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首页> 外文会议>10th International Conference on Additives 2001: Plastics for the New Millennium, 10th, Mar 18-21, 2001, Hilton Head Island, South Carolina >STABILISER PARTITIONING AND MIGRATION IN POLYMER BLENDS AND HETEROPHASIC COPOLYMERS
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STABILISER PARTITIONING AND MIGRATION IN POLYMER BLENDS AND HETEROPHASIC COPOLYMERS

机译：聚合物共混物和异规共聚物中的稳定剂分配和迁移

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The solubility and diffusion rate of an additive in a polymer are critical to the performance of the additive. The solubility is the maximum amount of additive which can be present in the polymer at equilibrium at any given temperature, and any concentration above this represents supersaturation. It is a common feature of polymers that supersaturated additives migrate to the surface and precipitate there, forming an unsightly "bloom" and reducing the additive's effectiveness. The rate of blooming is controlled by the diffusion coefficient of the additive. If an additive is dissolved in the polymer at a concentration below saturation, then it can be lost into air only by evaporation, which is usually very slow, because of the low vapour pressure of typical stabilisers. However, if the polymer is in contact with a liquid which is a solvent for the additive, then loss will occur by leaching, at a rate controlled by the diffusion of the additive in the polymer. With this in mind, we can draw a number of conclusions about the behaviour of additives in polymers which have biphasic morphologies. 1. Additives are significantly more soluble in the soft, low T_g, high free-volume polymers typical of toughened polymers. The effect increases with temperature, and extrapolation of measured data suggests that stabilising additives are almost completely concentrated in the rubber phase at processing temperatures, and often significantly so even at ambient temperatures. 2. The effect of partitioning on thermo-oxidative stability will depend on the rate of migration of the additive between phases in response to its consumption. This may be a problem at high temperatures; at ambient temperatures oxidation is slow enough that redistribution of additives will be rapid, unless one phase of the polymer is glassy. The effect of partitioning of UV absorbers is less clear and must depend in part on the balance of chemical and physical action of the additive. 3. The presence of a soft phase will increase the overall solubility of an additive, and this will reduce the possibility of blooming and allow more additive to be used without loss. However, if the additive concentration becomes supersaturated, blooming will become much more rapid than in the unmodified polymer, because of the higher diffusion rate; this effect will be much more marked in polymers like the PEBEs when the soft phase fraction is above the percolation threshold. 4. Since the soft phase increases diffusion rate, it will also increase the susceptibility of toughened polymers to loss of additives by leaching; again, this effect will be much more marked when the soft phase fraction is above the percolation threshold.
机译：添加剂在聚合物中的溶解度和扩散速率对添加剂的性能至关重要。溶解度是在任何给定温度下在平衡状态下可存在于聚合物中的最大添加剂量，高于此的任何浓度均表示过饱和。聚合物的一个共同特征是过饱和添加剂迁移到表面并在那里沉淀，形成难看的“水华”并降低添加剂的有效性。起霜率由添加剂的扩散系数控制。如果添加剂以低于饱和的浓度溶解在聚合物中，则由于典型的稳定剂的蒸气压低，它只能通过蒸发而损失到空气中，这通常非常缓慢。但是，如果聚合物与作为添加剂的溶剂的液体接触，则损失将通过浸出发生，损失的速率由添加剂在聚合物中的扩散控制。考虑到这一点，我们可以得出关于具有双相形态的聚合物中添加剂行为的许多结论。 1.添加剂在增韧聚合物典型的柔软，低T_g，高自由体积聚合物中的溶解度更高。该影响随温度增加而增加，对测量数据的推断表明，稳定添加剂在加工温度下几乎完全集中在橡胶相中，即使在环境温度下也常常如此。 2.分配对热氧化稳定性的影响将取决于添加剂根据其消耗而在各相之间迁移的速率。在高温下这可能是个问题。在环境温度下，除非聚合物的一相是玻璃态的，否则氧化足够缓慢，以至于添加剂的重新分布很快。紫外线吸收剂的分配效果不太清楚，必须部分取决于添加剂的化学和物理作用之间的平衡。 3.软相的存在将增加添加剂的整体溶解度，这将减少起霜的可能性，并允许使用更多的添加剂而不会造成损失。但是，如果添加剂浓度变得过饱和，则由于较高的扩散速率，起霜将比未改性的聚合物快得多。当软相分数高于渗透阈值时，这种效果在像PEBE这样的聚合物中将更为明显。 4.由于软相增加了扩散速率，因此也将增加增韧聚合物对通过浸出而损失添加剂的敏感性。再次，当软相分数高于渗滤阈值时，这种影响将更加明显。

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