain hardening occurs, but to a lesser degree. Hardness of COC E at durometer A 89 lies in the middle of the range for most elastomers.

As shown in table 4, dielectric properties of E-140 are excellent. Dielectric strength is the maximum voltage required to produce dielectric breakdown in the material. Dielectric strength (ASTM D149, 500 V/second; short) is 4,000, 820 and 150 V/mil for E-140, TPV (Santoprene 201-87) and copolyester elastomer (Ecdel 9966), respectively. Dielectric constant quantifies the ability of an insulating material to store electrical energy. Dielectric constant (relative permittivity) and dissipation factor (ASTM D150, IEC 60250 and ASTM D2520) are measured across a broad range of frequencies at 23[degrees]C; 50% RH. Electrical applications where high capacitance is needed typically favor those materials with lower dielectric constant. Dielectric constant of E-140 is very low, 2.2 measured at high (microwave) frequencies between 1 and 10 GHz. Dielectric constant of SBS (Styrolux 684D) and TPV (Santoprene 201-87) are slightly higher, between 2.4 and 2.5, but are measured at much lower frequencies. Dielectric constant of copolyester elastomer (Ecdel 9966) is much higher between 3.9 and 3.8, measured at low 1 and 10 kHz frequency. Dissipation factor measures the inefficiency of an insulating material. Dissipation factor values for these elastomers follow a similar trend with dielectric constant.

Dynamic mechanical analysis (figure 1) shows four major thermal transitions for E-140, each related to the structure of this mostly amorphous random olefinic copolymer. E-140 has extremely low ductile-brittle transition temperature of <-90[degrees]C, corresponding to the glass transition of amorphous polyethylene. Ethylene-norbornene glass transition temperature, as shown by the step change in slope of the elastic modulus, occurs at about 6[degrees]C. As shown in table 4, E-140 has a Vicat softening point of 64[degrees]C, which corresponds to the onset of a second step change in slope of the elastic modulus. This is lower than the 86[degrees]C and 170[degrees]C softening point for SBS (Styrolux 684D) and copolyester elastomer (Ecdel 9966), respectively. Melt temperature of E-140 crystalline polyethylene and perhaps ethylene-norbornene phases occur at 85[degrees]C. These thermal transitions are nicely illustrated by tensile strength measured at five temperatures at 500 mm/minute strain rate. E-140 retains ductility at -25[degrees]C and -50[degrees]C, with elongation at break in excess of 200%. Sharp tensile strength at yield peaks are 30 MPa (4,350 psi) and 38 MPa (5,500 psi), respectively. E-140 shows a tensile yield point below ethylene-norbornene glass transition. At 0[degrees]C and above, tensile yield is not evident and the extent of strain hardening becomes less at 50[degrees]C, near the softening point. Electron beam crosslinking (figure 2) can greatly extend the useful upper temperature range for E-140 fabricated products. DMTA of 100 micron (4-mil) E-140 films, treated at 150-250 kV and 50-100 kGy, show increased storage modulus more than 150[degrees]C beyond the crystalline melting point. Higher energy and radiation dosage increases crosslinking and practical stiffness. E-beam crosslinking does not adversely change color or haze.

Processing

E-140 can be melt processed and fabricated into useful articles by all common thermoplastic techniques. These include mono, multi and nano-layer film and sheet extrusion, profile extrusion for hose and tubing, injection and co-injection molding, calendering, single and twin screw compounding for filler and polymer blending, multi-layer extrusion blow molding and foams. Melt process temperatures are similar to those of LLDPE, between 190[degrees]C to 260[degrees]C. Melt flow rate, measured at 190[degrees]C and 260[degrees]C, 2.16 kg, is 2.7 and 11.0 dg/ minute, respectively.

Applications

The unique combination of mechanical, barrier, optical, electrical and thermal properties of E-140 has lead to many successful commercial applications in a few short years. These applications include, but are not limited to, tubing (figure 3) and hoses, caps, gaskets, films and bags, impact modifiers, polyolefin compatibilizer, food, medical and pharmaceutical packaging, cryogenic components and dielectrics. Creativity inspired by E-140 will enable many exciting new applications in the future.

This article was originally presented at SPE's Thermoplastic Elastomers 11th Topical Conference in September 2014.

References

(1.) R.R. Lamonte, "Stiffer, thinner packaging films with improved sealing using cyclic olefin copolymers," presented at 10th Worldwide Flexible Packaging Conference, Amsterdam, The Netherlands, November 2000.

(2.) Liesl K. Massey, Permeability Properties of Plastics & Elastomers, 2nd, Plastics Design Library, 2003, pp. 436-437, 440, 444-445, 448-449.

(3.) Laurence W. McKeen, Film Properties of Plastics & Elastomers, 3rd, Plastics Design Library, 2013, pp. 193, 342-344, 346, 349.

(4.) Styrolux 684D technical data sheet, Styrolution, UL Prospector, June 2014.

(5.) Ecdel 9966 technical data sheet, Eastman Chemical Company, UL Prospector, June 2014.

(6.) Riteflex 663 technical data sheet, Celanese Corporation, UL Prospector, June 2014.

(7.) Attane 4201G technical data sheet, Dow Chemical Company, UL Prospector, June 2014.

(8.) Santoprene 201-87 technical data sheet, ExxonMobil Chemical, UL Prospector, June 2014.

by Paul D. Tatarka, Topas Advanced Polymers

Table 1--oxygen permeability of elastomers and
polymers (23[degrees]C; 50% RH)

Grade           Material type                 Supplier         Oxygen
                                                          permeability
                                                              (cc-mm/
                                                            [m.sup.2]
                                                             day atm)

8007F-04                 COC    Topas Advanced Polymers            24
Attane 4201       Ultra LDPE              Dow Chemical            279
E-140           COC elastomer   Topas Advanced Polymers           118
Riteflex 663     Copolyester      Celanese Corporation             37
                   elastomer
Ecdel 9966       Copolyester          Eastman Chemical            130
                   elastomer
Santoprene               TPV       ExxonMobil Chemical            434
  201-87
JSR RB830       Polybutadiene   Japan Synthetic Rubber            550
                       (TPE)
G-1652                  SEBS           Kraton Polymers          1,095
D-1101                   SIS           Kraton Polymers          1,717

Table 2--water vapor permeability of elastomers and
polymers (38[degrees]C; 90% RH)

Grade           Material type              Supplier      Water vapor
                                                        permeability
                                                              (g-mm/
                                                       [m.sup.2]day)

8007F-04                  COC                 Topas             0.09
Attane 4201        Ultra LDPE          Dow Chemical              0.5
E-140                     COC                 Topas              0.4
Santoprene                TPV    ExxonMobil Chemical             0.2
  201-87
JSR RB820       Polybutadiene       Japan Synthetic                7
                        (TPE)                Rubber
JSR RB830       Polybutadiene       Japan Synthetic               10
                        (TPE)                Rubber
Ecdel 9966        Copolyester      Eastman Chemical               19
                    elastomer
G-1652                   SEBS       Kraton Polymers               83
                                                      (23[degrees]C)
Estane 58315    Ether type TPU    Lubrizol Advanced              250
                                          Materials
D-1101                    SIS       Kraton Polymers              257
                                                      (23[degrees]C)
Estane 58237    Ether type TPU             Lubrizol              550
                                 Advanced Materials

Table 3--mechanical properties of elastomers

                            Grade                     Topas E-140

                             Type                   COC elastomer
                         Supplier                  Topas Advanced
                                                         Polymers

Property               Test method        Units
Specific gravity        ASTM D792          g/cc              0.94
Hardness               ASTM D2240    Durometer A               89
Water absorption        ASTM D570             %             <0.01
  (24 hours,
  23[degrees]C)
High speed puncture    ASTM D3763
Peak force                                 lbs.               270
Total energy                            ft.-lb.                33
Tensile stress at      ASTM D6328           psi             2,800
  break                                             (500 mm/min.)
Elongation at break    ASTM D6328             %               700
                                                    (500 mm/min.)
Haze                   ASTM D1003             %       1.3 (5-mil)

                         Ecdel 9966    Santoprene     Styrolux 684D
                                          201-87

                        Copolyester          TPV                SBS
                          elastomer    ExxonMobil       Styrolution
                            Eastman
                           Chemical

Property
Specific gravity               1.13         0.96               1.01
Hardness                         95           93    68 (durometer D)
Water absorption                0.4           --               0.07
  (24 hours,
  23[degrees]C)
High speed puncture
Peak force                       --           --                 --
Total energy                     --           --                 16
Tensile stress at             3,200        2,550              3,800
  break                (500 mm/min.)
Elongation at break             400          580                250
                       (500 mm/min.)
Haze                    1.0 (5-mil)           --                1.5

Table 4--thermal and electrical properties of elastomers

                                                              Topas
                                                          E-140 COC
                                     Grade                elastomer
                                      Type                    Topas
                                  Supplier                 Advanced
Property                       Test method        Units    Polymers
Ductile-brittle
transition                       ASTM D746    [degrees]C       <-90
Glass transition                  DSC/DMTA    [degrees]c          6
Vicat softening                 ASTM D1525    [degrees]c         64
Melting temperature               DSC/DMTA    [degrees]c         85
Dielectric strength              ASTM D149       V/mil.       4,000
                               (500 v/sec.;
                                    short)

Dielectric constant             ASTM D150,                       --
(1 kHz hour, 23[degrees]C)      IEC 60250,                       --
(10 kHz hour, 23[degrees]C)     ASTM D2520                       --
(1 MHz hour, 23[degrees]C)                                       --
(1 GHz hour, 23[degrees]C)                                      2.2
(5 GHz hour, 23[degrees]C)                                      2.2
(10 GHz hour, 23[degrees]C)                                     2.2

Dissipation factor              ASTM D150,
(1 kHz hour, 23[degrees]C)      IEC 60250,                       --
(10 kHz hour, 23[degrees]C)     ASTM D2520                       --
(1 MHz hour, 23[degrees]C)                                       --
(1 GHz hour, 23[degrees]C)                                  0.00026
(5 GHz hour, 23[degrees]C)                                  0.00033
(10 GHz hour, 23[degrees]C)                                 0.00030

                               Ecdel 9966
                               Copolyester   Santoprene     Styrolux
                                elastomer       201-87          684D
                                  Eastman          TPV           SBS
Property                         Chemical    ExxonMobil   Styrolution
Ductile-brittle
transition                           <-75          -54            --
Glass transition                       -3           --            --
Vicat softening                       170           --            86
Melting temperature                   205           --            --
Dielectric strength                   150          820            --

Dielectric constant                    --          2.4            --
(1 kHz hour, 23[degrees]C)            3.9           --            --
(10 kHz hour, 23[degrees]C)           3.8           --            --
(1 MHz hour, 23[degrees]C)             --           --           2.5
(1 GHz hour, 23[degrees]C)             --           --            --
(5 GHz hour, 23[degrees]C)             --           --            --
(10 GHz hour, 23[degrees]C)            --           --            --

Dissipation factor
(1 kHz hour, 23[degrees]C)           0.02           --            --
(10 kHz hour, 23[degrees]C)          0.02           --            --
(1 MHz hour, 23[degrees]C)             --           --       0.00080
(1 GHz hour, 23[degrees]C)             --           --            --
(5 GHz hour, 23[degrees]C)             --           --            --
(10 GHz hour, 23[degrees]C)            --           --            --
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Author:Tatarka, Paul D.
Publication:Rubber World
Date:Jun 1, 2015
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