Polypropylene (PP) is a non-toxic, odorless, tasteless, milky-white, highly crystalline polymer, which is one of the lightest varieties of all plastics at present. It is particularly stable to water, with a water absorption rate of only 0.01% in water. At the same time, it has good heat resistance, and the products can be sterilized at temperatures above 100 °C, and will not deform at 150 °C without external force. However, if you want to use it at a higher temperature, and it will inevitably be disturbed by external forces, problems such as warping and deformation will occur, and then it needs to be heat-resistant and stiffened. Generally speaking, the methods of stiffening and heat-resistant modification of PP mainly include the following:

filling modification

Filling modification generally refers to adding calcium carbonate, talc, mica powder, kaolin, wollastonite powder, barium sulfate and other non-metallic mineral powder materials or other materials to PP resin, which can not only significantly improve the rigidity and heat resistance of PP , Improve dimensional stability, high temperature creep resistance, hardness, etc., most of which can also play a role in incremental cost reduction.

In the filling modification, the first thing to do is to solve the problem of whether the distribution and dispersion of the filler in the PP resin matrix are uniform, and at the same time, the filler needs to be properly surface treated to have good affinity with polypropylene. It can be said that the surface treatment method of filler and the choice of surface treatment agent are the keys to determine the success or failure of filling modification. Today, many packing manufacturers can provide models of different specifications for selection according to customer requirements. If the product quality requirements are higher, the filler masterbatch can be selected.

Enhanced modification
 
Reinforcement modification generally refers to the addition of fibrous materials to PP to increase its strength, although fillers, especially fillers with large diameter-to-thickness ratios, have the same effect. The fibrous materials used to strengthen PP mainly include glass fiber, carbon fiber, inorganic and metal whiskers and so on. Among them, glass fiber is the main reinforcing material, which can significantly improve the tensile strength, flexural strength and modulus (rigidity), heat resistance, and dimensional stability of PP plastics. Glass fiber reinforced PP can be used as engineering plastics in many occasions, such as fan blades, heater grilles, impeller pumps, lampshades, electric furnaces and heater casings, etc. Such as today, the popular long glass fiber reinforced PP.

Nucleation modification
 
Nucleation modification generally refers to adding a small amount of nucleating agent to PP to significantly increase the crystallization speed, crystallization rate and crystal fine ratio of PP to achieve rigidity and heat resistance modification of PP. PP nucleating agents include inorganic nucleating agents such as ultrafine talc, silicon dioxide, and nano-calcium carbonate, and organic nucleating agents represented by sorbitol and its derivatives. Inorganic nucleating agents often have a certain influence on the gloss and transparency of products, while organic nucleating agents can significantly improve the transparency and surface gloss of products.

With the continuous improvement of people's living standards, it will inevitably bring about different requirements and improvements in various aspects such as culture, entertainment, food, medical care, materials, and room decoration. Many items in the market are increasingly using transparent materials. Transparent PP has more characteristics than ordinary PP, PVC, PET, PS, etc., and has more advantages and development prospects. In 2016, the consumption of transparent PP in my country was about 1.2 million tons, which is one of the types of PP with rapid growth in demand in recent years.