Recently, a Shanghai resident social media posts reported that exposed fiberglass was found on the railing surface of Zhangdong Road Zhangjiabing Bridge in Pudong New Area. She took her child for a walk and on the way home, the child said their "hand itched," and it was later discovered that fiberglass from the railing had gotten into their hand. Even after going to the hospital, it could not be completely cleaned and they had to wait for it to fall out naturally. The maintenance unit has submitted a major repair plan to the management agency, which has approved the project to replace the entire line. It is currently in the bidding phase and is expected to be implemented in the second half of this year. It is said that the plan is to change the railing material and no longer use fiberglass reinforced plastic (referred to as composite material below).

Another field faces the situation of being phased out! What do composite material colleagues think?

The author believes that the vast majority of industry experts and enterprises should understand why this problem occurs. It is simply that there is a problem with the selection of the resin matrix, UV-9, etc., whether UV absorbers and light stabilizers are added, and the surface Polyester felt is lacking, and there is no surface coating, etc. Let's do a technical and engineering project level analysis.

1. The problem of UV resistance

For outdoor composite material products, under the condition of durability requirements, UV resistance design is generally required. For example: stadium seats, bus seats, railings, highways Anti-glare panels outdoor storage tanks, pipelines, drinking water and fire water tanks, automotive body parts, fishing boats, yachts, cruise ships, wind turbine blades, photovoltaic composite material frames and brackets, etc.

Many products use various methods for weather resistance protection according to different application environments, such as surface coating, using resins with strong UV resistance, increasing rich resin layer adding UV-9, light stabilizers, etc., to improve the product's UV resistance and thus improve the product's service life.

Taking wind turbine blades and anti-glare panels as examples, both products use surface coating for UV protection. Wind turbine blades use UV-resistant and wear-resistant coatings, with a service life of 20 years, and some blades have a service life of 25 years without any problems. The SMC anti-glare panels used on the second and third ring roads in Beijing are surface-coated with fluorocarbon coating and have not been replaced since their installation in 2001, and their surface condition remains as good as new.

For some products that do not require surface coating, isophthalic unsaturated polyester resin with slightly better UV resistance is generally used, and UV absorbers and light stabilizers are added to ensure that the surface is not damaged during long-term use. For example, molded SMC seats, water tanks, etc.

2. Application issues of surface polyester felt

There are various composite material product processing technologies, such as molding, pultrusion, winding, vacuum infusion, hand lay-up, etc. The railing reported in the article is made by pultrusion. Resin-impregnated glass fiber is passed through a mold and pulled out by a traction device. Because it is pressed in the mold, it is commonly known as pultrusion. This type of process product has extremely high axial strength and is suitable for making equal-section profiles. The railing is assembled from equal-section pultruded profiles. Pultruded products are widely used in automobiles, photovoltaic frames, various brackets, marine ranches, doors and windows, railings, anti-corrosion grids, etc.

Pultruded products are characterized by high glass fiber content and low resin content, high axial tensile strength and modulus. Due to the low surface resin content, outdoor products should generally use isophthalic unsaturated polyester resin or weather-resistant polyurethane resin. UV absorbers should also be added to the isophthalic resin; at the same time, in order to increase the surface resin content, polyester surface felt should be wrapped around the outermost layer of glass fiber during pultrusion, which will greatly improve the weather resistance and UV resistance of the product.

3. Competition issues

From the photos in the article, it can be seen that the product has not been surface-coated. The author analyzes that the resin used is not a better UV-resistant resin, or even that no UV absorbers were added to the resin; no polyester surface felt or measures to increase the surface resin content were used.

(Source: Internet)

The composite material industry has developed rapidly since the 1990s due to its low investment and technical thresholds; at the beginning of this century, it began to experience disorderly and fierce competition. Because the raw materials of composite material products are difficult to detect after molding, many inferior and counterfeit products have flooded the market. Due to disorderly competition, cable protection pipes, sand-filled pipes, and drinking water tanks have been almost eliminated, leaving users with the bad impression that fiberglass products are low-end and unreliable.

The railing mentioned in the article is presumably also a result of the fierce competition leading to counterfeit and inferior products.

4. Low-price bidding for engineering projects

However, from a deeper perspective, low-price bidding for engineering projects is the root cause of fierce and disorderly competition. Historical experience has verified this countless times. In the current situation of overcapacity in various industries, obtaining orders is the fundamental pursuit of enterprises, and profit is the goal. No matter how low the price is, enterprises must make a profit. Therefore, when the price is lower than the design cost, the only thing enterprises can do is to cut corners.

The article mentions that "investigations by reporters have found that the maintenance of roads and bridges involves a wide range of aspects, and railings are not a key focus of maintenance work. Taking Zhangdong Road Zhangjiahama Bridge as an example, maintenance inspections are divided into three types: daily inspections, regular inspections, and periodic inspections, with frequencies of once a day, once a month, and once every three years (once a year for special bridges). Although the frequency is fixed, the focus of the inspection is on the safe passage of vehicles and pedestrians on the bridge. Railings are mainly checked for damage that affects safety, and the condition of the railing surface is difficult to detect through vehicle-based visual inspection. Hu Yi Highway also has daily patrols, but road surfaces, greening, and cleaning are all within the scope of daily patrols, and the attention paid to railings is limited. Relevant persons in charge of the maintenance company stated that in recent years, maintenance records show that railings account for a very small proportion of reported maintenance actions on this road, and their impact on road traffic safety is also relatively small." In fact, such products that have a relatively small impact on traffic safety are rarely given attention. The exposure of fiberglass on the surface of the product is not something that happens overnight, but rather a long process. If it had been discovered and addressed earlier and proactive measures had been taken, such problems should not have occurred. For metal guardrails, users know to repaint them periodically, but why isn't there such a plan for fiberglass products?  

For the railings mentioned in the article, there is no need to go to the trouble of replacing them; the most cost-effective method is to apply a UV-resistant coating to the surface. If fluorocarbon paint is used, it is estimated that there will be no problems even after 30 years of use. The purpose of the coating is to encapsulate the exposed fiberglass and achieve UV resistance, preventing further exposure.

Society and government departments cannot be deterred from taking action. The solution should be quick, efficient, economical, and effective, rather than a blanket rejection, which would not only cause huge economic losses but also lead to deeper-level impacts.  

Under the impact of unfavorable economic conditions and international trade tariffs, enterprises face a difficult path to development and survival. However, industry data from 2024 shows that the composite materials industry is in a period of low-level growth, indicating that the composite materials industry is still in its development phase. However, industry enterprises should continuously improve their self-discipline awareness and not engage in industrial activities like "monkeys picking up corn cobs"—they cannot destroy their own livelihoods.

For many years, enterprises have been plagued by low-price competition. Many small and micro enterprises have scattered business orders and dispersed product application areas, making it impossible to achieve scale and resulting in poor self-discipline. Industry associations are also actively trying to regulate industry development, but so far, there have been no good results.

Establish product instructions. If railing manufacturers clearly inform users during delivery that the product requires surface coating maintenance every 5 years, this kind of situation would not have occurred. Composite materials industry products have many industrial shell-type supporting products and profiles (materials), but fewer complete products, so everyone has not realized the need for instructions for materials or products, perhaps thinking it is simple and unnecessary. However, many problems often arise during the engineering process. For example, leakage caused by the construction and installation of fiberglass pipes; fires during the metal welding process of desulfurization and denitrification towers and chimneys, are all caused by the lack of attention to product instructions and construction and installation training.

Implementing a "quality control capability grading" evaluation may be a new way to solve the problem of stable industry development. Quality control capability grading evaluates enterprises from various aspects, including quality management, design and development capabilities, equipment capabilities, energy consumption levels, low-carbon emissions, delivery capabilities, personnel quality, and after-sales service, and then assigns grades. Then, promote it to users, gain user recognition, and let users feel at ease, secure, and comfortable.

In short, the "railing assassin" has appeared. Fiberglass composite material enterprises should actively face this issue, reflect on the problems existing in the industrial development process, and avoid the occurrence of various hidden problems in future development. In recent years, the China Building Materials Federation has organized enterprises in various fields to establish "building materials product instructions" and has formulated relevant standards, organized competitions, and encouraged enterprises to actively establish product instructions; at the same time, the Building Materials Federation has also carried out "quality grading and 'leader' evaluation requirements" and "building materials supplier quality control capability grading" activities. Composite material enterprises should also actively respond and participate in various activities to add luster to the high-quality and stable development of industry products and resolutely resist behaviors that discredit the industry.

In the user field, the usage requirements of composite materials products should be obtained, and construction and maintenance and repair plans should be formulated accordingly. At the same time, the strength of product manufacturers should be given more attention in the bidding process to avoid low-price bidding and ensure the reliability and high quality of product quality.

Reprinted from the Low-Carbon Composite Materials Public Account

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