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POLY(TRIMETHYLENE TEREPHTHALATE)

Introduction

Poly(trimethylene terephthalate) (PTT, also abbreviated as 3GT) is an aromatic
polyester made by the melt polycondensation of 1,3-propanediol (PDO) with ei-
ther terephthalic acid (TPA) or dimethyl terephthalate (DMT). Although available
commercially only since 1998, it was one of the three polyesters first synthesized
by Whinfield and Dickson (1) in 1941. Two of which, the so-called even-numbered
poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) for the
number of methylene units in their chemical structures, are well-established high
volume polymers. However, the odd-numbered PTT remained an obscure polymer.
It was never commercialized until recently because PDO was very expensive and
was available only as a small volume fine chemical.

In the early 1970s, there were interests to commercialize PTT (2–4); however,

they were short-lived. Despite making significant progress in lowering PDO man-
ufacturing cost, the economics was still not good enough. Interest was revived in
the late 1980s when Shell Chemical Co. (5) and Degussa (6) had breakthroughs in
PDO manufacturing technologies. Shell began selling PTT in 1998 and completed
building a new PDO plant (7). It was followed by DuPont announcing the building
of a PTT plant by first using PDO acquired from Degussa, and later using PDO
from bioengineering route (currently under development) when it becomes avail-
able (8). More than half a century after it was first synthesized, PTT finally joined
PET and PBT and became a commercial reality. PTT from Shell is trademarked
as Corterra polymer and DuPont’s trademark is Sorona 3GT.

Encyclopedia of Polymer Science and Technology. Copyright John Wiley & Sons, Inc. All rights reserved.

Vol. 3

POLY(TRIMETHYLENE TEREPHTHALATE)

545

1,3-Propanediol Monomer

1,3-Propanediol [504-63-2], also called trimethylene glycol, is a colorless, clear
liquid with a boiling point of 214

◦

C. The traditional synthesis route, practiced by

Degussa, is to hydrate acrolein (9) under pressure with an acid catalyst such as
acidic ion-exchange resin into 3-hydroxypropanal (3-HPA). This intermediate is
not isolated. The aqueous solution is hydrogenated into PDO using Raney nickel
catalyst. A new commercial route developed by Shell uses ethylene oxide (EO) as
the starting raw material. Ethylene oxide is first hydroformylated into 3-HPA,
using a combination of CO and H

2

synthesis gas with cobalt catalyst (5). 3-HPA

is concentrated and hydrogenated into PDO. Commercial quantities of PDO are
now available from both processes. A third route with the potential of further low-
ering PDO cost is by enzymatic fermentation (10,11) of glycerol and alcohol. This
bio-route is under active development by DuPont and Genencore International.
With advances in biogenetic engineering, new strains of engineered bacteria were
reported to improve yield and selectivity that can be scaled up for commercial
production.

Polymerization

PTT is melt-polymerized by either the transesterification of PDO with DMT or
by the direct esterification of PDO with TPA. The process is similar to the poly-
merization of PET but with several important differences. Since the reactivity of
PDO is much lower than that of ethylene glycol, “hot” catalysts such as titanium
butoxide (12) and dibutyl tin oxide (13), normally too fast for PET, are used to
polymerize PTT. Melt polymerization is carried out between 250 and 275

◦

C, about

40

◦

C lower than that used for PET. PTT has different polymerization side reaction

products. Instead of cyclic trimers, PTT produces cyclic dimers. It also gives off
acrolein and allyl alcohol instead of acetaldehyde gaseous by-products. Acrolein
requires special handling and disposal.

Direct esterification of PDO with TPA is the preferred commercial route to

polymerize PTT because it is more economical than using DMT. Figure 1 shows
the reaction scheme. Because TPA has a melting point

> 300

◦

C and has poor sol-

ubility in PDO, esterification is carried out in the presence of a “heel” and under a
pressure of 70–150 kPa at 250–270

◦

C for 100–140 min. Heel is an oligomeric PTT

melt with a degree of polymerization (DP) of 3–7 purposely left in the reaction
vessel from a previous reaction to act as a reaction medium and to increase TPA
solubility. The esterification step is self-catalyzed by TPA. After reaching a DP of
about 3–7, 40–50% of the oligomers is transferred to the polymerization vessel.
Titanium butoxide or dibutyl tin oxide catalyst (50–150 ppm) is added to initiate
polymerization at 260–275

◦

C. Vacuum (

<0.15 kPa) is applied to remove the con-

densed water until the polymer reaches an intrinsic viscosity (IV) of 0.7–0.9 dL/g.

To obtain higher molecular weight PTT with IV

> 1.0 dL/g, melt-polymerized

chips are further solid-stated (14,15) at 180–210

◦

C under nitrogen to prevent poly-

mer yellowing from prolonged melt polymerization. Solid-stating also helps driv-
ing off residual gaseous by-products in the polymer chips; however, the molecular
weight distribution is broadened from 2 to about 2.5.

546

POLY(TRIMETHYLENE TEREPHTHALATE)

Vol. 3

Fig. 1.

PTT polymerization by direct esterification of TPA with PDO. Gauche conformation

of PTT’s methylene units is indicated by g.

Side Reactions and Thermal Degradation

PTT melt undergoes several side reactions during polymerization and melt pro-
cessing. It has been proposed that PTT undergoes thermal degradation similar
to PET via McClafferty rearrangement of the ester moiety (16,17). The carbonyl
group abstracts a

β-methylene hydrogen through a six-membered cyclic transi-

tion state, and this event is followed by chain scission giving terminal carboxyl
and vinyl end groups in the fragmented chains. Further scission of the vinyl end
gives allyl alcohol and its oxidative product acrolein. Under inert atmosphere,
PTT has similar thermogravimetric weight loss profile as PET (18) with only one
main decomposition step. Degradation in air was, however, different and involved
two mechanisms. At about 300

◦

C, degradation was decomposition-controlled. At

a higher temperature, the rate increased and degradation changed to diffusion-
controlled.

Cyclic oligomer is generated by chain backbiting similar to that in PET. In-

stead of cyclic trimer, PTT forms cyclic dimer with a melting point of 254

◦

C. During

polymerization, some PDO is dimerized into dipropylene ether glycol (DPG) and
are incorporated in PTT as copolymer. Presence of DPG moiety lowers the poly-
mer’s melting point and affects the fiber’s dye uptake. These side reactions could
be suppressed to various extents by adding antioxidants and phosphites, using
high purity PDO, and controlling the polymerization conditions (19).

Thermal Properties

PTT is a semicrystalline polymer with a glass-transition temperature T

g

of 45

◦

C

and a melting point T

m

of 228

◦

C, both measured by a differential scanning

calorimeter (dsc). The T

g

of PTT is dependent on the polymer’s crystallinity. It

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POLY(TRIMETHYLENE TEREPHTHALATE)

547

Table 1. Thermal Properties of PTT

Property

Value

Reference

Melting point,

◦

C

228

–

Equilibrium melting point,

◦

C

244, 248

21,22

Heat of fusion

H

f

, kJ/mol

30

±2

23

Fully amorphous heat capacity, J/(K

·mol)

94

23

Crystallization half-time @ 180

◦

C, min

2.4

24

Cold crystallization temperature,

◦

C

65

–

Glass-transition temperature,

◦

C

45

–

Thermal diffusivity, m

2

/s

@ 25

◦

C

1.36

× 10

− 7

25

@ 140

◦

C

0.99

× 10

− 7

25

remains at 45

◦

C up to about 30% crystallinity, and increases rapidly to about

70

◦

C when crystallinity reaches 50% (20). The heat of fusion

H

f

for a 100% crys-

talline PTT is 30

± 2 kJ/mol. Other thermal properties are shown in Table 1. When

PTT was rapidly quenched from the melt, the dsc heating scan showed a cold crys-
tallization exotherm at about 65

◦

C; however, a slowly cooled PTT does not cold

crystallize. Therefore, the crystalline morphology is dependent on the melt quench
history, and affects the drawing behavior of the polymer. The reversible and ir-
reversible heat capacities were measured using adiabatic calorimetry, dsc, and
temperature-modulated dsc (23,26). The measured heat capacities for both solid
state and liquid state PTT agreed well with values calculated from the Tasarov
equation based on polymer chain skeletal vibration contributions (Fig. 2).

Temperature, K

Heat Capacity

, J/(K

ⴢmol)

C

p

L

(Cal)

C

p

S

(Cal)

⌬C

p

(100%)

⫽ 88.8 J/(Kⴢmol)

T

g

⫽ 331 K

T

f

⫽ 489 K

W

c

⫽ 51%

⌬H

f

⫽ 15.3

kJ/mol

0

0

200

400

600

800

100

200

300

400

500

600

Fig. 2.

Experimental and calculated heat capacities of solid and liquid PTT. –

•– C

p

(Exp);

–

•– Standard DSC;——C

p

L

(Exp);

. . .. . . C

p

L

(Cal). From Ref. 23, Copyright c

1998 by John

Wiley and Sons, Inc. Reprinted by permission of John Wiley & Sons, Inc.

548

POLY(TRIMETHYLENE TEREPHTHALATE)

Vol. 3

Crystallization Kinetics

A comparison of the isothermal crystallization kinetics of PET, PTT, and PBT using
a dsc showed that PTT has a crystallization rate in between those of PET and PBT
(24). The Avrami rate constant K was of the order of 10

− 3

–10

− 2

min

− n

when

crystallized at 175–195

◦

C. It is about an order of magnitude higher than PET but

an order of magnitude lower than PBT when they were compared with the same
degree of undercooling from the melt. PTT has a spherulitic growth rate of 117–4.7
µm/min, and it requires 4.8 kcal/mol of work for lamellae chain folding (22). On
the basis of secondary nucleation analysis, a multiple nucleation crystallization
mechanism transitioned from regime II to regime III at around 194

◦

C was reported

(22). Since the work of chain folding and the nucleation mechanism transition
temperature were between literature values of PET and PBT, the three polyester
crystallization rates rank in the same order.

A rapidly quenched PTT cold crystallizes when it is heated to above its T

g

. It

was found that PTT cold crystallized at a much faster rate than PET by following
the increase in PTT crystalline band at 1220 cm

− 1

using rapid scanning Raman

spectroscopy (27). At 71

◦

C, PTT crystallized and reached 80% of its equilibrium

crystallinity in

<1 min whereas PET did not cold crystallize at all.

Molecular Weights

As a norm, molecular weight M of a polyester is given by its intrinsic viscosity
(IV), also called limiting viscosity number [

η]; M and [η] are related to each other

through the Mark–Houwink equation

[

η] = KM

α

(1)

where K and

α are constants unique to the solvent and temperature used in

measuring IV. Because of the fast crystallization rate, PTT chips have higher
crystallinity than PET and are much more difficult to dissolve. A stronger sol-
vent such as hexafluoroisopropyl alcohal (HFIPA) is used to dissolve PTT at room
temperature. However, by heating to 110

◦

C and taking care to ensure complete

dissolution, mixtures of tetrachloroethane/phenol, typically used for PET, have
been successfully used for PTT. Table 2 shows PTT’s Mark–Houwink constants
for various solvents (28,29), and the methods of molecular weight measurement.

In practice, IV is often measured using the simplified single-point method

to save time. Simplified equations (30–33) gave good estimations of IV compared
to the more rigorous Huggins or Kraemer plots to within

±3% when the solution

concentration is kept at

<0.005 g/dL (28).

Crystal Structure

Like PET and PBT, PTT crystallizes into the triclinic crystal structure (34–
37). Unit cell dimensions obtained from wide-angle x-ray diffraction (waxd) are
a

=0.459, b=0.621, c=1.831 nm, α = 98

◦

,

β=90

◦

,

γ =112

◦

(34). The c-axis contains

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POLY(TRIMETHYLENE TEREPHTHALATE)

549

Table 2. PTT Mark–Houwink Constants

Molecular weight

a

Temperature,

determination

a

K, 10

4

Solvent

◦

C

method

a

dL/g

α

Reference

HFIPA

35

sals

5.51

0.71

24

HFIPA

35

Hydroxyl group

10.0

0.70

–

60/40 Tetrachloroethane/

30

sals

5.36

0.69

24

phenol

50/50 Tetrachloroethane/

20

sals

8.2

0.63

25

phenol

a

sals

= small-angle light scattering.

c

c

b

a

(a)

(b)

Fig. 3.

Crystal structure of PTT viewed in the (a) bc-plane and (b) ac-plane showing the

zizzag chain from the gauche–gauche conformation of the methylene units. Reprinted from
Ref. 34, Copyright 1979, with permission from Elsevier Science.

two PTT repeating units with the methylene groups arranged in a gauche–gauche
conformation. When viewed in the ac- and bc-plane, the chains are arranged in a
highly contracted zizzag manner compared to that of PBT and PET (Fig. 3). There
are disagreements in the reported crystal densities. Densities based on waxd crys-
tal structures are much higher than those obtained by electron diffractions (38).

550

POLY(TRIMETHYLENE TEREPHTHALATE)

Vol. 3

Measurements of the densities of a series of 19 PTT samples with dsc crystallini-
ties from 14 to 35% gave an extrapolated crystal density of 1441 kg/m

3

, in closer

agreement to the waxd unit cell density (39). Until more work was done, the au-
thor’s research group used 1432 kg/m

3

for crystallinity measurement, based on

crystal structure parameters (34). Using a group contribution method, an amor-
phous density of 1295 kg/m

3

was calculated (25) in good agreement with the ex-

trapolated value obtained by Ziabicki (39).

PTT waxd crystal orientation function f

c

can be measured from the azimuthal

scan of 010 reflection. The Herman orientation function equation using this re-
flection has been given by (38), and is based on Wilchinsky’s treatment of uniaxial
orientation:

f

c

= 1 − 3cos

2

φ

010

,Z

(2)

where

cos

2

φ

010

,Z

is the average cosine angle of the normal of (010) plane made

with the draw direction Z.

Mechanical Properties

Table 3 compares properties of PTT, PET, and PBT (40). They were measured on
injection-molded samples using ASTM test methods. Tensile strength, flexural
modulus, and notched Izod impact of PTT fall in between those of PET and PBT.
All three polymers have similar electrical properties except for PET which has
lower volume resistivity. The lower moisture absorptions of PTT and PBT are due
to the high crystallinities from fast crystallization.

Dynamic Mechanical Properties.

The PTT dynamic mechanical relax-

ation spectrum shows three viscoelastic relaxations (41).

α-Relaxation occurs at

−70

◦

C and is the glass-transition temperature. T

g

obtained by dynamic mechan-

ical methods is usually higher than that from a dsc, and is frequency dependent.

Table 3. Comparison of PTT, PET, and PBT Properties

Property

PET

PTT

PBT

Tensile strength, MPa

a

72.5

67.6

56.5

Flexural modulus, GPa

b

3.11

2.76

2.34

Heat distortion temperature @ 1.8 MPa,

◦

C

65

59

54

Notched Izod impact, J/m

c

37

48

53

Specific gravity, kg/m

3

1400

1350

1340

Mold shrinkage, m/m

0.03

0.02

0.02

Dielectric strength, V/

µm

0.407

0.393

0.296

Dielectric constant at 1 MHz

3.0

3.0

3.1

Dissipation factor at 1 MHz

0.02

0.015

0.02

Volume resistivity, 10

− 16

·cm

0.1

1.0

1.0

Moisture absorption, 14 days, %

0.49

0.15

0.2

a

To convert MPa to psi, multiply by 145.

b

To convert GPa to psi, multiply by 145,000.

c

To convert J/m to ft

·lbf/in., divide by 53.38.

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POLY(TRIMETHYLENE TEREPHTHALATE)

551

α-Relaxation as high as 91

◦

C has been reported (42). There are two subzero re-

laxations.

β-Relaxation occurs at about −70

◦

C. It originated from the amorphous

phase (43), and has been attributed to the reorientation of the hydroxyl groups
and local motions of the carboxyl groups.

γ -Relaxation occurs at about −105

◦

C and

overlaps with the

β-relaxation peak as a shoulder. This relaxation comes from the

cooperative movement of the methylene segments containing at least three con-
secutive methylene units (44), and is therefore a low temperature motion of the
trimethylene glycol portion of the polymer.

Elastic Recovery.

The fiber industry has long been aware of PTT hav-

ing the best tensile elastic recovery and resiliency among the three aromatic
polyesters (45). This property is very desirable for fiber applications such as in
carpets and textile apparels. The driving force for PTT’s good elastic recovery
comes from the response of its molecular chain to the applied strain.

It has been shown (46) that PTT has a very low theoretical crystal modu-

lus, 2.59 GPa (375, 550 psi), compared to 107 GPa (1.55

× 10

7

psi) of PET (47)

because of PTT’s highly contracted helical-like conformation, whereas PET chain
is fully extended with trans conformation. When a PTT fiber is stretched in situ
in a waxd, the fiber period, measured from the Bragg d-spacing, increases imme-
diately and is proportional to the applied strain up to 4% strain before deviating
from affine deformation (48). Up to this critical strain the crystal deformation is
reversible. The response of microscopic crystalline chains to macroscopic defor-
mation explains why PTT has the best elastic recovery among the three aromatic
polyesters. Further, PTT’s elastic recovery and permanent set are nearly the same
as nylon-6,6 up to 30% strain (25).

Melt Rheology.

Figure 4 shows the melt viscosity as a function of shear

rate for a 0.92 dL/g IV fiber grade PTT from 245 to 275

◦

C (49). At 265

◦

C, the

melt viscosity profile is nearly the same as that of PET at a typical processing
temperature of 290

◦

C. At high shear rates of 10

3

–10

4

s

− 1

, found in injection

Shear Rate, s

−1

Viscosity

, P

a

. s

245

°C

255

°C

265

°C

275

°C

5

5

10

2

10

0

10

1

10

2

10

3

10

4

Fig. 4.

Fiber grade 0.92 dL/g IV PTT capillary rheometer melt viscosity as a function of

shear rate from 245 to 275

◦

C. To convert Pa

· s to P, multiply by 10.

552

POLY(TRIMETHYLENE TEREPHTHALATE)

Vol. 3

molding and fiber spinning, the melt shear thins. It can be approximated as a
power law fluid. However, PTT is more sensitive to shear thinning than PET with
a non-Newtonian power law index n of 0.64 compared to 0.79 of PET (26).

Processing and Applications

Most of the developments to date have focused on textile and carpet fiber appli-
cations because PTT has a combination of several properties particularly suited
for these applications. Table 4 compares PTT fiber properties with those of PET,
nylon-6, and nylon-6,6 (20), (50), (51).

PTT fibers and yarns have bulk, resiliency, stretch-recovery, softness, hand,

and drape similar to nylons and are much better than PET. As a polyester, it is
inherently resistant to most stains that are acidic in nature because it does not
have dye sites. It also has a lower static propensity. It is dyed with disperse dyes,
but at a lower temperature than PET because of a lower T

g

. The combinations

of these properties are attractive to carpet and textile manufacturers for some
applications where PTT could replace nylon or PET. It also offers the potential of
creating new fiber products by using the unique combinations of these properties,
which are not found in either nylon or PET.

Fiber end-use applications include (1) ready-to-wear, active-wear, intimate

apparels, inner linings where stretch-recovery, softness, hand, and drape are the
key attributes; (2) carpets where resiliency, newness retention, stain resistance,
and low static generation provide values over currently used materials in some
market segments; (3) automotive and home upholstery utilizing the easy dyeing,
stain resistance, stretch-recovery properties. Within a short period of time since
the polymer’s commercialization, PTT ready-to-wear stretch apparels (52) and
resilient floor coverings had already appeared in the market (since 1999).

Other applications are in monofilaments, nonwovens, films, engineering ther-

moplastics, and molded goods. Paper forming fabrics made with PTT monofil-
aments have been patented (53) for use in papermaking machines because
PTT combines the chemical resistance of a polyester and the resiliency of the
less chemical resistant nylon. PTT non-woven fabric shows better dimensional

Table 4. Comparison of PTT, PET, and Nylon Fiber Properties

Property

PTT

PET

Nylon

Yarn bulk and crimp

Excellent

Good

Excellent

Resiliency, stretch-recovery

Excellent

Fair

Excellent

Dyeing

Very good

Good,

Excellent,

disperse-dyed at

disperse-dyed

acid dyed

atmospheric boil

under pressure

without carrier

with carrier

Stain resistance

Excellent

Excellent

Poor to very good

Electrostatic propensity

Excellent

Excellent

Poor to very good

Hand and softness

Excellent

Excellent

Very good

Drape

Excellent

Fair

Excellent

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POLY(TRIMETHYLENE TEREPHTHALATE)

553

stability and is softer than polypropylene (54). Other applications include syn-
thetic leathers (55) and flexible transparent film for packagings (56).

Fiber Processing.

PTT used for fiber applications has IV of 0.80–

0.92 dL/g (M

n

≈ 16,000–20,000). Prior to melt processing, the polymer chips must

be dried to a moisture level of

<30 ppm to avoid hydrolytic degradation. A close-

loop hot air dryer is preferred. PTT is dried at 130

◦

C and at a dew point of

<−40

◦

C

for 6 h. Because of the faster crystallization rate, PTT chips are already semicrys-
talline after palletizing, and do not require a precrystallization step prior to drying
as in PET.

The dried polymer is extruded at 250–265

◦

C into fibers using conventional

processing machines for bulk continuous filaments (BCF), partially oriented yarn
(POY), spin-draw yarn (SDY), and staple fiber.

Carpets.

The process of making PTT BCF carpets has been described in

detail (57). The extruded yarn is drawn between sets of heated godets to a draw ra-
tio 2.8–3.5 (58,59). It is then textured with hot air at 160–220

◦

C and at a pressure

of 0.6–1.0 MPa (87–145 psi) (60). Heat-setting with steam is at 135–145

◦

C or at

175–195

◦

C (61) when heat-set with the less effective heat conducting superheated

steam. Tufted carpets are dyed with disperse dyes at atmospheric boil (62) in a
continuous or a batch process. PTT carpets show excellent resiliency equivalent
to a nylon in walk tests, have lower static charge of

<3.5 kV, and are resistant to

coffee, mustard, betadine, red acid dyes, and other stains (63).

Textile Fibers.

PTT POY is spun using PET POY or SDY fiber spinning

machines. Table 5 shows the tenacities and elongations of PTT fiber as a function
of spinning speed (64). Tenacity increases while the elongation decreases with
increasing speed. The PTT fiber stress–strain curve, unlike PET, has an inflexion
point like a knee (45,65). A fully oriented PTT fiber has a modulus of 2.58 GPa
(374,000 psi) compared to 9.15 GPa (1.33

× 10

6

psi) of PET (45).

PTT yarn has been textured by false-twist method at 140–160

◦

C (64). Crimp

development was almost twice as high as PET with crimp contraction reaching
about 50%. When PTT yarns with a high level of crimp contraction are knitted
into stretch fabrics, the amount of stretch achieved is equivalent to PET stretch
fabrics incorporated with 6–8% of Spandex (66). In addition to stretch, PTT fabrics
tend to have softer hand and better drape than PET. Since PTT does not absorb
moisture like nylon, PTT fabrics also have a desirable dry touch and comfort.

Table 5. Tensile Properties of 150 dtex

a

/34-filament PTT Fiber as a

Function of Spinning Speed

Spinning speed, m/min

Tenacity N/tex

b

Elongation, %

600

0.090

252

1000

0.124

176

1500

0.148

146

2000

0.162

125

2500

0.195

97

3000

0.188

68

a

150 dtex

= 135 den.

b

To convert N/tex to g

·f/den, multiply by 11.33.

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POLY(TRIMETHYLENE TEREPHTHALATE)

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Table 6. Properties of Glass-Filled Polyesters

Property

PET

PTT

PBT

Glass content, wt%

28

30

30

Tensile strength, MPa

a

159

159

115

Flexural modulus, GPa

b

8.97

10.4

7.60

Heat distortion temperature @ 1.8 MPa,

◦

C

224

216

207

Notched Izod impact, J/m

c

101

107

85

Specific gravity, kg/m

3

1560

1550

1530

Mold shrinkage, m/m

0.002

0.002

0.002

a

To convert MPa to psi, multiply by 145.

b

To convert GPa to psi, multiply by 145,000.

c

To convert J/m to ft

·lbf/in., divide by 53.38.

Dyeing.

Because of its low T

g

, PTT is disperse-dyed at atmospheric boil

without using carriers for plasticization (62,67,68). Most countries have legisla-
tions prohibiting or regulating the use of the environmentally harmful biphenyl
type carriers. PTT is thus a much more environmentally friendly polymer than
PET in this respect, although PET is now dyed under pressure at 130

◦

C with-

out using carrier. The dye uptake of PTT and PET fibers has been compared by
measuring their Kulbelka–Munk, K/S, values as a function of dyeing temperature
(68). PTT reached and leveled off at K/S of about 16 at 100

◦

C whereas PET did

not absorb much dye at this temperature. Dye uptake only leveled off at

>120

◦

C

dyeing temperature with a less dense color shade K/S value of 13.

Injection Molding.

Several patents describe the injection molding of PTT

for applications as transparent heat-resistant bottles (69), impact, heat, and bend-
ing resistant electrical connectors (70) and others. Neat PTT can be injection
molded at 250–260

◦

C into a mold maintained at 70–80

◦

C under a holding pressure

of 3.1–4.2 MPa (450–609 psi) and a cycle time of 40 s (40). Colder mold temper-
ature tends to cause uneven crystallization with the formation of an amorphous
transparent skin and a highly opaque crystalline core. The spherulites formed
ranged from small and disordered at the outer edges to more perfect and larger in
the core with high stress-concentration interfaces. In extreme cases, the molded
article could become brittle. Glass-filled PTT crystallizes at a much faster rate and
reduces the cycle time to 30 s. Table 6 compares the properties of a 30% glass-filled
PTT with PET and PBT (40). The heat distortion temperature is greatly improved
by the glass from 59 to 216

◦

C. Notched Izod impact is similar to that in PET and

slightly better than in PBT.

Health and Safety

Since PTT is a new commercial product, Shell took up the responsibility of product
stewardship (71) and registered the polymer on the chemical inventory lists of
several countries. As a high molecular weight polymer, PTT is biologically inactive
and requires safe handling like other commercial polymers.

When PTT is exposed to high heat such as during drying and melt processing,

it releases acrolein, allyl alcohol, and cyclic dimer by-products (71). Among them,

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POLY(TRIMETHYLENE TEREPHTHALATE)

555

acrolein is of special concern because it is a very strong lacrymator. It also irritates
lung and respiratory tracts and affects breathing. The effects are acute and do
not have cumulative long-term effects. OSHA industrial hygiene guidelines for
time-weighted exposure limit of acrolein over a period of 8 h is 0.1 ppm, and the
short-term exposure limit for 15 min is 0.3 ppm. Therefore, adequate ventilation
must be provided to avoid acrolein exposure.

BIBLIOGRAPHY

1. Br. Pat. 578079 (June 14, 1946), J. R. Whinfield and J. T. Dickson.
2. U.S. Pat. 3984600 (Oct. 5, 1976), S. Kawase and T. Kuratsuji (to Teijin Ltd.).
3. U.S. Pat. 3584103 (June 8, 1971), M. E. Harris (to E. I. du Pont de Nemours & Co.,

Inc.).

4. Br. Pat. 1254826 (Nov. 24, 1971) (to Fiber Industries, Inc.).
5. Eur. Pat. Appl. 478850A1 (Aug. 4, 1992), E. Drent; U.S. Pat. 5684214 (Nov. 4, 1997), P.

R. Weider, J. B. Powell, and K. T. Lam (to Shell Oil Co.).

6. P. Nager, Paper presented at CHEMSPEC Asia ’91, Tokyo, Japan, June 24–25,

1991.

7. H. H. Chuah, Paper presented at Tifcon ’96, The Textile Institute, Blackpool, U.K., Nov.

6, 1996.

8. DuPont Sorona

TM

Selected As Brand Name for 3GT Polymer, Press Release, April 11,

2000, E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.

9. Process Economics Program Report 227, 1,3-Propanediol and Polytrimethylene Tereph-

thalate, SRI International, 1999.

10. DE 3734764 A1 (May 3, 1989), K. Tran-Dinh and F. F. Hill (to H ¨

uls AG).

11. WO 9928480 (June 10, 1999), R. V. Nair and co-workers (to E. I. du Pont de Nemours

& Co., Inc., and Genecor International, Inc.).

12. U.S. Pat. 4611049 (Sept. 9, 1986), T. Kuratsuji and T. Miki (to Teijin Ltd.).
13. U.S. Pat. 5340909 (Aug. 23, 1994), M. L. Doerr, J. J. Hammer, and J. R. Dees (to Hoechst

Celanese Corp.).

14. H. H. Chuah, R. W. Vinson, and C. W. Ulzelmeier, Research Awareness Bulletin, Shell

Chemical Co., July 1993, p. 101.

15. U.S. Pat. 5763104 (June 9, 1998), J. M. Stouffer, E. N. Blanchard, and K. W. Leffew (to

E. I. du Pont de Nemours & Co., Inc.).

16. H. H. Chuah and S. L. Wallace, Research Awareness Bulletin, Shell Chemical Co., Aug.

1993, p. 97.

17. S. Schauhoff, Chem. Fibers Int. 46, 263 (1996).
18. X.-S. Wang, X.-G Li, and D. Yan, Polym. Degrad. Stab. 69, 361 (2000).
19. U.S. Pat. 6093786 (July 25, 2000), D. R. Kelsey (to Shell Oil Co.).
20. H. H. Chuah, H. S. Brown, and P. A. Dalton, Int. Fiber J. 10(5), 50 (1995).
21. K. M. Lee, K. J. Kim, and Y. H. Kim, Polymer (Korea) 23, 56 (1999).
22. J. M. Huang and F. C. Chang, J. Polym. Sci., Part B: Polym. Phys. Ed. 38, 934

(2000).

23. M. Pyda and co-workers, J. Polym. Sci., Part B: Polym. Phys. Ed. 36, 2499 (1998).
24. H. H. Chuah, Polym. Eng. Sci. 41, 308 (2001).
25. H. H. Chuah, Introduction to PTT Chemistry & Technology, Short course at Shell Chem-

ical Company, Westhollow Technology Center, Dec. 1995.

26. M. Pyda and B. Wunderlich, J. Polym. Sci., Part. B: Polym. Phys. Ed. 38, 622 (2000).
27. B. J. Bulkin, M. Lewin, and J. Kim, Macromolecules 20, 830 (1987).
28. H. H. Chuah, D. Lin-Vien, and U. Soni, Polymer 42, 7137 (2001).

556

POLY(TRIMETHYLENE TEREPHTHALATE)

Vol. 3

29. H. L. Traub, and co-workers, Die Angew. Makromol. Chemie 230, 179 (1995).
30. O. F. Solomon and I. Z. Ciut ˜a, J. Appl. Polym. Sci. 6, 683 (1962).
31. N. Kuwahara, J. Polym. Sci. A 1, 2395 (1963).
32. S. H. Maron, J. Appl. Polym. Sci. 5, 282 (1961).
33. M. V. R. M. Rao, and M. Yaseen, J. Appl. Polym. Sci. 31, 2501 (1986).
34. I. J. Desborough, I. H. Hall, and J. Z. Neisser, Polymer 20, 545 (1979).
35. Y. Chatani and co-workers, Ann. Meet. Soc. Polym. Sci. Kyoto, Preprints, 1977, p. 427.
36. S. Poulin-Dandurand and co-workers, Polymer 20, 419 (1979).
37. B. Moss and D. L. Dorset, J. Polym. Sci., Part B: Polym. Phys. Ed. 20, 1789 (1982).
38. H. H. Chuah and B. T. A. Chang, Polym. Bull., (in press).
39. A. Ziabicki, Research on PolyTrimethylene Terephthalate and Corterra

®

Fibers, Sem-

inar presented at Shell Chemical Company, Westhollow Technology Center, Feb.
1999.

40. K. Dangayach, H. Chuah, W. Gergen, P. Dalton, and F. Smith, in Proc. SPE 55th Ann.

Tec. Conf. & Exhibits, 1997, p. 2097.

41. C. C. Gonz ´alez, J. M. Pere ˜

na, and A. Bello, J. Polym. Sci., Part B: Polym. Phys. Ed. 26,

1397 (1988).

42. G. Farrow, J. McIntosh, and I. M. Ward, Makromol. Chem. 38, 147 (1960).
43. J. G. Smith, C. J. Kibler, and B. J. Sublett, J. Polym. Sci., Part. A-1 4, 1851 (1966).
44. N. G. McCrum, B. E. Read, and G. Williams, Anelastic and Dielectric Effects in Polymeric

Solids, John Wiley & Sons, Inc., New York, 1967.

45. I. M. Ward, M. A. Wilding, and H. Brody, J. Polym. Sci., Part B: Polym. Phys. Ed. 14,

263 (1976).

46. K. Nakamae and co-workers, Zairyo 35, 1066 (1986).
47. I. Sakurada and K. Kaji, J. Polym. Sci., Part C 31, 57 (1970).
48. R. Jakeways and co-workers, J. Polym. Sci., Part B: Polym. Phys. Ed. 13, 799

(1975).

49. K. Dangayach, K. Ghosh, H. H. Chuah, B. Cristea, and W. P. Gergen, Paper presented

at ETP’99, Zurich, June 7–9, 1999.

50. F. W. Werny, Carpet & Rug Industry 23(6) 38 (1995).
51. Sorona

TM

3GT’s Attributes, Website product information, E. I. du Pont de Nemours &

Co., Inc., 2000.

52. C. Heschmeyer, Int. Fiber J. 15(4), 66 (2000).
53. U.S. Pat. 5104724 (Apr. 14, 1992), C. Y. Hsu (to Wangner System Corp.).
54. C. Hwo and co-workers, Poly(trimethylene phthalates or napthalate) and Copolymers:

New Opportunities in Film, Engineering Thermoplastic and Other Applications, Tech-
nical Bulletin, SC:2731-98, Shell Chemical Co., 1998.

55. Jpn. Pat. 11222780 (Aug. 17, 1998) G. Bungo and M. Akiharu (to Asahi Chemical

Industry Co., Ltd.).

56. Jpn. Pat. 08325391 (Dec. 10, 1996), T. Sato, T. Imamura, and T. Matsumoto (to Nippon

Esters, Ltd.).

57. H. H. Chuah, Processing of Corterra

®

Polytrimethylene Terephthalate Polymer for

Bulk Continuous Filament Carpets, Technical Bulletin SC:2528-98, Shell Chemical
Co., 1998.

58. U.S. Pat. 5645782 (July 9, 1997), J. M. Howell, W.-H. Tung, and F. Werny (to E. I. du

Pont de Nemours & Co., Inc.).

59. U.S. Pat. 6113825 (Sept. 5, 2000), H. H. Chuah (to Shell Oil Co.).
60. F. Werny and H. Chuah, Int. Fiber J. 11(4), 62 (1996).
61. J. D. Polejes and co-workers, Int. Fiber J. 13(6), 26 (1998).
62. H. H. Chuah, F. Werny, and T. Langley, Book Pap.—Int. Conf. Exhib., The American

Association of Textile Chemists and Colorists, 1995, pp. 98–106.

Vol. 3

POLY(TRIMETHYLENE TEREPHTHALATE)

557

63. H. H. Chuah, Chem. Fiber Int. 46, 424 (1996).
64. H. S. Brown and H. H. Chuah, Chem. Fiber Int. 47, 72 (1997).
65. H. L. Traub, P. Hirt, and H. Herlinger, Chem. Fiber Int. 45, 110 (1995).
66. M. Moerman, Corterra

®

PTT Polymers: Downstream Textile Development Generation

1 Information Package, Shell Chemical Co., 2000.

67. H. L. Traub, P. Hirt, and H. Herlinger, Melliand Textilber 76, 702 (1995).
68. Y. Yang and co-workers, Textile Chemist and Colorist & American Dyestuff Reporter

1(3), 50 (1999).

69. Jpn. Pat. Appl. 05031789 (Feb. 9, 1993), K. Kawaguchi, T. Nakane, and K. Hijikata (to

Polyplastics Co.).

70. Jpn. Pat. 11054189 (Feb. 26, 1999), H. Matsumoto and co-workers (to Toray Industries,

Inc.).

71. K. S. Kiibler and co-workers, Byproduct Emissions from Poly(trimethylene terephtha-

late): Studies on the Release of Acrolein and Allyl Alcohol During Processing, Storage,
and Shipping of PTT, Technical Information Report, WTC-3659, Shell Chemical Co.,
2000.

H

OE

H. C

HUAH

Shell Chemical Company

POLY(VINYL ACETATE).

See V

INYL

A

CETATE

P

OLYMERS

.

POLY(VINYL ALCOHOL).

See V

INYL

A

LCOHOL

P

OLYMERS

.

POLY(VINYL CHLORIDE).

See V

INYL

C

HLORIDE

P

OLYMERS

.

POLY(VINYL ETHER).

See V

INYL

E

THER

P

OLYMERS

.

POLY(VINYL FLUORIDE).

See V

INYL

F

LUORIDE

P

OLYMERS

.

POLY(VINYLIDENE CHLORIDE).

See V

INYLIDENE

C

HLORIDE

P

OLYMERS

.

POLY(VINYLIDENE FLUORIDE).

See V

INYLIDENE

F

LUORIDE

P

OLYMERS

.

558

POLYAMIDES, AROMATIC

Vol. 3

POLYACETAL.

See A

CETAL

R

ESINS

.

POLYACRYLAMIDE.

See A

CRYLAMIDE

P

OLYMERS

.

POLYACRYLATES.

See A

CRYLIC

E

STER

P

OLYMERS

.

POLYACRYLONITRILE.

See A

CRYLONITRILE

P

OLYMERS

.