A Presentation on

Critical Review of

Studies of Glycolysis of Poly (ethyleneterephthalate)

Recycled from Postconsumer Soft-Drink Bottles.I.Influences of Glycolysis Conditions.

CHENG-HO CHEN, HUH-YEAN CHEN,YU-WEN LO,CHING-FENG MAO,WEI-TUNG Published in Journal of Applied Polymer Science,

Vol. 80, 943–948 (2001)

Presented by

Munish AroraM.Tech. Fibers and Textile Processing Technology

Institute of Chemical Technology, Mumbai

1. INTRODUCTION 1.1 About the process 1.2 Application of glycolysis products of PET 2. EXPERIMENTAL3. CRITICAL REVIEW 3.1Originality 3.2 Technical correctness 3.3 Clarity 3.4 Bibliography 3.5 Title and Abstract 3.6 Illustrations and Tables 4. CONCLUSION

OVERVIEW

INTRODUCTIONThe problem of waste is now a global one.Most prevalent manufactured material plastics is not easily degradable.The methods of managing plastics are:• Land filling.• Composting.• Incineration.• Recycling. • Sewage.

Polyester• It is semi crystalline. • Excellent tensile and impact strength.• Chemical resistance. • Process ability. • Reasonable thermal stability.

Applications • In the textile industry.• In the manufacture of video and audio tapes.• In x-ray films.• In food packaging and especially of soft-drink bottles.

Need of Recycling• Widespread use, particularly in the beverage and food

industry. • High strength, not easily degraded• Environmental protection. • Energy preservation. • Economic benefits.• Limits the quantity of plastics sent to landfills. • Provides cheaper route to plastic production.

Recycling techniques • Primary.• Mechanical. • Chemical recycling and energy recovery.The acceptable one according to the principles of “sustainable Development” is chemical recycling,

Chemical recycling Defined as the process leading to total depolymerisation of PET into monomers, or partial depolymerisation into oligomers and other chemical substances.The main methods used are• Glycolysis. • Methanolysis.• Hydrolysis (alkaline, acidic and neutral).• Aminolysis and ammonolysis.

About the process:Glycolysis • The molecular degradation of PET polymer by glycols. • In the presence of catalysts i.e. metal acetates. • Ester linkages are broken and replaced with hydroxyl

terminals. • PET waste can be depolymerized by glycolysis to obtain

oligomeric diols and polyols.• Glycolyzed into its monomeric units, bis(2-

hydroxyethyl) terephthalate (BHET) or dimethyl terephthalate. • Bis(2-hydroxyethyl) terephthalate can be used as a

substrate to create PET and other polymers like polyurethane.

EXPERIMENTALCommercially clear PET soft-drink bottles were recycled &

washed.Cut into 0.4 * 0.4 cm flakes.Recycled PET flakes were dried.A 1000-mL four-necked flat-bottom reactor was used.The ratio of EG:PET used was 2:1 (w/w). The weights of EG and recycled PET flakes were 160 and 80 g.Influences of glycolysis temperature, glycolysis time, and

amount of catalyst on the depolymerization of recycled PET was observed.

Thermal analysis was also carried out.

Three groups were made.In first group• Temperature=190°C • Cobalt acetate (catalyst) = 0.002 mol. • The glycolysis time was varied (0, 0.5, 1.0, 1.5, and 2 h) In the second group • Temperature =190°C • Glycolysis time =1.0 h. • The molar amounts of Cobalt acetate were 0, 0.001, 0.002,

0.003, 0.004, 0.005, and 0.006 mol. In the third group • Time=1.0 h • Cobalt acetate = 0.002 mol.• Temperature was varied from 110 to 190°C at 20°C

intervals.The conversion for the glycolysis of the recycled PET flakes was defined as% conversion = A*B

A *100 %

A= A 80 g of recycled PET flakesB =the weight of undepolymerizedPET flakes.

RESULTS AND DISCUSSION

Influence of glycolysis time on glycolysis conversion of recycled PET flakes

Influence of amount of cobalt acetate on glycolysis conversion of recycled PET flakes

Influence of glycolysis temperature on glycolysis conversion of recycled PET flakes

Thermal analysis•Two DSC thermal analysis curves formed.• Curve a → BHET {bis (2-hydroxyethyl) terephthalate} fraction.•Melting temperature of the BHET fraction is 110°C.• Curve b → X fraction. X fraction = the fraction having BHET along with dimers and oligomers.•One peak is around 105°C.•Associated with BHET. •The other peak, centered at around 143°C.•Hence is considered as the melting of the dimer as well as BHET.

• Curve a shows the FTIR spectroscopy of the BHET fraction .• There is a broad peak between 3000

and 3500 cm-1.• Shows strong hydrogen bonding

among the BHET molecules.• Curve b shows the FTIR

spectroscopy of the X fraction.• A shoulder exists between 3000 and

3500 cm-1 in curve b.• This indicates that the energy of

hydrogen bonding is lower.• The higher hydroxyl number may

result in stronger hydrogen bonding.• This proves the BHET fraction has

higher hydroxyl numbers.

FTIR analysis

CRITICAL REVEIWOriginality• Extended study of paper by jong-wu chen, leo-wang

chen.• Published in J of App Polymer Sci, Vol. 73, 35–40 (1999). • Different catalyst was used.• Cobalt acetate was used.• Effect of temperature, time and catalyst was studied. • It is a little bit duplication of the process.

Technical Correctness• Effect of time, temperature and concentration of catalyst

are shown with the help of suitable graphs and values.• Has not mentioned anywhere about the pressure.• FTIR and DSC part has not been explained in detail.

Clarity• Explained the background of work first. • The need of the work.• Previous work on this subject. • Experimental setup and conditions.• Effect of various parameters like temperature, time

and catalyst concentrations on glycolysis rate.• The ways to analyse the effect. It shows• Paper is reasonably easy to follow and understand.• It does stick to the subject.Could be made more clear • By showing the formation of dimers and oligomers.• By showing the mechanism of the reaction taking

place.

Bibliography• Use of all the references in the text properly.• Paper accurately represents statements in cited references.

Title and abstract•Title is self explanatory.•Title is suitable and sufficient. •The abstract describes work very clearly.

• Gives the idea about the effect of various parameters on glycolysis. •Abstract brings out the main points of the paper.

Illustrations and tables• Results summarized in the tabulated manner.• Shows direct relation between the variation in the

parameter and the rate of glycolysis.• The illustrations are clear and easily readable. • There is no needless duplication between text

illustrations and tables.

CONCLUSION• Overall the author has explained the work very clearly.• For 100% glycolysis the conditions are

Temperature=190O CTime=1.5 hoursAmount of catalyst=0.002 mol.• The glycolysis conversion rate increased significantly with

the glycolysis temperature, glycolysis time,and the amount of cobalt acetate.• In the absence of catalyst no glycolysis was found.• The results from FTIR and DSC indicated that the BHET,

dimer, and other oligomers were predominately glycolysis products.