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Copolymerization reactivity of monomers and sequence structure of copolymers during the

curing of UPR

Undergraduate: Congcai WangSupervisor: Professor Ruiwei Guo

2012.9.7

Department of Polymer Science and Engineering, School of Chemical Engineering and Technology, Tianjin University.

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Content

Degradation methods2

Experimental program

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Fountain of the project 31

Determination methods

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1. Fountain of the project

On basis of developing knowledge on the radical curing of polyester resin systems for AkzoNobel Corporate, the studying team of professor Guo cooperated with AkzoNobel and proposed a project feasibility study report about the research ideas, in which the project was divided into two sub-projects and corresponding research contents.

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Degradation products

Cured UPR

Sequence structureUP/St

DSCFTIR

Degradation

1H NMR13C NMR

My task

Network structure’s forming and its shielding effect will have an influence on the curing of UPR, and strongly affect properties of UPR,

such as toughness, intensity, hardness, shrinkage, etc.

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The research content:

2-1. De-crosslinking of cured UPR by alcoholysis or hydrolysis to obtain linear copolymers consisted of fumarate (or maleate) and styrene units;

2-2. Analysis of sequence structure of obtained linear copolymers;

2-3. Study the effect of conversions, monomer content and curing temperature to the sequence structure of styrene units.

My project: Copolymerization reactivity of monomers and sequence structure of copolymers during the curing of UPR

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2. Degradation methods

Degradation methods of UPR reported are alcoholysis,

hydrolysis and Subcritical water.

The degradation of copolymers is a process of opening the

ester bonds so that we can obtain short chains or linear chains

which are easy to measure. So we also look up other esters’

degradation methods.

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Degradation behavior of unsaturated polyester resin in alcohols.Hojo,H, K. Ogasawara, W. L. Chang, K. Tsuda.Composite Materials.Vol..3,No.4,341-353(1994).

The immersion test was conducted by immersing the test specimens in the environmental liquid(pure water, methanol, ethanol, 1-propanol, 1-butanol and methanol solution) at constant concentration and temperature for a maximum of 1600h.

Figure 4: After the change in wet weight reaches the maximum(about 12%) independently of temperature it decreases, implying that corrosion is in progress.

2.1 Degradation methods of UPR Alcoholysis:

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Physical degradation is dominant for resin and the degree of corrosion is relatively low. The form of corrosion is of the “penetration type” and the resulting corrosion degradation is due to the transesterification reaction.

Figure 6: The degree of corrosion is in the order methanol ＞ ethanol ＞ 1-propanol ＞ 1-butanol, which implies that the larger the number of carbon atoms in the alcohol, the larger the molecular size, thus functioning as resistance to diffusion of the alcohol in the resin.

Methanol

Alkali hydrolysis by KOH:

Crosslinking and Degradation of a Side-Chain-Unsaturated Polyester.N.A.Ghanem,M.H.Nosseir,(Miss)N.I.Hussein.European Polymer Journal,Vol. 7, 943-951(1971).

UP/StInitiator Cured

UPR1. Extraction

2. 1M KOH in methanol

Benzene layer

Distill

Degradation products

Molecular weight

Acid and hydroxyl values

VPO

Calculation

Average sequence length

The bands at 3400cm-1 characteristic for the hydroxyl group is in direct correlation with the experimental hydroxyl values.

IR

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The allylic double bond in the polyester has low reactivity towards styrene which forms branches on the allyl ether side chains. It has higher reactivity towards methyl Methacrylate and its 1:1 mixture with styrene to form real crosslinks between the allyl ether side chains of the polyester.

n=11m=0-11

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Aminolysis

•PET(ethanolamine, 40% aqueous methylamine, 70% aqueous ethylamine, 98% aqueous n-butylamine)

Supercritical Alcohol

• PET(supercritical methanol, ethanol and propanol)

•PET(ethylene glycol, tetraglycol)

•PHB(ethylene glycol, glycerol)

Alcoholysis

Hydrolysis

• PET(Sulfuric Acid, Nitric Acid, KOH, NaOH.)• Crosslinkable copolyesters(NaOH)

2.2 Degradation methods of other esters

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3. Determination methods

There are many techniques measuring the sequence

structure. The techniques used in UPR mainly contain DSC,

FTIR, 1H NMR, 13C NMR.

DSC and FTIR can measure conversion rate, and the

specras of 1H NMR, 13C NMR can measure the content of less

than triad and multi-unit in copolymers. They are also used to

calculate the average sequence length.

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Effects of Resin Chemistry on Redox Polymerization of Unsaturated Polyester Resins.HUAN YANG, L. JAMES LEE.Journal of Applied Polymer Science, Vol. 84, 211–227 (2002).

The reaction kinetics of a series of well-defined polyester resins at temperatures between 35 and 90 was studied using DSC and ℃FTIR. The effect of the degree of resin unsaturation on the curingbehaviors was investigated. This experiment also affirmed the shielding effect of network.

3.1 DSC, FTIR

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Experimental results from FTIR and DSC measurements agree with each other reasonably well. The higher the degree of C=C unsaturation per molecule, the higher is the reaction rate. The diffusion-limitation effect is more significant for the polyester resin with a higher degree of unsaturation, leaving more unreacted C=C bonds trapped inside the matrix after vitrification, resulting in lower final conversions of polyester and styrene C=C bonds.

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Determinating the average sequence length:• Cui J. et al. and Zhao Q. Z. et al. determined the ratio of

components in copolyesters and calculated the average sequence length by 1H NMR and 13C NMR spectra.

• Zhao F. R. et al. studied the relationship of polybutadiene sequence structure and properties by NMR. They separated different conformers (cis-1,4-, trans-1.4-, 1,2-ethenyl) by thin-layer chromatography(TLC), and determined their contents by 13C NMR.

3.2 1H NMR, 13C NMR

• Dong H. R. et al. and James et al. determined ethylene-propylene mole fractions and methylene number average sequence lengths in ethylene-propylene copolymers by 1H NMR, 13C NMR and FTIR.

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Determinating the sequence distribution:• Bara et al. obtained compositions of vinyl acetate/methyl

acrylate (V/M) copolymer from 1H NMR spectroscopy. The microstructure was obtained in terms of the distribution of V- and M-centered triad sequences from 13C{1H}–NMR spectra of copolymers. Homonuclear 1H-2D-COSY and 2D-NOESY NMR were used to determine the most probable conformer for the V/M copolymer.

• Bara and his coworkers also determinated the microstructure (triad) of styrene and methyl methacrylate(S/M) copolymer by 1H NMR, 13C NMR, two-dimensional NMR techniques such as heteronuclear single quantum coherence(HSQC) and heteronuclear multiple quantum coherence(HMQC).

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Monomer Sequence Distribution in Styrene-Maleic Anhydride copolymers.Bonnie E. Buchak, Kermit C. Ramey.Polymer Letters Edition. Vol. 14, 401-405(1976).

Structure

Chemical shifts of

C1(ppm)Assignment

SSS 144 This peak in the SMA copolymer spectra is seen to grow with increasing concentrations of styrene.

MSS, SSM

138-142

Assuming that the γ-substitution has a smaller effect than

the β-substitution, the C1 of an MSS triad will fall slightly

upfield from that of an SSS triad(viz.,142ppm) and the C1

of an SSM traid will fall more upfield and slightly

downfield from that of an MSM central C1 (viz., 138ppm).

MSM 137 This peak in the SMA copolymer spectra grows with increasing maleic anhydride concentration.

The chemical shift of C1(the styrene aromatic carbon directly attached to the polymer backbone) in copolymer

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4. Experimental program 4.1 De-crosslinking of cured UPR by alcoholysis or hydrolysis to

obtain linear copolymers consisted of fumarate (or maleate) and styrene units.

Method A: hydrolysis by KOH

UP/StCo

MEKP Cured UPR

1. Extraction

2. KOH in methanol3. Separation

Benzene layer

Distill

Degradation products

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Program B: alcoholysis by methanol

UP/StCo

MEKP Cured UPR

1. Extraction

2. Methanol, p-toluenesulfonic acid3. Filtration

Degradation products

Standard method

Molecular weight

Acid and hydroxyl values

VPO

Calculation

Average sequence length

1H NMR 13C NMR

Sequence structure

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4.2 Analysis of sequence structure of obtained linear copolymers

The procedure:

(1) Prepare polystyrene, maleate ester copolymer and determinate

them by 13C NMR;

(2) Prepare styrene-maleate copolymer in different component

proportions and determinate them by 13C NMR;

(3) Assign the chemical shift of C1 in styrene-maleate copolymer

according to the changes of peak and component proportions and

estiblish the relationship between chemical shift and characteristic

C.

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Structure

Chemical shifts of

C1(ppm)Assignment

SSS144

This peak in the SMA copolymer spectra is seen to grow with increasing concentrations of styrene.

MSS, SSM

138-142

Assuming that the γ-substitution has a smaller effect than

the β-substitution, the C1 of an MSS triad will fall slightly

upfield from that of an SSS triad(viz.,142ppm) and the C1

of an SSM traid will fall more upfield and slightly

downfield from that of an MSM central C1 (viz.,

138ppm).

MSM137

This peak in the SMA copolymer spectra grows with increasing maleic anhydride concentration.

M-center

>170 The same method as analyzing S-center

1C

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4.3 Study the effect of conversions, monomer content and curing temperature to the sequence structure of styrene units

(1) The effect of monomer content:At the constant of initiator, accelerator and temperature, cure the UP at different St/UP(C=C)(the ratio is 1-3), then degradate the UPR, measure the degradation products and analyze the sequence structure according to the relationship established between δ and C;

Curing at different St/UP

Degradation by alcoholysis or

hydrolysis

Analysis: δ & C

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(2) The effect of curing temperature:At the constant of initiator and accelerator and St/UP(C=C), cure at different temperature (30,40,50, 60,70,80,90 ) , ℃then degradate the UPR, measure the degradation products and analyze the sequence structure according to the relationship established between δ and C;

Curing at different temperature

Degradation by alcoholysis or

hydrolysis

Analysis: δ & C

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(3) The effect of conversions:

At the constant of initiator and accelerator, at a temperature, cure the UP and regular sampling, measure the samples by FTIR, then analyze the conversion, and calculate the average sequence length combined with the reactivity ratio;

Curing conversionAverage sequence

length

Regular sampling

FTIR

Calculation

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At the same time, at the constant of initiator and accelerator, set a temperature, measure the process of curing by isothermal DSC, then calculate the relationship between conversion rate and time, and calculate the average sequence length at different conversion rate combined with the reactivity ratio;

α-conversion rate;t-time;Q- the heat of the reaction till to t;Q0- the overall heat of the reaction