Blends of polycarbonates with polyamides, having high impact strength and high flexural modulus

A polymer blend comprising an aliphatic polyamide matrix and a dispersed phase of a polycarbonate and a compatibilizing agent having pendant succinic anhydride groups or epoxide groups, made under such blending conditions that the polymer stock melt temperature is 290.degree.-350.degree. C., has a combination of excellent toughness and stiffness properties.

BACKGROUND OF THE INVENTION 
This invention relates to a process for making blends of polycarbonates 
with certain polyamides, which blends have high notched Izod impact 
strength and frequently also an unexpectedly high flexural (or flex) 
modulus. 
It is well known in the polymer industry to make polymer blends that have 
improved properties, when compared with the properties of the individual 
blend components. For example, it is a common practice to blend 
engineering resins such as, for example, polyamides, polyesters, or 
polycarbonates with low flex modulus, soft, rubbery polymers in order to 
improve their toughness (or impact strength). U.S. Pat. Nos. 4,172,859 and 
4,174,658, both to Epstein, represent what is believed to be the most 
successful earlier work in this area. For the purpose of this invention, a 
polymer blend which has a notched Izod impact strength of at least 10 
ft.lb/in (534 J/m), as determined according to ASTM Standard D256, is 
considered to be "supertough". Most Epstein blends are supertough. 
While the starting engineering resins have high flex modulus, the flex 
modulus of the toughened engineering resins ordinarily is decreased, 
sometimes significantly. In some applications, this is not considered a 
drawback, but in some other applications such as, for example, machine 
parts or automobile parts, this would be a drawback. 
Blends of crystalline polyamides, such as, for example, nylon 6 with 
polycarbonates also are known; see, for example, U.S. Pat. Nos. 4,782,114 
to Perron and 5,008,374 to Thill. Such blends normally also contain a 
third and in some cases a fourth component, which is a polymeric 
compatibilizing agent, having low glass transition temperature and low 
flex modulus. Those blends have very high impact strength, but their flex 
modulus always is lower, sometimes significantly so, than that of the 
starting polyamide. The starting polycarbonate itself most often has a 
flex modulus that is lower than that of the polyarnide, and the flex 
modulus of the blend can be lower than that of the polycarbonate as well, 
so that in this case, the final composition may not have sufficient 
stiffness for those special applications. 
It is customary in the industry to make polymer blends at the lowest 
temperature at which they can be melt processed, usually about 
10.degree.-60.degree. C. above the melting temperature of the highest 
melting polymer. In the case of nylon 6, which melts at about 220.degree. 
C., the processing temperature normally is no higher than about 
260.degree. C., although Perron describes operations at temperatures as 
high as 287.degree. C. 
Certain aliphatic polyamides such as, for example, nylon 11, nylon 12, and 
nylon 12,12, have rather low flex moduli, which would be considered 
marginal in many engineering resin applications. Those polyamides can be 
readily toughened to high values, but their stiffness normally decreases 
below acceptable level. Blends of such polyamides with polycarbonates and 
toughening agents do not have a satisfactory toughness/stiffness 
combination. 
There is a need, therefore, for a blend of such polyamides with a 
polycarbonate that would not only have high impact strength but also high 
stiffness. 
SUMMARY OF THE INVENTION 
According to the present invention, there is now provided a process for 
making a supertough polymer blend composition, said process consisting in 
blending the following components A, B, and C in the indicated 
proportions: 
C, 2-30% of an engineering grade polycarbonate resin; 
B, 3-20%, total, of at least one elastomeric compatibilizing agent carrying 
0.1-5% of at least one type of pendant groups selected from the class of 
succinic anhydride and epoxide groups; and 
A, 50-95% of an engineering grade polyamide resin selected from the group 
consisting of nylon 6, nylon 11, nylon 12, nylon 6,12, nylon 12,12, and 
mixtures of two or more of those polymides; the amount of polyamide A 
always being equal to 100% -(B%+C%); 
all the above percentages being by weight; 
under such conditions that the stock melt temperature is about 290.degree. 
C. to 350.degree. C., for a sufficient time to obtain a uniform dispersion 
of the polycarbonate and compatibilizing agent in polyamide matrix; 
the resulting blend having a flexural modulus, as determined according to 
the ASTM Standard D790, that is always at least as high as the lower of 
that of the polyamide and of the polycarbonate: 
said blend consisting essentially of a polyamide matrix and a dispersed 
phase consisting of the polycarbonate and the compatibilizing agent. 
There also is provided a polymer blend composition made by the above 
process,

DETAILED DESCRIPTION 
The polyamides suitable in the blend compositions of the present invention 
are commonly known and employed as engineering resins. They are 
semicrystalline or crystalline polymers, with melting points above 
170.degree. C. Such polyamides frequently are referred to in the industry 
as nylons. Those used in the present invention are commercially available. 
Nylon 6,6 (polyhexamethylene adipamide) is not suitable in the process of 
the present invention because it is not sufficiently thermally stable to 
be processed at the high temperatures required in the present invention. 
The preferred polyamide is nylon 6 because it has a good flex modulus, is 
industrially used in large volume as an engineering resin, and is for that 
reason readily available from several sources. 
The polycarbonates suitable in the practice of the present invention are 
well known and many are commercially available, among others, from General 
Electric Co. They also are sometimes known as polyarylates. Polycarbonates 
are derived from cyclic, usually aromatic, diols and carbon dioxide and 
normally are made by a reaction of the diol with phosgene or a 
chloroformate. Typical aromatic diols that are used in the manufacture of 
polycarbonates are dihydroxybenzenes, especially resorcinol, diphenols, 
Bisphenol A, and Bisphenol F. Commercially available polycarbonates are 
amorphous resins, which crystallize on annealing. They retain their 
amorphous state during melt processing. 
The compatibilizing agent is a functionalized rubber such as, for example, 
maleated EP or EPDM rubber or maleated styrene-butadiene rubber, maleated 
styrene/ethylene/butylene-1 rubber, and maleated styrene/ethylene/propene 
rubber. The acronyms EP and EPDM are known in the industry. The former 
stands for an ethylene/propylene copolymer; the latter stands for a 
terpolymer or tetrapolymer of ethylene with propylene and with a diene 
having only one terminal double bond, which may also contain a fourth 
ethylenically unsaturated monomer. The succinic anhydride group can be 
introduced into the elastomer either by copolymerization with a monomer 
such as maleic anhydride, fumaric acid, maleic acid, monomethyl maleate, 
or itaconic acid or by grafting an elastomeric material with maleic 
anhydride or with fumaric acid, as is well known in the art. 
Other compatibilzing agents include elastomeric materials containing both 
succinic anhydride groups and carbon monoxide groups such as, for example, 
maleated ethylene/butyl acrylate/carbon monoxide terpolymer. Still further 
compatibilizing agents can contain epoxy groups such, for example, 
ethylene/butyl acrylate/glycidyl methacrylate terpolymer, ethylene/butyl 
acrylate/carbon monoxide terpolymer grafted with glycidyl methacrylate, 
and EP or EPDM rubber grafted with glycidyl methacrylate. All such 
copolymers are well known and some are commercially available. 
Preferably, the amount of pendant succinic anhydride and/or epoxide groups 
is 0.3-3%. 
The preferred nylon 6 or nylon 6,12 composition consists of 70-85% of 
nylon, 10-15% of compatibilizing agent, and 5-15% of polycarbonate. The 
preferred compositions containing nylon 11, nylon 12, or nylon 12,12 
consist of 55-90% of polyamide, 5-15% of compatibilizing agent, and 5-30% 
of polycarbonate. 
In the practical operation of the process of the present invention, the 
components are fed directly to the blending equipment, usually an 
extruder, although other blending equipment such as a Banbury mixer or a 
rubber mill can be used as well. A two-step process involving preblending 
of the polycarbonate with the compatibilizing agent also is possible but 
would be more expensive than direct blending. 
The extruder temperature is set at a sufficiently high temperature to 
obtain a stock melt temperature of 290.degree.-350.degree. C. The actual 
machine setting normally will be below the desired value, but further 
temperature increase is caused by the high shear. Once the machine 
parameters such as temperature, extrusion rate, and revolutions per minute 
are set, they are maintained constant throughout the operation. 
For a given nylon, the flex moduli of the blends of the present invention 
are to a large degree dependent on the relative proportions of their 
components and especially on the amount of the compatibilizing agent. But, 
generally speaking, depending on the particular polymers, and especially 
the particular nylon used, one of three situations may occur: (a) the 
final flex modulus is higher than the flex modulus of both the starting 
polyarnide and the starting polycarbonate; (b) the final flex modulus is 
lower than that of the starting polyarnide but higher than that of the 
starting polycarbonate; or (c) the final flex modulus is lower than that 
of the starting polycarbonate but higher than that of the starting 
polyamide (when the polyamide is nylon 11, nylon 12, or nylon 12,12). The 
process of the present invention can in each one of those three situations 
produce a blend that has high impact strength and the highest attainable 
flex modulus for a given composition. 
Under the process conditions of the present invention, polyamide always 
forms the matrix and polycarbonate and the compatibilizing agent the 
dispersed phase. This can be readily ascertained by a conventional 
technique such as, for example, scanning electron microscopy (SEM), 
without and with chloroform extraction. Chloroform extracts polycarbonate 
but does not dissolve polyamide. Comparison of SEM photomicrographs before 
and after extraction will prove that this requirement has been met. 
While the inventor does not know why the process conditions described and 
claimed herein produce blends which have high Izod impact strengths and 
high flex moduli, he has established, nevertheless, that certain chemical 
changes occur in those blends as a result of exposure to simultaneous high 
temperature and high shear. Three different techniques, differential 
mechanical analysis, infrared spectroscopy, and nuclear magnetic resonance 
spectroscopy, have been used to show those changes, although their 
chemical significance still is not understood. 
This invention is now illustrated by the following examples of certain 
representative embodiments thereof, where all parts, proportions, and 
percentages are by weight unless otherwise indicated. All data of weight 
and measure not originally obtained in SI units have been converted to SI 
units. 
I) GLOSSARY OF POLYMERS 
A) POLYMER A: POLYAMIDE 
A1: Nylon 6 with relative viscosity, RV, (ASTM Standard D-789) about 58-62. 
Available from Nylon de Mexico, S.A. under the trademark and grade 
designation DURAMIDA.RTM. 6. 
A2: Nylon 12,12, formerly offered by Du Pont of Canada under the trademark 
and grade designation ZYTEL.RTM. 1212. It had an inherent viscosity, IV, 
of 1.2 dl/g, and a specific gravity of 1.022 g/cm.sup.3. 
A3: Nylon 12, made by Atochem USA under the trademark AECNO RILSAN.RTM. TL. 
It has a melting point of 174.degree. C. and a specific gravity of 1.02 
g/cm.sup.3. 
B) POLYMER B: COMPATIBILIZING A GENT 
B1: EPDM rubber containing about 0.12 % of copolymerized norbornadiene, 
grafted with a monomer providing about 2 % of succinic anhydride groups 
(maleic anhydride, maleic acid, or fumaric acid). 
B2: EPDM rubber similar to B1, except that it had a slightly lower 
molecular weight than B1; grafted to contain about 2% of succinic 
anhydride groups. 
B3: The same EPDM as B1, but grafted with 0.73% of glycidyl methacrylate. 
It had a melt flow rate, MFR, at 280.degree. C. of 0.09 dg/min. 
B4: A terpolymer of ethylene with n-butyl acrylate and carbon monoxide (an 
E/n-BA/CO terpolymer) in their respective amounts of 60:10:30%, grafted 
with 0.8 % of maleic anhydride. It had an MFR at 190.degree. C. of 6.5 
dg/min. 
B5: A terpolymer of ethylene with n-butyl acrylate and glycidyl 
methacrylate (an E/n-BA/GMA terpolymer) in their respective amounts of 
66.8:28: 5.2%. It has a Tg of about -60.degree. C. 
B6: An E/n-BA/GMA terpolymer, with respective comonomer amounts of 
72.6:26:1.4 %. 
B7: A styrene/ethylene-butylene/styrene copolymer, grafted with about 2% of 
maleic anhydride, available from Shell Chemical Company under the 
trademark KRATON.RTM. FG 1901X. 
C) POLYMER C: POLYCARBONATE 
C1: Polycarbonate, available from General Electric Company under the 
trademark and grade designation LEXAN.RTM. 101. It has a MFR at 
300.degree. C. of 6.5 dg/min. 
C2: Polycarbonate, available from the same source as LEXAN.RTM. HF1110. It 
has a MFR of 22 dg/min. 
II) EXTRUDER 
MI: A Werner&Pfleiderer (W&P) twin-screw extruder equipped with bilobal 
30-mm diameter screws and divided into four zones set at the same 
temperature. The extruder has a vacuum port at the end. 
M2: A W&P twin-screw extruder equipped with trilobal 28mm diameter screws 
and divided into five heating zones. It has a vacuum port a the end. 
M3: A twin screw, "ZSK", W&P extruder equipped with 53mm diameter trilobal 
mixing screws and divided into ten heating zones. It has a vacuum port at 
the end. 
M4: A twin screw, "ZSK" W&P extruder equipped with 40mm diameter bilobal 
screws and divided into five heating zones. It has a side feed port for 
glass fibers and a vacuum port at the end. It has a rated throughput 
capacity of about 30 kg/hr. 
Note: The the term "stock polymer temperature", used in the examples, means 
the temperature of the polymer exiting the die, measured with a hand-held 
thermocouple. Each extruder was operated at a set temperature such that 
the stock polymer temperature at the given shear rate was at the desired 
level within the 290.degree. C.-350.degree. C. range. 
III) MOLDING 
Extruded and pelletized polymers were dried overnight at 
90.degree.-110.degree. C. They were injection molded in a nominal 6-ounce 
(177-ml) machine made by HMP Company, running at a cycle ratio of 20 
see/20 sec. The actual melting temperature for each nylon during molding 
was determined with a hand-held device. The mold cavity temperature was 
about 40-60.degree. C. The molding specimens were 0.3175 cm thick and 
either flex bar type (1.27.times.11.43cm) or dog bone type 
(1.27.times.21.6 cm). 
IV) TESTING 
a) Flexural (flex) modulus was determined according to ASTM D-790. 
b) Notched Izod impact strength was determined according to ASTM D-256. 
c) Tensile strength and elongation at break were determined according to 
ASTM D-638. 
The above determinations (a) through (c) were made on "dry as molded" 
samples. 
EXAMPLES 1 AND 2 
These examples show an unexpected combination of high stiffness and 
toughness of the blends. In each run, the total weight of each sample was 
from 4 to 5 kg. The compositions of Examples 1 and 2 were the same: 
A1/B1/C2, 80:10:10%. 
Polymer A 1 pellets and Polymer C2 pellets were dried overnight under 
vacuum at 110.degree. C. and fed, along with Polymer B1. The polymer blend 
was molded at two different set temperatures, with the mold temperature 
set at 60.degree. C. Table 1, below, provides the experimental conditions 
and lists certain physical properties of those blends, as well as those of 
the starting polyamide A1, the starting polycarbonate C2, and a commercial 
supertough nylon. Both the notched Izod impact strength and the flex 
modulus of the blends of Examples 1 and 2 were surprisingly high. This is 
especially remarkable when compared with ZYTEL.RTM. ST801, which is 
considered to be a state of the art supertough nylon. The data for 
ZYTEL.RTM. ST801 are taken from the sales bulletin of E. I. du Pont de 
Nemours and Company. 
TABLE 1 
______________________________________ 
Example 
1 2 A1 C2 ST801.sup.1 
______________________________________ 
Rev. per minute 
300 300 N/A.sup.2 
N/A.sup.2 
N/A.sup.2 
Production rate, kg/min 
9.1 9.1 N/A.sup.2 
N/A.sup.2 
N/A.sup.2 
Stock melt temp., .degree.C. 
300 300 N/A.sup.2 
N/A.sup.2 
N/A.sup.2 
Extruder M1 M1 N/A.sup.2 
N/A.sup.2 
N/A.sup.2 
Molding temperature, .degree.C. 
240 260 260 300 270 
Flex modulus, MPa 
2620 3172 2758 2310 1689 
Notched Isod, J/m 
1174 907 53.4 641 961 
Tensile strength, MPa 
64.1 71.0 82.7 85.5 51.7 
Elongation at break, % 
63 25 60 120 60 
______________________________________ 
.sup.1 Supertough ZYTEL .RTM. ST801 nylon from E.I. du Pont de Nemours an 
Company 
.sup.2 Not applicable because in these runs no compounding was done and 
each sample was molded without prior extrusion. 
EXAMPLES 3-8 
The following examples illustrate various types of compatibilizers that can 
be used to produce a blend with a good combination of stiffness and 
toughness. In each case, the composition was A1/B/C2, 80:10:10%. Table 2 
provides the flex modulus and notched Izod values for blends in which the 
compatibilizer B was varied as shown. For completeness, Example 1 of Table 
1 also should be considered, The extruder was M2. 
TABLE 2 
______________________________________ 
Example 
3 4 5 6 7 8 
______________________________________ 
Rev. per minute 
140 200 200 200 200 200 
Prod. rate, kg/hr 
14.5 14.5 13.2 11.8 11.8 11.3 
Stock melt temp., .degree.C. 
330 306 305 301 302 314 
Molding temp., .degree.C. 
260 245 245 240 245 260 
Polymer B B2 B3 B4 B5 B6 B7 
Flex Mod., MPa 
2200 2379 2413 2413 2517 2689 
Notched Izod, J/m 
1068 1068 1068 673 694 587 
______________________________________ 
It can be seen from Table 2 that different kinds of compatibilizer B can be 
used to give toughness ranging from about 600 to more than 1000 J/m, while 
flex modulus is about 2200-2700 MPa. Example 1 (Table 1) gave even higher 
impact strength and flex modulus values. Such a combination of high 
toughness and high stiffness for nylon 6 compositions is unusual. 
EXAMPLES 9 AND 10 
The following examples show that the molecular weight of polycarbonate (C1 
or C2) is not critical. The results of these examples should be compared 
with those reported for Examples 1 and 8, above, where polycarbonate C was 
C2. The polyamide in all the examples was A1, and all the compositions 
were A/B/C, 80:10:10%. The experimental data and results are presented in 
Table 3, below. 
TABLE 3 
______________________________________ 
Example 9 10 
______________________________________ 
Rev./min. 100 100 
Prod. rate, kg/hr 7.3 6.4 
Stock melt temp., .degree.C. 
290 292 
Extruder M1 M2 
Molding temp., .degree.C. 
250 250 
Polymer C C1 C1 
Polymer B B1 B7 
Flex Modulus, MPa 2620 2654 
Notched Izod, J/m 1228 1041 
Tensile strength, MPa 
73.0 68.3 
Elongation at break, % 
50 30 
______________________________________ 
EXAMPLES 11-17 
Blends of Polymer A3, Polymer B1, and Polymer C1 or C2 were made in 
Extruder M 1 operated at 150 rev./min. Test samples were molded at 
250.degree. C. The relative amounts of the blend components were varied as 
shown in Table 4, below. Good stiffness and toughness were obtained 
through the entire range of those compositions. 
TABLE 4 
______________________________________ 
Example 
11 12 13 14 15 16 17 
______________________________________ 
Prod. rate, kg/hr. 
8.6 9.3 9.3 9.3 9.4 9.7 9.9 
Stock melt temp., 
311 310 309 310 310 310 311 
.degree.C. 
Polymer A3, % 
90 80 75 75 65 60 50 
Polymer B1, % 
5 5 5 10 10 10 10 
Polymer C2, % 
5 15 20 0 0 0 0 
Polymer C1, % 
0 0 0 15 25 30 40 
Flex modulus, MPa 
1379 1517 1586 1413 1413 1449 1482 
Notched izod, J/m 
1228 1281 801 1174 1121 961 801 
Tensile strength, 
41.3 46.2 43.4 39.3 40.0 39.3 39.3 
MPa 
Elongation at 
200 150 75 150 90 70 100 
break, % 
______________________________________ 
The above results can be compared with similar data obtained for polyamide 
A3 alone (Contr. 1) and for a conventional impact-resistant polyamide 
(Comp. 1), which are given below in Table 5. 
TABLE 5 
______________________________________ 
Example 
Contr. 1 
Comp. 1 
______________________________________ 
Prod. rate, kg/hr 8.4 8.5 
Stock melt temp., .degree.C. 
263 261 
Polymer A3, % 100 90 
Polymer B1, % 0 10 
Flex modulus, MPa 1379 1207 
Notched Izod, J/m 96 907 
______________________________________ 
The comparison suggests that the conventional toughening method improves 
the toughness at the expense of the stiffness (Comp. 1 vs. Contr. 1), 
while the present invention improves the toughness without decreasing the 
stiffness, and in some cases even increases the stiffness. 
EXAMPLES 18-21 
In these example, nylon 12,12 (Polymer A2) was used. All the polymer blends 
were extruded with Machine M1. All the samples were molded at 270.degree. 
C. The experimental data are given in Table 6, below. Comparing these 
results with data for the control polyamide A2 (taken from a sales 
bulletin), one sees that toughness was increased without decreasing 
stiffness. 
TABLE 6 
______________________________________ 
Example 
18 19 20 21 Contr. 2* 
______________________________________ 
Rev./min. 200 250 250 250 N/A 
Prod. rate, kg/hr. 
5.4 16.5 16.9 16.1 N/A 
Stock melt temp., .degree.C. 
357 332 332 323 N/A 
Polymer A2, % 85 80 70 80 100 
Polymer B1, % 5 5 10 5 0 
Polymer C1, % 10 15 20 0 0 
Polymer C2, % 0 0 0 10 0 
Flex, modulus, MPa 
1482 1620 1413 1482 1344 
Notched, Izod, J/m 
801 747 961 534 58.7 
Tensile strength, MPa 
43.4 41.4 39.3 41.4 41.4 
Elongation at break, % 
35 40 50 40 27 
______________________________________ 
*Commercial polyamide. All data taken manufacturer's technical bulletin 
EXAMPLES 22-24 
These examples show that the process of this invention can be carried out 
in a commercial scale production equipment such as Extruders M3 and M4. 
Examples 23 and 24 also show that glass fibers can be added to the blend 
to further improve stiffness. 
The composition of Example 22 was an 80:10:10% blend of A1, B1, and C1, 
made in Extruder M3 operated at a rate of 74.4 kg/hr, the stock melt 
temperature being 300.degree. C. The blend pellets were dried at 
100.degree. C. under vacuum and molded at 240.degree. C. 
The blends of Examples 23 and 24 were made in Extruder M4 from the blend of 
Example 22, feeding glass fibers through the side port. The glass fibers 
were of type PPG3540.RTM.(Pittsburgh Plate Glass Co.). The polymer blend 
pellets were introduced first. The temperature setting of the extruder 
barrel was 270.degree. C. Test bars were molded at 240.degree. C. The 
compositions and test data are reported below in Table 7. 
TABLE 7 
______________________________________ 
Example 
22 23 24 
______________________________________ 
Blend from Example 22, pts. 
100 95 90 
Glass fibers, pts. 
0 5 10 
Flex modulus, MPa 2482 2758 3103 
Notched Izod, J/m 1281 400 240 
______________________________________ 
While a good improvement of stiffness could have been expected, the notched 
Izod values are unexpectedly good. Usually, addition of as little as 5% of 
glass fibers, decreases the notched Izod value below 160 J/m. The impact 
strength in Examples 24 and 25 is below the values obtained in all the 
previous examples of this disclosure but still is far better than that of 
the polyamide A1 alone, given in Table 1 as 53.4 J/m. Comparison with 
commercial glass fiber-reinforced toughened nylon 6 (DuPont's ZYTEL.RTM. 
71G13L, which contains 13% of glass fibers) also shows the superior impact 
strength of the blend of the present invention. The commercial glass 
fiber-reinforced material has a flex modulus of 3792 MPa but a notched 
Izod impact strength of only 123 J/m. 
ANALYTICAL METHODS (Examples An-1 to An-9) 
Examples An 1 -An 3--Dynamic Mechanical Analysis 
These examples show a correlation of the improved mechanical properties of 
the compositions of the present invention with the process conditions via 
Dynamic Mechanical Analysis (DMA) according to ASTM Standard D-4092-90. 
All the compositions were A1/B1/C2 in respective amounts of 80:10:10 %, 
and were extruded in Extruder M1. The samples of Examples An 2 and An 3 
were identical with those of Examples 1 and 2, respectively, reported 
above. The .DELTA.t value is the difference between the DMA temperature of 
the polycarbonate peak and of the nylon peak. The mechanical properties of 
the samples are given in Table 8. 
TABLE 8 
______________________________________ 
Example 
An 1 An 2 An 3 
______________________________________ 
Stock poly, 252 304 300 
temp., .degree.C. 
Molding temp., .degree.C. 
240 240 260 
Flex mod., MPa 2227 2923 3172 
Notched Izod, J/m 
160 1121 907 
DMA ANALYSIS 
Nylon peak, .degree.C. 
70 75 74 
Polycarbonate peak, 
151 145 131 
.degree.C. 
.DELTA.t, .degree.C. 
81 70 57 
______________________________________ 
FIG. 1 is a plot of tan 6 (or damping peak) vs. scanning temperature. Curve 
1 is for the above Example An 1; curve 2 for Example An 2; and curve 3 for 
example An 3. These curves show that the higher the processing temperature 
the lower is the carbonate damping peak, and that .DELTA.t is smaller. 
One can further conclude from the above data that the smaller the .DELTA.t 
value the better is the stiffness/toughness combination. 
Examples An 4-An 7, Infrared Spectroscopy (IR) 
These examples correlate the mechanical properties of the polymer blends of 
the present invention with the process conditions by means of infrared 
spectroscopy. All the blends had the composition A1/B1/C2, in respective 
amounts of 80:10:10% and were extruded in Extruder M1. The information is 
reported in Table 9, below. 
TABLE 9 
______________________________________ 
Example 
An 4 An 5 An 6 An 7 
______________________________________ 
Stock melt temp., .degree.C. 
283 304 304 304 
Molding temp, .degree.C. 
240 240 260 270 
Flex modulus, MPa 2455 923 2827 2827 
Notched Izod, J/m 320 121 1174 961 
Infrared peak normalized area 
Nylon 1 1 1 1 
Polycarbonate 0.93 0.74 0.61 0.32 
Ratio: polycarbonate/nylon area 
0.93 0.74 0.61 0.32 
______________________________________ 
FIG. 2 is a plot of absorbance vs. the wave number. Curve 5 refers to 
example An 5; curve 6 to example An 6; and curve 7 to Ex An 7. These 
curves show that the higher the processing temperature the lower is the 
absorbance of the carbonate bond. 
The nylon peak was taken at 1375 cm.sup.-1 and the polycarbonate peak at 
1775 cm.sup.-1. The initial area ratio of the polycarbonate peak to the 
nylon peak will depend on, but will not necessarily be the same as, the 
weight ratio of the starting materials. However, for the same weight 
ratios of blend polymers, the smaller the peak area ratio the better is 
the toughness/stiffness combination. 
Examples An 8 and An 9, Nuclear Magnetic Resonance (NMR) 
These examples correlate the mechanical properties and the process 
conditions by means of HNMR. Both examples had the same composition, 
A1/B1/C2 in respective amounts of 80:10:10%. However, the process 
conditions were different, and this affected the mechanical properties of 
the blends. FIG. 3A represents the sample of Example An 8, while FIG. 3B 
represents the sample of Example An 9. The extrusion and molding 
conditions were identical for Examples An 4 and An 8. They also were 
identical for Examples An 7 and An 9, Extrusion conditions were identical 
for Examples An 5, An 6, and An 9, but the molding conditions of Examples 
An 5 and An 6 were different from those of Example An 9. The effect of 
process conditions can be shown by measuring the ratio of the peak areas 
at 7 and 6.6 ppm. Hydrogen atoms on polycarbonate aromatic rings are 
mainly located in the area of 6.9-7.1 ppm, as can be seen in FIG. 3A. 
Processing at a high temperature results in a strong peak at 6.6. ppm, 
which can be well seen in FIG. 3B. It also is present in FIG. 3A but is 
weak. While the optimum peak area ratio depends on the starting amounts of 
nylon and polycarbonate, it appears that improved properties of the blend 
are observed for a smaller ratio. In both examples, Extruder M1 was used. 
The results are presented in Table 10, below. 
TABLE 10 
______________________________________ 
Example 
An 8 An 9 
______________________________________ 
Stock polymer temp., .degree.C. 
283 304 
Molding temp., .degree.C. 
240 270 
Flex modulus, MPa 2455 2827 
Notched Izod, J/m 320 961 
NMR 
Area under 7 ppm peak 
12.8 57.3 
Area under 6.6 ppm peak 
0.35 18.2 
Peak area ratio, 7/6.6 ppm 
37 3.2 
______________________________________ 
While the analytical methods described above provide some information about 
the blend products, the values of the various readings obtained cannot be 
quantitatively correlated with any well-defined composition. These 
analytical results can be roughly rationalized as follows: 
DMA shows gradual disappearance of the polycarbonate and formation of a new 
chemical component of unknown structure. This new component may be 
responsible for the improved toughness/stiffness combination. 
IR analysis also suggests that some polycarbonate bonds are destroyed to 
form a new chemical component. 
The NMR spectrum is responsive to hydrogen atoms on the aromatic ring of 
polycarbonate. As a result of the above-discussed unknown chemical 
changes, the hydrogen atoms are no longer in the same magnetic field. 
ADDITIONAL EXAMPLES OF THE INVENTION 
EXAMPLES 25-30 
Blends of Polymers A1, B 1, and C2 in respective percentages of 80:10:10% 
were made in Extruder M1 operated at 200 rev./min. The extruded materials 
were molded at a temperature of 240.degree. C., with a mold at 60.degree. 
C., and a 20 sec/20 see cycle. The properties of those blends vary 
considerably with the extrusion temperature, as is shown in Table 11, 
below. 
TABLE 11 
______________________________________ 
Example 
25 26 27 28 29 30 
______________________________________ 
Stock melt temp., 
269 276 282 294 304 336 
.degree.C., 
Flex modulus, MPa 
2260 2210 2460 2750 2920 2870 
Notched Izod, J/m 
160 213 320 1280 1120 1170 
______________________________________ 
As can be seen, the increase of both notched Izod impact strength and flex 
modulus with the increase of stock melt temperature from 282.degree. C. to 
294.degree. C. is dramatic. 
EXAMPLES 31-32 
A polymer blend A1/B1/C1, 85:5:10%, was prepared in Extruder M1 at two 
different stock melt temperatures. The molding conditions were the same as 
in Example 30. The results are shown in Table 12, below. 
TABLE 12 
______________________________________ 
Example 
31 32 
______________________________________ 
Stock melt temp., .degree.C. 
251 330 
Rev./min 100 150 
Flex mod., Mpa 2290 2830 
Notched Izod, J/m 123 1120 
______________________________________ 
Here again, the increase of both notched Izod impact strength and flex 
modulus with increase of stock melt temperature from 25 1.degree. C. to 
330.degree. C. is dramatic. 
EXAMPLES 33-34 
A polymer blend of A1/B1/C1, 70:10:20%, was prepared at two different stock 
melt temperatures. Here again, the increase of notched Izod impact 
strength with higher processing temperature was remarkable, as show in 
Table 13, below. 
TABLE 13 
______________________________________ 
Example 
33 34 
______________________________________ 
Stock melt temp., .degree.C. 
270 322 
Rev./min 184 150 
Flex modulus, MPa 1860 2340 
Notched Izod, J/m 373 1170 
______________________________________