What are the reasons why PC sheets may crack or even crack during use?
Many friends may experience the phenomenon of PC sheets bursting or cracking after installing it for a period of time after purchasing it? They will suspect that the product quality is not good, so they will start requesting the manufacturer to return it, and they will be very angry. But it's not just about product quality, there may be other reasons for the rupture.
What exactly caused it?
1、 Failure to apply force during installation due to rupture.
Before fixing the plate with screws, a pilot hole must be drilled with a diameter 6-9mm larger than the diameter of the fixing screw to prevent thermal expansion and contraction and prevent the plate from bursting due to excessive pressure. PC sheet has strong internal stress, which is formed during the process of extrusion molding and cooling shaping, while their appearance remains basically unchanged. During placement or use, they will undergo
A stress relaxation effect partially eliminated some internal stresses. However, PC sheets that have only undergone limited relaxation are difficult to completely eliminate these stresses, as they still retain significant internal stresses and then add external stresses generated during use.
If the stress is too high, a local deformation zone will occur in the surface layer and approach the surface, resulting in a vulnerable point. So during the installation process, it can also cause cracking.
2、 Neglecting the transportation and reservoir processes is also a cause of cracking.
Proper cushioning, packaging, and flat placement are necessary during transportation and storage, as any slight damage to the surface of the PC sheets will develop into cracks. And the PC sheets should not be stored in the same place as other chemicals, as volatile substances can cause chemical stress cracking on the surface of the PC sheetss. The PC sheets to be installed on the construction site must also be done in this way. Keep away from acidic substances such as cement, and do not use acidic adhesives during installation.
3、 Improper selection of processing tools can also lead to cracking.
Regardless of the type of processing, the cutting tools or instruments used must not cause any damage to the non processed parts of the PC sheet, and the cut must be smooth. Because even minor damage can lead to severe cracking. So for outdoor sheds produced by PC sheets companies, if edge cutting is required, a marble cutting machine must be used or a hand grinder must be used, and the cut must be smooth.
4、 During the installation process, attention should also be paid to some details.
1. Do not damage or remove the protective film before installation to avoid scratching the surface.
2. It is absolutely not allowed to directly nail the PC sheet onto the skeleton, otherwise it will generate high stress due to the expansion of the PC sheet and damage the perforated edge.
3. It is necessary to use sealant and gasket suitable for polycarbonate plastic. Wet sealant should be used in wet assembly systems. It is generally recommended to use polysiloxane adhesive for wet assembly of PCsheets, but special attention should be paid to checking the chemical adaptability of the adhesive before use. Amino, phenylamino, or methoxy curing agents should never be used to cure polysiloxane adhesive, as these curing agents can cause cracking of the sheet, especially when there is internal stress. Never use PVC as a sealing gasket, as plasticizers in PVC can precipitate and corrode the board, causing surface cracking and even damaging the entire sheet.
5、 PC sheets are prone to cracking when in contact with acids and alkalis.
PC hollow sheets should not come into contact with alkaline substances and corrosive organic substances such as alkali, basic salts, amines, ketones, aldehydes, esters, methanol, isopropanol, asphalt, etc. These substances can cause severe chemical stress cracking.
6、 The installation bending degree shall not be less than the specified radius.
If the curvature radius of the bent PC sheet is too small, the mechanical strength and chemical resistance of the PC sheet will sharply decrease. In order to avoid dangerous stress cracking on the exposed side, the bending radius of the PC sheet must not be less than the specified data. Multi layer PC sheets must not be bent perpendicular to the direction of the ribs, as it can easily flatten or even break the sheet. The sheet must be bent in the direction of the ribs.
As long as we know the cause of cracking, we can prevent it in a timely manner and take remedial measures in a timely manner.