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How to optimize and improve the interfacial bonding strength between the fiber and the matrix of PPR tube with fiber?

Publish Time: 2025-10-10
As a new type of composite pipe, the core performance of PPR tube with fiber depends on the interfacial bonding strength between the fiber and the matrix. This interfacial bonding strength directly affects the pipe's pressure resistance, impact resistance, and durability. Optimizing this metric requires coordinated breakthroughs in material modification, process innovation, and structural design.

Fiber surface treatment is crucial for improving interfacial bonding strength. Untreated fibers have smooth surfaces, resulting in weak mechanical integration with the PPR matrix. Plasma treatment or chemical etching techniques can create micro- and nano-scale roughening on the fiber surface, increasing the contact area between the fiber and the matrix. For example, nitric acid oxidation treatment of glass fiber generates active groups such as carboxyl groups on its surface, which chemically bond with the PPR molecular chains. This surface activation treatment significantly improves the shear strength of the fiber-matrix interface and reduces debonding caused by stress concentration.

Matrix material modification plays a crucial role in interfacial bonding. Traditional PPR resins have limited compatibility with fibers. Introducing polar groups through copolymerization or grafting techniques can enhance the matrix's ability to wet the fibers. For example, introducing maleic anhydride grafted units into the PPR molecular chain creates anchor points that react with active groups on the fiber surface. This chemical modification not only improves interfacial adhesion but also inhibits interfacial crack propagation caused by differences in thermal expansion coefficients. Furthermore, the addition of nanoparticles as a third phase forms a transition layer at the fiber-matrix interface, alleviating thermal stress concentration.

A gradient structure design for the interfacial layer is an important means of achieving a balance between bond strength and toughness. An ideal interfacial layer should possess both high strength and energy dissipation capabilities. By controlling the thickness and composition of the fiber surface coating, a modulus gradient can be created from the fiber to the matrix. For example, a double-layer coating process, with an inner layer of a rigid coupling agent and an outer layer of an elastic polymer, ensures efficient load transfer while absorbing impact energy through elastic deformation. This structural design prolongs the interfacial crack propagation path when the pipe is subjected to external pressure, significantly improving fracture toughness.

Precise control of molding process parameters is crucial to interfacial quality. During extrusion, melt temperature, shear rate, and cooling rate directly influence fiber dispersion and interfacial crystallization behavior. Excessively high processing temperatures can cause the fiber surface treatment agent to decompose, reducing interfacial activity; while excessively rapid cooling rates can induce residual stress in the matrix. Using segmented temperature-controlled extrusion technology combined with a vacuum setting process ensures uniform fiber dispersion and perfect interfacial crystallization. Furthermore, optimizing the fiber length-to-diameter ratio to achieve a three-dimensional, random distribution of fibers within the matrix further enhances the pipe's isotropic performance.

Optimizing environmental adaptability is key to ensuring long-term, stable pipe operation. PPR tubes with fiber are often used in exposed installations and must withstand environmental factors such as UV rays and temperature fluctuations. Adding light stabilizers and antioxidants to the matrix can inhibit degradation of the interfacial region due to photoaging. Furthermore, co-extrusion technology is used to produce multilayer pipes, with a weather-resistant PPR outer layer and a fiber-reinforced inner layer. This not only protects the interface from environmental corrosion but also maintains the overall strength of the pipe.

Improving quality inspection and evaluation systems is crucial for ensuring interfacial performance. Traditional tensile testing cannot fully reflect the quality of interfacial bonding. Micro-CT imaging is needed to observe the interface microstructure and dynamic thermomechanical analysis is used to assess the interfacial viscoelasticity. Establishing a pipeline performance prediction model based on interfacial bonding strength can provide a scientific basis for product design.

Optimizing the interfacial bonding strength of PPR tubes with fiber requires a comprehensive approach encompassing material design, process control, and performance evaluation. Through the combined application of surface activation, matrix modification, gradient interface design, and precision molding processes, the mechanical properties and environmental adaptability of pipelines can be significantly improved. With the continuous advancement of composite material technology, PPR tubes with fiber will have even broader application prospects in fields such as water supply and drainage, heating, and more.
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