液态反应性聚合物复合材料的旋转模塑成型工艺研究

【作者】 张军；

【导师】 张恒；

【作者基本信息】 郑州大学 ， 材料学， 2007， 博士

【摘要】 旋转模塑是一种以塑料粉末为原料成型中空塑料制品的工艺。由于它具有一些其它成型工艺无法比拟的优点，如成本低、制品无内应力、适合成型大型制品等，一直受到人们的关注。该工艺也存在一些缺点，如制品强度低、工人劳动强度大、成型时间长、原材料种类少及原材料成本高等，限制了旋转模塑工艺的发展。长期以来人们一直都在努力研究适合旋转模塑工艺的新材料并对旋转模塑工艺进行改进，取得了一定的成果。很早就有人提出使用液体聚合物进行旋转模塑生产。液体聚合物与粉末聚合物原料相比具有诸多优点，如液体聚合物增强方式灵活，能够使用长纤维进行增强以提高制品强度等。但是，液体聚合物作为旋转模塑原料在操作过程中会遇到一些困难，主要问题是原料在模具壁上分布不均匀和制品表面产生气泡。这些问题制约了旋转模塑工业中液体聚合物的应用。基于此，本文工作的目标是使用通用型不饱和聚酯树脂为原料研究适用它的旋转模塑成型工艺及长纤维增强技术。同时，本文还对液态发泡树脂体系旋转发泡工艺进行了试验研究，并得到了一些有意义的结论。为进行上述不饱和聚酯树脂旋转模塑试验研究，本文自行设计并制造了双轴可调速旋转模塑机。该设备具有内传动和外传动两条传动路线，分别使模具绕两互相垂直轴旋转。该设备每轴调速范围为0～35r／min，能够满足液体原料在各种转速下的成型试验研究，也可用于企业中小型液体旋转模塑制品的生产。通过不饱和聚酯树脂旋转成型试验研究发现：不饱和聚酯树脂旋转模塑制品存在最大质量问题是壁厚不均匀及表面存在较多气泡，问题的产生与不饱和聚酯树脂的初始黏度和凝胶速度有关。与热固性树脂凝胶曲线相对应可把旋转模塑制品的形成过程分为成型前、成型期、缺陷形成期三个阶段。本文还研究了正交试验研究树脂初始黏度，凝胶速度与制品质量的关系。研究结果表明：树脂的初始黏度影响制品的厚度，树脂的固化速度影响制品壁厚的均匀性，而通过正交试验的方法可为生产一定形状和大小的制品确定合适的工艺参数。本文进行了长纤维增强不饱和聚酯树脂旋转模塑试验研究，试验结果表明：对于长纤维增强旋转模塑制品，制品壁厚均匀性控制不再是主要问题，而制品表面气泡控制是最为主要的工艺难题。针对这一问题，本文设计了试验观察和研究气泡形成过程的装置并进一步研究了气泡的形成机理。研究发现制品表面气泡主要是由于树脂浸润纤维速度不均匀性及树脂浸润纤维的驱动力过小产生的。本文通过增加树脂在模具内的流动通道，改善树脂浸润纤维速度不均匀性，制造出了表面没有气泡的制品。针对长纤维增强时，树脂浸润纤维驱动力过小的问题，本文提出了高速旋转成型技术，并进行了成型工艺试验。试验结果表明，模具高速旋转能够有效减少制品外表面气泡数量，但却在制品内表面产生较多气泡。通过对成型工艺进行仿真模拟，可知这是由于模具旋转速度过高引起的。可通过有限元仿真确定最佳模具旋转速度。论文最后还初步研究了液体原料旋转发泡工艺，进行了成型试验，并研究了工艺参数对发泡泡孔均匀性和大小的影响。试验表明：随着主轴转速的增大，制品外壳气泡数量增多；异氰酸脂和聚醚的质量比接近1∶1，稳定剂质量比一般在0.5-5％之间时能够得到泡孔密度均匀致密的泡沫夹芯。结合本文所做工作及得到的结论，本文有以下几点创新：1)首次使用旋转模塑成型工艺制成了连续纤维增强不饱和聚酯树脂复合材料制品。2)首次研究了连续纤维增强旋转模塑工艺中树脂交联固化的化学变化与旋转运动物理变化的耦合问题，获得有价值的研究结论。3)首次采用提高模具双轴旋转速度的方法，减少长纤维增强时制品表面气泡缺陷。4)首次使用拉格朗日-格拉平流重构算法基于有限单元法对旋转模塑工艺进行仿真模拟，仿真的结果可为制定工艺参数提供理论依据。更多还原

【Abstract】 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.更多还原