Raman micro-analysis could provide you the information you need. It can get molecular bonding structures versus correlated spatial structures. This means that co-polymer can be distinguished from a mixture or blend of two polymer compenents, i.s. PP and PE. It can also detect the purity of copoymers if it is generated indeed and its percentage if there is presence of low levels of each two residual PP and/or PE.

DSC shows 2 Tg for blend  of homopolymers and generally one in random copolymers.

Satisfied with Mr @Sinasafari response

Be carefull, PP-PE block copolymers are also on the market with 2 Tgs. Besides the determination of the Tgs for PP/PE blends or copolymers could be quite difficult.

You should perform SEM to observe the presence of domains (with characteristic sizes) and DMA to get precise relaxation temperature

Dear s. Pappalardo , I will borrow from the article titled "Identification of turf fibres using differential scanning calorimetry" by Dr. Konrad Binder, ÖIST, Vienna, the following clear explanation for how to understand the combine polymers if it is a blend or a copolymer by performing the DSC analysis [1]:

"Fundamentally, there are two means in which to combine polymers with one another:

1) Through mixing the two polymers:

Generally mixing two polymers produces two phases, in which one phase, composed more or less of bigger particles, is embedded into the matrix of the other. Consequently, the two polymers have considerably independent melting points, which can be easily interpreted.

2) Through copolymerization.

According to the specific type of polymerisation (which is determined by the catalyst system), we can produce different kinds of copolymers:

Random, alternating, sequential or graft copolymers. We can understand quite easily that a random copolymer, consisting of 40% ethylene and 60 % propylene monomers, for example, cannot form crystalline zones which are characteristic for PE or PP. Therefore the DSC Analysis will not show the melting peaks of PE or PP. Nevertheless, a graft polymer with a main chain (backbone) of PP and only a few short grafted PE-side chains would show the PP-Peak at around 160 °C but no PE-Peak" [1].

The Shimaduz Application News, No. T153 titled "Measuring Polyethylene (PE)-Polypropylene (PP) Blend Samples" utilizes a process to determining the component ratios of blended high molecular materials by DSC [2].

Best regards

[1] https://www.isss-sportsurfacescience.org/conferences-mallorca-1999-m01

[2] https://www.shimadzu.com/an/sites/shimadzu.com.an/files/pim/pim_document_file/applications/application_note/10829/jpc317014.pdf