PP板材的化學穩(wěn)定性

Chemical stability of PP sheet

PP板材具有******的力學性能，其屈服強度、拉伸強度、壓縮強度和硬度、彈性模量等都比HDPE高，但在室溫及低溫下，由于本身的分子結構規(guī)整度高，所以沖擊強度較差。PP的抗彎曲疲勞強度突出，具有******的耐熱性，耐摩擦性能也較***，但在低于一35℃的溫度下會發(fā)生脆裂，耐寒性 不如聚乙烯。PP的化學穩(wěn)定性很***，除能被濃硫酸及濃硝酸侵蝕外，對其他各種化學試劑都比較穩(wěn)定，但是低分子量的脂肪烴、芳香烴和氛化烴等能使聚丙烯軟化和溶脹。PP的高頻***緣性 能******，由于它幾乎不吸水，故***緣性能不受濕度的影響，它有較高的介電系數(shù)，可以用來制作 受熱的電氣***緣制品，它的擊穿電壓也很高，適合用作電氣配件等。

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板材熱穩(wěn)定性差，對光、熱很敏感，加入穩(wěn)定化助劑則可改善其老化性能。PP制品對缺口敏感，因此在設計模具時必須注意避免尖角存在，否則會產(chǎn)生應力集中現(xiàn)象，影響產(chǎn)品的使用壽命。推薦閱讀：PP板材加工注意事項

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、擠塑、吹塑、真空熱成型、涂覆、旋轉成型、熔接、機加工、電鍍和發(fā)泡等，并可在金屬表面噴涂。即長時間與金屬壁接觸時，會發(fā)生分解、炭化，所以在加工過程中要注意不要使物料長期停滯在料筒里。在注塑成型時，為了便于塑化，較***加長注塑機的分流梭。若要縮短注塑周期，也可適當提高注塑溫度，但掌握在以不發(fā)生嚴重降解為限。注塑時選擇適當?shù)哪厥欠浅Ｖ匾?，因為聚丙烯分子容易發(fā)生取向，分子取向后會發(fā)生應變并降低沖擊強度，而取向現(xiàn)象在低溫高壓注射時較容易產(chǎn)生，因此溫度不能過低(模溫較***在8OC 左右，不可低于50℃)，否則成型品表面光澤較差，或者產(chǎn)生熔接痕等缺陷，當然，模溫也不能過高，模溫過高會使制品產(chǎn)生翹曲現(xiàn)象。PP板材的二次加工性能很***，其印刷性能***于聚乙烯，制品 可燙金、印花、黏合等，電鍍用于儀器、儀表、電子等的裝飾件。

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薄膜透明而有光澤，對水蒸氣和空氣的滲透性小，按加工工藝可分為吹塑薄膜、流延薄 膜、雙向拉伸薄膜等;注塑制品可用作汽車、電器、機械、儀表、無線電、紡織、***防等工程配件，也可用于日用品、周轉箱、醫(yī)療衛(wèi)生器材、建筑材料;擠塑制品，有管材、型材、單絲、漁用繩索、打包 帶、捆扎繩、編織袋、纖維、復合涂層、片材、板材等;吹塑中空成型制品，有各種小型容器等;旋轉 成型可制造各種***型化工儲槽、容器、罐等;其他制品有鈣塑板、層壓板、合成紙、高發(fā)泡結構泡 沫體等。

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.