可降解颗粒的聚合物物理性能决定于什么？

可降解颗粒的聚合物的物理性能取决于诸如重复单元的组成、链的柔性、极性基团的存在、分子质量、支化度、结晶度、取向度等几个因素。下面具体讲解下：

The physical properties of polymers with degradable particles depend on several factors, such as the composition of repeating units, the flexibility of chains, the existence of polar groups, molecular weight, degree of branching, degree of crystallinity, and degree of orientation. The following are explained in detail:

短链支化降低了聚合物的结晶度，而长链支化降低了熔融粘度并且尤其赋予具有拉伸硬化性态的拉伸粘度。该应用材料的特性可以进一步通过共混、以及与其它聚合物共聚、或通过改变大分子构型(如超支化聚合物、星型聚合物、或枝状聚合物等)而修整。

The short chain branching reduces the crystallinity of the polymer, while the long chain branching reduces the melt viscosity and especially endows the tensile viscosity with tensile hardening property. The properties of the applied material can be further modified by blending, copolymerization with other polymers, or changing the macromolecular configuration (such as hyperbranched polymer, star polymer, or dendritic polymer).

任何这种合适的可降解聚合物的特性(例如疏水性、亲水性、降解速率，等)可以通过沿该聚合物链引入所选择的功能性基团而修整。用于制备在地下应用中有用的可降解颗粒(例如作为酸性前体、流体损失控制颗粒、导引剂、滤饼部分、钻井液、水泥添加剂等)的常规方法尤其包括乳液法和溶液沉淀法。

The characteristics of any such suitable degradable polymer (such as hydrophobicity, hydrophilicity, degradation rate, etc.) can be modified by introducing selected functional groups along the polymer chain. Conventional methods for preparing degradable particles useful for underground applications (such as acid precursors, fluid loss control particles, guiding agents, filter cake parts, drilling fluids, cement additives, etc.) include, in particular, the lotion method and the solution precipitation method.

为了使用乳液法制备可降解颗粒，一般将可降解聚合物材料如聚(乳酸)溶解于卤化溶剂如二氯甲烷中以形成聚合物溶液，随后在充分剪切下向该聚合物溶液加入水和表面活性剂以形成乳液。

In order to prepare degradable particles by the lotion method, degradable polymer materials such as poly (lactic acid) are generally dissolved in halogenated solvents such as dichloromethane to form a polymer solution, and then water and surfactant are added to the polymer solution under full shear to form a lotion.

该乳液形成之后，通过真空抽提或水蒸气抽提将该溶剂从该乳液中除去，在水相中留下基本不含溶剂的聚合物颗粒。然后去除水，并通过离心、过滤或喷雾干燥收集颗粒。

After the lotion is formed, the solvent is removed from the lotion by vacuum extraction or water vapor extraction, leaving polymer particles basically free of solvent in the water phase. The water is then removed and the particles are collected by centrifugation, filtration or spray drying.

同样，用溶液沉淀法制备可降解颗粒包括将可降解聚合物溶解在水可混溶的溶剂中以形成聚合物溶液。以足够的剪切将表面活性剂和/或水加入该聚合物溶液，以便该溶剂与聚合物溶液分离，留下基本无溶剂的聚合物颗粒，所述聚合物颗粒可以用已经讨论过的相同方法收集。

Similarly, the preparation of degradable particles by solution precipitation includes dissolving the degradable polymer in a water miscible solvent to form a polymer solution. The surfactant and/or water are added to the polymer solution with sufficient shear so that the solvent is separated from the polymer solution, leaving essentially solvent-free polymer particles that can be collected in the same way as discussed.

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