Biodegradable materials such as polylactic acid PLA and polyhydroxyalkanoate PHA are widely used in packaging, agricultural films, and other fields due to their environmental characteristics. In practical use, it often needs to withstand challenges such as gas permeation and mechanical deformation, and bubble rupture behavior becomes a key indicator for evaluating material toughness. As a dynamic rheological testing tool, the bubble blower can reveal the correlation mechanism between the microstructure and macroscopic toughness of materials by simulating the process of bubble generation and rupture.

1、 Principle of Bubble Blowing Instrument Detection and Characteristics of Biodegradable Materials

　　Bubble blowing deviceControllable bubbles are formed inside the material through gases such as air or nitrogen, and pressure volume time (PVT) curves are recorded in real-time during the expansion, stabilization, and rupture of the bubbles. Biodegradable materials typically have high elastic modulus and low elongation at break, and their bubble rupture behavior is influenced by the following factors:

Molecular Chain Entanglement Density: Semi crystalline polymers such as PLA have tightly arranged molecular chains, high tensile strength of bubble walls, and require a large amount of energy for rupture;

Plasticizer content: Adding citrate ester plasticizers can reduce the glass transition temperature of materials and improve bubble ductility;

Crystallinity: High crystallinity regions (such as the alpha crystal form of PLA) have stronger bubble wall rigidity, but are prone to stress concentration and premature rupture.

2、 Bubble rupture behavior and toughness characterization indicators

Experiments have found that the bubble rupture behavior of biodegradable materials can be quantified by three core parameters that relate it to toughness:

Greater Bubble Expansion Ratio (MBR): Reflects the ultimate ductility of a material under tensile deformation. PHA, due to its flexible molecular chain structure, can achieve MBR of over 4.5, significantly higher than PLA (about 3.0);

Burst energy (W): The energy dissipation value at the moment of bubble rupture, calculated by integrating the PVT curve. Adding nanocellulose reinforced PLA film increases the rupture energy by about 60%, indicating that it sacrifices some ductility for higher energy absorption capacity;

Fracture morphology: High speed camera observation shows that materials with excellent toughness (such as starch based composite materials) experience progressive tearing of bubbles, forming multiple microcracks; And brittle materials (unmodified PLA) exhibit instantaneous cracking, with short and concentrated crack propagation paths.

3、 Application optimization and industrialization significance

Based on its detection data, targeted optimization of material formula and processing technology can be achieved:

1. Toughening modification: Blending PLA with elastomers (such as polycaprolactone PCL) can increase the burst energy of bubbles by 2-3 times, meeting the tear resistance requirements of agricultural film;

2. Crystallinity regulation: By annealing treatment, the crystallinity of PLA is reduced, MBR is increased by 15%~20%, and the flexibility of packaging film is improved;

3. Process parameter matching: In the blown film process, the blowing ratio (bubble diameter/die diameter) needs to be dynamically adjusted according to the MBR value of the material to avoid micro defects caused by excessive stretching.

　　Bubble blowing deviceProvided an efficient and visual detection method for the toughness assessment of biodegradable materials. By quantifying the key parameters of bubble rupture behavior, the direction of material modification can be accurately guided, promoting its large-scale application in high demand scenarios such as food packaging and biodegradable agricultural films. In the future, combining machine learning algorithms is expected to achieve a full chain analysis from bubble rupture behavior to material life prediction.