Anti-Aging Solutions for Agricultural Covering Materials

I. Six Categories, Six Completely Different Aging Propositions

The six categories below, though all called "agricultural film," have almost no overlap in failure mechanism, assessment metrics and formulation direction. This is why Tiangang studies agricultural covering materials as six separate technical lines.

Note the last row: shade net is the only category where "color also matters" - it needs good looks and color fastness; while greenhouse and mulch films never look at color, only at mechanical performance and light-transmission retention. This is the most easily misleading point when selecting.

II. Accelerated Aging: Why Tiangang Promotes Xenon over QUV

When it comes to weathering, the most common client question is: "Can you run a QUV test?" Behind this is a widespread misunderstanding - QUV and xenon are not the same, and their results are not interchangeable.

The industry standard has already fixed the method. The method specified in "T/CPPIA 12-2021 Judgment of Weather Resistance of Agricultural Greenhouse Film Affected by Sulfur/Chlorine-Containing Pesticides" is: after the specimen is treated with sulfur- or chlorine-containing pesticide contact (fumigation or immersion), it undergoes xenon-arc artificial-climate aging per GB/T 16422.2, another group serves as control, and then tensile properties are tested per GB/T 1040.3 and retention calculated. The standard has 19 drafting units, one of which is Beijing Tiangang Auxiliary (the drafter includes Qin Lijie, Secretary-General of the China Society of Agricultural Plastics Application Technology). So for agricultural film, "run a QUV test" actually does not answer the industry judgment standard.

Tiangang Technology Center (Beijing) is equipped with multiple xenon artificial-environment accelerated-aging chambers (WOM), QUV fluorescent-UV aging chambers, thermo-oxidative aging ovens and supporting mechanical and optical analysis equipment, and under the recognition of the China National Light Industry Council has established the "China Light Industry Plastics Products Weathering Engineering Technology Research Center," and under CPPIA recognition has established the "China Plastics Products Weathering Technology Laboratory" (the country's first dedicated laboratory in this field); the testing center is CNAS-accredited. Two outdoor exposure test bases in Guangzhou and Beijing serve as the final calibration for accelerated aging.

III. What Is Really Harsh Is Not UV, but High Sulfur, High Chlorine and High Temperature

Simple UV aging is the "entry-level question" for the entire plastics-additive industry. What pushes agricultural film to truly harsh conditions is three superimposed factors - this is also why Tiangang studies agricultural covering materials as a separate project.

1. High sulfur. Lime sulfur, Bordeaux mixture and sulfur fumigation are routine sterilization and disinfection means in facility agriculture. The sulfides produced by sublimation or fumigation undergo acid-base reactions with hindered-amine light stabilizers, forming inactive salts - the light stabilizer is "silenced," but the film keeps being degraded by UV and heat. This is the root cause of "clearly dosed, yet the greenhouse still bursts."

2. High chlorine. Chlorine-containing pesticides, soil disinfectants, and chloride water vapor that infiltrates the film in coastal areas also protonate HALS. Chlorine's lethality lies in its lower threshold - conventional HALS basically lose activity at a few hundred ppm sulfur or ten-odd ppm chlorine.

3. High temperature. Summer in-shed temperature can reach 60-80°C, and hot spots form where the film contacts the galvanized frame. High temperature not only accelerates the oxidative chain reaction itself, but also accelerates additive volatilization and migration, and makes the already-protonated inactive products escape the system faster - high temperature and sulfur/chlorine act synergistically, not independently.

Measured data: the 18-month turning point of film removal. At the end of 2019, the China Society of Agricultural Plastics Application Technology organized a batch field-application trial of "Xichang grape dedicated film." During the Xichang grape growth period, pesticide spraying exceeds 20 times per season, with very large lime-sulfur usage. Results:

• Of the 7 HALS samples tested, only the T-69 + HS-625 group still met the standard after 18 months of film removal;
• Another 5 (three groups 119, T-68, XT100) had mechanical retention already below 50%, reaching the aging end point;
• Adding hydrotalcite to HALS T-68 showed marked improvement;
• Changing the antioxidant had little effect; changing the anti-fog agent had a marked effect - indicating the main cause of aging is the light-stabilizer system, not the antioxidant system.

Conclusion of Secretary-General Qin Lijie: "Agricultural-film producers should stop blindly trusting foreign products; domestically developed pesticide-resistant light stabilizers have reached internationally leading levels."

IV. Match by Category: Four Topics

The following four pages break down each of the six categories, each giving an independent failure mechanism, formulation direction, product combination and acceptance method. Enter directly by your main category.

Topic 1 · Greenhouse Film - high-sulfur/high-chlorine pesticides, high-temperature hot spots, back-panel (inner-face) aging, and xenon + sulfur-fumigation acceptance.

Topic 2 · Mulch Film - the mechanical paradox of films as thin as 8-15 µm: survive a season + be recoverable + recycled material without downgrade.

Topic 3 · Nonwoven - additive extraction from ultrafine fibers, the dilemma of white fabric with no carbon black available, and dedicated masterbatches.

Topic 4 · Woven Fabric, Substrate & Shade Net - orientation stress, ground-surface environment, mesh wind load, and the unique color-fastness demand of shade nets.

V. Tiangang's Four Hard Assets on This Track

Two other endorsements often underestimated by customers: Tiangang's "Tiangang Anti-Aging Application Technology Center" is the first provincial-and-above enterprise technology center in the field of material aging and anti-aging (completed in 2007); and it participated in drafting multiple national standards for material aging and anti-aging. On the product side, T-66 / T-68 / T-69 are rare "named by industry scenario" additive packages on the market - belonging to the same "industry-specific additive package" product line as the automotive-modification-specific T-70/T-78, a unique approach of Tiangang in the additive industry.

VI. Frequently Asked Questions from Agricultural-Film Enterprises

Why does the film still burst after adding a light stabilizer?

Probably not insufficient dosage, but that the light stabilizer has been protonated and deactivated by sulfur or chlorine. Conventional N-H type HALS have relatively high basicity and form inactive salts with acids. Dosage only delays; the root problem is solved only by switching to low-basicity polymeric HALS, Me-HALS or N-OR (NOR) structures.

Does color matching affect weather resistance?

In agricultural covering materials, color basically does not affect aging performance. Greenhouse and mulch films care about mechanical retention and light-transmission retention, not color difference. Only categories with appearance selling points such as shade nets and nonwoven need extra attention to color fastness. (This is also why the choice of antioxidant in the formula need not be extra-dosed for "color protection.")

Should agricultural film do QUV?

It can, but the purpose differs. QUV is for early-R&D quick horizontal screening (short cycle, credible relative ranking); judgment and life extrapolation must use xenon (GB/T 16422.2), because the agricultural-film pesticide-resistance judgment standard T/CPPIA 12-2021 specifies the xenon-arc method. The two results are not interchangeable, nor can QUV hours be directly converted into outdoor years.

Can mulch film and greenhouse film share one formula?

No. Under mulch's one-season dosage of 8-15 µm, the selection logic of the stabilization system is almost opposite to that of greenhouse film: greenhouse film wants "the more stable the better, the longer it stays the better," while mulch film wants "hold a season, then be recoverable whole." See the mulch-film topic for details.

How much weight does high temperature carry in greenhouse-film aging?

Many underestimate it. In summer the in-shed 60-80°C, higher at frame contact points, not only accelerates oxidation but also accelerates additive volatilization and migration, and produces synergistic acceleration with sulfur/chlorine. This is why the same formula performs much worse in southern high-temperature high-humidity regions than in the north.

VII. Tiangang Product Comparison Table for the Six Categories