可降解顆粒的聚合物的物理性能取決于諸如重復(fù)單元的組成、鏈的柔性、極性基團(tuán)的存在、分子質(zhì)量、支化度、結(jié)晶度、取向度等幾個(gè)因素。下面具體講解下：

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:

短鏈支化降低了聚合物的結(jié)晶度，而長(zhǎng)鏈支化降低了熔融粘度并且尤其賦予具有拉伸硬化性態(tài)的拉伸粘度。該應(yīng)用材料的特性可以進(jìn)一步通過(guò)共混、以及與其它聚合物共聚、或通過(guò)改變大分子構(gòu)型(如超支化聚合物、星型聚合物、或枝狀聚合物等)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).

任何這種合適的可降解聚合物的特性(例如疏水性、親水性、降解速率，等)可以通過(guò)沿該聚合物鏈引入所選擇的功能性基團(tuán)而修整。用于制備在地下應(yīng)用中有用的可降解顆粒(例如作為酸性前體、流體損失控制顆粒、導(dǎo)引劑、濾餅部分、鉆井液、水泥添加劑等)的常規(guī)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.

為了使用乳液法制備可降解顆粒，一般將可降解聚合物材料如聚(乳酸)溶解于鹵化溶劑如二氯甲烷中以形成聚合物溶液，隨后在充分剪切下向該聚合物溶液加入水和表面活性劑以形成乳液。

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.

該乳液形成之后，通過(guò)真空抽提或水蒸氣抽提將該溶劑從該乳液中除去，在水相中留下基本不含溶劑的聚合物顆粒。然后去除水，并通過(guò)離心、過(guò)濾或噴霧干燥收集顆粒。

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.

同樣，用溶液沉淀法制備可降解顆粒包括將可降解聚合物溶解在水可混溶的溶劑中以形成聚合物溶液。以足夠的剪切將表面活性劑和/或水加入該聚合物溶液，以便該溶劑與聚合物溶液分離，留下基本無(wú)溶劑的聚合物顆粒，所述聚合物顆粒可以用已經(jīng)討論過(guò)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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