The thermal dynamic study of polyester

Shi Dali 050412007015 Lin Yin 110012007055 Wang Xi 110012007095 Yang

Ge 140122007045

(Chemistry and Chemical engineering College, Ocean University of China,

Qingdao, Shandong Province)

Summary: The thermal stability of polyester directly determine

the scope and polyester. This paper through the thermal analysis

method and poor reduction micro business studies gather

terephthalic acid glycol (PET) and thermal stability, thermal dynamic

parameters of polyester, and according to the experimental data

and the polyester thermal stability of changing with temperature.

Key words: polyester thermal decomposition Poor reduction

micro business

Chinese library classification: X703.1

Literature identification code: A

Introduction

Polyester [1] diols by ErYuanSuan polyol or acids or high-molecular

compounds and condensation. Include polyester resin, polyester,

polyester acid etc. Such as, terephthalic acid Polyethylene glycol

esters [2] terephthalate (PET) consists of terephthalic acid (PTA) and

glycol (EG generated by condensation, including) part of the PET

again through the water cut and eventually generated. The glycol

esters [3] Polymethlene terephthalate (PMT) is based on the

potassium and 2 bromine ethane, or in the appropriate bromine

methylene chloride solvent reaction, belong to a new polyester.

Amorphous copolymerization pet PETG [4] by 1,4-dihiobenzene ring of

methanol modified polyethylene adipic acid esters two benjia

formed two new polyester, application of a wider range.

Polyester can with a wider temperature range to maintain good

physical properties, moisture absorption performance of small,

electric insulation performance is good, but in the high temperature

environment characteristics of easy throush degradation. Therefore

the thermal stability of polyester directly determine the scope of use

polyester, polyester and value to improve their study of pyrolysis

value increases the thermal stability of the vital role [5].

Based on the clustering of terephthalic acid esters, for example,

glycol, its thermal pyrolysis process dynamics research.

1 The basic properties of polyester

1.1 The physical properties of polyester

The relative density of polyester 1.11 ~ 120, in curing, polyester

shrinkage when the volume of physical properties are as follows:

(1) heat-resistant. Most of the thermal deformation temperature are

polyester in 50 ~ 60 ° c, some heat-resistant good polyester can

reach 1.2 degrees Celsius. Red-hot expansion coefficient of alpha 1

(130-150) x 10-6 degrees Celsius.

(2) mechanical properties. Unsaturated polyester resin with high

tensile strength, bending, etc.

(3) chemical resistance. Polyester resin, water resistant, dilute acids,

dilute alkali resistant, good performance of the organic solvent, at

the same time, the performance of polyester chemical resistance

with its chemical structure and geometric switch is different, can

have a big difference.

(4) the dielectric insulation performance, high coefficient.

1.2 Polyester chemical properties

Many kinds of polyester and chemical properties are different,

but the polyester under high temperature mechanism of complex

will cracking reaction. PET, such kinds of polyester PMT thermal

process is complicated, with phase change of temperature, reaction

mechanism are changing. The process of pyrolysis and PBT only one

stage, and reaction. Normally, with similar molecular structure of

polyester, molecular chain of benzene, thermal stability. Another pet

thermal stability and polyester additive type, content, and the

physical form of polyester.

2 Thermal analysis

Thermal analysis is in process control temperature

measurement, the physical properties of the material with a

temperature changes. According to determine ICTA physical

properties, will existing thermal analysis technology into 9 class 17.

Differential thermal analysis, DSC and thermogravimetric analysis

and thermal mechanical analysis of the four pillars of thermal

analysis is used to study the material, crystal transformation,

melting, sublimation and adsorption physical phenomena and

dehydration, decompose and chemical oxidation, reduction

phenomenon. They can provide fast by the thermal stability and

thermal decomposition product, the change process, various types

of infinite change point, the glass transition temperature and

softening point, heat, temperature and purity, blasting, and polymer

characterization of data structure and properties, but also for

balance and chemical kinetics studies of commonly used method.

2.1 Differential Scanning Calorimetry

DSC (Differential Scanning Calorimetry, DSC), is in process

control temperature measurement, the input to the sample and the

energy GSCC temperature difference of time or a kind of technology.

In the differential thermal analysis of samples, occurs when the

radiant heating rate of sample itself is nonlinear. For example, in

heat reaction to the sample after heating speed greatly behind

heating speed program control of heating or not, or even the

temperature, At the end of the reaction, sample for heating and

higher speed program control of heating speed, the temperature

control program gradually up, The temperature is always in the

change. But in heating, sample and GSCC and sample surrounding

environment have bigger difference, the heat transfer between

them, will reduce the sensitivity and accuracy of the thermal

measurement. So far, most of the differential thermal analysis

technology is not only quantitative analysis and qualitative or work

half quantitative analysis of work, in the process of change to obtain

the temperature and reaction kinetics sample data. Differential

scanning calorimetry thermal analysis is to overcome the amount in

the quantitative determination of differential thermal analysis on

these deficiencies and developed a new kind of thermal analysis

technology. This happened because of sample through the thermal

energy changes timely due compensation, and maintain between

GSCC remained the same temperature, temperature, heat transfer,

small signal detection, heat loss. Therefore the sensitivity and

accuracy are greatly improved, but the quantitative analysis of heat.

2.2 Thermogravimetric analysis

Many substances in heating and cooling process for heating, often

have the quality change the size of its changes, and the

temperature of the material and the chemical composition and

structure are closely related. Therefore use in heating and cooling

process quality of material, can change the physical differences and

different. Thermogravimetric analysis (TG) is, referred to as

Thermogravimetry in process control temperature measuring the

quality of material with the temperature of a relationship. Its

characteristic is quantitatively, can accurately measuring the quality

of material and the rate of change. At present, thermogravimetric

analysis method widely used in chemistry and chemical related

fields, in metallurgy, paint and ink science, ceramics, food

technology, inorganic chemistry, organic chemistry, polymer

science, biochemistry and geochemistry and play an important role.

The rmogravimetric analysis including the static and dynamic

method, method of two types.

The static pressure method and grading quality changes and

determination of two isothermal mass change. Pressure changes in

the quality and determination of spontaneous atmosphere

thermogravimetric analysis, is in process control temperature

measurement, in constant pressure balance quality under volatile

relationship with the temperature of a kind of method. The use of

sample decomposition of volatile products formed by gas as

atmosphere, and the constant pressure under control temperature

measuring quality and can reduce the process of thermal oxidation

process. The isothermal mass changes in temperature is refers to

the physical quality and measured under the conditions of

temperature of the relationship between a method. The temperature

of every must be constant temperature and constant intervals,

physical record of constant temperature relation curves. The high

accuracy, can record tiny weightlessness, but more time-consuming.

The method of dynamic and weight, temperature and thermal

gravimetric analysis into shang thermogravimetric analysis.

Thermogravimetric and micro business thermogravimetric analysis

are in the process of heating situations, the material quality change

with temperature. Micro business thermogravimetric analysis and

derivation thermogravimetric analysis (thermogravimetry

Derivative, respectively), it is the record of temperature and thermal

gravimetric curve of a Derivative of a kind of technology. Due to the

dynamic analysis and micro business tepid simple

thermogravimetric analysis, and practical techniques and DTA, DSC,

so widely used in thermal analysis technology.

3 Minus bad micro business

Poor reduction micro business (Freeman - Carroll) is a thermal

analysis curves (TG curve) some weightlessness rate of bottom,

temperature, and the difference between two adjacent to a method

of calculating activation energy. By the dynamic equation can be

obtained with Arrhenius equation (1):

α/d T=A/βexp ( - E/ R T) (1 - α) n (1)

The (1) type sides at Δ trypanblau again by lg (1 - alpha),

Get type (2),

Δlg(dα/d T)/Δlg (1 - α )= -E/2. 303R •Δ (1/T)/Δlg( 1 - α )+ n

(2)

Type, alpha for conversion, A for the (min 1); - Beta for heating

rate (c/min), T for temperature (K), E is for activation energy (mol);

kJ / N for reaction series, R for gas constant (8) 314 J mol/K). By Δ lg

(d/d T) / alpha Δ lg (1 - Δ of alpha) (1 / T) / Δ lg (1 - alpha) fitting

lines, through the linear gradient and intercept can obtain activation

E and reaction series of value, n. the E and n value into type (1), the

former refers to the value of A factor.

4 Polyester pyrolysis of experiment

4.1 Experimental process [6]

Select a b - a sample, b - PET the thickness of the PET 0.12 mm,

sample were taken 10.7 mg. By Swiss MET listed company DSC822e

TL ER type differential scanning calorimeter to differential scanning

calorimetry is hot (DSC) analysis, heating rate is 10 ° c/min from 25

° c to 1 min, insulation 290 degrees from 290 to 25 degrees Celsius,

static air atmosphere. By Swiss MET listed company production of TL

ER SD2TA851e type thermogravimetric TGA / / synchronous

differential thermal analyzer thermogravimetric analyzer for

pyrolysis loss (TG) analysis, heating rate is 10 ° c/min, from 25 ° c to

600 ° c, static air atmosphere. Porcelain crucible: 70 muon l.

4.2 Data analysis[6]

4.2.1 DSC analysis

Figure 1 samples of DSC spectra

As shown in figure 1 shows that the degree of overheating,

sample and cold.

Specimen of overheating: T = 230 degrees - 190 overheating

degrees = 40 ° c

Sample super-cooling: T super-cooling = 260 ° c = 65 ° c – 195

Super-cooling degree and overheat degree is mainly composed

of the impetus and phase transition process in the process of

temperature conditions. The change process "cold" and "over-

heated", detailed list will occur spontaneously, if cold faster (cold),

namely the little more easily crystallization, Similarly if overheating

faster (overheating during the process, so the easier it).

PET in molten state, only the crystallization parts change,

melting heat is actually destroying crystal structure need calories.

The higher the crystallinity, melting heat, namely the melting heat

and polymer is proportional to the crystallinity. The crystallization of

melting heat PET for 140.1 KJ/mol. Due to the PET chain rigidity,

crystallization slow, if the glass of PET slow-heat or slow cooling,

melt temperature in the glass transition temperature of the above

and below the melting point, can form a certain proportion of

crystalline structure. In certain temperatures PET materials should

be part of the crystallization of internal temperature or time limit

due to fully complete crystal, when temperature is higher than that

of the glass transition temperature of the molecular chain, soft and

have enough Yin sport ability to rearrange the crystallization, will

release the crystallization heat. Cold crystallization is located in the

Tg curve of DSC, reflects the PET after peak from the glass transition

temperature of cold and clean. Glass transition temperature of

amorphous phase provides information for chain, PET in glass

transition, can cause physical properties, especially the mechanical

properties, thus glass-transition temperatures are often used in PET

processing or the need to consider that a very important parameter.

Sample DSC analysis results

The glass transition

temperature Tg degrees

Celsius

93.81

The crystallization

temperature Tc degrees

Celsius

229.59

MJ exothermic

crystallization

22.17

Melting Tm degrees 260.31

Molten peak crystallinity

%

31.17

Molten peak heat J· g -467.31

Cold crystallization

temperature T 'C

degrees Celsius

197.28

Cold crystallization heat

mJ

440.76

4.2.2TG analysis

Figure 2 sample respectively, TG spectra

Pictured above, PET's TG curve of the first steps starting

weightlessness temperature zero for 337.74 degrees Celsius, the

initial temperature is 408.61 degrees Celsius, the end 478.49

degrees Celsius temperature for the second stage is the initial

temperature zero, zero degrees in 592.13 reaction, in 580 ~ basic

600 ° c interval, and almost no loss of residue 3.04%. To meet the

needs of engineering application, and other components of the PET,

with its decomposition temperature approximately 400 degrees.

Respectively for the small business TG curve thermogravimetric

curve, reflects the change rate and quality of sample temperature or

time. It can be seen in PET passion curve has two stages, so the

thermal pyrolysis of differential curve is heavy, two peak see chart.

Initial temperature

degrees Celsius zero

337.87

Decomposition

temperature degrees

Celsius

398.36

The reaction

temperature degrees.

Completely

588.26

The remaining amount

after reaction

3.04

Weightlessness rate

degrees Celsius

439. 53

4.3 Thermal dynamics research

4.3.1The calculation is studied. apparent activation

energy

4.3.1.1 Flynn - by Ozawa - studied. apparent

activation energy decomposition method

Flynn - by Ozawa - studied.apparent activation energy

decomposition method, below type:

Type of:β— — —The heating rate;

A — — —Frequency factor;

E— — —Thermal studied. apparent activation energy;

R — — —Gas constant;

α— — —Conversion。

4.3.1.2 Poor reduction micro commercial calculation

of this experiment data processing temperature

(by)

To better compare the main selection, PET activation reaction

relative severe 340-445 degrees and pp.961 ~ 561 degrees Celsius

temperature interval analysis, data processing, in general 2 degrees

Celsius temperature interval. Calculation results, see table 3 b - PET

in different temperature range of lg (d/d T) / alpha Δ lg (1 - Δ of

alpha) (1 / T) x 104 / Δ lg (1 - alpha) fitting lines (see figure 3 and 4.

In 340-445 pp.961 ~ 561 ° c and relative severe interval,

reaction temperature, only two of the investigation activation.

Table 3

Temperature

degrees

Celsius

Activatio

n E kJ/mol

Reactio

n series

n

Refers to

the

former

A/min

The linear

correlation

coefficient

r

340~445 167.13 0.66 4.33E+11 0.99490

515~561 123.04 0.70 1.05E+7 0.98363

FIG 3 o sample sent reduction micro commercial 340-445 degrees

Celsius temperature and reaction of interval series

4.3.2Reaction. Series

Figure 4 is bad for reduction micro sample in commercial pp.961

~ 561 degrees Celsius temperature and reaction of interval series

4.3.2.1 Coats - redfern method to calculate

the reaction series

For the polymer pyrolysis under inert angry, thermal dynamics

of basic equations for:

dC/dT=(a/β)exp(-E/RT)(1-C)n

Type of: C----------t Moments of weightlessness percentage

β--------- The heating rate

E---------- Activation reaction

A---------- Frequency factor

R---------- Gas constant

T---------- Absolute temperature

Most pyrolysis reaction pseudo-first-order reaction n = 1 used to

approximate. Using similar methods, coats - redfern lg ln [C] (1-1 / T

drawing to a line, if that is, except for the reaction, the reaction

occurs deviation line.

4.3.2.2 Minus bad micro calculated reaction

series (commercial) this experiment

data processing by

Using differential reduction micro commercial calculated under

the heating rate of single b - 340-445 degrees in PET temperature

range for the activation energy 12kJ/mol. 167, reaction series is 0.

66, refers to the former factor is 33E + 4) 11min - 1, 561 degrees

Celsius temperature in pp.961 ~ 123. For the activation energy

interval 04kJ/mol, reaction series is 0.70, Refers to the former factor

is 1. 05E + 7min- 1。

5 Conclusion

(1) b - PET thermal decomposition, mainly divided into two stages is

reaction.

(2) b - PET with the rise of temperature pyrolysis reaction

studied.apparent activation energy, reduce series, and increased

more prone to thermal.

(3) temperature on the thermal stability of polyester has a great

influence. In certain temperatures can maintain a stable polyester,

but when the temperature rise to polyester may produce

polycondensation reaction temperature rise, polyester

decomposition. Industrial production of polyester added stabilizing

agent, can make the thermal stability, but only within a certain

range, excessive stabilizers can rise to the contrary, stabilizer

species will also affect thermal stability [9].

(4) heating rate of pyrolysis products of different influence [7]. As the

temperature increases, polyester decomposition can produce

different result, through different temperature, the product can

speculate polyester category macromolecular molecular

composition [8].

6 References