Study on the preparation and properties of UV curable polyurethane materials modified by organic silicon

In this paper, polyester polyol, toluene diisocyanate (TDI) and hydroxyethyl acrylate (HEA) were taken as the raw materials to synthesize polyurethane acrylate. UV curable organic silicon nano sol was synthesized by γmethacryloxypropyltrime-thoxysilane. The UV curable polyurethane materials modified by organic silicon were prepared based on the UV curable organic silicon nano sol and synthesized polyurethane acrylate. This paper studies on the mechanical properties of organic silicon modified UV curable polyurethane materials and puts forward the micro model that inorganic phase is bonded to the resin in the form of chemical bonds. The results show that the heat resistance and mechanical properties of hybrid materials are improved with the increase of the nano silica sol’s contents , the abrasion resistance of hybrid coatings is also improved and the silica nano particles are well dispersed in the organic


Introduction
UV curable technology is a method to form a curable coating and products by taking ultraviolet light as curing energy. Photo-chemical reactions occurred in this process when liquid UV materials are excited by the UV light. UV curable technology has many advantages such as quickcuring, high-efficiency, energy saving, environmental protection, excellent performance of the cured product and so on. It is an environmentally friendly and energy efficient technology [1][2]. Polyurethane acrylate is an important light curing oligomer, which has high toughness and oil resistance after curing while the heat resistance is poor.
Organic / inorganic hybrid material will have excellent performance because organic / inorganic hybrid material could combine the characteristics of high toughness, high elasticity, excellent machinability of the organic phase with the high hardness and high modulus performance of the inorganic phase. It has become a research focus due to its obvious advantages in many aspects [3][4][5][6] .
The technology that prepares UV curable nano silica sol by sol-gel method has a lot of advantages.The mild reaction condition is a kind of this advantages ,it means the synthesis can realize at room temperature or slightly above the room temperature. In recent years, sol-gel technique has been rapidly developed in the preparation of organic / inorganic hybrid materials.
KeChangme i [7] prepared polyacrylate/TiO2 -SiO2 nano hybrid material with butyl titanate and ethyl orthosilicate as the metal alkoxide precursor, the appearance of inorganic particle in hybrid material is spherical, particle size is 90 ~ 110nm. Wei [8] finished the

The main instruments and equipments
The main instruments used in the tests are: UV-curing machine RW -UVA 201-20，Video based contact angle Measuring device OCAZO ， thermogravimetric analyzer TG209C ， Electronic Universal Material Testing Machine LR30KPlu，Differential scanning calorimetry DSC204F1， thermostat water bath HHS11-Ni1 ， Precision timing electric mixer JJ-1 and other major equipment.

Infrared spectrum analysis
The infrared spectra of nano sol was tested through the KBr tabletting method by Fourier transform infrared spectrometer tensor27 type that is produced by Bruker Corporation of Germany, scanning range is 400 cm -1~4 000 cm -1 .

Thermogravimetric analysis(TGA)
The speed of heating is 20℃/min, temperature range from 30℃ to 600℃ and test the concentration of nitrogen.

Coating hardness test
The pencil hardness of the coating according to the national standard GB6739-86 is done by using a set of pencils whose hardness is known. The hardness of the coating is expressed as the depth that pencil core can penetrate the surface of the coating to substrate.

Coating adhesion test
For adhesion test, the QFH Paints-cross-cut tester is used, according to the determination of GB/T1720-1979.
Test results are divided into six grades. Among them level 0 is for the best, while 5 is for the worst.

The preparation of UV-curable hybrid coatings
A certain concentration of nano sol and photoinitiator1173 was put into the polyurethane acrylate, then mixed homogeneously to get UV-curable hybrid coating.

Conclusions
Polyester polyol, toluene diisocyanate (TDI) and Hydroxyethyl acrylate (HEA) were taken as raw material to synthesize polyurethane acrylate. UV curable organo showed that the heat resistance of the hybrid materials was increased with the increase of the amount of nano -sol and the hardness of the hybrid film was also increased.