1、填料过多。

1. Too much filler.

由于目前市场上石塑电梯门套的价格低，原材料价格又在上涨，很多石塑电梯门套厂家都在降低成本上着手。而正规的石塑电梯门套厂家都是在不降低质量的前提下，通过配方的优化组合降低了成本;有些厂家却在降低成本的同时也降低了制品质量。

Due to the low price of stone plastic elevator door pocket in the market and the rising price of raw materials, many stone plastic elevator door pocket manufacturers are starting to reduce costs. The regular stone plastic elevator door pocket manufacturers reduce the cost through the optimal combination of formulas without reducing the quality; Some manufacturers have reduced the quality of products while reducing the cost.

2、抗冲击改性剂的数量及添加种类。

2. Quantity and type of impact modifier.

在应力作用下，抗冲击改性剂能够提高聚氯乙烯破裂的总能量。目前，CPE、ACR、MBS、 abs、EVA等是硬质聚氯乙烯的抗冲击改性剂的主要品种，其中CPE、EVA、ACR改性剂的分子结构中不含双键，耐候性能好，适宜做户外建筑材料，它们与PVC共混，能有效的提高硬聚氯乙烯的抗冲击性能、加工性、耐候性及在一定范围内提高焊角强度。

Under the action of stress, the impact modifier can increase the total energy of PVC rupture. At present, CPE, ACR, MBS, ABS and EVA are the main varieties of impact modifiers for rigid polyvinyl chloride. Among them, CPE, EVA and ACR modifiers do not contain double bonds in their molecular structure and have good weather resistance. They are suitable for outdoor building materials. Their blending with PVC can effectively improve the impact resistance, processability and weather resistance of rigid polyvinyl chloride and improve the fillet strength in a certain range.

3、稳定剂过多或过少。

3. Too much or too little stabilizer.

稳定剂的作用是抑制降解，或与释放出的氯化氢反应以及防止聚氯乙烯加工时变色。稳定剂用量多少也会对型材的抗冲击强度造成影响，过多或过少都会造成型材强度降低引起型材发脆现象。

The function of stabilizer is to inhibit degradation or react with released hydrogen chloride and prevent discoloration of PVC during processing. The amount of stabilizer will also affect the impact strength of the profile. Too much or too little will reduce the strength of the profile and cause the embrittlement of the profile.

4、外润滑剂用量过多。

4. Excessive amount of external lubricant.

外润滑剂与树脂相溶性较低，能够促进树脂粒子间的滑动，从而减少摩擦热量并推迟熔化过程，润滑剂的这种作用在加工过程早期(也就是在外部加热作用和内部产生的摩擦热使树脂完全熔化和熔体中树脂失去识别特征之前)是的。

The compatibility between the external lubricant and the resin is low, which can promote the sliding between the resin particles, so as to reduce the friction heat and delay the melting process. This effect of the lubricant is the largest in the early stage of the processing process (that is, before the external heating and internal friction heat make the resin completely melt and the resin in the melt lose its recognition characteristics).

5、热混加料顺序，温度设值以及熟化时间对型材的性能也有决定性的因素。

5. The hot mixing feeding sequence, temperature setting value and curing time also have decisive factors on the properties of profiles.

PVC-U配方的组分很多，所选择加料顺序应有利于发挥每种助剂的作用，并有利于提高分散速度，而避免其不良的协同效应，助剂的加料顺序应有助于提高助剂的相辅相成效果，克服相克相消的作用，使用在PVC树脂中分散的助剂，充分进入PVC树脂内部。

PVC-U formula has many components. The selected feeding sequence should be conducive to giving full play to the role of each additive and improving the dispersion speed to avoid its adverse synergistic effect. The feeding sequence of additives should help to improve the complementary effect of additives, overcome the function of eliminating each other, and use the additives dispersed in PVC resin to fully enter the interior of PVC resin.