Patent Publication Number: US-3970533-A

Title: Process for conversion of elastomeric phosphazene

Description:
This application is a continuation of Ser. No. 405,236 filed Oct. 10, 1973 now abandoned. 
    
    
     This invention relates to polyphosphazene elastomers which are possessed of an exceptional ease of curability and to useful articles produced from said elastomers. More particularly, it is directed to polyphosphazene elastomers of the type described in U.S. Pat. No. 3,702,833 issued Nov. 14, 1972, the disclosure of which is incorporated herin by this reference. 
     One object of this invention is to provide polyphosphazenes of the type described having curative sites which are not directly attached to the ##EQU2## backbone and which do not detract from the thermal stability of the elastomer and which can be cured by means of sulfur cures, peroxide cures, or radiation cures. 
     Another object of the invention is to provide novel phosphazene terpolymers and to provide procedures and formulations whereby the raw gums comprising the polyphosphazenes are incorporated into compositions from which useful articles with outstanding properties are obtained. 
     A further object of the invention is to provide compositions and articles which exhibit excellent solvent resistance, low temperature flexibility and good physical strength over a broad range of service conditions. 
     The phosphazene polymers of the present invention contain small but significant amounts of unsaturation in the groups attached to the P atoms of the ##EQU3## chain, in addition to aryloxy and/or alkoxy groups (both unsubstituted and substituted) attached to the P atoms, a particularly preferred substituent being an o-allyl phenoxy group. In the preferred embodiment of the invention, 0.1-5% by weight of o-allyl phenol groups are randomly distributed among the groups attached to the ##EQU4## polymer backbone. 
     Briefly, the invention contemplates the replacement of some of the chlorine atoms in linear (NPCl 2 ) polymer with a substituent which possesses at least some unsaturation in a side chain not directly attached to the P atoms in the chains. 
     The following structural formula may be taken as illustrative of the polyphosphazenes of the present invention: ##EQU5## in which Q, Q&#39; and Q&#34; represents monovalent groups randomly distributed along the -P=N- backbone, Q&#39; and Q&#34; being preferably relatively inert or unreactive alkoxy or aryloxy groups of the types described in U.S. Pat. Nos. 3,370,020; 3,515,488; 3,700,629 and 3,702,833 and others of a similar nature, the total of Q and Q&#39; groups being sufficient to replace at least 90% and preferably at least 95% but not more than 99% of the Cl atoms originally present in the linear (NPCl 2 ) polymer; and the Q&#34; groups being a group with some unsaturation e.g. a group represented by ##SPC1## 
     in which R includes some unsaturation e.g. an alkenyl group such as vinyl, allyl, crotyl or the like, the number of Q&#34; groups distributed randomly along the -P=N- chain being preferably between 0.1% and 5% of the total of Q, Q&#39; and Q&#34;. Q and Q&#39; may be either the same or may differ and each may represent more than one group. Because of the greater reactivity exhibited by the Q&#34; groups, as compared with the Q and Q&#39; groups it is believed that these groups serve as cure sites or as sites for crosslinking and vulcanization. 
     In particularly preferred copolymers according to the present invention, the groups Q, Q&#39; and Q&#34; comprise the following and are present in the relative proportions indicated: 
     
         Q            Q&#39;            Q&#34;                                             
1-90%        1-95%         0.1-5%                                         
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1.   --OCH.sub.2 CF.sub.3                                                 
                 --OCH.sub.2 C.sub.3 F.sub.6 CF.sub.2 H                   
                               --O--C.sub.6 H.sub.4 --o-allyl             
2.   --OCH.sub.2 CF.sub.3                                                 
                 --OCH.sub.2 C.sub.3 F.sub.7                              
                               --O--C.sub.6 H.sub.4 --o-allyl             
3.   --OCH.sub.2 C.sub.n H.sub.2n.sub.+1                                  
                 --OC.sub.6 H.sub.5                                       
                               --O--C.sub.6 H.sub.4 --o-allyl             
     n=1 to 4                                                             
4.   --OCH.sub.2 C.sub.n F.sub.2n.sub.+1                                  
                 --OCH.sub.2 C.sub.n Z.sub.2n.sub.+1                      
                               --O--C.sub.6 H.sub.4 --o-allyl             
     n=1, 2 or 3 n=1, 2, 3, 4, 5                                          
                 Z=F or H and not                                         
                 all Z&#39;s need be                                          
                 the same                                                 
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     The elastomers of this invention were prepared as follows: a suitable alcohol or fluoroalcohol or a mixture of alcohols and/or fluoroalcohols, together with o-allyl phenol were slowly added to sodium metal in dried tetrahydrofuran under a nitrogen atmosphere in a 3 neck, 12 liter, round bottom Pyrex flask fitted with a dropping funnel, a dry ice condenser with a H 2  vent line, and a motor driven glass stirrer. The flask was immersed in a thermostatically controlled liquid bath. After the reaction of the alcohols with sodium had proceeded to completion, a solution of linear poly(dichlorophosphazene) in benzene was added rapidly to the mixture of alkoxides and/or fluoroalkoxide(s) and o-allyl phenoxide. The chlorine atoms of the poly(dichlorophosphazene) combined readily with the alkali metal of the alkoxides and as a result, the substituted polyphosphazene derivative was produced. The derivatized product was recovered by washing the reaction mixture free of salt until the test for chloride was negative. 
     The table above gives other examples of elastomers with unsaturation in the side chains of the groups attached to the P atoms. 
     Terpolymers or copolymers containing the indicated unsaturation can be readily compounded and cured i.e. vulcanized in much the same way as presently known rubbers, producing useful products possessing an outstanding combination of properties, which are substantially retained over an extreme temperature range from temperatures as low as -80°F to temperatures as high as 400°F, thus permitting use of the vulcanizates in service applications where they will encounter such temperatures. 
     The presence of the indicated unsaturation results in polymers which can be cured more efficiently with lower levels of peroxide than polymers in which only saturated groups are attached to the polyphosphazene chain, the resulting vulcanizates possess better heat aging properties and better compression set than the corresponding polymers lacking the unsaturated side groups. They are also more amenable to curing than their saturated counterparts and it is possible to use peroxide curing agents in compositions containing carbon black fillers and to use sulfur-accelerated cures as well as radiation cures. 
     The level of unsaturated groups is quite important and may be varied according to the cure system to be used and according to the properties desired in the cured composition. For example, when the unsaturation is provided as o-allyl phenoxy groups the following is noted: 
     
         OAP Level                                                                 
        Cure            Property Improvement                              
(mol %)                                                                   
______________________________________                                    
0.02- 0.5                                                                 
        Peroxide, Radiation                                               
                        Heat aging, compression                           
                        set, modulus, hardness                            
0.5- 2  Peroxide, Radiation                                               
                        Modulus and Hardness                              
1.5- 6.0                                                                  
        Sulfur Accelerated                                                
                        Modulus, Strength and                             
                        Hardness                                          
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     The properties of several different terpolymer gums and the compounded stock obtained from them are set forth in the tables which follow, compounding having been achieved by simply mixing the several constituents with the polyphosphazene gums in a Banbury, Brabender or other conventional mixer. 
     Raw Polymer 
     Phosphonitrilic fluoroelastomer of the general formula [(CF 3  CH 2  O)(HF 2  C(CF 2 ) 3  CH 2  O)(o-allyl C 6  H 4  O)P=N] n  in which the three substituents are randomly distributed along the ##EQU6## backbone is produced by the above described method and is usually a light tan crumb which exhibits no cold flow. It posesses the following properties (average): 
     
         Specific Gravity      1.72                                                
Mooney Viscosity      15                                                  
Glass Transition                                                          
Temperature           -90°F                                        
 
    
     The raw gum feels quite tough and exhibits considerable &#34;nerve&#34;. It softens readily at high shear rates, as for example when processed on a rubber mill or in an extruder or mixer and it exhibits good green strength and nerve reduction after addition of reinforcing agents such as carbon blacks, silicas or treated clays. 
     
                                           Table I                                 
__________________________________________________________________________
Comparison of the Cured Properties of                                     
Several Preparations of Terpolymer (I)                                    
Terpolymer (I)  A   B   C   D   E   F                                     
__________________________________________________________________________
[DSV]           2.19                                                      
                    1.69                                                  
                        1.65                                              
                            2.31                                          
                                2.19                                      
                                    1.67                                  
% Gel           0.0 0.0 0.0 0.0 0.0 0.0                                   
% OAP           0.4 0.5 0.9 0.5 0.61                                      
                                    0.70                                  
Tg (°C)  -68 -69 -69 -69 -67 -68                                   
Compound (by wt.)                                                         
Polymer         100 100 100 100 100 100                                   
Silanox 101     30  30  30  30  30  30                                    
Stan Mag ELC    6   6   6   6   6   6                                     
Dicup 40C       2   2   2   1   1   1                                     
Normal Stress-Strain                                                      
Cure (min. at 320°F)                                               
                20  30  30  30  30  30                                    
Post Cure (24 hr at 212°F)                                         
50% M (psi)     137 125 88  125 188 150                                   
100% M (psi)    325 525 500 450 780 550                                   
Tensile Strength                                                          
                1850                                                      
                    1900                                                  
                        1650                                              
                            2012                                          
                                1794                                      
                                    1975                                  
% Elong. (at break)                                                       
                220 170 170 170 140 175                                   
% Tension Set (at break)                                                  
                10  9   8   6   9   9                                     
Shore A Hardness                                                          
Cure (min. at 320°F)                                               
                40  30  30  40  60  60                                    
Post Cure (24 hr at 212°F)                                         
at 73°F  59  67  64  60  64  62                                    
Aged 240 Hr. at 300°F                                              
                    71  69  66  65  60                                    
Aged 240 Hr. at 350°F                                              
                            64  64  67                                    
Aged 240 Hr. at 400°F                                              
                            62                                            
ASTM Method B %                                                           
Compression Set                                                           
Cure (min. at 320°F)                                               
                40  30  30  60  60  60                                    
Post Cure (24 hr. at 212°F)                                        
% Set (22 hr. at 212°F)                                            
                31  28  31                                                
% Set (70 Hr. at 212°F)                                            
                            36                                            
% Set (70 Hr. at 275°F)                                            
                            56                                            
% Set (70 hr. at 300°F)                                            
                            67  62  68                                    
Aged Stress-Strain                                                        
(Same Cure as for normal)                                                 
50% M (psi)                                                               
240 hr. at 300°F                                                   
                    175 125 165 146 189                                   
240 hr. at 350°F     175 174 184                                   
120 hr. at 400°F     150                                           
100% M (psi)                                                              
240 hr. at 300°F                                                   
                250 450 425 530 347 370                                   
240 hr. at 350°F     362 238 224                                   
120 hr. at 400°F     262                                           
Tensile Strength (psi)                                                    
240 hr. at 300° F                                                  
                1175                                                      
                    1275                                                  
                        1200                                              
                            1680                                          
                                1237                                      
                                    1564                                  
240 hr. at 350°F     1063                                          
                                588 954                                   
120 hr. at 400°F     700                                           
% Elong. (at break)                                                       
240 hr. at 300°F                                                   
                200 175 180 175 210 240                                   
240 hr. at 350°F     190 245 275                                   
120 hr. at 400°F     215                                           
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                                           Table II                                
__________________________________________________________________________
Effect of Filler Type and Curative Type and Level                         
On Mechanical Properties of Terpolymer (I)                                
                A   B   C   D   E   F   G   H                             
__________________________________________________________________________
Terpolymer (I)  100 100 100 100 100 100 100 100                           
Silanox 101     30  30  30  30          30                                
Stan Mag ELC    6   6   6   6   6   6   5   5                             
Carbon Black                    40          30                            
Silane Treated Clay                 40                                    
Dicup 40C       1   2   3   6   2   3                                     
Sulfur                                  0.3 0.3                           
Accelerators                            5.5 5.5                           
(% OAP As Cure Site)                                                      
                0.5 0.5 0.5 0.5 0.5 0.8 3.0 3.0                           
Normal Stress-Strain                                                      
Cure (min. at 320°F)                                               
                30  30  30  15  30  30  30  30                            
Post Cure (24 hr. at 212°F)                                        
50% M (psi)     125 215 290 400 285 125                                   
100% M (psi)    450 720 1100                                              
                            1425                                          
                                1500                                      
                                    688 1487                              
                                            1425                          
Tensile Strength (psi)                                                    
                2012                                                      
                    1065                                                  
                        1610                                              
                            1550                                          
                                1500                                      
                                    838 1837                              
                                            1775                          
% Elong. (at break)                                                       
                170 120 117 105 100 130 130 135                           
% Tension Set (at break)                                                  
                6   6   7   6   3   7                                     
Shore A Hardness                                                          
Cure (min. at 320°F)                                               
                30  60  60  25  60  40  20  20                            
Post Cure (24 hr. at 212°F)                                        
Durometer       54  67  70  72  57  50  76  81                            
ASTM Method B                                                             
Compression Set                                                           
Cure (min. at 320°F)                                               
                40  60  60  25  60  40  20  20                            
Post Cure (24 hr. at 212°F)                                        
% Set (70 hr. at 275°F)                                            
                56  38  34                                                
% Set (22 hr. at 275°F)                                            
                            33                                            
% Set (70 hr. at 300°F)  39                                        
% Set (22 hr. at 212°F)                                            
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                       Table III                                                   
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Cured Properties of Terpolymer (II)                                       
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Terpolymer (II)                                                           
               100                                                        
Silanox 101    30                                                         
Elastomag ELC  6                                                          
Dicup 40C      1                                                          
Normal Stress-Strain (Cure min. at 320°F; post cure 24 hr.         
at 212°F)                                                          
               15 min.      30 min.                                       
100% M (psi)   250          350                                           
200% M (psi)   825          975                                           
Tensile Strength (psi)                                                    
               1500         1550                                          
% Elongation (at break)                                                   
               290          265                                           
ASTM Method B (Cure 35&#39; at 320°F; post cure 24 hr. at              
212°F)                                                             
% Compression Set                                                         
(22 hr. at 158°F)                                                  
               28.8                                                       
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                       Table IV                                                    
______________________________________                                    
Cured Properties of Terpolymer (III)                                      
               A     B       C       D                                    
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Terpolymer (III) 100     100     100   100                                
Silanox 101      30      30      30                                       
Carbon Black                           30                                 
Metal Oxide      6       6       5     5                                  
Dicup 40C        1                                                        
Varox                    1                                                
Sulfur                           0.5   0.5                                
Accelerator                      5.5   5.5                                
Normal Stress-Strain (Cure 20&#39; at 320°F; post cure 24 hr.          
at 212°F)                                                          
100% M (psi)     160     125     40    125                                
200% M (psi)             575     175   590                                
Tensile Strength(psi)                                                     
                 560     575     1300  1125                               
% Elongation     170     200     440   310                                
Shore A Hardness (Cure 50&#39; at 300°F; post cure 24 hr.              
at 212°F)                                                          
Durometer        42      35      24    31                                 
ASTM Method B (same cure as for Hardness)                                 
% Compression Set                                                         
(22 hr. at 158°F)                                                  
                 35      36      58    35                                 
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                       Table V                                                     
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SULFUR (ACCELERATED) VULCANIZATION                                        
OF TERPOLYMER (I)                                                         
Formulation      A          B                                             
______________________________________                                    
Terpolymer (I)   100        100                                           
Silanox 101      30                                                       
HAF Black (N-330)           30                                            
Zinc oxide       5          5                                             
Sulfur           0.3        0.3                                           
DTDM             1          1                                             
Methyl Zimate    2          2                                             
Butyl Zimate     2          2                                             
Stress-Strain                                                             
Cure (10 min. at 320°F)                                            
100% M (psi)     562        1250                                          
200% M (psi)     1325                                                     
T.S. (psi)       2350       2087                                          
E.sub.b (%)      310        175                                           
Shore A Hardness                                                          
(Durometer)      76         81                                            
% Compression Set                                                         
(ASTM Method B)                                                           
(22 hr. at 212°F)                                                  
                 55         60                                            
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                                           Table VI                                
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RADIATION (HIGH ENERGY ELECTRONS)                                         
INDUCED VULCANIZATION OF TERPOLYMER (I)                                   
Stock A (Terpolymer (I)-100, Silanox 101-30, Stan Mag ELC-6               
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phr)                                                                      
Radiation Dose (MR).sup.1                                                 
            0   1   2   3   4   5   6                                     
50% M (psi) 75  175 240 290 500 630 655                                   
100% M (psi)                                                              
            100 500 710 980                                               
T.S. (psi)  180 1700                                                      
                    1680                                                  
                        1530                                              
                            1190                                          
                                1270                                      
                                    1030                                  
E.sub.b     405 175 150 125 85  75  65                                    
% Tension Set                                                             
            40  14  11  9   4   2   3                                     
Shore A Hardness                                                          
            45  65  65  70  74  75  75                                    
Stock B (Terpolymer (I)-100, FEF Black-30, Stan Mag ELC-6                 
__________________________________________________________________________
phr)                                                                      
Radiation Dose (MR)                                                       
            0   1   2   3   4   5   6                                     
50% M (psi) 120 630 880 1180                                              
100% M (psi)                                                              
            150                                                           
T.S. (psi)  150 1370                                                      
                    1290                                                  
                        1340                                              
                            1270                                          
                                1170                                      
                                    1100                                  
E.sub.b     110 95  65  55  40  35  30                                    
% Tension Set                                                             
            1   1   1   1   1   1   1                                     
Shore A Hardness                                                          
            45  60  65  70  73  75  75                                    
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 1. - MR = Megarad                                                        
 
    
     
                                           Table VII                               
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SILANOX 101 - REINFORCEMENT OF PEROXIDE                                   
VULCANIZED TERPOLYMER (I)                                                 
Formulation    A   B   C   D   E   F                                      
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Terpolymer (I) 100 100 100 100 100 100                                    
Silanox 101        10  20  30  40  50                                     
Stan Mag ELC   6   6   6   6   6   6                                      
Dicup 40C      1   1   1   1   1   2                                      
Stress-Strain                                                             
Cure (30&#39; at 320°F)                                                
Post Cure (24 hr at 212°F)                                         
50% M (psi)    20  50  75  125 200 600                                    
100% M (psi)   60  175 250 450 630 1512                                   
T.S. (psi)     245 662 1600                                               
                           2012                                           
                               2380                                       
                                   1963                                   
E.sub.b (%)    190 150 200 170 175 130                                    
% Tension Set (at Break)                                                  
               4   2   5   10  23  38                                     
Shore A Hardness                                                          
(Durometer)    21  30  44  60  76  88                                     
% Compression Set                                                         
(ASTM-Method B)                                                           
(70 hr at 275°F)                                                   
               20  36  43  56  80  89                                     
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                                           Table VIII                              
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REINFORCEMENT OF PEROXIDE VULCANIZED                                      
TERPOLYMER (I) WITH SELECTED AGENTS                                       
Formulation    A   B   C   D   E                                          
__________________________________________________________________________
Terpolymer (I) 100 100 100 100 100                                        
Silanox 101    30                                                         
Aerosil 300        15                                                     
SAF Black (N-110)      30                                                 
FEF Black (N-550)          25                                             
MT Black (N-990                35                                         
Stan Mag ELC   6   6   6   6   6                                          
Dicup 50C      1   1   6   2   2                                          
Stress-Strain                                                             
Cure (min. at 320°F)                                               
               30  10  30  30  30                                         
Post Cure (24 hr at 212°F)                                         
50% M (psi)    125 230 150 125 82                                         
100% M (psi)   450 980 500 1000                                           
                               600                                        
T.S. (psi)     2012                                                       
                   1420                                                   
                       2062                                               
                           1812                                           
                               1012                                       
E.sub.b (%)    170 120 270 140 125                                        
% Tension Set (at break)                                                  
               10  10  22  2   3                                          
Shore A Hardness                                                          
(Durometer)    60  74  64  58  40                                         
% Compression Set                                                         
(ASTM-Method B)                                                           
               56  100 77  38  21                                         
(70 hr at 275°F)                                                   
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                       Table IX                                                    
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RETENTION OF STRESS-STRAIN AND HARDNESS FOR A                             
TERPOLYMER (I) STOCK AGED AT 275-400°F                             
(FORCED AIR OVEN - ASTM-D-573)                                            
Formulation    Terpolymer (I) - 100                                       
               Silanox 101 (30) - 30                                      
               Stan Mag ELC - 6                                           
               Dicup 40C - 1                                              
Aging     50% M    100% M   T.S.  E.sub.b (%)                             
                                        Shore A                           
Conditions                                                                
          (psi)    (psi)    (psi)       Hardness                          
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Original  125      532      1913  165   60                                
275°F                                                              
72 hrs.   187      808      2000  160   62                                
120 hrs.  175      650      1775  150   62                                
240 hrs.  200      763      1975  160   64                                
336 hrs.  175      500      1863  180   63                                
672 hrs.  200      455      1595  190   65                                
1000 hrs. 226      644      1490  170   67                                
300°F                                                              
72 hrs.   150      550      1900  170   62                                
120 hrs.  150      475      1775  185   68                                
240 hrs.  165      530      1680  175   66                                
336 hrs.  170      440      1460  175   64                                
672 hrs.  200      500      1525  190   64                                
1000 hrs. 240      480      1450  200   64                                
350°F                                                              
72 hrs.   175      400      1442  200   64                                
120 hrs.  170      365      1500  215   64                                
240 hrs.  175      362      1063  190   64                                
400°F                                                              
24 hrs.   155      275      1215  240   62                                
48 hrs.   125      250      1000  220   62                                
72 hrs.   150      280       840  210   64                                
120 hrs.  150      262       700  215   65                                
240 hrs.  200      300       412  155   62                                
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     In the preceding tables various tradenames and abbreviations are utilized, the meanings of which are as follows: 
     Terpolymer (I) is a linear polyphosphazene with three randomly distributed substituents; namely: CF 3  CH 2  O-; HF 2  C(CF 2 ) 3  CH 2  O- and o-allyl phenoxy 
     Terpolymer (II) is a linear polyphosphazene with three randomly distributed substituents; namely: CF 3  CH 2  O-; CF 3  (CF 2 ) 2  CH 2  O- and o-allyl phenoxy (OAP) 
     Terpolymer (III) is a linear polyphosphazene with three randomly distributed substituents; namely: C 6  H 5  O-; CH 3  (CH 2 ) 3  CH 2  O- and OAP 
     Silanox 101 is a silane-coated fumed silica 
     Stan Mag ELC is MgO 
     Dicup 40C is dicumyl peroxide (40% on CaCO 3 ) 
     Varox is 2,5-bis(t-butylperoxy)-2,5-dimethylhexane (50% on inert carrier) 
     MBT is mercaptobenzothiazole 
     Cyclex B is t-Butyl-2-mercaptobenzothiazole sulfenamide 
     Butyl Zimate is dibutyl dithiocarbamate 
     Methyl Zimate is dimethyl dithiocarbamate 
     phr means per hundred parts of polyphosphazene rubber 
     M is Modulus 
     DTDM is dithiodimorpholine