PP板材的化学稳定性

　

PP板材的化学稳定性

Chemical stability of PP sheet

PP板材具有******的力学性能，其屈服强度、拉伸强度、压缩强度和硬度、弹性模量等都比HDPE高，但在室温及低温下，由于本身的分子结构规整度高，所以冲击强度较差。PP的抗弯曲疲劳强度突出，具有******的耐热性，耐摩擦性能也较***，但在低于一35℃的温度下会发生脆裂，耐寒性 不如聚乙烯。PP的化学稳定性很***，除能被浓硫酸及浓硝酸侵蚀外，对其他各种化学试剂都比较稳定，但是低分子量的脂肪烃、芳香烃和氛化烃等能使聚丙烯软化和溶胀。PP的高频***缘性 能******，由于它几乎不吸水，故***缘性能不受湿度的影响，它有较高的介电系数，可以用来制作 受热的电气***缘制品，它的击穿电压也很高，适合用作电气配件等。

PP sheet has excellent mechanical properties, its yield strength, tensile strength, compressive strength, hardness, modulus of elasticity are higher than HDPE, but at room temperature and low temperature, due to its high molecular structure regularity, the impact strength is poor. PP has outstanding flexural fatigue strength, good heat resistance and good friction resistance, but brittle cracks occur at temperatures below 135 C, and its cold resistance is inferior to that of polyethylene. The chemical stability of PP is very good. Besides being eroded by concentrated sulfuric acid and nitric acid, it is relatively stable to other chemical reagents, but low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons and atmospheric hydrocarbons can soften and swell PP. PP has excellent high frequency insulation performance, because it hardly absorbs water, so its insulation performance is not affected by humidity. It has a high dielectric coefficient and can be used to make heated electrical insulation products. Its breakdown voltage is also very high, and it is suitable for use as electrical accessories.

PP板材热稳定性差，对光、热很敏感，加入稳定化助剂则可改善其老化性能。PP制品对缺口敏感，因此在设计模具时必须注意避免尖角存在，否则会产生应力集中现象，影响产品的使用寿命。推荐阅读：PP板材加工注意事项

PP sheet has poor thermal stability and is sensitive to light and heat. Adding stabilizer can improve its aging performance. PP products are sensitive to notches, so we must pay attention to avoid sharp corners in the design of dies, otherwise stress concentration will occur, affecting the service life of products. Recommended Reading: Notes for PP Plate Processing

PP板材的成型方法很多，如注塑、挤塑、吹塑、真空热成型、涂覆、旋转成型、熔接、机加工、电镀和发泡等，并可在金属表面喷涂。即长时间与金属壁接触时，会发生分解、炭化，所以在加工过程中要注意不要使物料长期停滞在料筒里。在注塑成型时，为了便于塑化，较***加长注塑机的分流梭。若要缩短注塑周期，也可适当提高注塑温度，但掌握在以不发生严重降解为限。注塑时选择适当的模温是非常重要的，因为聚丙烯分子容易发生取向，分子取向后会发生应变并降低冲击强度，而取向现象在低温高压注射时较容易产生，因此温度不能过低(模温较***在8OC 左右，不可低于50℃)，否则成型品表面光泽较差，或者产生熔接痕等缺陷，当然，模温也不能过高，模温过高会使制品产生翘曲现象。PP板材的二次加工性能很***，其印刷性能***于聚乙烯，制品 可烫金、印花、黏合等，电镀用于仪器、仪表、电子等的装饰件。

There are many forming methods for PP sheet, such as injection molding, extrusion, blow molding, vacuum thermoforming, coating, rotating forming, welding, machining, electroplating and foaming, and spraying on metal surface. That is, when contacting with the metal wall for a long time, decomposition and carbonization will occur, so in the process of processing, care should be taken not to make the material stagnate in the barrel for a long time. In order to facilitate plasticization, the shunt shuttle of injection moulding machine can be lengthened. In order to shorten the injection cycle, the injection temperature can also be increased appropriately, but only in the absence of serious degradation. It is very important to choose the appropriate mold temperature for injection moulding, because polypropylene molecule is prone to orientation, strain and impact strength will occur after molecular orientation, and orientation phenomenon is more prone to occur at low temperature and high pressure injection, so the temperature should not be too low (the mold temperature is better at about 8OC, not less than 50 C), otherwise, the surface gloss of the moulded product is poor, or weld marks and other defects will occur. Of course, the die temperature can not be too high, too high die temperature will cause warpage of products. PP sheet has good secondary processing performance, and its printing performance is better than polyethylene. Products can be stamped, printed and bonded. Electroplating is used for decorative parts such as instruments, meters and electronics.

PP薄膜透明而有光泽，对水蒸气和空气的渗透性小，按加工工艺可分为吹塑薄膜、流延薄 膜、双向拉伸薄膜等;注塑制品可用作汽车、电器、机械、仪表、无线电、纺织、***防等工程配件，也可用于日用品、周转箱、医疗卫生器材、建筑材料;挤塑制品，有管材、型材、单丝、渔用绳索、打包 带、捆扎绳、编织袋、纤维、复合涂层、片材、板材等;吹塑中空成型制品，有各种小型容器等;旋转 成型可制造各种***型化工储槽、容器、罐等;其他制品有钙塑板、层压板、合成纸、高发泡结构泡 沫体等。

PP film is transparent and lustrous, and has little permeability to water vapor and air. According to the processing technology, it can be divided into blown film, casting film, biaxial stretching film, etc. Injection products can be used as automobile, electrical appliances, machinery, instrumentation, radio, textile, national defense and other engineering accessories, as well as daily necessities, switchboxes, medical and health equipment, building materials; extruded products, including pipes, shapes, etc. Material, monofilament, fishing rope, packing belt, strapping rope, woven bag, fiber, composite coating, sheet, plate, etc. blow molding hollow molding products, all kinds of small containers, etc.; rotary molding can produce various large chemical tanks, containers, cans, etc.; other products include calcium plastic board, laminate, synthetic paper, high foaming structure foam, etc.