Flame retardant transformation of PE film for agricultural greenhouses: test data of magnesium hydroxide weather resistance

In the vast fields, agricultural greenhouses are like "transparent armor" covering crops, which must not only resist the invasion of storms and rainstorms, but also resist the test of scorching sun. However, the balance between flame retardancy and weather resistance of traditional polyethylene (PE) greenhouse films is always like walking a tightrope - although adding halogen flame retardants can extinguish fires, it makes the film material as brittle as dead leaves under ultraviolet rays and acid and alkali erosion; the pursuit of weather resistance requires sacrificing fire safety, and an accidental fire may turn the entire farmland into scorched earth. It was not until magnesium hydroxide appeared as a "natural defender" and built a double line of defense of flame retardancy and weather resistance in PE film through molecular-level technological innovation that this battle concerning life and harvest ushered in the dawn.

1. The life and death test field of greenhouse film

Agricultural greenhouse PE film needs to face three extreme tests:

Flame attack: Winter heating equipment accidentally ignites, traditional PE film molten droplets splash, and the speed of fire spread is comparable to grassland wildfire;

Ultraviolet strangulation: The average annual ultraviolet radiation exceeds 120kJ/m², ordinary flame retardants accelerate photooxidation, and the film material becomes brittle and cracks within half a year;

Chemical encirclement: Fertilizer volatilization and acid rain erosion cause micropores on the surface of the film material, and the light transmittance plummets from 90% to 60%, and the photosynthetic efficiency of crops is halved.

The measured data of a North China agricultural base shows that after 8 months of use, the tensile strength of the unmodified PE film drops sharply from 20MPa to 9MPa, the oxygen index is only 17%, and it burns completely within 3 seconds when exposed to open flames. The turning point of this crisis is hidden in the molecular-level weather resistance test data of magnesium hydroxide.

2. Weathering code: Molecular evolution of magnesium hydroxide

1. UV protection system

Magnesium hydroxide is transformed into an "optical shield" in PE film:

Ultraviolet absorption: The absorption rate of nano-particles to 280-400nm ultraviolet rays exceeds 92%, which is equivalent to applying "molecular sunscreen" to the film material;

Light reflection: The surface of the modified magnesium hydroxide forms a micron-level concave-convex structure, which reflects 30% of the incident light back to the atmosphere, and the temperature rise of the film body is slowed down by 40%;

Free radical capture: The active magnesium oxide produced by decomposition captures photooxidation free radicals, delays the breakage of PE molecular chains, and the elongation at break retention rate jumps from 50% to 85%.

2. Chemical corrosion firewall

Through the compound modification of silane coupling agent (KH-560) and zinc stearate, magnesium hydroxide constructs triple protection in the PE matrix:

Acid-base buffer: Release OH⁻ ions to neutralize H⁺ when encountering acid rain, the local pH value is stabilized at 6.5-8.0, and the corrosion rate of the membrane material is reduced by 75%;

Micropore plugging: 3.1 micron particles accurately fill the gaps between PE molecules, ammonia permeability decreases by 3 times, and fertilizer volatilization damage is reduced by 60%;

Antibacterial barrier: Chitosan extracted from shrimp shells is grafted onto the surface of particles to inhibit mold growth, and the biodegradation rate is reduced from 0.3mm/year to 0.05mm/year.

3. Actual data: from laboratory to 10,000 acres of fertile fields

1. Accelerated aging test

Simulate 5 years of outdoor environment in a xenon lamp aging box (radiation 1500MJ/m²):

Light transmittance: initial value 91% → 88% after 5 years, attenuation rate is only 0.6%/year, which is 2 times better than the industry standard;

Mechanical properties: tensile strength dropped from 18.2MPa to 16.5MPa, elongation at break from 620% to 580%, toughness comparable to that of a newborn vine;

Flame retardant durability: oxygen index slightly dropped from 28.3% to 27.8%, vertical burning time is still <30 seconds, and passed UL94 V-0 certification.

2. Actual test in extreme environment

Comparative test deployed in a desert farm in Inner Mongolia:

50℃ high temperature exposure: the surface temperature of the modified PE film is 12℃ lower than that of the conventional film, and the temperature difference fluctuation in the greenhouse is compressed from ±8℃ to ±3℃;

8-level wind and sand impact: the puncture resistance of the film material remains at 38kJ/m², and the breakage rate is reduced from 23% to 5%;

-30℃ extreme cold: the bending radius exceeds the 3D limit and passes the 200,000 folding test without cracks.

4. Cost account: save three bags of fertilizer per mu per year

Traditional halogen flame retardant film is replaced 1.2 times per year, while magnesium hydroxide modified film is free of replacement for 3 years:

Direct cost: the unit price of film material increases by 15%, but the life cycle cost decreases by 40%, and the average annual saving per mu exceeds 200 yuan;

Hidden benefits: the increase in light transmittance drives a 12% increase in crop yields, and the reduction in pests and diseases reduces pesticide expenditures by 30%;

Environmental value: halogen-free release reduces the content of heavy metals in the soil by 90%, which complies with the EU RoHS and REACH dual certifications.

The case of Shandong Shouguang Vegetable Base shows that after the transformation of 1,000 mu of greenhouses, the annual reduction of film material waste is 38 tons, and the reduction in carbon dioxide emissions is equivalent to planting 3,400 trees.

5. Future battlefield: self-repair and intelligent response

This agricultural material revolution is moving towards a higher dimension:

4D self-healing film: microencapsulated magnesium hydroxide combined with shape memory polymer, scratch self-repair rate>85%, breakage rate after typhoon drops by another 70%;

Light and temperature control: electron beam lithography builds photonic crystal structure on the film surface, reflects infrared in summer, absorbs heat in winter, and intelligently adjusts greenhouse temperature by ±5℃;

Internet of Things sensing: embedded cadmium selenide quantum dots, volatile substances of pests and diseases stimulate surface fluorescence, and warn of crop diseases 14 days in advance.

The weather resistance data of magnesium hydroxide in agricultural greenhouse PE film has rewritten the industry conclusion that "flame retardancy and durability cannot be achieved at the same time". When the transmittance of 88% and the oxygen index of 27.8% meet in the five-year aging report, this technological long march across molecules and fields proves that true agricultural protection can not only be an enemy of flames, but also dare to confront time. In the future, every inch of membrane material that passes rigorous testing will be the most gentle promise to the earth and life.