Polymerization Shrinkage
Polymerization Shrinkage - Related Videos
01:27
Shrinkage in Concrete
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2024
Shrinkage in concrete is primarily due to water loss from evaporation, hydration of cement, or carbonation, leading to a reduction in volume. The volumetric contraction results in volumetric strain in concrete. However, in practice, shrinkage is measured as linear strain, which is one-third of the volumetric strain. When concrete is still in its plastic state, it can undergo a decrease in volume by about 1% of its absolute volume. This decrease is known as plastic shrinkage. It arises either...
01:21
Drying Shrinkage
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2024
When hardened concrete is exposed to air with a relative humidity of less than 100 percent, it begins to lose the free water within its capillaries. As this water evaporates, the water initially adsorbed onto the calcium silicate hydrates migrates towards these now empty spaces and eventually evaporates as well. Over time, as more water leaves, the volume of the concrete decreases, a phenomenon known as drying shrinkage. A portion of this drying shrinkage can be reversed; if the concrete is...
01:24
Carbonation Shrinkage
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2024
Atmospheric CO2 penetrates the concrete's pores and, in the presence of moisture, forms carbonic acid, which then reacts with calcium hydroxide in the hydrated cement, forming calcium carbonate. This process reduces the concrete's volume and is termed carbonation shrinkage. The concrete's permeability is slightly reduced as calcium carbonate produced during the reaction fills its pores. Furthermore, its strength is slightly enhanced as the water released during the reaction facilitates the...
08:45
Shrinkage of Dental Composite in Simulated Cavity Measured with Digital Image Correlation
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Cited by 12 •
2014
In order to understand the spatial development of polymerization shrinkage stress in dental resin-composite restorations, Digital Image Correlation was used to provide full-field displacement/strain measurement of restored model glass cavities by correlating images of the restoration taken before and after polymerization.
06:45
Polymerization
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2023
Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA Polymers are made from macromolecules, which are composed of repeating units (the so called monomeric units). In our modern world, polymers play an important role. One of the first important polymers was nylon, which is a polyamide. It found widespread application in tooth brushes and stockings.
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During curing, covalent bonds form between monomer units and draw those units closer together. This reduces the intermolecular spacing present in the liquid, producing a smaller solid volume. If the developing polymer cannot contract freely, the same molecular rearrangement can generate internal stress, making molecular bonding and geometric constraint central to the outcome.
Constraint changes shrinkage from a dimensional change into a mechanical problem. A polymer that is bonded to surrounding surfaces cannot contract without transmitting forces to those interfaces or nearby material. In resin-based composite restorations, this interaction can compromise the interface and is associated with marginal gaps, interfacial leakage, and postoperative sensitivity.
Material design addresses shrinkage through the monomer system and filler composition, while processing design addresses it through curing protocols and placement techniques. These variables are not merely manufacturing details: together, they influence how a restoration develops and manages shrinkage-related stress. Their optimization is intended to improve restoration integrity and clinical durability.
Polymerization shrinkage and shrinkage stress describe related but different outcomes. Shrinkage is the reduction in volume as liquid monomers become solid, whereas stress is the internal mechanical consequence that may arise when contraction is constrained. Distinguishing them helps explain why the same curing process can create an interfacial problem when surrounding surfaces restrict movement.
To address the issue in a dental restoration, planning should consider the resin-based composite’s monomer system and filler composition, then align curing protocols with an appropriate placement technique. The goal is not simply to produce a cured material, but to support interfacial integrity by reducing the consequences of contraction during restoration formation.
Clinical concern centers on what happens at the bonded interface after curing. Shrinkage-related stress may promote marginal gaps, which can permit interfacial leakage, and the restoration may be associated with postoperative sensitivity. These outcomes make polymerization shrinkage relevant to both immediate patient experience and the longer-term integrity and durability of resin-based composite restorations.
Outside dentistry, the same consideration applies to medical materials and device fabrication whenever a liquid monomer system is converted into a solid polymer. Designers must account for volume reduction and possible stress if the developing material is attached to or constrained by surrounding surfaces. This perspective connects material processing choices with the integrity of finished medical devices.