Control of Nano-Scale Structuring and Reinforcement in Rotational Molding of Polyethylene
Control of Nano-Scale Structuring and Reinforcement in Rotational Molding of Polyethylene
复制标题
聚乙烯旋转成型中纳米级结构化和增强的控制
DOI：
10.1002/masy.201051045
复制
发表时间：
2010
影响因子：
--
通讯作者：
Wagner MH
中科院分区：
文献类型：
--
作者：
Kulikov O;Hornung K;Wagner MH
用于滚塑成型的聚乙烯（PE）树脂通常具有小于0.8 mm的粒度，并用作粉末或微丸。在旋转模具中加热期间，这些颗粒熔化并合并成一片。滚塑工艺的缺点是循环时间长，影响生产速率并增加聚合物的热降解。滚塑中的问题之一是在PE粉末的烧结过程中捕获的气泡，这降低了所生产的制品的机械强度。我们建议使用PEG与柠檬酸的反应混合物作为加工添加剂（PA）来滚塑等级的PE。硅灰和乙烯基硅烷可以是添加剂包的其他成分。PA加速了PE颗粒的烧结，并大大减少了熔体中的气泡数量，但在高浓度下，它阻碍了颗粒的流动。粉末的特征在于低流动性，而微丸对于滚塑具有太高的流动性。为了改进滚塑工艺，我们建议通过在降低的温度下挤出包含PA的PE树脂并在露天造粒来制造微丸。相同的PA降低了挤出压力，抑制了造粒过程中的流动不稳定性，并将微丸的流动性调节到最佳状态，加速了PE颗粒的烧结，并从PE熔体中去除了气泡。所观察到的改进的机制进行了讨论。
Polyethylene (PE) resins used for Rotational Molding have usually particle sizes less than 0.8 mm and used as powders or micro‐pellets. During heating in a rotating mould, these particles get fused and merge into one piece. A disadvantage of the rotomolding process is long cycle times that affect the production rate and increase thermal degradation of the polymer. One of the problems in rotomolding is bubbles of gasses trapped during sintering of the PE powders which reduce mechanical strength of the article produced. We propose to use reacting mixtures of PEG with citric acid as Processing Additive (PA) to rotomolding grades of PE. Silica fume and vinyl‐silanes can be other ingredients of the additive package. The PA accelerates sintering of the PE particulates and greatly reduces number of bubbles in the melt but at high concentrations it impedes flow of the particles. Powders are characterized by low flowability while micro‐pellets have too high flowability for rotomolding. To improve the rotomolding process we propose to fabricate micro‐pellets by extrusion of PE resins comprising the PA at reduced temperatures and pelletizing in open air. The same PA reduces extrusion pressure and suppresses flow instabilities during pelletizing as well as adjusts flowability of micro‐pellets to optimum, accelerates sintering of the PE particulates and removes bubbles from the PE melt. Mechanisms of the observed improvements are discussed.