The selection of TPE coating materials should pay attention to these six aspects
Source：德創化工Time：2019-07-25Hits：3090
Many people do not know about TPE encapsulation. In the plastic aspect, encapsulation is the encapsulation of soft materials onto other materials. Generally, the processing methods used include one-step molding with a two-color injection molding machine or two-step injection molding with a common injection molding machine using an encapsulation mold. Today Dechuang TPE will introduce the matters needing attention in TPE encapsulation.
I. Selection of TPE Coating Materials
Different substrates should choose different TPE coating materials. For example, PP-wrapped TPE material cannot wrap ABS, ABS-wrapped TPE material cannot wrap PA, etc. At present, the coated TPE in the market can be divided into the following categories: PP coated, ABS coated, PETG coated, PC coated, PA coated, etc.
II. Thickness Selection of TPE Coating
In most rubber-coated molding applications, a wall thickness in the range of 1.5-3.0mm will ensure a good bonding effect. If the TPE adhesive position is too thin, injection molding is difficult, bonding strength is low, and hand feeling is poor. If the TPE glue is too thick, on the one hand, the cost is higher, on the other hand, it is easy to produce shrinkage, bubbles and other defects. The wall thickness of TPE glue should be as uniform as possible to achieve the best forming period. The transition between different wall thicknesses should be gradual to reduce problems caused by fluid flow, such as air streaks and bubbles.
Three, TPE encapsulation exhaust
Radius (minimum radius is 0.5mm) shall be adopted at sharp corners to reduce local stress. Deep closed air chambers or arched parts that cannot be exhausted should be avoided, and sufficient exhaust grooves (0.015-0.025mm) can be added at the end of TPE glue position if necessary. Inadequate exhaust may cause bad phenomena such as trapped air, burning glue and insufficient adhesion and relay.
4. Surface Treatment of TPE Encapsulated Mold
The mold should be polished to obtain a smooth or clear surface. In order to produce the matte appearance of thermosetting rubber surface, a rougher mold surface is required. Generally speaking, the rough surface of the mold cavity after electrical discharge machining (EDM) will produce a good appearance of the workpiece and make demolding easier. Grinding methods such as steam jet, sandblasting or shot peening and chemical etching can also be used to produce surfaces with different gloss and appearance.
V TPE Application Industry (Environmental Protection Requirements)
Different application industries have different testing standards. For example, the kitchen ware industry and the daily hardware industry have different environmental requirements for TPE. Most kitchen utensils industry has food-level testing requirements for TPE, while tool hardware industry usually only needs ROHS and REACH(SVHC) environmental protection requirements.
Six, TPE coating material other matters needing attention
It is very helpful to improve the bonding effect of TPE by adding buckle or making some deep concave-convex parts with proper design on the substrate. The base material should avoid using release agent. The surface of the base material should be clean to avoid dust. The processing temperature of TPE compound shall be based on the measured melting temperature of compound, not the display temperature of injection molding machine. If TPE is required to be coated on metal parts, appropriate adhesive can be used as an aid.
