在PVC发泡板材挤出过程中，碰到的问题基本可以归为4类，一是稳定性问题；二是熔体强度问题；三是润滑问题；四是分散问题。这四类问题特别是前三类问题会相互制约，交叉影响。从表面现象看有时稳定性不足，会影响整个板面，板面发黄，发泡板材脆性大。熔体强度不足会导致发泡板泡孔大，纵切面泡很长。判断熔体强度是否不足，最直接的办法是到三辊后面用手指按压包在中辊上的板材，熔体强度好按压时能感觉到弹性。若按压后很难弹起，说明熔体强度较差。因为螺杆结构和冷却方式差别较大，很难判断温度是否合理，一般来说，在挤出机允许的负荷内，3—5区温度以低为好。润滑剂分为外润滑剂和内润滑剂，外润滑剂有利于脱模，对板材表面的光洁性有好处，外滑太少，挤出机5区温度不易控制，易升温，这会导致合流芯温度高，板材中间出现大泡、串泡、发黄等问题，板材表面也不光滑；外滑多，析出会变得严重，表现在模具内的结垢和板材表面外滑的析出，也会表现为某些个别现象在板面上不定期的来回移动。内滑有利于塑化和熔体的流动性，内滑不足板面难以控制厚度，表现为板材中间厚两边薄；内滑多，易出现合流芯温度高的现象。分散不好会带来板材表面不光滑的现象。
The problems encountered in extrusion process of PVC foamed sheet can basically be classified into 4 categories, one is stability, two is melt strength, three is lubrication, and four is dispersion. These four kinds of problems, especially the first three types of problems, will be mutually restricted and cross influence. From the surface phenomenon, sometimes the stability is insufficient, which will affect the whole surface of the plate, the surface of the plate is yellow, and the foamed sheet is brittle. Melt strength deficiency will lead to foam foaming plate, longitudinal long pimple. The most direct way to judge whether or not the melt strength is enough is to press the fingers on the middle rolls after pressing the three rolls, which can feel the elasticity when the melt is strong and press. It is difficult to start if pressed, indicating that the strength of the melt is poor. Because the screw structure and cooling way are quite different, it is difficult to determine whether the temperature is reasonable. Generally speaking, in the allowable load of the extruder, the temperature in zone 3 to 5 is low. The lubricant is divided into external lubricant and lubricant, lubricant for release, is good for the smooth surface of the plate, the outer slide is too small, the extruder 5 zone temperature is not easy to control, easy to heat up, it will lead to the confluence of the core temperature is high, the plate appeared in the middle of bulla, on issues such as global, yellow, plate surface not smooth; the outer slide, precipitation will become serious, in the mold of precipitation fouling and plate surface smooth, also showed some individual phenomenon on the surface of back and forth in the irregular movement. The internal sliding is favorable for plasticization and melt flow. The inner slide is not enough to control the thickness of the plate. It is shown that the thickness of the plate is thick and thin on both sides, and the inner sliding is much, which is easy to appear the phenomenon of high temperature of the confluent core. Poor dispersion will lead to the unsmooth surface of the plate.