The aging principle and prevention of FRPP pipe

(1) The aging appearance of FRPP pipes, fire-fighting steel-plastic composite pipes

FRPP is exposed to natural or artificial conditions, the appearance of deterioration due to the passage of time is called the appearance of plastic aging, often referred to as aging for short.

The aging of FRPP pipes can be manifested as the following manifestations: ①The appearance of plastic products has changed, such as darkening, deformation, cracking or moldy, falling, etc.; ②Changes in physical and chemical functions, such as solubility, glass transition temperature, melt Activity rate and group content, etc.; ③ Changes in mechanical functions, such as tensile strength, impact strength, elongation at cracking, etc.; ④ Changes in electrical functions, such as insulation resistance, dielectric constant, breakdown voltage, etc.

(2) Elements of FRPP pipe aging

The factors that cause FRPP pipe aging are internal and external.

1. Intrinsic elements

(1) The impact of chemical planning

The difficulty of FRPP pipe aging depends on the strength of its chemical bond. Different keys have different key abilities, and they vary greatly. In the polymer molecule, the presence of branches and side groups will reduce the strength of the bond, which makes the aging of the plastic different.

(2) The impact of mobilized state planning

Centralized planning is also an important factor that affects the aging of plastics. There are still amorphous areas in crystalline polymers. The density and crystallinity of the crystalline and amorphous areas are different. The plastic aging reaction occurs only when the reactants (such as oxygen, etc.) enter the polymer plan to have a certain reaction speed, otherwise the aging speed is very slow and only proceeds on the surface. Therefore, the dispersibility of the aging reactants of the plastic into the plastic material varies with its crystallinity and the density of the amorphous area.

2. External elements

The chemical changes caused by external elements of FRPP pipe are mainly:

① Pyrolysis generates oligomers;

②Depolymerization to generate monomer;

③Decompose to release simple compounds;

④ Oxidation or cross-linking.

The external effects of aging plastics can be summarized as physical elements (light, heat, stress, electric field, radiation, etc.), chemical elements (oxygen, ozone, heavy metal ions, chemical media, etc.) and biological elements (microorganisms, molds, etc.). Among the elements that affect the outside world, the three elements of light, oxygen, and heat are the most important. Therefore, the aging of plastics is essentially the generalized effect of light aging, oxygen aging and thermal oxidation of plastic materials.

(3) Prevention and treatment of FRPP pipe aging

The photo-aging of plastics refers to the appearance that the functions of plastics deteriorate over time when they are exposed outdoors. It is usually called "climatic aging".

The essence of "chemical" is the photo-aging of plastics. Among the elements of climate aging, ultraviolet radiation in sunlight is the primary element. The primary method to prevent photo-aging is to participate in light stabilizers.

The oxygen aging of plastic refers to the auto-oxidation reaction that occurs on the molecular chain of the plastic in the presence of oxygen, which has free radical reaction.

Response mechanism. The first way to prevent oxygen aging is to participate in antioxidants

The thermal oxidation of FRPP pipe refers to the degradation reaction of plastic under thermal conditions, which is composed of heat itself or caused by heat propelling light and oxygen. The primary method to prevent thermal oxidation is to participate in thermal stabilizers.