11. 5 *The Application of FT-IR Spectrum Method in Photocuring Process for Polyester Acrylate

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1 11. 5 *The Application of FT-IR Spectrum Method in Photocuring Process for Polyester Acrylate Cao Jin Lu Xlanliang Zhang Zhenli East China University of Sci nee and technology Shanghai China Abstract This paper describles that the UV curing process of polyester acrylate can be monitored by measuring the degree of bouble bonds conversion with FT-IR spectroscopy. The various factors effect the UV curing rate. The relation between the curing rate and the concentration of photoinitiator crosslinking agent,, UV light intensity was discussed. INTRODUCTION Recently the UV curing technology was widely used in painty coating printed board % ink,, opti calfi ber adhesion agent and tooth material etc. field. C. Decker reported that Laser-induced polymerization of mono and mul ti acrylate monomer has been studied by using infrared spectroscopy, and degree of double bonds conversion was deterimened with the absorbance at 810 cm on IR specturm. This paper describles that the UV curing rate can be expressed by measuring the degree of bouble bonds conversion with FT-IR spectroscopy for polyester acrylate system. It was discussed that curing rate was related mutually to concentrati on of photoi ni tiat ors and crosslinking agent UV light intensity. EXPERIMENT Materi al The polyester acrylate has been prepared by the easteri fication with glycol and hcxanclioic acid. The photoinitiator, Trgacure 651( 2, 2 dimethoxy- 2- phenyl acetophenone) and Irgacure 184 (hydroxycyclohexyl phenyl acetone) is obatined from Ci ba Gei gy Co. Ltd. The active diluent, TMPTUri met hylol propane tri acrylate), EDGAC ethyl diethylene glycol acrylate),, HDDA(hexanediol acrylate), can be get from the market

2 JAERl-Conf Equi pment: The irradiation was carried out with UV radiator which consist of high pressure mercury (power 500W, 1000W, Model GG2) and M reflect plate and ventilating device for aim at cooling. Sample preparation and analysis method According to various molar ratios for polyester, active diluent and initiator were mixed to form photocuring paint. It is plated on KBr disk then UV curing and deterimi ning degree of double bonds with FT- TR spectroscopy. It exhibited absorption at 810 cm (-CH= CH- twisting) under UV irradiation. The decreasing of peak at 810 cm"* will refect the extent of the photocuring processes since the (A810) o -(A8l0) t is directly proportional to the number of acrylate functions. Thus, can be accounted degree of conversion for unsturated double bonds. (A810) o -(A8l0) t :%=- xiooy, (A810) RESULTS AND DISCUSSION 1. Influence of the kinds and concentration of photoi ni tiators on photocuring rate The curing rate closely related to the kinds and concentration of initiators in system of paint upon UV irradiation. The initiators absorb«-i the incident light which lead to production of active radical as a consequence of the reaction of polymerization and crossl i nki ng. The results showed that initiaton rate is in order of Irgacure 184 > Irgacure 651 > Benzophenone(BP). Since Irgacure 184 can straight clea/es to generate two free radical which induce the polymerization reaction. But Irgacure 651 cleaves to generate two free radical which the radical easily recompose to form yellow quinoid compound, decreasing the induce-polymerization rate. Irgacure *Q ^ *«Q Irgacure 651 mro *- «3 OCH,» OCH 3 6 OCH, + = \ OCH, OCH,

3 The influence of the concentration of phot oi ni t i at or was illustrated by Fig. 2. The photocuring rate increased with increasing the concentration of initiator. The relation of curing rate and concentration ofinitiator can be represented of Roc[S$ 2. Influence of the construction of active diluent curing rate Three kinds of active diluent were compared with each other. The initiation rate was illustrated as Fig. 3. The double bonds number for trifuncti onal monomer is more than di functional monomer or monofunctional monomer. Because trifuncti onal- have more viscosity than di functional - or monofunctional- so that the air diffuse difficulty in the system of paint, inhibiting effect of 0 on radical polymerization at induced step. After the induced reaction, the curing rate decreased with advancei ng of initiated reaction for system of coatining trifunctional monomer. It is explained that amount of gel enhanced introduing curing rate droping. In the practical operation, monofuncti onal- % dif uncti onal- and trifunctional- were mixed, applied on the coating system. 3. Influence of ratio of oligomerc polyester acrylate) with active dulent on curing rate It is important that the ratio of oligomer as main component with active diluent applied to photocuring system of paint. The experiment showed that when the molar ratio of oligomer to diluent is 1:1, the curing surface apparent the smooth and bright. The relation of curing rate and concentration of oligomer expresses Roc [M]. Fig The curing rate relation with UV light intensity The samples were exposed under high mercury lamp, study the influence of UV intensity which was adjusted by distance of sample from UV lamp on curi ng rate. The results lead to increase the curing rate-in proportion to light intensity. The Fig. 5. recored the relation of curing rate and light intensity Rp oc l 5. For the system of radical polymerization, the presence of 0 Z inhibits reaction progress as can be interpreted at Fig. 6. The double bond conversion % when the sample exposed to 5 sec in N 2 can be evaluated to reach near upon 100 %. 6. The post-polymerization was observed when the sample exposed to 5 sec in presence of 0 2 then put it in dark at room temperature after one hour, The degree of double bond conversion reached 89. 5%, two hour 90. 0%, twenty two hour 92. 0%

4 CONCLUSIONS 1. It is found that initiated efficiency for photoini tiator in the system of polyester acrylate arranges Irgacure 184) Irgacure 651) BP. 2. The relational formula for curing rate and concentration of initiator or concentration of oligomer or light i ntensi ty were: Rp oc [stf Rp oc [M], Rp oc [i]. 3. The sequence of avtive diluent which advance initiated rate was TMPTMA>TEGDA>HDDA. REFERENCE [1] C. Decker and Moussa, Real-Time Kinitic Study of Laser- Induced polymerization Macromolecules. Vol (1989) [2] I. K. Shahidi and J. A. Vona, Mod. Paint. Coating. Vol. 21(1975)

5 irradiated nan-irradiated cm Fig. l. FT-IR spectrum of the sample for irradiated and non-irradiated I irradiation time (sec) Fig.2. The effect of concentration of photoinitiator on curing rate Irgacure 184 (1) $% (2) 1H (3) \9i oligomer/diluent=h irradiation time (sec) Fig.3. The effect of various diluent on curing rate (l)hdda (2) TEGDA (3)TMPTMA Irgacure 184 2%

6 irradiation tiae (sec) Fig. 4. The effect of ratio of oligonervdiluent on curing rate (1)2:1 (2)1:1 (3) 1:2 diluenthdda irradiation tine (sec) Fig.5. The curing rate relation with light intensity (1) 93.7(nj.ca) (2) 50.4(nj.cm) (3) 26.7(aj. cm) oligoacr/diluent=h irradiaton time (sec) Fig. 6. The effect of atmosphere on curing rate oligoaer/diluent=li1-433-