Copolymerization reactivity of monomers and sequence structure of copolymers during the curing of UPR Undergraduate: Congcai Wang Supervisor: Professor Ruiwei Guo Department of Polymer Science and Engineering, School of Chemical Engineering and Technology, Tianjin University. 1

Content Degradation methods 2 Experimental program 3 3 Fountain of the project 3 1 Determination methods 4 2

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. 3

Degradation products Cured UPR Sequence structure UP/St DSC FTIR Degradation 1 H NMR 13 C 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. 4

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 5

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. 6

Degradation behavior of unsaturated polyester resin in alcohols. Hojo,H, K. Ogasawara, W. L. Chang, K. Tsuda. Composite Materials.Vol..3,No.4, (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: 7

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 8

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, (1971). UP/St Initiator Cured UPR 1. 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

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=11 m=

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 11

3. Determination methods There are many techniques measuring the sequence structure. The techniques used in UPR mainly contain DSC, FTIR, 1 H NMR, 13 C NMR. DSC and FTIR can measure conversion rate, and the specras of 1 H NMR, 13 C NMR can measure the content of less than triad and multi-unit in copolymers. They are also used to calculate the average sequence length. 12

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 curing behaviors was investigated. This experiment also affirmed the shielding effect of network. 3.1 DSC, FTIR 13

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. 14

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 1 H NMR and 13 C 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 13 C NMR H NMR, 13 C NMR 15 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 1 H NMR, 13 C NMR and FTIR.

Determinating the sequence distribution: Bara et al. obtained compositions of vinyl acetate/methyl acrylate (V/M) copolymer from 1 H NMR spectroscopy. The microstructure was obtained in terms of the distribution of V- and M-centered triad sequences from 13 C{ 1 H}–NMR spectra of copolymers. Homonuclear 1 H-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 1 H NMR, 13 C NMR, two-dimensional NMR techniques such as heteronuclear single quantum coherence(HSQC) and heteronuclear multiple quantum coherence(HMQC). 16

Monomer Sequence Distribution in Styrene-Maleic Anhydride copolymers. Bonnie E. Buchak, Kermit C. Ramey. Polymer Letters Edition. Vol. 14, (1976). Structure Chemical shifts of C 1 (ppm) Assignment SSS144This peak in the SMA copolymer spectra is seen to grow with increasing concentrations of styrene. MSS, SSM Assuming that the γ-substitution has a smaller effect than the β-substitution, the C 1 of an MSS triad will fall slightly upfield from that of an SSS triad(viz.,142ppm) and the C 1 of an SSM traid will fall more upfield and slightly downfield from that of an MSM central C 1 (viz., 138ppm). MSM137This peak in the SMA copolymer spectra grows with increasing maleic anhydride concentration. The chemical shift of C 1 (the styrene aromatic carbon directly attached to the polymer backbone) in copolymer 17

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/St Co MEKP Cured UPR 1. Extraction 2. KOH in methanol 3. Separation Benzene layer Distill Degradation products 18

Program B: alcoholysis by methanol UP/St Co MEKP Cured UPR 1. Extraction 2. Methanol, p-toluenesulfonic acid 3. Filtration Degradation products Standard method Molecular weight Acid and hydroxyl values VPO Calculation Average sequence length 1 H NMR 13 C NMR Sequence structure 19

4.2 Analysis of sequence structure of obtained linear copolymers The procedure: (1) Prepare polystyrene, maleate ester copolymer and determinate them by 13 C NMR; (2) Prepare styrene-maleate copolymer in different component proportions and determinate them by 13 C NMR; 20 (3) Assign the chemical shift of C 1 in styrene-maleate copolymer according to the changes of peak and component proportions and estiblish the relationship between chemical shift and characteristic C.

21 Structur e Chemical shifts of C 1 (ppm) Assignment SSS 144 This peak in the SMA copolymer spectra is seen to grow with increasing concentrations of styrene. MSS, SSM Assuming that the γ-substitution has a smaller effect than the β-substitution, the C 1 of an MSS triad will fall slightly upfield from that of an SSS triad(viz.,142ppm) and the C 1 of an SSM traid will fall more upfield and slightly downfield from that of an MSM central C 1 (viz., 138ppm). MSM 137 This peak in the SMA copolymer spectra grows with increasing maleic anhydride concentration. M- center >170The same method as analyzing S-center 1 C

4.3 Study the effect of conversions, monomer content and curing temperature to the sequence structure of styrene units 22 (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

(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; 23 Curing at different temperature Degradation by alcoholysis or hydrolysis Analysis: δ & C

24 (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; Curingconversion Average sequence length Regular sampling FTIR Calculation

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; Q 0 - the overall heat of the reaction 25