ASSEMBLY OF POLYMERIC PARTS

Abstract

The invention relates to an assembly of parts comprising a first part containing a first polymer composition and a second part containing a second polymer composition, both compositions comprising a semi-crystalline polymer and optionally one or more other components, the first part and the second part being fastened to each other through an interface between the first polymer composition and the second polymer composition, wherein the interface is free from mechanically interlocking elements and the thermal conductivity of the second polymer composition (TC2) is higher than the thermal conductivity of the first polymer composition (TC1) with a factor TC2/TC1 of at least 1.5. The invention further relates to a process for manufacturing such an assembly and to various uses of said assembly.

Claims

1. A process for manufacturing an assembly of parts comprising a first part containing a first polymer composition comprising a semi-crystalline polymer, referred to as “first polymer”, and optionally one or more other components, and a second part containing a second polymer composition comprising a semi-crystalline polymer, referred to as “second polymer”, and optionally one or more other components, the first and second part being fastened to each other through an interface between the first polymer composition and the second polymer composition by multiple-component injection moulding, preferably by two-component injection moulding, wherein the first part containing the first polymer composition is injection moulded first and the second part containing the second polymer composition is injection moulded second over the first part to create an interface between the first polymer composition and the second polymer composition, and the thermal conductivity of the second polymer composition (TC2) is higher than the thermal conductivity of the first polymer composition (TC1) with a factor TC2/TC1 of at least 1.5.

2. The process according to claim 1, comprising the steps of: (i) injection moulding the first polymer composition, i.e. the polymer composition having the lower thermal conductivity (TC1), at an injection temperature above the melting temperature (Tm1) of the first polymer to form the first part containing thereof; (ii) cooling said first part such that the first polymer composition reaches a surface temperature (Ts1) below the crystallization temperature (Tcr1) of the first polymer; and (iii) subsequently, injection moulding the second polymer composition, i.e. the polymer composition with the higher thermal conductivity (TC2), at a temperature above the melting temperature (Tm2) of the second polymer over the first part, to form the second part and simultaneously form an interface between the second polymer composition and the first polymer composition.

3. The process according to claim 1, wherein the first part and the second part are fastened to each other through an interface with an interfacial adhesive energy being higher than either the cohesive energy of the first polymer composition or the cohesive energy of the second polymer composition, or higher than both.

4. The process according to claims 1, wherein the ratio TC2/TC1 is at least 3 and either the first polymer composition has an in-plane thermal conductivity of at most 1.25 W/m.Math.K and/or the second polymer composition has an in-plane thermal conductivity of at least 3 W/m.Math.K.

5. The process according to any one of the claims 1, wherein the first polymer and/or the second polymer comprises a semi-crystalline polyamide chosen from the group consisting of PA6, PA66, PA46 and PA46/4T, and mixtures and copolymers thereof.

6. The process according to claim 1, wherein the second polymer composition comprises a thermally conductive filler chosen from the group consisting of aluminium, alumina, copper, magnesium, brass, carbon, silicon nitride, aluminium nitride, boron nitride, graphite, ceramic fibres and mixtures thereof.

7. An assembly of parts obtained by the process according to claim 1, the assembly of parts comprising a first part containing a first polymer composition and a second part containing a second polymer composition the second part being overmoulded over the first part, the first part and the second part being fastened to each other through an interface between the first polymer composition and the second polymer composition, wherein the thermal conductivity of the second polymer composition (TC2) is higher than the thermal conductivity of the first polymer composition (TC1) with a factor TC2/TC1 of at least 1.5.

8. A lamp component comprising an assembly according to claim 1.

9. The lamp component according to claim 8, wherein the lamp component is a lamp socket or a lamp housing.

Description

EXAMPLES AND COMPARATIVE EXPERIMENTS

[0085] For the examples and comparative experiments different combinations of materials were used, selected from the materials listed below.

Materials

[0086] C-1 Unreinforced PA46 grade, TC=0.3 W/m.Math.K [0087] C-2 Glass fibre reinforced grade, PA46 based, graphite filled, TC=15 W/m.Math.K [0088] C-3 Unfilled PA6 grade, TC=0.3 W/m.Math.K [0089] C-4 Unreinforced PA6 grade, graphite filled, TC=15W/m.Math.K [0090] C-5 Unreinforced flame retardant grade, PA46 based, boron nitride filled, TC=1 W/m.Math.K [0091] C-6 Unreinforced PA46-grade, graphite filled, TC=15 W/m.Math.K [0092] C-7 Unreinforced grade, based on PA46/PA6 blend, TC=0.3 W/mK.

TABLE-US-00001 TABLE 1 Overview of Examples and Comparative Experiments representing injection moulding tests comprising combinations of different materials, their thermal conductivities, moulding temperatures and resulting adhesion energy. First Second Processing polymer polymer TC1, TC2 Temperatures Adhesive compo- compo- Ratio Tim1, Ts1, Energy .sup.b) Experiment sition sition TC2/TC1 Tim2, (J/m.sup.2) Example I C1 C2 0.3; 15; 50 315; 125; 315; 180 Example II C3 C4 0.3; 15; 50 260; 125; 290; 340 Example III C5 C2 1; 15; 15 310; 125; 310; 287 Example IV C5 C4 1; 15; 15 315; 135; 290; 304 Example V C1 C6 0.3; 15; 50 315; 125; 315; 170 Comp. Exp C1 C1 0.3; 0.3; 1 315; 135; 315;  .sup. ~0.sup.a)   A Comp. Exp C1 C1 0.3; 0.3; 1 315; 240; 315;  .sup. ~0.sup.a)   B Comp. Exp C2 C1 15; 0.3; 315; 125; 315;  .sup. ~0.sup.a)   C 0.02 Comp. Exp C2 C5 15; 1; 0.07 315; 125; 315;  8 D Comp. Exp. C1 C7 0.3; 0.3; 1 315; 125; 315;  .sup. ~0.sup.a)   E .sup.a) Too low to be measured accurately. .sup.b) In case of cohesive failure, the reported number is considered to be representative for the cohesive energy rather than the interfacial adhesive energy, the latter considered implicitly being higher than the measured value.
The Examples according to the invention all showed cohesive failure within one of the parts, thus evidencing that the interfacial adhesive energy was higher than the cohesive energy of at least one of the parts. The Comparative Experiments showed adhesive failure between the two parts, and a very low separation or delamination energy, thus evidencing that the interfacial adhesive energy was lower than the cohesive energy of each of the parts.