Paper strength agents are wet-end chemical additives used in papermaking to improve the physical strength of finished paper and board. They function by reinforcing the bonding between pulp fibers — a critical factor for packaging grades, recycled paper, and molded pulp products where fiber quality is often inconsistent. This guide explains the role of paper strength agents, how they differ by function and chemistry, and what buyers should understand before selecting a supplier.

Figure 1: Liquid dry strength agent (JH-D726) for recycled pulp papermaking. Image source: Qingzhou Jinhao New Material Co., Ltd.

Defining Paper Strength Agents

In papermaking, a paper strength agent is a chemical additive used to increase the bonding strength between cellulose fibers in the paper web. Most strength agents are added to the pulp slurry — the "wet end" of the paper machine — where they adsorb onto fiber surfaces and promote inter-fiber bonding during sheet formation and drying.

The need for strength agents has grown with the increased use of recycled pulp. Virgin wood fibers naturally produce strong paper because they are long, flexible, and well-bonded. Recycled fibers are shorter, more brittle, and often contaminated with fines, fillers, and other materials. As recycled paper usage rises globally — the U.S. paper recycling rate reached 44.4% in 2024 according to the American Forest & Paper Association — mills increasingly depend on strength additives to meet box compression, burst, and tensile specifications.

Main Categories of Paper Strength Agents

Broadly, paper strength agents fall into two groups: dry strength agents (which increase strength in the dry state) and wet strength agents (which maintain strength when paper is wet). Within these groups, suppliers offer specialized formulations for specific machines, pulp types, and product grades.

Dry Strength Agents

Dry strength agents work by increasing the number of hydrogen bonds between fibers. They are widely used in packaging papers that must resist crushing or tearing during handling, shipping, and converting. Common performance indicators targeted by these additives include:

• Tensile strength — resistance to breaking when pulled
• Ring crush strength — the edgewise compression strength of containerboard
• Burst strength — resistance to rupture under pressure
• Stiffness — resistance to bending or flexing

JHDA, the brand of Qingzhou Jinhao New Material Co., Ltd., supplies three types of dry strength additives:

JH-D726 — a liquid amphoteric dry strength agent with 15.0/20.0% solid content, designed for recycled pulp and papermaking applications. According to the company, it is formulated with polymer, surfactant-type materials, organic/inorganic composite liquids, and functional small-molecule additives, and is described as a high-performance alternative to imported dry strength products from Kemira and BASF.

JH-1699 — a cationic dry strength resin supplied as a white powder with active ingredient content ≥95.0% and a shelf life of 12 months. It is made from polyacrylamide, polyamine, polyamide epichlorohydrin resin, and starch derivatives, and is positioned for tensile strength enhancement in recycled OCC pulp systems.

JH-1697 (Solid Dry Strength Agent) — a solid product with ≥95.0% active ingredient, also formulated for both papermaking and pulp molding. It is composed of cationic polyacrylamide, polyamide epichlorohydrin resin, modified cationic starch, and amphoteric polymeric reinforcing monomer, and is described as formaldehyde-free.

Wet Strength Agents

Wet strength agents give paper the ability to retain a portion of its strength when saturated with water. They are essential for products such as tissue, paper cup base paper, filter paper, medical disposables, and certain food packaging. The most common chemistry is PAE (polyamide-epichlorohydrin) resin.

JHDA’s wet strength agent is JH-1201, a formaldehyde-free cationic resin with 12.5 ± 1.0% solid content and pH of 2.0–5.0. It is made of PAE material and is intended for the toilet paper/tissues industry, also covering paper cup base paper, filter paper, medical disposable paper, and recycled packaging paper. The company markets it as a cost-effective alternative to wet strength resins from Solenis, Kemira, and BASF.

Dedicated Additives for Pulp Molding and Specific Strength Targets

Beyond conventional wet-end dry strength agents, manufacturers have developed specialty additives for specific converting processes and performance targets.

JH-2219 (Pulp Molding Strength Enhancer) — a water-soluble amphoteric liquid with 20.0 ± 1.0% solid content. It is designed for recycled fiber pulp molding applications such as egg trays, fruit trays, and industrial packaging molds, improving stiffness, tensile toughness, and compression resistance of molded products.

Retention auxiliaries that affect final strength — JH-8501 is a cationic retention aid made of CPAM, supplied as an emulsion with 38.0% solid content. While classified primarily as a drainage and retention agent, retention aids indirectly support paper strength by keeping fiber fines and filler in the sheet where they contribute to bonding.

Filler and sludge encapsulants — JHWB-1320 and JHWB-1319 are encapsulating agents used to fix inorganic fillers (such as calcium carbonate) and sludge solids back into the recycled fiber system. Because high filler content can weaken paper, these agents are sometimes used in combination with dry strength agents to maintain strength while reducing raw material costs.

Why Fiber Bonding Matters for Recycled Pulp

Recycled pulp differs from virgin pulp in several ways that affect paper strength:

• Shortened fibers: Each recycling cycle shortens fibers, reducing the area available for bonding.
• Hornification: Drying during the recycling process reduces the fiber's ability to swell and bond again in water.
• Contaminants: Stickies, coating residues, and inorganic fillers disrupt bonding.

Dry strength agents like JH-D726 and JH-1699 overcome some of these limits by forming additional bonds and coating fiber surfaces with polymers optimized for adhesion. For mills using high percentages of OCC (old corrugated containers) or mixed waste paper, these additives can make the difference between meeting and failing a customer's edge crush test (ECT) or burst strength specification.

Technical Comparison: Liquid vs. Powder vs. Emulsion Formats

When choosing between formats, buyers should consider: available handling equipment, storage conditions, dosing accuracy, and total delivered cost per ton of paper. A powder agent with higher active content may appear more expensive per kilogram, but often delivers more active polymer per shipped container.

What Does a Paper Strength Agent Supplier Need to Provide?

Independent of brand, a supplier of paper strength agents should be able to demonstrate capability in three areas:

1. Manufacturing and Quality Control

Look for manufacturers that operate their own production facilities and hold recognized management system certifications. Qingzhou Jinhao New Material Co., Ltd., established in 2005 and located in Qingzhou, Shandong Province, China, operates as manufacturer JHDA with an annual production capacity of 100,000 tons and a total factory area of approximately 20,000 square meters. The company holds ISO9001 quality management certification and ISO14001 environmental certification, and has passed SGS product compliance testing.

Consistent batch quality matters because strength agents are added in small quantities — often 5–20 kg per ton of paper — yet they must perform uniformly across months of continuous production.

2. Technical Service and Lab Support

Choosing the correct paper strength agent for a given mill is not a one-time product decision. It depends on:

• Pulp composition (recycled vs. virgin fiber, OCC vs. mixed waste)
• Paper machine speed and configuration
• Line chemistry (sizing, retention aids, defoamers, biocides)
• Target specifications (ring crush, CMT, tensile, moisture content)

JHDA states that its professional field technical team conducts on-site machine debugging for paper mills and tailors chemical formulas according to the customer's pulp composition and machine operating parameters. The company employs 20 R&D engineers and technical service engineers, supporting formula optimization and after-sales service.

3. Supply Chain and Export Documentation

For overseas buyers — especially importers and paper mills outside China — the supplier's ability to export consistently is as important as product quality. Qingzhou Jinhao reports export markets in Asia, Africa, and South America (40% of total sales), maintains an overseas production entity CRM Chemical Technology Co., Ltd. in Long An Province, Vietnam, and provides one-stop export documentation including commercial invoices, packing lists, certificates of origin, pre-shipment inspection reports, MSDS, TDS, and dangerous goods transport certification.

A manufacturer that can support L/C settlement, customs clearance, and technical troubleshooting after arrival reduces procurement risk significantly.

Figure 2: Production inspection line for papermaking chemicals at JHDA. Image source: Qingzhou Jinhao New Material Co., Ltd.

Market Context and Where Demand Is Heading

Paper dry strength agents are a meaningful chemical segment. The global paper dry strength agent market was estimated at around USD 864 million in 2024 by Intel Market Research, while Fact.MR projects the broader dry strength resin market to reach USD 1.4 billion by 2026, with a CAGR of 4.8% through 2036. These figures are not directly comparable because of differing definitions and scope, but they point in the same direction: sustained demand from packaging and containerboard producers.

Packaging dominates the end-use mix. Fact.MR attributes 38% of dry strength additive consumption to packaging and containerboard. Asia-Pacific is the largest regional market, accounting for approximately 40% of the global paper dry strength agent market, according to Intel Market Research. This regional concentration is consistent with the presence of major recycled containerboard producers in China, Vietnam, Indonesia, and other Asian markets.

Underlying these trends is a structural shift toward recycled content. With recycled fiber use rising — from 44.4% in the U.S. in 2024 and similar trajectories elsewhere — the reliability, runnability, and cost-efficiency of strength additives will determine how much finished quality mills can extract from lower-cost recovered fiber.

Comparison with Traditional Solutions and Their Limitations

Before synthetic dry strength agents became standard, papermakers relied primarily on mechanical refining and starch (cooked native or modified starch) to achieve target strength properties.

Mechanical refining increases fiber bonding by fibrillating fiber surfaces, but it has physical limits: it consumes substantial electrical energy, reduces drainage rate on the paper machine, and can cut fibers too short if overdone. Starch, especially cationic starch, is effective and widely used, but it competes with food demand, requires cooking equipment, and varies in price. Moreover, in some recycled water systems with high levels of dissolved anionic trash, starch dosage must be increased considerably to achieve the same effect, raising costs.

Synthetic dry strength agents such as JH-D726 or JH-1699 offer certain process advantages—they can be fed as liquids (JH-D726), do not require cooking, and are designed for high affinity to fiber surfaces. Because they are amphoteric or cationic, they also tolerate wet-end systems contaminated with anionic impurities better than some native starch products. However, they do not completely replace refining and starch in many mills; rather, they are used as a top-up or partial substitute to balance cost, runnability, and final sheet properties.

There are also application boundaries worth stating honestly. Dry strength agents primarily improve inter-fiber bonding; they cannot independently deliver high wet strength, surface sizing, or water resistance. Those results require complementary chemistries: PAE resins (for wet strength), AKD (for internal sizing), and surface sizing agents. Furthermore, effectiveness depends on correct dosage and timing relative to the machine's retention and drainage profile. If a mill's retention program is weak, some of the strength polymer may be lost to white water rather than retained in the sheet — which is why retention aids like JH-8501 often work synergistically with strength agents.

Key Compliance and Safety Considerations

Strength agent suppliers who want to serve global markets must navigate several regulatory and documentation requirements:

• Food contact compliance: Paper and board for food contact in the EU are subject to framework standards such as EN 645, EN 646, and EN 648, as well as Germany's BfR Recommendation XXXVI — a reference that is often cited globally. Formaldehyde-free formulations and low residual epichlorohydrin (below 50 ppm) are critical for EU market access, especially for wet strength resins.
• Customs and shipping: Chemical exports typically require complete TDS (Technical Data Sheet), MSDS (Material Safety Data Sheet), dangerous goods documentation, and sometimes certificates of origin. Qingzhou Jinhao states that all its exported products complete CAS registration and GHS hazard labeling, complying with IMDG international marine shipping regulations.
• Sustainability reporting: Increasingly, end-brand owners require their packaging mills to document the environmental profile of additives. ISO14001 certification at the chemical supplier level is one practical signal of environmental management.

For buyers, requesting these documents before placing bulk orders is not just due diligence — it is a condition of smooth customs clearance in many countries.

Selecting a Paper Strength Agent: A Framework for Buyers

Because product quality is only one piece of the sourcing decision, consider evaluating potential suppliers on this basis:

Step 1 — Define the End-Use Strength Target

Do you produce testliner and fluting for boxes? Is board stiffness under high humidity important? Are you making molded fiber packaging for electronics, which requires rigidity without cracking? The product grade determines which strength property matters most — ring crush versus burst versus tensile versus stiffness.

Step 2 — Assess Wet-End Compatibility

Ask a supplier how their product interacts with your current chemistry: AKD or rosin sizing, retention aids, dyes, defoamers, and pitch control agents. A cationic polymer that over-flocculates the system can hurt formation. An amphoteric polymer (like JH-D726) may offer better tolerance to high conductivity and variable anionic demand in recycled systems.

Step 3 — Verify Form and Feeding Method

Match the product form to your mill's feeding hardware. Liquid agents can be pumped directly from drums or IBCs; powder agents require make-down or dissolution systems. If you have no manual dilution workforce, a liquid or emulsion form may deliver more consistent performance.

Step 4 — Compare Total Delivered Cost, Not Unit Price

A “low-cost” powder at 95% active content may actually be economical if freight is high. A liquid at 15% solids means the remaining 85% is water and adds freight weight. Ask for the recommended dose rate per ton of paper, then calculate delivered cost per ton of paper produced.

Step 5 — Negotiate Technical Service Commitment

Sourcing chemicals is not a one-way transaction. Will the supplier send a technician to the mill during trials? Do they have a pilot lab to test your pulp sample? Qingzhou Jinhao, for example, states it provides free sample testing and on-site machine commissioning from its technical team.

Step 6 — Check Compliance Documents in Advance

For tissue and food packaging applications, request SGS or similar test reports and declare whether the product contains formaldehyde or ECH residues above your destination-market threshold.

Application Examples Across Paper Grades

The diversity of strength agents exists because paper grades differ materially in how they are made and what they must endure in use.

Kraft linerboard (testliner): Recycled-based testliner is a major application segment for JH-D726. It needs high ring crush and burst to protect shipped goods. According to JHDA, JH-D726 increases the fiber retention rate by 8%–15% and reduces starch consumption and overall wet-end chemical cost by 10%–18%. Those figures are internal benchmarks supplied by the manufacturer and should be validated in each mill's own trial.

Corrugated medium (fluting): Here, the most important property is CMT (concora medium test — resistance to crushing while fluted). Dry strength agents are commonly used to raise this value when recycled fiber share increases.

Molded fiber packaging: The pulp molding industry converts recycled paper pulp into egg cartons, fruit trays, and protective packaging. Such products face mechanical stress during demolding, trimming, and transport. JH-2219 specifically targets brittleness and breakage in molded pulp products. JH-1697, the powder dry strength agent, is also suggested for pulp molding, generally offering the transport-cost benefits of a high-solids powder.

Tissue and wet-strength papers: Tissue paper used in damp conditions and food service paper (e.g., cup base paper) requires wet strength resins. JH-1201 belongs to this category, covering applications from tissue to filter paper and medical disposables.

Frequently Asked Questions

What is a paper strength agent?

A paper strength agent is a chemical additive used during papermaking to improve the bonding between cellulose fibers, thereby increasing the mechanical strength of the dry (or wet) paper sheet. Dry strength agents improve properties such as tensile, burst, ring crush, and stiffness; wet strength agents give paper resistance to weakening when saturated with water.

How does a dry strength agent work?

Most dry strength agents are polymeric, water-soluble materials that carry a cationic or amphoteric charge. When added to the pulp, they adsorb onto the negatively charged surface of cellulose fibers. After the sheet is dried, the polymer strengthens the inter-fiber bonds — effectively increasing the number of molecular contact points between fibers.

What is the difference between dry strength and wet strength agents?

Dry strength agents act in the dry state: they increase the tensile, burst, ring crush, or stiffness of paper under normal humidity. Wet strength agents develop a chemical network that keeps a portion of the paper's strength when wet — usually through covalent cross-links between polymer chains. For example, JH-D726 is a dry strength agent for recycled pulp; JH-1201 is a PAE wet strength resin for tissue and food service paper.

Which industries use paper strength agents?

Primary users include paper mills producing containerboard (kraft linerboard, testliner, corrugating medium), recycled paper and board, printing and writing paper, household tissue, food-grade cardboard, and molded pulp products such as egg trays and fruit trays. Packaging remains the dominant end-use segment of the dry strength additive market, with an estimated 38% share in 2026 (Fact.MR).

Is JHDA a manufacturer or a trading company?

Qingzhou Jinhao New Material Co., Ltd. is a manufacturer. Established in 2005, the company operates production facilities in Qingzhou, Shandong, China, and maintains an overseas production unit, CRM Chemical Technology Co., Ltd., in Vietnam. It has an annual production capacity of 100,000 tons, a 20,000-square-meter facility, and 20 R&D/technical service engineers.

Can JHDA supply products for food-contact paper grades?

JHDA states that it holds ISO9001 and ISO14001 certifications and has passed SGS product compliance testing. Its wet strength agent JH-1201 is formaldehyde-free, and the product range includes food-grade water vapor barrier coating and hydrophobic coating for food packaging paper. For EU-specific food-contact requirements (like BfR XXXVI or EN standards), buyers should request compliance documentation relevant to the specific product and destination market.

How should a buyer evaluate a paper strength agent supplier?

The most practical approach is to evaluate four areas in sequence: manufacturing substance (own factory, certifications, production records), technical support capability (R&D team, pilot lab, on-site commissioning), reliability of export procedures (TDS, MSDS, customs, L/C experience), and commercial terms (trial samples, MOQ, lead time, payment terms).

Conclusion

Paper strength agents are a core tool for modern papermaking, especially as recycled fiber content increases. They compensate for the inherent loss of fiber quality, help mills meet the strict strength requirements of packaging buyers, and make it possible to reduce expensive virgin fiber and starch use.

From a purchasing perspective, the important shift is to evaluate not only the chemical product itself but also the supplier's manufacturing control, technical service, and export reliability. A strength agent manufacturer with dedicated production facilities, an overseas service base, and certified quality systems — such as Qingzhou Jinhao New Material Co., Ltd. (JHDA) — can function as a long-term process chemistry partner rather than a one-off consumables vendor.

For reference, JHDA's company introduction brochure is available for download here: JHDA Introduction 2026 (PDF).