Process to form amorphous, crystallizable thermoplastic polymers

A method of forming an amorphous crystallizable thermoplastic polymer composition. The polymer composition has a modulus of rigidity which decreases to a minimum value with increasing temperature and then begins to increase. The process includes heating polymer to below a temperature at which crystal formation occurs and form the polymer. The polymer composition is then heated to a temperature at which crystal formation can occur and be annealed. This process is useful to make articles having a thickness of from 0.127 cm (0.050 inches) to 1.27 cm (0.50 inches) such as sheets and tubes of the amorphous polymer and then reforming and annealing them.

BACKGROUND OF THE INVENTION 
This invention is in the field of forming thermoplastic polymers, more 
particularly this invention relates to a process to form amorphous, 
crystallizable thermoplastic polymers 
Presently, crystallizable thermoplastic polymers are formed or shaped by 
heating them to their softening or melting temperature and exerting force 
to shape the polymeric material. The formed polymeric material 
crystallizes to some degree upon cooling from the temperature at which it 
was formed. The formed article is a crystallized thermoplastic article. 
Reshaping of the formed thermoplastic articles involves heating the 
polymer until it is sufficiently soft to be reshaped. This involves 
heating the polymer to a softening temperature close to or above the melt 
temperature of the polymer. During the heating of the polymer to the 
melting temperature, more crystals form making it necessary to continue to 
heat the polymer to the softening point before shaping can occur. 
U.S. Pat. No. 4,123,473 discloses a process to form a thin sheet of an 
amorphous blend of polycarbonate and polyester, at temperatures from 
99.degree. C. (210.degree. F.) to 138.degree. C. (280.degree. F.). It does 
not disclose forming the polycarbonate and polyester blend and then 
annealing it. Rather, the goal of this patent is to maintain the formed 
article amorphous so that it retains its dimensions and clarity. 
For the purposes of the present invention, thermoplastic polymers can be 
characterized by a T.sub.ch and a T.sub.cc. The T.sub.ch is the 
temperature upon heating the polymer at which crystal formation is first 
measurable. It is an indication of the lowest temperature at which 
crystals form upon cooling the polymer. The T.sub.cc is the temperature 
upon cooling the polymer from the melt at which crystal formation is first 
measurable. To form such a crystallizable thermoplastic polymer, the 
polymer has to be heated until it is soft enough to be shaped by suitable 
equipment. This involves heating the polymer to above the T.sub.ch during 
which crystals continue to form. The formation of crystals makes the 
polymer stiffer and more difficult to form requiring that the polymer be 
heated to a high enough temperature at which the stiffening effect of the 
crystals is destroyed. Upon heating it to such a formable temperature, the 
polymer can be formed. The polymer is then cooled and upon cooling below 
T.sub.cc crystals once again begin to form resulting in a crystallized 
formed polymer article. To reform the article once again requires heating 
to a temperature at which the crystals again disappear. 
In characterizing thermoplastic polymers there are polymers that have a 
very low T.sub.ch. These polymers crystallize at a very low temperature. 
There are polymers that have very high T.sub.cc. Once these polymers are 
cooled from the melt, they begin to crystallize immediately and rapidly. 
Further, with a minimal of heating the extent of crystallinity increases. 
Typical crystalline polymers include polycaprolactam, polyhexamethylene 
adipamide, and polybutylene terephthalate. There are thermoplastic 
polymers which remain amorphous or noncrystalline up to their melt 
temperatures. In a sense these polymers have a very low T.sub.cc or a very 
high T.sub.ch and slow crystallization rates. Upon cooling from the melt, 
crystals will not form even when cooling them to very low temperatures. 
Upon heating them, crystals will not form before the melt temperature is 
reached. One such amorphous polymer is polycarbonate. 
SUMMARY OF THE INVENTION 
The present invention is a method of forming an amorphous crystallizable 
thermoplastic polymer of the type having a T.sub.ch which is higher than 
the glass transition temperature, T.sub.g. The process comprises the steps 
of heating the polymer in its amorphous state to between the T.sub.g and 
the T.sub.ch. The polymer is amorphous during this heating and is 
formable. The next step is to form the polymer to the desired shape. Once 
the polymer is formed the polymer is heated to between the T.sub.ch and 
T.sub.cc for a sufficient time to form crystals. The polymer is then 
cooled. 
This method has the advantage of being able to form and reform the 
amorphous polymer at a low temperature between T.sub.g and T.sub.ch and 
then heat the polymer to above the T.sub.ch, but below the T.sub.cc, for 
sufficient time to form crystals. The crystallized polymer is stiff and 
retains its stiffness upon reheating. The polymer cannot be reformed until 
it is heated and the stiffening effect of the crystals is destroyed. It is 
required to heat the polymer close to or above the melting temperature to 
reform the polymer. 
The method of the present invention is particularly useful for the polymer 
class which can be characterized by how its stiffness changes with changes 
in temperature (T). Preferably, stiffness is measured by modulus of 
rigidity (G). The preferred class of polymers of the present invention has 
a modulus of rigidity which decreases to a G.sub.min at a T.sub.min and 
subsequently increases with increasing tempeature from G.sub.min to 
G.sub.cry. At G.sub.cry and T.sub.cry there is a decrease in the rate at 
which G changes with increasing temperature. The process of forming this 
class of polymers involves heating an amorphous polymer composition to 
below the T.sub.cry preferably between T.sub.soft and T.sub.cry, and more 
preferably between T.sub.soft and T.sub.min, and forming the polymer 
composition. The formed polymer composition is then heated to from 
T.sub.min to T.sub.cc for sufficient time to form crystals, i.e. annealed. 
In the present invention after the amorphous polymer is formed it can be 
cooled to ambient condition prior to annealing. This is particularly 
useful in forming a variety of shapes such as tubes made of amorphous 
polymer and then annealing them after they have been reshaped for specific 
applications. The polymer is annealed from T.sub.min to T.sub.cc and 
preferably from T.sub.cry to T.sub.cc. The shaping of the amorphous 
polymer takes place at a low temperature below T.sub.cry. Yet after the 
reformed polymer has been crystallized, it cannot be reformed again until 
the temperature is increased beyond that at which the crystals will start 
to decimate and the polymer composition will soften. 
Included in the polymers which can be formed by the process of the present 
invention are polyethylene terephthalate, polyamides in which the 
crystallinity is decreased i.e., a G.sub.min and T.sub.min is established 
and copolyamides which are amorphous and fit within the criteria of the 
modulus of rigidity discussed above. 
The present invention is particularly useful in forming amorphous, 
crystallizable articles having a thickness at some point in the article 
greater than 0.127 cm (0.050 inches). This is distinguishable from thin 
films which can be rapidly heated to destroy crystallinity and then 
shaped. The thicker articles do not require more rapid heat transfer while 
heated below T.sub.ch or T.sub.min for shaping while amorphous. A 
preferred amorphous, crystallizable article is tubing which can be 
reformed and then annealed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention relates to a process to form a class of polymers 
characterized by specific amorphous and crystalline forms dependent on 
their thermal histories. Preferably, these are polymers which can be 
characterized by their stiffness as a function of temperature. 
Following is a list of parameters, their definitions, and methods of their 
measurement which describe the class of polymers useful in the method of 
the present invention. T.sub.cc is the temperature of the first 
measurement of crystal appearance upon cooling of the polymer from the 
melt. T.sub.ch is a measurement of temperature at which crystallization is 
no longer occurring upon cooling. T.sub.ch is determined by measuring the 
temperatures at which crystals appear upon heating an amorphous piece of 
polymer. T.sub.cc and T.sub.ch can be measured using a Differential 
Scanning Calorimeter. Between 5 and 10 milligrams of sample is compression 
molded to form a film which is vacuum dried. To measure T.sub.cc the 
sample is placed in the Differential Scanning Calorimeter and heated to 
above the polymer melting point, usually at least 280.degree. C., where it 
is held for two minutes. The sample is then cooled at 10.degree. C. per 
minute. The sample used to measure T.sub.ch is prepared in the same manner 
as the sample used to measure T.sub.cc. After the sample film has been 
prepared, it is heated to above its melt temperature (280.degree. C.) and 
quenched. This assures an amorphous sample. The sample is then heated at 
10.degree. C. per minute. In measuring the T.sub.cc and the T.sub.ch, the 
sample is indicated to be brought to 280.degree. C. However, the sample 
can be brought to above the melting point of the polymer of interest. For 
example, in polyamides and copolyamides the temperature could be 
230.degree. C. to 240.degree. C. T.sub.cc and T.sub.ch are the 
temperatures at the maxima of the peaks of the curves measured on the 
Differential Scanning Calorimeter. 
For the purposes of the present invention a polymer is considered to be 
amorphous if there is insufficient crystallization to inhibit forming in a 
temperature range between T.sub.g and T.sub.ch. The polymer is plastic in 
that the polymer is capable of being deformed continuously and permanently 
in any direction without rupture. The amorphous crystallizable polymer can 
be made amorphous by quenching to below T.sub.ch from the melt. A polymer 
is considered crystalline if there is sufficient crystal formation to 
inhibit forming the polymer in the temperature range between T.sub.g and 
T.sub.ch, continuously and permanently in any direction without residual 
stresses remaining in the polymer which would cause the polymer to return 
to its original shape or cause the polymer to rupture. 
The present invention in terms of T.sub.cc, T.sub.ch, T.sub.g, and T.sub.m, 
the melting point, is a method for forming a crystallizable thermoplastic 
polymer selected from a group of polymers which has a T.sub.cc below its 
melting point, i.e., begins to crystallize before it melts, and has a 
T.sub.ch above the glass transition temperature, T.sub.g. The polymer can 
be a polymer composition or a polymer as long as the total composition 
meets the criteria of the T.sub.g, T.sub.cc, T.sub.ch, T.sub.m. An 
amorphous crystalline polymer is heated to between the T.sub.g and 
T.sub.ch. The heated polymer is formed in its amorphous state. The polymer 
can optionally be cooled or continued to be heated. The polymer is heated 
to between the T.sub.ch and the T.sub.cc for a sufficient time to form 
crystals. Once the polymer composition is crystallized, it will no longer 
be formable between the T.sub.g and the T.sub.ch. In order to reform this 
thermoplastic polymer, it must then be heated to close to or above the 
T.sub.m. 
A particular class of the polymer compositions of the present invention is 
defined in terms of the stiffness of the polymer composition as it varies 
with temperature. A preferred way to measure the stiffness is by use of G, 
the modulus of rigidity. The modulus of rigidity is measured according to 
ASTM Test No. D1043-72, hereby incorporated by reference. In the preferred 
class of polymers the modulus of rigidity decreases with temperature to a 
minimum value G.sub.min at T.sub.min. Continued increase of the 
temperature causes the modulus of rigidity to increase from the minimum up 
to a G.sub.cry at T.sub.cry. At the G.sub.cry there is a decrease in the 
rate at which the G changes with increasing temperature. 
Polymers which can be formed by the method of the present invention have 
the general performance outlined on FIG. 1. FIG. 1 is a general graph of 
the log of the modulus of rigidity G in Pascals (Pa) versus the 
temperature T in degrees Centigrade. On FIG. 1 there are three curves. 
Curve A indicates the behavior of the polymers of the class useful in the 
present invention. Curve B indicates the behavior of polymers which are 
crystalline, and curve C indicates the behavior of polymers which are 
amorphous. It is noted that in curve C for amorphous polymers, there is a 
decrease in slope comparable to the decrease in curve A at G.sub.soft, 
T.sub.soft. However, there is no T.sub.min, G.sub.min and the amorphous 
polymer melts before bottoming out and beginning to increase in slope 
toward a G.sub.cry, T.sub.cry. Crystalline polymers, which behave in the 
manner of curve B, have a gradually decreasing modulus of stiffness. There 
is no trough, and the stiffness decreases gradually until the polymer 
finally melts. Polymers of the class of the present invention start to 
gradually decrease in stiffness modulus with increasing temperature. Upon 
reaching a G.sub.soft at a T.sub.soft, the rate of decrease of modulus 
increases. This is comparable to the behavior of amorphous polymers as 
described by curve C. However, the polymers useful in the process in the 
present invention continue to decrease only until they reach a G.sub.min 
at a T.sub.min. At this point the polymers begin to crystallize, and the 
modulus of stiffness begins to increase with increasing temperature, 
thereby forming a trough in the curve. At a point G.sub.cry and T.sub.cry 
sufficient crystallization occurs so that the polymer begins to behave in 
the manner of a crystalline polymer as defined by curve B. The rate of 
change of G with increasing T slows down. 
In the process of the present invention an amorphous, crystallizable 
polymer is heated to below T.sub.cry and has a modulus of stiffness of 
below G.sub.cry. The polymer is formable between T.sub.soft and T.sub.cry. 
This includes the polymer being formed between T.sub.soft and T.sub.min. 
When forming the polymer above T.sub.min, between T.sub.min and T.sub.cry, 
some crystallization occurs. This can be minimized by immediate quenching 
to below T.sub.min so that the polymer is reformable. Upon forming the 
polymer composition, the polymer can be heated to above T.sub.min, 
preferably from T.sub.min to T.sub.cc, for a sufficient time to form 
crystals so that the polymer behaves in the manner of a crystalline 
polymer of the type identified by curve B. Alternately, the polymer can be 
formed in this formable range below G.sub.cry, T.sub.cry and cooled to 
room temperature. The polymer can then be heated to below T.sub.cry and 
reformed and then subsequently heated to above T.sub.min, preferably above 
T.sub.cry and below T.sub.cc, in an annealing step for a sufficient time 
to form crystals. Once the polymer has been annealed or crystallized, it 
cannot be reformed unless it is heated to a sufficient temperature to 
dissipate the stiffening effect of the crystals or melt them. Generally, 
this temperature is at or close to the melting point of the polymer. 
Therefore the present invention provides a method for forming a 
thermoplastic polymer and reforming it at below the melting point of the 
polymer. This formed or reformed article can then be heated or annealed 
for a sufficient time to cause crystallization resulting in a stiffness or 
modulus of the polymer which will not reform at temperatures below 
T.sub.cry. It is recognized that crystal formation can occur by heating to 
below T.sub.cry, i.e. between T.sub.min and T.sub.cry, for sufficient time 
so that the G.sub.cry is reached. 
In the annealing step the polymer is heated between T.sub.min and T.sub.cc 
for a sufficient time to form sufficient crystals so that it cannot be 
reformed at a temperature below T.sub.cry. The time depends on the 
temperature. The higher the temperature, the shorter the heating time 
necessary. FIG. 2 shows the behavior of a terpolymer of caprolactam, 
terephthalic acid and bis(p-aminocyclohexyl)methane as discussed in 
Example 1. An amorphous sample begins to crystallize at about 75.degree. 
C. A sample of this terpolymer anneals, i.e. when it is heated for a 
sufficient time so that it crystallizes sufficiently, so that the sample 
can no longer be reformed at a temperature below T.sub.cry, about 
95.degree. C. The time to anneal can vary from about one hour at 
75.degree. C. to from about 1 to 10 minutes between 90.degree. C. and 
120.degree. C. The heat transfer characteristics of the polymer affect the 
rate of crystallization. A thicker sample takes a longer time to 
crystallize. 
For the purposes of the present invention as indicated above, the procedure 
to be followed to identify the class of polymers is that described in ASTM 
Test No. D1043-72. Analogous methods of measuring stiffness, such as the 
use of the Vibron Direct Reading Dynamic Viscoelastometer, can be used to 
identify the polymers useful in the method of the present invention. As 
indicated in the examples, this alternate method has been used. This 
method is described in Vibron Direct Reading Dynamic Viscoelastometer 
Model DDV-II, Instruction Manual 17, October, 1967, published by the Toyo 
Measuring Instruments Company, Limited, Headquarters in 104, 1-CHOME 
CHOFUMINEMACHI, OTA-KU, Tokyo, Japan, hereby incorporated by reference. 
Polymers useful in the present invention are those which have the behavior 
shown on curve A of FIG. 1. Such polymers include a variety of 
copolyamides, as well as polyethylene terephthalate. An example of an 
amorphous polymer not following curve A, but following curve C, is 
polycarbonate. An example of a crystalline polymer, not following curve A 
but following curve B, is polyepsiloncaprolactam. For the purposes of the 
present invention the term polymer includes the polymer, as well as the 
polymer and additional additives which can cause the polymer to behave in 
the manner described by curve A of FIG. 1. For example 
polyepsiloncaprolactam containing between 0.1 and 10% of a lithium salt, 
preferably lithium chloride has a behavior which falls along curve A of 
FIG. 1. Additionally copolyamides, such as the terpolymer of caprolactam, 
terephthalic acid and bis(p-aminocyclohexyl)methane has been found to be a 
curve A type polymer and is particularly useful and preferred in the 
process of the present invention. The most preferred terpolymer contains 
90 mol percent of caprolactam, 5 mol percent of terephthalic acid and 5 
mol percent of bis(p-aminocyclohexyl)methane. Other polymers following 
curve A of FIG. 1 and useful in the method of the present invention 
include copolymers of caprolactam, terephthalic acid and 1,3 or 
1,4-cyclohexane bis(methyl amine) with terephthalic acid or isothalic 
acid. Also useful in the present invention is the terpolymer of 
caprolactam, hexamethylene diamine and azelaic acid. Another polymer found 
useful in the present invention is the copolymer of caprolactam and 
aminododecanoic acid. 
Included in the polymers useful in the present invention are those 
disclosed in U.S. Pat. Ser. No. 336,976, filed Jan. 4, 1982. These 
polymers are amorphous and generally follow curve A of FIG. 1. However, 
copolymers which remain amorphous and do not exhibit the trough as shown 
in FIG. 1 are not useful since these cannot be annealed. An example of 
such a copolymer is the copolymer of terephthalic acid and an alkyl 
substituted hexamethylene diamine having the repeating unit 
##STR1## 
The polymer compositions useful in the present invention are initially 
amorphous. They do not have sufficient crystallinity to inhibit the 
formation of the trough in the curve of FIG. 1. That is, the polymers can 
be heated up to T.sub.cry and exhibit a G.sub.min. Another polymer useful 
in the present invention is polyethylene terephthalate. Amorphous 
polyethylene terephthalate behaves in the manner of curve A of FIG. 1. 
The polymer composition of the present invention can include polymer 
blends, and can include various other additives such as stabilizers and 
inhibitors of oxidative, thermal and ultraviolet light degradation, 
lubricants, plasticizers, mole-release agents, crosslinking agents, 
colorants, including dyes and pigments, impact modifiers and additives 
such as fibers and particulate fillers and reinforcing agents which are 
not deleterious to physical properties or promote premature 
crystallization. 
The process of the present invention is useful for forming thick articles, 
as well as thin articles made from amorphous crystallizable polymers. For 
example articles thicker than 0.127 cm (0.050 inches) thick which could 
not immediately be heated and cooled due to heat transfer limitations 
could be formed by the process of the present invention. Articles 
particularly preferred include tubing and sheets both having thicknesses 
of from 0.127 cm (0.050 inches) to 1.27 cm (0.500 inches) preferably 
0.127 cm (0.050 inches) to 0.635 cm (0.250 inches) and more preferably 
0.127 cm (0.050 inches) to 0.318 cm (0.125 inches). Tubing diameter with 
the indicated thicknesses as wall thicknesses is limited only by 
production (i.e. extrusion) equipment limitations. The articles are first 
formed into an initial shape, i.e. a tube or sheet. The article can be 
reformed according to the process of the present invention, and annealed. 
Several examples are set forth below to illustrate the nature of the 
invention and the manner of carrying it out. However, the invention should 
not be considered as being limited to the details thereof. All parts are 
percents by weight unless otherwise indicated. 
EXAMPLES 1-4 
In Examples 1-4 polymer compositions were made based on a copolyamide 
containing 90 mol percent caprolactam, 5 mol percent terephthalic acid, 
and 5 mol percent of bis(p-aminocyclohexyl)methane. In Example 1 this 
polymer alone was tested according to ASTM D1043-72 using a Clash-Berg 
torsion pendulum. The results are shown on FIG. 2 as a graph of the log of 
the modulus of rigidity G (Pa) vs. temperature T (.degree.C.). The torsion 
pendulum test was conducted while raising the temperature 1.degree. C. per 
minute. The initial copolyamide was amorphous. The polymer was soft and 
moldable between 60.degree. C. and about 90.degree. C., more preferably 
from 60.degree.-80.degree. C. 
The polymer was compression molded into discs 0.3175 cm (1/8 inch) thick 
and 5.08 cm (2 inches) in diameter in a hydraulic press set at 260.degree. 
C. The discs were quenched in cold tap water at about 10.degree. C. 
Tensile bars and flex bars were injection molded at a polymer temperature 
of 230.degree. C. and a mold temperature of 32.degree. C. The tensile bars 
were (ASTM Type 1 dog bones) 0.3175 cm (1/8 inch) thick, 1.27 cm (1/2 
inch) wide at the neck and 2.54 cm (1 inch) wide at the widest portion and 
19.3 cm (7.6 inches) long. The flex bars were 0.3175 cm (1/8 inch) thick 
by 1.27 cm (1/2 inch) wide and 12.7 cm (5 inches long), and 0.635 cm (1/4 
inch) thick by 1.27 cm (1/2 inch) wide and 12.7 cm (5 inches) long. Tubing 
having an outside diameter of 2.54 cm (1 inch) and an inside diameter of 
1.9 cm (3/4 inch) was extruded at 230.degree. C. using a 5.08 cm (2 inch) 
NRM single screw extruder. Each of these articles was quenched in cold tap 
water at about 10.degree. C. They were then put under hot tap water at 
about 70.degree. C. and became soft and pliable. They could be formed by 
hand. The molded articles were annealed at 105.degree. C. for 40 minutes. 
The annealed samples were tested according to ASTM D1043-72 in the same 
manner as the amorphous sample. The result is shown as the "Annealed" 
curve on FIG. 2. 
The deformation of a sample under a load can be measured as the DTUL, the 
distortion temperature under load according to ASTM Test No. D648. Under 
this procedure a 0.635 cm (1/4 inch) by 1.27 cm (1/2 inch) by 12.7 cm (5 
inch) bar is subjected to a load of 455 kPa (66 psi) or 1820 kPa (264 psi) 
applied to the center and the temperature is raised at 2.degree. 
C./minute. The temperature at a specified deformation is measured. The 
DTUL at 455 kPa (66 psi) for the amorphous material increased from 
69.degree. C to about 113.degree. C. after 4 minutes, and then gradually 
increased to about 115.degree. C. after being annealed for 15 minutes. 
Other physical properties measured included tensile strength in Pa (psi), 
as measured according to ASTM Test No. D638, flexural strength and modulus 
in Pa (psi) as measured according to ASTM Test No. D790, unnotched and 
notched Izod impact results, Nm/m (foot pounds/inch) measured according to 
ASTM Test No. D256. The T.sub.cc and T.sub.ch were measured according to 
the procedure discussed above. The Drop Weight Impact was measured using 
the procedure of ASTM D2444 with Gardner impact apparatus for measurement. 
The results are summarized in Table I below. 
EXAMPLE 2 
Example 1 was reproduced except that the copolymer composition contained 7 
percent by weight of ethylene acrylic acid and 7 percent by weight of 
ethylene ethylacrylate. Here again, the composition containing the 
amorphous copolyamide was found to behave in the manner of curve A of FIG. 
1. This composition was then annealed at 120.degree. C. for 15 minutes in 
order to crystallize it. The results are summarized in Table I. 
TABLE I 
______________________________________ 
Ex. 1 Ex. 2 
As An- As An- 
Molded nealed Molded nealed 
______________________________________ 
Copolyamide (%) 
100 100 86 86 
EAA (%) 7 7 
EEA (%) 7 7 
Tensile Str., MPa (psi) 
81.4 81.4 59.3 66.9 
(11800) (11800) (8600) (9700) 
Flex. Str., MPa (psi) 
103.4 119.3 70.3 81.4 
(15000) (17300) (10200) 
(11800) 
Flex Mod., MPa (psi) 
248.2 248.2 186.2 193.05 
(3.6 .times. 
(3.6 .times. 
(2.7 .times. 
(2.8 .times. 
10.sup.5) 
10.sup.5) 
10.sup.5) 
10.sup.5) 
Drop Wt, J. (ft. lbs.) 
9.5 241 
(7) (177) 
No Notch Izod, Nm/m 
32.02 26.69 
(ft. lbs./in.) (60) (50) 
Notch Izod, Nm/m 
58.7 53.4 
(ft. lbs./in.) (1.1) (1.0) 
DTUL, 455 kPa (66 psi) 
55 115 
(.degree.C.) 
DTUL, 1820 kPa (264 psi) 
56 
(.degree.C.) 
Appearance Clear Trans- White White 
lucent 
amorp. cryst. amorp. cryst. 
T.sub.ch (.degree.C.) 
110 
T.sub.cc (.degree.C.) 
135 
T.sub.g (.degree.C.) 
68 
______________________________________ 
EXAMPLES 3 AND 4 
In Examples 3 and 4, 15 percent and 30 percent by weight of short 
fiberglass filler was added to the amorphous copolymer used in Example 1. 
The polymer composition containing the glass filler behaved in a manner 
similar to the amorphous curve shown on FIG. 2. This material could be 
molded and remolded before annealing. After annealing, the composition 
behaved in a similar manner as the composition which followed the annealed 
curve of FIG. 2. The physical properties measured for the compositions in 
Examples 3.gtoreq.4 are summarized on Table II below. 
TABLE II 
______________________________________ 
Ex. 3 Ex. 4 
As As 
Molded Molded 
______________________________________ 
Copolyamide (%) 70 85 
Glass (%) 30 15 
Tensile Str., psi 131.0 95.8 
(19000) (13900) 
Flex Str., psi 188.2 141.3 
(27300) (20500) 
Flex Mod. psi 668.8 399.9 
(9.7 .times. 10.sup.5) 
(5.8 .times. 10.sup.5) 
No Notch Izod ft. lbs./in. 
976.8 555 
(18.3) (10.4) 
DTUL, 455 KPa (66 psi) (.degree.C.) 
61 60 
DTUL, 1820 KPa (264 psi) (.degree.C.) 
58 60 
______________________________________ 
The amorphous crystallizable polymer compositions of Examples 1-4 could all 
be formed upon heating the polymer to between 60.degree. and 70.degree. 
C., and all had the characteristics of the amorphous curve of FIG. 2. The 
polymers were then cooled. The cooled polymers could be reheated to the 
temperatures of 60.degree.-80.degree. C. and reformed. The polymers were 
then heated to above about 100.degree.-105.degree. C. for sufficient time 
to be annealed, and as indicated in Example 1, the annealing took place 
for 40 minutes at 105.degree. and in Example 2 the annealing took place 
for 15 minutes at 120.degree. C. Once the part was annealed, it could not 
be reformed at 60.degree.-80.degree. C., but the polymer had to be heated 
to almost the melt temperature before it could be reshaped. 
EXAMPLE 5 
An amorphous polyethylene terephthalate sample was heated according to the 
referenced Vibron procedure to measure the complex tensile modulus, E 
(Pa). This modulus measures stiffness in a similar manner as G, the 
modulus of rigidity measured by the Clash-Berg torsion pendulum. The 
results are shown on FIG. 3 as a plot of log of the complex tensile 
modulus E versus the temperature T in .degree.C. The amorphous 
polyethylene terephthalate had the characteristic curve of polymers useful 
in the process of the present invention as indicated on curve A on FIG. 1. 
The polymer was annealed for 3-4 minutes at 180.degree. C. The annealed or 
crystalline polyethylene terephthalate was retested using the Vibron 
method. The result is shown as the PET, crystalline curve on FIG. 3. By 
way of comparison, the Vibron method was used to test crystalline 
polybutylene terephthalate, as well as amorphous polycarbonate. The 
results are also shown on FIG. 3. Polybutylene terephthalate and 
polycarbonate could not be used in the process of the present invention, 
while amorphous polyethylene terephthalate has the characteristic curve 
required. 
While exemplary embodiments of the invention have been described, the true 
scope of the invention is to be determined from the following claims: