Rotation Of The Liquid Reactive Polymer Composites Molding Process

Rotational moulding is a process for manufacturing hollow plastic product. The number of advantages which includes low level of residual stresses, low product cost, being suitable to produce large hollow plastic production offered by this process over other plastic processing methods makes rotational moulding lots of engineering sense. But rotational moulding also has some disadvantages. Except for low strength of its product, high intensity of labour and long molding time, the rare species of raw material and hight cost to process them is the major one. All those disadvantages limit the development of rotational moulding. So, the development of new materials with desirable properties is of great significance in rotational moulding. Researchers have done lots of study in this field and obtained some satisfying results.Some researchers tried to use liquid plastics in this process very early. Compared with powdered polymer, liquid polymer can offer flexible reinforcing methods. This makes it possible for using continuous fibre to reinforce plastic, thus to improve mechanical property of final production. But operating liquid plastic in rotational moulding is difficult. The major problem is surface defects(bubbles) and poor material distribution. The purpose of this thesis is to study rotational moulding of molding continuous fibre reinforced thermosetting resin composites. In the end of this thesis, rotational foaming moulding of liquid reactive resin was studied and some significative results were obtained.In this thesis, a rotational molding machine was designed and made in order to match the requirement of rotational moulding experiment. The rotational speed can be adjusted separately in two directions. The mould can rotate along two orthogonal axes. The speed-regulating scope of its two axes is 0～35r/min. This machine could be used for making composite production by multi-kinds of liquid reactive resin.The process of rotational forming products can be divided into three stages-before forming, forming and defect creating according to the gel curve of corresponding thermosetting resin. The result of unsaturated polyester resin rotational molding experiment shows that the main problem is wall inhomogeneous. And this problem relate to the unsaturated polyester resin's original viscosity and gel velocity. With the help of the orthogonal test about original viscosity, gel velocity and the quality, it shows that the original viscosity effect the wall thickness and the gel velocity influence the wall homogeneous; it all shows that the orthogonal test can give the best processing parameter according to the certain product with different shape and size.Continuous fibre reinforced resin rotational moulding process was studied through special experiment. The results show that the main problem is not poor material distribution but surface bubbles. That's different from liquid resin rotational moulding. A view device was made in order to observe the formation of those bubbles. It can be concluded that non-uniform seepage velocity of the liquid resin and little driving force are the main factors which produce the surface bubbles. Product with non-surface defects (bubbles) can be obtained by adding flow channels in the inner wall of the mould.High speed centrifugal rotational moulding process was put forward and investigated in order to solve the problem which the driving force is small when liquid resin permeate continuous fibre. The results show that this technology can mostly reduce the number of surface bubbles. But there are still some bubbles in the inner wall of rotational moulding product. After the process simulation it can be concluded that this problem is caused by excessive rotational speed of the mould. Suitable process parameters can be obtained through process simulation.In the last part of this theis, liquid foaming resin system rotational moulding process was studied. The principle of this process was introduced. Rotational speed, speed ratio, ratio of raw materials and temperature which is important to the foaming process was analyzed. The experimentation results indicate that the bubble number increased with the increasing of the main axial speed. Uniform and compact foam can be obtained when the ratio of isocyanate and polyether was 1:1 and the ratio of stabilizing agent was 0.5～5%.According to the work which has been done and results which has been obtained in this thesis, The originality innovation includes the following points:1) study the rotational moulding process by using unsaturated polyester resin as raw material, firstly.2) The couple of chemical change and physical change in continuous fibre reinforced unsaturated polyester resin rotational moulding process was investigated, firstly and some meaningful results were obtained.3) The method of improving the rotational velocity of the mould is used in order to reduce the number of surface bubbles, firstly.4) Based on the finite element theory, the Lagrangian-Eulerian advection remap algorithm was used to simulate rotational moulding process.