Diallyl phthalate (DAP) is widely used as a plasticizer in plastic containers, packaging, and medical devices. The appropriate diallyl phthalate addition can not only enhance the tensile strength and elongation at the break of PVC plastic but also be used as a chain extender to prepare high molecular weight PVC resin.

The transformation and interaction of diallyl phthalate

Whereas, as a plasticizer, diallyl phthalate cannot bond with the plastic matrices and will be released and contaminate the water after longtime storage under warm conditions. In previous reports, DAP has been detected in 0.009 μg/L in surface water and 0.22 ± 0.31 μg/L in wastewater. Although diallyl phthalate is not currently listed as a priority contaminant, it can cause health problems, including developmental toxicity and oxidative stress phenomenon. Yet the degradation process of DAP has not attracted enough attention. To date, except Fenton and biofilm treatment method, there are few studies on the treatment of DAP-containing wastewater. Moreover, there is little valuable information on the degradation and transformation process of diallyl phthalate in other mediums. Therefore, the main objectives of this study are: (1) Simulate the disinfection process of plastic packaging products and investigate the influence of plastic-type (polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC)), disinfectant concentration, typical ions and temperature on the degradation process of diallyl phthalate in plastics. (2) Identify the intermediate products through the interaction between plastics and DAP and clarify the possible mechanism combined with high-performance liquid chromatography-quadrupole time-of-flight-mass spectrometer (HPLC-QTOF-MS) with density functional theory (DFT).[1]

Considering the degradation of diallyl phthalate may be occurred by direct UV photolysis or DCCNa oxidation only, the removal experiments of diallyl phthalate in UV or DCCNa disinfection systems were designed to clarify the contributions of these effects. As shown, both UV direct photolysis and DCCNa disinfection could degrade DAP added to the plastic. The degradation efficiency of diallyl phthalate in PE, PP, and PVC with UV direct photolysis within 20 min were 86.2%, 23%, and 26.7%, respectively, and the degradation efficiency of DAP in PE, PP and PVC with DCCNa disinfection within 20 min were 34.5%, 28.6%, and 19.8%, respectively. It may be considered that the double bond on the diallyl phthalate side chain is easy to break under the action of UV photolysis. However, the combined effect of UV and DCCNa could significantly accelerate the degradation efficiency of diallyl phthalate, especially in DAP/PP and DAP/PVC systems. The degradation efficiency of DAP in PE, PP, and PVC plastics under the UV/DCCNa system was 87.5%, 82.4%, and 78.9%, respectively.

Diallyl phthalate in Plastics under UV/DCCNa Disinfection

Scientists systematically investigated the transformation and interaction of diallyl phthalate in the three kinds of plastic under UV/DCCNa disinfection process. The best treatment method of DAP supplied in PE plastic was long-strip static soaking treatment, while in PP and PVC plastic was a single-piece static soaking treatment. The optimal supplied concentration was 0.82 mg/g. The diallyl phthalate in PE plastic was the easiest degraded under the UV/DCCNa disinfection process, and the degradation efficiency could reach 87.5%. The difference in degradation efficiency of DAP among the three kinds of plastics could be attributed to the different degrees of active radicals reacted with plastics, which also lead to the rough and cracks or pits morphology of plastics. Compared with PP and PVC, the degradation of diallyl phthalate in PE was almost unaffected by the concentration of HOCl. HCO3?, Cl?, NO3?, NH4+, and SO42? had different effects on the degradation efficiency of DAP.[2]

The diallyl phthalate degradation efficiency in PE, PP, and PVC plastics under 0.0 ℃ could reduce to 46.7%, 62.6%, and 56.5% respectively, but the transformation could not be completely inhibited. Through product identification analysis, a total of seventy-six products were identified, and the transformation pathways including hydroxylation, chlorination, bond breaking, nitrosation, hydrolyzation, coupling reaction of diallyl phthalate in UV/DCCNa system, and interactive reaction between diallyl phthalate and three kinds of plastics were elucidated. Since most intermediate products with developmental toxicity and mutagenicity, and the formation of DCAA and TCAA was observed, attention needs to be paid to the environmental health risks during the disinfection process. In brief, this study provides significant information regarding the degradation of diallyl phthalate in PE, PP, and PVC plastics. The results of this study demonstrate the ubiquitous interaction between DAP and plastics, which should be taken seriously during cold sterilization.

Effect of ultrasonic separation on the structure and properties of diallyl phthalate prepolymer

The bulk polymerization of diallyl phthalate (DAP) was carried out at high temperature (190 degrees C) without using any initiator, and the reaction was stopped before the gelation point in order to get the prepolymer of diallyl phthalate. The mixture for the prepolymer and the monomer was successfully separated by a novel ultrasonic method for the first time, and the separation efficiency for the new method was obviously higher than that for the traditional reprecipitation. The product obtained by ultrasonic separation was characterized by infrared spectroscopy (IR), gel permeation chromatography (GPC) and iodine number measurement. It was shown that the average molecular weight of the prepolymer got by the ultrasonic method was lower than that of the prepolymer got by the multi-precipitation, moreover, the molecular weight distribution of the prepolymer got by the ultrasonic separation was broader. Besides, the residual unsaturation degree of the prepolymer separated by ultrasonic was slightly higher than that of prepolymer separated by reprecipitation.[3]

Wafer-Level 3D Integration Based on Poly (Diallyl Phthalate) Adhesive Bonding

Three-dimensional integration technology provides a promising total solution that can be used to achieve system-level integration with high function density and low cost. In this study, a wafer-level 3D integration technology using Poly (Diallyl Phthalate) as an intermediate bonding polymer was applied effectively for integration with an SOI wafer and dummy a CMOS wafer. The influences of the procedure parameters on the adhesive bonding effects were determined by Si-Glass adhesive bonding tests. It was found that the bonding pressure, pre-curing conditions, spin coating conditions, and cleanliness have a significant influence on the bonding results. The optimal procedure parameters for Poly (Diallyl Phthalate) adhesive bonding were obtained through analysis and comparison. The 3D integration tests were conducted according to these optimal parameters. In the tests, process optimization was focused on Si handle-layer etching, Poly (Diallyl Phthalate) layer etching, and Au pillar electroplating. After that, the optimal process conditions for the 3D integration process were achieved. The 3D integration applications of the micro-bolometer array and the micro-bridge resistor array were presented. It was confirmed that 3D integration based on Poly (Diallyl Phthalate) adhesive bonding is suitable for the fabrication of system-on-chip when using MEMS and IC integration and that it is especially useful for the fabrication of low-cost suspended-microstructure on-CMOS-chip systems.[4]

References

[1]Wu, J. N., Sui, B. X., Li, L., Meng, G. H., Guo, X. H., & Liu, Z. Y. (2017). Influences of diallyl phthalate as chain extender on the properties of high molecular weight poly(vinyl chloride) resin. Journal of Applied Polymer Science, 134(19), 45093.

[2]Zhang, S., Wei, J., Guo, R., Liu, B., Qu, R., Huo, Z., & Zhu, F. (2023). The transformation and interaction of diallyl phthalate (DAP) in the three kinds of plastic under ultraviolet/sodium dichloroisocyanurate (UV/DCCNa) disinfection process. Chemical Engineering Journal, 467, 143401.

[3]Xu SA, He M, Shi QF, Jin GC, Yao JQ, Yu RB, Wu CF. Effect of ultrasonic separation on the structure and properties of diallyl phthalate prepolymer. Ultrason Sonochem. 2008 Apr;15(4):364-369.

[4]Fang Z, You P, Jia Y, Pan X, Shi Y, Jiao J, He Y. Wafer-Level 3D Integration Based on Poly (Diallyl Phthalate) Adhesive Bonding. Micromachines (Basel). 2021 Dec 20;12(12):1586.